Grundfos A2 Water Engineering[1]

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GRUNDFOS ENGINEERING MANUAL

GRUNDFOS ENGINEERING MANUAL

L-SP-TL-500

5/04

PRINTED IN USA

U.S.A. GRUNDFOS Pumps Corporation 17100 West 118th Terrace Olathe, Kansas 66061 Phone: (913) 227-3400 Telefax: (913) 227-3500

www.grundfos.com

Canada GRUNDFOS Canada Inc. 2941 Brighton Road Oakville, Ontario L6H 6C9 Phone: (905) 829-9533 Telefax: (905) 829-9512

Mexico Bombas GRUNDFOS de Mexico S.A. de C.V. Boulevard TLC No. 15 Parque Industrial Stiva Aeropuerto C.P. 66600 Apodaca, N.L. Mexico Phone: 011-52-81-8144 4000 Telefax: 011-52-81-8144 4010

Water Systems Engineering Manual for Groundwater Supply and Special Applications

GRUNDFOS ENGINEERING MANUAL

TABLE OF CONTENTS WATER SUPPLY PLANNING 1A 1B 1C 1D 1E

2.

PUMP HYDRAULICS & APPLICATION CONSIDERATIONS 2A 2B

2C

2D

2E 3.

Water Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Sources, Quality, Quantity & Rights Groundwater & Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8 Supply, Hydraulics, Construction & Treatment Water Quality & Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-37 Drinking Water Regulations, Characteristics & Treatment Water System Capacity Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-59 Rural, Public and Irrigation Systems, Sizing Pumping, Distribution and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-81 Hydro-Pneumatic System

Pump Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 General Centrifugal Pump Operation and Types (ie. types made by Grundfos), Submersible Overview Hydraulic Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15 Density, Specific Gravity and Weight, Pressure and Head, Flow, Vapor Pressure, NPSH, Power and Viscosity Pump Hydraulic Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24 Affinity Laws, Specific Speed, Speed - Torque, System Head Curves, Parallel and Series Flow, Minimum Flow and Thrust Pumping System Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-38 Cavitation, Entrained Gas, Entrained Solids, Water Hammer, Downhole Check Valves, Corrosion, Testing, Power Consumption and Cost Engineering Properties of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-60

ELECTRICAL – POWER, MOTORS AND CONTROL 3A 3B 3C 3D

Electrical & Power Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 AC Power, Impedance, Power Factor, Phase Converters Induction Motor Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 Voltage, Frequency, Efficiency, 3-Phase, PF, Insulation Systems Motor Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26 Full Voltage Starting, Reduced Voltage Starting Grundfos Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-32 CU3 Controller, R100 Remote, SM100 Sensor Module, G100 Gateway Communication Interface

4. SUBMERSIBLE MOTORS 4A 4B 4C 4D

Submersible Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Overview, Motor Types, Thrust Bearings, Generator Use in Submersible Application Submersible Motor Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18 Required Cooling, Motor Derating, Motor Sleeves, Special Applications Motor Insulation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24 Dielectic Absorption Ratio Submersible Power Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26 Cable Selection Introduction

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1.

GRUNDFOS ENGINEERING MANUAL

5.

GRUNDFOS SUBMERSIBLE PRODUCTS

Introduction

5A 5B

Large Submersible Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 Product Overview, Features and Benefits, Pump Models, Single Stage Data, Submersible Pump Data Exploded View Drawings and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 Pump Drawings, Materials Used in Construction

6. SUBMERSIBLE APPLICATIONS AND SIZING 6A 6B

7.

Submersible Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2 Sump Pumps, Can Pumps Sizing and Selection Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12 Calculation of Submersible Pump and Motor Size, Installation and Start-Up Rules

TECHNICAL APPENDICES AND REFERENCES 7A

7B

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Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Pipe Data, Flange Dimensions, Friction Loss, Equivalent Pipe Capacity, Pipe Flow Estimating, Conversion Tables Reference List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31

Introduction

JANUARY 1999

GRUNDFOS ENGINEERING MANUAL

Grundfos Introduction

Engineering Manual for Groundwater Supply and Special Applications INTRODUCTION FOREWORD This manual was developed to serve three (3) principal purposes: 1. To provide the water supply professional with a technical primer applicable to many of the various system considerations and issues associated with the development of a new or expansion of existing groundwater supply systems commonly encountered in the United States. 2. To provide a single source reference for commonly required information associated with the design of groundwater supply systems utilizing submersible pumping equipment and selective special applications 3. To acquaint the water supply professional with the use, application and advantages of Grundfos stainless steel submersible pump and control products. We have taken considerable time and care to make the presentation as convenient and easy to use as possible; however, we realize there is always room for improvement and invite comment. It is our sincere hope that the user finds this manual a useful reference tool in the design and construction of groundwater systems, and associated submersible pump products.

Introduction

iii

Introduction

GRUNDFOS ENGINEERING MANUAL

Technology and business development center at Group headquarters in Denmark

A global business With over 11,000 employees worldwide, and annual production of 10 million pump units per year, Grundfos is one of the world’s leading pump manufacturers. Over 60 Grundfos Companies around the globe help bring pumps to every corner of the world, supplying drinking water to Antarctic expeditions, irrigating Dutch tulips, monitoring groundwater beneath waste heaps in Germany, and air conditioning Egyptian hotels. Efficient, sustainable products Grundfos is constantly striving to make its products more user-friendly and reliable as well as energy-saving and efficient. Our pumps are equipped with ultra-modern electronics allowing output to be regulated according to current needs. This ensures convenience for the end-user, saves a great deal of energy and, in turn, benefits the environment. Research and development In order to maintain its market position, Grundfos takes customer research to heart when improving or developing

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Introduction

new products. Our Research and Development department makes use of the latest technology within the pump industry in search of new and better solutions for the design and function of our pump solutions. Corporate values The Grundfos Group is based on values such as sustainability, openness, trustworthiness, responsibility, and also on partnership with clients, suppliers and the whole of society around us, with a focus on humanity that concerns our own employees as well as the many millions who be-nefit from water that is procured, utilized and removed as wastewater with the help of Grundfos pumps.

GRUNDFOS ENGINEERING MANUAL

Introduction

IT IS OUR MISSION – the basis of our existence – to successfully develop, produce, and sell high quality pumps and pumping systems worldwide, contributing to a better quality of life and a healthier environment.

Grundfos North America

Fresno, California

Monterrey, Mexico

● ● ● ●

Olathe, Kansas

Allentown, Pennsylvania

Oakville, Canada

North American headquarters in Olathe, Kansas Manufacturing in Fresno, California Service, distribution and light assembly in Allentown, Pennsylvania Sales and assembly located in Canada and Mexico

Introduction

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GRUNDFOS ENGINEERING MANUAL

Introduction

Disclaimer Considerable effort has been expended to insure the accuracy of the information presented in this manual and to the best of our knowledge, the information contained is accurate. Grundfos, it’s dealers and distributors, and authors of and contributors to this manual assumes no liability or warranty whatsoever, expressed or implied, for the accuracy, completeness and/or reliability of such information contained herein. Final determination of the suitability of the information or products for the use contemplated is the sole responsibility of the user. We recommend that anyone intending to rely on the guidelines and recommendations mentioned in this manual satisfy themselves as to the suitability, fitness for a particular purpose and compliance to all applicable safety and public health codes before implementation. The format, presentation and a majority of the tabulated information is copyrighted by Grundfos. Manual materials may be copied for individual use only.

PRODUCT LINES Groundwater Grundfos offers a wide range of “no lead” submersible pumps for domestic groundwater system applications. Built of rugged stainless steel and superior components, Grundfos submersibles are regarded as the toughest, most reliable pumps on the market.

Commercial/Industrial Grundfos pumps provide a multitude of commercial uses, providing high capacity pumps for universities, hospitals, hotels and high-rise buildings. Grundfos is also well recognized for industrial applications including automotive plants, paper mills, food processing machinery, offshore platforms and reverse osmosis systems.

Plumbing and Heating Grundfos offers a full line of circulators for hydronic, hot water, and solar energy applications. Currently there are more than 3 million Grundfos circulators systems in use throughout the world.

Sewage, Effluent and Sump Pumps Grundfos offers a line of sewage, effluent and sump pumps for applications involving residential and light commercial sewage, septic system effluent and residential sump and waste water removal.

Environmental Grundfos Redi-Flo submersible pumps are designed for environmental groundwater monitoring, sampling and clean-up operations. Grundfos Pumps Corporation is one of the first U.S. pump manufacturers to be ISO 9001 certified for high quality standards throughout its entire product line. Advanced robotics fabrication, skilled applications engineers, CAD/CAM & Catia engineering, on-going educational training, and service and repair facilities all contribute to success at Grundfos.

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Introduction

GRUNDFOS ENGINEERING MANUAL

Grundfos Engineering Manual for Groundwater Supply and Special Applications

1A

WATER SUPPLY PLANNING FUNDAMENTALS • Water Sources . . . . . . . . . . . . . . . . . . . • Water Quality . . . . . . . . . . . . . . . . . . . • Quantity of Water . . . . . . . . . . . . . . . . • Water Rights . . . . . . . . . . . . . . . . . . . .

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1-2 1-5 1-6 1-7

1B

GROUNDWATER & WELLS • Groundwater as a Water Supply Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8 • Groundwater Hydrology & Well Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11 • Well Design & Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17 • Well Disinfection & Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-34

1C

WATER QUALITY & TREATMENT • Drinking Water Regulations . • Water Quality for Agriculture • Water Quality Characteristics . • Water Treatment . . . . . . . . .

1D

1E

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1-37 1-44 1-45 1-50

WATER SYSTEM CAPACITY REQUIREMENTS • Residential / Domestic and Farm Systems . • Public Water Systems . . . . . . . . . . . . . . . . • Agricultural and Turf Irrigation Systems . . . • Curves for Sizing Domestic Water Demand

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1-59 1-65 1-69 1-74

PUMPING, DISTRIBUTION & STORAGE • Pumping . . . . . . . . . . . . . . . . . . . • Distribution . . . . . . . . . . . . . . . . . • Storage . . . . . . . . . . . . . . . . . . . . • Hydro-Pneumatic Systems . . . . . .

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1-81 1-87 1-89 1-92

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Section 1A Water Supply Planning Fundamentals

1-1

Section 1

SECTION 1: WATER SUPPLY PLANNING

GRUNDFOS ENGINEERING MANUAL

1A WATER SUPPLY PLANNING FUNDAMENTALS Planning a water-supply system begins with the identification of available water sources. The quality of water from those sources must then be investigated, as well as the quantity of water that each source can reliably supply. Finally, before a source can be selected and developed, the legal rights to the water from that source must be established.

Section 1

Water Sources There are two principal sources suitable for use as a potable water supply; groundwater and surface water. In some instances, a water supply may use a combination of both sources. Both sources are part of, and renewed by the hydrologic cycle. Refer to Figure 1-1 for a graphical depiction of the Hydrologic Cycle. Groundwater. Groundwater supplies are important sources of water supply which have a number of advantages over surface supplies. They may require little or no treatment, have uniform temperature throughout the year, are cheaper than impounding reservoirs, and amounts of water available are more certain. They are relatively unaffected by drought in the short term. Groundwater is the portion of water that infiltrates the soil not utilized by plants (evapo-transpiration) or directly evaporated. This unused water eventually reaches the zone of saturation through the force of gravity. Water in the zone of saturation is referred to as “groundwater.” The upper surface of the zone saturation, if not confined by impermeable material, is called the water table. The saturated zone may be viewed as a huge natural reservoir whose capacity is the total volume of pores or openings in the rocks that are filled with water. Groundwater may be found in one continuous body or several separate strata. The thickness in the zone of saturation varies from a few feet to many hundreds of feet. Factors that determine its thickness are: the local geology, the availability of pores or openings in the formations. Movement of water within the zone is a result of gradient changes as a result of natural or man made recharge and discharge. Formations or strata within the saturated zone from which ground water can be obtained for beneficial use are called “aquifers.” An aquifer is a water-saturated geologic unit that will yield water to wells or springs at a sufficient rate as to be a practical sources of water supply. Sand, gravel and sandstone aquifers provide the best aquifer media for high capacity water well construction. Types of Wells. In the ordinary or water-table well the water rises to the height of the saturated material surrounding it. There is no pressure other than atmospheric upon the water in the surrounding aquifer. An artesian well is one in which the water rises above the level at which it is encountered in the aquifer because of pressure in the confined water of the aquifer. A flowing well is an artesian well where the pressure raises the water above the casing head. Heavy draft upon the aquifer may so lower the hydraulic gradient that a flowing well will cease to flow. Figure 1-2 illustrates artesian conditions. Pumping will cause a lowering of the water table near the well. If pumping continues at a rate that exceeds the rate of ground water recharge, a condition known as ground water mining occurs. Prolonged groundwater mining will increase pumping cost as the water level drops, change quality and can promote salt-water encroachment in coastal areas. Springs: An opening in the ground surface form which ground water flows is a spring. Water may flow by force of gravity (from water-table aquifers) or be forced out by artesian pressure. Springs constitute only a very small portion of groundwater supply sources. Surface Water. Precipitation that does not enter the ground through infiltration or is not returned to the atmosphere by evaporation, flows over the ground surface and is classified as direct runoff. Direct runoff is water that moves over saturated or impermeable surfaces into stream channels, lakes or artificial storage sites. The dry-weather (base) flow is derived from groundwater or snowmelt. Runoff from ground surfaces may be collected in either natural or artificial reservoirs. A portion of the water stored in surface reservoirs is lost by evaporation and by infiltration to the groundwater.

1-2

Section 1A Water Supply Planning Fundamentals

GRUNDFOS ENGINEERING MANUAL

Figure 1-1: Schematic Diagram of the Hydrologic Cycle

Section 1

Figure 1-2: Subsurface and ground water phase of the hydrologic cycle

Section 1A Water Supply Planning Fundamentals

1-3

GRUNDFOS ENGINEERING MANUAL

Potable Water Available in the United States. It is estimated that the earth contains 380 million cubic miles of water. About 2.5% of this is fresh water and of this, 1.5 % is in the form of ice at the polar caps. Slightly less than 1% of all water therefore remains available to man for potable use. One percent sounds like a small amount, however, it represents a tremendous quantity, far outranking all other natural resources.

Section 1

Water is not used up like other resources. By virtue of the hydrological cycle it is continually returned to its source. It has been estimated that ground waters in the United States have been depleted less than 1/4% of 1% in 500 years. Of all usable water available on earth, approximately 26% exists in the United States, 77% of which is contained in underground aquifers, 23% as surface water (21% in lakes and 2% in rivers and reservoirs). Approximately 47% of the water presently used in the United States comes from surface water. The remaining 53% is taken from groundwater sources (source: USGS 1986 National Water Summary). The major groundwater regions of the continental United Sates are shown in Figure 1-3. Figure 1-3: Groundwater Availability and Regions in the U.S.

Fresh Water Availability in the U.S

Groundwater vs. Surface Water in the U.S.

Groundwater 77%

Groundwater 53%

Lakes 21% Surface Water 47%

Reservoirs Rivers

Major Groundwater Regions of the Continental U.S.

1-4

Section 1A Water Supply Planning Fundamentals

GRUNDFOS ENGINEERING MANUAL

Water Quality Precipitation in the form of rain, snow, hail or sleet contains very few impurities and virtually no bacteria. It may contain trace amounts of minerals, gases, and other substances as it forms and falls through the earth’s atmosphere. Once precipitation reaches the earth’s surface, however, mineral and organic substances, microorganisms, and other forms of pollution (which tend to lower water quality) enter the water.

The widespread use of synthetically produced chemical compounds; including pesticides, insecticides and solvents, has had a pronounced effect on water quality. Many of these materials are known to be toxic. Others have certain undesirable characteristics, which interfere with water use even when these materials are present in relatively small concentrations. The Safe Drinking Water Act. When selecting a source as a water-supply for potable purposes, it is necessary to carefully examine all water-quality factors that might adversely affect the intended use of the water source. As a minimum, the quality of the water must be such that it will meet (after treatment, if necessary) the standards established under the drinking water regulations of the Federal Safe Drinking Water Act (SDWA), as well as any additional state or local standards. When selecting a water source it is also important to consider other characteristics, including the water’s palatability, its aesthetic quality and its potential for corrosion or scaling of pipes. A detailed discussion of the SDWA and associated water quality issues are presented in Section 1C. Treatment. In evaluating a source based on water quality, the availability and costs of water-treatment techniques to remove undesirable constituents must be considered. Conventional water treatment techniques; such as aeration, sedimentation, coagulation/flocculation, filtration, softening, fluoridation, adsorption and disinfection have been used for decades to produce potable water for large municipal water systems. The same techniques can be used to produce water of potable quality for smaller systems. In addition, small package treatment units using membrane separation processes, primarily reverse-osmosis (RO), are commercially available. These units, although often uneconomical for large utilities, may be a viable alternative for a small system, especially for use with brackish ground water sources. Water quality characteristics can be broken into four categories; physical, chemical, biological and radiological. Some of the treatment methods that a small utility might economically use to reduce objectionable contaminants to an acceptable level are discussed in Section 1C. Sanitary Survey. A sanitary survey is important in the development of a new water supply and is often a regulatory requirement for permit. The sanitary survey should be made in conjunction with the collection of initial engineering data covering the development of a given source and its capacity to meet existing and future needs. The sanitary survey should include the detection of all health hazards and the assessment of there present and future importance. Only persons trained and competent in public health and familiar with water supply engineering should conduct the sanitary survey. In the case of an existing supply, the survey should be made at a frequency compatible with the control of the health hazards and the maintenance of good sanitary quality, or as required by the governing regulatory agency. A general outline of the issues/ factors that should be investigated or considered in a ground water sanitary survey is listed as follows: A. Character of local geology and slope of ground surface. B. Nature of soil and underlying porous strata - whether clay, sand, gravel, rock (especially porous limestone); coarseness of sand or gravel; thickness of water-bearing stratum, depth to water table; location, log and construction details of local wells in use and abandoned.

Section 1A Water Supply Planning Fundamentals

1-5

Section 1

When water runs over or through the ground surface, it may pick up soil particles. This is noticeable in the water as cloudiness, or “turbidity.” Water also picks up particles of organic matter and bacteria. As surface water seeps into the soil and through the underlying material to the water table, most suspended particles are filtered out. This natural filtration is partially effective in removing bacteria and other particulate materials; however, the chemical characteristics of the water may change and vary widely when it comes in contact with mineral deposits in the soil.

GRUNDFOS ENGINEERING MANUAL

C. Slope (gradient) of water table. D. Extent of drainage area likely to contribute water to the supply. E. Nature, distance and direction of local pollution sources. F. Possibility of surface-drainage water entering the supply and of wells becoming flooded, methods of protection.

Section 1

G. Methods used for protecting the supply of pollution by means of sewage treatment, waste disposal, etc. H. Water quality data collected from test wells or permanently constructed monitoring wells constructed in advance of production wells. I. Well construction: 1. Total depth of well.. 2. Casing - diameter, wall thickness, material and length from surface. 3. Screen or perforations - diameter, material, construction, locations and lengths. 4. Formation seal - material (cement, sand, bentonite, etc.), depth intervals, annular thickness and method of placement. J. Protection of well head - presence of sanitary well seal, casing height above ground, floor or flood level, protection of well vent, protection of well from erosion and animals. K. Pumphouse construction (floors, drains, etc.), capacity of pumps, drawdown when pumps are in operation. L. Availability of an unsafe supply, usable in place of normal supply, hence involving danger to the public health. M. Disinfection - equipment, supervision, test kits or other types of laboratory control.. Note: Not all the items listed are pertinent to any one supply.

Quantity of Water An important step in selecting a suitable water-supply source is determining the demand that will be placed on it. The four principal issues that must be addressed in conjunction with determining system water quantity needs are usage, flow, pressure and storage. Usage (consumption). The quantity of water must be established to determine the adequacy of the source to meet demand; as well as establishing infrastructure requirements. The quantity of water required to be supplied by a system is most easily calculated when the ultimate or end use is known. Quantity requirements are normally estimated based on average daily usage (consumption) and is expressed in gallons per day (gpd) or gallons per capita per day (gpcd) depending on the size of the system. Metering can significantly reduce consumption within a system. Surveys of public water systems, which have went from a flat rate charge to individually metered services, have reduced system wide consumption by as much as 50%. The usage rate generally will increase slightly with time after meters have been installed. Flow. Flow requirements must be determined to insure the adequacy of the system to deliver the required amount of water on demand. The first step in calculating flow requirement is to estimate the average daily consumption, which is discussed above under the heading of “Usage”. The average daily consumption can then be translated to a average instantaneous daily flow value, most often referred to as average demand or average flow, usually expressed in gallons per minute (gpm). The peak demand rate (peak flow) can then be estimated by multiplying the average flow by the appropriate correction factors. The peak flow requirements can be ten times greater than the average daily flow. Knowledge of the average and peak flow requirements in a system is critical for developing system infrastructure such as; pipe lines, pumping equipment, buffer storage, treatment, etc. 1-6

Section 1A Water Supply Planning Fundamentals

GRUNDFOS ENGINEERING MANUAL

Pressure. For ordinary service, the typical delivery pressure ranges from 20 to 40 psi. The discharge pressure at the well head (discharge of the pump) is often 10 to 20 psi greater than system pressure to over come friction losses within the system. Optimum system pressure requirements are a function of topography, fire protection needs, building height, etc. The availability of water under pressure stimulates its use. Increasing pressure from 25 psi to 45 psi can encourage a increase water use of up to 30%. Storage. Storage is required to equalize pumping rates over the day, to equalize supply and demand over a long period of high consumption, and to furnish water for such emergency and seasonal usage such as fire fighting and landscape irrigation.

Water Usage in the United States. On average, the United States uses 80 to 100 gallons of drinking water per person per day. Of the “drinking water” supplied by public water systems, only a small portion is actually used for drinking. A majority of residential water consumers use water for such purposes as: sanitation, cooking, cleaning and landscape irrigation. The typical daily residential water use profile is described as follows: • • • •

Lowest rate of use - 11:30 p.m. to 5:00 a.m. Sharp rise/high use - 5:00 a.m. to noon. (Peak hourly use from 7:00 a.m. to 8:00 a.m.) Moderate use - noon to 5:00 p.m. (Lull around 3:00 p.m.) Increasing evening use - 5:00 p.m. to 11:00 p.m. (Second minor peak from 6:00 p.m. to 8:00 p.m.)

A typical family of four on a public water supply uses about 350 gpd. In contrast, a typical household that gets its water from a private well or cistern uses about 200 gpd for a family of four. The commonly accepted value for individual water usage for rural/domestic populations is 100 gpd per person. Public water systems typically used a design values ranging from 125 to 175 gpd per person (175 gpd avg.) Major factors which affect consumption are metering, climate and delivery pressure. Commercial and industrial businesses may also place heavy demands on public water supplies. In most water supply systems, the predominant number of user connections are residences, but the few connections to nonresidential customers may account for a significant portion of the system-wide water use. Of the total annual U.S. water use; it is estimated 10% is consumed by residential use, with the remainder being consumed by Industry and Agriculture.

Rights to the Use of Water The right to use surface or groundwater for domestic use, irrigation, or other purposes varies between states. Some water rights stem from ownership of the land bordering or overlying the source, while others are acquired by a performance of certain acts required by law. The three basic types of water rights are: • Riparian - Rights that are acquired together with title to the land bordering or overlying the water source. • Appropriative - Rights that are acquired by following a specific legal procedure, usually involving diverting unclaimed water and putting it to use. • Prescriptive - Rights that are acquired by diverting and putting to use, for a period, and under the conditions specified by statute, water to which other parties may or may not have prior claims. When there is any question regarding the right to the use of water, the utility owner should consult the appropriate state authority and clearly establish the rights to its use.

Section 1A Water Supply Planning Fundamentals

1-7

Section 1

The issues discussed above under the general heading of “Quantity of Water” are most applicable to public water systems. Technical issues associated with estimating usage, flow, pressure and storage requirements for several of the most common water system categories are detailed in Section 1D “Water System Capacity Requirements”. Special considerations, such as landscape irrigation and fire protection are addressed within the context of each water system category (system type) presented in Section 1D.

GRUNDFOS ENGINEERING MANUAL

1B GROUNDWATER & WELLS Groundwater as a Water-Supply Source Rock Types and Geology. About 98% of the earth’s crust is composed of 8 chemical elements. Two of the eight elements, oxygen and silicon (silica Si 02), compose 75% of the crust. Most of the elements of the earth’s crust have combined with one or more other elements form compounds called minerals. The minerals generally exist in mixtures to form rocks.

Section 1

The rocks that form the earth’s crust are divided into three classes: 1. Igneous. Rocks that are derived from magma deep in the earth. They include granite and other coarsely crystalline rocks, dense igneous rocks such as basalt and other lava rocks occur in dikes and sills. 2. Sedimentary. Rocks that consist of chemical precipitates and rock fragments deposited by water, ice, or wind. These include deposits of gravel, sand, silt, clay, and the hardened derivatives of these-conglomerates, sandstone, siltstone, shale, limestone, gypsum and salt. 3. Metamorphic. Rocks that are derived from both igneous and sedimentary rocks through considerable alternation by heat and pressure at great depths. These include gneiss. schist, quartzite, slate, and marble. The pores, joints, and crevices of the rocks in the zone of saturation are generally filled with water. Although the openings in these rocks are usually small, the total amount of water that can be stored in the subsurface reservoirs of the rock formations is large. The most productive aquifers are deposits of clean, coarse sand and gravel; coarse, porous sand stone; cavernous limestone; and broken lava rock. Some limestone, however, is very dense and unproductive. Most of the igneous and metamorphic rocks are hard, dense, and of low permeability, and generally yield small quantities of water. Among the most unproductive formations are the silts and clays. The openings in these materials are too small to yield water, and the formations are structurally too weak to maintain large openings under pressure. Compact materials near the surface, with open joints similar to crevices in rock, may yield small amounts of water. Formation and deposition of the various rock types can be further classified in terms of geologic time period. The time period in which the various formation deposits were made often identify the characteristic of the groundwater (Aquifer) system. Generally, younger rocks are better aquifer’s than older materials. Groundwater and Quality. Water movement within a ground water basin is caused by gradient changes. Gradient changes are primarily a result of recharge (inflow), stemming from precipitation infiltration and discharge (outflow) as a result of pumping. The quantity of water that can be removed from a ground water basin, without depleting storage, is referred to as the basin yield. Proper development of a groundwater source requires careful consideration of the hydrological and geological conditions of the area. Information about the geology and hydrology of an area may be available in publication of the US Geological Survey or from other federal and state agencies. The National Water Well Association may also offer assistance. Sanitary Quality of Groundwater: When water seeps through overlying material to the water table, particles in suspension, including microrganisms, may be removed. The extent of removal depends on the thickness and character of the overlying material. Clay or hardpan provides the most effective natural filtration of ground water. Silt and sand also provide good filtration if it is fine enough and in thick enough layers. The bacterial quality of the water also improves during storage in the aquifer because storage conditions are usually unfavorable for bacterial survival. Groundwater found in unconsolidated formations (sand, clay, and gravel) and protected by similar materials from pollution sources is more likely to be safer than water coming from consolidated formations (limestone, fractured rock, lava, etc.).

1-8

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

In areas where human waste are deposited in septic tanks, cesspools, or pit privies, the bacteria in the liquid effluents from such installations may enter shallow aquifers. Sewage effluents have been known to enter directly into water-bearing formations by way of abandoned wells or soil-absorption systems. In such areas, the threat of contamination may be reduced by proper well construction-locating the well father from the source of contamination. The direction of groundwater flow usually approximates that of surface flow, and it is always desirable to locate a well so that the normal movement of ground water flow carries the contaminate away from the well.

Some substances found naturally in groundwater, while not necessarily harmful, may cause a disagreeable taste or undesirable properties to the water. Magnesium sulfate (Epsom salt), sodium sulfate (Glauber’s salt), and sodium chloride (common table salt) are a few of these. Iron and manganese are commonly found in groundwater. Regular users of water containing relatively high concentrations of these substances commonly become accustomed to the water and consider it good tasting. Concentrations of chlorides and nitrates that are unusually high generally indicate sewage pollution. Temperature. The temperature of groundwater remains nearly constant throughout the year. Water from very shallow sources (less than 50 ft [15m] deep) may vary in temperature from one season to another, but water from deeper zones remain relatively constant – about the same as the average annual surface air temperature. Beyond about 100 ft (30 m), the temperature of ground water increases steadily at the rate of about 1°F (5/9°C) for each 100 ft. (30m) of depth. In volcanic regions, this rate of increase may be much greater. Figure 1-4: Typical Groundwater Temperature in the U.S @ 100’ Depth

Section 1B Groundwater & Wells

1-9

Section 1

Chemical and Physical Quality of Groundwater. The mineral content of groundwater reflects the type of formation which it moves through. Generally, groundwater in arid regions is harder and more mineralized than water in regions of high annual rainfall. Deeper aquifers are more likely to contain higher concentrations of minerals in solution because the water has had more time to dissolve the mineral rocks. For any groundwater region there is a depth below which salty water, or brine, is almost certain to be found. This depth varies from one region to another.

GRUNDFOS ENGINEERING MANUAL

Distances to Sources of Contamination. All groundwater sources should be located a safe distance from sources of contamination. In cases where sources are severely limited, groundwater that might become contaminated may be considered for a water supply if treatment is provided. All water sources should be placed a safe distance from potential contamination with consideration to the direction of water movement. A determination of a safe distance should be based on specific local factors and addressed in the “Sanitary Survey” phase. Table 1-1 is a guide for determining safe distances.

Section 1

Table 1-1: Guide for Determining Location of Water Source From Contamination Source

Formation Favorable (unconsolidated) Unknown Poor (consolidated)

Minimum Acceptable distance from Well to Source of Contamination 50 ft (15 m). Lesser distances only with health department approval following comprehensive sanitary survey of proposed site and immediate surroundings. 50 ft (15 m) only after comprehensive geological survey of the site and its surroundings has established, to the satisfaction of the health agency, that favorable formations do exist. Safe distances can be established only following both the comprehensive geological and comprehensive sanitary surveys. These surveys also permit determining the direction in which a well may be located with respect to sources of contamination. In no case should the acceptable distance be less than 50 ft (15 m)

Development of a Groundwater Supply. The type of groundwater development to be undertaken depends on the geological formations and hydrological characteristics of the water-bearing formation. Development of ground water falls into two main categories: 1. Development by wells a. Nonartesian or water table b. Artesian

2. Development from springs a. Gravity b. Artesian

Note: Development of springs is outside the scope of this manual. Nonartesian wells penetrate formations in which groundwater is found under water table conditions. Pumping from the well withdrawls water, lowering the water table in the vicinity of the well, as a result of the artificially created pressure differences. Artesian wells penetrate aquifers in which the ground water is found under hydrostatic pressure. Such a condition occurs in an aquifer that is confined beneath an impermeable layer of material at an elevation lower than that of the intake area of the aquifer. When the water level in the well stands above the top of the aquifer, the well is described as artesian. A well that yields water by artesian pressure at the ground surface is a flowing artesian well. Preparation of Ground Surface at Well Site. A properly constructed well should prevent surface water from entering a ground water source to the same degree as does the undisturbed overlying geologic formation. The top of the well must be constructed so that no foreign matter or surface water can enter. The well site should be properly drained and adequately protected against erosion, flooding, damage and contamination. Surface drainage should be diverted away from the well. Well Yields. The amount of water that can be pumped from any well depends on the character of the aquifer and the construction of the well. In general, doubling the diameter of a well increases its yield only about 10 percent. The casing diameter is generally selected to provide enough room for proper installation of the pump. A more effective way of increasing well capacity is by drilling deeper into the aquifer. Consideration of the inlet portion of the well structure (screen, perforations, slots) is also important in determining the yield of a well in a sand or gravel formation. The amount of open area in the screened or perforated portion exposed to the aquifer is critical. Wells completed in consolidated formations are usually of open-hole construction.

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

It is rarely possible to accurately predict the yield of a well before it is completed. Knowledge can be gained from studying the geology of the area and results obtained from other wells constructed in the vicinity. This information is helpful in selecting the location and type of well most likely to be successful. The information can also provide an indication of the yield to expect. A common way to describe the yield of a well is to express its discharge capacity in relation to its drawdown. This relationship is called the “specific capacity of the well” and is expressed in gallons per minute per foot of drawdown. The specific capacity may range from less than 1 gpm/ft of drawdown for a low yield well to several 100 gpm/ft for high yield wells.

Porosity. Not all of the water contained in unconsolidated sand and gravel aquifers (water-bearing formation) can be used. The amount of water which can be taken out of an aquifer depends upon the porosity of this waterbearing formation. Porosity is a term describing the amount of open space between sand grains in an underground aquifer (Figure 1-5 diagram A). The term “absolute porosity” is the total amount of water that can be held in a given volume of the aquifer. Of the total amount of water held in an aquifer, only a portion of it is “free water” available for use. It is this free water which can be used promptly, that determines the useable porosity of the formation. The useable “bound water” is trapped (held) in the form of a thin film wetting the sides of the particles of sand (Figure 1-5 - diagram B). The more uniform the grains of sand are in size, the higher the porosity and yield from a well. A fine uniform sand will often produce more water than a coarse, mixed sand and gravel. Figure 1-5: Porosity of a Water - Bearing Formation

Permeability and Transmissibility. The terms permeability and transmissibility are used to describe the ability of an aquifer (or water bearing fomation) to allow water to pass through it. The drawing in Figure 1-6 shows a sand and gravel water bearing formation and the arrows indicate the water flow. Permeability is a measure of the flow of water, in gallons per day, which will take place across opposite faces of a one foot cube (P) under a differential head of one foot of water. Transmissibility is the average permeability of a section (T) of the entire aquifer at a given location multiplied by the thickness of the aquifer.

Figure 1-6: Permeability and Transmissibility Illustration

Section 1B Groundwater & Wells

1-11

Section 1

Groundwater Hydrology and Well Hydraulics

GRUNDFOS ENGINEERING MANUAL

Cone of Depression. When a well is pumped, the water level in the well falls below the water level out in the aquifer, creating a gradient which immediately creates a flow into the well from all directions. As a result, the free water surface in the aquifer takes the shape of an inverted cone or curved funnel. This cone is appropriately called the “cone of depression”.

Section 1

If the material of the aquifer transmits water easily, the cone is flat and wide spread. If it transmits poorly, the cone will be steep. The cone does not have a fixed shape and becomes deeper and flatter as the well is pumped. The science of aquifer hydraulics has been built around the shape and behavior of this cone. Cone of depression issues are graphically illustrated in Figure 1-13 - diagram A & B. Seasonal Water Level Changes. A hydrograph is a record of water levels over a period of time. To obtain a hydrograph on ground water, a recorder is installed in an observation well which is not directly affected by pumping. The water level in the observation well fluctuates with the seasons of the year. Water levels will be fairly constant during the winter months and a sharp rise in the water level is generally noted in the spring season, followed by a slow decline through summer and fall. The range of seasonal variations may be as great as five to ten feet and has a marked effect on the yield in shallow wells. Hydrographs on artesian wells show interesting effects. Changes in barometric pressure may cause a foot or more change in water level. Earthquake tremors temporarily affect levels and can be detected by sensitive hydrograph instrumentation. Pumping data obtained during the spring should be adjusted to allow for the normal decline in water levels typically observed in the fall. The collection of such hydrographic data on local ground and surface water sources is often available form the Federal and State Geological Surveys. Figure 1-7: Seasonal Water Level Changes

Well Efficiency and Overpumping. The concept of pumped well efficiency was first presented by Jacob in 1947. Basically, “well efficiency” is defined as the formation loss (the head loss required to produce flow) divided by the total drawdown observed in the well. This quotient is expressed as a percentage and is typically calculated based on data compiled from a step - drawdown pump test. Figure 1-8 represents a simplified sketch illustrating the well efficiency concept. Since groundwater flow through porous medial is laminar in nature, the head loss required to produce the flow through the aquifer is directly proportional (linear) to the well discharge.

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Construction and maintenance parameters to be considered in order to maximize well efficiency are: 1. Well screen aperture size (as large as possible consistent with gravel pack formation material retention).

Figure 1-8: Well and Formation Loss in a Pumped Well

Flow

3. Well development (well development should be conducted immediately after completion and should be continued until there is no change in specific capacity/well yield).

Formation Loss Pumping Water Level Well Loss

4. In areas where wells are subject to plugging, as a result of incrustation and/or fouling, chemical treatment should be performed periodically to maintain acceptable well performance.

In general, open hole completions in consolidated formations are more efficient than screened completions in unconsolidated formations assuming complete development. High efficiency does not insure higher specific capacity, as wells completed in unconsolidated formation usually have a higher specific capacity than consolidated formations. Overpumping (pumping the well in excess of the design rate) will result in decreased well efficiency. Adverse affects associated with overpumping are: • Increased risk of dry run (pump-off) and/or cascading water which may damage pumping equipment. • Increased risk of developing a sand problem, which can damage the well and pump. • Decrease in water quality as a result of adverse gradient changes (salt water intrusion, pull in of pollutants, silt fouling, etc.) • Increase incrustation potential. Deep drawdown increases oxygen exposure (oxidation) and can lead to plugging of both the well and pump. Incrustation is a function of the presence of detrimental micro-organisms and specific water quality conditions. Figure 1-9: Overpumping Illustration 55

Static Water Level Acceptable Gradient (ft/gpm) Increasing Gradient

40

10 Acceptable Well Load

Formation Loss

Careful analysis of pump test data should be made to insure pumping equipment is sized properly to avoid overpumping. Pumping to storage over a longer period of time and/or the construction of multiple wells to provide the required system demand can be used to reduce over pumping.

Overpumping 0

100

200

300

400

500

600

700

800

900

1000 gpm

Section 1B Groundwater & Wells

1-13

Section 1

2. Screen entrance velocity (3.5 fps or less, assuming at the design flow rate- 50% plugging of the available screen open area effective area of opening).

Static Water Level

GRUNDFOS ENGINEERING MANUAL

Well Spacing and Interference. The location of water wells in relation to one another becomes critical where:

Section 1

1. 2. 3. 4.

The land is limited for large spacing between wells. There is a high concentration of wells in the immediate vicinity. A high yield well field is planned. The aquifer has a low permeability and/or nearby boundaries, or when recharge is at great distance.

When determining well spacing requirements, it is necessary to have some idea of the shape and extent of the “cone of influence”. The cone of influence is defined as the slope of the hydraulic gradient or water surface away from a pumping well. Figure 1-13 diagram C illustrates “cone of influence” affect relative to well spacing. By determining the “cone of influence” of adjacent wells the effect of the overlapping curves can be determined, and a decision made to allow a large overlap or keep the overlap small. The cone of influence is normally determined by an aquifer pumping test. This involves measuring flows and draw- downs in the pumping well and observation wells located a distance away from the pumping well. In some highly permeable formations, wells of 2000 gpm capacity could be spaced 200’ apart, as opposed to a low permeability formation 50 gpm wells might be spaced up to 1000’ apart. Groundwater Mining. Excessive pumping of an aquifer or water-bearing formation is called “groundwater mining”. Groundwater mining occurs when the quantity of water annually pumped out of a given aquifer exceeds the quantity recharged into the aquifer. Prolong groundwater mining will result in a declining water tables and can create serious long term water supply problems, as well as increasing the cost of pumping. In certain areas, surface subsidence can occur as the water bearing formation is de-watered. The overproduction (overdraft pumping) from a well can only be maintained until the water in storage has been “mined out”. Pumping level on the well will continue to fall until it reaches the bottom of the well, at which time production cannot exceed the natural recharge rate. Overpumping and overdraft pumping are not directly relate; overpumping applies to exceeding the well design capacity, where as overdraft pumping refers to the long term depletion of aquifer storage. A remedy for groundwater mining is to space wells further apart to capture only the groundwater which is escaping from various water supply sources such as rivers, streams and lakes. In some areas, the deficiency is being made up by artificial recharge from surface water sources, as they become available. In arid regions such as the southwestern states, where pumpage far exceeds available recharge, there is no easy solution short of reduced pumping from the aquifer. Figure 1-10: Ground Water Mining Flow Clay (Water Level) 1970 1980 1990

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Artificial Recharge. When the groundwater level in an area drops at an excessive rate, it is a sign that groundwater mining is occurring. In some cases it is possible to make up this shortage with surface water. If the aquifer is shallow, it may be possible to artificially recharge the aquifer by ponding or shallow recharge pits. If the aquifer is relatively deep and confined between with impervious materials, recharge wells may be required. Artificial recharge is commonly practiced in many arid regions. Increased usage of this practice is recommended in areas where the groundwater supply is being depleted. Successful use of this method requires a careful study and analysis. Figure 1-11: Artificial Recharge

Section 1

Surface Water

Well Water Supply

Recharge Ponding

Clay

Well Sand & Gravel

Dewatering. A dewatering system is typically used to lower (depress) water levels for the purposes of construction of sub surface structures, changing aquifer flow gradient for the purposes pollutant recovery and to counter buoyancy forces which can dislodge (float out) underground structures subjected to high water table. Shallow Dewatering for construction purposes is typically accomplished through the insertion of 2” diameter well points at depths and spacings ranging from 10’ - 25’ and 20’ - 25’ respectively. The well points are typically plumbed into a central collection header system, using a single large pump equipped with a auxiliary vacuum pump, to “dewater” each well through a riser pipe by suction lift. Deep Dewatering (25’ and greater), generally require the use of individual pumps which must be controlled based on water level within the well. Submersible pumps are typically used for this purposes, as they are ideally suited as a result of there compact design and high capacity. Control (water level maintenance) is accomplished using a variety of methods ranging from throttling valves, to on - off controls, to direct acting variable speed control or a combination of one or more of these techniques. Figure 1-12: Typical Shallow Well Dewatering System

Note: Mutual interference between 2 or more wells depresses the water table for dewatering operations.

Section 1B Groundwater & Wells

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GRUNDFOS ENGINEERING MANUAL

Section 1

Water Well Hydraulics. When a well is pumped, the level of the water table in the vicinity of the well will be lowered (Figure 1-13 A). This lowering, or drawdown, causes the water level to take the shape of an inverted cone called a cone of depression. This cone, with the well at the apex, is measured in terms of the difference between the static water level and the pumping level. At increasing distances from the well, drawdown decreases until the slope of the cone merges with the static water table. The distance from this point to the well is called the radius of influence. The character of the aquifer-artesian or water table-and the physical characteristics of the formation that affect the shape of the cone include thickness, lateral extent, size and grading of sand or gravel. The radius of influence is not constant and continuously expands with continued pumping. At a given pumping rate, the shape of the cone of depression depends on the characteristics of the water-bearing formation. Shallow wide cones will form in highly permeable aquifers composed of coarse sand or gravel. Steep and narrow cones will form in less permeable aquifer. As the pumping rate increases, the drawdown increases and consequently the slope of the cone steepens. In a material of low permeability such as fine sand or sandy clay, the drawdown will be greater and the radius of influence less than for the same pumpage from very coarse gravel (Figure 1-13). When the cones of depression overlap, the local water table will be lowered (Figure 1-13). An increase in pumping lifts is required to obtain water from the interior portion of the group of wells. Wider distribution of wells over the groundwater basin will reduce the cost of pumping and allow the development of more water. Figure 1-13: Pumping Effects on Aquifers Discharge Ground Surface

A. Effect of Pumping on Cone of Depression

Static Water Table

Cone of Depression for Draw-Down Lesser Pumping Rate

Cone of Depression for Greater Pumping Rate

Radius of Influence

Discharge

Discharge Ground Surface

B. Effect of Aquifer Material on Cone of Depression

Ground Surface

Static Water Table

Static Water Table Draw-Down

Cone of Depression Draw-Down

Cone of Depression Radius of Influence

Radius of Influence Fine Sand

A

C. Effect of Overlapping Field of Influence Pumped Wells

Discharge Static Water Table mping well A created by pu

e C on by pumping wells A an e created dB n o C

Aquifer

1-16

Section 1B Groundwater & Wells

Coarse Gravel

B

Discharge

GRUNDFOS ENGINEERING MANUAL

Well Design & Construction Well Specifications. High capacity water wells are usually constructed by contract, so it is advisable that careful specifications be written to insure a satisfactory well. Before specifications are written there should be considerable investigation made by the system operator or owner. Some estimates and investigation should be made of the well size and capacity by way of the methods outlined in this manual.

1. Design Targets. An estimate of the anticipated well capacity in gpm, depth and diameter must be established in order to develop preliminary well design parameters, select drilling equipment and infrastructure planning. 2. Construction Method. The drilling and completion method should be specified based on the type of water bearing formation in which the well completion is to be made. 3. Casing. The type, weight, material, diameter and wall thickness of the casing should be specified, as well as accessory item requirements. 4. Screen. The screen type, diameter, wall thickness, aperture size, etc. Note: Screen selection and installation intervals are normally based on geophysical investigative work performed in conjunction with test hole work, 5. Gravel Pack. Gradation and installation interval to be specified when applicable. 6. Annular Seals. Grout/cement mix and application interval to be specified. 7. Development & Testing. Development and testing criteria should be clearly specified. In general, development should be continued until no increase in well specific capacity (yield) is noted and the sand specification is met. Pump performance testing should be conducted for 8-72 hours (minimum of 8 hours) after development. 8. Sand Content. A typical sand specification for a new water well is: “sand content not to exceed 5 ppm (mg/ l), 15 minutes after the start of pumping”. A properly designed and developed well should easily maintain the sand content level substantially below 1 ppm. 9. Alignment. In general, the well should not vary from the vertical (drift) in excess of 3” per 100’ of casing length (ie. 6” @ 200’ is permissible). Proper alignment of the well should be guaranteed and a test of alignment required. 10. Sanitary. Sanitary requirements should be recognized by closing the top of the well so that no surface water can enter. The casing of the well should extend at least 6” (150 mm) and preferably 12” (300 mm) above the finished grade. In areas subject to flooding, the well casing should extent 24” (600 mm) above the 100 year flood level. The well should be cleaned of all debris, lubricants and mud. Disinfection of the well must be performed. All documents and records to be maintained, and submitted by the contractor should be clearly specified in the contract documents (logs, casing and screen materials, aperture size, gravel analysis, etc.). Reliable local contractors and consultants can provide valuable advice and design assistance in the development of a water well supply source. The American Water Well Association (AWWA) standard A100-84 for water wells, contains sample contract language and various design aids.

Section 1B Groundwater & Wells

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Section 1

The drilling of a test hole as part of the geophysical investigation process is recommended in order to specify in advance the well completion requirements (casing, screen, gravel pack, etc.). In areas where high capacity water well completions are not always assured, a test well may be necessary – in addition to a test hole – to properly assess the suitability of the well location. A sanitary survey investigation as described in Section 1C should be conducted in conjunction with the initial investigation. The contract technical specification for a production water well should address the following issues.

GRUNDFOS ENGINEERING MANUAL

Types of Wells. Wells are constructed using a variety of methods such as; dug, bored, driven, jetted or drilled. Table 1-2 summarizes the suitability of the various well construction methods for a specific application and geologic formation. High capacity water wells are typically drilled using either the percussion (cable tool) or rotary (direct or reverse) drilling technique and/or combination of both.

Section 1

High Capacity Water Well Drilling Methods. As previously mentioned, the two most common methods of drilling high capacity water wells are the cable tool and rotary drilling techniques. These techniques, as they relate to drilling and completion (casing and screen) are presented below. Cable Tool. In the cable tool (percussion) drilling method, the borehole is drilled by the pulverizing action of a reciprocating steel bit suspended from the drilling rig by a wire cable. As the bit strikes the bottom of the hole, the formation is crushed, creating cuttings which are removed by balling. If the formation is loose and unconsolidated, the casing must be forced into the hole periodically to prevent caving. Several procedures are available for completing wells drilled by the cable tool method. If casing is installed as the hole is drilled, it may be perforated by down-the-hole tools, forming a screen opposite the waterproducing formations. With most methods of down-the-hole perforating, a small aperture cannot be formed nor can the aperture size be precisely controlled. Consequently, finer-grained aquifers must be avoided. In general practice, the cable tool method lends itself more to drilling coarser, harder formations. Cable tool well diameters and depths range from 8” to 18” and 100’ to 1000’ respectively. Small diameter wells for domestic purposes, drilled in tight - consolidated formations, can be constructed using the cable tools or down-the-hole air hammers. These wells often only need a surface conductor casing installed through the unconsolidated over-burden. Water is produced from the open hole. In some cases, a protective casing is installed to the depth of the pump. Rotary. The use of the direct rotary and reverse circulation rotary drilling methods are the dominate method of construction of higher capacity production water wells. Both rotary methods can be used to construct gravel envelope wells in unconsolidated formations. Typical rotary drilled well completions in unconsolidated and consolidated formations are illustrated in Figure 1-14. Direct Rotary. In the direct rotary method, a rotating bit under controlled loading is applied to the formation. Drilling fluid (water with additives-mud, is used to provide weight and viscosity) is pumped down the drill pipe, through the bit, and circulates up the hole carrying the cuttings, which are separated and removed at the surface. Usually the finished borehole is drilled in two or more stages. A smaller pilot bore is drilled first, then reamed to a diameter 6 to 12 inches greater than that of the casing and screen. The screen is selected and designed according to information gained through analysis of the cuttings, formation and electric logs. The casing string (blank pipe & screen) is generally installed in a continuous operation. Selected gravel is placed in the annular space adjacent to the screen, between the casing and enlarged hole to stabilize the formation and provide a filter against fine sand or silt. The annular space between the borehole and blank filled with cement grout. Well diameters and depths range form 4” to 24” and 100’ to 3000’ respectively. Reverse Rotary. The reverse circulation rotary method varies from the direct rotary method in three major respects. The circulating fluid flows down the hole and up the drill pipe. Drilling fluid hydrostatic pressure against the formation maintains the wall of the borehole from caving both systems, usually no additives are mixed with the circulating water (drilling fluid). The reverse circulation procedures, the hole is normally drilled in one pass without staging. Well completion (blank casing, screen, gravel placement and grout) are installed in the same manner as the direct rotary process. Equipment requirements differ in that drill pipe diameters range from 6” to 10” and a high capacity suction lift pump is normally used to create the “reverse” flow. A compressor is required for deep well applications to induce reverse flow via air lift pumping action. The reverse rotary method is particularly applicable to unconsolidated formations, where large diameter-high capacity well construction is required. Well diameters and depths generally range from 18” to 42” and 100’ to 1500’ respectively.

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Air Rotary. The air rotary method is similar to the rotary hydraulic method in that the same type of drilling machine and tools may be used. The principal difference is that air rather than mud or water is used as the drilling fluid. In place of the conventional mud pump to circulate the fluids, air compressors are used. The air rotary method is best suited for consolidated formation, and is especially popular in regions where limestone is the principle water source. The air rotary method requires that air be supplied at pressures from 100-250 psi. To effect removal of the cuttings, rising velocities of at least 3000 fpm are necessary. Penetration rates of 20-30 fph in hard rock are common with air rotary methods.

Characteristics Range of practical depths (general order of magnitude) Diameter

Dug 0-50 ft. (0-15 m) 3-20 ft. (1-6 m)

Bored 0-100 ft. (0-30 m) 2-30 in. (51-762 mm)

Driven 0-50 ft. (0-15 m) 1 1/4-2 in. (32-51 mm)

Jetted 0-100 ft. (0-30 m) 2-12 in. (51-305 mm)

Type of geologic formation: Clay Silt Sand Gravel

Yes Yes Yes Yes

Yes Yes Yes Yes

Yes Yes Yes Fine

Cemented gravel Boulders

Yes Yes

No No

Yes, if soft and/or fractured

No Yes, if less than well diameter Yes, if soft and/or fractured

Yes Yes Yes 1/4-in (6-mm) pea gravel No No

Thin layers only No

No No

No

No

No

No

Air 0-750 ft. (0-229 m) 4-10 in. (102-254 mm)

Sandstone Limestone Dense igneous rock

Drilled Characteristics Range of practical depths (general order of magnitude) Diameter Type of geologic formation: Clay Silt Sand Gravel Cemented gravel Boulders Sandstone Limestone Dense igneous rock

Percussion 0-1000 ft. (0-305 m) 4-18 in. (102-457 mm)

Direct 0-3000 ft. (0-610 m) 4-24 in. 102-610 mm)

Rotary Reverse 0-1500 ft. (0-455 m) 18-42 in. (305-762 mm)

Yes Yes Yes Yes Yes Yes, when in firm bedding Yes Yes Yes

Yes Yes Yes Yes Yes (Difficult)

Yes Yes Yes Yes (Difficult) (Difficult)

No No No No No No

Yes Yes Yes

No No No

Yes Yes Yes

Note: The range of values in this table are based upon general conditions.

Section 1B Groundwater & Wells

1-19

Section 1

Table 1-2: Suitability of Well Construction Methods to Different Geological Conditions

GRUNDFOS ENGINEERING MANUAL

Figure 1-14: Typical Rotary Drilled Well Completions

A. Unconsolidated Formation Ground Surface Sloped to Drain Away from Well

Plug Air Vent

Discharge Sanitary Well Seal Outer Casing

Top Soil

Section 1

B. Consolidated Formation

Connection to Source of Power Clay

Drill Hole Diameter for Cemented Casing Cement Grout

Artesian Pressure Surface or Piezometer Surface Inner Casing

Cement Grout Formation Seal

Drill Hole Through Soft Formation

Dynamic (Pumping) Water Level

Caving Formation Cased Out

Submersible Pump

Pumping Unit Maximum Dia. Open Hole Water Bearing Sand Taper Section Screen

Hole Diameter on Bottom

Drilling Method Selection Factors. Many factors are considered in selection of drilling method and well design. Among them are depth, diameter, hardness of formation, presence of fine-grained aquifers that need a gravel envelope filter, accessibility of site to equipment and availability of the quantity of water required for drilling. Rotary drilling construction - particularly reverse rotary, requires large amounts of water. In some areas, gravel envelope wells permit the production of greater quantities of water than non-gravel envelope wells, but this is not always the case. Many high efficiency water wells are being constructed today by the cable tool method. The diameter of a well should be selected only after a careful consideration of all factors such as the desired yield; the type of well construction; the type of pumping equipment to be used; the physical character of the water bearing formation; etc. The ability to produce sand-free water from water-bearing sands is related to the diameter of the well. A larger well diameter coupled with screen open area will decrease the velocity of the water as it enters the well. Decreased velocity reduces the possibility of pumping fine sand. Sanitary Construction of Wells. Although there are different types of wells and construction methods, there are basic sanitary aspects that apply to all. The broad issues are described as follows: • The annular space outside the casing should be filled with a watertight cement grout or suitable impermeable material form the surface to the deepest level of excavation or as deep as necessary to prevent entry of contaminated water, whether from surface runoff or other aquifers. • For artensian aquifer, the casing should be sealed into the overlying impermeable formations so as to retain the artesian pressure. • When a water-bearing formation containing water of poor quality is penetrated, the formation should be sealed off to prevent infiltration of water into the well and aquifer. 1-20

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

• A sanitary well seal with an approved vent should be installed at the top of the well casing to prevent entrance of contaminated water or other objectionable material. The well seal should be installed per the appropriate regulatory requirements. A pitless adapter and cap assembly should be used in situation where applicable. For large-diameter shallow wells, it is difficult to provide a sanitary well seal to the depth normally required by most regulatory authorities. A typical surface completion consisting of a reinforced concrete slab, overlapping the casing and sealed to it with a flexible sealant or rubber gasket are normally used to affect a sanitary seal. The annular space between the casing and bore hole should first be filled with suitable grouting or sealing materials before surface completion.

1. The type of water bearing formation. a. Consolidated formations - limestones, sandstones, granites, etc. b. Unconsolidated formations - alluvial, glacial, sand and gravel deposits, etc. 2. The permeability of the water bearing formation. (The ability of the formation to yield water). 3. Design capacity of the well. 4. The type of deep well pump to be utilized. High capacity submersible pumps may require a larger diameter than turbine pumps to facilitate power cable installation; although alignment may be less critical. Type of water bearing formation a. Wells drilled into consolidated formation are normally more expensive and deeper than shallow unconsolidated wells, the diameter is normally kept as small as possible in line with the diameter of pump to be used. Normally, a minimum of 2” is allowed between the pump end/ bowl and the casing, and 3” between the casing and borehole. b. In unconsolidated formations, the screen diameter may depend upon the bowl /pump diameter but may be increased to: 1. Reduce the entrance velocity through the screen. 2. Increase the screen opening area for longer life if mineral deposition from the ground water is a problem. 3. A minimum of 8” is added to the screen diameter for the gravel wall diameter (4” annulus). A 12” increase (6” annulus) is recommended; however, larger annular clearance may improve well performance. Note: Typical guidelines for screen and gravel pack selection are overviewed in Section 1B. Permeability of the Formation Increasing the well borehole diameter in a consolidated formation will increase the yield somewhat, depending on how many additional crevices are encountered by the increased diameter. In unconsolidated formations it is often wise to increase the well diameter in formations with low permeability so that the maximum flow can be obtained. The higher the permeability the less the well diameter will increase the specific capacity (well yield). Design Capacity Local knowledge from existing well completions, local hydrology and geology studies can be used to estimate well yield and estimate pump size. The pump chamber casing diameter can be determined by estimating the maximum pump unit diameter (based on well yield) by adding at least 2” the minimum pump diameter, 3” is recommended for ease of installation of submersible units casing diameter vs pump/motor size are listed in Table 1-4. Downhole Logs and Geophysical Investigative Methods. Numerous instruments and techniques are available for special investigations of sub-surface and groundwater conditions. Logging equipment can be lowered into a well via wireline, measurements and other data are recorded at the surface by electrical means. Several of the most commonly used logging techniques used in the water supply industry are presented as follows: 1. Electric log: (single point, short normal - 16” and long normal - 64”): Used in uncased fluid filled boreholes and are typically used for; identification of lithologic (sand, clay, etc.), determine high and low permeability zones, and casing depth in cased hole applications 2. Caliper log: Measures hole diameter at any depth; useful to locate large casing breaks, determine of size and position of casing and liners, location of caving formations (shales, cavernous limestone, etc.), determination of the effectiveness of “shooting” for well development and/or enlarging diameter, etc.

Section 1B Groundwater & Wells

1-21

Section 1

Well Completion Considerations. The well size and completion method depends upon four principal issues:

Section 1

GRUNDFOS ENGINEERING MANUAL

3. Temperature log: Measures water temperature at any depth; useful in locating sources of flow into the well, casing leaks, etc. 4. Fluid Velocity log: Measures flow (natural or artificial) at any point in hole-either up or down; useful in determining contributing permeable and “thief” zones, casing leaks, etc. 5. Radiation log: Similar in use to electric logging, but can be used in cased well or open hole. Radio- active logs are generally source collecting and measure the natural radioactivity of the fomation material. They are extremely useful where formation materials are known to have higher natural radioactivity compared to others (ie. clays are often more radioactive than sands in certain geologic areas). 6. Water Sampler: Permits collection of water samples for analysis from any depth in the well. 7. Video log: Video logs are predominately used to identify the location of casing imperfections (breaks), screen damage or verification of prominent features at the proper depth. Other geophysical methods, such as surface seismic and electrical resistively surveys, have been successfully used in many areas to map the bedrock surface in order to identify sub-surface water-bearing sand or gravel. Such surveys do not replace a program of test drilling, but merely serve to aid in selecting the most favorable sites for test holes and/or wells. These special geophysical investigative method are normally conducted in area where geology is highly variable and well productivity is highly variable. Logs and Samples. In drilling any well, regardless of the method used (i.e. cable tool, rotary, etc.) the driller should keep an accurate formation log and completion records. The logs and records should include: the location of the well; name of owner; owner’s well number; total depth of borehole, casing and screen; borehole size; elevation at the surface (if known); depth, thickness, and character of each type of formation material penetrated (lithologic information); depth (s) at which water was encountered - if possible; depth to water level upon completion of the well; the date the well was started and completed. The state or regulatory agency having regulatory jurisdiction will require a driller report be filed. The driller report will generally require the above minimum information. Well production data (flow rate, draw-down, water levels, etc.), as well a final pump installation data if known, should be complied. In the construction of high capacity water wells, the drilling and pump contractor may be different, making record collection difficult if not specifically identified by contract. Such records are invaluable as they are required for proper pump sizing and future system expansion-particularly if additional wells are to be drilled nearby or if the well requires any repair or reconditioning. Actual formation and geophysical logs (electric logs, etc.) are usually much more valuable than the written log kept by the driller, both samples and logs should be kept for analysis and maintained until all regulatory reports are filed and/or contractual data is provided to the owner or its agent. In unconsolidated formations, where a gravel pack well completion is to be made, representative formation samples in the water bearing zone, collected during the drilling process are often analyzed. The purpose of the analysis is to determine formation grain size distribution via sieve analysis. The grain size distribution of water bearing formation is key factor in gravel pack selection and/ or screen aperture size selection. Water Well Casing and Pipe. There are several kinds of steel pipe suitable for casing drilled wells. The commonly types are; standard pipe, line pipe, drive pipe, reamed and drifted (R&D) pipe, and water-well casing. Steel possesses high strength and resiliency required for water well service, and is weldable. There are certain differences in size, wall thickness, type of connection and method of manufacture. Well casing must meet certain generally accepted specification for quality of steel and wall thickness. Both are important because they determine resistance to corrosion and consequently the useful life of the well. Strength of the casing may also be important in determining whether certain well-construction procedures may be successfully carried out, particularly in cable-tool drilling where hard driving of the casing is sometimes required. The most commonly accepted specifications for water well casing are those prepared by the American Society for Testing and Materials (ASTM), American Petroleum Institute (API), and the American Iron and Steel Institute (AISI). Table 1-3 lists the minimum acceptable wall thickness requirements for carbon steel water well casing based on diameter and depth. If conditions are known to be corrosive; consideration should be given to corrosion resistant material such as stainless steel, plastic, fiberglass or the use of greater wall thickness carbon steel pipe. PVC plastic casings should be made of a material approved for use with potable water by the National Sanitation Foundation (NSF). 1-22

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Table 1-3: Suggested Minimum Thickness for Carbon Steel Water Well Casing

6

8

10

0-100 100-200 200-300 300-400 400-600 600-800 800 +

12 12 10 10 10 3/16 3/16

12 12 10 8 8 3/16 3/16

12 10 8 8 3/16 3/16 3/16

Casing Diameter (in.) 12 14 16 18 10 8 8 3/16 3/16 3/16 1/4

10 8 8 3/16 3/16 1/4 1/4

8 8 3/16 3/16 1/4 1/4 1/4

8 3/16 3/16 1/4 1/4 1/4 5/16

20

22

24

30

8 3/16 3/16 1/4 1/4 5/16 5/16

8 3/16 1/4 1/4 5/16 5/16 3/8

8 3/16 1/4 1/4 5/16 3/8 3/8

3/16 1/4 1/4 5/16 5/16 3/8 7/16

Note: 1. Diameter thickness in U.S standard gauge or fraction of a inch. 2. A minimum of 1/4” wall thickness is normally specified for high capacity water well for municapal purposes. Refer to Section 7A for a overview of the various tubular products used in the water supply industry. Well Casing Diameter vs. Pump Size. The diameter of the upper pump housing casing must provide sufficient clearance between the largest pump component diameter and the casing. In addition to accommodating the obvious pump and motor dimensional requirements, a clearance allowance must be made for power cable and a water level measurement device. No well is exactly “straight” (perpendicular to ground level) and operation will be unsatisfactory if there is severe misalignment. In addition, consideration should be given to the possibility of corrosion product buildup which may lock the pump to the casing. It is recommended that pump housing casing should have a minimum diameter at least two inches greater than the nominal diameter of the largest pump component (ie. pump, motor or column pipe collar) required for desired yield. Table 1-4 and 1-5 can be used as a guideline for determining the minimum casing size for a given flow, pump diameter or speed. Table 1-4: Casing Diameter vs. Well Capacity and Pump Diameter

Q (gpm)

Minimum Casing Dia. (in.)

Recommended Casing Dia. (in.)

*Pump/ Motor Dia.(in.)

0 to 25 0 to 100 100 to 300 300 to 700 700 to 1400 1400 to 2000 2000 to 3000 3000 to 4500

4 ID 6 ID 8 ID 10 ID 12 ID 14 OD 16 OD 18 OD

6 ID 8 ID 10 ID 12 ID 14 OD 16 OD 18 OD 20 OD

>4 4 6 8 10 12 14 16

* Pump, motor or column pipe coupling diameter whichever is larger.

Section 1B Groundwater & Wells

1-23

Section 1

Casing Depth (ft.)

GRUNDFOS ENGINEERING MANUAL

Table 1-5: Casing Diameter vs. Well Capacity & Pump Operating Speed

Nominal Op. Speed (rpm)

Capacity/Yield (gpm)

Minimum Casing Dia. (in.)

Recommended Casing Dia. (in.)

2 **

-

0 - 10

2

3

3 **

3600

2 - 25

3

4

4*

3600

5 - 75

4

6

6*

3600 1800

50 - 350 100 - 200

6

8

7

3600 1800

100 - 500 50 - 275

8

10

8

3600 1800 1200

200 - 1200 150 - 600 100 - 400

10

12

10

3600 1800 1200

500 - 1800 200 - 1500 370 - 670

12

14

12

3600 1800 1200

600 - 2500 400 - 2300 250 - 1500

14

16

14

1800 1200

1000 - 4500 800 - 3500

16

18

16

1800 1200

2000 - 5200 1300 - 3400

18

20

18

1800 1200 900

3200 - 5400 2200 - 4000 2800 - 3000

20

24

Section 1

Nominal Pump Diameter (in.)

Note: (1) For non-domestic submersible applications, it is recommended that the well inside diameter (I.D) be a minimum of 2” larger than the largest submersible component. (2) For pump settings in excess of 400 feet, the minimum well ID should be increased to the next larger standard size when practical. * Domestic sized pumps and motors are typically 1” smaller than the casing I.D. ** Special use submersible pumps or shallow well suction lift pumps Well Casing Accessories. In addition to the casing and screen, high capacity water wells completed in sand and gravel formations using the rotary drilling method will often employ special components to enhance the completion. Several of the most commonly employed casing accessories are: (1) welding collars, (2) carbon steel to stainless steel change over connector, (3) compression section, (4) casing guides, (5) float plates and (6) taper (reducer reduction) section. 1. Welding Collars are factory installed to one end of each casing or screen joint to facilitate quick casing installation by reducing set-up, welding and alignment time. Lap welded collared joints provide a stronger connection than butt welded joints. 2. Carbon Steel to Stainless Steel Change Over Connectors are used reduce the rate of galvanic corrosion between dissimilar metals, which can occur when stainless steel well screen is joined to carbon steel blank casing. Change over connectors range from insulated couplings to special slip weld connections, where there is no direct weldment between the stainless steel and carbon steel material. The slip weld connection relies on the formation of a oxide layer on the carbon steel surfaces where it contacts stainless steel to inhibit corrosion. If

1-24

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

stainless steel is welded directly to carbon steel, the carbon steel section should be at least two times the thickness of the stainless. 3. Compression Sections are often used in areas prone to subsidence as a result of groundwater mining, and in earthquake prone regions. The compression section provide a casing stress relief point should the ground surface drop in the immediate vicinity of the well head.

5. Float Plates are installed in the casing, where the weight of the casing (screen and blank casing) exceed the safe lifting capacity of the drill rig. The float plate allows for buoyancy forces to counter the weight of the casing as it is installed. The weight of the casing is reduced by the weight of the fluid displaced. Fluid is added to the casing after each successive connection to force the casing down. When the casing operation is completed the float plate, is removed by impact (striking) with drill pipe or bailer. Float plates are typically constructed of cast iron, which has high strength but low impact resistance. 6. Taper Sections are used to provide a smooth transition from casing and/or screen of different diameters. Long transition (3 - 4 ft.) fabricated diameter reductions are preferable to abrupt changes in diameter from a construction and maintenance stand point. Gravel Pack. The gravel filter pack envelope well serves two vital purposes; (1) stabilizes the casing (blank casing and screen) between the boreholes by filling the annular space and (2) provides a graded filter for the fine grained particles in the aquifer. Neither purpose can be achieved if the gravel pack is not placed in a continuos and uniform manner in the annulus. Formation analyses associated with the gravel pack and screen aperture size selection process are discussed in greater detailed later in Section 1B. Gravel pack selection based solely on formation sampling can be misleading as it assumes formation samples are truly representative of the aquifer. Strict adherence to good formation sampling collection and analysis procedures are required where no historic data is available. In well established groundwater basins, field experience and past applications can be used to supplement analytical techniques. Grouting (Annular Seal). The penetration of a water bearing formation by a well provides a direct route for possible contamination of groundwater. This space must be filled with grout to prevent surface contaminants from running down the annulus and into the aquifer. A properly installed grout seal reduces the possibility of contamination. Sealing the annulus in the non-producing formation zones has other advantages, in addition to sealing out poor quality water from an overlying aquifer; it increases the life of the well by protecting the casing against exterior corrosion; and it stabilizes the soil and rock formation to help prevent caving. Water Well Screen. Screens or slotted casings are installed in wells to permit sand-free water to flow into the well and to provide support for unstable formations to prevent caving. In a drilled well, the screens are normally placed after or at the same time the casing is installed. In a driven well, the screen is a part of the drive assembly and is sunk to its final position as the well is driven. The size of the slot (aperture) for the screen or perforated pipe should be based on a sieve analysis of selected samples from the water-bearing formation that is to be developed or gravel packed. The analysis is usually made by the screen manufacturer or contractor. If the slot size is too large, the well may yield sand when pumped. If the slot size is too small, it may become plugged with fine material, and the well yield will be reduced. Common types of manufactured screen include; milled slot, wire wrap, bridge slot and shutter screen. Slots cut with a down hole mill knife or holes burned into the bottom end of the casing string should not be substituted for a manufactured well screen.

Section 1B Groundwater & Wells

1-25

Section 1

4. Casing Guides are used primarily to center screen within the borehole. In water well applications, guides are typically attached by welding and are placed at forty foot intervals. Three to four guides are used at each interval and are placed equidistantly around the screen. Guides are not typically used with blank casing, unless special cementing (grouting) requirements are specified.

GRUNDFOS ENGINEERING MANUAL

Section 1

The relationship between screen open area and entrance velocity of water through the openings should be considered if maximum hydraulic efficiency is desired. Loss of energy in the form of incereased draw down and formation material transport is kept to a minimum by holding velocities between 0.1 fps and 0.5 fps. These low entrance values are often unobtainable and as a practical matter, velocities up to 3.5 fps have been employed without appreciable loss in well efficiency or transport of formation material, in properly designed gravel pack wells. Since slot size is determined by grain size distribution in the aquifer sand or gravel pack, the required open area must be obtained by varying the diameter or, if aquifer thickness permits, by varying the length of the screen. Manufacturers of well screens provide tables of capacities and other information to facilitate selection of the most economical screen dimensions. A screen is seldom required in wells that tap bedrock fractures or tightly cemented sediments such as sand stone or limestone. Well Screen Diameter Considerations. Well screen diameter does not have much effect on production water yield; however, there are strong reasons for specifying identical casing and screen diameters (with the exceptions of telescoped screen installations and under-reamed gravel envelope well designs). Equal internal diameters facilitate well development, redevelopment and provide options should special conditions such as formation gas, incrustation, corrosion or sand become a issue. The possibility of damage due to dropping a pump or tools is minimized. Maintaining identical diameters reduces head loss through the screen and improves well efficiency. Wells smaller than six inch diameter are difficult to repair and larger diameter wells are easier to deepen where well construction and formation condition make such practices possible. In wells deeper than 1,200 feet, a reduction of four inches in screen diameter can be practical. This is generally limited to high capacity wells where the screen diameter is a minimum of 12 inches. The saving in screen and borehole costs may offset other considerations. This reduction normally begins at the bottom of the pump housing casing. Formation Analysis - Gravel Pack and Screen Aperture Selection. Evaluation of representative formation samples (sand in the interval to be screened) is performed to determine screen aperture (slot) size. The two principal forms of high capacity water well completions in unconsolidated water bearing sands are “gravel pack” and “naturally developed”. (1) In a gravel pack completion, the well diameter in the vicinity of the screen is typically 12” larger than the screen and graded gravel is used as a filter media to prevent sand pumpage. The screen aperture is sized to retain a majority of the gravel pack. (2) In a naturally developed well completion, the well is drilled no larger than required to insert the screen and casing. The screen aperture is sized to retain a majority of the natural formation material. Filler gravel is sometimes used to fill void space between the borehole/casing string annulus. A complete course in well design and gravel pack selection is outside the scope of this manual; however, general screen aperture size selection criteria and related information are presented in the following figures and tables.

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Table 1-6: General Screen Aperture (slot) Size Selection Criteria

Naturally Developed Wells Step 1) Obtained samples representative of formation materials Step 2) Perform formation grain-size (sieve) analysis Step 3) Select slot size that retains > 70% of formation materials

Section 1

Gravel Packed Wells Step 1) Obtain samples representative of formation materials Step 2) Perform formation grain-size (sieve) analysis Step 3) Select filter medium (sand) based on 70% retained formation grain size multiplied by: • 3 if formation is fine and uniform, or • 6 if formation is coarse and non-uniform (uniformity coefficient of filter medium should be less than 2.5) Note: Gravel pack selection is sometimes based on maintaining a Grave Pack Ratio (GPR = 50% gravel pack size/50% formation size) of 5 to 7. The gravel pack distribution should parallel the formation distribution. Step 4) Select a slot size that retains 95 - 100% of filter pack materials Note: Uniformity Coefficient = Grain Size Retained @ 40%/Grain Size Retained @ 90% Table 1-7: Common Screen Aperture (slot) Size Selection Practices vs Filter Pack/ Grain Size

Aperture Size in.

mm

Media Distribution U.S. Sieve Size Range

0.006 0.010 0.020 0.030 0.040 0.060 0.080

(0.15) (0.25) (0.50) (0.75) (1.0) (1.5) (2.0)

50 - 100 20 - 40 12 - 20 12 - 20 8 - 12 6-9 4-8

Figure 1-15: Typical (% Retained) Grain Size Distribution

CUMULATIVE % RETAINED

100

Grain Size Distribution % Retained

80 60 40 20 0

10

20

30

40

50

60

70

80

90

100

GRAIN SIZE, THOUSANDTHS OF AN INCH

Section 1B Groundwater & Wells

1-27

GRUNDFOS ENGINEERING MANUAL

Section 1

Table 1-8: Physical Properties of Water Bearing Sand and Gravel Formation Materials

Sieve Standard Tyler Standard U.S. Standard Sieves Sieves – – 4 4 6 6 8 8 9 10 10 12 12 14 14 16 16 18 20 20 24 25 28 30 32 35 35 40 48 50 60 60 65 70 80 80 100 100 150 140 200 200 250 230 – –

Sieve Opening Opening Opening (Inches) (Microns) .250 6350 .187 4699 .131 3327 .093 2362 .078 200 .065 1651 .055 1400 .047 1180 .039 1000 .0328 850 .0276 710 .0234 600 .0195 500 .0164 425 .0116 295 .098 250 .0082 210 .069 175 .0058 147 .0041 105 .0029 74 .0024 62 – 20

Grain Size Classification (USGS Method) Medium Gravel

Fine Gravel

Coarse Sand

Medium Sand

Fine Sand

Silt & Clay

Transport Velocity Lifting Settling (fps) (fph) – – 2.75 – – – – – 0.58 – – – – – – 0.35 1181 – – – – – – 0.25 626 – 496 – 378 – – – 248 – – – 177 0.10 94 – 71 – 45 – 7

Note: (1) microns = mm x 1000, (2) fps = ft./ sec., (3) fph = ft./ hr. (4) AWWA Material Classification by Grain Size • Gravel 0.080” (2.032 mm) • Very coarse sand 0.040” - 0.080” (1.016 - 2.032 mm) • Coarse sand 0.020” - 0.040” (0.508 - 1.016 mm) • Medium sand 0.010” - 0.020” (0.254 - 0.508 mm) • Fine sand 0.005” - 0.010” (0.127 - 0.254 mm) • Very fine sand 0.003” - 0.005” (0.076 0.127 mm) • Silt and clay < 0.003” (< 0.076 mm) Well Development. Developing the well is necessary to obtain its maximum capacity for a given drawdown. The developing process usually uses hydraulic agitation to remove the fine material from the formation near the well casing perforations, thereby opening up passages so that the water can enter the well more freely. Typical methods used for well development include but are not limited to; air lift pumping, swabbing - via surge block and test pumping. All three methods agitate and surge the water-bearing strata adjacent to the well screen, which washes out the fine material from the formation. The method of development must be suited to the aquifer and the type of well construction. Proper development is necessary to maximize well yield and remove formation materials that might otherwise damage production pumping equipment or plug the well. Well development is required/recommended after completing most drilling and well construction processes.

1-28

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Sand Content. Issues associated with sand content concentration levels are discussed in Section 2D, under the heading of “Entrained Solids (Sandy Water)”. In general, the sand content of a new and fully developed water well should not exceed 5 mg/l, 15 minutes after start-up.

Long term pump test data can be used for aquifer analysis in conjunction with water level recovery data. Water level recovery (residual drawdown) measurements can provide significant aquifer information and typically range from 1 - 24 hours. A step drawdown test is sometimes performed at several flow rates to develop a well performance curve for the purposes of determining well efficiency. Pump test data is used to select the production pumping equipment for the intended application, and should be corrected for seasonal variations as applicable. Failure of the well to recover completely to the original static water level within the same time period as the pump test, is an indication of aquifer storage depletion. Well Alignment - Pump Setting Limits. The Bureau of Reclamation recommends that all casing to the lowest contemplated pump setting should not deviate for vertical more than 3 inches per 100 ft. for casings up to 6 inches diam., 4 inches per 100 ft. for casing 8 to 12 inches diam., and 6 inches per 100 ft. for casing 14 to 18 inches diam. All casings up to 20 inches diam. should be sufficiently straight to permit free passage of a 40 ft. length of pipe with couplings at each end and in the middle, of the next smaller size than can enter the well casing. The AWWA recommends that the outer diameter of the plumb or dummy should not be more than 1/2 inch smaller than the diameter of the part of the casing or hole being tested. The dummy is recommended to consist or a rigid spindle with 3 rings each 12 inches wide and truly cylindrical. If the dummy fails to move freely throughout the length of the casing or hole to the lowest anticipated bowl setting, or should the well vary from vertical in excess of 2/3 of the smallest diameter of that part of the well being tested per 100 ft. of depth, it is not satisfactory. Impact of alignment deviation on pump installation are: • A drift of 3” per 100 ft. of well depth is of little or on consequence. • A drift of 3 to 6” per 100 ft. of well depth is less desirable but not serious if the well is straight. • A drift of more than 6” per 100 ft. of depth may be extremely troublesome unless the pump is much smaller than the well casing. Note: A” dog-leg” in the well is a problem regardless of alignment drift. Plumbness and Alignment Survey. AWWA standard A100 - 97 provides a procedure for conducting a Plumbness and Alignment (deviation) survey. The purposes of such a survey is to graphically depict well alignment, as well as identification of dog-legs which can make a well unusable depending on the location and surverity. The alignment survey procedure is addreviated as follows: Test Fixture Set-up. Using the test fixture as shown in Figure 1-16. The horizontal center of the pulley “C” should be exactly 10 feet above the top of the well. The vertical center of the pulley must be so located that the plumb line “A” will come off its outer edge exactly over the center “D” of the well casing. Unless this point is closely established the well survey will not be corrected. The plumb ring “E” should be 1/4” smaller than the inside diameter of the well casing and should be heavy enough to keep the plumb line taut. The ring must not be solid as the water must pass through it as it is lowered in the well. The hole “F” through which the plumb line “A” passes must be in the exact center of the ring. Marks should be made every 10 feet on the plumb line, to indicate the depth the ring has been lowered in the well.

Section 1B Groundwater & Wells

1-29

Section 1

Performance Testing. After the well is developed, a long term pump (yield) test is normally conducted on the well using a test pump. Depending on the formation and historical data, the duration of a long term pump test at the design flow rate can range from 8 to 72 hours. The pump test should be conducted until the pumping water level remains stable and/or as required by contract. It is important that the test pump be accurately sized for the well in order to obtain the best test results. The test pump should have variable speed capability, with 10 - 50% greater capacity and lift than anticipated at full load speed. Test data should include the static water level (standing water level), pumping water level, discharge rate, water level, sand content, recovery measurements and duration.

GRUNDFOS ENGINEERING MANUAL

Drift Calculation Procedures. Well drift characteristics are determined by lowering the plumb ring 10 feet at a time and taking a reading at each 10’ interval. If the plumb line passes exactly through the center line “D” at any location, the well is plumb at the depth the plumb ring is suspended. If the line “A” does not pass through “D”, the well at that depth is out of plumb by the distance “A” varies from “D” plus an equal distance for each 10 feet that the plumb ring “E” is below the reference datum level.

Section 1

Example 1-1: Well Alignment - Drift Calculation.

Assume that “c” is exactly 10’ above the reference datum and “D” is at datum level. (1) If plumb line “A” varies 1/16 of an inch form the center of the well at “D” and the plumb ring “E” is 10 feet below the reference line, then the well is 1/8 out of plumb at the 10 foot level. (2) If “A” varies 1/16 inch form the center of the well “D” when the plumb ring “E” is 50 feet below the datum at “D”, then the well is 1/16 plus 5/16 or 3/8 of an inch out of plumb at the 50 foot level. The amount of drift is related to the proportional relationship of similar triangles, and is illustrated as follows: 60 ft. 10 ft.

x

1 16

=

3 8

Drift calculations at the various depths tested may be plotted on graph paper for a graphical depiction of alignment. Typical forms of plumbness and alignment presentation are illustrated in Figure 1-17 and 1-18. Figure 1-16: Alignment Survey Text Fixture Guide Pulley "C"

10'0" Exact Well Center "D"

Exact Center "F"

Plumb Line "A"

Plumb Ring "E"

Frame "B" Datum

Knots Every 10 ft.

"E"

1-30

Section 1B Groundwater & Wells

Figure 1-17: Typical Alignment Survey Longitudinal Projections

GRUNDFOS ENGINEERING MANUAL

Table 1-9: Typical Plumbness and Alignment Test Data Sheet

Well No. 1 Date: 3-21-75 Size of Hole or Casing = 19-1/4 in., ID Size of Plummet = 18-1/4 in. OD. Height of Apex Above Top of Well = 10.0 ft. Depth of Plummet Below Top of Well (ft) North .01 .10 .01 .01 .01 .005 .005 .005 .005 .005 .005 .005 0

South

East 0

0 .005 .01 .01 .01 .01 .01 .01

0 0

Calculated Drift of Well (ft) West 0 .01 .015 .015 .015 .015 .015 .02 .02 .02 .01 .01 .005 0 0 .005 .005 .01 .01 .01

North .02 .03 .04 .05 .06 .35 .04 .045 .05 .055 .06 .065 0

South

East 0

0 .075 .16 .17 .18 .19 .20 .21

0 0

West 0 .03 .06 .075 .09 .105 .12 .18 .20 .22 .12 .13 .07 0 0 .085 .09 .19 .20 .21

Figure 1-18: Graphical Representation of Plumbness Requirements

Drift is greatest at depths 100 ft. and 200 ft. Depth ft.

Actual Drift in.

Allowed Drift* in.

100 200

2.75 3.63

12.83 25.66

North .20 ft Depth 100 ft t=2

.

East

.10 ft

.10 ft

.20 ft

.10 ft

ft

=

3.

63

in .

.20 ft

Imaginary Vertical Line

.75 in

West

.3 0

*For 19.250 in. ID casing.

.10 ft

.23 f

Depth 200 ft

.20 ft South

Note that this well meets the specifications for plumbness.

Section 1B Groundwater & Wells

1-31

Section 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Horizontal Deflection of Plumb Line (ft)

GRUNDFOS ENGINEERING MANUAL

Well Covers and Surface Seals. Every well should be provided with an overlapping, tight-fitting cover at the top of the casing or pipe sleeve to prevent contaminated water or other material from entering the well.

Section 1

The sanitary well seal for a well exposed to possible flooding should be either watertight or elevated at least 2 ft. (0.6 m) above the highest known flood level. When it is expected that a well seal may become flooded, it should be watertight and equipped with a vent line that has an opening to the atmosphere at least 2 ft. (0.6 m) above the highest known flood level. Under normal circumstances, the minimum height or vent is usually specified by the regulatory agency having jurisdiction for public water supplies. The seal in a well not exposed to possible flooding should be either watertight (with an approved vent line) or selfdraining (non-watertight) type, all openings in the cover should be either watertight or flanged upward and provided with overlapping, downward flanged covers. All sanitary well seals, pitless adapter units, and caps must be approved by local or state health departments. Pumps should have a supporting base that can be effectively adapted to seal the upper terminal of the well casing. There are several acceptable sanitary well seal designs for submersible pumps consisting of an expandable neoprene gasket compressed between two steel plates (Figures 1-19 and 1-20), which are easily installed and removed for well servicing. If the pump is not installed immediately after well completion, the top of the casing should be closed with a metal cap screwed or tack-welded into place, or covered with a sanitary well seal. A well slab alone is not an effective sanitary defense and alone, may not be permissible for public water supply purposes. A cement grout formation seal is far more effective. Concrete slab or floor around the well casing to facilitate cleaning and improve appearance should be placed only after the formation seal and/or the pitless installation have been inspected. Well covers and pump platforms should be elevated above the adjacent finished ground level. Pump room floors should be constructed of reinforced, watertight concrete, and carefully leveled or sloped away from the well so that surface and wastewater cannot stand near the well. The minimum thickness of such a slab or floor should be 4 in. (100 mm). Concrete slabs or floors should be poured separately from the formation seal. All water wells should be readily accessible at the top for inspection, servicing, and unobstructed access for wellservicing equipment. Figure 1-19: Typical Large Submersible Pump (LSP) Discharge Styles & Surface Plate Assemblies

Notes: 1. Well seal surface plates are for use where a sanitary well sealing is required; a flange must be welded to the casing by a continuous watertight weld or the plate must be grouted in place. Ordinary surface plates may be used where sanitary well seals are not required. 2. The surface discharge assembly must physically comply and be installed in accordance with state or federal sanitary requirements having jurisdiction. Vent well as required for service and/or sanitary requirements.

1-32

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

Figure 1-20: Typical Submersible Pump (Small Submersible) Discharge and Well Seal Completion Pipe Plug Well Vent

Power Cable Drop Pipe Basket

Wire Mesh

Bolt

Section 1

Access Plug (Threaded)

Discharge Line

Well Cap

Casing

Concrete Base

Drop Pipe from Submersible Pump

Submersible Pump Cable

Abandoning Wells. Unsealed, abandoned wells constitute a potential hazard to the public health and welfare of the surrounding area. Sealing an abandoned well presents certain problems, and the solution involves consideration of well construction and the geological and hydrological conditions of the area. Factors to be considered when sealing an abandoned well are elimination of any physical hazard, prevention of any possible contamination of groundwater, conservation and maintenance of the yield and hydrostatic pressure of the aquifer, and prevention of contact between desirable and undesirable waters. When a well is to be permanently abandoned, the well should be filled with concrete, cement grout, neat cement, or clays with sealing properties similar to those of cement in accordance with the regulatory agency having jurisdiction. Care should be taken to insure sealing material does not bridge during installation. It is recommended that the top of the casing be cut-off five feet below the finished grade after the well is filled with impermeable material. Well Failure. Over a period of time, wells may fail to produce for any of the following reasons: • • • •

Failure or wear of the pump. Declining water levels. Plugged or corroded screens. Accumulation of sand or sediments in the well.

Proper analysis of the cause necessitates measuring the water level before, during, and after pumping. To facilitate measuring the water level, an entrance for a tape or wire line electrical measuring device into the well in the annular space between the well casing and the pump column should be provided. A perminately installed airline or submersible water level transducer are often used to measure water levels and is recommended for applications requiring frequent measurements or where it is difficult to insert portable devices. The airline method is not generally as accurate as the tape, electric wire line or the pressure transducer method. If the well is completed as a pitless-adapter installation, consideration should be given as to how water level measurement can be taken.

Section 1B Groundwater & Wells

1-33

GRUNDFOS ENGINEERING MANUAL

Any work performed within the well including insertion of a measuring line could potentially contaminate the water with coliform bacteria and other organisms. Care should be exercised when procuring water level measurements. All access holes should be tightly plugged or covered following the work.

Section 1

Special Considerations in Constructing Artesian Wells. To conserve water and ensure good productivity from an artesian well, it is essential that the well casing be sealed into the confining stratum. Otherwise, water loss may occur by leakage into lower-pressure, permeable strata at higher elevations. A flowing artesian well should be designed so that the movement of water from the aquifer can be controlled. Water can be conserved if such a well is equipped with a valve or shut off device. In general, water can not be extracted from a flowing artesian well via pumping, greater than the natural flow.

Well Disinfection and Treatment Disinfection of Wells. All newly constructed wells should be disinfected to eliminate contamination from equipment, material, or surface drainage introduced during construction. Every well should be disinfected promptly after construction or repair. An effective and economical method of disinfecting wells is use of calcium hypochlorite containing approximately 70% available chlorine. This chemical can be purchased in granular or tablet form at hardware stores, swimming pool-equipment outlets, or chemical supply houses. When used to disinfect wells, calcium hypochlorite should be added in sufficient amounts to provide a dosage of approximately 50 mg/L of available chlorine in the well water. When calcium hypochlorite is not available, other sources of available chlorine-sodium hypochlorite (12-15% of volume) can be used. Sodium hypochlorite, which is also commonly available as liquid household bleach with 5.25% available chlorine. Table 1-10 shows quantities of disinfectants to be used in treating wells of different diameters. Table 1-10: Chlorine Compound Required to Dose 100 feet (30 meters) of Water-Filled Casing at 50 mg/l

Diameter of Casing in. (mm) 2 4 6 8 10 12 16 20 24

(50) (100) (150) (200) (250) (300) (400) (510) (610)

(70%) Calcium Hypochlorite 2/ (Dry Weight) 1/4 oz 1 oz 2 oz 3 oz 4 oz 6 oz 10 oz 1 lb 1 1/2 lb

(7 g) (28 g) (57 g) (85 g) (113 g) (0.2 kg) (0.3 kg) (0.45 kg) (0.7 kg)

Chlorine Compounds (25%) Chloride (12%) Sodium of Lime Hypochlorite (Dry Weight) (Liquid Measure) 1/2 oz 2 oz 4 oz 7 oz 11 oz 1 lb 2 lb 3 lb 4 lb

(14 g) (57 g) (113 g) (0.2 kg) (0.3 kg) (0.45 kg) (0.9 kg) (1.4 kg) (1.8 kg)

1 1/2 oz 7.8 oz 13.9 oz 1.4 pt 2.0 pt 3 1/2 pt 2/3 gal 1.0 gal 11/2 gal

(44 ml) (233 ml) (.4 l) (.7 l) (1 l) (1.7 l) (2.7 l) (3.8 l) (4.7 l)

(5.25%) Sodium Hypochlorite (Liquid Measure) 2 oz 9 oz 20 oz 2 1/8 pt 3 1/2 pt 5 pt 1 gal 1 2/3 gal 2 1/3 gal

(59 ml) (266 ml) (0.6 l) (1.0 l) (1.7 l) (2.4 l) (3.8 l) (6.3 l) (8.8 l)

Note: 1. Some authorities recommend a minimum concentration of 100 mg/l. To obtain 100 mg/l concentration level, double the amounts shown in the table above. 2. 70% Calcium Hypochlorite tablets (ie. HTH, Perchloron, Pittchlor, etc.) 3. Where dry chlorine is used, it should be mixed with water to form a chlorine solution prior to placing it into the well. Dry chlorine should always be added to water - not vice versa, and should be added slowly. These precautions are necessary to lessen the possibility of a violent chemical reaction. 4. 5.25% Sodium Hypochlorite solution - household bleach (ie. Chlorox, Purex, etc.) 5. 12% Sodium Hypochlorite solution - commercial bleach.

1-34

Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

General Well Disinfection Practices. The chlorine solution should remain in the well for at least 4 hours, preferable longer. After disinfection, the well should be pumped to waste, until the odor of chlorine can no longer be noticed. The well should then be tested for bacteriological quality to determine the chlorine’s effectiveness. In the case of deep wells having a high water level, it may be necessary to use special methods of introducing the disinfecting agent into the well, so as to ensure proper diffusion of chlorine throughout the well.

Bacteriological Tests Following Disinfection. The water from the system should not be used for domestic and cooking purposes until the results of the tests indicate that the water is safe for such uses. If bacteriological examination of water samples collected after disinfection indicates that the water is not safe for use, disinfection should be repeated until tests show that water samples from that portion of the system being disinfected are satisfactory. Samples collected immediately after disinfection may not be representative of the water used. Sampling is recommended (may be required) to be repeated several days after disinfection to verify the water delivered under normal conditions of operation, meet the bacteriological requirements of the National Drinking Water Regulations. Water Well Treatment. In water wells, decline in production basically is caused by: 1. 2. 3. 4.

Lowered static water level - depletion. Worn, corroded or debri plugged pump parts. Incrustation and micro - organism growths. Mud, sand and silt fouling.

Well treatment is effective only in the latter two types of situations. General. Water quality is the key indicator as to the incrustation potential of a groundwater source (see Table 1-8). The kinds and amounts of dissolved minerals and gases in groundwater determine its tendency either to corrode or to deposit mineral matter as incrustation. When the groundwater formation is penetrated by a well and exposed to changing conditions (ie. oxygen introduced, pressure/velocity changes, etc.), the natural balance is changed. The change in local aquifer conditions coupled with water quality conducive to the formation of mineral deposits, can lead to well and/or pump plugging. The four primary causes of plugging, in order of frequency of occurrence are: (1) incrustation from precipitation of carbonates of calcium and magnesium or their sulfates; (2) incrustation from precipitation of iron and manganese compounds, primarily their hydroxides or hydrated oxides; (3) stoppage due to slime produced by iron bacteria or other slime-forming organisms; (4) stoppage resulting from deposition of soil materials, such as silt and clay, carried up to the well screen in suspension. Guide to Chemical Treatment Methods. It is impossible to prescribe a method of well treatment that is applicable to every well condition. Hence the methods prescribed should be tailored to provide the optimum treatment for a specific well. Study of the well log, well record, and water analysis are often of value. The majority of chemical treatments are made with the pump in the well. If the pump is removed, variations in the application of the selected treatment method may be required to remove treatment spoils. Air-lift pumping for removal of the expended (spent) treatment solution, debris and associated dissolved materials is commonly used in the absence of a pump. Treating Solutions. Any chemical used in the treatment of a water well must be non-toxic and not impart a taste or odor to the water supply. The concentration of the treating solution is of the utmost importance. A solution that is too weak will not be effective. One that is too strong will displace or dissolve more material than can be carried by the spent chemical solution. Heavy gels or flocculent precipitates with plugging properties may result.

Section 1B Groundwater & Wells

1-35

Section 1

Flowing Artesian Wells. The water from flowing artesian wells is generally free from contamination after it is allowed to flow a short time. It is not generally necessary to disinfect flowing wells; however, should it become necessary to disinfect a flowing artesian well, chlorine solution should be placed at the bottom of the well and the well shut-in for 24 hours.

GRUNDFOS ENGINEERING MANUAL

No one chemical solution is a cure-all. The type of chemicals, volume, concentration, and method of treatment must be selected carefully for optimum results. Several of the most common well/pump treatment methods, based on the plugging mechanism identified are briefly described as follows:

Section 1

1. Chlorine Treatment. The chlorine solution is applied to the well and/or pumping equipment for sterilization and for the destruction of plugging micro-organism (bacteria and slime) growth. 2. Acidizing Treatment. Acidizing of wells and pumping equipment serves to dissolve carbonate, manganese, magnesium, and iron encrustations; and for the specific destruction of specific micro-organisms. It is also used in the development process for enlarging the pores of limestone formations, and in some cases can be used to loosen stuck drilling tools in and soluble rock formation. Acid treatments should be used in conjunction with a inhibitor to reduce corrosive attack on metal components. If zinc or magnesium anodes are used in the pump for cathodic protection, the anodes or the pump must be removed from the well prior to any acid treatment. No galvanized pipe or fittings should be used in the acid treatment. The acid quickly reacts with and dissolves the zinc or magnesium, inhibited or not generating gaseous hydrogen. 3. Phosphate Treatment. Phosphates are primarily used as a treatment for mud and silt fouling, and rely on the dispersive - detergent effect of the phosphate solution. Phosphates are sometimes used in the development process to remove excessive drilling mud. Phosphate treatments generally require mechanical surging with a surge block to be affective, which requires pump removal. A improper phosphate treatment can be extremely detrimental to the water bearing formation, and will further reduce yield. 4. Explosive Treatment. Explosive treatment “shooting” is primarily used as a well development tool for increasing the yield in tight consolidated sand stone formations. Explosives are rarely used for incrustation treatment purposes. 5. Dry Ice Treatment. Compressed carbon dioxide gas, or dry ice, has been used to some extent in well development. Its efficiency is about equal to the air lift development process. It is an inexpensive and convenient method of agitating and obtaining some back-pressure effect. It does not dissolve incrustations. In areas where well and pump plugging is a possibility or a known problem, specific well performance should be monitored on a periodic or continuous basis. Flow, drawdown and kWh/1000 gal. (energy) data can be used to establish well/pump cleaning and service intervals. Continuous monitoring instrumentation, such as the Grundfos CU3 control unit, are available for such purposes. Maintaining well efficiency through the prevention of water level decline from plugging, as a result of incrustation or fouling is extremely important. Energy costs to pump can be many times the initial cost of the pumping equipment over the service life, making good well maintenance a key factor in overall system reliability and efficiency.

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Section 1B Groundwater & Wells

GRUNDFOS ENGINEERING MANUAL

1C WATER QUALITY & TREATMENT Drinking Water Regulation

As directed by the SDWA, the U.S. Environmental Protection Agency (USEPA) developed primary and secondary drinking water regulations designed to protect public health and welfare. The National Primary Drinking Water Regulations (NPDWR) cover contaminants that have adverse effects on human health. These regulations are most enforced by the State or the USEPA. The Secondary Drinking Water Regulations cover contaminants that adversely affect the aesthetic quality of drinking water, such as taste odor, and appearance. Contaminants covered by Secondary Regulations do not normally affect health directly. There regulations are intended as guidelines and are not enforceable by USEPA; however, individual states may choose to enforce some or all of the Secondary Regulations. Refer to Table 1-15 for a listing of the secondary standard as applied to a typical ground water supply. National Primary Drinking Water Regulations. The NPDWR are the drinking water regulations that apply to all public water systems in the United States. In order to provide adequate public health the SDWA makes it clear that the owners and operators of public water systems are responsible for ensuring that their systems meet the regulations. To help fulfill this responsible for ensuring that their systems meet the regulations. The SDWA and NPDWR address, five principal areas: • • • • •

Definition of “public water system” Maximum contaminant levels (MCLs) Sampling frequencies Record-keeping requirements Regulatory reporting requirements

The discussion refers only to the USEPA regulations; individual states can adopt more stringent regulations. Most states have “primacy” responsibility under the SDWA with respect to enforcement of regulations and are responsible for their enforcement. A water supplier need only check with the appropriate state agency to learn exactly what regulations apply to the water system. Public Water System. A Public Water System (supply) is defined in the SDWA as those systems that either (1) have 15 or more service connections or (2) regularly serve an average of 25 or more people daily for at least 60 days each year. The NPDWR applies to all public water systems. There are two types of public water systems defined by the NPDWR: Community systems and non-community systems. A community system is one that serves a residential (year-round) population. A non-community system is one that serves intermittent users, such as a campground. Since certain contaminants have adverse health effects only when consumed regularly over a long period of time, the distinction between community and non-community systems is important in determining which contaminants must be monitored to protect public health. As of 1998, there are approximately 59,000 community water systems in the U.S. Maximum Contaminant Levels and Health Effects. Under the SDWA regulations, the USEPA has issued water standards for drinking an established maximum Contaminant Levels (MCLs) for more than 80 contaminants. The standard limit the amount of each substance allowed to be present in drinking water. A process called risk assessment is used to set drinking water quality standards. In developing drinking water standards, USEPA assumes that the average adult drinks 2 liters of water each day throughout a 70-year life span. Section 1C Water Quality & Treatment

1-37

Section 1

Safe Drinking Water Act (SDWA). In 1974, the US congress passed the Safe Drinking Water Act (SDWA, Public law 93-523) establishing a cooperative program among local, state, and federal agencies to help ensure safe drinking water in the United States. Under the SDWA, the primary role of the federal government is to develop national drinking water regulations that will protect public health and welfare. The states are assigned the responsibility of implementing the regulations and monitoring the performance of public water systems. The public water systems themselves are responsible for treating and testing drinking water to ensure that its quality consistently meets the standards set by the regulations.

GRUNDFOS ENGINEERING MANUAL

Section 1

Risks are estimated separately for cancer and non-cancer effects. For cancer effects, a risk assessment estimates a measure of the chances that someone may get cancer because they have been exposed to a drinking contaminant. USEPA generally sets MCLs at levels that will limit an individual’s risk of cancer from that contaminant to between 1 in 10,000 and 1 in 1,000,000 over a lifetime. For non-cancer effects, the risk assessment estimates an exposure level below which no adverse effects are expected to occur. MCLs are set based on known or anticipated adverse human health effects, the ability of various technologies to remove the contaminant, their effects, the ability of various technologies to remove the contaminant, their effectiveness, and cost of treatment. All MCL’s are set at levels that protect public health. The limit for many substances is based on lifetime exposure so, for most potential contaminants, short-term exceedances pose a limited health risk. The exceptions are the standards for coliform bacteria and nitrate, for which exceedances can pose an immediate threat to health. Table 1-12 lists the MCL’s specified in the NPDWR for various contaminants, there potential health effects and typical source of contamination. Public water purveyors will often report water supply quality data periodically as general mineral, general physical, inorganic & organtic chemicals (pesticides and volatile organics). Table 1-11 lists a typical summary presentation of general mineral, general physical and organic constituents. Table 1-11 lists a typical summary presentation of organic contaminants, radioactivity and microbiology quality. Monitoring & Reporting Requirements. To ensure that drinking water meets the standards set by the SDWA. USEPA has established pollutant specific minimum testing schedules for public water systems. Table 1-11 shows the major groups of contaminants and the minimum frequency that public water systems must test. If a problem is detected, there are immediate retesting requirements that go into effect and strict instructions for how the system informs the public about the problem. Until the system can reliably demonstrate that it is free of problems, the retesting is continued. Refer to the appropriate water quality regulatory agency having jurisdiction for reporting requirements. Table 1-11: Typical Monitoring Schedule

Contaminant Acute Contaminants Bacteria Protozoa and Viruses Nitrate Chronic Contaminants Volatile Organics (e.g., benzene) Synthetic Organics (e.g., pesticides) Inorganics/Metals Lead and Copper Radionuclides

Minimum Monitoring Frequency Monthly or quarterly, depending on system size and type Monthly monitoring for turbidity and total coliforms, as indicators Annually Ground water systems, annually for 2 consecutive years; surface water systems annually Larger systems, twice in 3 years; smaller systems, once in 3 years Ground water systems once every 3 years; surface water systems, annually Annually Once every 4 year

Note: General requirements may differ slightly based on the size or type of drinking water system. Source: USEPA - A consumer’s guide to the Nation’s Drinking Water

1-38

Section 1C Water Quality & Treatment

GRUNDFOS ENGINEERING MANUAL

Record keeping. The SDWA requires record keeping for compliance. In addition to the compliance requirement, records are useful in evaluating system performance, planning improvements and writing reports. Records must be maintained and stored for specific time periods, as established by the NPDWR. Storage periods range from 3 to 10 years pending record type and category. Regulatory Reporting Requirements. To ensure that prompt attention is given to potential health problems, the NPDWR require water systems to submit routine reports to the appropriate regulatory agency. The regulatory agency is most often the State; however in some states the USEPA has primary responsibility for implementing the SDWA.

Section 1

There are three types of reports that must be sent to the state (regulatory agency): • Routine sample reports

• Check sample reports

• Violation reports

Refer to the appropriate water quality regulatory agency for sampling, report frequency and MCL violation reporting. Public Notification. Public Notification is a requirement of the SDWA which requires water suppliers to notify their customers when their system is in violation of the NPDWR. The purpose of the notice is to protect consumers from water that may be temporarily unsafe, as well as to increase public awareness of the problems water systems face and the costs of supplying safe drinking water. Violation notification by mail is sufficient for all cases except violation of an MCL, which requires newspaper and broadcast notice as well. Refer to the appropriate water quality regulatory agency for specific public notification requirements of violations.

Section 1C Water Quality & Treatment

1-39

GRUNDFOS ENGINEERING MANUAL

Table 1-12: National Primary Drinking Water Standards Contaminants

MCLG (mg/L)

MCL (mg/L)

Potential Health Effects from Ingestion of Water

Sources of Contaminant in Drinking Water

Fluoride

4.0

4.0

Skeletal & Dental Fluorosis

Nat.l deposits; fertilizer, aluminum industries; water additive

Benzene Carbon Tetrachloride

0 0

0.005 0.005

Cancer Cancer

Some foods; gas, drugs, pesticide; paint, plastic industries Solvents and their degradation process

p-Dichlorobenzene 1,2-Dichlorobenzene 1,1- Dichlorobenzene

0.075 0 0.007

0.075 0.005 0.007

Cancer Cancer Cancer

Room and water deodorants, and “mothballs” Leaded gasoline, fumigants, paints Plastics, dyes, perfumes, paints

Trichloroethylene 1,1,1-Trichloroethane

0 0.2

0.005 0.2

Cancer Liver, nervous system effects

Textiles, adhesives and metal degreasers Adhesives, aerosols, textiles, paints, inks, metal degreasers May leach from PVC pipe; formed by solvent break down

Vinyl Chloride

0

0.002

Cancer

Section 1

Volatile Organics

Coliform & Surface Water Treatment Giardia Lamblia Legionella

0 N/A

TT TT

Gastroenteric disease Legionnaire’s disease

Human and animal fecal waste Natural waters; can grow in water heating system

Standard Plate Count Total Coliform* Turbidity

N/A 0 N/A

TT 10um)

0 7MFL

0.006 7MFL

Cancer Cancer

Fire retardants, ceramics, electronics, fireworks, solder Natural deposits; asbestos cement in water systems

Barium* Beryllium Cadmium*

2 0.004 0.005

2 0.004 0.005

Circulatory system effects Bone, lung damage Kidney effects

Natural deposits; pigments, epoxy sealants, spent coal Electrical, aerospace, defence industries Galvanized pipe corrosion: natural deposits, batteries, paint

Chromium* (total) Cyanide Mercury* (inorganic)

0.1 0.2 0.002

0.1 0.2 0.002

Liver, kidney, circulatory disorders Thyroid, nervous system damage Kidney, nervous system disorders

Natural deposits; mining, electroplating, pigments Electroplating, steel, plastics, mining, fertilizer Crop runoff, natural deposits, batteries, electrical switches

Nitrate*

10

10

Methemoglobulinemia

Nitrite Selenium*

1 0.05

1 0.05

Methemoglobulinemia Liver damage

Animal waste, fertilizer, natural deposits, septic tanks, sewage Same as nitrate; rapidly converted to nitrate Natural deposits; mining, smelting, coal/oil combustion

Thallium

0.0005

0.002

Kidney, liver, brain, intestinal

Electronics, drugs, alloys, glass

Acrylamide Adipate Alachlor

0 0.4 0

TT 0.4 0.002

Cancer, nervous system effects Decreased body weight Cancer

Polymers used in sewage/wastewater treatment Synthetic rubber, food packaging, cosmetics Runoff from herbicide on corn, soybeans, other crops

Atrazine Carbofuran Chlordane*

0.003 0.04 0

0.003 0.04 0.002

Mammary gland tumors Nervous, reproductive system effects Cancer

Runoff from use as herbicide on corn and non-cropland Soil fumigant on corn and cotton; restricted in some areas Leaching from soil treatment for termites

Chlorobenzene Dalapon

0.1 0.2

0.1 0.2

Nervous system and liver effects Liver and kidney effects

Dibromochloropropane

0

0.0002

Cancer

Waste solvent from metal degreasing processes Herbicide on orchards, beans, coffee, lawns, road/railways Soil fumigant on soybeans, cotton, pineapple, orchards

Dichlorobenzene

0.6

0.6

Liver, kidney, blood cell damage

1,2-Dichloroethylene trans-1,2 Dichloroethylene Dichloromethane

0.07 0.1 0

0.07 0.1 0.005

Liver, kidney, nervous, circulatory Liver, kidney, nervous, circulatory Cancer

Paints, engine cleaning compounds, dyes, chemical wastes Waste industrial extraction solvents Waste industrial extraction solvents Paint stripper, metal degreaser, propellant, extraction

1,2-Dichloropropane Dinoseb Dioxin

0 0.007 0

0.005 0.007 3EE-8

Liver, kidney effects, cancer Thyroid, reproductive organ damage Cancer

Soil fumigant; waste industrial solvents Runoff of herbicide from crop and non-crop applications Chemical production by-product, impurity in herbicides

Inorganics

Organics

1-40

Section 1C Water Quality & Treatment

GRUNDFOS ENGINEERING MANUAL

Table 1-12: National Primary Drinking Water Standards (continued) MCLG (mg/L)

MCL (mg/L)

Potential Health Effects from Ingestion of Water

Sources of Contaminant in Drinking Water

Diquat 2,4-D Endothall

0.02 0.07 0.1

0.02 0.07 0.1

Liver, kidney, eye effects Liver and kidney damage Liver, kidney, gastrointestinal

Runoff of herbicide on land & aquatic weeds Runoff from herbicide on wheat, corn, rangeland, lawns Herbicides on crops, land/aquatic weeds; rapidly degraded

Endrin Epichlorohydrin Ethylbenzene

0.002 0 0.7

0.002 TT 0.7

Liver, kidney, heart damage Cancer Liver, kidney, nervous system

Pesticide on insects, rodents, birds, restricted since 1980 Water treatment chemicals, waste epoxy resins, coatings Gasoline, insecticides, chemical manufacturing wastes

Ethylene Dibromide Glyphosate Heptachlor

0 0.7 0

0.00005 0.7 0.0004

Cancer Liver, kidney damage Cancer

Leaded gasoline additives, leaching of soil fumigant Herbicide on grasses, weeds, brush Leaching of insecticides for termites, very few crops

Heptachlor Epoxide 0 Hexachlorobenzene 0 Hexachloro-cyclopentadiene 0.05

0.0002 0.001 0.05

Cancer Cancer Kidney, stomach damage

Biodegration of heptachlor Pesticide production waste by-product Pesticide production intermediate

Lindane Methoxchlor Oxamyl (Vydate)

0.0002 0.04 0.2

0.0002 0.04 0.2

Liver, kidney, nerve, immune, circ. Growth, liver, kidney, nerve effects Kidney damage

Insecticide on cattle, lumber, gardens, restricted 1983 Insecticide for fruits, vegetables, alfalfa, livestock, pets Insecticide on apples, potatoes, tomatoes

PAHs (Benzo(a)pyrene) PCBs Pentachlorophenol

0 0 0

0.0002 0.0005 0.001

Cancer Cancer Liver and kidney effects, cancer

Coal tar coatings, burning org. matter, volcanos, fossil fuel Coolant oils from electrical transformers, plasticizers Wood preservatives, herbacide, cooling tower wastes

Phthalate (di(2-ethylexyl)) Picloram Simazine

0 0.5 0.004

0.006 0.5 0.004

Cancer Kidney, liver damage Cancer

PVC and other plastics Herbicide on broadleaf and woody plants Herbicide on grass sod, some crops, aquatic algae

Styrene Tetrachloroethylene Toluene

0.1 0 1

0.1 0.005 1

Liver, nervous system damage Cancer Liver, kidney, nervous, circ.

Plastics, rubber, resin, drug ind., leachate from landfills Improper disposal of dry cleaning & other solvents Gasoline additive, manufacturing and solvent operations

Toxaphene 2,4,5 - TP 1,2,4 - Trichlorobenzene

0 0.05 0.07

0.003 0.05 0.07

Cancer Liver and kidney damage Liver and kidney damage

Insecticide on cattle, cotton, soybeans, cancelled 1982 Herbicide on crops, golf courses, cancelled 1983 Herbicide production, dye carrier

1,1,2 - Trichloroethane

0.003

0.005

Kidney, liver, nervous system

Xylenes (total)

10

10

Liver, kidney, nervous system

Solvent in rubber, organic products, chemical prod. wastes By-product of gasoline refining, paints, inks, detergents

0 1.3

TT+ TT#

Kidneys, nervous system damage Gastrointestinal irritation

Natural/industrial deposits, plumbiing, solder, brass Natural/industrial deposits, wood preservatives, plumbing

Beta/Photon Emitters Alpha Emitters

0 0

4mrem/yr Cancer 15 pCi/L Cancer

Decay of radionuclides in natural and man-made deposits Decay of radionuclides in natural deposits

Combined Radium 226/228 Arsenic

0 0.05

5 pCi/L 0.05

Bone cancer Skin, nervous system toxicity

Total Trihalomethanes

0

0.10

Cancer

Natural deposits Natural Deposits, Smelters, glass, electronics wastes, orchards Drinking water chlorination by-products

Lead and Copper Lead* Copper Other Interim Standards

Notes: 1. Maximum contaminant level goal (MCLG) is a non-enforceable goal at which no known adverse health effects occur. 2. Maximum contaminant level (MCL) is a federally-enforceable standard. 3. TT-Treatment Technique requirements established in lieu of MCL’s: effective beginning December 1990. 4. MFL = Million Fibers per Liter longer than 10 um. 5. *Contaminants with interim standards which have been changed. 6. + = Less than 5% positive samples. 7. ++ = Action Level 0.015 mg/L. 8. # = Action Level 1.3 mg/L. 9. Source: USAEPA publication EPA 815-K-97-002 (July 1997).

Section 1C Water Quality & Treatment

1-41

Section 1

Contaminants

GRUNDFOS ENGINEERING MANUAL

Section 1

Table 1-13: Typical Ground Water Quality Summary (General Mineral, General Physical & Inorgonic Chemicals)

Parameter/ Units of measurement

Avg. Conc.

Max Conc.

Min Conc.

Allowable Limit

General Mineral pH (Standard Units) Carbonate mg/L Bicarbonate mg/L Chloride mg/L Sulfate mg/L Calcium mg/L Magnesium mg/L Sodium mg/L Copper mg/L Zinc mg/L Iron mg/L Maganese mg/L

7.3