KOC STD

STANDARDS PUBLICATION

KOC RECOMMENDED PRACTICE

FOR DRAINAGE SYSTEMS

-

DESIGN, MATERIALS AND CONSTRUCTION DOC. NO. KOC-C-025

STANDARDS TEAM

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REV.l _IIl--

KUWAIT OIL COMPANY (K.S.C.)

STANDARDS PUBLICATION

KOC RECOMMENDED PRACTICE FOR DRAINAGE SYSTEMS DESIGN, MATERIALS AND CONSTRUCTION DOC. N 0 . KOC-C-025

STAN DARDS TEAM

KOC RECOMMENDED PRACTICE

FOR

DRAINAGE SYSTEMS -

DESIGN, MATERIALS AND CONSTRUCTION

(FORMERLY 015-SH-1004)

ISSUING AUTHORtTY:

STANDARDS TEAM

TABLE OF CONTENTS Page No. FOREWORD

6

SCOPE

7

APPLICATION

7

TERMINOLOGY 3.1 Definitions 3.2 Abbreviations

8 8 10

REFERENCE STANDARDS, CODES AND SPECIFICATIONS 4.1 Conflicts 4.2 List o f Standards and Codes 4.3 KOC Health & Environment Guidelines 4.4 KOC Standard Drawings 4.5 Project Specifications

11 11 11 15 15 15

ENVIRONMENTAL CONDITIONS

16

HEALTH, SAFETY AND ENVIRONMENT

16

BASIC ENGINEERING REQUIREMENTS 7.1 General Considerations 7.2 Basic Drainage Concepts

16 16 17

DESIGN OF DRAINAGE SYSTEMS 8.1 General 8.2 Design Factors Types and Sources of Effluents 8.3 8.4 Effluent Segregation 8.5 Types o f Drainage System Vented Pipe Gravity Drain System 8.6 8.7 Open Channel Gravity Drain System 8.8 Closed Gravity Drain System 8.9 Pumped Drain System 8.10 Pressurized Drain System

18 18 19 19 21 22

DESlGN VOLUMES 9.1 General 9.2 Effluent Volumes 9.3 Rainwater Volumes 9.4 Firewater Volumes 9.5 Sanitary Sewer Volume 9.6 Dike Area Flow Capacity

24 24 24 25 25 26 26

22 22 23 23 24

DRAINAGE LAYOUT WITHIN PROCESS AREAS 10.1 General 10.2 Process Plot Areas 10.3 Entry Points for Effluents 10.4 Drains Crossing Foundations 10.5 Valves 10.6 Manhole Locations 10.7 Surface Water From Process Area 10.8 Sanitary Sewage DRAINAGE LAYOUT OUTSIDE PROCESS AREAS 11.1 General 11.2 Oily Water From Storage Tanks 11.3 Oily Water From Transformer Bays 11.4 Chemical Sewer From Battery Rooms, Laboratory and Chemical Injection Facilities 11.5 Drainage From Dike Areas 11.6 Surface Water From Area Land Drainage 11.7 Drainage From Buildings 11.8 Treatment 11.9 Measurement HYDRAULIC DESIGN 12.1 General 12.2 Gravity Based Drainage Systems 12.3 Closed Drainage Systems 12.4 Pumped Drain System 12.5 Presssurized Drain System DESIGN OF BURlED PIPEWORK 13.1 General Considerations 13.2 Rigid Pipes 13.3 Flexible Pipes 13.4 Road Crossings 13.5 Thermal Expansion 13.6 Load During Testing 13.7 Submerged Pipes 13.8 Settlement DESIGN OF ANCILLARY STRUCTURES 14.1 Manholes 14.2 Gully Traps 14.3 Catch Boxes and Valve Pits 14.4 Clean-outs 14.5 Oily Water Collection Sumps

14.6 Open Channels and Ditches 14.7 Effluent Collection and Neutralization Pits 14.8 Soak-awayPits 14.9 Septic Tanks 14.10 Cesspools 14.11 Evaporation Ponds SELECTION OF PIPE MATERIAL 15.1 General 15.2 Oily and Clean Water Sewer 15.3 Sanitary Sewer 15.4 Chemical Sewer CONSTRUCTlON MATERIALS CONSTRUCTION 17.1 Setting-out 17.2 Excavation 17.3 Installation of Pipes and Fittings 17.4 Manholes 17.5 Backfillling 17.6 Installation of Septic Tanks and Neutralization Pits 17.7 Installation of Soak-away Pits 17.8 Connection of Building Drainage t o Sewer System 17.9 Wastewater Evaporation Ponds TESTS AND RECORDS 18.1 General 18.2 Field Tests 18.3 Test Records PERFORMANCE RECORDS QUALITY CONTROL 20.1 Quality Plan 20.2 Quality Control Engineer QUALITY ASSURANCE DOCUMENTATION 22.1 General 22.2 Deliverables ACKNOWLEDMENT

FOREWORD

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This document "KOC Recommended Practice for Drainage Systems Design, Materials and Construction" {KOC-C-025) is intended t o address the basic requirements of good drainage, generally by gravity flow systems for KOC Plants and Offsite Facilities (Onshore). This KOC Recommended Practice (RP) has been approved by Standards Team in consultation with the Standards Technical Committee for use throughout the corporate engineering and operational functions of Kuwait Oil Company (K.S.C). This RP sets out t o achieve the following objectives: a. To cover the general guidelines of good drainage requirements with a view to provide a safe, reliable and economic system for the collection and transport of effluents and surface water to treatment areas and discharge points. b. To provide the design recommendations and technical inputs in order to develop the intended drainage system for the oil and chemical contaminated effluents and water before the final disposal. c.

To establish relevant design concepts for forming the basis of a detailed design package and project specification to be prepared prior to construction tender.

d. To install reliable, simple to operate and cost effective drainage systems with a view t o satisfy the wide-ranging safety and environmental concerns by meeting the local and KOC Regulations. e. To set out minimum technical requirements to monitor compliance of material, construction and workmanship with a contract. Feedback as well as any comments or suggestions from the application of this RP derived at any stage of conceptual design, engineering, construction, testing, monitoring and rqaintenance are encouraged and should be directed to: The Team Leader Standards (Chairman, Standards Technical Committee) Industrial Services Group, KOC P.O. Box - 9758, Ahmadi 61008 State of Kuwait Task Force Responsible for this RP The preparation of this RP has been entrusted by the Standards Technical Committee (STC) to the Task Force No. (TF-C/O6) comprising of the following members: Mr. Mr. Mr. Mr. Mr. Mr. Mr.

S. Kumar Mohd. Javaid Krishna Kumar Ahmed Al-Fenaini S. Gopakumar Maged Madi Uppara Saibaba

Standards Team Design Team Design Team Export Fac. Proj. Gen. Projects Projects Design HSE Team

- TF Leader /Author - Member - Member - Member - Member - Member - Member

Tel. Tel. Tel. Tel. Tel. Tel. Tel.

No. No. No. No. No. No. No.

61 407 61322 61 15 2 66987 61388 66389 71 8 3 7

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SCOPE This Recommended Practice (RP) provides guidance on the design of general drainage systems, and describes the minimum technical requirements of materi~lsand construction related t o the drainage systems in KOC Plants and Of-'site Facilities (Onshore) within Kuwait. This RP covers the basic requirements of all drainage, which shall be collected and directed, t o one of the following segregated systems: a. Surface Water b. Oily Water c. Chemical d. Savitary e. Waste Water This Rf' does not include the drainage requirements for the following: Closed process drains for oil and gas production (to be regarded as part of process plant pipe-work). b. Offshore platforms. c. Dril!ing and Exploratory well fluid drainage. d. Deep sea discharges. e. Outfall requirements. a.

The content of this RP is intended to be adopted as a design guide to meet the minimum KOC requirements; and should form the basis of a detailed design specification t o be prepared prior to construction tender. The extent of the Work shall be defined clearly on the Project drawings for the intended drainage systems and detailed specifications shall be provided by the Designer 1 Contractor for KOC approval.

APPLICATION The design, materials, construction and workmanship of the drainage systems shall conform t o the requirements of this RP and the reference standards and codes mentioned herein. Any exceptions or deviations from this RP, along with their merits and justific~tions,shall be brought t o the attention of KOC Controlling Team for their review, consideration and amendment by Standards Team (if required). Compliance with this RP does not of itself confer immunity from legal or statutory obligations.

TERMINOLOGY Definitions For the purposes of this RP, the following definitions apply. Adverse Environmental Impact That causes serious harm t o human, vegetation, natural flora and fauna, marine life or wildlife, or contaminates soil, groundwater / sea water which would make the surrounding area unsuitable for its current or intended use, or would require remedial actions under governing regulations or operating practices. Cesspools Covered watertight tanks used for receiving and storing sewage from premises which cannot be connected to a plant or public sewer, and where ground conditions prevent the use of a small sewage treatment works includir g septic tanks.

Used in conveyance systems t o facilitate inspection and maintenance of drainage systems that cannot be entered by personnel and are not scheduled for frequent inspection and maintenance. Contaminants Any physical, chemical, biological, or radiological substance or matter that changes the naturally occurring make-up of the environment, when disposed off unlreated; and may generally include crude, condensate, chlorides, gasoline, acids, solvents, additives, sanitary and other harmful wastes. Designer Person or persons from KOC or from Contractor or any Consulting firm approved by KOC, who are undertaking the responsibilities of the actual design and detailed specifications, related t o the drainage systems at the KOC Plants and Offsite Facilities. Effluents A discharge of waste material in the form of liquids or liquids mixed with solids irlto the environment, partially or completely treated or in their natural state.

Fluid T:-eatment Center (FTC) Tempo-ary ponds for holding effluents and then recycling for further use or disposal. Good Drainage

A network of open and / or closed system for conveying surface runoff, underground water, produced water and other products or effluents t o discharge safely from areas or plants and facilities without contaminating or flooding into natural watercourses or soil. Manhole Chamber with a removable cover used in conveyance systems to facilitate inspection and maintenance of the drainage pipe, by permitting entry of the personnel. Oily Water System

A sepa-ate drainage system t o carry contaminated water frequently mixed with hydrocarbons from sources such as process drains, laboratory sinks, tank water draws, pump base drains, and manifolds etc. Permeability Hydraulic property (conductivity) of a medium (soil) as a measure of its ability / capacity t o transmit fluids (water etc.) or gases within its interconnected pore network by gravity. Sanitary Sewage System

A separate / segregated drainage system for handling and disposing of sanitary wastes from toilets, bathrooms and kitchens etc. Screening

A mechanical process, which accomplishes a division of particles on the basis c f sizes by accepting or removing relatively coarse floating and suspended solids by straining through a screening surface. Segregated Drainage System

A network of collection and conveying system(s), which keep certain wastes and reactive chemicals, separate from others in the effluents for further processing and disposal.

DOC.NO. KOC-C-025

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Self-cleansing Ability of the flow in a drain or sewer to carry away solid particles, which would otherwise be deposited in the channel or pipe. Septic Tank A type of settlement tank in which the sludge is retained for sufficient time for the organic matter to undergo anaerobic decomposition i.e. bacterial action in the absence of dissolved oxygen. Sewer Pipeline or other construction, usually underground, designed to carry wastewater and / or surface water from more than one source. Storm Water System Separate drainage system(s) for disposal of surface runoff, being either mainly clean rainwater from areas away from tanks and process facilities, free from hydrocarbon or other chemicals, or rain water contaminated with fire water and wash down water containing other liquids from drips or spills. Surcharge Flow condition in which waste water and / or surface water is held under pressure within a gravity drain or sewer system, but does not escape t o the surface t o cause flooding. Waste Water System Separate drainage system(s) dedicated t o dispose off all other types of foul water, 2ontaminated with process fluids, acids, solvents, hydrocarbons or sanitary wastewater. Abbreviations EPA (K1V) EPA (USA) EWTP FTC GRE GRP HDPE HSE

Environment Public Authority Environmental Protection Agency Effluent Water Treatment Plant Fluid Treatment Center Glass Reinforced Epoxy Glass Reinforced Plastics High Density Polyethylene Health, Safety and Environment

KOC PVC QA/QC RTRP UPVC

Kuwait Oil Company (K.S.C) Plasticized Polyvinyl Chloride Quality Assurance / Quality Control Reinforced Thermo resin Plastics Un-plasticized Polyvinyl Chloride

REFERENCE STANDARDS, CODES AND SPECIFICATIONS Conflicts In the event o f conflicts between this RP and the standards / codes referenzed herein, or other contractual requirements, the most stringent requirement shall apply. In case further clarifications are required, the subject shall be brought t o the attention o f KOC Controlling Team.

List of Standards and Codes The latsst edition o f the following standards, codes and specifications shall apply: Nationsl / International Standards API 5 L

Specification for Line Pipe

API 15 LR

Specification for Low Pressure Fiberglass Line Pipe and Fittings

API 15 HR

Specification for High Pressure Fiberglass Line Pipe and Fittings

ASME 1331.3

Process Piping

ASME H31.4

Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

ASME B31.8

Gas Transmission and Distribution Piping Systems

ASTM A 5 3

Specification for Pipe, Steel, Black and Hot-Dipped, ZincCoated, Welded and Seamless

A S T M A ? 53

Specification for Zinc Coating (Hot-Dip) o n Iron and Steel Hardware

A S T M C? 50

Specification for Portland Cement

A S T M I31556

Test Method for Density and Unit Weight o f Soil in place b y the Sand Cone Method

DOC. NO. KOC-C-025

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r

ASTM 015 5 7

Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Efforts

ASTM D3921

Standard Test Method for Oil and Grease and Petroleum Hydrocarbons in Water Vitrified Clay Pipes, Fittings and Ducts, Also Flexible Mechanical Joints for Use Solely with Surface Water Pipes and Fittings

8 s 534

Steel Pipes, Joints and Specials for Water and Sewage

BS 1 2 4 7 Part 1

Galvanized Ferrous or Stainless Steel Manhole Steps

8 s 3506

Unplasticized PVC Pipes for Industrial purposes

BS 4660

Thermoplastics Ancillary Fittings of Nominal Sizes 1 10 and 1 6 0 for Below Ground Gravity Drainage and Sewerage Ductile Iron Pipes and Fittings Propylene Copolymer Pressure Pipe Glass Reinforced Plastics (GRP) Pipes, Joints and Fittings for Use for Water Supply or Sewerage Concrete Pipes and Ancillary Concrete Products Part 1: Specification for Un-reinforced and Reinforced Concrete Pipes (Including Jacking Pipes) and Fittings with Flexible Joints Specification for Un-reinforced and Reinforced Part 4: Concrete Inspection Chambers Pre-cast Concrete Pipes and Ancillary Concrete Products Specification for Inspection Chambers and Part 2: Street Gullies Part 200: Specification for Un-reinforced and Reinforced Manholes and Soak-ways of Circular Cross Section Part 230: Specification for Road Gullies and Gully Cover Slabs Code of Practice for Site Investigations Code of Practice for Earthworks

Code of Practice for Design and Installation of Small Sewage Treatment Works and Cesspools Polyethylene Pipes (Type 50) in Metric Diameters for General Purposes Reinforced Plastic Pipes, Fittings and Joints for Process Plants Design of Concrete Structures for Retaining Aqueous Liquids Code of Practice for Pipelines Part 1: Pipelines on Land: General Part 2: Pipelines on Land: Design, Construction and Installation Code of Practice for Protection of Structures against Water from the Ground Structural Use of Concrete Part 1 : Code of Practice for Design and Construction Gully Tops and Manhole Tops for Vehicular and Pedestrian Areas - Design Requirements, Type Testing, Marking, Quality Control Ductile lron Pipes, Fittings, Accessories and Their Joints for Water Pipelines - Requirements and Test Methods Ductile lron Pipes, Fittings, Accessories and Their Joints for Sewerage Applications - Requirements and Test Methods Elastomeric Seals - Materials Requirements for Seals Used in Pipes and Fittings Carrying Gas and Hydrocarbon Fluids Drain and Sewer Systems Outside Buildings Part 1 : Generalities and Definitions Part 2: Performance Requirements Part 4: Hydraulic Design and Environmental Considerations Plastics Piping Systems for Non-Pressure Underground Drainage and Sewerage Un-plasticized Poly (Vinyl Chloride) (PVC-U) Part1 : Specifications for Pipes, Fittings and the System

DOC. NO. KOC-GO25

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Gravity Drainage Systems Inside Buildings Part 1 : General and Performance Requirements Part 2: Sanitary Pipe-work, Layout and Calculation

4.2.2

BS I S 0 4 0 6 5

Thermoplastics Pipes - Universal Wall Thickness Table

NFPA 2 0

Standard for the Installation o f Stationary Pumps

KOC S-tandards KOC-(2-001

KOC Standard for Basic Civil Engineering Design Data

KOC-C-002

KOC Recommended Practice for Engineering Design Basis o f Civil and Structural Work KOC Standard for Geotechnical Investigation (Onshore)

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KOC Standard for Materials and Workmanship Preparation and Earthwork KOC Standard for Concrete Work Construction KOC-C-024 Part 2

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Site

Materials and

KOC Standard for Materials and Workmanship Roadways, Paving and Hard Standing: Part 2 Miscellaneous Works & Rigid Pavement

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KOC Standard for Materials and Workmanship Wail for Storage Tanks

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Bund

KOC Standard for Hazardous Area Classification KOC Standard for Basic Design Data KOC Standard Equipment

for

Fire

Protection

and

Safety

KOC Recommended Practice for RTRP Pipes and Fittings Part 1 : Materials Part 2: Engineering Design and Installation KOC Standard for HDPE Pipes and Fittings Part 1 : Materials Part 2: Engineering Design and Installation KOC Standard for External Coating of Pipelines, Parts 1-8

KOC-P-005

KOC Standard for Internal Coating o f Pipelines

KOC Fire & Safety Regulations

4.3

KOC Health & Environment Guidelines KOC

-

KOC

- 213 0

2100

KOC - 2 1 6 0

4.4

4.5

Guideline for Evaporation Pits Guideline for Spill Prevention Ministry o f Oil Regulations

KOC Standard D r a w i n q s 1 5-1 -22

Standard Pipe Culvert

15-4-14

Typical Details o f Shallow Manholes

15-4-2?

Standard Gullies

1 5-4-28

Typical Manholes for Drain Pipes

15-5-7'

Standard Septic Tank

15-14-' 0

Standard Valve Pit for Pipe Lines

15-25-'

Standard Soak-away Details

1 5-30-'113

Oil and Gas System Standard Drain Pit Details

15-39-28

Oil Drain Pond, Waste Water Disposal Pond and Tank Bund Details

15-39-30

Standard Manholes Details for Sanitary Systems

15-39-31

Standard Soak-away Pit

Praiect Specifications This RP makes also reference t o other specifications, which should be designated b y the Controlling Team in KOC, in absence o f any Standard IRP for the subjects listed as below: a. Pipirg Material Classes b. Cathodic Protection Design Requirements

c. P r o j e . 3 ~Quality Assurance and Quality Control Requirements

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ENVIRONMENTAL CONDITIONS Refer t o KOC Standard for "Basic Design Data" IKOC-G-007), which provides the detailed design information regarding the environmental, site and utility supply conditions prevailing throughout the KOC facilities.

HEALTH, SAFETY AND ENVIRONMENT The ergineering design should meet all the applicable Kuwait EPA Regulations and should conform t o the KOC Health and Environment (H&E) guidelinss with a view t o protecting its personnel and surrounding environment. All relevant safety requirements of KOC Fire & Safety Regulations and KOC Health, Safety and Environment Management System (HSEMS) shall be adhered to, by the designer / contractor, while designing the drainage systems for the Plant and Offsite Facilities within KOC areas. Permits are essential prior t o fieldwork within hazardous areas in compliance with "KOC Standard for Hazardous Area classification" (KOC-G-002) and KOC Fire and Safety Regulations in any KOC facilities.

BASIC ENGINEERING REQUIREMENTS General Considerations Prior t o commencing preliminary design activities on drainage work for any new or existing KOC Plant, Offsite and / or Field Facilities, the Site should be thoroughly surveyed t o establish its natural topography including surrounding areas; and shall be assessed for the basic requirements to provide a reliable, economic and simple to operate drainage system for the collecticm and transport of all effluents and surface runoff t o treatment areas and discharge points for safe disposal. Due regard should also be given t o the effect of effluent(s) beyond the point of discharge with respect t o quality and quantities of the effluent(s) and contaminated water t o meet the regulations as mentioned in clause 6.0 of this RP. As a measure t o prevent the unwarranted pollution of natural water bodies by harmful substances in quantity or concentration in water, the quality of discharged water should meet the requirements given in Table I of this RP in compliaxe with Kuwait Ministry of Oil Regulations. The overall system should be provided as simple as possible in terms of construction, operation and maintenance, usually by means of open or closed systems as required; and gravity based open system should be considel-ed for wastewater effluents where permitted.

Table I -Water Pollution - Requirements for Qualitv of Discharqed Water (As per Kuwait Ministrv of Oil RequlationslKOC-2160)

//

1

2 3

1 Sulfides (as H,S) Hydrocarbons (Oil)

2 5 mg / litre

4 5 6

Free Available Chlorine Mercury Lead

0.6 m g / litre

7 8 9

Phenol Phos~hates Chromium (Total)

0.05 pprn 5 ma / litre 0 . 5 rng / litre

10 11

Copper Nickel

1 .5 rng / litre 0.5 mg / litre

12 13

Iron Suspended Solids

0.5 rng / litre 25 mg / litre

14

C3issolved Solids (Total)

1 0 0 0 mg / litre

15

k

1 5 mg / litre

Biological Oxygen Demand (BOO) at 5 day 6- p~ value

-1 I

0.01 mg / litre 0.5 m g / litre

I

1 0 mg / litre 6.5 -8.5

The drainage system should be kept free as practicable from the unnecessary mixing of water, oils and chemicals; and every effort should be made t o minimize the waste by suitable provisions of mechanical means such as slop tanks, screens and local separators etc. before entering into the drains. The drainage system shall be developed, by taking into consideration the actual ground conditions and subsurface data from the latest soil investigation report, where available. Otherwise, a soil exploration program shall be conducted at various locations in accordance with KOC-C-003 "KOC Standard for Geo-technical Investigation (Onshore)" t o determine the general soil properties and specific characteristics (porositylpermeability/corrosivity/electrical resistivity etc.) of the soil required for proper working of the drainage systems. Basic Drainage C o n c e ~ t s

Drainage system for any Plant / Facility involved in the handling, processing and storing of hydrocarbons and other chemicals becomes an important part of both fire and environment protection; and should satisfy the growing concerrrs of health, safety and environment related issues within Kuwait.

A good drainage system should consider the following basic concepts in the layout and early design phase as below: Route flammable fluids away from ignition sources and into closed drains; and should isolate also flammable vapours in drainage piping from ignition sources. Route burning liquids away from equipment that might rupture and add fuel t o the flames. It also minimizes exposure of adjacent property. Drain off rainwater quickly and prevent flooding from outside sources. Minimize air emissions from evaporation of volatile fluids by capturing them in closed drains. Kee3 wastes out of soil, groundwater, and surface water. Seg-egate clean and contaminated water to reduce the amount of water t o be treated. Develop catchments, in case of emergency t o prevent flow towards the Plants or Facilities. Need little maintenance. Surface drainage should route contaminated water and wastes into an undergr~unddrainage system that take those liquids t o a treatment facility if necessary. Where there is no potential for contamination 1 pollution, liquids c:an drain into open basins or sumps for later release or treatment. Natural ground slopes shall be utilized as much as possible t o minimize the depths of sewer or channels. DESIGN OF DRAINAGE SYSTEMS General. Normall-q a network of suitable drainage systems should be selected at the early stage of design, assessing all the sources and characteristics of effluents to be present, the estimated rates and volumes of flow, the maximum temperatures, including possible contaminations and chemical reactions of the effluents generated. The system should also take into account the basic requirements as described in clause 7.0 of this RP. Efforts should be made t o segregate clean and contaminated water on the basis of effluent types and degree of segregation required inside and outside the process areas and offsite prior to disposal.

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8.2

Desiqn Factors

8.2.1

When planning a suitable drainage system, the Designer 1 Contractor should take in:o account many process and site specific design factors, and should assess the following technical and financial aspects of the proposed system t o be effective as below: a. The nature and quantity of effluents to be conveyed. b. The safety of proposed system in relation to the effluents and the site. c. The segregation requirements of the effluents, d. Design life of the proposed system. e. Costs related t o construction, operation and maintenance. f.

Compliance with local, environmental and safety regulations.

g. Topography of the site. h. Method of construction. i.

Material, jointing method, size, length and depth of pipe-work.

j.

C o ~ d i t i o nof existing services.

k.

Location of existing buildings and services t o be connected or modified.

I.

Secondary containment requirements (catchments, lining etc.).

m. Site ground conditions that may affect the method of installation and materials of construction and consequent increase in the cost. n. Ground contamination (soil & groundwater). o.

Nature and quantity of additives for chemical treatment of effluents

8.3

Tvpes and Sources of Effluents

8.3.1

Clean Water The system should deal with surface water that is clean and uncontaminated under normal conditions; and can generally be collected as rainwater from building roofs, roadways, access-ways, paved and surfaced areas. I t can be discharged from the Site without further treatment.

. KOC-C-025 8.3.2

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Contaminated Water The system should deal with surface water from areas liable to be contaminated from the following sources: a. Rurl-off from the contaminated paved areas. b. Use of hoses for wash-down and fire fighting in contaminated areas. c. Laboratory wastes.

8.3.3

Oily Water The system should deal with water contaminated with varying degrees of oil that may be originated from the following sources; and should be diverted to the closed drain after collection. Drainage from pipe trenches. Spillages and leaks from process equipment (valves, pumps, etc.). Dralnage from sample points, level gauges, drain cocks etc. Wayer from transformer bays. Pump stations, meter-proving stations and pipe manifolds, roof drains from floating storage tanks, bottom drains (water draw-off) from crude storage tanks. Wa'.er cuts from separators. Kncckout drums drainage. Wash water from Desalters.

8.3.4

Chemicals, Solvents and Other Process Fluids The system should deal with discharges of these effluents t o be regulated generally as part of production process, and should be referred to P&l diagrams for details. The chemical sewer system should collect effluents from the following: a. Battery rooms. b. Laboratory sinks. c.

Chemical Injection Facilities.

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Sanitary Sewage The system should deal with the sanitary waste that shal I be collected from the fol:owing: a. All sanitary, washroom and toilet facilities. b. Kitchens, eating room and cleaners' sinks. c. Building floor drains (except where oily and chemical spills may occur) d. Laboratory sinks and floor drains (except where oily and chemical spills may occur). e. Condensate drains from HVAC equipment, provided all necessary precautions against contamination from the sewer has been built into the system. Waste Water The system should be dedicated t o dispose off all other types of foul water, contaminated with process fluids, acids, solvents, hydrocarbons or sanitary wastewater by evaporation and percolation in the ground, if permitted, or should be treated in the treatment plant as necessary before final disposal. Effluent Seqreqation The effluents should be segregated as practicable t o achieve the optimum number and types of systems that shall be specified in relation to the capacity, ancillary structures, fittings and materials in accordance with the particular requirements of that effluent. The waste treatment facility should also be effluent specific, thereby more reliable and cost effective. The degree of effluent segregation will depend on the following factors as below. System specification t o attain the desired levels of integrity and treatment. Reaztions (physical/chemical/biological) between effluents t o restrict the amount of intermixing. Treatment necessary t o achieve the effectiveness of the treatment process.

process

goals

with

the

Flow rates with a minimum velocity t o prevent silting and blocking in the drainage pipes. Treated effluents.

T v ~ e sof Drainaqe System Depending on the basic requirements of drainage system t o be provided for the effluents discharge and surface runoff from the KOC plants and facilities and the desired levels of meeting the local environmental and safety regulations, the drainage systems should be as below: a. Open Gravity Drainage Systems. b. Closed Drainage Systems. Open Gravity Drainage Systems can be provided as one of the following: a.

Verrted Pipe Gravity Drain System.

b. Open Channel Gravity Drain System. Closed Drainage Systems shall be considered due t o legislation or safety reasons t o restrict gaseous emissions t o atmosphere from open gravity drainage systems. Process information should be used t o identify which effluent streams shouid also be closed. Closed Drainage Systems can be provided as one of the following: a.

Clo::ed Gravity Drain System.

b. Pumped Drain System. c.

Pre:;surized Drain System.

Vented Pipe Gravitv Drain System In this system, the effluent flows in pipes laid t o suitable gradients between manholss, which shall be vented; and the manhole inlets shall be trapped to prevent the spread of fire when the effluent system contains flammable gases cr liquids. Vents shall be provided to maintain atmospheric pressure in each section of pipe, avoiding pressure locks developing in the system. Gullies shall also be trapped and vapours expelled from the system should be kept to the minimum.

Open Channel Gravitv Drain Svstem In this :system, the effluent flows in open channels or drains normally lined, and laic t o fatls or level. The channels / drains shall be trapped, wherever necessary, t o prevent spread of fire.

Closed Gravity Drain Svstem This system shall be configured as a conventional gravity system with sealed access manholes and with a gas vent collecting system. The materials and construction techniques to be used shall be of higher integrity than with open gravity drain systems. Joints shall generally be welded and tested -10 higher standards. Connections t o the drainage system shall be airtight at process units, tanks and dikes etc. and bends shall be used instead of manholes at changes of gradient and direction. Pipe sizes shall be changed by using flat backed tapers and connections from laterals to the main sewer line shall be by branches or flat tees. To ease cleaning of the system, rodding points (clean outs) shall be provided at minimum 50 m intervals in the form of a 'Y' branch on the sewer pipe with the branch pointing upwards and extended to a suitable access point.

Pumped Drain Svstem Pumped drain system shall be closest t o the normal process lines and may be run below or above ground. Two (2) types of pumped drain system may be considered in the drainage design: a. Effluent lift stations t o lift flow from one gravity system and deliver to a second similar system. Such stations should contain only short lengths of pressurized pumping main local t o the lift station. b. Pumping stations with associated pumping mains t o lift and deliver to a distsnt treatment facility. Such systems shall have long lengths of pressurized pumping main, normally located above ground but if necessary can be buried. The main components of pumped drain system should comprise the followir g: a.

Localized gravity system feeding to the lift / pumping station sump.

b. The effluent lift / pumping station. c.

A pvessurized pumping main.

Pressurized Drain Svstem In the pressurized drain system, the effluents flow under gravity but without the access manholes and without conventional vents. The vapour space above the liquid flow shall be sufficient enough t o allow displacement of gases above the liquid level. This space shall then be filled with an inert gas at .ow positive pressure. The inert gas shall be injected at discreet points in this system to prevent accumulation of hazardous vapours. Venting of the inert vapour mixed gas shall be provided at a controlled vent facility, where the gases shall be removed for treatment. Connections t o the drains in this system shall be airtight by providing pressure reducing and isolating valves. These connections shall generally be made above ground for ease of access. Bends, pipe size changes, connections to laterals and rodding points shall be simi ar to the closed gravity system as specified in clause 8.7 of this RP. DESIGN VOLUMES Genera! The intended systems draining paved and / or unpaved areas shall be designed for the greater volume of the either cases as follows: a. Casz 1: Effluent volume b. Case 2: Effluent volume

+ Rainwater volume, + Firewater volume.

or

Effluent Volumes Effluent volumes shall be determined from process information or standard tables; and usually flow continuously in limited quantities from process plants and non-plant / offsite facilities. Effluents including all dry-weather flows shall run through the drainage systems, which shall not be allowed t o flood the adjoining areas for adverse environrnental impact. However when the effluent is mixed with surface runoff, the volumes generated from rain and firewater should be assessed with adequate margins to be built in the drainage systems for future development.

DOC. NO. KOC-C-02

REV.l

Page 25 of 65

-

Rainwater Volumes Rainwater volumes shall be derived from the rainfall intensity as specified in "KOC Standard for Basic Design Data" (KOC-G-007), t o assess surface runoff frorn the areas using the appropriate permeability factors given in Table II of this RP. Table 11: Permeabilitv Factors

I 2

3 4

I Roofs 1 Paved Areas (Concrete or Tarmac) Gatched Areas Gravelled Areas

I

0 0

I

0 0.2

0.9

-

0.8 5

The contributing areas for rainfall drainage to the sewers shall be considered t o be 1 0 0 % of the paved area. However, the contribution of runoff -from unpaved areas should be considered on a case-by-case basis using the relevant permeability factors as given in Table II of this RP. Firewater Volumes In case of emergency, the fire water runoff t o be generated from a dike area of storage tanks or from a part of process unit t o contain and control fire shall be in accordance with the appiication rates of water and other fire fighting facilities as specified in the relevant KOC Standards in clause 4.2.2 of this I3P. Normally as a guide, the total firewater demand for hydrocarbon related installa1:ions having a fire risk should be as per NFPA 20, or more if the risk levels are high or process requirements demand for higher protection. However, it should generally vary between 800 m3/hr and 2 0 0 0 m3/hr and usually an average of 1 3 6 0 m3/hrshould be considered adequate. Firewater should not cause spread of fire by flowing into the adjacent areas, and should be directed as fast as possible into the drainage system and / or to areas where the water can cause no harm. The drainage system should be assumed for design purposes that water will be applied as follows: a.

1 0 0 % evenly distributed over the whole of the process area; or

b. 7 0 % evenly distributed over an area of 1 0 0 0 within the process area.

rn2 located anywhere

-

DOC. NO. KOC-C-025

1

I Page

26 o f 65

L

REV.l

Firewater Losses Some losses should be considered between the firewater being applied and the wa-ter being entering the drainage system due t o over-spray, evaporation and percolation into the surrounding ground; and they will be influenced by factors such as climatic conditions, ground type, duration of water applica-tion & application type and structure types. They should be assessed on a case-by-case basis. Sanitarv Sewer Volume The anticipated flow in sanitary sewers shall be based on the Probability Data and Discharge Unit System in accordance with BS EN 7 5 2 Parts 1-4. In addkion, the daily volume of sewage shall be calculated on the basis of 135 litre / person / shift, with ten (10) person per shift of work. Due allowance shal! be made for future expansion and development of the area in designing the capacity of sewers. Dike AI ea Flow Capacity The flow capacity of drainage system in a diked tank area shall take into consideration the greater flow rate of the following conditions as below: a.

Dr~inageof all accumulated rainwater within the dike in less than four (4) hours.

b.

Continuous drainage of firewater used for cooling purposes.

The tank base should not become submerged in both cases. DRAINAGE LAYOUT WITHIN PROCESS AREAS General When .:he plant layout is being finalized, the drainage systems should be configured at the same time as a part of Site development. The impact on drainage systems of future developments in plant and wastewater treatment facilities should also be considered. Surface drainage in process areas must route surface liquids away from equipment and into underground drainage systems. Uncontaminated surface runoff :;hould enter storm water rather than process sewers. Main drain lines should run along the edges of plant areas and roads wherever possible, t o minimize the impact of future drainage work on the operational areas.

All oily water within process area shall have dedicated drainage system and shall be treated as part of the process system. Process Plot Areas Process plot areas shall be provided with concrete paving as necessary to meet the requirements of drainage and/or access t o equipment(s), buildings and maintenance areas in accordance with clause 12.0 "Paving and Access-ways" of KOC Recommended Practice for Engineering Design Basis of Civil and Structural Work (KOC-C-002). Process plot areas should be divided into catchments, draining to manhole / gully around the process equipment so that any leakage and / or spilled of liquids should be directed towards the drainage points. The catchments should also drain in a fire incident to prevent the spread of firewater and / or flammable liquids to unaffected areas. Within process plot areas, paving should be generally laid t o falls sloping with a gradient 1 in 100 (1 %) t o the drainage points. Bituminous paving wherever provided, should have minimum slopes not less than 1 in 6 0 t o ensure adequate drainage without ponding. Around pumps and other areas where leaks and spills are anticipated, the minimun slope should be increased t o 1 in 5 0 (2%) for quicker draining from the area. The use of kerbing / bunding, minimum 1 0 0 m m high should be considered around the perimeter of the catchments and around sensitive process units or group of equipment t o separate leaked / spilled effluents and contain firewater flow carrying them further. However, care should be taken in the layout to avoid any trip hazards or obstructions to safe and convenient access paths for vehicles and people. Entry Points for Effluents Effluents should enter into the drain system through four f4) main types of collection points as below: a. Manhole Gullies b. Gul y Traps c. Turdishes d. Ch~nnels All marhole gullies, gully traps and tundishes shall be provided with rodding points.

Manhole Gullies a. Where rainwater and / or firewater are t o be drained from paved areas, combined manhole gully shall be provided in the centre of each catchment area for greater capacity; and that should act as a simpler sysF:em than a number of smaller gullies leading t o a trapped manhole. b.

Refer t o clause 14.1 -9 of this RP for details of combined manhole gull es.

Gully Trap Connections a.

Where lower volumes of effluent are t o be collected, individual trapped gullies should be used.

b. Gullies within process plot limits should generally be connected by indi-~iduallines from each to a manhole, which shall be trapped on entry to t i e manhole. Process Drain Connections a. Process drain connections should be provided through tundishes. b. Collector drains and branches may be used, if several process drains conrlect t o the underground drain system at the same or closely a d j ~ c e n tlocations. In such cases the collector drain shall be connected direct t o a manhole, and trapped on entry. Drainage Channels a.

In case large volumes of water are t o be conveyed, drainage channels shall generally be used.

b. When the risk of fire spreading due to flammable liquids and vapours is minimal, a combined drainage system may be appropriate. Drains Crossinq Foundations Drains shall not be laid below or through structural foundations. The drainagz system and foundations shall be designed in such a way that drains can be laid above the upper surface of any foundation, which they cross. Precautions should be taken to allow for any differential settlement where drains are t o be laid in soft or unsupported ground outside the foundations.

Valves Valves should be installed into open and closed systems t o isolate sections of p i p ~ ( s ) .Where located underground, they shall be mounted in suitable valve pits made of concrete. Underground valves that are required frequently t o operate manually shall be providsd with extended spindles t o avoid entry into the valve pit. Manhole Locations Manhole locations should be established at an early stage in initial layout design, which will allow vents t o discharge in safe area with the minimum length of underground vent pipe. Generally, manholes should not be located in access-ways within process units o* where crane outriggers may be placed. When located outside or on the edge of process units, they should be, wherever possible, at least 5 m (16 ft) away from the edge of any road. However as guidance, manholes on sewers and drains shall be provided as below: a.

At changes in pipe direction in vertical and horizontal planes.

b. At a maximum spacing of 25 m for sewers less than 9 0 0 mm ( 3 6 in.) pipe diameter, where solids may be present. c.

At a maximum spacing of 100 m for sewers of diameter greater than 900 m m ( 3 6 in.), or where no solids are present.

d.

A t a junction with incoming pipes, that does not have cleaning access w i t i n 1 0 m.

e.

A t changes of main sewer diameter.

f.

A t :lead of runs.

Surface Water From Process Area Clean and uncontaminated surface water under normal conditions as described in clause 8.3.1 of this RP shall be collected and discharged to the clean water drainage system. The system may be provided either simply as the graded areas located outside the Facility boundary, by grading to falls onto the surrounding areas; or as the holding basins at a designated location outside the Facility.

-

DOC. NO. KOGC-025

I

Page 30 of 6 5

REV.l

Clean water may also be piped from the collecting manholes; and then be discharged to the swales constructed outside the Facility for further disposal. Sanitarv Sewaqe The sanitary sewage collected from the sources (buildings etc. in the process areas) shall be handled and discharged through U-PVC pipes t o the septic -:anks or to the cesspools as described in clauses 14.9 or 14.10 and 15.3 of this RP. Sanitary sewers shall not be installed in the proximity of potable water lines less than the following separation distances as below: a.

Vertical

b. Lateral

-

- Minimum 300

m m below the potable water line.

Minimum 900 m m horizontally from the potable water line.

DRAINAGE LAYOUT OUTSIDE PROCESS AREAS General Drainace outside process plot area limits but including from offsite areas and field facilities should be collected and directed into the following segregated systems as described below. Disposal of the effluents from these areas should meet the requirements of KOC HSE and / or Kuwait EPA as given in clause 6.0 of this RP. No discharge point from any collected drainage, be it natural or from any other sources, should be directed onto / into any drilling location or drilling site reserve pit(s), e,g. final effluent soak-away from sewage treatment system in field areas. Oily Water From Storaqe Tanks All the water draw-off from the oil storage tanks shall be drained / piped to a common collecting sump (drain pit) that shall be located by the side of the tank with vehicular access-way. This drain line from the collecting sump shall be provided with a shut-off valve adjacent t o the sump, which will be normally closed except when draining oily water under control from the area. Oily water drained through the oily water drain piping shall be routed to the oily water separator at the tank farm or effluent water treatment plant (EWTP); and the separated oil shall then be pumped back t o the oil storage tank. T3e water from the separator shall be drained to a wastewater pond or ground disposal.

The oily water separator shall have high / low detection device linked to the on / off action of oil transfer pump t o maintain an optimum level in the separa1:or. The top level@) of any sump walls shall be made sufficiently high from ground t o prevent any rainwater within the dike from flooding into the sumps during periods of heavy rain. If there are areas within the diked area which are heavily contaminated with oil drips under valves and manifolds, they should be paved and connected to the oily water system, instead of the clean water system. Oilv Water From Transformer Bavs Generally drainage from transformer bays will be t o the oily water system via a trapped gully. Where transformer bays are remote from an oily water sewer, discharge may be to a clean sewer through a trapped gully and normally closed valve.

A collecting sump shall be provided so that operatork) may inspect the effluent before release t o the clean sewer. The requirement of oily water drainage can be waived, if a roof is provided over the transformer bay(s) and a sump is used t o collect intermittent spills, which can then be pumped out. Chemical Sewer From Battery Rooms, Laboratorv and Chemical lniection Facilities Wastes from battery rooms, laboratory sinks and chemical injection facilities should be routed through the chemical sewer system to a neutralization sump; and the neutralized effluent shall then be drained t o the sanitary sewer or to a soak-away pit. Soak-away pit shall be made in accordance with KOC Standard drawings 15-25-1 and 15-39-31

.

Chemicals from the injection facilities shall be routed to a sump through a drain piping. This sump shall have provisions for being drained through either vacuum tanker or pumping system as specified. Drainaqe From Dike Areas Storm water (rain) drainage and / or firewater used in dike areas for cooling around tanks containing crude oils and oily products, shall be collected in one or more reinforced concrete catch boxes located at the internal toe of the dike walls as remote from the tank as practicable.

The run-off shall be directed t o the catch boxes by grading the surrounding ground away from the tank with the slopes as specified in "KOC Standard for Layout, Spacing and Diking of Aboveground Petroleum Storage Tanks" (KOC-L-027). The effluent shall be drained through a minimum 3 0 0 m m (12-inch) diameter carbon steel pipe, under the dike wall to a gate valve, that shall be normally closed and kept inside a dike outlet valve pit. The valve pit shall be of reinforced concrete construction and should be locatec; outside the dike wall in a readily accessible location. The discharge from the gate valve shall be visible to contamination.

detect any

Flow from the dike outlet valve pit shall be routed through a valve outlet to an impounding basin located outside the facility boundary at a KOC approvl3d location. The impounding basin when provided shall meet the requirements as specified in KOC-L-027. Contaminated effluent shall not be discharged into the surface water system. The location of valve pits shall, therefore be selected adjacent to access roads to facilitate removal of any contaminated effluent by road tankers. Surface Water From Area Land Drainaqe Rainwater falling on unpaved uncontaminated ground outside process plot areas should normally be disposed off by natural percolation into the subsoil and evaporation. Where the natural percolation is not sufficiently effective without undue ponding due to subsoil characteristics (impermeable or less permeable) of the surrounding land, the surface should be graded to suitably located trapped gullies discharging t o a buried pipe system. Where this is not practicable, land drains should be provided.

11.7

Drainaqe From Buildinqs

11.7.1

Plant Buildings a.

Floor drains in plant buildings such as pump or compressor houses shall be connected t o fully trapped and vented manholes when they form part of a system draining oily or chemically contaminated water.

b. Adequate precautions shall also be taken to eliminate any possible ingress of hazardous gases entering building from the drainage system. 11.7.2

Control Buildings a.

No drains shall be permitted within control rooms of any control buildings.

b. In other areas of control buildings, electric substations and switchgear rooms, the appropriate drainage systems for sewage wastewater shall be provided.

1 1.7.3

c.

Sanitary flows shalt be discharged into a septic tank and design of t r e ~ t m e n units t shall be in accordance with BS 6297.

d.

Septic tanks shall be located outside the facility fence but not less than 15 m from manned buildings, with due regard t o wind direction and vehicular access for periodic removal of sludge.

Laboratory Drainage a. To maintain control over waste disposal, laboratory collection points s h o ~ l dbe used. b.

1 1.7.4

Uncontaminated waste wastewater system.

liquids

can

be

drained

to

the

sewage

Other Buildings a. Normally, other buildings can be connected to the sewage wastewater sysl:em, when only domestic type wastes are being drained. Canteen wastes shall be connected via a grease trap. b. In case of isolated buildings, disposal by septic tank and subsoil irrigation s h o ~ l dbe preferred, subject to there being no possibility of polluting underground potable water. c.

Cesspools may be used as an acceptable alternative.

DOC. NO. KOC-C-025

I

Page 34 of 65

REV.1

Treatment Effluen-t Treatment Plants Effluene:s containing oily and chemical waste should be treated as necessary t o meet KOC HSE requirements; and the treated outflow should satisfy also the Kuwait EPA Regulations prior t o discharge, disposal or injection. Fluid Treatment Centers (FTC) Effluenl:~, if permitted, may be discharged temporarily to the fluid treatment centers such as lined ponds for evaporation and treatment for further recycle and / or disposal. Holding Basins Holding basins may be provided, if necessary to capture and retain some part of rainfall or firewater from paved areas in order t o avoid flooding the adjoining areas due t o ground conditions. Wastewater Evaporation Ponds a. Wastewater where it is necessary to dispose off by evaporation and / or soakage shall be discharged t o the designated ponds. These ponds should be located outside the boundary of the KOC Facility and shall be made by gradivg and diking the required areas. b. However, the location should not cause any potential contamination to any iearby fresh water aquifer. In that case, consideration should be given t o alternate site or other appropriate measures to prevent it. c. The evaporation pond shall meet the other requirements as given in KOC Guideline No. 21 00 and satisfy the Kuwait EPA Regulations. Sewage Treatment a.

All means of sewage handling and treatment should conform t o the State Public Health requirements.

b. The drainage should preferably be discharged t o the nearest sewer (KOC / S-tate) where available. But if this is not practicable, biological treatment may be considered and septic tanks or cesspools shall be provided for isolated or remote buildings.

Measurement A simple weir or monitoring device to measure the effluent discharge rate should be installed at or near the final effluent discharge point.

DOC. NO. KOC-C-025 12.0

HYDRAULIC DESIGN

12.1

General

Page 35 of 65

12.1 -1 Drainage systems in most cases shall be provided as gravity based open systems in compliance with clause 8.5.2 of this RP. Occasionally for process reasons, closed drainage system may be more appropriate because of tech7ical, safety or environmental requirements. However, the design methods and criteria for both open and closed systems are closely related. 12.1 - 2 Gases or vapours that may be carried forward with the effluent or evolved during the course of treatment may affect the flow regime of the system. 12.1.3

Hydraulic design should consider the following factors as below: a. b. c. d.

Recommended maximum and minimum velocities and flows. Sediment transport capacity. Degree of surcharge, or controlled flooding within tolerable limits. Intended hydraulic capacity which requires selection of pipe size, gradient and condition, nature of liquid to be carried and vapour pressure likely to develop in the system.

12.2

Gravity Based Drainaqe Systems

12.2.1

Flow in pipes and channels shall be evaluated using the standard design methods (i.e. Rational Area Method or Modified Manning's Equation) employing simple hand calculations or approved software for designing the system. Due allowance shall also be made for roughness factors of piping and / or channel bed materials, and the effect of pipe joints on the flow regime.

12.2.2

Drainage sewers shall be designed in open and / or closed gravity systems assuming a maximum flow depth of 70% of pipe diameter, and operating at or near t o atmospheric pressure. The minimum flow depth shall not be less than 30 m m for pipes likely t o transport solids.

12.2.3

Drainage sewers shalt be designed to be dry under no flow conditions.

12i2.4

Flow Velocities a.

Velocities shall be kept within a range that prevents damage t o the pipes and fittings and should be self-cleansing as much as possibie; and in case of open channels, they should neither deposit excessive silts nor scour the bed channels.

DOC. NO. KOC-C-025

Page 36 of 65

REV.l 4

b. Pipe runs should be designed to accommodate the maximum expected flow when running just full. For some lengths of drain the flow from emergency use of fire hoses may exceed the normal process and rainwater flows. 12.2.5

mini mu^ Velocity a. All ~ i p e ddrains shall be designed to attain a minimum velocity of 0.75 m/s either from process flows alone, or from combined process and rainwater flows to achieve periodic cleansing of the drains. b. In oily water drains, the minimum velocity should be about 0.9 m/s to limit, both silting and emulsion.

12.2.6

12.2.7

Maximem Velocity a.

The maximum velocity shall not exceed 2.5 m/s t o avoid high friction losses and thereby more head-losses.

b.

In cily water systems, the maximum velocity under normal operating condition shall not exceed 1.20 m/s to prevent emulsification.

Design 'Jelocity The design velocity from combined process and rainwater flows shall be about 1.0 m/s; however velocities from firewater or emergency flows may exceed this.

12.2.8

Open Channels a.

All channels in fine sands or silts shall be lined with concrete or asphalt t o prevent erosion.

b. In case of unlined open channels, the velocity should be kept sufficiently low t o prevent scouring. This velocity should be selected as per local soil conditions and construction; and may be in the ranges between 0.5m/s t o 0.75 m/s. c. Where the velocity is likely t o be higher than 0.75 m/s around bends, concrete or asphalt lining shall be provided t o prevent scouring of the bed or sides. 12.2.9

Siltation a. The drainage system shall be free from ingress of any solids as much as possible; but should be capable of carrying them with minimum maintenance effort.

b. Where minimum velocities for periodic cleansing of the system cannot be abtained through process or rainwater flows, flushing facilities should be installed t o provide a flow of 0.75 mls in each pipe run of the system. c.

Where lengths of drainage sewer are designed t o be permanently flooded for hydraulic reasons or for safety reasons, the design flows should be increased by 1 0 % as an allowance for siltation.

d.

Fine solid particulate matters such as silt or clay particles from storm wacer runoff on unpaved areas should be prevented wherever possible frorn entering into oily water drains.

12.2.10 Surcharging and Flooding a.

Surcharging of the drains may be considered in open gravity systems only, for emergency conditions or high rainfall in order to ensure sufficient hydraulic capacity, provided that surface flooding should not be increased thereby.

b.

Under these maximum flow conditions, the hydraulic gradient within the drainage system can extend no higher than 3 0 0 m m below any point of entry into the system.

c.

If there be a risk of flooding, each drainage catchment area should be ass3ssed using an accepted risk assessment technique.

d.

In those cases where some flooding can be acceptable, any sensitive areas should be diked or kerbed, and the water directed away by using paving falls.

12.2.1 1 Roughness Factors a.

In assessing the frictional head-loss of the effluents flowing in the drains, roughness factors (k,) shall be selected on the basis of likely mature condition of the pipes Ichannels with due regard t o the materials of c:onstruction and the nature of the effluents drained.

b. As guidance, the roughness factors (k,) may be used in calculating the flow rate as follows:

-

-

3.01 3 for 3.01 2 for 0.01 4 for 3.020 for 3.030 for

Steel, Concrete, Cement-lined and Vitrified Clay Pipes. Plastic Pipes. Concrete lined channels. Channels with earth, straight and uniform. Channels with earth having some vegetation.

-

DOC. NO. KOC-C-025

REV.l

All likely head losses due to bends, enlargements and contractions of open channel / pipes as well as pipe connections to tanks and equipment(s) including valves, fittings and accessories, and at manholes should be duly considered into the hydraulic design of the drainage systems. For details refer t o standard design handbook for hydraulic str ~ c t u r e s . 12.2.13 Corrosion a.

External corrosion on the metallic pipe materials due to adverse effects of soil / ground water and internal corrosion due to effluents or contaminated water shall be properly accounted in the pipe materials thickness as necessary in conformity with the design practices.

b.

Corrosion allowance shall be considered minimum 1.5 mm or more as specified by KOC in the designated project specification for material classes of metallic pipes.

c.

Appropriate coating / lining of external and internal surfaces of metallic pipss shall be decided as per KOC Standards in clause 4.2.2 of this RP; and should be provided as applicable. Suitably designed cathodic protection system shall be installed t o prevent or minimize further, the deterioration by corrosion.

12.2.1 4 Recommended Gradients for Pipe Laying a. Trench excavation should generally be limited t o 6 m depths because of construction difficulties and associated high cost, especially where water tables are found to be high. b. Pipes should be laid as per the recommended minimum gradients given in Table II! of this RP. Table Ill:Recommended Minimum Gradients

1.

!l 'I

.