Report of Drilling Results-Wlenchiti BH02

 

 

WELENCHITI TOWN WATER SUPPLY AND SANITATION PROJECT

 

 _____

WATER WELL DRILLING FOR THE WATER SUPPLY OF WELENCHITI TOWN & SATELLITE VILLAGE (DENGORO TIYO)   WELENCHITI TOWN BOREHOLE NO.2 DRILLING RESULTS REPORT

Client: 

Oromia Water, Energy & Mineral Resources Development Bureau   Contractor : GTB Engineering in JV with EMU General Importer PLC and TAM Geo-Engineering PLC Supervisor: A Consortium of Salomon and YGRY Consulting Engineers PLC March 2017

TAM GEO-ENGINEERING PLC. Tel. 251-(0)911211792 (0)911517411/12 P.O.Box 4661, e-mail [email protected] e-mail  [email protected] 

 

Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

Table of Contents EXECUTI EXE CUTIVE VE SUMMARY SUMMARY .............................................................................................. 1  1 

GENERA GEN ERAL L BACKGRO BACKGROUND UND................................................................................... 3 

1.1 

DESCRIPTION OF THE WORK AREA ........................................................................ 3 

 

 

GEOLOGY  ............................................................................................................ 5 1.2 2  DRILLI DRI LLING NG RESULT RESULTS S ............................................................................................. 6 

2.1  DRILLED GEOLOGICAL FORMATION ..................................................................... 6  2.1.1  Well Casings and Screens Screens ............................................................................... 7   2.2  TEST PUMPING ..................................................................................................... 8  2.2.1  Test Pumping Pumping of Welenchiti Welenchiti BH-02.................................................................. 8  2.2.2   Provisional Test Pumping of Welenchiti BH-02 ............. ...... ............. ............ ............ ........... ........... ........... ..... 8  2.2.3  Step Drawdown Drawdown Test of Welenchiti Welenchiti BH-02 ....................................................... 8  2.2.4  Constant Discharge Test of Welenchiti BH-02 ............................................... 11  2.2.5   Recommended pumping rate of Welenchiti BH-01 Alternative ............ ...... ............ ........... ..... 15  2.2.6   Water quality of Welenchiti Welenchiti BH-02 ................................................................17   3 

 

CONCLUSION AND RECOMMENDATION CONCLUSION RECOMMENDATION............ ...... ............ ............. ............. ........... ........... ............ ............ ...... 20 3.1  CONCLUSION ..................................................................................................... 20  3.2  R ECOMMENDATION ECOMMENDATION............................................................................................ 21  List of Tables T  ABLE 0:1.SUMMARY OF TEST DRILLING RESULTS  ......................................................................................................1  T  ABLE 0:2. SUMMARY OF PUMP TEST RESULT   ...........................................................................................................1  T  ABLE 1:1. LOCATION OF W ELENCHITI ELENCHITI T OWN OWN & DENGORO T IYO IYO S ATELLITE VILLAGE BOREHOLES   ..........................................3  T  ABLE 2:1. F ORMATIONS ORMATIONS DRILLED AT W ELENCHITI ELENCHITI BH02  ............................................................................................6  T  ABLE 2:2. SUMMARY OF W ELL ELL C ONSTRUCTION ONSTRUCTION FOR W ELENCHITI ELENCHITI BH02  .......................................................................7  T  ABLE 2:3  W ELENCHITI ELENCHITI BH02 SUMMARY OF STEP TEST RESULT ....................................................................................9 ....................................................................................9   T  ABLE 2:4. STEP DRAWDOWN TEST RESULT W ELENCHITI ELENCHITI BH02 ............ ............. ............. ............. ............. ............. .... 10  T  ABLE 2:5 S UMMARY OF C ONSTANT ONSTANT T EST EST RESULT OF W ELENCHITI ELENCHITI BH02 ..................................................................... 15  T  ABLE 2:6 E  XTRAPOLATED PUMPING RATE OF W ELENCHITI ELENCHITI BH02BASED ON STEP TEST RESULT  ...........................................  ........................................... 16  T  ABLE 3:1.SUMMARY OF TEST DRILLING RESULTS AT W ELENCHITI ELENCHITI BH02 ............ ............. ............. ............. ............. ...... 20  T  ABLE 3:2. W ELENCHITI BH02 S ELENCHITI   UMMARY OF PUMP TEST RESULT   ............................................................................... 20 

List of Figures F IGURE IGURE 1. LOCATION OF W ELENCHITI ELENCHITI & DENGORO T IYO IYO BOREHOLES  .............................................................................4  F IGURE IGURE 2. W ELENCHITI ELENCHITI BH02 STEP DRAWDOWN TEST RESULT   .....................................................................................9  3  )   ........................ ............ ............. ........... 10  F IGURE -DOWN ( M ) VERSUS DISCHARGE ( M  / DAY  DAY  IGURE 3. W ELENCHITI ELENCHITI BH02 DRAW -D F IGURE IGURE 4. W ELENCHITI ELENCHITI BH02 H ANTUSH-BIERSCHENK W ELL ELL LOSS  .............................................................................. 11  F IGURE IGURE 5. W ELENCHITI ELENCHITI BH02 SEMI-LOGARITHMIC TIME DRAWDOWN PLOT OF CONSTANT DISCHARGE TEST ............ ............ ............. .. 12  F IGURE IGURE 6. W ELENCHITI ELENCHITI BH02 LOGARITHMIC TIME DRAWDOWN PLOT OF CONSTANT DISCHARGE TEST  ............... ............. ...... 12  F IGURE IGURE 7. W ELENCHITI ELENCHITI BH02 SEMI-LOGARITHMIC TIME -RECOVERY PLOT OF CONSTANT DISCHARGE TEST ............. ............. ............. .... 13  F IGURE IGURE 8. W ELENCHITI ELENCHITI BH02 RESULTS FROM C OOPER OOPER J ACOB T IME IME DRAWDOWN METHOD ................................................ 14  F IGURE IGURE 9. W ELENCHITI ELENCHITI BH02 RESULTS FROM T HEIS HEIS RECOVERY ANALYSIS METHOD  ............. ............. ............. ............. ............. ...... 14  F IGURE IGURE 10. W ELENCHITI ELENCHITI BH02 W ELL ELL DEPTH V S PUMPING RATE . DEPTH TO W   ATER LEVEL FOR DIFFERENT PUMPING RATES ....... 16  IGURE 11. EC  CHANGE  CHANGE WITH PUMP TEST TIME FOR THE GROUNDWATER OF W ELENCHITI ELENCHITI BH02 .............. .............. ............ 17  F IGURE Tel. 251-(0)911211792 251-(0)911517411-(0)911517412, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

F IGURE IGURE 12. PH & TEMPERATURE CHANGES WITH PUMP TEST TIME FOR THE GROUNDWATER OF W ELENCHITI ELENCHITI BH02 ... ............. 18 18  F IGURE IGURE 11. PIPER DIAGRAM FOR THE GROUNDWATER OF W ELENCHITI ELENCHITI BH02 ............. ............. ............ .............. ............ 19  F IGURE IGURE 14. SCHOELLER DIAGRAM FOR THE GROUNDWATER OF W ELENCHITI ELENCHITI BH02.......................................................... 19 

APPENDICES APPENDIX A  –  –  PROFILE  PROFILE OF WELLS COMPLETED WITH CASING APPENDIX B  –  –  TEST  TEST PUMPING DATA APPENDIX

C   –   WATER

QUALITY

ANALYSIS

LABORATORY

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RESULT

 

Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

EXECUTIVE SUMMARY

The Welenchiti Town Water Supply and Sanitation Project included drilling and test  pumping of o f four boreholes, for Welenchiti Town (three boreholes) & Dengoro Tiy T iyo o (one Borehole) in Oromia Regional State in the Federal Democratic Republic of Ethiopia. Welenchiti BH01 Alternative was drilled as part of o f this program. Welenchiti BH01 Alternative the drilling commenced on January 14 th  2017 and th

completed at a depth of 252m on March 18  2017. The borehole is drilled to a depth of 252 m. The well was drilled with a diameter of 17 ½ inches for surface casing and 14 ¼ inches diameter for the main drilling. Steel surface casing of 14 inches diameter installed to a depth of 6 m and the annular space is grouted with cement. In this well production casings of mild steel casings and screens with 7mm wall thickness with inner diameter 203mm are installed. The annular space has been packed with gravel from 145m up to 252 and the top part filled with clay and grouted with cement. Table 0:1.Summary of test drilling Results BH No 

Drilled Depth (m) 

Casing Depth (m) 

Inner Casing Dia. (mm)

BH02

252

252

203

Screen position st

nd

rd

1  

2  

3  

4th

169m 169m –   –  175.14m

180.86m 180.86m –   –  186.64m

215.3m –  215.3m –  209.52m

232.46m - 249.8m

The aquifer used for production in this well is mainly the fractured and weathered basalts and sand deposits. The test pumping result shows that the wells has good yield. BH02 is pumped with discharge rate of 11.0 l/s for 72 hours and the resulting drawdown was 10.85m. The 2

aquifer has Transmissivity Transmissivity values of about 174 17 4 m /day. Table 0:2. Summary of pump test result

BH No

Constant test (l/s)

Test Duration (hrs)

SWL (m)

DWL (m)

BH01

11.0

72

103.6

114.45

Draw Down (m) 10.85

Specific capacity (m2/day) 87

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Transmissivity (m2/day) 174

 

Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

The fluoride content (2.76 mg/l) of the groundwater from this well is higher than the maximum allowable limit (1.5mg/l). All other analyzed chemicals are within the allowable limits of the WHO and the Ethiopian Standard Agency Age ncy guidelines. The fluoride concentration in the water supply can be reduced by mixing proportionally the groundwater from this well with the nearby wells. Based on the pumping test analysis result and the well construction this well can be pumped up to 15 l/s with pump position  between 160m and 165m. However, the pumping rate from this well depends on the  pumping from the t he nearby wells to reduce the concentration of the fluoride content. co ntent. The temperature of the water is less than 38 oC, thus cold-water submersible pumps with operating temperature range of up to 40 oC recommended.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

1 

Water well Drilling Results Report

GENERAL BACKGROUND

Wlenchiti Town Water Supply and Sanitation Project included drilling of 4 boreholes (three boreholes for Welenchiti Town and one borehole for Dengoro Tiyo Satellite village). The major scope of work included drilling with 17 ½ inch diameter for installation of 14 inches surface casing, drilling with 12 ¼ inch diameter and installation of 8 inches uPVC casings & screens, gravel packing, development and testing in accordance to the specification. However, as a result of difficulties encountered in installation of uPVC casing in 12 ¼ inch diameter, 8 inches mild steel casing was installed for Welenchiti BH02. This report includes the drilling results for Welenchiti th

BH02. At this borehole the drilling commenced on January 14  2017 and completed at a th

depth of 252m on March 18  2017. 1.1

Description of the work area

The drilling sites are situated in Oromia Region East Shewa Zone around Welenchiti Town. Welenchiti Town is located at about 120km from Addis Ababa, whereas the drilling sites are situated 5 km south west (before) Welenchiti town by the right side of the main highway. The area is situated within the Awash River catchment within the Main Ethiopian Rift Valley. The location of the boreholes is shown on the following table and the map in figure 1. Table 1:1. Location of Welenchiti Town & Dengoro Tiyo Satellite village Boreholes BH No Coordinate (WGS84) Altitude (m) Wlenchiti BH01 Alternative 1459 (WTBH-01Alt) 545884 955018 Wlenchiti BH02 (WTBH-02) Wlenchiti New BH02 (WTBH-02New) Wlenchiti BH03 Dengoro Tiyo BH04a Dengoro Tiyo BH04b (DTBH-04b)

546255 544997

954669 955055

1460 1459

Not Drilled

546115 545930 544227

954121 953650 954143

1462 14 62 1464 1461

Not drilled Drilled but not used

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Water well Drilling Results Report

 Figure 1. Location of Welenchiti Welenchiti & Dengoro Tiyo B Boreholes oreholes

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

1.2

Water well Drilling Results Report

Geology

Welenchiti is situated in the Main Ethiopian Rift Valley on an alluvial plain with basalt flows and spatter cones bounded from the east by Dino Formation Volcanics and from the west by the Nazareth Series. The alluvial sediment is of quaternary to recent in age and composed of alluvial and lacustrine deposits, sands, silts and clays. Dino Formation is Pleistocene in age composed of Ignimbrites, tuffs, coarse pumice, water lain  pyroclastic deposits and with rare intercalations of lacustrine deposits. depo sits. Nazareth Series is mainly composed of mildly alkaline basalts with subordinate alkaline and peralkaline silicics. Quaternary Rhyolite volcanic centres with obsidian, pumice, ignimbrite and trachyte flows also occur in plains. The drilling for the groundwater of Welenchiti and Dengoro Tiyo has targeted the

alluvial and lacustrine deposits for lower values of fluoride content as it was observed from the result of the test well. At Welenchiti BH02, the drilling encountered the alluvial and lacustrine sediment at the top 162m and followed by volcanic deposits and layers of alluvial and lacustrine deposits.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

2 

Water well Drilling Results Report

DRILLING RESULTS

The borehole was drilled to a depth of 252 m below ground surface. The top 6m was drilled with 17 ½ inches for installation of 14 inches surface casing. The remaining depth was drilled with 12 ¼ inches diameter. The drilling method was mud circulation throughout the depth. 2.1

Drilled Geological Formation

The major geological formations penetrated are volcanic rocks mainly alluvial and lacustrine deposits, basalt and pyroclastic deposits. There was no drilling problem, except slow drilling in the basalt formation and the loss of o f circulation below 236m depth. Upon completion of the drilling, electrical logging was done using Terrameter SAS-300C

in order to complement the lithological logs. The electrical logging result shows distinct difference in the resistivity of the sediments and fractured volcanic rocks. The following table shows the lithological logging result based on recovered samples and electrical logging. Table 2:1. Formations drilled at Welenchiti BH02 B H02 Geologic Log Depth (m) From

To

0m

2m

2m

4m

4m

6m

6m

12 m

12 m

20 m

Geology

Geologic Descriptio Description n Clay:- Black in colour

Sediment

Clay:- black sandy clay Clay:- brownish clay Pumice:- pumice deposit  Trachyte:-

Volcanic

20 m

22 m

22 m

32 m

Trachyte:-

32 m

60 m

Clay:-

60 m

100 m

Clay:- Sandy clay

100 m

126 m

126 m

144 m

Sand:-

144 m

162 m

Clay:- Brownish clay

162 m

178 m

178 m

180 m

180 m

184 m

184 m

210 m

Sediment

Volcanic

Clay:-

Clay:- Brownish clay

Basalt:- fractured basalt Clay:- Reddish clay

Sediment

Sand:- coarse grained  Clay:- black clay

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

Geologic Log Depth (m)

Geology

Geologic Descriptio Description n

From

To

210 m

214 m

Basalt:- fractured trachy basalt 

214 m

222 m

Clay:- light brown clay 

222 m

230 m

230 m

232 m

Clay:- light brown clay 

232 m

234 m

Basalt:- highly weathered 

234 m

252 m

Sand:-

 2.1.1  2.1. 1

Volcanic

Pumice:- weathered 

Well Casings and Screens

The well was drilled 252 m depth. The up to 252 m it is lined with steel casings and screens with nominal diameter of 8 inches. The screens are slotted with 2-mm slot size. The casing has 217mm outside and 203mm inner diameter with wall thickness of 7mm.

Observation pipe of ¾ inches GS pipe installed up to the depth of 200 m. A steel surface casing of 6 m length and 14 inches diameter installed in the well. Rounded river gravel of basaltic origin has been emplaced in annular space up to 145m  below ground. A total of 7 m3 gravel has been used. After the emplacement of gravel, the well has been developed with compressed air for 12 hours using Ingersoll-Rand (IR) compressor of capacity 25 bar mounted on the rig. The annular space has been grouted for 12m below the ground surface and above the gravel level. Finally a wellhead of 1 m by 1 m by 0.75 m is constructed around the 14 inches surface casing. The details of casing and screen positions are provided in the following table. Table 2:2. Summary of Well Construction for Welenchiti BH02 Item 

From (m)

1.  Drilling

0 6

2.  Steel Surface Casing 3.  8 inches steel 7mm thick Casing installed with outer diameter of 217mm and inner diameter 203mm

To (m)

6 252

+0.8 Blind 6 From (m) To (m)

Total (m)

Diameter in inch

6 246

17 ½ 12 ¼

6.8(m) Total

16 Diameter in inch 

169.36

170.06

8

175

180.86

5.86

8

186.64

209.52

22.88

8

215.3

232.46

17.16

8

249.8

252.8

3

+0.7

Total blind Casing

8

218.96 218.9 6

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

4.  uPVC heavy duty 13mm thick screens installed in stalled

Total Screen Casing 5.  Observation pipe

2.2  2.2.1  2.2. 1

Screen  From (m)   To (m) 

Water well Drilling Results Report

Total (m)

Diameter in inches 

169

175.14

6.14

8 

180.86

186.64

5.78

8 

215.3

209.52

5.78

8 

249.8

232.46

17.34

8

35.04

+0.7

200

¾

Test Pumping Test Pumping of Welenchiti BH-02

The test pumping was conducted between 10/03/2017 and 14/03/2017. It was done o

using 200 KVA generator, 55 KW submersible pumps, 4 inches riser pipe, 90  weir

(V-notch), stopwatch and water level measuring tape (deep-meter). (deep -meter).  2.2.2  2.2. 2

Provisional Test Pumping of Welenchiti BH-02

Before starting the proper pumping test, provisional test was conducted on the well to estimate the well yield, to check the draw down, and to decide on the pump position and the type of pumping test to be conducted. This test was carried out with  11 l/s for one hour with the pump intake situated at 140 m depth below the top of casing, which was 0.5m above ground level. The static water

level at the beginning of the test has been measured 103.8 m from the same reference  point. At the end of the test the pumping level reached 113.27 m.  2.2.3  2.2. 3

Step Drawdown Test of Welenchiti BH-02

Based on the result obtained from provisional pumping test, Step drawdown test was carried out to determine some characteristics of the well such as well performance, well efficiency, specific capacity of the well, to calculate aquifer and well loss and to determine a suitable discharge rate for the constant discharge test. The test was conducted for a total of four hours and consisted of four steps, where each step lasted for one hour. The well was pumped successively with 6.5 l/s, 8.0l/s, 9.5 l/s and 11.0 l/s  by positioning the pump at a depth of o f 140 m below the reference point. The total t otal draw down of the step-wise test was 6.14 m, 7.44 m, 9.08 m and 9.34 m respectively. With the increase of discharge from 6.5 l/s to 9.34 l/s the specific capacity of the well did Tel. 251-(0)911211792 251-(0)911517411-(0)911517412, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

not show any significant decline and rather it increased at 11 l/s. Summary of the step test result is shown on the following table and figure. Table 2:3 Welenchiti BH02 summary summary of step test result result l/s

m3/day

DD

l/s/m

m2/day

SC %

6.5

5 61.6 561.6

6.14

1.06

91.47

100%

8

691.2

7.44

1.08

92.90

102%

9.5

820.8

9.08

1.05

90.40

99%

11

950.4

9.34

1.18

101.76

111%

7.2

m3/day 622.08

DD 3.25

l/s/m 2.22

m2/day 191.41

SC % 100%

8.7

751.68

4.11

2.12

182.89

96%

10.2

881.28

4.92

2.07

179.12

94%

l/s

11.7

1010.88

5.06

2.31

199.78

104%

 Figure 2. Welenchiti BH02 Step Drawdown test result

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 3. Welenchiti BH02 Draw-D  Draw-Down own (m) versus d discharge ischarge (m3 /day)

The step test result is analysed using the following conventional method;  s = BQ + CQ2  Where s Where  s =  = Drawdown 2  B  B =  = Aquifer loss (d/m ( d/m ) C  =  = Well loss coefficient Q = Discharge (m3/d) Well efficiency = 100*BQ / (BQ+CQ2) The result shows that the major drawdown in the well is as a result of the aquifer loss. The results of the step test are shown in the t he following tables and figures. Table 2:4. Step Drawdown test result Welenchiti BH02 Specific Capacity 2 (m /d)

Qn  (l/s)

Qn (m /d)

DD, Sw   (m)

6.5

561.60

6.14

91.47

8

691.20

7.44

9.5

820.80

11

950.40

3

Specific Draw down 2 Sw/Qn (d/m ) 

2

2

2

100*BQn / (BQ+CQn2)

B*Qn

CQn  

Swn = B *Qn + CQn  

2.64E-06

5.13

0.83

5.96

86.03

9.13E-03

2.64E-06

6.31

1.26

7.57

83.34

0.011

9.13E-03

2.64E-06

7.49

1.78

9.27

80.82

0.010

9.13E-03

2.64E-06

8.68

2.38

11.06

78.44

B (d/m )

C

0.011

9.13E-03

92.90

0.011

9.08

90.40

9.34

101.76

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 4. Welenchiti BH02 Hantush-Biersc  Hantush-Bierschenk henk Well Well Loss

 2.2.4  2.2. 4

Constant Discharge Test of Welenchiti BH-02

72 hours constant rate test was carried out at the same pumping position and discharge

rate of  11  11 l/s. The water level at the beginning of the test was 104.19 m. During the pumping period the maximum drawdown attained was 10.26 m. The recovery of the well was fast and 91% recovered within 4 hours duration. The aquifers are situated within the volcanic rock formation such as basalt and sediments mainly sand (probably reworked volcano-clastic deposit). The timedrawdown curve shows semi-confined aquifer characteristic with gradual increase in drawdown.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 5. Welenchiti BH02 Semi-Logarithmic time drawdown plot of constant discharge test

 Figure 6. Welenchiti BH02 Logarithmic time drawdown drawdown plot of constant constant discharge discharge test

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 7. Welenchiti BH02 Semi-Logarithmic time-recovery plot of constant discharge test 2

2

The specific capacity of the well is about 186m /day. The transmissivity (m /day) of the aquifer has been calculated using Cooper-Jacob time-drawdown method and the Theis recovery methods; where, T = 0.183*Q/Δs -------------------- (for Drawdown) T = 0.183*Q/Δs’ ------------------ (for Recovery) 2

Where T  =  = Transmissivity (m /day) 3

Q = Pumping rate (m /day)  Δs =  Δs  = Drawdown difference per log cycle (m) time-drawdown graph  Δs’’ = Drawdown difference per log cycle (m) of recovery graph  Δs In addition the Theis’s analysis method for time-drawdown was used, 2where both have given equivalent results. The transmissivity of the aquifer is about 174m /day. The results are shown on the following figures. The summary of the test result is shown in the following table.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 8. Welenchiti BH02 results from Cooper Jacob Time drawdown method

 Figure 9. Welenchiti BH02 results from Theis Recovery analysis method

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

Table 2:5 Summary Su mmary of Constant Test Result of Welenchiti BH02 Pumping rate (m3/day) Pumping test length (hrs) Static Water Level Below ground (m) Pumping water level (m) Drawdown (m) Specific Capacity (M3/day/m) Transmissivity Transmissivi ty from time drawdown plot (m /d) Transmissivity from 2 recovery (m /d)

constant

rate

163.00

pumping 185.00

Transmissivity Transmissivi ty from step test recovery (m /d) Average transmissivi Average transmissivity ty of aquifer (m /d) Hydraulic Conductivity divided by screen length)

950.4 72 103.6 114.45 10.85 87.59

m/d

174.00

(Transmissivity 5.02

 2.2.5  2.2. 5

Recommended pumping rate of Welenchiti BH-01 Alternative

The well was test pumped for 72 hours at 11.0 l/s and has 10.65 m of drawdown. The static water level before commencement of test was at 103.8 m and dynamic water level for 11.0 l/s pumping was at 114.45m. The screen in this well is deep below 169m depth. Taking into account the pump position at about 160m, there will be an available drawdown of about 56m. Taking into account the step test result along with constant test result and by extrapolating this well can be pumped 15 l/s without any problem. At 15 l/s the estimated drawdown is below 20m, which means, the dynamic water level will be below 124m depth. Thus, from the pumping test analysis it is recommended to pump this well up to 15 l/s with pump position at about 160 and 165m. o

o

The temperature of the water measured at the site range between 32 C and 38 C. The o

normal operating range of cold  owater pumps range up to 40 C, thus cold water pump with temperature range up to 40 C is recommended.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

Table 2:6 Extrapolated pumping rate of Welenchiti BH02based on step test result

Qn (l/s)

Qn  (m3/d)

B (d/m2)

C

S (Drawdown)

CQn2 

BQn 

8.00

691.2

9.13E-03

2.64E-06

6.31

1.26

7.57

9.00

777.6

9.13E-03

2.64E-06

7.10

1.60

8.70

10.00

864

9.13E-03

2.64E-06

7.89

1.97

9.86

11.00

950.4

9.13E-03

2.64E-06

8.68

2.38

11.06

12.00

1036.8

9.13E-03

2.64E-06

9.47

2.84

12.30

13.00

1123.2

9.13E-03

2.64E-06

10.25

3.33

13.59

14.00

1209.6

9.13E-03

2.64E-06

11.04

3.86

14.91

15.00

1296

9.13E-03

2.64E-06

11.83

4.43

16.27

 Figure 10. Welenchiti BH02 Well depth Vs pumping rate. Depth to Water level for different  pumping rates rates

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

 2.2.6  2.2. 6

Water well Drilling Results Report

Water quality of Welenchiti BH-02

For the purpose of checking changes in water quality characteristic the electrical conductivity (EC), pH and temperature and fluoride has been monitored throughout the  pumping test. The EC value range between 960 μS/cm and 506 μS/cm and the o

o

temperature between 38 C and 32 C. The EC value has shown three different ranges within the 72 hours test. The first is up to 18 hours pumping in which the EC value was  between 960 μS/cm and 825  825  μS/cm. After 18 hours of pumping, between 18 hrs and 46 hrs the EC and temperature have shown significant decline. The EC value dec declined lined within the ranges of 675μS/cm and 670 μS/cm and the temperature between 32.2 oC and 33 oC. The third is from 47 hrs up to 72 hours. In this period the EC value declined, but the temperature have shown rising trend. The EC value ranges 506μS/cm and 632 μS/cm

and the temperature between 32. oC and 37 oC. This indicates the presence of aquifers having cold and warm water with different EC values. The pH varies within small range  between pH values of 7. and 7.3.

 Figure 11. EC EC change with with pump test test time for for the grou groundwate ndwaterr of Welenchiti BH02 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 12. pH & temperature changes with with pump test time time for the groundwate groundwaterr of Welenchiti  BH02 

At the end of the test pumping water sample was collected and submitted to the Water Works Design & Supervision Enterprise Laboratory for analysis. The groundwater analysed from BH02 is Na-HCO3 type. Except for fluoride, all the analysed parameters are within the allowable limits of the guideline set by the WHO and the Ethiopian Standard Agency. Agency.

The groundwater has low low TDS (380mg/l), (380mg/l), pH of 7.42 and and low low

hardness (64mg/l). The analysis result of Aluminium, Chromium and boron have values less than 0.1 mg/l. The analysis result has shown that the fluoride content is about 2.76mg/l which is higher than the allowable maximum value of 1.5 mg/l. Thus this water has to be blended with water from the nearby wells with lower fluoride content in order to reduce the fluoride concentration in the water to be supplied.

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

 Figure 13. Piper Piper diagram for the groundwate groundwaterr of Welenchiti BH02 

 Figure 14. Schoeller Schoeller diagram diagram for the the groundwater groundwater of Welenchiti BH02 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

3 

3.1

Water well Drilling Results Report

CONCLUSION AND RECOMMENDATION Conclusion

The depth of the well below ground where casing is installed is 252m. The well has been drilled with a diameter 17 ½ inches (444.5mm) diameter for surface casing and 12 ¼ inches (311.15mm) diameter for the well casing. Well casings and screens are made of mild steel with nominal diameter of 8 inches and wall thickness of 7mm. After installation of casing the annular space has been packed with gravel up to 145 m below ground. The remaining part is filled with clay and the top 12 m grouted with cement. Table 3:1.Summary of test drilling Results at Welenchiti BH02 BH No 

Drilled Depth (m)

Casing Depth (m)

Inner Casing Dia.

Screen position 1st  

2nd 

3rd 

4th

BH02

(m) 

(m) 

252

252

(mm)

203

169m 169m –   –  175.14m

180.86m 180.86m –   –  186.64m

215.3m –  215.3m –  209.52m

232.46m - 249.8m

The aquifer used for production in this well is mainly the fractured and weathered basalts & and sand deposit. The aquifers in the volcanic ash and trachyte are sealed with clay and  blind casing as a result of their higher values of fluoride content. The aquifer situated  below 160m is used for production with screen position position indicted in the above table. The test pumping result shows that the wells has good yield. BH02 is pumped with discharge rate of 11.0 l/s for 72 hours and the resulting drawdown was 10.85m. The 2

aquifer has Transmissivity values of about 174 m /day. The following table shows the summary of test pumping result. Table 3:2. Welenchiti BH02 Summary of pump test result

BH No

Constant test (l/s)

Test Duration (hrs)

SWL (m)

DWL (m)

BH01

11.0

72

103.6

114.45

Draw Down (m)

Specific capacity (m2/day)

10.85

Transmissivity (m2/day)

87

174

The chemical quality of the groundwater for the analysed parameters except its high fluoride content (2.76 mg/l) is within the allowable limits of the WHO and the Ethiopian Standard Agency guidelines.

The groundwater is is Na-HCO3 type.

It has low TDS

(380mg/l), pH of 7.42 and low hardness (64mg/l). The analysis result for Aluminium, Chromium and boron shows that they have values less than 0.1 mg/l. Tel. 251-(0)911211792 251-(0)911517411-(0)911517412, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

3.2

Water well Drilling Results Report

Recommendation

The screen in this well is deep below 169m depth. Taking into account the pump position at about 160m, there will be an available drawdown of about 56m. Combining the constant and the step test results show at 15 l/s the drawdown in this well does not exceed 20m with with dynamic water level of 124m. Thus, from the pumping test analysis analysis it is recommended to pump this well up to 15 l/s with pump position between 160m and 165m. However, the pumping rate has to be decided based on the pumping rates of the nearby wells to be used to reduce the fluoride concentration. o o The temperature of the water from this well ranges between 32 C and 38 C. Thus cold  o

water pumps with operational temperature range of over 38 C are recommended.

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Water well Drilling Results Report

References 1.  Mengesha Tefera, Tadiwos Chernet and Workineh Haro; The Geological Map of

Ethiopia, 2nd edition. Geological Survey of Ethiopia, 1990  2.  Mengesha Tefera, Tadiwos Chernet and Workineh Haro; Explanation of the

Geological Map of Ethiopia, 2  edition. Geological Survey of Ethiopia, 1996   nd

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

APPENDICES

Water well Drilling Results Report

–  PROFILE  PROFILE OF WELLS COMPLETED WITH CASING APPENDIX A  –   TEST PUMPING DATA APPENDIX B  –  –  TEST APPENDIX C  –  –  WATER  WATER QUALITY ANALYSIS LABORATORY RESULT

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Water well Drilling Results Report

–  PROFILE  PROFILE OF WELLS COMPLETED WITH CASING APPENDIX A.  – 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

– PUMPING PUMPING TEST DATA APPENDIX B  – 

Water well Drilling Results Report

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Water well Drilling Results Report

Project Name: Welenchiti Town Water Supply and Sanitation Project  Client:Oromiya Mineral, Water and Energy Bureau Date of Start:- 10/03/2017  Date of Completion:14/03/2017  Site Name: New BH-02 REFERENCES Known Benchmark Data:- X=___________ Y=__________ Z=__________ Top of observation pipe 0.5m  above ground GPS Reading:X= ___________ Y=___________ Z=__________   Step Drawdown Test st n r t 1 2 3   4   Discharge L/s 6.5 Discharge L/s 8 Discharge L/s 9.5 Discharge L/s 11 Water Draw Water Draw Water Draw Water Draw Time Level down Time Level Down Time Level down Time Level Down (Min) 0 0.5 1

(m) 103.6 105.25 105.6

(m)

0.00 1.65 2.00

(min) 60.5 61 61.5

(m) 109.82 109.9 109.95

(m)

6.22 6.30 6.35

(min) 120.5 121 121.5

(m) 111.14 111.23 111.27

(m)

7.54 7.63 7.67

(min) 180.5 181 181.5

(m)

112.69 112.69 112.70

(m)

9.09 9.09 9.10

7 8 9 10 12 14 16 18 20 25 30 35 40 45

105.7 105.9 106 106.07 106.25 106.32 106.54 106.63 106.8 107 107.27 108.4 108.72 108.95 109 109.03 109.15 109.2 109.3 109.42 109.45 109.56 109.56

50 55 60

109.63 109.65 109.74

1.5 2 2.5 3 3.5 4 4.5 5 6

2.10 2.30 2.40 2.47 2.65 2.72 2.94 3.03 3.20 3.40 3.67 4.80 5.12 5.35 5.40 5.43 5.55 5.60 5.70 5.82 5.85 5.96 5.96 6.03 6.05 6.14

62 62.5 63 63.5 64 64.5 65 66 67 68 69 70 72 74 76 78 80 85 90 95 100 105 110

109.99 110.02 110.1 110.13 110.18 110.21 110.27 110.35 110.43 110.5 110.57 110.62 110.63 110.65 110.66 110.7 110.7 110.74 110.8 110.8 110.86 110.89 110.98

115 120

111.02 111.04

6.39 6.42 6.50 6.53 6.58 6.61 6.67 6.75 6.83 6.90 6.97 7.02 7.03 7.05 7.06 7.10 7.10 7.14 7.20 7.20 7.26 7.29 7.38 7.42 7.44

122 122.5 123 123.5 124 124.5 125 126 127 128 129 130 132 134 136 138 140 145 150 155 160 165 170

111.29 111.3 111.35 111.47 111.54 111.6 111.65 111.72 111.81 111.9 111.98 112.06 112.2 112.31 112.4 112.4 112.42 112.47 112.5 112.52 112.55 112.64 112.68

175 180

112.68 112.68

7.69 7.70 7.75 7.88 7.94 8.00 8.05 8.12 8.21 8.30 8.38 8.46 8.60 8.71 8.80 8.80 8.82 8.87 8.90 8.92 8.95 9.04 9.08 9.08 9.08

182 182.5 183 183.5 184 184.5 185 186 187 188 189 190 192 194 196 198 200 205 210 215 220 225 230 235 240

112.71 112.71 112.71 112.72 112.72 112.73 112.74 112.74 112.74

9.11 9.11 9.11 9.12 9.12 9.13 9.14 9.14 9.14

112.75 112.75 112.75 112.76 112.76 112.76 112.78 112.79 112.80 112.85 112.85 112.87 112.89 112.92 112.92 112.94

9.15 9.15 9.15 9.16 9.16 9.16 9.18 9.19 9.20 9.25 9.25 9.27 9.29 9.32 9.32 9.34

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Water well Drilling Results Report

Project Name: Welenchiti Town Water Supply and Sanitation Project  Client:Oromiya Mineral, Water and Energy Bureau Date of Start:- 10/03/2017  Date of Completion:14/03/2017  Site Name: New BH-02 REFERENCES Known Benchmark Data:- X=___________ Y=__________ Z=__________ Top of observation pipe 0.5m 

GPS Reading:-

X= ___________ Y=___________ Z=____________

SWL 104.19 (m) Time Water Level (m) Hour Min

Draw down (m)

Constant Discharge Test Discharge 11.0 (l/s) Time Water Draw Level (m) down (m) Hour Min

Pump Position 140 (m) Time Water Draw Level (m) down Hour Min (m)

0 0.5

104.19 109.80

0.00

35

112.17

7.98

600

113.60

9.41

5.61

40

112.20

8.01

660

113.74

9.55

1

110.40

6.21

45

112.22

8.03

720

113.86

9. 9.67 67

1.5

110.70

6.51

50

112.35

8.16

780

113.86

9.67

2

110.87

6.68

55

112.37

8.18

840

113.86

9. 9.67 67

2.5

111.00

6.81

60

112.44

8.25

900

113.90

9.71

3

111.10

6.91

960

113.93

9. 9.74 74

111.20

7.01

112.47 112.47

8.28

3.5

70 80

8.28

1020

113.93

9.74

4

111.29

7.10

90

112.50

8.31

1080

113.94

9.75

4.5

111.37

7.18

100

112.58

8.39

1140

113.94

9.75

5

111.45

7.26

120

112.65

8.46

1200

113.95

9.76

6 7

111.50 111.59

7.31 7.40

140 160

112.80 112.85

8.61 8.66

1260 1320

114.05 114.05

9.86 9.86

8

111.64

7.45

180

112.93

8.74

1380

114.06

9.87

9

111.69

7.50

210

113.05

8.86

1440

114.08

9.89

10

111.70

7.51

240

113.08

8.89

1500

114.10

9.91

12

111.73

7.54

270

113.10

8.91

1560

114.22

10.03

14

111.79

7.60

300

113.23

9.04

1620

114.22

10.03

16

111.81

7.62

330

113.28

9.09

1680

114.23

10.04

18

111.85

7.66

360

113.33

9.14

1740

114.27

10.08

20

111.90

7.71

420

113.33

9.14

1800

114.31

10.12

25

111.98

7.79

480

113.40

9.21

1860

114.37

10.18

30

112.06

7.87

540

113.54

9.35

1920

114.39

10.20

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

SWL 104.19 (m) Time Water Level (m) Hour Min

Draw down (m)

Constant Discharge Test Discharge 11.0 (l/s) Time Water Level (m) Hour Min

Water well Drilling Results Report

Draw down (m)

1980

114.43

10.24

3300

114.40

10.21

2040

114.45

10.26

3360

114.44

10.25

2100

114.46

10.27

3420

114.43

10.24

2160

114.49

10.30

3480

114.47

10.28

2220

114.49

10.30

3540

114.48

10.29

2280

114.49

10.30

3600

114.52

10.33

2340

114.49

10.30

3660

114.51

10.32

2400

114.49

10.30

3720

114.51

10.32

2460

114.49

10.30

3780

114.52

10.33

2520

114.50

10.31

3840

114.51

10.32

Pump Position 140 (m) Time Water Draw Level down Hour Min (m) (m)

2580

114.50

10.31

3900

114.53

10.34

2640

114.52

10.33

3960

114.52

10.33

2700

114.52

10.33

4020

114.48

10.29

2760

114.52

10.33

4080

114.50

10.31

2820

114.47

10.28

4140

114.49

10.30

2880

114.43

10.24

4200

114.45

10.26

2940

114.55

10.36

4260

114.44

10.25

3000

114.55

10.36

4320

114.45

10.26

3060

114.25

10.06

3120

114.26

10.07

3180

114.30

10.11

3240

114.36

10.17

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Water well Drilling Results Report

Project Name: Welenchiti Town Water Supply and Sanitation Project  Client:Oromiya Mineral, Water and Energy Bureau Date of Start:- 10/03/2017  Date of Completion:14/03/2017  Site Name: New BH-02 REFERENCES Known Benchmark Data:- X=___________ Y=__________ Z=__________ Top of observation pipe 0.5m 

GPS Reading:-

X= ___________ Y=___________ Z=____________

SWL 104.19 (m) Time Time Since since Pumping pumping Stopped (t’) (min) Hour Min

Time Ratio (t/t’) 

Constant Discharge Test Recovery Discharge 11.0 (l/s) Time Time Since Water Residual since Pumping Level Drawdo pumping Stopped (t’) (s) wn (s’)

Pump Position 140 (m) Time Water Residual Ratio Level Drawdown (t/t’)  (s) (m) (s’) (m) 

started (t) (min)

(m)

(m)

0

4320

114.45

57.21

35

4355.0

124

106.71

2.52

0.5

4320.5

111.6

51.10

40

4360.0

109

106.63

2.44

8641

(min) Hour Min

started (t) (min)

1

4321.0

4321

111.1

48.40

45

4365.0

97

105.9

1.71

1.5

4321.5

2881

110.4

47.25

50

4370.0

87

105.85

1.66

2

4322.0

2161

110.39

47.62

55

4375.0

80

105.8

1.61

2.5

4322.5

1729

110.3

47.80

60

4380.0

73

105.76

1.57

3

4323.0

1441

109.59

47.70

70

4390.0

63

105.71

1.52

3.5

4323.5

1235

109.49

47.51

80

4400.0

55

105.62

1.43

4

4324.0

1081

108.55

47.37

90

4410.0

49

105.6

1.41

4.5

4324.5

961

107.67

47.24

100

4420.0

44

105.54

1.35

5

4325.0

865

107.55

47.13

120

4440.0

37

105.43

1.24

6

4326.0

721

107.52

47.00

140

4460.0

32

105.33

1.14

7

4327.0

618

107.59

46.75

160

4480.0

28

105.33

1.14

8

4328.0

541

107.44

46.53

180

4500.0

25

105.29

1.10

9

4329.0

481

107.4

46.32

200

4520.0

23

105.22

1.03

10

4 330.0 4330.0

433

107.37

46.16

220

4540.0

21

105.1

0.91

12

4 332.0 4332.0

361

107.31

45.67

14

4 334.0 4334.0

310

107.25

45.50

16

4336.0

271

107.2

45.16

18

4 338.0 4338.0

241

107.21

44.84

20

4 340.0 4340.0

217

107.17

44.48

25

4345.0

174

107.1

44.08

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

–  WATER  WATER QUALITY ANALYSIS LABORATORY RESULT APPENDIX C  – 

Tel. 251-(0)11-6181521/499/518, 0911211792 Fax (0)11-6181520, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

EC, pH and Temperature Te mperature result during test pumping Elapsed Time, [t] (hour)

(min)

EC

pH

(µS/m)

Temp. (℃)

1

797

7.1

37

2

856

7.2

38

3 4

825 960

7.1 7.1

37.1 37.4

5

953

7.2

37.4

6

950

7.1

37.4

7

949

7.1

37.3

8

952

7.2

37.2

9

948

7.1

37.2

Water well Drilling Results Report

10

945

7

37

11

920

7.1

37.1

12

911

7.1

37.2

13

902

7.1

37.2

14

896

7.1

37.1

15

890

7.1

37.2

16

895

7.2

37.4

17

886

7.1

37.1

18 19

879 670

7.3 7.2

37 32.5

20

670

7.1

32.4

21

675

7.2

32.4

22

672

7.1

32.4

23

675

7.2

32.4

24

670

7.2

32.3

25

673

7.1

32.2

26

674

7.2

32.4

27

671

7.3

32.3

28

674

7.2

32.3

29

675

7.1

32.3

30

673

7.2

32.2

31

670

7.1

32.3

32

673

7.2

32.3

33

672

7.2

32.4

34

672

7.3

32.3

35

671

7.2

32.3

36

672

7.4

32.3

Tel. 251-(0)11-6181521/499/518, 0911211792 Fax (0)11-6181520, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Elapsed Time, [t] (hour)

(min)

EC

pH

(µS/m)

Temp. (℃)

37

668

7.3

32.4

38

674

7.3

32.4

39

665

7.2

33

40

664

7.2

32.8

41

663

7.2

32.4

42

665

7.2

32.4

43

660

7.3

32.2

44 45

649 652

7.2 7.3

32.5 32.4

46

698

7.2

32.4

47

506

7.2

32

Water well Drilling Results Report

48

516

7.1

32.2

49

523

7.1

32.2

50

525

7.1

33

51

530

7.2

32.4

52

531

7.1

32.4

53

531

7.1

32.4

54

530

7

32.3

55

542

7.1

32.3

56

556

7

32.1

57

550

7

32.1

58

554

7

32.3

59

560

7.1

32.3

60

580

7.1

32.5

61

590

7.2

32.5

62

600

7.2

33.1

63

618

7.2

33.6

64

620

7.3

33.9

65

615

7.3

34.1

66

623

7.3

34.9

67 68

626 608

7.2 7.2

36.9 36.8

69

614

7.1

36.5

70

620

7.1

36.6

71

625

7.2

35.9

72

632

7.1

36.3

Tel. 251-(0)11-6181521/499/518, 0911211792 Fax (0)11-6181520, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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Welenchiti Town & Satellite Village Water Supply and Sanitation Project

Water well Drilling Results Report

Tel. 251-(0)11-6181521/499/518, 0911211792 Fax (0)11-6181520, P.O.Box 4661, e-mail 4661, e-mail [email protected] 

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