Flowmeter Tests in Pak Kong Slope

(2nd draft)

Dr Jimmy Jiao

Department of Earth Sciences The University of Hong Kong

September 13, 2007

Flowmeter Tests in Pak Kong Slope

Contents 1. Introduction ...... 3

2. About the site and boreholes ...... 3

3. Basics of a flowmeter test ...... 5

3.1 Equipment ...... 5 3.2 Theory ...... 6

4. Test and results ...... 9

4.1. Tests in PH3 ...... 9

4.1.1 Field procedure ...... 9 4.1.2 Data analysis ...... 10 4.1.3 Estimation of K profile ...... 12 4.2 Tests in PH4 ...... 14

4.2.1 Field procedure ...... 14 4.2.2 Data analysis ...... 15 4.3.3 Estimation of K profile ...... 15 5. Conclusions ...... 16

References ...... 18

Appendices ...... 40

1. Introduction

The Department of Earth Sciences in The University of Hong Kong was invited to conduct flowmeter tests in two drillholes installed in the Pak Kong slope as part of the ground investigation for landslides coordinated by Maunsell Geotechnical Services Limited. This report presented the field measurements, data interpretation and findings of the flowmeter tests.

2. About the site and boreholes

The site is located at Slope No. 8SW-C/CR175, near Pak Kong Water Treatment Works at Sai Kung (Figures 1 and 2). The site is underlain by bedrock of coarse ash crystal tuff. More information on site geology can be found in the report by Maunsell Geotechnical Services Limited (2005).

Two boreholes PH3 and PH4 were drilled by DrilTech Ground Engineering Ltd. Drilling of the holes was carried out using hydraulic rotary drilling rigs with air foam as flushing medium (DrilTech, 2007). The initial diameter of the borehole was 4.5 inch. To enlarge the hole to fit the flowmeter, the holes were reamed by core barrel to increase the diameter to be?.

A PVC pipe with 107 mm internal diameter (the lower limit of the diameter which the flowmeter can work) and with 6 mm perforation at 50 mm intervals in a staggered arrangement was installed in each hole (DrilTech, 2007). The PVC pile has screens from 3 m below the top of the hole all the way down to the bottom. Details of the progress of installing PH3 and PH4 are outlined in Table 1.

PH4 is located on a relatively flat area on a road side. PH3 is located on the steep slope of a road site. Some details of the two holes are shown in Table 2. The distance between the two drillholes is 47.11 m. Each borehole has fill, saprolite and bedrock. The

3 fill in both drillholes is about 1.80 m. The bedrock is located at about 22.05 m below the ground level (measured by DrillTech) in PH3 and 21.50 m below the ground level in PH4 (DrillTech, 2007).

Table 1 Progress of installing PH3 and PH4 Activity PH4 PH3 Start End Start End Drilling March 2 March 16 April 2 April 22 Reaming March 12 April 20 April 27 May 16 Well screen installation April 21 April 24 May ? May ? Well flushing June 29 June 30 June 26 June 28

A trial flowmeter test was carried out in PH4 on May 17. It was then suggested that well development should be conducted in the drillholes after screen installation. Following the installation of a monitoring well or any well for hydraulic-test purposes, it is critical to perform a procedure called well development. The purpose of well development is to ensure removal of fines from the vicinity of the well screen which are created in the drilling processes. This allows free flow of water from the formation into the well. Development of a well should occur as soon as it is practical after installation (USEPA, 1994). Well development is a sophisticated job. If the development process is too vigorous, it may remove fine material beyond the edge of the borehole and then increase artificially the hydraulic conductivity of the aquifer (Fetter, 2001).

Figure 3 demonstrates the flushing procedure used in the development of the two drillholes used by DrillTech: 1) Feed compressed air through to base of hole and push the in-situ water out of the hole; 2) Pour normal water into the base of hole and feed compressed air; 3) Continuously repeat the above steps for two to three days until water seeping into the borehole becomes clean. The flushing in the two holes was carried out between June 26 and 29 (Table 1).

Figure 4 shows the well structure after the completion of the installation. The ground levels of PH3 and PH4 are 65.94 and 67.07 mPH, respectively. The ground level of PH4 is the same as the level of the surface of the concrete box over the borehole, but

4 ground level of PH3 is lower than level of the surface of the concrete box (Figures 4 and 5). The difference is estimated to be about 0.3 m.

All the downhole measurements of this study used the top of the concrete box as the ground level or zero point of the well depth. If the data from PH3 are used to compare with the results from other hydraulic conductivity studies, the difference of 0.3 m should be noted.

Table 2 Some details of the two boreholes PH3 and PH4 (from DrillTech (2007) except water-level data) PH3 PH4 Ground level (mPD) 65.94 67.07 Easting 845124.09 845087.67 Northing 826749.12 826779.01 Depth of the hole 43.87 37.16 Residual soil bottom level (mPD) 61.14 63.37 Completely to highly decomposed rock (mPD) 43.89 45.57 Moderately decomposed or less decomposed 43.89? 45.57 ? rock (top level, mPD) End of hole (mPD) 22.07 29.91 Water-level depth from top of the concrete box 17.11 m at 12.46 m at 9:40am, 5/7 9:40 am, 3/7

3. Basics of a flowmeter test

3.1 Equipment A borehole flowmeter can be used to measure the ambient (natural) flow in boreholes; it also enables one to determine the flow distribution in the borehole under pumping or injection condition, or so-called stressed well conditions. These data allow to determine relative aquifer hydraulic conductivity as a function of depth or identify fracture locations depending on the type of aquifer as described by Molz et al. (1994). If

5 the average hydraulic conductivity of the aquifer is estimated by a pumping or injection test or any other aquifer tests, the hydraulic conductivity of individual layers or zones can be estimated.

The flowmeter type used for this study is heat-pulse flowmeter (Model HFP-2293) with a measuring range of 0.03 to 1.0 gallon/min (or 0.113 to 3.785 L/min). It was produced by Mount Sopris Instrument Co., Inc. USA. The flowmeter is operated by MGXII, a geophysical logging system. The flowmeter measures the direction and rate of vertical flow in the borehole. Accurate measurements require sufficient time between readings for the area around the tool to stabilize. At least three readings are required per interval in order to obtain a reasonably reliable average flow rate.

The flowmeter is supplied with PC based software, centralizers and a range of diverters for 4 inch through 8 inch (101.6 mm through 203.2 mm) boreholes. The measurements occur in the probe, and the water flow outside the flowmeter will be blocked by diverters. The flowmeter is of 122 cm in length and 4.1 cm in diameter. Diverters are devises that divert flow in the borehole through a column where the measurement is taken by the tool.

The fluctuation of water level in the well during the entire test period should be monitored when the flow is measured by the flowmeter under ambient or stressed flow conditions. The water level information can be used to assist the interpretation of flowmeter data, and under stressed well condition the water level data can be used to estimate the average hydraulic conductivity of the aquifer. For the Pak Kong site, a computer-operated transducer called miniTROLL 9000 produced by In-Situ Inc., USA was used to monitor the water level. Water level was also measured manually from time to time so that the results of the transducer could be cross checked. The manually-measured data can be used as a backup in case that the transducer goes wrong for any unexpected reason.

3.2 Theory

A pump is placed in the borehole and operated at a constant flow rate Q. When pseudo steady state behavior is obtained, the flowmeter is lowered to near the bottom of the borehole to measure the flow. The flowmeter is then raised by one meter to take another reading. This is repeated until it is near the water level.

Assuming that the aquifer is composed of n horizontal layers, Molz et al. (1989, 1990) developed the following equation to estimate the relative hydraulic conductivity

(Ki/ K ):

K (ΔQ − Δq )/ Δz i = i i i (1) K Q / Z

th where Ki=horizontal hydraulic conductivity of the i layer; K = average horizontal th hydraulic conductivity of all the layers; ΔQi = total flow from i layer into the well;

th th Δqi = ambient flow from i layer; Δzi = i layer thickness; and, Z = total thickness of the aquifer.

Equation (1) was obtained under a few assumptions. For example, the aquifer has many sub-layers which have no vertical hydraulic connection and share the same influential radius where the head remains unchanged; the aquifer has no lateral boundary;

ΔQi and Q do not change with time, or the system is in a steady state.

If there is no boundary such as a river or the sea, it is impossible for the aquifer system to approach an absolute steady state under pumping or injection condition. For a practical problem, the above equation can be applied approximately if the system approaches a so-called pseudo steady state (Molz et al. 1989 and 1990). Such a state occurs when

2 rw S / 4Tt ≤ 0.01

where rw is effective well radius, S is aquifer storage coefficient, T is aquifer transmissivity, and t is time since pumping.

As calculated later, the estimated transmissivity in PH3 and PH4 is of the order of 10-5 and 10-6 m2/s, respectively; the estimated storativity is of the order of 10-3. The internal well diameter is 107 mm. The above equation was used to estimate the time after which a pseudo steady condition was achieved in the two boreholes:

2 2 −3 −6 t > rw S /(0.01× 4T ) = (0.107 / 2) S ×10 /(0.01× 4×10 ) = 342(sec) = 5.7(min)

The above calculation means that the water level changes quickly within about 6 minutes. After that the pseudo steady condition can be achieved. This estimation, however, is very rough and uncertain. For the flowmeter testing at Pak Kong site, the flowmeter data taken at time much longer than 6 minutes were used in the final calculation.

Equation (1) indicates that the direct result of a flowmeter test is the ratios of hydraulic conductivity of individual layers to the average hydraulic conductivity of all the layers, or the flowmeter test can provide information on the change of relative hydraulic conductivity with depth. Thus after a flowmeter test, a plot of Ki / K versus depth can be obtained.

If a traditional pumping (or injection) test is conducted and the average hydraulic conductivity of the aquifer K is estimated, then a Ki profile can be obtained by multiplying the Ki / K values by K (Molz et al., 1989, 1990). For the study at Pak Kong site, flowmeter test and pumping (injection) test were carried out to estimate first the ratio of Ki / K and then Ki of individual layers, respectively.

4. Test and results

4.1. Tests in PH3

4.1.1 Field procedure

The field tests in borehole PH3 were conducted on July 5. The water level at 10 am was measured to be 17.11 m below ground level. A pressure transducer was installed at 17.5 m below the ground level. Because the flowmeter can only work under water level, to maximize the length of the measurable profile, an injection of water was carried out. If water is pumped from the well, the initial depth of the transducer should be carefully chosen so that the transducer is always submerged during the pumping period. Water level was also measured manually from time to time. The field setting of the flowmeter test is illustrated in Figure 6. Details of the field activities of the tests in PH3 were summarized in Table A.1

The flowmeter was lowered to the depth of 42 m where the first measurement was made. Flowmetering under ambient condition was first carried out. The measurements were taken at 1 m interval. Details of the raw data were presented in Table A.2. All the vertical flow rates detected under ambient conditions were much lower than the lower detection limit (0.113 L/min) of the flowmeter, indicating very low flow under ambient condition. Therefore, the flow rate under ambient condition was ignored in the final calculation.

After the ambient flow was measured, water was injected to the well at the rate of 1.8 L/min. This low rate was used so that it would not take too long time for the water level to approach a pseudo steady state. The water-level measurements from the transducer during the injection period were shown in Figure 7.

Two profiles of vertical flow were measured. The measurement of the first profile (profile 1) started immediately after the injection started and completed at 16:59. The second profile (profile 2) was measured between 17:05 and 18:20. During this period,

9 water level increased only 10 cm within 1.5 hours and was assumed approximately in a steady state (Figure 7). Details of the flow data from ambient flow and two profiles are shown in Table A.2.

4.1.2 Data analysis

4.1.2.1 Flowmeter data

Figure 8 shows the change of flow with depth under ambient and injection conditions. On the whole, injection‐induced flow profiles showed the expected downward flow (negative value), with absolute flow rate decreasing with depth below ground surface (for the convenience of discussion, the word “absolute” is omitted hereafter). Two profiles (profiles 1 and 2) were measured. There are three abnormal measurements along profile 2. It was decided that profile 1 should be used in further calculation and detailed explanation is given later.

Figure 9 shows the interpretation of the change of flow rate (red line) of profile 1. Whenever there is a change, there is a fracture or more permeable zone into which water flows. A greater change indicates a zone with higher hydraulic conductivity. As can be seen from Figure 9, most injection‐induced flow into the aquifer occurred in the section above 27 m. Below the depth of 27 m, the flow was very low and did not change much with depth, indicating the hydraulic conductivity in this section is low. There was a sudden increase in the flow from the depths of 26 to 25 m, indicating a very permeable zone between them. The flow then was relatively stable and changed slowly from the depths of 23 to 20 m, which suggests that the change of hydraulic conductivity over this section is not dramatic.

4.1.2.2 Injection test to estimation of K

A pressure transducer was placed below the water table to monitor the

10 fluctuation of water level in the well and the water level data during the injection period was shown in Figure 7. The injection rate was maintained as 1.8 L/min, but there was a short time period around 18:01 when the rate dropped to 1.6 L/min. As soon as this was noted, the rate was then increased to 1.8 L/min again. The change of the injection rate caused some fluctuation in the water level (Figure 7).

The total initial saturated thickness was about 25 m, including the shallow part of 14 m which was relatively very permeable. Overall the system should be regarded as an unconfined aquifer. In such a system, if the water level change caused by injection or pumping is less than 10% of the initial aquifer saturated thickness, the parameter K can be estimated approximately by Thesis Equation. It should be noted that the drawdown values should be corrected as (Xue and Zhu, 1979)

s2 Q s'= s − = W (u) (2) 2H0 4πT

Where s’ is the corrected drawdown, Q is the pumping (or injection) rate, T is the aquifer transmissivity, and W(u) is the well function.

In the data analysis for hydraulic conductivity, the data in the early injection period were usually preferred because boundary effect may be involved in the later injection period (This is especially a problem for PH4 because it is located on a spur). In the injection period, there was a change in the flow rate at about 18:00, which violates the assumption of the Theis equation. When the theoretical Theis curve was matched with the observed data, emphasis was given to the data in the early injection period (Figure 10). Hydraulic conductivity was estimated to be about 1.03 x 10‐6 m/s, which represents the average hydraulic conductivity of the borehole below about 17 m (the initial water level). The parameter K was also estimated by the Cooper‐Jacob Time‐Drawdown method and the estimated value is about 1.02 x 10‐6 m/s (Figure 11), which is very close to the estimated value with Thesis method.

4.1.3 Estimation of K profile

Theoretically, the flow rate should change progressively from zero at the bottom of the hole to the pumping or injection rate near the water table. Profile 1 satisfies this requirement, but profile 2 does not. There are three obvious abnormal measurements at the depths of 23, 22, 21 m in profile 2 (Figure 8). Similar problems occurred in previous flowmeter studies (e.g., Genereux and Guardiario, 2001). They speculated that some water may bypass the well bore and flow through the gap between the well wall and the background soil, which is possible if the well development is over done. Genereux and Guardiario (2001) suggested that such points should be discarded in further analysis.

A careful examination of these abnormal measurements shows that this may be caused by the sudden fluctuation in the water level. The record shows that there points were taken during the period between 18:07 and 18:13. At 18:01, it was found that the injection rate was somehow reduced to 1.6 L/min. The rate was then adjusted back to 1.8 L/min (See Table A.1). These caused the fluctuation of the water level and it took over 10 minutes for the water level to return back to the trend, as can be seen from Figure 7. It is believed that the points taken after that should be acceptable. If these three measurements were ignored, it can be seen that the over trend is reasonable and very similar to profile 1 (see the brown dotted line in Figure 8).

The data in profile 1 could be used for further analysis except that it was measured during the unsteady state period. A careful examination of the timings at which the measurements were taken demonstrated that this may not be really a major problem. The measurement started from the bottom and lots of time was consumed below the depth of 30 m and it took a long time for the data logger to pick up a stable reading. This is because the flow rate there was very low and the flowmeter reading was noisy. Above the depth of 30 m, the flow was reasonably

12 high and the system picked up the reading very quickly. The points above the depth of 24 m were measured between the time of 16:34 and 16:57. During this period of over one hour, the water level changed only about 3 cm (Figure 7), indicating that the system already approached to a pseudo steady state. The lower section was measured in an unsteady state, but these measurements were so small that there was no appreciable difference between steady and unsteady states, as can be seen from measurements of profiles 1 and 2 (Figure 8). Therefore, it was decided that profile 1 was used in the final calculation of hydraulic conductivity. The estimated hydraulic conductivity values were shown in Table 4.

Figure 12 shows the estimated hydraulic conductivity based on profile 1. The average hydraulic conductivity values along the profile differ by over two orders of magnitude. There is a relatively permeable zone between the depths 23 to 26 m, with hydraulic conductivity up to 10‐5 m/s. From the depth of 23 to 20 m, the hydraulic conductivity decreases. Hydraulic conductivity near the water table (above 20 m) increases again.

Table 4 Estimated hydraulic conductivity values using profile 1 in PH3

Depth range Hydraulic Depth (m) (m) conductivity (m/s)

41-42 41.5 4.59E-08 40-41 40.5 4.59E-08 39-40 39.5 4.59E-08 38-39 38.5 4.59E-08 37-38 37.5 4.59E-08 36-37 36.5 4.59E-08 35-36 35.5 4.59E-08 34-35 34.5 4.59E-08 33-34 33.5 4.59E-08 32-33 32.5 4.59E-08 31-32 31.5 4.59E-08 30-31 30.5 1.80E-07 29-30 29.5 1.80E-07 28-29 28.5 1.80E-07 27-28 27.5 1.80E-07

26-27 26.5 1.80E-07 25-26 25.5 1.44E-05 24-25 24.5 7.30E-07 23-24 23.5 1.96E-06 22-23 22.5 1.12E-07 21-22 21.5 1.68E-07 20-21 20.5 1.07E-06 19-20 19.5 1.07E-06

4.2 Tests in PH4

4.2.1 Field procedure

The flowmeter test in PH4 was conducted on July 3. The field test procedure was the same as in PH3. The ambient flow in the borehole was measured at 10:00 am, and again no obvious flow was detected. The injection was performed from 14:50pm with an injection rate of 1.6 L/min. The initial water level depth in PH4 was 12.4m. Three profiles of vertical flow were measured and each took about one hour (Table A.3). The detailed measurements of the flow rate are shown in Table A.4 and plotted in Figure 13.

The transducer installed in the well showed that the water level responded to the injection in a way as expected and the water level approached a pseudo steady state when the profile 3 was measured, as observed in the field. Thus profile 3 was used to estimate the vertical K profile. Unfortunately, the water level data in the transducer could not be extracted due to some unknown reasons which damaged the pressure transducer.

Fortunately, the water level was also measured manually from time to time. Figure

15 shows the water level data, which could be used to estimate K . The injection rate was checked at irregular time interval too and plotted in Figure 16. As can be seen from this figure, most of the time the rate was 1.6 L/min.

Because the manual data points of the water level were sporadic, a trip was arranged again on July 18 specifically for running a pumping test in PH4. The pumping test was

14 performed from 11: 55am with the pumping rate of 2.4 L/min. The pump was shut down at 13:05 pm. Another transducer was used to monitor the water level. This time the transducer worked properly and the data during the pumping and recovering periods was shown in Figure 17.

4.2.2 Data analysis

4.2.2.1 Flowmeter data

Figure 13 shows three flow profiles obtained in PH4. All the profiles have similar trend and looked reasonable. The flow data in profile 3 was used to estimate the K profile using Equation (1). Figure 14 shows the interpretation of the change of flow rate (red line) of profile 3. Most of the injection-induced outflow occurred above the depth of 20m. The flow changes fairly gradually from the depth of 20 m to 15 m. There is a relatively more permeable zone between the depth of 17 and 18 m, but this is not so outstanding as the highly permeable zone observed in PH3.

4.2.2.2 Injection and pumping tests to estimation of K

Both the water level data measured manually during injection test on July 3 and the data measured automatically during pumping test on July 18 were used to estimate the hydraulic conductivity K by the Theis method. Similarly the drawdown was corrected using Equation (2). The match between the observed data and the theoretical Theis curve is shown in Figures 18 and 19. The hydraulic conductivity was estimated to be 2.46 x 10-7 m/s.

4.3.3 Estimation of K profile

The estimated hydraulic conductivity profile is shown Figure 20 and detailed information is presented in Table 5. Generally the profile can be divided into low

15 hydraulic conductivity zone below the depth of 22 m and high hydraulic conductivity zone above 22 m. The hydraulic conductivity varies but it does not appear that there is an obvious highly permeable zone in the profile.

Table 5 Estimated hydraulic conductivity profile 3 in PH4 Hydraulic Depth range Depth (m) conductivity (m) (m/s) 35-36 35.5 9.69E-09 34-35 34.5 9.69E-09 33-34 33.5 9.69E-09 32-33 32.5 9.69E-09 31-32 31.5 9.69E-09 30-31 30.5 9.69E-09 29-30 29.5 9.69E-09 28-29 28.5 9.69E-09 27-28 27.5 9.69E-09 26-27 26.5 9.69E-09 25-26 25.5 9.69E-09 24-25 24.5 9.69E-09 23-24 23.5 7.27E-09 22-23 22.5 7.27E-09 21-22 21.5 1.45E-07 20-21 20.5 2.18E-07 19-20 19.5 5.52E-07 18-19 18.5 3.05E-07 17-18 17.5 1.28E-06 16-17 16.5 2.04E-07 15-16 15.5 5.09E-07

5. Conclusions

Field flowmeter studies were carried out in two drillholes in the slope above the Pak Kong Water Treatment. Injection or pumping tests were conducted to estimate the average hydraulic conductivity and flowmeter test to depict the depth profile of the relative hydraulic conductivity. Finally, by combining results from these two types of aquifer tests, the change of hydraulic conductivity with depth in the two boreholes was identified.

Both the water-level data measured manually during the injection test and the data monitored by a transducer during a pumping test in PH4 were used to estimate the average hydraulic conductivity. The estimated average hydraulic conductivity in PH4 was 2.46 x 10-7 m/s. Similarly, the average hydraulic conductivity in PH3 was estimated to be 1.02 x 10-6 m/s using the water-level data measured by a transducer during an injection test.

The estimated hydraulic conductivity profile in PH4 shows that the section above 22 m is very permeable but that below 22 m is much less permeable. There does not appear to be a major highly permeable zone along the profile although the hydraulic conductivity varies with depth. The estimated hydraulic conductivity profile in PH3 shows, however, that there is a highly permeable zone between the depths 23 to 26 m. This feature is obvious because the hydraulic conductivity in this zone is about two orders of magnitude greater than the materials below and above this zone. It is expected that the relatively permeable zone from 23 to 26 m may be confined under certain hydraulic conditions.

References

Cook P.G. (2003) A Guide to Regional Groundwater Flow in Fractured Rock Aquifers. Seaview Press, Henley Beach (South Australia), 108pp. Cooper, H. H. and Jacob, C. E., 1946. A generalized graphical method for evaluating formation constants and summarizing welll-field history. Trans. Am. Geophys. Union, 27: 526-534. DrilTech Ground Engineering Ltd, 2007, Final Field Work Report, Works order No. GE/2005/23.11. Agreement No. CE 50/2005/ (GE), Study of landslides at cut slope 8SW-C/CR175 at Pak Kong Treatment Works, Near O Long Village Sai Kung Genereux, D., and J. Guardiario Jr. (2001), A borehole flowmeter investigation of small-scale hydraulic conductivity variation in the Biscayne Aquifer, Florida, Water Resour. Res., 37(5), 1511–1518. Fetter, C.W., 2001, Applied Hydrogeology(4th ed), Prentice Hall Javandel, I. and Witherspoon, P. A., 1969. A method of analyzing transient fluid in multilayered aquifers, Water Resources Res., 5: 856-869. Maunsell Geotechnical Services Limited, 2005, Landslides at cut slope 8SW-C/CR175 at Pak Kong Treatment Works, Near O Long Village Sai Kung Molz, F.J., R.H. Morin, A.E. Hess, J.G. Melville and O. Guven, 1989. The Impeller Meter for Measuring Aquifer Permeability Variations: Evaluation and Comparison with Other Tests, Water Res. Res., 22, pp. 1677-1683. Molz, F. J. et al. 1990. A new approach and methodologies for characterising the hydrogeologic properties of aquifers. Robert S. Kerr Environmental Research Laboratory. Ada, Oklahoma. Report EPA/600-2-90/002; NTIS 90-167063. Molz, F. J. and Young, S. C., 1993. Development and application of borehole flowmeters for environmental assessment. Log Analyst, 3: 13-23. Molz, F.J., Bowman, G.K., Young, S.C., and Waldrop, W.R., 1994, Borehole flowmeters-field application and data analysis: Journal of Hydrology, v. 163, p. 347-371. Kabala, Z. J. 1994, Measuring distributions of hydraulic conductivity and storativity by

the double flowmeter test, Water Resour. Res., 30(3), 685-690. Schlumberger, Ltd., Log interpretation charts, New York, 1984. USEPA, Well development, 1994, http://www.epa.gov/earth1r6/6pd/qa/qadevtools/mod5_sops/groundwater/monitoring _ell_installation/ertsop2044-well-dev.pdf Xue YQ and XY Zhu, Groundwater Dynamics, Publishing House of Geology, Beijing, 1979

PH4 PH3

Figure 1 Bird view of the test site

Figure 2 Location map of the site (DrillTech, 2007)

Figure 3 Set-up of air-lifting and desilting unit (DrilTech, 2007)

Figure 4 Well structure of PH3 (left) and PH4 (right) after completion of installation (DrillTech, 2007)

Ground level

Figure 5 Well top of PH3. Note the ground level used by DrillTech (2007), which is about 30 cm lower than the top of the well.

MGXII Q PC Land surface

Pump Pressure

transducer

Screen

Flow meter

Borehole

Figure 6 Apparatus and geometry associated with a borehole flow meter. MGXII, console and PC, personal computer.

Figure 7 Change of water level depth with time under injection condition in PH3 during the flowmeter test.

Figure 8 Change of flow rate under ambient and injection conditions in PH3

Flow (L/min)

-1.5 -1 -0.5 0 15 17 19 21 23 25 27 29 31 33

Depth below ground level (m) Depth 35 37 39 Interpretation Observed 41 43 45

Figure 9 Interpretation of the observed flow rate profile 1in PH3

Figure 10 Match between the observed data during injection in PH3 and the Thesis type curve. Hydraulic conductivity was estimated to be 1.03 x 106 m/s.

Figure 11 Match between the observed data during injection and theoretical CooperJacob TimeDrawdown curve in PH3. Hydraulic conductivity was estimated to be 1.02 x 106 m/s.

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Depth (m) Depth 31 32 33 34 35 36 37 38 39 40 41 42

1E-009 1E-008 1E-007 1E-006 1E-005 1E-004 k (m/s)

Figure 12 Estimated hydraulic conductivity vs depth below ground level in PH3

Figure 13 Change of flow rate under ambient and injection conditions at PH4

Flow (L/min)

-1 -0.8 -0.6 -0.4 -0.2 0 10 12 14 16 18 20 22 24

Depth below ground level (m) Depth 26 28

30 Interpretation 32 Observed 34 36 38

Figure 14 Interpretation of the observed flow rate profile 3 in PH4

13.0 12.5 12.0 11.5 11.0 10.5 water level depth (PH4) 10.0

Depth ground below level (m) 9.5 9.0 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 Time (h)

Figure 15 Change of water level with time under injection condition in PH4 during the flowmeter test.

2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3

Injection rate (L/min) 1.2 1.1 1.0 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 Time (h)

Figure 16 Change of injection rate with time in PH4

16 Start of Pumping 15

14 Pump shutdown 13 Depth to water level (m) 12 11:30 12:00 12:30 13:00 13:30 14:00 14:30 Time (hh:mm)

Figure 17 Change of water level depth during the pumping and recovery time in PH4

Figure 18 Match between the observed data during injection and the Thesis type curve (With water-level data recorded manually in PH4 on July 3)

Figure 19 Match between the observed data during pumping test on July 18 and theoretical Thesis curve. Hydraulic conductivity was estimated to be 2.46 x 10-7 m/s.

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Depth (m) 29 30 31 32 33 34 35 36 37 38

1E-009 1E-008 1E-007 1E-006 1E-005 1E-004 k (m/s)

Figure 20 Estimated hydraulic conductivity vs depth below ground level in PH4

Appendices

Table A.1 Field logging schedule at PH3 (July 5)

Time Description Start End 9:40 10:25 Arrived at the site and started site preparation Measure water level (17.11 m), install transducer (to the depth of 17.5 m), install water tanks and pump (water was pumped from the tank to the well), lower the flowmeter to 42 m, connect the computer with transducer to start automatic measurement of water level, disconnect the computer with the transducer but connect it with flowmeter 10:26 10:46 Interrupted by heavy rain 10:47 11:15 Measurement of flow under ambient condition 11:18 13:58 To avoid further interruption of rain, the whole system was re-set up with the data logger under a nearby shelter; at the same time, taking turn having hamburger for lunch 14:15 15:20 Tried to inject water, but a few problems occurred: the pump did not work properly when the tube was lowered down to below water level, the rate was not steady. Eventually the pump was removed and water was added from the top of the well. 15:25 - The formal injection started and the rate was fixed at 1.8 L/min. 15:35 16:59 1st flowmeter profile measurement 17:05 18:20 2nd flowmeter profile measurement 18:01 The injection rate of the flow was found to reduce to 1.6 L/min. It was adjusted to 1.8 L/min again 18:25 Stop injection 19:15 Stop measuring water level (Note: the water level in PH3 was measured manually and the flow rate of injection was checked at irregular times during the field testing)

Table A.2 Flow rate (L/min) measured by flowmeter in ambient flow and stressed flow conditions in PH3

Depth Corrected Ambient flow Flow rate of Flow rate of (m) depth (m) rate profile 1 profile 2

42 41.7 -0.0265 -0.03028 -0.03028 41 40.7 -0.0265 -0.03407 -0.03028 40 39.7 -0.0265 -0.03028 -0.03028 39 38.7 -0.03028 -0.03028 -0.03028 38 37.7 -0.0265 -0.03028 -0.04542 37 36.7 -0.0265 -0.03028 -0.04542 36 35.7 -0.0265 -0.03028 -0.03785 35 34.7 -0.0265 -0.04164 -0.04921 34 33.7 -0.0265 -0.05299 -0.04921 33 32.7 -0.0265 -0.06056 -0.05678 32 31.7 -0.0265 -0.06435 -0.06813 31 30.7 -0.03785 -0.06435 -0.06813 30 29.7 -0.03407 -0.06056 -0.07192 29 28.7 -0.03028 -0.06435 -0.0757 28 27.7 -0.03407 -0.06056 -0.07949 27 26.7 -0.03785 -0.06813 -0.08327 26 25.7 -0.03028 -0.12491 -0.23089 25 24.7 -0.0265 -1.09765 -0.9841 24 23.7 -0.0265 -1.14686 -1.13929 23 22.7 -0.0265 -1.27933 -0.9841 22 21.7 -0.06056 -1.2869 -1.02952 21 20.7 -0.03407 -1.32475 -1.13929 20 19.7 -0.0265 -1.30961 -1.27555 19 18.7 -0.0265 -1.38153 -1.38153

Table A.3 Field logging schedule at PH4 (July 3)

Time Description Start End 9:35 10:30 Arrived at the site and started site preparation Measure water level (12.46 m below ground level), install transducer (to the depth of 13.14 m below ground level), install water tanks and pump (water was pumped from the tank to the well), lower the flowmeter to 36 m, connect the computer with transducer to start automatic measurement of water level, disconnect the computer with the transducer but connect it with flowmeter 10:52 12:20 Measurement of flow under ambient condition 10:25 13:40 Lunch 13:45 14:48 Setup the pump system. 14:50 Injection started (rate 1.8 L/min) 15:00 16:10 1st flowmeter profile measurement 16:20 17:33 2nd flowmeter profile measurement 17:46 18:43 3nd flowmeter profile measurement 18:01 The injection rate of the flow was found to reduce to 1.6 L/min. It was adjusted to 1.8 L/min again 18:10 Stop injection 19:21 Stop water level measuring (Note: the water level in PH4 was measured manually and the flow rate of injection was checked at irregular times during the field testing)

Table A.4 Flow rate (L/min) measured by flowmeter in ambient flow and stressed flow conditions in PH4

Depth Ambient flow Flow rate of Flow rate of Flow rate of (m) rate profile 1 profile 2 profile 3

36 -0.03028 -0.03785 -0.04164 -0.03028 35 -0.03028 -0.04921 -0.04921 -0.03028 34 -0.03028 -0.03028 -0.03028 -0.03028 33 -0.03028 -0.03028 -0.03028 -0.03028 32 -0.03028 -0.03028 -0.03028 -0.03028 31 -0.03028 -0.03028 -0.03028 -0.0265 30 -0.03028 -0.03028 -0.03028 -0.0265 29 -0.03028 -0.03028 -0.03028 -0.03028 28 -0.03785 -0.03028 -0.03028 -0.0265 27 -0.03785 -0.03028 -0.03028 -0.0265 26 -0.04164 -0.03028 -0.0265 -0.0265 25 -0.04164 -0.0265 -0.0265 -0.03785 24 -0.03028 -0.0265 -0.04921 -0.06056 23 -0.03407 -0.03407 -0.03028 -0.06056 22 -0.03407 -0.03785 -0.03407 -0.06435 21 -0.03785 -0.04921 -0.04921 -0.1022 20 -0.04542 -0.08327 -0.06056 -0.15897 19 -0.05299 -0.15519 -0.11734 -0.3028 18 -0.04921 -0.18925 -0.24981 -0.38229 17 -0.0757 -0.35958 -0.4807 -0.71537 16 -0.04921 -0.51855 -0.66995 -0.76836 15 -0.04921 -0.57532 -0.82892 -0.90083