Appendix E Pump Test Report

Transcription

1 Appendix E Pump Test Report

2 GROUND-WATER EXPLORATION PROGRAM LEGACY RIDGE, TOWN OF WOODBURY, NEW YORK Prepared For: Legacy Ridge August 2007 Prepared By: LEGGETTE, BRASHEARS & GRAHAM, INC. Professional Ground-Water and Environmental Engineering Services 4 Research Drive, Suite 301 Shelton, CT 06484

3 TABLE OF CONTENTS Page INTRODUCTION...1 DRILLING EXPLORATION PROGRAM...1 Bedrock Aquifer...2 Sand and Gravel Aquifer...2 TW-A...3 PW INSTALLATION OF PIEZOMETER...3 INSTALLATION OF PRESSURE TRANSDUCERS HOUR PUMPING TEST...4 WELL MONITORING PROGRAM...5 Long-Term Yield of PW WATER QUALITY...6 CONCLUSIONS...6

4 GROUND-WATER EXPLORATION PROGRAM LEGACY RIDGE, TOWN OF WOODBURY, NEW YORK INTRODUCTION Leggette, Brashears & Graham, Inc (LBG) conducted an additional groundwater exploration program, aquifer testing program, and groundwater quality assessment on the Legacy Ridge parcel in the Town of Woodbury, NY. The objective of the groundwater exploration program was to locate, install test wells and perform aquifer performance test to demonstrate sufficient yield to augment the existing water-supply sources. Figure 1 shows the location of the site in the Town of Woodbury, Orange County, New York along with the existing production wells, test wells, monitoring wells, and piezometers used during the aquifer performance test. DRILLING EXPLORATION PROGRAM The additional exploration program conducted by LBG included test well drilling completed in both the bedrock and sand and gravel aquifers from March to June To date, three bedrock test wells and two sand and gravel test wells have been completed. The following is a discussion of the preliminary yield estimate of the test wells from the bedrock and sand and gravel aquifers, including data from a 24+ hour pumping test event conducted on a successful high-yield sand and gravel well (PW-1). A previous ground-water exploration program conducted by HDR Engineering, Inc. (HDR) in 2005 on the study parcel developed three successful sand and gravel production wells identified as TW-1, TW-2 and TW-4; with respective yields of 290, 120 and 34 gpm. The wells are shown on figure 1. Details of the well completion reports of the existing water supply wells and monitoring wells completed under the supervision of HDR are provided in the report Groundwater Exploration and Hydrogeologic Report, Town of Woodbury, Orange County, NY by HDR, Inc., January 2006.

5 -2- Bedrock Aquifer The bedrock geologic map from the Orange County New York, Ground-Water Resources Study (LBG, May 1995) shows complex bedrock geology on the study parcel. The initial bedrock well drilling program considered an area north of Trout Brook Road and west of Route 9 (Mineral Spring Road). A prominent northeast to southwest trending trust fault bisects this portion of the study parcel, separating a granitic gneiss bedrock unit on the north of the fault; and Undifferentiated Lower Devonian and Silurian Rocks consisting of sandstone, shale and conglomerate rock units on the southern side of the fault. Fracture-trace maps were interpreted with additional layers of topography; bedrock geology; underling faults; geologic contacts; wells inventoried; sand and gravel deposits; and State and Federal wetlands to locate favorable locations to target high-yielding bedrock well. Locations which exhibit more than one of the above features are considered to be promising for drilling high-yielding bedrock well and the sites initially considered on the study parcel for drilling test wells exhibited a number of these favorable features. Three bedrock test wells were drilled by Turnbull Well Drilling, Inc. from March to April of 2007 under the supervision of LBG. Bedrock test wells 1, 2 and 3 (BRW-1, 2, and 3) are shown on Figure 1. The well completion reports are presented in Appendix I. All three bedrock test wells yielded about 30 gpm at termination of drilling. The project team decided to terminate the bedrock test well drilling at completion of BRW-3, considering the well yields were considered marginal for the development of public water-supply sources. Sand and Gravel Aquifer Layne Christensen Company (Layne) was contracted in April of 2007 to drill test well locations in the sand and gravel aquifer, north of Trout Brook on the study parcel. The initial drilling program completed three test borings (TB-1, 2 and 3) in the vicinity of BRW-1. Sand and gravel aquifer material was encountered in this area during drilling; however, the material was determined to not be suitable for the development of a high-yielding well. The test boring reports for TB-1, 2 and 3 are presented in Appendix II. LBG supervised the drilling of the two additional test borings and test wells drilled by Layne in June of The two six inch diameter test wells were completed as TW-A and PW-1

6 -3- (figure 1). The test boring reports and well construction diagrams for TW-A and PW-1 are located in Appendix II. TW-A TW-A was completed at a depth of 112 feet below land surface (bls). The well was screened from 102 to 110 feet bls with a 60-slot stainless steel screen. The well was screened in suitable sand and gravel aquifer material. A dense gray clay layer about 40-feet in thickness was encountered at a depth of 10 to 50 feet bls. The underlying bedrock was encountered at 112 feet bls and was composed of sandstone. The well was developed with repeated surging and pumping. PW-1 PW-1 was completed at a depth of 87 feet bls. The well screen was set at 80 to 87 feet bls with a 90-slot stainless steel screen. The well was screened in suitable sand and gravel aquifer material. Similarly a dense gray clay layer about 20-feet in thickness was encountered at a depth of 10 to 30 feet bls. The bedrock was encountered at 90 feet bls and was composed of black shale. The well was developed with repeated surging and pumping. The initial pumping conducted during development indicated PW-1 had the higher yield potential, therefore, a shortterm 24-hour pumping test was recommended on this well to determine the yield potential of a larger diameter production well. INSTALLATION OF PIEZOMETER A 1.25-inch diameter piezometer (PZ-A) was installed in the middle of the Trout Brook at a distance of about 60 feet from the test well (PW-1). A 12-inch length stainless steel screen (with drive point and coupled steel pipe) was driven into the bottom of the stream sediments to a depth of 3.73 feet. The piezometer was developed by repeated well surging. The location of PZ-A is shown of figure 1.

7 -4- INSTALLATION OF PRESSURE TRANSDUCERS Prior to the aquifer performance test, pressure transducers (mini-trolls from Insitu, Inc.) were installed on June 25, 2007 in existing production wells (TW-1, TW-3, and TW-4); monitoring wells (MW-2, MW-5, BRW-1), and in 12 Trout Brook Rd. (offsite homeowner well); TW-A, and inside and outside of the piezometer, PZ-A. These pressure transducers provided background water levels prior to, during and after the pumping tests at 1-minute intervals. 24+ HOUR PUMPING TEST On June 27, 2007 at 10:14 hours the pumping test event on PW-1 began at a rate at 250 gallons per minute (gpm). The static water level just before pumping the well was 6.5 feet below top of casing (TOC) and the pump was set at a depth of 79 feet TOC. The casing stickup was 1.67 feet above the grade. The water was discharged 300-feet downstream of the PW-1 in the Trout Brook (figure 1). The flow rate for the well were measured with pipe orifice weir at 15-minute intervals during the first hour of the test, and hourly for the balance of the test. The flow rate was constant through out the test at 250 gpm. At the 250 gpm pumping rate, the stabilized water level just prior to shutdown of the test (June 28, 2007 at 13:09 hours) was reported to be feet. It should be noted that the test was extended an additional three hours for a total pumping duration of about 27 hours. The total drawdown at the end of the 27-hour pumping test was 21.6 feet. At about 1400 hours on June 27, 2007, a slight rain (drizzle) occurred at the site for 30-minutes, however, the rain did not affect the water-level data for PW- 1, monitoring wells and piezometer. Water-level data measured during the pumping test and hydrograph for PW-1 are given in Appendix III. After the pumping test was terminated (June 28, 2007 at 13:09 hours), recovery measurements were collected in PW-1 for a period of approximately 94-hours. During the recovery period, a rain event occurred overnight on June 28, 2007, which is evident on the hydrograph for PZ-OUT (stream stage) in the Trout Brook. Based on the rain gage at West Point, New York (which is 15 miles east of the site), there was only 0.14 inches of rain on June 28, The rain did not have a discernible recharge effect on the recovery of the groundwater level. The hydrographs provided in Appendix III show the water level in PW-1 recovered

8 -5- from a final pumping water level of feet to 7.3 feet (which is 96.3% of pre-pumping condition) within 24-hours. Considering a slight region water-level decline was observed in the monitoring wells prior to the start of the test, which likely continued during the testing period and following shutdown, the well is assumed to be fully recovered at about 24 hours from shutdown of the test. WELL MONITORING PROGRAM During the pumping test program conducted on PW-1 an onsite and offsite well monitoring program was conducted. The purpose of the monitoring program was to determine if the pumping of PW-1 for 24+ hours at a rate of 250 gpm would significantly affect water-level and/or yields of existing onsite production well (TW-1, TW-3 and TW-4) and neighboring offsite wells. LBG also installed PZ-A in Trout Brook to determine any hydraulic connection with the sand and gravel aquifer and stream under pumping conditions. The hydrographs for the monitoring wells and piezometer are located in Appendix IV. A majority of the monitoring wells indicated a regional declining water-level trend prior to, during and following completion of the test on PW-1. The piezometer (PZ-IN) installed in the Trout Brook, showed about 0.4 feet of drawdown during the pump test, however, there was no discernible change in the stream stage (PZ-OUT) due to the pumping effect. Though there was minor drawdown in the piezometer, the stage in the Trout Brook was not impacted and this indicates that there is no significant effective groundwater and surface water interaction as a result of ground-water withdrawals from PW-1. The hydrograph for 12 Trout Brook Road (offsite homeowner well), located approximately 1000 feet southwest from the pumping well (PW-1), indicated about 0.75 feet of drawdown during the test, as a result of ground-water withdrawal from PW-1. Monitoring well TW-A located at a distance of only 220 feet northwest of the pumping well PW-1 showed approximately 9.5 feet of drawdown during the test. BRW-1 which is a flowing well completed in bedrock, located 1250 feet southeast of PW-1, showed no discernible impact during the test. This indicates no hydraulic connection between the sand and gravel aquifer and bedrock aquifer, as expected.

9 -6- MW-5, a sand and gravel monitoring well, located 1875 feet southeast of PW-1, showed no discernible impacts form the pumping of PW-1. TW-1, a 14-inch diameter production well located 1950 feet northwest of PW-1 shows no discernible water level drawdown due to pumping PW-1. TW-3 is a 14-inch diameter production well located 1400 feet northwest of PW-1, also showed no discernible change in the water level due to pumping from PW-1. Similarly, TW-4, a 14-inch diameter production well located 1630 feet northwest of PW-1, showed no discernible impact due to the pumping at PW-1. MW-2 is a monitoring well located 1565 feet northwest of PW-1 and the hydrograph showed no discernible impact from the pumping of PW-1. Long-Term Yield of PW-1 The specific capacity of the PW-1 after 27-hour of pumping was 11.6 gpm/ft. The maximum safe yield estimate (assuming drawdown to be five feet above the top of the screen) is 812 gpm. Therefore based on the maximum safe yield calculation, PW-1 can safely maintain a pumping rate of 250 gpm even during extended drought conditions. WATER QUALITY On June 28, 2007 at about10 hours water quality samples were collected from PW-1 and were delivered to Orange County Laboratory Analytical Services (OCL) at 11:30 hours on June 28, 2007 for all parameters required by the New York State Sanitary Code Part 5, Subpart 5-1. In addition, because PW-1 is located 60 feet from a surface-water body (Trout Brook), the analysis included microparticulate analysis (MPA) and Cryptosporadium & Giardia to determine if the well is under the direct influences of surface-water bodies. The Surface Water Treatment Rule is applied to any well under direct influence of surface-water bodies. The water-quality report will be available within two weeks of the date of this report. CONCLUSIONS Based on the result of the 27-hour pumping test conducted on PW-1, the well can sustain a yield of 250 gpm. The data indicated no discernible impact to the stream flow (stage) on Trout

10 -7- Brook. In addition, ground-water withdrawals from PW-1 during the test event indicated no discernible impacts on the existing production wells (TW-1, TW-3 and TW-4). The data indicate PW-1 can be pumped simultaneously with any of the existing production well (TW-1, TW-3 and TW-4). The hydrograph for the offsite homeowner well located at 12 Trout Brook Road indicated minor water-level interference drawdown effects of about 0.75 feet from the pumping of PW-1. The noted impacts will not impair the yield of this well. No significant offsite water-level interference effects are expected from ground-water withdrawal from PW-1 up to 250 gpm in the study region. Following completion of a larger diameter production well in the vicinity of PW-1, additional long-term testing (72-hour duration) will be conducted to confirm the yield of the well at rates equal to (250 gpm) or higher than tested for PW-1. Additional monitoring will be conducted to include onsite and offsite wells, including piezometers in Trout Brook to reaffirm above conclusions related to potential impacts. LEGGETTE, BRASHEARS & GRAHAM, INC. Reviewed by: Hillol Guha, Ph.D., P.G., P.HGW Senior Hydrogeologist/Modeler Thomas P. Cusack, CPG Principal nv August 2, 2007 H:\Legacy Ridge\WELL COMPLETION REPORT.doc

11 FIGURE

12 TW-1 TW-4 TW-3 MW-2 12 Trout Brook Road D TW-A PW-1 PZ-A Trout Brook 1 3 MW-5 D 1 2 L B G 4 Research Drive Suite 301 Shelton, Connecticut (203) O:\DWG\Legacy Ridge\2007\Fig-1.dwg, Layout1, 8/2/2007 6:46:25 PM, Acrobat PDFWriter

13 APPENDIX I

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44 LEGGETTE, BRASHEARS & GRAHAM, INC. PROFESSIONAL GROUND-WATER AND ENVIRONMENTAL ENGINEERING SERVICES RESEARCH DRIVE, SUITE 301 SHELTON, CT (203) FAX (203) August 20, 2007 Mr. Stuart E. Bassell, P.E., A.I.C.P. Senior Project Manager Lawler, Matusky & Skelly Engineers, LLP One Blue Hill Plaza P.O. Box 1509 Pearl River, NY RE: Legacy Ridge Water-Quality Results, PW-1 Woodbury, New York Dear Mr. Bassell: Attached is copy of the laboratory results for the water-quality samples (Appendix I) collected during the pumping test completed on PW-1 located on the Legacy Ridge study parcel in Woodbury, New York. As required by the New York State Department of Health (NYSDOH), the samples were analyzed for all parameters specified in the NYSDOH Sanitary Code, Part 5, Sub-part 5-1. In addition, PW-1 is located within 200 feet of a surface-water body which required the collected of a microparticulate analysis (MPA) to determine if the well is under the direct influence of surface water. The Surface Water Treatment rule is applied to any well under the direct influence of surface-water bodies. The water-quality results for PW-1 meets all New York State Drinking Water Standards. A sodium concentration of 16 mg/l (milligrams per liter) and a chloride concentration of 18 mg/l were reported for the well. Both concentrations are well below NYSDOH recommended concentration and maximum concentration levels (MCL) of 270 mg/l and 250 mg/l, respectively, for sodium and chloride. The MPA results for PW-1 reported no presence of Giardia and Cryptosporidium in the sample collected. The report also stated that no algal organisms exhibiting chlorophyll fluorescence, which area primary indicator of GWUDI (ground water under direct influence of surface water), were observed in the sample. Plant debris was noted in the sample. However, again no chlorophyll fluorescence was noted in the plant debris. These MPA results indicate that well PW-1 is at a low risk for GWUDI. CONNECTICUT OHIO ILLINOIS SOUTH DAKOTA PENNSYLVANIA FLORIDA NEW JERSEY MINNESOTA TEXAS WISCONSIN NEW YORK MISSOURI VERMONT MICHIGAN

45 Mr. Stuart E. Bassell -2- August 20, 2007 If you have any questions, please feel free to contact me at Very truly yours, LEGGETTE, BRASHEARS & GRAHAM, INC. SS:cmm Enclosures cc: M. Rosenzweig H:\Legacy Ridge\water-quality cover ltr.doc Stacy Stieber Hydrogeologist II

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