| Abstract: | This report presents the results of a study by
the U.S. Geological Survey in cooperation with the
U.S. Environmental Protection Agency to evaluate
ground-water flow in Triassic sedimentary rocks
near Colmar, in Bucks and Montgomery Counties,
Pa. The study was conducted to help the U.S. Environmental
Protection Agency evaluate remediation
alternatives at the North Penn Area 5 Superfund
Site near Colmar, where ground water has been
contaminated by volatile organic solvents (primarily
trichloroethene). The investigation focused on
determining the (1) drawdown caused by separately
pumping North PennWater Authority wells
NP?21 and NP?87, (2) probable paths of groundwater
movement under present-day (2000) conditions
(with NP?21 discontinued), and (3) areas contributing
recharge to wells if pumping from wells
NP-21 or NP?87 were restarted and new recovery
wells were installed. Drawdown was calculated
from water levels measured in observation wells
during aquifer tests of NP?21 and NP?87. The
direction of ground-water flow was estimated by
use of a three-dimensional ground-water-flow
model.
Aquifer tests were conducted by pumping
NP?21 for about 7 days at 257 gallons per minute
in June 2000 and NP?87 for 3 days at 402 gallons
per minute in May 2002. Drawdown was measured
in 45 observation wells during the NP?21
test and 35 observation wells during the NP?87
test. Drawdown in observation wells ranged from
0 to 6.8 feet at the end of the NP?21 test and 0.5 to
12 feet at the end of the NP?87 test. The aquifer
tests showed that ground-water levels declined
mostly in observation wells that were completed in
the geologic units penetrated by the pumped
wells. Because the geologic units dip about
27 degrees to the northwest, shallow wells up dip
to the southeast of the pumped well showed a
good hydraulic connection to the geologic units
stressed by pumping. Most observation wells
down dip from the pumping well penetrated units
higher in the stratigraphic section that were not
well connected to the units stressed by pumping.
The best hydraulic connection to the pumped wells
was indicated by large drawdown in observation
wells that penetrate the water-bearing unit
encountered below 400 feet below land surface in
wells NP?21 and NP?87. The hydraulic connection
between wells NP?21 (or NP?87) and observation
wells in the southern area of ground-water contamination
near the BAE Systems facility is good
because the observation wells probably penetrate
this water-bearing unit.
A 3-dimensional, finite-difference, groundwater-
flow model was used to simulate flow paths
and areas contributing recharge to wells for current
(2000) conditions of pumping in the Colmar
area and for hypothetical situations of pumping
suggested by the U.S. Environmental Protection
Agency that might be used for remediation. Simulations
indicate that under current conditions,
ground water in the northern area of contamination
near the former Stabilus facility moves to the
northwest and discharges mostly to West Branch
Neshaminy Creek; in the southern area of contamination
near BAE Systems facility, ground water
probably moves west and discharges to a tributary
ofWest Branch Neshaminy Creek near well NP?21.
Model simulations indicate that if NP?21 or NP?87
are pumped at 400 gallons per minute, groundwater
recharge is likely captured from the southern
area of contamination, but ground-water recharge
from the northern area of contamination is less
likely to be captured by the pumping. Simulations
also indicate that pumping of a new recovery well
near BAE Systems facility at 8 gallons per minute
and two new recovery wells near the former Stabilus
facility at a total of about 30 gallons per minute
probably would capture most of the ground-water
recharge in the areas where contamination is
greatest. |
| Genre: | USGS Numbered Series |
| ProdID: | 53121 |
| Citation Author: | Risser, Dennis W.; Bird, Philip H. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | viii, 73 p. : ill. (some col.), maps (some col.) ; 28 cm. |
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| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 2003-4159 |
| Citation Search Results Text: | Aquifer tests and simulation of ground-water flow in Triassic sedimentary rocks near Colmar, Bucks and Montgomery Counties, Pennsylvania; 2003; WRI; 2003-4159; Risser, Dennis W.; Bird, Philip H. |
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| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Aquifer tests and simulation of ground-water flow in Triassic sedimentary rocks near Colmar, Bucks and Montgomery Counties, Pennsylvania; 2003; WRI; 2003-4159; Risser, Dennis W.; Bird, Philip H. |
| URL (THUMBNAIL): | http://pubs.usgs.gov/wri/2003/4159/report-thumb.jpg |
| URL (DOCUMENT): | http://pubs.usgs.gov/wri/2003/4159/report.pdf |
| Date Other: | Tue, 1 Jul 2003 00:00 -0500 |
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