ARCHIVED REPORTS XR0004613 - Laserfiche WebLink

Home Browse Search

v A S S O C I A T E S I N C . i- petroleum hydrocarbons. One groundwater sample was collected from each boring at the depth groundwater was first encountered. Groundwater samples indicated the presence of petroleum hydrocarbons. Results are summarized in ATC's Summary Report of Additional Subsurface �- Investigation, dated September 9, 1998. On February 18, 1999, a geologist from ATC Associates supervised the installation of three L' groundwater monitoring wells from 39 to 41 feet bgs. Soil borings MW1, MW2, and MW3 were completed as two-inch monitoring wells. One soil sample from each boring was collected and after the groundwater monitoring wells were developed on groundwater sample was collected ` from each well. Soil and groundwater samples contained detectable concentrations of petroleum hydrocarbons. Results are summarized in ATC's Summary Report of Additional Subsurface LO Investigation, dated June 1, 1999. In September and October 2001, a geologist from ATC Associates supervised the advancement of six off-site soil borings to approximately 25 feet bgs. Analytical results of soil and groundwater samples indicated that no petroleum hydrocarbons were present off site. One soil boring was advanced on site in the vicinity of the former USTs to evaluate the vertical extent of impacted L groundwater. A groundwater sample collected from the second water-bearing zone indicated that no petroleum hydrocarbons were present. Results are summarized in ATC's Summary Report of " Supplemental Subsurface Investigation, dated January 4, 2002. 2.0 SUBSURFACE CONDITIONS r— 22.1 Hydrogeology Water level measurements were collected from wells MW1 through MW3 on July 16, 2002. `r Water levels ranged from 27.37 to 28.01 feet below the tops of the well casing elevations_ Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the northeast. The average hydraulic gradient on July 16, 2002 ` was calculated to be 0.001 ft/ft or approximately 5.3 ft/mile. A summary of groundwater monitoring data is presented in Table 1. 3.0 GROUNDWATER PUMPING PILOT TEST L The objective of this pump test was to determine whether groundwater extraction will lower the concentrations of petroleum hydrocarbon constituents to acceptable levels over a reasonable period. The following information was collected and evaluated: • Radius of influence of groundwater extraction; • Groundwater drawdown; ' • Hydrogeologic properties of the aquifer; • Mass extraction rate of groundwater. w:\wordpro1149811repoMTump_test.doe 2 L