WORK PLANS - Laserfiche WebLink

Home Browse Search

Di salvo Truddng-WP July 25,1995 Page-3- *f 3.4 PROPOSED SCOPE OF WORK Condor recommends pumping MW1 in an at empt to evaluate the lateral extent of groundwater contamination associated with the former UST's located at the site. MW is located in the estimated down gradient direction approximately 10 feet northwest of the former east end of TK4. Based on aquifer parameters discussed in section 3.1, Condor estimates that in a time period of 14 days at least one pore volume can be extracted from a cylindrical area surrounding MW1 with a circumference of approximately 10 feet. One groundwater sample will be collected from MW1 following extraction of one ore volume. If hydrocarbon constituents are detected at or above the reported laboratory det ction limits in the groundwater sample, pumping will continue until 14 days has elapsed or 10,000-gallons have been pumped. A final groundwater sample will be collected from MW1 at he end of pumping. The extracted groundwater will be stored on site ina 10,000-gallon frac tank. 3.1 Aquifer Parameters The site geology generally consists of medium sand from 10.5 feet to 16 feet bgs and silt from 16 feet to 18.5 feet. The hydraulic conductivity of silt is on the order of 100 times lower than the hydraulic conductivity of sand. In June, 1995, the static water level in MW1 was approximately 11.90 feet below the ground surface. ondor assumes the thickness of the aquifer is governed by the top of the water column (11.90 ft. bgs in June, 1995) and the top of the silt at 16.0 feet bgs. Therefore, the thickness of he shallow aquifer is approximately 4 feet. Based on an estimated aquifer porosity of 40%, the volume of groundwater present in a cylindrical area 10 feet from MW1 is approximately 3,800 gallons. A minimum hydraulic conductivity value for sandy material of 8.2 ft/day ( odd, Groundwater Hydrology, 1980) was used to evaluate the effects of pumping from MW1. The groundwater parameters were simulated using the Quickflow groundwater modeling program. Modeling indicated that pumping MW1 at 1 gpm would cause a 3 foot drawl Dwn and create a cone of depression of approximately 120 feet. If 1 gpm is achieved, one pc re volume of groundwater will be extracted within 3 days. Figure 3, Appendix A'shows results of the modeling program. 3.2 Pumping A submersible pump will be placed in MW1 t 16 feet bgs to allow for maximum draw down. The pump will be fitted with a high-low shut off switch to insure the water table does not drop 'below the pump inlet during pumping. All hoses and fittings will be securely attached to prevent rupture and potential surface discharge. Tbe groundwater will be pumped from tr= MW1 to a 10,000-gallon frac tank located on site. Following installation and setup, a Condor 1 - " CONDOR