WORK PLANS - Laserfiche WebLink

Home Browse Search

CVATeo v A S S O C I A T E S I N C . petroleum hydrocarbons as diesel (TPHd) have ranged from nondetect to 1,100 parts per billion in wells MW-1,MW-2,MW-3,MW-5 and MW-6. Free product has been present in well MW-4 since 1992. The free product thickness has varied from trace amounts to 8.41 feet. From May 1992 through May 1998, free product has been removed from well MW4 by method of hand bailing. A passive skimmer was installed in well MW4 in May 1998 to collect free product. The skimmer has been monitored and maintained on approximately a monthly basis. To date, a total of approximately 34.34 liters or 9.07 gallons has been removed from the well. Over the past two years, there has been an increase in rainfall and subsequently an increase in the groundwater elevation. The increase in groundwater elevation appears to have resulted in a decrease in free product recovery. OBJECTIVE The objective of this work is to evaluate the stability of the free product plume and determine if the plume is declining. As previously stated, an increase in groundwater elevation at the site appears to have resulted in a decrease in free product recovery. In addition, the removal of free product reduces pressure on the groundwater table and contributes to the rise in groundwater elevation. The elevated groundwater in the vicinity of well MW4 may be "pinching off' the free product plume and preventing it from entering the well casing and thus reducing the free product thickness to a sheen in the well casing. ATC proposes to perform the 24-hour pumping test in an effort to reduce the water table elevation and allow free product, if any, to flow into the well casing. Following the pumping test, ATC will advance additional soil borings in the vicinity of well MW4 to obtain sufficient data to quantify the free product plume. SCOPE OF WORK 24-Hour Pumoine Test ATC will perform a 24-hour pumping test on well MW-4. PHS/EHD will be notified at least 48 hours in advance of performing any fieldwork. Upon arrival to the site, ATC personnel will remove the passive free product skimmer from well MW-4. Water levels will be measured in monitoring wells MW 1 through MW6. A 2-inch Redi-Flog, submersible pump equipped with a flow meter capable of reading flows up to 10 gallons per minute (gpm) and a discharge hose will be installed in well MW-4. ATC will use a generator to supply power to the pump. Additional information on the submersible pump is provided in Attachment 1. Groundwater will be extracted from the well at a rate of approximately 3 gpm. If the well can sustain a greater flow, ATC will increase the flowrate accordingly. If the well goes dry, the pumping test will be temporarily halted to allow groundwater to sufficiently recover and the test will be restarted. The extracted groundwater will be discharged directly to the sanitary sewer under permit. w:\62574\62574.02\reports\pumpwkp.doc 2