Laserfiche WebLink
Ms. Lori Duncan <br /> _ June 12,2007 <br /> CONESTOGA-ROVERS <br /> &ASSOCIATES. <br /> Maximum Contaminant Levels (MCLS) are enforceable regulatory standards-under the Safe prinking <br /> Water Act and must be met by all drinking water systern.to which they apply. MTBE has a primary <br /> (health protection based) MCL of 13 uglL and a secondary (taste and odor based) MCL of 5 ug/L. The <br /> mass flux estimate results illustrate that the MTBE concentration in a virtual supply well would be.at <br /> least an order of magnitude lower than the secondary MTBE MCL.. m <br /> EVALUATION OF REMEDIAL ACTIVITES " <br /> _ Current remediation at the site consists of monthly groundwater extraction (GWE) by vacuum truck <br /> (vacops) from wells MW-1 and MW-6. .Vacops has been performed since August 2005. A.total%of <br /> 12,481 gallons of groundwater has been-extracted as of March_2007 equating to 0.107 pounds of MTBE <br /> removed. Table 3 presents historical vacops mass removal data. - <br /> The average MTBE removal rate can also be expressed as 8:57x10-6 pounds per gallon. Assuming this <br />,. average removal rate is constant, approximately 215,870 gallons would need to.be extracted to remove <br /> the remaining MTBE mass.in groundwater(1.85 pounds). <br /> A more accurate assessment of groundwater cleanup can be estimated internis of pore volume removal. <br /> It typically requires the-removal of,4 to,6 pore volumes to achieve an. order.of magnitude decrease in <br />` dissolved-phase concentration. In.the mass remaining section of this report, one-pore volume ( 100 ppb <br /> contour)was estimated at 715,893 gallons. Four pore volumes equates to 2,863,572 gallons. The current <br /> highest MTBE concentration-of MTBE in groundwater is 470 ppb(MW-6). Approximately.2.8 million. .. <br /> gallons of groundwater would need .to -be extracted, to 'reduce, this concentration, to 47 ppb.. . <br /> Approximately 5.7 million 'gallons of groundwater would.need to^be extracted to reduce the MTBE <br /> concentration below the 13 ppb primary.MCL..These estimates do not account for concurrent reduction <br /> of MTBE concentrations by degradation or other processes. <br /> The cost to off-haul and dispose groundwater is approximately $850 per event. Based on.the historical <br /> extraction data and this cost,vacops is not a cost-effective remedial approach. <br /> 1667 6 <br /> I _ - <br /> :,Worldwide Engineering.Environmental,Construction,and IT Services <br />