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California P-%gional Water Quality Cor -rol Board <br /> � Central Valley Region <br /> Katherine Hart, Chair <br /> Linda S. Adams 11020 Sun Center Drive#200, Rancho Cordova, California 95670-6114 Arnold <br /> Secretary for Phone (916)464-3291 • FAX (916)464-4645 Schwarzenegger <br /> Environmental http://www.waterboards.ca.gov/centr alley Governor <br /> Protection <br /> 30 August 2010 qUG <br /> Ms. Janet HeikeldNIVIN,v <br /> Olympian �'�RM/TjS�RV�FACTy <br /> 1300 Industrial Road, Ste. 2 ES <br /> San Carlos, CA 94070 <br /> DOCUMENT REVIEW, J/MCO TRUCK PLAZA, 1022 EAST FRONTAGE ROAD (AKA 22502 SOUTH <br /> HIGHWAY 99), RIPON, SAN JOAQUIN COUNTY(REGIONAL BOARD CASE# 390718) <br /> 1 reviewed the Additional Site Assessment (AKA Site Assessment/Feasibility Testing Report, or <br /> Report) received 3 August 2010 from your consultant, Conestoga-Rovers and Associates (CRA). The <br /> Report provides the results of bench scale testing using two insitu chemical oxidation techniques, <br /> Fenton's Reagent and Sodium Persulfate, to remove petroleum hydrocarbons from soil and <br /> groundwater. The Report states neither method was particularly successful in removing petroleum <br /> hydrocarbons, and does not recommend their use. In June 2010, ten additional groundwater <br /> monitoring wells (MW-11 through MW-20) were installed. No benzene or MTBE, little gasoline range, <br /> and higher diesel range constituents were detected in soil during well installations. Maximum total <br /> petroleum hydrocarbons as diesel (TPHd) results were reported in soil from MW-13 and MW-16 at <br /> 10' to 15' below ground surface, at up to 5,400 milligrams per kilogram. These depths and the <br /> locations of the wells near the above ground tanks (AGTs) correlate to an underground piping failure <br /> observed near the AGTs by San Joaquin County and Regional Board staffs in 2005. The Report does <br /> state that a recent change from standard 3 casing purge to low flow purging has resulted in significant <br /> reductions in TPHd concentrations (maximum was MW-6, from 260,000 micrograms per Liter, or ug/L <br /> in April 2010; down to 550 ug/L in July 2010), which is due to a lack of turbidity in the groundwater <br /> samples during low flow purging. The Report recommends three more quarters (one hydrologic cycle) <br /> of low flow purging prior to groundwater sampling, to confirm if low TPHd groundwater concentrations <br /> .persist and would not pose a threat if TPHd is allowed to naturally degrade without active remediation. <br /> The USEPA guidance cited as used by CRA for the low flow sampling does not address turbidity <br /> causing a three orders of magnitude reduction in concentrations for any constituents. On the contrary, <br /> the guidance states that-resu�lt:s-shb-old-be similar for—both pUrging-methods­.—A-s-this--rep-orted-pToblem <br /> with turbidity was not previously addressed, those wells identified as problematic will be redeveloped <br /> and tested for turbidity with a meter; subsequently sampled for all current constituents, first after low <br /> flow purging, then after standard purging; and both results compared during the next scheduled <br /> sampling event, to evaluate whether low flow purging should replace standard purging. If you have any <br /> stions, please contact <br /> �m/e�at (916) 464-4615 or via e-mail at jbarton@waterboards.ca.gov. <br /> James L.L. Barton, P. G. <br /> Engineering Geologist <br /> cc: Nuel Henderson, San Joaquin County Environmental Health Department, Stockton <br /> Ron Scheele, Conestoga-Rovers & Associates, 5900 Hollis St., Ste. A, Emeryville, 94608 <br /> California Environmental Protection Agency <br /> p�a Recycled Paper <br />