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EDMUND G. BROWN J. <br />GOVERNOR <br />CALIFORNI• <br />Water Boards <br />Central Valley Regional Water Quality Control Board <br />26 June 2018 <br />Bob Long <br />Sierra Lumber Manufacturing Inc. <br />P.O. Box 6216 <br />Stockton, CA 95202 <br />MATTHEW RODYNOUE Z <br />SECRETARY FOP <br />ENVIRONMEN T A I. PROVE CT ION <br /> <br />WORK PLAN RESPONSE, SIERRA LUMBER CASE 1 & CASE 2,375 W. HAZELTON AVENUE, <br />STOCKTON, SAN JOAQUIN COUNTY, CASE# 390257 & 391168 <br />Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff reviewed the <br />Soil-Vapor Investigation Work Plan (Work Plan) dated 13 June 2018, submitted on your behalf by <br />Advanced GeoEnvironmental Inc (AGE) for the Sierra Lumber Case 2 unauthorized petroleum release <br />at 375 Hazelton Avenue in Stockton (Site). In the Work Plan, AGE proposes to install a single soil <br />vapor sampling well (SV-1), adjacent to both the former underground storage tank (UST) location and <br />closest Site structure, as detailed below. <br />Well Location Total <br />Depth <br />(ft bgs) <br />Soil Sampling Vapor Sampling <br />Depth <br />(ft bgs) <br />Analysis Depth <br />(ft bgs) <br />Analysis <br />SV-1 Near <br />MW-15 6.5 5 <br />TPHg, BTEX, MTBE, <br />DIPE, TAME, ETBE ' TBA, 1,2-DCA, EDB, <br />naphthalene <br />6.25-6.5 <br />IPA, oxygen <br />TPHg, BTEX, <br />naphthalene, <br />TPHg=total petroleum hydrocarbons as gasoline; BTEX=benzene, toluene, ethylbenzene, xylenes; MTBE=methyl tert butyl <br />ether; DIPE=di-isopropyl ether; TAME=tert amyl methyl ether; ETBE=ethyl tert butyl ether; TBA=tert butyl alcohol; 1,2- <br />DCA=1,2-dichloroethane; EDB=ethylene dibromide; IPA=isopropyl alcohol (leak detection compound) <br />Central Valley Water Board staff concurs with the proposed scope of work with the following <br />comments: <br />As an additional quality control measure, a shroud should be utilized during soil vapor <br />sampling. Please place a shroud over the sampling equipment, and leak detection compound <br />under the shroud. The concentration of leak detection compound under the shroud should be <br />quantified for comparison to that reported in the collected soil vapor sample. <br />In the Work Plan, AGE states that the vapor sampling probe will be placed at the bottom of the <br />borehole, with sand placed from 5 to 6.5 feet bgs. Per the Department of Toxic Substances <br />Control's (DTSC's) July 2015 joint-agency guidance document Advisory — Active Soil Gas <br />Investigations, "Place the probe tip midway in the sand pack...with at least six inches of sand <br />above and below the probe tip". As such, please center the probe vertically within the sand <br />pack. <br />By 19 October 2018, please submit a Soil Vapor Report which details the completion of the <br />above scope of work and the resultant findings. As part of the Soil Vapor Report, please <br />include an evaluation of both Case 1 (Case #390257) and Case 2 (Case #391168) Site <br />conditions as compared to Low Threat Underground Storage Tank Case Closure Policy <br />(LTCP) criteria. In this evaluation, please address both cases, and include for each a detailed <br />KARL E. LONGLEY ScD, PE., CHAIR I PAMELA C. CREEDON P.E.. BCEE, EXECUTIVE OFFICER <br />11020 Sun Center Dove *200. Rancho Cordova. CA 95670 I www.waterboards.ca.govicentralvalley