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<br /> Mr. George Luxbacher • -2 - • 6 August 2012
<br /> same depths. Groundwater samples were collected from each newly installed well and were
<br /> analyzed for sulfolane, DBCP, EDB, organochlorine pesticides and benzene hexachloride
<br /> isomers, organophosphorus pesticides, herbicides, nitrate, chloride, and sulfate. Elevated
<br /> levels of sulfolane were detected at 4,400 pg/L in groundwater sample from well PW28-40
<br /> located 20 ft south of extraction well EW-09. Concentrations of DBCP, EDB, pesticides, and
<br /> herbicides were not detected above their respective analytical reporting limits. Elevated levels
<br /> of sulfolane were detected at 180,000 pg1L from the groundwater samples collected from
<br /> extraction well EW-09 at a 30 gallons per minute (gpm) pumping rate.
<br /> In January 2012, hydraulic testing of extraction well EW-09 was conducted. Pressure
<br /> transducers were. placed in pumping well EW-09 and observation wells PW27-40, PW28-40,
<br /> PW29-40, PW26-154, PW26-199, and PW18-199 to evaluate baseline water levels.
<br /> Well Installation and Hydraulic Testing Report and Additional Well Installation Work Plan
<br /> To expedite the removal of sulfolane-affected groundwater, GHS proposes to expand the
<br /> extraction and injection well network throughout the Site by installing ten (10) additional
<br /> extraction wells: EW-10(40 ft bgs), EW-11(40 ft bgs), EW-12A(159 ft bgs), EW12B(200 ft bgs),
<br /> EW-13(150 ft bgs), EW14A(150 ft bgs), EW-14B(200 ft bgs), EW-15A(150 ft bgs), EW-15B (200
<br /> ft bgs), and EW-16(100 ft bgs). GHS also proposes to install six (6) injection wells: INJ-11A
<br /> (100 ft bgs), INJ-11 B (150 ft bgs), INJ-11 C (200 ft bgs), INJ-12 (150 ft bgs), INJ-13A (1 50 ft
<br /> bgs), and INJ13B (200 ft bgs).
<br /> With respect to the Report and the proposed work, the Central Valley Water Board staff has the
<br /> following comments:
<br /> 1. Based on the information obtained from the most recent investigations, Central Valley
<br /> Water Board staff concurs with GHS's recommendation to expedite removal of sulfolane-
<br /> affected groundwater underneath the Site. Additional extraction and treatment of
<br /> groundwater should help expedite restoration of the groundwater at the Site.
<br /> 2. Though we conceptually concur with the proposed additional pumping to expedite the
<br /> cleanup of the groundwater at the Site, it is unclear how the recent collected hydraulic
<br /> testing data was used to justify the scope of work for the proposed new extraction and
<br /> injection well network. Section 7.4 of the 15 July 2011 sulfolane Remedial Investigation
<br /> Report and Work Plan (Hydraulic Testing Work Plan) prepared by Arcadis, states: "A
<br /> pumping test will be conducted on well EW-09 to collect data regarding the hydraulic
<br /> properties (transmissivity, radius of influence)....."The transmissivity and radius of
<br /> influence were not included in the Report. Furthermore, a capture zone analysis, which
<br /> staff believes is crucial to the proposed well designs, was not presented. In addition,
<br /> Section 8.0 of the Hydraulic Testing Work Plan states: "The report will include detailed
<br /> descriptions of the methods and procedures used and technical rationale for the
<br /> conclusions reached, and will present interpretations of collected data."First, the Report
<br /> did not include any "conclusions" of the data and secondly, there was no technical
<br /> rationale given for the proposed scope of work. Therefore, please provide in an
<br /> addendum report, the necessary discussion, technical rationale and conclusions
<br /> (including a capture zone analysis) for the hydraulic testing data and how it was used to
<br /> design the proposed extraction and injection well network. Also, provide in the
<br /> addendum report any calculations and modeling results that were used for the design of
<br /> the proposed extraction and injection well network.
<br /> KARL E. LONGLEY $cD, P.E., CHAIR I PAMELA C. CREEDON P.E.. BCEE, EXECUTIVE OPPICER -
<br /> 11020 Sur,Center grive#2on.Rancho Cordova,CA 95670 f www.warerE>oerds.ca.gov/centralvalley
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