|
• _ EuuuNv G. BXuwry JX.
<br /> >i - wEn"on
<br /> ........�to
<br /> ENVIRONMENTAL
<br /> TAL PROTECTION
<br /> Water Boards `"`"°""`""`°"°""'°"
<br /> Central Valley Regional Water Quality Control Board
<br /> RECEIVED
<br /> 20 May 2014
<br /> MAY 21 2014
<br /> Ms. Jennifer Sedlachek
<br /> Exxon/Mobil Environmental Services Company ENVIRONMENTAL HEALTH
<br /> 4096 Piedmont Ave, #194 PERMITISERVICES
<br /> Oakland, CA 94611
<br /> FORMER MOBIL STATION 99CAS (AKA MARLER PROPERTY, and JH GRIFFIN MOBIL
<br /> SERVICE), 75 EAST ALPINE AVENUE, STOCKTON, SAN JOAQUIN COUNTY
<br /> (CASE#390857)
<br /> The California Regional Water Quality Control Board-Central Valley Region (Central Valley
<br /> Water Board) staff reviewed the Groundwater Monitoring and Remediation Status Report, First
<br /> Quarter 2014 (Report) submitted on your behalf by Cardino ERI on 29 April 2014. Cardino ERI
<br /> conducted groundwater monitoring on 19 and 20 March 2014. Results continue to show
<br /> groundwater concentrations are not declining significantly, with Benzene at 6400 micrograms
<br /> per Liter (ug/L), 5,200 ug/L; and 8,300 ug/L in MW-4, EX-1, and EX-2 respectively while under
<br /> active soil and groundwater remediation. The water quality objective for benzene is 1 ug/L and
<br /> the State Water Resources Control Board's Low Threat Closure Policy requires concentrations
<br /> of benzene below 3,000 ug/L before regulatory closure of an underground storage tanks case
<br /> may be considered.
<br /> The soil vapor extraction (SVE) portion of the SVE/air sparging (AS)treatment system removed
<br /> approximately 531 lbs. (80.5 gal.) of petroleum hydrocarbons during 62 days of operations in
<br /> the first quarter of 2014, or 8.5 lbs. (1.3 gal.) per day. Since April 2012, SVE has removed
<br /> approximately 12,320 lbs. (1,867 gal.) of TPH in soil. We are concerned the reported operation
<br /> of the treatment system was less than 70% of the available run time, and petroleum
<br /> hydrocarbons recovery was less than 2 gallons per day during the first quarter 2014 reporting
<br /> period. Please submit a Work Plan to optimize the SVE/AS treatment system, or to enhance
<br /> the existing system with additional technology(s), by 30 July 2014.
<br /> Cardino ERI recommended continued operation of the SVE/AS treatment system and continued
<br /> Quarterly Monitoring of monitoring wells DW-1, DW-2, EX-1, EX-2, MW-2, MW-4, and MW-5,
<br /> with semiannual monitoring of MW-1, MW-3, and DW-3, and annual monitoring of MW-6
<br /> through MW-8, and DW-4. Horizontal and vertical delineation of the groundwater plume is
<br /> defined at this site by: DW-1 through DW-4 are non-detect (ND) or slightly above detection
<br /> limits (DW-1 Benzene, 0.52 ug/L), effectively delineating deeper impacts laterally as well as
<br /> vertically. MW-6 (ND) delineates lateral extent to the north, MW-8 (ND) to the northeast,
<br /> MW-7 (ND) to the southeast, MW-5 (Benzene, 1.0 ug/L)) effectively defines the pollution to the
<br /> south, and MW-3 (ND) defines the extent of impacts to the west. Therefore, we concur with
<br /> Cardino ERI's recommendations and believe that sufficient monitoring data exists to allow an
<br /> additional reduction in the frequency of monitoring in the following wells: MW-1, MW-3, MW-5,
<br /> DW-1, DW-2 and DW-3, to annual monitoring. The next quarterly groundwater monitoring and
<br /> remediation status report is due 30 July 2013.
<br /> KARL E. LONOLEY SCD, P.E., GHMR I PAMELA C. GREEDON P.E., BCEE, CXCCUTIVC Orriccn
<br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 85570 I www.waterboards.ca.gov/contralvalley -
<br /> C,aecvcaeo veEEa
<br />
|