Central Valley Regional Water Quality Control Board
29 August 2023
Mark Perisco, Secretary
Merced Designated Local Authority
c/o Kosmont Companies
1601 North Sepulveda Blvd, Suite 382
Manhattan Beach, CA 90266
REQUEST FOR DELINEATION AND CHARACTERIZATION OF LNAPL PLUME
R ST TEXACO (FORMER EXXON), 1415 R STREET, MERCED, MERCED COUNTY, LUST CASE #5T24000349, GEOTRACKER GLOBAL ID #T0604700199
PACIFIC PRIDE CARDLOCK STATION, 1455 R STREET, MERCED, MERCED COUNTY, LUST CASE #5T24000533, GEOTRACKER GLOBAL ID #T0604709442
Central Valley Water Board staff has reviewed the following documents:
Sampling Results Summary for Sparge Point Installation and On-Site Soil Sampling (Report), dated 21 July 2023
RE: Request for Remediation Schedule and Groundwater Monitoring (Schedule), dated 21 July 2023
Castle Analytical laboratory analysis report, received 9 August 2023 (Lab Report)
Provost & Prichard Consulting Group (P&P) submitted these documents on your behalf for the R St Texaco (Texaco) and Pacific Pride Cardlock Station (Pacific Pride) underground storage tank (UST) petroleum release cases at 1415 and 1455 R Street in Merced (collectively the Site). In the Report, P&P summarizes the installation and findings of (1) two air-sparge wells SP-1 and SP-2 off-Site near the MW-6 well group and (2) four on-Site shallow soil borings on both the Texaco and Pacific Pride properties. In the Schedule, P&P presents an anticipated schedule for completion of installation and startup of the air-sparge remediation system and next groundwater sampling events. In the Lab Report, Castle Analytical presents the analytical results for groundwater samples collected in July 2023 from wells MW-5R, MW-6AR, MW-6C, and MW-10C. On 16 August 2023, Central Valley Water Board staff participated in a conference call with P&P staff to discuss the presence of light non-aqueous phase liquid (LNAPL) observed during the July 2023 sampling event, and to determine next steps.
Based on review of the submitted documents and the August 2023 call, Central Valley Water Board staff has the following comments:
R St Texaco & - 2 - 29 August 2023
Pacific Pride Cardlock Station, Merced
1. The April 2012 Technical Justification for Groundwater Media-Specific Criteria states that LNAPL is only considered “free product” in relation to Groundwater Media-Specific criteria of the Low Threat UST Case Closure Policy (LTCP) if it is migrating. Given the previous low dissolved hydrocarbon concentrations in MW-6AR and the sudden appearance of LNAPL in this well, LNAPL does appear to be migrating, and thus is currently considered free product as related to evaluation of LTCP criteria for this case.
2. The lateral extent of free product is unknown at this time. In order to effectively devise a remediation strategy for the free product, the extent and nature must be determined. Free product was observed in R Street Texaco well MW-A between 2002 and 2005. MW-A is approximately 330 feet upgradient of MW-6AR, and there are no monitoring wells in between. As such, the characterization and delineation of the extent of free product between MW-A and MW-6A is needed.
By 31 October 2023, please submit a work plan to characterize and define the extent of the free product plume, which may include soil borings, grab groundwater samples, and/or LNAPL sensors such as laser-induced fluorescence (LIF).
3. Once you determine the extent and nature of the free product, Central Valley Water Board staff will request that you submit a remedial action plan to remove free product and reduce dissolved concentrations in the vicinity of MW-6AR.
4. Due to the presence of LNAPL in MW-6AR, the focus of work at the Site and timing of remediation has shifted. As such, Central Valley Water Board staff will not require you to adhere to proposed schedules for completion of remediation installation and startup or submittal of the related report. However, please do adhere to the proposed schedules for groundwater sampling and monitoring reports.
If you have any questions or concerns regarding comments in this letter or regarding the Site, please contact Alan Buehler at (916) 464-4615 or by email at [email protected].
Alan M. Buehler, P.G. Galvin Kauffman, P.G.
Engineering Geologist Senior Engineering Geologist
R St Texaco & - 3 - 29 August 2023
Pacific Pride Cardlock Station, Merced
cc: Christine Pazin, Pacific Pride Cardgas Inc., 1455 R Street, Merced 95340 Jatinderpal & Prabhjit Randhawa, 1415 R Street, Merced 95340 Randall Hagerman & Kathryn Boyett, 1785 E. North Bear Creek Dr, Merced 95340 Amrik Randhawa & Bhupinder Gill, 1107 5th Street, Livingston 95334 James M. & Marlene S. Hagerman, 785 E. N. Bear Creek Drive, Merced 95340 Arvel R & Virginia Shackleford, 3105 N. 6th Street, Coeur D’Alene, ID 83815 Ron Rowe, Merced Co. Div. of Environmental Health, Merced Ken Elwin, City of Merced, 678 W. 18th St, Merced 95340 Greg Diaz, City of Merced Redevelopment Agency, 678 W. 18th St, Merced 95340 Robert Burks, 10451 Hyde St, Le Grand 95333
Janice Dutt, Savemart Real Estate, P.O. Box 5234, Modesto 95352 Savemart Supermarkets, P.O. Box 4278, Modesto 95352
Joseph Melehan & Larry Blackwell, c/o Frank Ratajczak, Walgreens, 1640 R St, Merced 95340
Joan Iglesias, P.O. Box 773, Merced 95341
Anna Lopez, 36033 Cripps Pl, Freemont 94536
Smith Van & Storage Company Inc., 1120 W. 15th St, Merced 95340 Jon Devish, Union Pacific Railroad, 1800 Farnam St, Omaha, NE 98102 Kosmont Companies, 1601 N. Sepulveda Blvd #382, Manhattan Beach 90266 David Norman & Linda Sloan, Provost & Pritchard Consulting, Clovis (email)