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Water Boards EDMUND G. BROWN JR. 00,,fRROR 41 11. cX T .ENvoy R,c.00IRIOUEZ NVIIONYIENTAL PROTEC NON Central Valley Regional Water Quality Control Board July 11,2017 Mr. Ed Martin & Mrs. Kimberly Martin 2112 South Main Street Manteca, California 95337 RE: CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD REVIEW OF CASE FILE: Tri-Ag Service, Inc., 20696 S. Manteca Road, Manteca, San Joaquin County, California (Global ID SLT5S4823431) Dear Mr. & Mrs. Martin, Central Valley Water Board staff have reviewed the sample results for monitoring well MW-3 from the Tri-Ag Service, Inc. site (Tri-Ag) located at 20696 S. Manteca Road in Manteca (Site). On June 8,2017, Central Valley Water Board staff sampled monitoring well MW-3. This correspondence is being sent to you as the current property owners for the above referenced Site. Included with this correspondence is a CD with the following files: Tri-Ag Limited Soil and Groundwater Investigation Report 2-13-2004 Tri-Ag Work Plan GWM and Soil Assessment 8-4-2004 Tri-Ag MW-3 Lab Report 6-8-2017 Site history shows that in about 2002, the surrounding agricultural area was subdivided into residential developments. In 2003, an assessment was conducted on 1.5 acres of the 5-acre property. Eight soil samples and one round of groundwater samples were taken from three monitoring wells, as described in the report prepared by Kleinfelder titled Limited Soil and Groundwater Investigation Report and dated February 13, 2004. Groundwater sampling demonstrated that all monitoring wells as well as the domestic well had nitrate above the maximum contaminant level (MCL) for drinking water. Additionally, the domestic well contained 4 micrograms per Liter (pg/L) of 1,2,3- trichloropropane (1,2,3-TCP), and 49 pg/L of 1,2-dichloropropane (1,2-DCP). A public health goal (PHG) for 1,2,3-TCP was developed by the Office of Environmental Health Hazard Assessment (OEHHA) for use by the State Water Board to establish an MCL. This PHG represents the level of 1,2,3-TCP in drinking water that does not pose a significant risk to health over a lifetime of exposure (70 years).The PHG for 1,2,3-TCP is 0.0007 pg/L, or 0.7 parts per trillion (ppt). The MCL for 1,2-DCP has been set at 5 pg/L. The last documented level of 4.0 pg/L for 1,2,3-TCP in the Tri-Ag domestic well exceeds the above referenced screening level of 0.0007 pg/L by approximately 10,000 times. E. LONGLEY ScD, P.E.. CHAIR I PAMELA C. CRLECON P.E.. BCEE, EXECUTIVE OFFICER 11020 Sun Center Drive 0200, Rancho Cordova, CA 95670 I www.waterboards.ca.govicentralvalley Ca BCC 'IGLOO ORPF