California Regional Water Quality Control Board, San Diego Region

June 15, 2016

In reply refer to: SL209094184:smcclain

Mr. Hossein Nassiri Hazardous Substance Engineer Department of Toxic Substances Control 5796 Corporate Avenue Cypress, California 90630

Subject:

Comments on Feasibility Evaluation, Felicita Creek, Chatham Site, Escondido, California

Mr. Nassiri: The California Regional Water Quality Control Board, San Diego Region (San Diego Water Board) has completed its review of the Feasibility Evaluation, Felicita Creek, Chatham Site, Escondido, California (Report), dated December 22, 2015, prepared by Hargis and Associates on behalf of the Chatham Site PRP Group (PRP Group). The San Diego Water Board provides the following comments: The Selected Alternative FC-1 Does Not Meet Agency Requirements As previously stated in meetings and comment letters, the discharge of contaminated groundwater from the Chatham Site (Site) to Felicita Creek is a violation of the San Diego Water Board’s Basin Plan Prohibitions.1 Therefore, the selected alternative FC-1, simply continued monitoring, does not meet regulatory requirements. In addition, the selected remedy fails to address DTSC comments on the 5-Year Remedy Review Report. The DTSC Memorandum dated February 26, 2015, attached to the March 17, 2015 DTSC comment letter, states that “The evaluation should address mechanisms which would significantly reduce or stop the flow of site related contaminants to the creek.” The selected alternative FC-1, essentially a “no action alternative,” does not reduce or stop the flow of site related contaminants into the creek.

1

Water Quality Control Plan For the San Diego Basin (9), Chapter 4 Implementation, Waste Discharge Prohibitions.

HENRY ABARBANEL PH.D., CHAIR │ DAVID GIBSON, EXECUTIVE OFFICER 2375 Northside Drive, Suite 100, San Diego, CA 92108-2700 │ (619) 516-1990 │ www.waterboards.ca.gov/sandiego RECYCLED PAPER

Mr. Nassiri

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June 15, 2016

Additional Investigations Needed to Determine Contaminant Pathways The Report failed to include sufficient information regarding the contaminant pathways from the Site to Felicita Creek. A basic principle in conducting feasibility studies is to first determine if there is sufficient hydrogeological information regarding the contaminant pathways. On several occasions DTSC and the San Diego Water Board indicated that additional investigations should be performed to determine the migration pathways through which the contaminants flow in groundwater from the Site into Felicita Creek. For example: 1. DTSC comment letter dated March 26, 2013 stated “Contaminant pathways to the creek need to be identified in order to propose effective mitigation measures to reduce the concentrations and stop the flow of contaminants into Felicita Creek…Submit a …Technical Memorandum…describing additional investigations…The Technical Memorandum must propose additional investigations…to determine the contaminant pathways from the site to Felicita Creek.” 2. DTSC Memorandum dated February 26, 2015, attached to the March 17, 2015 comment letter, also stated that “the selected alternative may need a detailed study to identify the contaminant flow paths from the site to Felicita Creek...” 3. During meetings with the PRP Group in 2015, DTSC and the San Diego Water Board provided several references regarding what additional investigations are necessary to sufficiently determine the contaminant pathways such that remedial alternatives are effectively evaluated. The references provided included the USGS “Draft Technical Protocol for Characterizing Natural Attenuation of Chlorinated Solvent Ground-Water Plumes Discharging into Wetlands.” Even though the document has a primary focus on evaluating natural attenuation, many of the technical protocols in this document are applicable to addressing the site-contaminants flowing into Felicita Creek. For example: a. “The [conceptual] model should show where and how fast the ground water flows, where the contaminants are located and at what concentrations…” The PRP Group’s conceptual model and Feasibility Evaluation do not provide this information in sufficient detail to allow proper identification and evaluation of remedial alternatives. b. USGS’s Figure 7 (provided below) shows the approach of using nested piezometers within or adjacent to the water body to provide sufficient resolution of where the contaminants are located and at what concentrations. In contrast, there are very few water table wells within a few hundred feet of Felicita Creek, and those typically have long 20-foot screen lengths.

Mr. Nassiri

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June 15, 2016

Figure 7 from USGS Draft Technical Protocol for Characterizing Natural Attenuation of Chlorinated Solvent Ground-Water Plumes Discharging into Wetlands, January 2006.