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Peter MacNicholl <br /> Page 2 <br /> May 17, 2006 <br /> changes in chemical impact characteristics in the past 11 years, the US Army Corps of <br /> Engineers (USACE) identified a data gap in the human health risk posed by chemicals <br /> of potential concern (COPCs) in soil onsite. As a result, the preparation of an updated <br /> HHRA under the current site condition is necessary. <br /> Objective: The SAP includes a Field Sampling Plan (FSP), a Quality Assurance Project <br /> Plan (QAPP), and a task-specific Health and Safety Plan (HASP). The SAP is designed <br /> to support the preparation of the updated HHRA for OU2. The updated HHRA will <br /> address potential human health risk attributed to exposure of COPCs in shallow and <br /> subsurface soil. <br /> GENERAL COMMENTS <br /> 1. Scope of Review: HERD primarily confines its review of the draft document to <br /> those sections concerning risk assessment. We assume that regional personnel have <br /> evaluated the sampling method requirements, analytical methods summary, QAPP, <br /> investigation derived waste handling, and HASP. Please clearly identify future changes <br /> or additions to the document. <br /> 2. Site Boundary: <br /> 2.1. Groundwater: Although impact to groundwater and the resultant risk attributed to it, <br /> is covered under the OU1 investigations, direct exposure to groundwater under the <br /> drinking water and domestic uses pathways should be considered complete for the <br /> current and future residential receptors onsite. The Draft SAP states that the <br /> groundwater is considered to be unsuitable for drinking water use based on its natural <br /> condition. We recommend consulting the Central Valley Regional Water Quality Control <br /> Board (RWQCB) on potential beneficial uses of the groundwater. Without an assurance <br /> from RWQCB stating no beneficial use of the groundwater, risks from direct exposure to <br /> groundwater, derived from OU1 investigation, should be included in the updated HHRA <br /> of the site. <br /> 2.2. Exposure Areas: Based on current and planned future land uses at the site, the <br /> Draft SAP divides the site into two exposure areas (EAs). EA1, approximately 2,600 <br /> acres, comprises the commercial-industrial building areas in the Central Area and the <br /> northern portions of the South Balloon. EA2, approximately 58 acres, covers the <br /> residential housing area in the North Balloon. According to the ROD for OU2, future <br /> land use of the entire site is commercial/industrial. Due to scope and budgetary <br /> limitations, portions of the Central Area, South Balloon, and North Balloon will not be <br /> included in the SAP. Therefore data from EA1 and EA2 will be used to derive the <br /> reasonable maximum exposure (RME) concentrations in the updated HHRA for OU2. <br /> The Draft SAP proposes a very low sampling density,24 soil borings for a site area of <br /> more than 7,000 acres. HERD can only support the proposed sampling density and <br /> locations if the following criteria have been met: <br /> - The site has been fully characterized in previous site investigations. <br />