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Joe Lentini -2 - 2 2 February 2030 w Former Pipelines, Tracy The MW Work Plan also proposes to advance a cone penetration test (CPT) boring to 150 feet below ground surface (bgs) in the proposed vicinity of the sentinel well to collect depth-discrete grab groundwater samples using Hydropunch sampling equipment. The data obtained from the grab groundwater samples will be used to design a cluster of three monitoring wells. The well installation report was due on 5 February 2010. The MW Work Plan also proposes to perform aquifer testing once the proposed wells are installed. On 21 January 2010, CRA contacted Central Valley Water Board staff by email on behalf of Shell and requested an extension to the due date based on.anticipation of adverse field conditions due to the wet season. Shell anticipates that the report could be submitted about 45 days after receiving the analytical laboratory reports for soil and groundwater samples collected during drilling. On 27 January, Board staff concurred with Shell's request to extend the well installation report due date to the first week of June 2010. The RA Work Plan proposes to perform the Human Health Risk Assessment (HHRA) in four key steps consisting of problem formulation, exposure assessment, toxicity assessment, and risk characterization. The problem formulation step will involve assigning toxicity based screening values for chemicals of potential concern (COPCs) in soil, groundwater, and soil vapor. Soil screening values will be selected from the California Human Health Screening Levels (CHHSLs). Groundwater screening levels will be selected from the lowest concentration of CalEPA's maximum contaminant levels, Office of Environmental Health Hazard Assessment's Public Health Goals, or the USEPA's Regional Screening Levels for Tap Water. Soil vapor values will be selected from CHHSLs for indoor air and soil gas. Based on the conclusions of the HHRH, Shell will propose risk-based cleanup levels. The RA Work Plan also proposes to conduct an Ecological Risk Assessment to characterize the risk to plants and animals. Shell anticipates that ecological risks will be eliminated at the site due to the absence of complete exposure pathways once contaminated soils in the upper six feet of soil in trenches 3 and 6 are replaced with clean materials. Shell submitted a 21 January 2010 Work Plan Addendum (Addendum) to modify the sampling and well installation locations proposed in the MW Work Plan. The Addendum proposes to • relocate the Trench 3 deep boring from near boring B-69 to near boring B-18 because TPHc was non-detect in a groundwater sample collected from 155 feet bgs in B-69 but was detected at 234,000 micrograms per liter (ug/L) at 36 feet bgs in B-18, • eliminate one shallow monitoring well previously proposed for the Trench 3 area, • collect soil and groundwater samples from the two deepest borings including the so- called sentinel well and one Trench 3 well, and • extend the target depth for the two deepest borings from 155 feet bgs to 172 feet bgs. Our comments on the RA Work Plan and Addendum are presented below. 1. The Water Quality Control Plan for the Central Valley Sacramento and San Joaquin River Basins (Basin Plan) establishes narrative water quality objectives (WQOs) for groundwater Water Quality Control Plan (Basin Plan)for the California Regional Water Quality Control Board, Central Valley Region, 4th Edition, Sacramento River and San Joaquin River Basins, revised September 2009