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Valley Organics, Inc. - 2 - 25 April 2007 V evidence at a nearby site the depth to groundwater is approximately 15 feet below ground surface. This would also provide limited protection of the groundwater resource. Based on our current understanding of the operation and the potential to generate leachate, the documented permeabilities of the underlying soils, and proximity to groundwater staff is recommending Valley Organics, Inc., make the following operational changes to protect surface and groundwater associated with the proposed operation: In the composting and storage area pads where runoff that has come in direct contact with the composting piles and leachate is generated by water percolating through the piles, a low hydraulic conductivity layer should be constructed. Below are several recommendations for that layer: a. Asphalt of sufficient thickness to support equipment without damage. b. Concrete (with steel reinforcement). c. A synthetic geomembrane of at least 60-mil thickness. d. One-foot of compacted clay with maximum hydraulic conductivity of 1x10-6 cm/s and protection from desiccation. e. An equivalent or better, engineered alternative. Runoff retention basins and washwater basins that will contain runoff from the compositing piles and leachate from those piles are also required to include one of the following: a. A liner system that includes a synthetic geomembrane of at least 60-mil thickness or a composite liner system consisting of a synthetic geomembrane of at least 60-mil thickness and one-foot of compacted clay with maximum hydraulic conductivity of 1x10-6 cm/s (or geosynthetic clay liner), depending on site-specific conditions (such as threat to water quality from the feedstock and Additives to be used, depth to groundwater, hydraulic conductivity of native soils, and background groundwater quality). b. An equivalent or better, engineered alternative liner system. Groundwater beneath the site must also be monitored to investigate the impact of a waste discharge on waters of the state. Groundwater beneath the site shall be monitored using a minimum of three groundwater monitoring wells. One groundwater monitoring well shall be installed up gradient of the composting facility and two wells installed downgradient of the facility. Groundwater monitoring wells shall be installed in accordance with the Requirements for Monitoring Well Installation Workplans, attached, and San Joaquin County Environmental Health Services guidelines. The RWD is comprised of Form 200 Application/Report of Waste Discharge General Information, a filing fee, and answers to the Additional Questions. The RWD, at a minimum, shall address the Additional Questions; it shall also include any additional information required to explain the site-specific processes. The answers to the Additional Questions shall be in the form of a technical report prepared by a California Registered Engineer.