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Harvest-Lathrop Composting Facility - 6 - 7 February 2018 San Joaquin County 4. FACILITY TIER CLASIFICATION Based on the information submitted by the Discharger and confirmed by Central Valley Water Board staff, the Facility is classified as Tier II as defined by the General Order. 6. COMPLIANCE WITH COMPOSTING PAD SPECIFICATIONS The General Order provides minimum specifications for design, construction, and operation of Tier II facilities working surfaces. Working surfaces must be capable of resisting damage from the movement of equipment and weight of piles, and have a hydraulic conductivity of 1.0 x 10-5 centimeters per second (cm/s) or less. The Discharger stated in the 2018 Revised Final Technical Report that they shall comply with the General Order requirements for working surfaces used in composting operations including but not limited to designing and constructing such working surfaces with minimum one-foot thick Class 2 aggregate base modified with on-site fine grained soil compacted to minimum 95% maximum dry density achieving a hydraulic conductivity of 1.0 x 10-5 centimeters per second (cm/s) or less. Therefore, all composting operations shall be conducted on working surfaces constructed with minimum one-foot thick layer as described above having a hydraulic conductivity of 1.0 x 10-5 centimeters per second (cm/s) or less as shown in Attachment D. The Discharger's maintenance of the working surfaces shall include periodically surveying the working surfaces to ensure: a. Drainage grades are maintained at minimum 1% grade to facilitate drainage and minimize ponding to reduce infiltration of liquids; b. Localized ponding does not occur due to operations, settlement, etc.; and c. The low permeability working surface thickness is maintained to at least 1-foot at all times. Repairs to the working surface shall be submitted as part of the Discharger's Annual Monitoring and Maintenance Report and shall include construction quality assurance that the materials and methods used to repair the working surface ensures that the hydraulic conductivity of the repair does not exceed 1.0 x 10-5 centimeters per second (cm/s). The Discharger shall also maintain the working surface such that it provides year round equipment access to feedstock, additives, amendments, and compost (active, curing, and final product) without damage to the working surfaces and containment structures. 6. COMPLIANCE WITH COMPOST WASTEWATER POND SPECIFICATIONS Detention ponds must be designed, constructed, operated, and maintained to meet a hydraulic conductivity of 1.0 x 10-6 cm/s or less. Detention ponds must be designed and constructed with a pan lysimeter monitoring device under the lowest point of the pond, or an equivalent engineered alternative specified in the NOI and/or a technical report, and approved by the Regional Water Board. Also, detention ponds must be designed, constructed, and maintained (Pond Sizing) to prevent conditions contributing to, causing, or threatening to cause contamination, pollution, or nuisance, and must be capable of containing, without overflow or overtopping (taking into consideration the crest of wind- driven waves and water reused in the composting operation), all runoff from the working surfaces in addition to precipitation that falls into the detention pond from a 25-year, 24-hour peak storm event at a minimum, or equivalent alternative approved by the Regional Water Sra 1-4