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MOUNTAIN HOUSE NEIGHBORHOOD"F"PROJECT INITIAL STUDY Conditions of Approval HYDRO-3:Implementation of the following measures would reduce construction-related erosion and sedimentation impacts to less-than-significant levels: • The project grading plan shall include an approved drainage and erosion control plan to minimize the impacts from erosion and sedimentation during grading. This plan shall conform to all standards adopted by San Joaquin County or Mountain House Community Services District. This plan shall include procedures such as: (1)restricting grading as mandated by the Regional Water Quality Control Board;(2)protecting all finished graded slopes from erosion using such techniques as slope benching,erosion control matting,and hydroseeding;(3)protecting downstream storm drainage inlets from sedimentation;and(4)use of silt fencing to retain sediment on the project site; • Prior to site earthmoving and grading activities,sedimentation basins shall be developed in order to retain sediment on-site as required by the Regional Water Quality Control Board. The sedimentation basins can either be created as temporary basins,or the planned project sediment basins can be constructed and put on-line prior to earthmoving activities. Appropriate sedimentation basins shall be part of the approved drainage and erosion control plan described above. • After construction is completed,all drainage culverts shall be inspected for accumulated sediment. If sediment accumulation has occurred,these drainage structures shall be cleared of debris and sediment. • A precise Winterization Plan shall be developed by the project engineer and shall be approved by the County Engineer and/or the Mountain House Community Services District prior to issuance of grading or building permits. The Winterization Plan shall identify specific locations where on-site water erosion is a threat,and shall identify specific control measures to offset such threats. A project representative,clearly designated in the Winterization Plan,shall be responsible for ensuring identified control measures are implemented and maintained following significant storm events. HYDRO-4: The applicant shall implement the erosion protection features indicated in the concept design of the discharge channel and diversion channel return as per the Neighborhood"F"Drainage Plan. _ HYDRO-5: A rainfall runoff monitoring program shall be instituted for the Mountain House Creek watershed.This program should,at a minimum,include installation of rainfall intensity gages within the watershed and several continuously recording stream flow gages at pertinent places along the creeks. This information can then be used to update the parameters in the hydrologic model to calculate more accurate peak flow estimates as well as provide valuable data for the channel improvement and enhancement of Mountain House Creek. More accurate peak flow estimates allow more precise develo ment of flood control measures and habitat protection measures in the creek zone. HYDRO-6: The project applicant shall incorporate the recommendations as stated in the Neighborhood"F"storm water report into the infrastructure improvement plans prior to approval of the first final map. All designed and constructed storm water facilities shall conform to all applicable County and/or Mountain House Community Services District design standards. HYDRO-7: As per the recommendations in the applicant's Geotechnical Report(CET, 1999),a positive surface drainage of at least 5 percent shall be provided within 10 feet of all building foundations. Elsewhere,a positive surface drainage of at least 2 percent is recommended to allow for rapid removal of surface drainage. HYDRO-8: As per Federal Emergency Management Agency requirements,all constructed berms or levees along Mountain House Creek shall have a minimum of 3 feet of freeboard between the calculated 100-year water surface elevation and top of the berm. Alternatively,the perimeter swale upslope of the Neighborhood"F"development shall maintain 3 feet of freeboard when conveying runoff from the upstream watershed and overflows from Mountain House Creek. One of these requirements shall be incorporated into the infrastructure'improvement plans prior to approval of the fust final ma K. Hazards HAZ-1: The disinfection system for the pool at the Neighborhood Recreation Facility shall be either liquid chlorine,bromine tablets,chlorine tablets,or other non-gaseous chlorine system of disinfection. The use,storage and transport of these materials shall be determined by applicable laws and regulations. Pool staff involved in water quality maintenance shall be educated and trained in the use of chemicals,proper storage and emergency response. The pool operator shall prepare a training manual for review and approval by County fire and/or environmental health personnel. The design of the sanitation system shall be reviewed and approved by the County prior to issuance of the building t for the proposed pool. HAZ-2: Prior to issuance of any grading permits,the applicant shall provide proof for the County Building Department that the demolition of the farmhouse in the northeast comer of the site shall be conducted with proper handling and disposal for materials containing identified asbestos if any. HAZ-3:The Lammersville School District shall comply with any requirements established by the Department of Toxic Substances Control(DTSC)for any hazardous materials at the proposed school site. Proof of such compliance shall be provided to the County Building Department prior to the issuance of buildin permits for the school. C'.VOB.SWC\INMA.L MDY\FINALINRIALMMY-PARTI DOC(7/22/00) 23 III. SUMMARY OF MITIGATION MEASURES