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MOUNTAIN HOUSE NEIGHBORHOOD"F"PROJECT INITIAL STUDY 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. Condition of Approval 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. d) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on-or off-site? The development of the project would increase the amount of impervious surfaces on the site which would substantially increase the amount and rate of runoff leaving Neighborhood"F". Extensive hydrologic and hydraulic studies were completed and synthesized into the Neighborhood"F" Storm Water Report. The report recommends and outlines storm water collection and conveyance facilities. The basis for these facility designs is a hydrologic model. This model was developed using standard methodologies and is considered appropriate for design at this stage of the project. However,no field data were collected to verify the accuracy of this model. This model should be amended and calibrated using real data collected on the site and in the watershed. This data could be collected over the next few rainy seasons and used in model calibration. The calibrated model could then be used to amend the project storm water facility design. Parameters that may be very important to calibrate include the runoff curve numbers and the individual basin lag times. Without accurate data, future storm drainage facilities could be overbuilt, with associated environmental impacts. In addition, future creek restoration efforts may not be properly designed without basic hydrologic field data for Mountain House Creek. Condition of Approval 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 development of flood control measures and habitat protection measures in the creek zone Condition ofApproval 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 an dlorMountain House Community Services District design standards. Condition of Approval HYDRO-7: Asper 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. e) Create or contribute runoff water which would exceed the capacity of existing or planned storm water drainage systems or provide substantial additional sources of polluted runoff? The development of Neighborhood"F"would increase the amount of runoff that currently ponds behind the Old River levee. This would exceed the capacity of the existing pumps and drainage facilities which, C lJOBSSJCUNMAL=YT1NALINfflAL=Y-PART7.D0C(7/27/00) 98 V.J. HYDROLOGY AND WATER QUALITY