SU0014674 - Laserfiche WebLink

Home Browse Search

MOUNTAIN HOUSE NEIGHBORHOOD"F"PROJECT INITIAL STUDY Mountain House Creek channel, and dredging of the Dredger Cut channel. This work would not be completed under the first phase of the project. Instead,the existing culvert draining to the Dredger Cut would be maintained. As previously stated, this culvert has a capacity of 150 cfs. Water that cannot flow through the Dredger Cut culvert would be discharged into one of two storage areas, termed the West and East Storage Areas. Spillways fitted with stop logs would be used to divide the flow into these storage areas. Large amounts of runoff would be stored in these areas. Existing pumps are available to discharge this water but, under severe storm conditions, these pumps would be inundated and would not function. The Master Drainage Plan assumes that a series of 5,000 gallon-per-minute pumps would be used to evacuate this stored water. The Master Drainage Plan calls for these pumps to be rented and used as an interim measure. There is no mention of the number of pumps or if any sump facilities would have been created for these pumps. The Internal Storm Drainage System Within the boundaries of the project site, major discharge trunk lines along DeAnza Boulevard and Mountain House Parkway would be constructed. These lines would be designed to carry the storm water flows from full buildout of the project. The trunk line along Central Parkway would not be constructed at this time. All of the Neighborhood"F"drainage would be directed into either the DeAnza Boulevard or Mountain House Parkway trunk lines. These lines would carry flows to the junction of Byron Road and Mountain House Creek. The 84-inch trunk lines(see Figure 3)would then cross beneath Byron Road and discharge into a constructed discharge channel. Flows from this discharge channel would then travel either overland and accumulate in the east storage area or make their way to the channel to be either discharged to Old River or accumulate behind the levees. A berm and Swale system would be constructed upslope of Neighborhood"F"(see Figure 3)to intercept overland flow from local areas outside the project site. Flows within this constructed berm and drainage channel would discharge to Mountain House Creek just south of Byron Road. Several small interim improvements to the local drainage system would be made in and around the Neighborhood"F" subdivision. These improvements include additional culverts at Grant Line Road. These culverts would improve the general drainage conditions in and around this area and reduce nuisance type flooding during moderate rainfall events. They would also improve the delivery of off-site runoff into the DeAnza Boulevard trunk line. Environmental Checklist Potentially Significant Potentially Unless Less Than Significant Mitigation Significant No Impact Incorporated Impact Impact HYDROLOGY AND WATER QUALITY. Would the project: a) Violate any water quality standards or waste discharge requirements? . b) Substantially deplete groundwater supplies or interfere substantially with . groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level(e.g.,the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted)? cvoeswmn'1AL=YTNAUNmALMVDY-PARn.Doc(maao) 94 V.J. HYDROLOGY AND WATER QUALITY