Portion Acton-Agua Dulce Unified School District Vasquez High School Mitigated Negative Declaration The Board approved Resolution #98-99.12 to adopt the final Mitigated Negative Declaration and Mitigation Monitoring Program on 5-13-99
VIII. HYDROLOGY AND WATER QUALITY. Would the project:
| a) Violate any water quality standards or waste discharge requirements, | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
The quality of strormwater runoff is regulated under the National Pollution Discharge Elimination System (NPDES). The NDPES stormwater permits provide a mechanism for monitoring the discharge of pollutants and for establishing appropriate controls to minimize the entrance of such pollutants into stormwater runoff. The County of Los Angeles is a co-permittee under the NPDES storm water permit covering Los Angeles County (NPDES No. CAS614001). As co-permittee, the County requires all development projects in its jurisdiction to comply with the NPDES requirements for construction and operations as appropriate.
During construction, the site will be watered according to SCAQMD regulations to reduce PM 10 emissions, resulting in "dirty' runoff. Best Management Practices (BMPs) will be utilized to reduce the extent of this runoff. BMPs may include the following:
Schedule excavation and grading work for dry weather
Use as little water as possible for dust control
Never hose down dirty pavement or impermeable surfaces where
fluids have spilled
Sweep up dry spilled materials immediately; clean up spills
on dirt areas by digging up and properly disposing of contaminated soil; and
report significant spills to the appropriate spill response agencies immediately
Maintain all vehicles and heavy equipment; conduct all
vehicle/equipment maintenance and refueling at one small location - away from
storm drains; perform major maintenance, repair jobs, and vehicle/equipment
washing off site; use drip pans or drop cloths to catch drips and spills, if
draining and replacing motor oil, radiator coolant, or other fluids on site; and
do not use diesel oil to lubricate equipment or parts
Use gravel approaches where truck traffic is frequent to
reduce soil compaction and limit the tracking of sediment into streets
Utilize revegetation, if feasible, for erosion control after
clearing, grading, or excavating
Avoid excavation and grading activities during wet weather
Construct diversion dikes to channel runoff around the site,
and line channels with grass or roughened pavement to reduce velocity of runoff
Cover stockpiles and excavated soil with tarps or plastic
sheeting
Remove existing vegetation only when absolutely necessary;
consider planting temporary vegetation for erosion control on slopes or where
construction is not immediately planned; and plant permanent vegetation as soon
as possible.
With implementation of the BMPs, short-term construction impact will be less than significant.
In compliance with County requirements, an on-site retention basin will be constructed to ensure that no net new peak stormwater runoff from the site will be added to the flow downstream. This retention basin will reduce the sediment load in the water draining from the site by allowing it to settle out. Furthermore, the retention basin will be constructed such that water flowing out of it will be filtered to reduce the amount of debris and other material flowing down Shannon Valley Channel. Compliance with existing NPDES requirements will ensure that long-term operational impacts will be less than significant.
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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)? |
Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
The proposed project will be served by Los Angeles County Waterworks District 37. Los Angeles County Waterworks has indicated that it has the capacity to serve the project with existing facilities (personnel communication, February 25, 1999). No wells that would pump water from the ground directly beneath the site will be installed. No impact will result.
| c) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on or off-site? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
| 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? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
c and d The proposed project will not alter the course of any stream or river. An on-site retention basin will be provided pursuant to Los Angeles County requirements so that no net increase in maximum peak flows from the property takes place. Although the project will result in changes to on-site drainage because of the increase in impermeable surface, drainage flows will be routed into the retention basin such that on-site changes to erosion and siltation patterns will also be minimal. The proposed project will not result in flooding on or off-site. Impact will be less than significant.
| e) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
Runoff from the site will be routed to Shannon Valley Channel, which provides local stormwater drainage. In compliance with County requirements, the proposed project includes an on-site retention basin to ensure no net change in peak stormwater runoff downstream (see a preliminary drainage plan illustrated in Figure 3). Thus, runoff from the project site will not exceed the capacity of local stormwater drainage systems because no net change in peak stormwater runoff will occur.
The proposed project will comply with existing NPDES requirements as applicable (see item a above). As such, no substantial increases in polluted runoff will occur. Impact will be less than significant.
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f) Otherwise substantially degrade water quality? The proposed project is a high school facility that has no potential to substantially degrade water quality in the area. No impact will occur. |
Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
| g) Place housing within a 100-sear flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
| h) Place within a 100-year flood hazard area structures which would impede or redirect flood flows? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
g and h. The proposed project does not include housing. Portions of the site are located within a I00-year flood hazard area as mapped on a federal Flood Insurance Rate Map (Federal Emergency Management Agency, 1980). However, nothing will be constructed within those portions of the flood plain that lie within the 100-year flood hazard area (portions immediately adjacent to Red Rover Mine Road and Escondido Canyon Road). No impact will result.
| Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
Portions of the project site are located in a 100-year flood hazard area as discussed above. However, no structures will be located within this area. No dams or levees are located upstream from the project (Los Angeles County General Plan Program, 1990). No impact will result.
| j) Inundation of seiche, tsunami, or mudflow? | Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
As discussed above, no dams or levees are located upstream from the project site. Thus, there is no danger of a seiche occurring that might inundate the area. The project site is located inland in a mountainous area. Thus, there is no danger of tsunami inundation. The proposed project is located on a relatively level site, and nothing will be located in the flood plain. Thus, there will not be any danger of a mudflow inundating the site. No impact will result.
IX. LAND USE AND PLANNING. Would the project:
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a) Physically divide an established community? |
Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
The proposed project will be built on vacant land. No communities that might be divided are located on this land. All surrounding land are accessible via existing roads and accessways. No impact will result.
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b) Conflict with any applicable land use plan, policy, or regulation of an agency with jurisdiction over the project (including, but not limited to the general plan, specific plan, local coastal program, or zoning ordinance) adopted for the purpose of avoiding or mitigating an environmental effect? |
Potentially Significant Impact | Less Than Significant With mitigation Incorporation | Less Than Significant Impact | No Impact |
The project site is designated for restricted density residential, and residential agricultural uses. The proposed school is a necessary public facility to serve the existing and future residents within the District's boundary, and school uses are considered compatible with residential uses. Building restrictions have been placed on the site because it is subject to hydroconsolidation (Los Angeles County Public Works Department on February 8, 1999) and high noise (Antelope Valley General Plan, 1986). Since the proposed project includes an engineering soils and foundations study for the proposed school campus that will identify site-specific engineering methods for construction, and noise insulation in classrooms and other educational facilities in compliance with the State regulations, this impact will be less than significant.
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