Saticoy & Wells Community Plan & Development ... - City Of Ventura

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Saticoy & Wells Community Plan and Code EIRSection 4.8 Hydrology and Water Quality4.8 HYDROLOGY AND WATER QUALITYThis section addresses impacts to local and regional hydrology, as well as temporary and longtermimpacts to surface water and groundwater quality. Water supply impacts are discussed inSection 4.14, Utilities and Service Systems.4.8.1 Settinga. Hydrology. The City of Ventura is located within the western portion of the SantaClara River Basin. The City’s general drainage pattern begins in the hills above of the City andterminates at the Ventura River, the Santa Clara River or the Pacific Ocean. Within the ProjectArea, water is transported through overland flows or by Ventura County Watershed ProtectionDistrict (VCWPD) natural and concrete-lined barrancas. Long Canyon, located in the hills northof the Project Area, drains to Brown Barranca, a drainage that is under the jurisdiction of theVCWPD. Brown Barranca is the primary drainage in the Project Area and transitions between aconcrete lined channel to a heavily vegetated earthen ditch that crosses the Parklands site in asoutheasterly direction from Telegraph Road on the north to the Santa Clara River to the south.Franklin-Wason Barranca transports water from Peppertree Canyon located northeast of theProject Area and partially forms the eastern border of the Project Area near Darling Road. Thisdrainage, like Brown Barranca, also continues south to the Santa Clara River.The Project Area is a predominantly built environment with approximately 300 acres ofundeveloped land previously or currently used for agriculture. Impermeable surfaces in thedeveloped portions of the Project Area prevent water from infiltrating, increasing the amount ofrunoff reaching the storm drainage infrastructure.b. Drainage. The Project Area consists of approximately 1,000 acres that extends fromTelegraph Road to the north down to the Santa Clara River to the south. The Project Areagently slopes to the south toward the Santa Clara River. Project Area elevations range fromabout 240 feet above mean sea level at the northern boundary to approximately 130 feet abovemean sea level in the southern portion of the Project Area. The Project Area is predominantlydeveloped, but also contains approximately 300 acres of agricultural and undeveloped landsand drains overland toward the Santa Clara River via the Brown and Franklin-Wasonbarrancas.c. Flood Hazards. The Federal Emergency Management Agency (FEMA) has definedthe 100- and 500-year flood hazard areas within the Project Area through the publication ofFlood Insurance Rate Maps (FIRMs), which establish base flood heights and flood zones for 100-year and 500-year storm events. The 100-year storm event is defined as a storm that has a 1%probability of occurring in any given year, while a 500-year storm event has a 0.2% chance ofoccurring in any given year. A “floodplain”, also called a flood zone, is the lowland adjacent toa river, lake or ocean and is designated by the frequency of the flood that is large enough tocover it. For example, a 100-year floodplain will be covered by a 100-year flood, while a 500-year floodplain will be covered by a 500-year flood. The “floodway” is the channel of a river orstream plus any adjacent floodplain areas that must be kept free of encroachment so that the100-year flood can be conveyed without substantial (greater than one foot) increases in floodheights. Planning policies typically prohibit urban development, activities, and structures4.8-1City of Ventura
Saticoy & Wells Community Plan and Code EIRSection 4.8 Hydrology and Water Qualitywithin the floodway that will alter the floodway’s ability to convey the 100-year flood.However, development is not usually restricted within the 500-year flood zone because of thelow probability of flood occurrence.As indicated on the FEMA Flood Maps (Figure 4.8-1), portions of the Project Area are locatedwithin the 100- and 500-year floodplains. Currently, Brown Barranca and areas located alongthe barranca are located within a 100-year flood zone (see Figure 4.8-1). Brown Barranca, for themost part, is a stabilized earthen ditch. It is currently deficient for the 100-year storm.However, modifications to the hydrological setting included in the Parklands Specific Planwould eliminate the deficiency of Brown Barranca and revise the flood zone for that area. Areason the north bank of the Santa Clara River, especially in the Southwest Neighborhood are alsolocated within a 100-year flood zone.Dam inundation is also a potential hazard to the Project Area. Table 4.8-1 illustrates those damsthat would have impacts on the Project Area should they fail. All of these dams meet applicablesafety requirements and are inspected by the Division of Dam Safety, California Department ofWater Resources, twice per year to ensure they meet all safety requirements and that necessarymaintenance is performed. The Castaic and Pyramid Dam inundation area lies north of OlivasPark Drive and south of U.S. 101 and SR 126. Dam inundation zones are shown on Figure 4.8-2.Table 4.8-1Existing Dams with the Potential to Affect the Project AreaDamLocationConstructionMaterialCapacity(Acre Feet)Bouquet DamSanta Felicia DamCastaic DamWest fork of Matilija Creekabove Matilija Hot SpringsPiru Creek 5 miles N oftown of PiruCastaic Creek 1 mile NEof town of CastaicEarth Fill 36,505Earth Fill 100,000Earth Fill 325,000Pyramid DamPiru Creek 15 miles N ofCastaicEarth and RockFill179,000Source: McClelland Consultants (West), Inc. Environmental Services, 1989.d. Surface and Groundwater Water Quality. The primary sources of pollution tosurface and groundwater resources include stormwater runoff from paved areas, which cancontain hydrocarbons, sediments, pesticides, herbicides, toxic metals, and coliform bacteria.Seepage from sewage treatment lagoons can further contribute to degraded water quality in theform of elevated nitrate levels. Improperly placed septic tank leach fields can cause similartypes of contamination. Illegal waste dumping can introduce contaminants such as gasoline,pesticides, herbicides, and other harmful chemicals. Agricultural and industrial operationstypically use substances that can affect surface and groundwater quality.4.8-2City of Ventura
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Saticoy & Wells Community Plan & Development ... - City Of Ventura

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