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Copies of these reports are available for review at the City of Manteca Pubic Works Department during normal
<br /> business hours(i.e., 8 a.m. to 5 p.m.). The proposed project would result in an increase in the quantity of treated
<br /> effluent discharged from the Manteca WQCF into the San Joaquin River through the existing and proposed side-
<br /> bank outfall located approximately one mile upstream of the Mossdale Bridge near the intersection of Interstate 5
<br /> and Highway 120. The future increased effluent discharge quantity from the WQCF could affect receiving water
<br /> quality near the point of discharge and in downstream reaches of the San Joaquin River and the. This section
<br /> evaluates the impacts to the beneficial uses of the lower portions of the San Joaquin River and the Delta that could
<br /> result from project-related changes to the near-field and downstream water quality. Potential impacts to fisheries
<br /> and aquatic biological resources of the lower San Joaquin River and Delta are discussed in Section 4.13,
<br /> "Fisheries and Aquatic Resources,"of this DEIR.
<br /> 4.9.1 ENVIRONMENTAL SETTING
<br /> HYDROLOGY AND DRAINAGE
<br /> Sacramento—San Joaquin Delta
<br /> The Sacramento—San Joaquin Delta(Delta)forms the lowest part of the Central Valley, lying between the
<br /> Sacramento and San Joaquin rivers and extending inland from the confluence of the two rivers to Sacramento and
<br /> Stockton. The Delta is roughly bordered by the cities of Sacramento, Stockton,Tracy, and Pittsburg. Other cities
<br /> within the Delta include Manteca,Lathrop,Antioch,Brentwood,Rio Vista, and Isleton. There are also about 14-
<br /> unincorporated towns and communities in the Delta. The area receives runoff from over 45 percent of the State's
<br /> land area including flows from 19 tributaries: the Sacramento,McCloud,Butte,Feather,Yuba,Bear,American,
<br /> Merced, San Joaquin,Mokelumne, Cosumnes, Stanislaus, Tuolumne,Chowchilla,Fresno,Kings, Cache,Putah,
<br /> and Calaveras rivers. The Delta is within the jurisdiction of six counties (Alameda, Contra Costa, Sacramento,
<br /> San Joaquin, Solano, and Yolo) and covers approximately 1,500 square miles interlaced with hundreds of miles of
<br /> waterways(Department of Water Resources [DWR] 1993). The Delta is delineated by a legal boundary that
<br /> includes the areas that historically were intertidal, along with supratidal portions of the floodplains of the
<br /> Sacramento and San Joaquin rivers. Today's legal Delta extends between the upper extent of tidal effect(near the
<br /> City of Sacramento on the Sacramento River and Vernalis on the San Joaquin River)and Chipps Island on the
<br /> west(CALFED 1999).
<br /> The 290-mile-long San Joaquin Valley occupies the southern half of the Central Valley and has an average width
<br /> of 130 miles. It covers approximately 32,000 square miles, or one-fifth of the surface area of California. The San
<br /> Joaquin River Basin is bounded on the west by the Coast Ranges and on the east by the Sierra Nevada mountain
<br /> range. The Tulare Lake Basin to the south is normally considered a separate drainage basin,but has contributed
<br /> occasional flood flows and subsurface flows to the San Joaquin River during wet years (DWR 1995). The San
<br /> Joaquin River itself is 330 miles in length and drains a watershed area of 13,540 square miles(CSLC 1993). It
<br /> flows west from the Sierra Nevada,turns sharply north at the center of the valley floor, and flows north through
<br /> the valley into the Sacramento—San Joaquin Delta. San Joaquin River monthly average flow ranges from 400 to
<br /> 1,500 cubic feet per second(cfs) in dry years, 1,500 to 3,500 cfs in normal years and up to 20,000 cfs to 40,000
<br /> cfs in wet years(CALFED 1999). Major tributaries draining the Sierra Nevada and flowing into the San Joaquin
<br /> River include the Fresno, Stanislaus,Merced, and Tuolumne rivers. The San Joaquin River flows through portions
<br /> of Fresno,Madera,Merced, Stanislaus, San Joaquin, Contra Costa, and Sacramento Counties.
<br /> San Joaquin River Basin
<br /> San Joaquin River Basin hydrology is predominantly influenced by tributary inflows, agricultural diversions and
<br /> return flows, and tidal flows. For the purpose of this antidegradation analysis,the Lower San Joaquin River can be
<br /> divided into two main sections based on the presence or absence of tidal flows. The Lower San Joaquin River
<br /> from Mendota Pool to Vernalis receives inflow from a variety of sources including eastside tributaries, dominated
<br /> by reservoir releases;westside tributaries,dominated by agricultural return flows; groundwater recharge; and
<br /> EDAW DER
<br /> Hydrology and Water Quality 4.9-2 City of Manteca
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