ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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program defined as the primary data source for a site was the program possessing the longest from dry/below normal water years were available for analysis. Data from dry/below normal monitoring history at the particular location. If data from the primary data source were not water years reflect different water quality conditions in the Delta relative to conditions observed available for a particular parameter at a particular site,then data from a secondary and/or tertiary during wet or above normal water years. San Joaquin River water quality and flow conditions data source were used. In an effort to compile as large a data set as possible for a particular characteristic of dry/below normal water years are expected to reflect future San Joaquin River parameter at a particular monitoring site,data from more than one monitoring program were conditions during rainfall-limited time periods due to the actions set forth in the Water Quality often combined when appropriate to provide an extended data set. These secondary and tertiary Control Plan for the San Francisco Bay/Sacramento-San Joaquin Delta Estuary(1995 Bay-Delta data sources acted to"fill in"data gaps that exist in the primary program's monitoring record at a Plan;SWRCB,1995)and the Revised Water Right Decision 1641(SWRCB,2000). particular location. So as not to unfairly weight certain sample collection dates by including The 1995 Bay-Delta Plan sets forth flow objectives to control declines in aquatic resources— more than one data point(coming from multiple monitoring programs)for any single calendar namely,fisheries—experienced in the Bay-Delta Estuary in recent decades,in addition to date,data from non-primary monitoring programs were omitted from the data set used for providing upstream-and within-Delta management strategies for the protection of beneficial uses statistical analysis. For example,on the occasion that a particular monitoring location possessed that involve salinity,water project operations,and DO. San Joaquin River at Vernalis flow three DO measurements taken on the same date,only a single DO measurement was included in objectives contained in the 1995 Bay-Delta Plan require spring and fall flows in the river to the final data set. The single DO measurement chosen for analysis was taken from the support spring out-migration and fall spawning of salmonids,respectively. Information gathered monitoring program acting as the primary data source for the site. Excluding the other two DO by parties during the limited-term Revised Water Rights Decision 1641(in effect through 20 10) measurements avoided the skewing of the statistical analysis since most monitoring dates were will allow the State Water Board to further review Vernalis flow objectives in terms of timing only represented by a single environmental measurement from a single monitoring program. and magnitude during a future review of the 1995 Bay-Delta Plan. Irrespective of final numeric Data were also excluded from use where analyte detection,analytical method,and detection limit flow objectives for the San Joaquin River at Vernalis that may be set forth in a future Bay-Delta were not documented sufficiently in a monitoring program's original raw data set. Plan,future flow objectives will provide flows similar to or greater than those observed during Water Year Hydrologic Classification dry water years,and not typical of those historically experienced during critical water years,as a means of protecting the aquatic life and water supply beneficial uses of the Bay-Delta Estuary. Data for the 18 water quality parameters measured at selected sites in the project area(see Table 7)were compiled and summary statistics calculated to provide historic surface water quality Table 9: Hydrologic Classification of Years 1990 information for two different water year types:critical years and dry/below normal years. Even through 2006 by Water Year Type though dry and below normal water years are distinct hydrologic classifications under the California Department of Water Resources hydrologic classification scheme(see Figure 4),they Water Year are grouped together in the current analysis as a"dry/below normal"water year type due to the Water Year Type (Oct.1—Sept.30) grouping of data required to produce as large a water quality data set as possible. The analysis of 1990 water quality data for two distinct water year hydrologic classifications—critical and dry/below 1991 normal—provides information upon which to estimate future water quality conditions in the Critical 1992 project area under the widely variable hydrologic conditions experienced in California's Central 1994 Valley. Critical and dry/below normal water years represent worse case conditions for most 2001 parameters as they relate to the impact of WQCF discharge on Delta water quality as compared to impacts measured during a wet or above normal water year. The current near-and far-field Dry 2002 water quality impacts assessments were designed to estimate the incremental change in water 2004 quality within the project area with an increase in WQCF effluent flowrate from the current Below Normal 2003 permitted 9.87 MGD(ADWF)to the proposed 27 MGD(ADWF). The greatest incremental 1999 change in surface water quality conditions in the San Joaquin River and Delta would likely occur Above Normal 2000 when WQCF effluent is discharged to a system with comparatively lower ambient pollutant 1993 concentrations and diminished flows such as those observed during critical and dry/below 1995 normal water years. 1996 Using California Department of Water Resources water year hydrologic classifications for the Wet 1997 San Joaquin Valley(see Figure 4),water quality data collected during specific water years were selected to determine baseline surface water quality in the project area during critical and 1995 dry/below normal water years. Table 9 lists the water year designations and relevant time 2005 periods for the years 1990 through 2006. With regard to the constituents selected for near-field 2006 impact assessments in the project area(see Table 7),only San Joaquin River water quality data City of Manteca Antidegradation Analysis 27 June 2007 City of Manteca Antidegradation Analysis 28 June 2007