ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

Home Browse Search

SUMMARY OF WATER QUALITY IMPACTS Table 45: Median Nitrate at Select Locations within the Delta for Project Scenarios under Dry/Below Normal Water Year Conditions The wastewater treatment process upgrades associated with the WQCF Phase III expansion, Nitrate(mg/L as N)for WQCF ADWF(MGD) including nitrification-denitrification,tertiary filtration,and UV disinfection facilities,will allow AM it to discharge very high quality tertiary treated effluent to the San Joaquin River. The WQCF Location 0.00) 2.1 tet 9.87 17.5 27 (mg/L) proposes to discharge this same high quality effluent to the river at higher flowrates as the plant SWP Clifton Court Intake 0.40 0.40 0.40 0.41 0.41 0.01 increases its discharge capacity from the currently permitted 9.87 MGD(ADWF)to 27 MGD (ADWF). The near-field and far-field water quality impact assessments presented in the CVP DMC Intake No Data previous two sections of this report show that the proposed increase in WQCF discharge capacity CCWD Intake at Rock Slough 0.22 0.22 0.22 0.22 0.22 <0.01 to the San Joaquin River will generally have very minor impacts on the water quality of the San CCWD Intake at Old River No Data Joaquin River and Delta,with the exception of a near-field exceedance of the U.S.EPA chronic San Joaquin River at Light 18 0.61 0.61 0.61 0.62 0.63 0.02 ambient water quality criterion(87 itg/L)for total aluminum(USEPA,2002)and possible Stockton Turning Basin 1.56 1.57 1.59 1.61 1.64 0.05 excursions to Thermal Plan objectives. The exceedance of the aluminum water quality objective in the receiving water is the result of the ambient levels of the parameter already exceeding (1)Estimated water quality the selected location without effluent stream of the CF discharge.scar a xceeances of (2)The WQCF ADWF duringg the modeled critical water yearr was as 3.5 MGD.Values listed represent the median observed at the standards upstream Q g Edf Thermal Planobjectives will be location. mitigated as necessary(e.g.,through the construction of an effluent cooling tower)based on the (3)Incremental change between build-out(27 MGD(ADWF))and current permitted condition(9.87 MGD(ADWF)). expert opinion of a fisheries biologist charged with determining the significance of the WQCF thermal plume to migrating salmonids and other resident fish species. Comparison to Water Ouality Objectives: The basis for EC water quality objectives in the The City recently completed a WER study(City of Manteca,2007)to identify an appropriate Delta is the Water Quality Control Plan for the San Francisco Bay/Sacramento-San Joaquin site-specific water quality objective for aluminum in the San Joaquin River that is both Delta Estuary(SWRCB,1995). Among the far-field sites considered,EC objectives exist only sufficiently protective of aquatic life and identifies available assimilative capacity for aluminum for the Clifton Court and DMC Intakes. A year-round objective of 1,000µmhos/cm applies to in the river under which the WQCF can discharge its effluent. The study indicates that a WER both export sites. The median EC levels at the two locations are well below the objective in of 22.7 in scientifically defendable. To this end,the next lowest water quality standard for critical water years and the incremental change in water quality due to the project is generally 1 aluminum(Title 22 Secondary MCL of 200µg/L)may be applicable to WQCF effluent. Title 22 µmho/cm or less. Secondary MCLS are set to evaluate potable water that has received treatment,including filtration that generally removes the particulate materials from the water,leaving essentially only There are no established water quality objectives for DOC in the Delta. the dissolved fraction. However,Title 22 standards do not directly specify whether the total or dissolved phase should be considered. Applying Secondary MCLS directly to surface water The Water Quality Objective for nitrate is from the Title 22 primary drinking water MCL of 10 warrants consideration in that only the dissolved fraction would ultimately pass through a mg/L as N. At all modeled far-field locations,the median nitrate levels are expected to be well drinking water treatment plant. While DHS has recently stated that application of Secondary below the MCL value,and changes to nitrate levels in the Delta as a result of the proposed MCLS as dissolved is sufficient to protect municipal and drinking water uses,it has be the project are estimated to be generally less than 0.02 mg/L as N. Regional Water Board's policy to apply it as a total concentration objective to be protective of Evaluation: The proposed project does not affect Delta water quality to a noticeable degree. taste and odor for direct consumption of San Joaquin River water. Most importantly,an increase Results from the hydrologic analysis indicate that implementing the proposed project will not in WQCF permitted discharge capacity from 9.87 MGD(ADWF)to 27 MGD(ADWF)does not lead to appreciable levels of WQCF effluent in the Delta. Because the WQCF effluent is of high negatively impact the San Joaquin River with regard to this parameter,and in fact will decrease quality,and is highly diluted by the time it reaches the Delta far-field locations of interest,the total aluminum concentrations in the receiving water. project is anticipated to have minimal impact on Delta water quality. The Thermal Plan objectives are slightly exceeded for the currently permitted discharge of 9.87 MGD(ADWF);however,an evaluation of the impacts of the thermal plume reveals that there Implementing the proposed project is expected to have little impact on the EC levels in the Delta. are no significant impacts of the plume and a limited exception is being sought for the WQCF. Levels of DOC are not predicted to change noticeably in the Delta as a result of the project. Increasing the effluent flowrate will increase the thermal plume,resulting in exceedance of both Typical changes in DOC levels will be less than 0.02 mg/L with the biggest change being 0.08 the 1°F temperature differential over less than 25%of the cross section,and 4°F differential mg/L. anywhere objectives in the Thermal Plan. Because the Thermal Plan objectives are exceeded, In summary,only a small fraction of high quality WQCF effluent will be present throughout the the characteristics of the WQCF plume need to be evaluated for the level of impact on aquatic Delta,thus there will be little change in Delta water quality due to implementation of the project. life. If the plume is found to not impact the aquatic life within the San Joaquin River,then an exception to the Thermal Plan will be required. If the plume is determined to impact aquatic life in the San Joaquin River,then the City is prepared to design,construct,install,and operate a City of Manteca Antidegradation Analysis 95 June 2007 City of Manteca Antidegradation Analysis 96 June 2007