ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Executive Summary indicates that a WER of 22.7 in scientifically defendable. To this end,the next lowest water quality standard for aluminum(Title 22 Secondary Maximum Contaminant Level(MCL)of 200 The City of Manteca(City)has requested the Central Valley Regional Water Quality Control pg/L)may be applicable to WQCF effluent. Title 22 Secondary MCLS are set to evaluate Board(Regional Water Board)to increase the NPDES-permitted capacity of its Wastewater potable water that has received treatment,including filtration that generally removes the Quality Control Facility(WQCF)to 27 million gallons per day(MGD)average dry weather flow particulate materials from the water,leaving essentially only the dissolved fraction. However, (ADWF)from the current permitted discharge capacity of 9.87 MGD(ADWF). The City Title 22 standards do not directly specify whether the total or dissolved phase should be requests the additional discharge capacity to accommodate planned community growth and considered. Applying Secondary MCLS directly to surface water warrants consideration in that development. The State's Porter-Cologne Water Quality Control Act requires that waters of the only the dissolved fraction would ultimately pass through a drinking water treatment plant. State be regulated so as to maintain the highest water quality that is reasonable. The State Water While the California Department of Health Services(DHS)has recently stated that application of Resources Control Board's(State Water Board)Antidegradation Policy(Resolution 68-16) Secondary MCLS as dissolved is sufficient to protect municipal and drinking water uses,it has be requires that the quality of existing high quality waters be maintained unless it has been the Regional Water Board's policy to apply it as a total concentration objective to be protective demonstrated that any change will be consistent with the maximum benefit to the people of the of taste and odor for direct consumption of San Joaquin River water. Most importantly,an State,will not unreasonably affect present and anticipated beneficial uses,and will not result in increase in WQCF permitted discharge capacity from 9.87 MGD(ADWF)to 27 MGD(ADWF) water quality less than that prescribed in State policies. The policy also requires that dischargers does not negatively impact the San Joaquin River with regard to this parameter,and in fact will proposing to increase their discharge to high quality waters employ best practicable treatment or decrease total aluminum concentrations in the receiving water. control to assure the highest water quality that is reasonable. The Federal Antidegradation The Thermal Plan objectives are slightly exceeded for the currently permitted discharge of 9.87 Policy requires that existing high quality waters be maintained unless a lowering of water quality MGD(ADWF);however,an evaluation of the impacts of the thermal plume reveals that there is necessary to accommodate important economic and social development. are no significant impacts of the plume and a limited exception is being sought for the WQCF. The purpose of this antidegradation analysis is to demonstrate that the requested increase in Increasing the effluent flowrate will increase the thermal plume,resulting in exceedance of both permitted capacity is consistent with the Porter-Cologne Act and State and Federal the I°F temperature differential over less than 25%of the cross section,and 4°F differential antidegradation policies. anywhere objectives in the Thermal Plan. Because the Thermal Plan objectives are exceeded, the characteristics of the WQCF plume need to be evaluated for the level of impact on aquatic WATER QUALITY IMPACTS OF AN INCREASE IN PERMITTED CAPACITY life. If the plume is found to not impact the aquatic life within the San Joaquin River,then an The wastewater treatment process upgrades associated with the WQCF Phase III expansion, exception to the Thermal Plan will be required. If the plume is determined to impact aquatic life including nitrification-denitrification,tertiary filtration,and ultraviolet(UV)disinfection in the San Joaquin River,then the City is prepared to design,construct,install,and operate a facilities,will allow it to discharge very high quality tertiary treated effluent to the San Joaquin cooling tower that cools treated effluent prior to its discharge into the San Joaquin River. The River. The WQCF proposes to discharge this same high quality effluent to the river at higher cooling tower would be confirmed to perform at final design specifications prior to operation of flowrates as the plant increases its discharge capacity from the currently permitted 9.87 MGD the WQCF at the proposed expanded capacity. Implementation of a cooling tower would act to (ADWF)to 27 MGD(ADWF). The near-field and far-field water quality impact assessments sufficiently reduce the modeled thermal impacts of the WQCF's non-cooled effluent plume presented in the previous two sections of this report show that the proposed increase in WQCF resulting in no significant adverse thermal effects on fisheries and aquatic resources as a result of discharge capacity to the San Joaquin River will generally have very minor impacts on the water the planned increase in WQCF discharge capacity from the current permitted rate(9.87 MGD quality of the San Joaquin River and Sacramento-San Joaquin Delta(Delta),with the exception (ADWF))to the proposed rate(27 MGD(ADWF)). of a near-field exceedance of the U.S.EPA chronic ambient water quality criterion(87µg/L)for All other near-and far-field constituents considered in this report are expected to exhibit only total aluminum(USEPA,2002)and possible excursions to the Water Quality Control Plan for slight to moderate increases in concentration in the receiving water at well-mixed conditions Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays and Estuaries of downstream of the discharge at the proposed 27 MGD(ADWF)discharge capacity. More California(Thermal Plan;SWRCB,1972). The exceedance of the aluminum water quality importantly,none of these constituents are anticipated to exceed relevant water quality objective in the receiving water is the result of the ambient levels of the parameter already objectives,and on average are estimated to be present at concentrations well below objectives. exceeding standards upstream of the WQCF discharge. Exceedances of Thermal Plan objectives will be mitigated as necessary(e.g.,through the construction of an effluent cooling tower)based COSTS AND BENEFITS OF ALTERNATIVES FOR MAINTAINING EXISTING WATER on the expert opinion of a fisheries biologist charged with determining the significance of the QUALITY WQCF thermal plume to migrating salmonids and other resident fish species. Maintaining existing water quality in the San Joaquin River and the Delta with an increase in The City recently completed a Water Effects Ratio(WER)study(City of Manteca,2007)to WQCF discharge may be approached through effluent-to-land disposal or additional wastewater identify an appropriate site-specific water quality objective for aluminum in the San Joaquin treatment by microfiltration and reverse osmosis(MF/RO). These alternatives each possess River that is both sufficiently protective of aquatic life and identifies available assimilative unique abilities to address water quality constituents of concern and each has distinct capacity for aluminum in the river under which the WQCF can discharge its effluent. The study implementation benefits,liabilities,and costs. In order to maintain existing water quality and City of Manteca Antidegradation Analysis ES-1 June 2007 City of Manteca Antidegradation Analysis ES-11 June 2007