Laserfiche WebLink
REGIONAL BOARD RESPONSE(SWRCB/OCC FILE A-1634) • -2- <br /> STATE BOARD DRAFT WATER QUALITY ORDER <br /> PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS <br /> ORDER NOS. R5-2004-0028 AND R5-2004-0029 <br /> CITY OF MANTECA WASTEWATER QUALITY CONTROL FACILITY <br /> The Draft Order's suggested 1,000µS/cm year-round effluent limitation is not necessarily <br /> inconsistent with the direction the Regional Board has taken in developing the TMDL for salt in the <br /> Lower San Joaquin River upstream of Vernalis, because the objectives that apply at Vernalis are <br /> slightly different than those that apply to the southern Delta. The most important difference is that <br /> the Vernalis objective does not include the caveat that is included in the water quality objective for <br /> the southern Delta. <br /> The proposed salinity objectives of 700µS/cm during the irrigation season is appropriate since it is <br /> intended to implement an existing State Water Board objective and the conditions have not yet been <br /> met to allow the 700µS/cm objective to be replaced with 1000µS/cm. On the other hand, requiring <br /> Manteca to comply with the 7001iS/cm objective may not be appropriate if the objective will be <br /> changed to 1,000µS/cm in the short term. A compromise position may be to propose a year round <br /> interim objective of 1,000µS/cm until a TMDL is developed for salinity in the southern Delta or <br /> pending fulfillment of the conditions specified in D-1641. <br /> Another consideration is that the Draft Order does not mention how changing the EC Effluent <br /> Limitations may affect compliance with other salinity water quality objectives. Finding 45 of Order <br /> No. R5-2004-0028 provides discussion of the water quality parameters that are typically indicative of <br /> salinity, including total dissolved solids (TDS), chloride, and EC. Finding 45 provides evidence that <br /> the discharge has reasonable potential to exceed the water quality objectives for all three salinity <br /> parameters. The water quality objectives for salinity are shown in the Table 1, below. <br /> Table 1: Salinit Water Qua]it Ob'ectives <br /> Agricultural Secondary Basin Plan Water <br /> Parameter WQ Goal MCL Quality Objective <br /> EC (uS/cm) 700 900 700 (1 Apr-31 Aug) <br /> 1000 (1 Sep—31 Mar) <br /> TDS (mg/1) 450 500 N/A <br /> Chloride (mg/1) 106 250 N/A <br /> Finding 45 concludes that, "Compliance with the Effluent Limitations for electrical conductivity <br /> based on the Basin Plan seasonal water quality objectives of 700 umhos/cm and 1000 umhos/cm will <br /> be protective of the chloride and TDS recommended levels; therefore, no limitations are included for <br /> chloride and TDS" The Draft Order's proposal would reduce the level of protection for the <br /> Secondary MCL and provide no protection for the Agricultural Water Quality Goal. Both municipal <br /> supply and agriculture irrigation are designated beneficial uses of the receiving water. <br /> 2. Restrictions on Periods of Dischar e I would like to re-emphasizes the Regional Board's <br /> concerns regarding the restrictions on periods of discharge to surface water established in Effluent <br /> Limitations B.8 of Order No. R5-2004-0028. The conclusion of the Draft Order is to change the <br /> restriction from discharging only during outgoing tides to discharging when net downstream flow is <br /> greater than or equal to 0.5 foot per second(fps). The Regional Board does not disagree with <br />