|
REGIONAL WATER BOARD RESPONSE (SWRCB/OCC File A-1846(a) and A-1846(b)) -24-
<br /> PETITIONS FOR REVIEW OF W( DISCHARGE REQUIREMENTS J
<br /> ORDER NO. R5-2007-0036 (NPDE6 NO. CA0079154) AND
<br /> TIME SCHEDULE ORDER NO. R5-2007-0037
<br /> CITY OF TRACY, WASTEWATER TREATMENT PLANT
<br /> that modeled flows could be used to calculate the human health dilution credit. Order
<br /> R5-2007-0036 allows a human health dilution credit based on modeled receiving water flows
<br /> provided by the Discharger. Modeling was performed for a 16-year period, from 1975-1991
<br /> (excluding wet years), with reasonable worst-case assumptions for the operation of South
<br /> Deltatmprovements Program's operable gates. The conservative esttton;of the harmonic
<br /> mean flow was used to calculate a dilution credit using the method prescribed in Table 3 of the
<br /> SIP.
<br /> CONTENTION R: The Order's compliance schedule misapplies Title 22 disinfection
<br /> requirements. Region 5 has, in the past, gone to great lengths to state that Title 22
<br /> Reclamation Requirements do not apply to surface water discharges, but that the science
<br /> used to develop Title 22 has applicable and necessary to protect the beneficial uses of contact
<br /> recreation and irrigated agriculture. The Order requires that. 'By August 1, 2008, or upon
<br /> compliance with Special Provisions V1.C.4.b. whichever is sooner, wastewater discharged to
<br /> Old River shall be oxidized, coagulated, filtered, and adequately disinfected pursuant to the
<br /> DHS reclamation criteria, Title 22 CCR, Division 4, Chapter 3, (Title 22) or equivalent."
<br /> The beneficial uses of Old River include municipal and domestic supply, water contact
<br /> recreation, and agricultural supply, and there is, at times, less than 20:1 dilution. To protect
<br /> these beneficial uses, the Regional Water Board found in Order R5-2007-0036 that the
<br /> wastewater must be disinfected and adequately treated to prevent disease. The principal
<br /> infectious agents (pathogens) that may be present in raw sewage may be classified into three
<br /> broad groups: bacteria, parasites, and viruses. Tertiary treatment, consisting of chemical
<br /> coagulation, sedimentation, and filtration, has been found to remove approximately 99.5% of
<br /> viruses. Filtration is an effective means of reducing viruses and parasites from the waste
<br /> stream. Order R5-2007-0036 requires that the wastewater be treated to tertiary standards
<br /> (filtered), or equivalent, to protect contact recreational and food crop irrigation uses.
<br /> The California Department of Public Health (CDPH) has developed reclamation criteria, CCR,
<br /> Division 4, Chapter 3 (Title 22), for the reuse of wastewater. Title 22 requires that for spray
<br /> irrigation of food crops, parks, playgrounds, schoolyards, and other areas of similar public
<br /> access, wastewater be adequately disinfected, oxidized, coagulated, clarified, and filtered, and
<br /> that the effluent total coliform levels not exceed 2.2 MPN/100 ml as a 7-day median. As
<br /> coliform organisms are living and mobile, it is impracticable to quantify an exact number of
<br /> coliform organisms and to establish weekly average limitations. Instead, coliform organisms
<br /> are measured as a most probable number and regulated based on a 7-day median limitation.
<br /> Title 22 also requires that recycled water used as a source of water supply for non-restricted
<br /> recreational impoundments be disinfected tertiary recycled water that has been subjected to
<br /> conventional treatment. A non-restricted recreational impoundment is defined as "...an
<br /> impoundment of recycled water, in which no limitations are imposed on body-contact water
<br /> recreational activities." Title 22 is not directly applicable to surface waters; however, the
<br /> Regional Water Board found that it was appropriate to apply an equivalent level of treatment
<br />
|