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CENTRAL VALLEY WATER BOF ` RESPONSE (SWRCB/OCC File A-1646. -6-
<br /> PETITIONS FOR REVIEW OF VOMTE DISCHARGE REQUIREMENTS
<br /> ORDER NO. R5-2007-0036 (NPDES NO. CA0079154) AND
<br /> TIME SCHEDULE ORDER NO. R5-2007-0037
<br /> CITY OF TRACY, WASTEWATER TREATMENT PLANT
<br /> CONTENTION C: Effluent limits for aluminum, ammonia, chlorine residual, mercury,
<br /> nitrate/nitrite, salinity, and acute toxicity were established in the Tracy Permit based on
<br /> the interpretation of the Basin Plan's narrative toxicity objective or narrative chemical
<br /> constituents objective. The Discharger contends that the Central Valley Water Board
<br /> exceeded its authority by relying on the narrative water quality objectives indefinitely,
<br /> and particularly where ample information exists to allow the State to properly adopt a
<br /> numeric water quality objective; and that water quality based effluent limitations cannot
<br /> be imposed where there is not reasonable potential to cause or contribute to an
<br /> exceedance of a water quality objective.
<br /> The Discharger asserts that there is no reasonable potential for certain constituents based
<br /> on narrative objectives. The Discharger does not specify what limitations this argument
<br /> applies to, other than acute toxicity. The permit provisions the Discharger cites on page
<br /> 12, lines 7-8 of the Petition address limits for aluminum, ammonia, chloride, copper,
<br /> chlorodibromomethane, dichlorobromomethane, dissolved oxygen, electrical conductivity
<br /> (EC), iron, mercury, nitrate, nitrite, oil and grease, pH, temperature, total dissolved solids
<br /> (TDS), and chlorine residual. The effluent limitations for chlorodibromomethane,
<br /> dichlorobromomethane, dissolved oxygen, EC, iron, pH, and temperature are based on
<br /> numeric site-specific objectives in the Basin Plan or based on the CTR. These limitations
<br /> were not based on an interpretation of the Basin Plan's narrative objectives. In addition,
<br /> there are no effluent limitations for oil and grease, TDS, and chloride. Only the effluent
<br /> limits for aluminum, ammonia, nitrate, nitrite, acute toxicity, and chlorine residual are based
<br /> on the toxicity or chemical constituents narrative objectives. Central Valley Water Board
<br /> staff disagree that there was not a demonstration of reasonable potential for these
<br /> constituents in the Tracy Permit.
<br /> Aluminum. See response to Contention F, below.
<br /> Ammonia. Untreated domestic wastewater contains ammonia. Nitrification is a biological
<br /> process that converts ammonia to nitrate, and denitrification is a process that converts
<br /> nitrate to nitrogen gas, which is then released to the atmosphere. At the time the Tracy
<br /> Permit was adopted, the Facility's operation partially nitrified the wastewater, resulting in
<br /> ammonia and nitrate in the discharge. Ammonia is highly toxic to aquatic life. The
<br /> maximum effluent concentration for ammonia (as N) was 42.3 mg/L, while the applicable
<br /> criterion was 1.96 mg/L (ammonia as N). This criterion is from USEPA's 1999 Update of
<br /> Ambient Water Quality Criteria for Ammonia. (See Fact Sheet, p. F-30.) Therefore, the
<br /> effluent has a reasonable potential to cause or contribute to an in-stream excursion above
<br /> the Basin Plan's narrative toxicity objective.
<br /> Nitrate and Nitrite. The discharge from the Facility has a reasonable potential to cause or
<br /> contribute to an in-stream excursion above water quality standards for nitrite and nitrate
<br /> because the Tracy Permit requires the removal of ammonia (i.e., nitrification), which is the
<br /> process of converting ammonia to nitrite and nitrate. Inadequate or incomplete
<br /> denitrification (i.e. process of removing nitrite and nitrate) may result in the discharge of
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