STATE OF CALIFORNIA

CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD

SAN FRANCISCO BAY REGION

STAFF SUMMARY REPORT (Ken Katen)

MEETING DATE: November 28, 2001April 16, 2003

ITEM: 185.A.

SUBJECT: CITY OF MILLBRAE, WATER POLLUTION CONTROL PLANT, MILLBRAE, SAN MATEO COUNTYNOVATO SANITARY DISTRICT, NOVATO, MARIN COUNTY – Reissuance Amendment of NPDES Permit

CHRONOLOGY: April 1994May 25, 1999 – Permit reissued

January 1995 – Permit amended

DISCUSSION:

Novato Sanitary District (District) owns and operates two wastewater treatment plants, the Ignacio Treatment Plant and the Novato Treatment Plant. The treatment plants use a combined outfall into to the intertidal mud flats of San Pablo Bay. adjacent to the former Hamilton Air Force Base. This discharge is classified as a shallow water discharge. During the discharge season (September 1 – May 31) annually) the District discharges an annual average dry weather flow of about 5.4 million gallons a day of fully treated, disinfected, dechlorinated wastewater through a multi-port diffuser about 950 feet offshore. Between June 1 and August 31, annually, the effluent is held in reclamation ponds for sprinkler irrigation on District-controlled pasture lands.

In 1999, the District petitioned their permit to the State Board, and it is currently in abeyance.

In 2002, the District requested certain amendments to the existing NPDES permit. The amendments requested by the District are consistent with NPDES permits adopted for other, similar treatment plants. With this permit amendment the District plans to withdraw their pending petition at the State Board.

This permit amendment proposes the following:

1.  re-evaluates the need for effluent limits for copper, nickel and mercury based on recent effluent data and the SIP;

2.  re-calculates final water-quality based effluent limits for copper and mercury based on the SIP;

3.  omits the nickel effluent limit as no reasonable potential was triggered;

4.  gives a new performance-based effluent limit for mercury based on the 2001 Pooled Mercury Staff Report;

5.  moves the compliance point for ammonia to the combined outfall to be consistent with how other water-quality based effluent limits are monitored.

6. 

The attached permit amendment proposes final effluent limits for copper and mercury, and interim effluent limits for these pollutants. It also continues the current permit’s mass discharge limitation for mercury. Finally, it changes the monitoring point for compliance with the ammonia effluent limitation from the individual plants’ discharges to the combined outfall. The attached permit amendment also increases the monitoring frequency for total suspended solids in effluent and influent from once per week and three times per week, respectively, to five times per week in both influent and effluent, increases the monitoring for biochemical oxygen demand (BOD) in influent from once per week to three times per week, and decreases the monitoring frequency for settleable matter from five times per week to monthly.

The City of Millbrae, Water Pollution Control Plant, currently processes an average dry weather flow of about 2.2 million gallons per day (MGD) of treated wastewater. The present service area population is approximately 22,000 within the City of Millbrae. Fully treated and disinfected wastewater is discharged into the North Bayside System Unit (NBSU) joint force main, thence to the NBSU dechlorination facility in South San Francisco and discharge through the NBSU outfall. Dechlorinated combined effluent is discharged into Lower San Francisco Bay northeast of Point San Bruno through a submerged deep water diffuser located 5,300 feet offshore at a depth of 20 feet beneath mean lower low water.

The attached Tentative Order proposes effluent limitations for the following pollutants: copper, lead, mercury, nickel, zinc, cyanide, TCDD equivalents (dioxin and dioxin-like compounds), tetrachloroethylene, bis(2 ethylhexyl)phthalate, 4,4-DDE, dieldrin, and PCBs. Interim limits are proposed for copper, mercury, TCDD equivalents, cyanide, tetrachloroethylene, bis(2 ethylhexyl)phthalate, and PCBs. The proposed permit has fewer toxic effluent limits than the previous permit because no reasonable potential was found for other pollutants using the State Implementation Policy methodology.

Written cComments were submitted by the City of Millbrae Novato Sanitarythe District, and wand the Bay Area Clean Water Agencies. Most of the comments are similar to those for the permits considered by the Board in recent months. We have responded to them in the Response to Comments.

RECOMMEN -

DATION: Adoption of the Tentative Order

File No. 2159.5022 (KK)2179.7019

Appendices:

A.: Tentative Order

B.  Fact Sheet

C.  Comments

D.  Response to Comments

E.  E. Facility Location Map