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SASM Unveils Master Plan for Wastewater Treatment Plant’s Next 30 Years

The board of the Sewerage Agency of Southern Marin (SASM), which provides wastewater treatment and sewage disposal for its six member agencies, is set to review the Wastewater Treatment Plant Master Plan, a comprehensive report on all of SASM’s major assets: collection,treatment and conveyance facilities, at its December 18 meeting.

The document, prepared over the past 12 months by Carollo Engineers, will guide the plant’s next 30 years in an effort to plan for expected new legal requirements, protect it from flooding, deal with aging infrastructure, prepare for its future growth needs and incorporate sustainability initiatives.

"The Wastewater Treatment Plant has served the needs of the community for 33 years, but it is clear to us that the plant’s facilities have surpassed their useful life," Board President Lew Kious said. "By committing the improvements and policies outlined in the Master Plan, we will be in much better position to provide wastewater services to our community and protect the environment going forward.”

The SASM board, comprised of board members of each of its six member agencies – the City of Mill Valley, the Tamalpais Community Services District and the Alto, Almonte, Homestead Valley and Richardson Bay sanitary districts – reviewed the Master Plan at its meeting on September 18, and is expected to take action on the document at the December 18 meeting.

Each Member Agency owns, operates, and maintains its respective sanitary sewer collection system. The SASM Joint Powers Agreement owns and operates the Wastewater Treatment Plant,which is located at 450 Sycamore Avenue in Mill Valley.

“This Master Plan is a critical component of managing our Wastewater Treatment Plant for the next several decades,” said Mark Grushayev, the manager of the Wastewater Treatment Plant. “This document develops a road map for the next 30 years of Wastewater Treatment Plant improvements, including a list of necessary projects, an implementation schedule, and cost estimates. It is needed to ensure that capital fundsare properly allocated to improvements that will benefit SASM in both the short and long term.”

The creation of the Master Plan had the following primary objectives:

  1. Evaluate the plant’s existing treatment processes in terms of their capability of reliably meeting existing discharge requirements.
  2. Evaluate the existing treatment system to meet potential future discharge requirements, such as stricter nutrient limits or reducing blending during wet weather flows.
  3. Develop a prioritized 25-year capital improvements program (CIP) that phases in projects and results in reasonable customer rate impacts.
  4. Examine and recommend sustainable elements and strategies, which can be incorporated into the proposed CIP, that are complementary to SASM’s policy initiatives.

Aging Infrastructure
The Wastewater Treatment Plant was built in 1954, was significantly expanded in 1984, and was subject to a number of smaller upgrade projects over the years since,including an expansion of the equalization basin in 2012.

The consultant assessed the physical condition of the entire plant in creating the Master Plan, including all existing mechanical and electrical equipment and structures. The process included estimates of when equipment and facilities will need to be replaced.

“The overall findings of the condition assessment are that many of the Wastewater Treatment Plant structures and equipment are nearing the end of their useful life,” Carollo concluded. “Collectively, if the aging facilities are allowed to continue to deteriorate without improvements,the ability of the Wastewater Treatment Plant to meet current discharge requirements will be jeopardized.”

Infiltration and Inflow
The Master Plan also pointed to infiltration and inflow (I&I), an additional burden during wet weather placed on the sewer system and the plant caused by system leaks and defects in service laterals, as a cause for concern.But the Master Plan concluded that

Because SASM and its member agencies are actively pursuing ways to reduce I&I in the sewer system, the burden on the sewer system during wet weather is not expected to increase.

Legal Requirements
The Master Plan also incorporates the requirements of the National Pollutant Discharge Elimination System (NPDES) permit program, under the auspices of the Clean Water Act. Those requirements call for specific tasks to improve wet weather management and reduce the plant’s “blending of primary effluent with secondary effluent during wet weather events for the foreseeable future.”

State agencies have also recently approved permits throughout California with stricter discharge limits for ammonia, nitrogen, and phosphorous, so the Master Plan provides methods for complying with stricter nutrient limits in the future.

Flooding
Due to 100-year flood events and sea level rise, the Wastewater Treatment Plant is at risk of flooding, the Master Plan concluded. The consultant recommended building a berm around the northern and western parts of the plant in coordination with local and regional flood protection measures currently being studied by the Marin County Flood Control and Water Conservation District.

Sustainability
The Master Plan concluded that improving the reliability and the performance of the Wastewater Treatment Plant benefited the environment by reducing pollutants in the San Francisco Bay. It also identified a number of sustainability initiatives at the plant, including the installation of high-efficiency outdoor lighting, more efficient equipment and hydraulic and treatment systems and expanded recycled water systems.

Capital Improvement Projects (CIPs)
To increase the plant’s capacity to meet future population growth, comply with additional permit requirements, maintain overall reliability, reduce the risk of flooding, incorporate sustainable initiatives and the fact that“many of the Wastewater Treatment Plant facilities and equipment are nearing the end of their useful lives,” the Master Plan calls for $26million in capital improvement projects in initial improvements (over the next five to seven years), and another $20 million in CIPs over the 15 years after that.

Once the Master Plan is approved, Carollo Engineers and City staff will develop a financial study to identify proposed sewer rate changes to fund the implementation of the Master Plan, followed by the SASM board’s eventual adoption of the recommended 5-year Capital Improvement Plan.

Click here for more information on the Sewerage Agency of Southern Marin and the Wastewater Treatment Plant.

The SASM Board of Commissioners meets at 7 p.m. on Thursday, December 18 in the conference room at the SASM office at 450 Sycamore Avenue. Please send your comments about the Master Plan to sasm@cityofmillvalley.org.