Millbrae’s sewer collection system is in need of significant repair and rehabilitation. During wet weather rain events, rainwater enters the sanitary sewers through cracks and defects (infiltration) and through illegally connected sources such as roof gutter downspouts (inflow). These infiltrations and inflows (I/I) are the major cause of sanitary sewer overflows (SSO), and raise great concerns related to public health and environmental impacts to San Francisco Bay.
Millbrae’s Sewer Modernization Program is a collection of actions and projects designed to remove infiltrations and inflows entering the sewer system, thereby reducing SSO in the future. In implementing the Program, the City is establishing a series of communication pathways to inform residents of the sewer system rehabilitation and improvements needed to reduce and prevent future SSO.
San Francisco Baykeeper Consent Decree
In November 2010, the City of Millbrae entered into a Consent Decree with San Francisco Baykeeper (Baykeeper). The Consent Decree requires the reduction of SSO’s from the City’s sanitary sewer collection system by November 2018.
In accordance with the Consent Decree, the City is working to remove I/I from entering the sewer system and thereby reduce SSO’s in its collection system by:
- Comprehensively inspecting and repairing the collection system sewer pipes and house laterals
- Enhancing collection system maintenance activities
- Providing additional sewer and pumping system capacity to contain and convey peak wet weather flows to the wastewater treatment plant
Consent Decree Requirements
The City has made steady progress in implementing the Consent Decree requirements. Completed work includes:
- Closed Circuit Television inspection of all gravity sewer mains has been completed ahead of schedule
- Investment in excess of $5 million in rehabilitation of the City’s most critical collection system areas
- Increase in preventative maintenance activities on the sewer mains has been effective in reducing SSO’s
- The number of sewer mains on the City’s “Hot Spot Cleaning List” is decreasing
- Completing a Capacity Assurance Report (CAR) identifying the sewer rehabilitation and capacity improvement projects needed to reduce SSOs.
While a number of the Consent Decree’s requirements have been accomplished, the majority of sewer rehabilitation work outlined in the City’s CAR needs to be completed by November 30, 2018 in order to meet legal compliance.
Capacity Assurance Report
In 2010, the City prepared and adopted a Capacity Assurance Report (CAR) that outlined the rehabilitation and capacity improvement projects needed for compliance with the Baykeeper Consent Decree requirement to reduce SSO’s during wet weather events. The CAR was updated in 2014 with increased focus on repair projects and strategies that would both meet Consent Decree requirements and provide sustainable, cost effective, long-term collection system performance.
The 2014 CAR recommends:
- Comprehensive collection system rehabilitation projects in four priority sewer basins
- A capacity upgrade project at the Madrone Pump Station
- Four projects to upgrade the hydraulic capacity of currently undersized sewer mains
When originally prepared, the 2014 CAR estimated the total capital cost of these projects to be $34.2 million. These costs have been updated to April 2017 dollars, and the total cost of these projects is now estimated at $48.6 million.
Sewer System Rehabilitation
As documented in the 2014 CAR, residential sewer lateral connections are a significant source of I/I. If only the publicly-owned sewer laterals are rehabilitated in identified priority basins, I/I is expected to be reduced by 30-50%. If both publicly-owned lower laterals and privately-owned upper laterals are rehabilitated within the priority basins, I/I will be reduced by as much as 70%. This is I/I reduction goal that will allow the City to meet Baykeeper Consent Decree compliance.
The CAR recommends comprehensive rehabilitation of both the public and private laterals in the four priority basins (three in the Madrone basin and one in the Hillcrest basin) because it results in the greatest I/I reduction with the lowest overall program cost to comply with the Consent Decree.
Cost to Millbrae Residents
The total estimated cost needed to comply with the Consent Decree is $48.6 million; $19 million of which is required by the compliance deadline of November 2018. It is proposed that most of these costs will be funded using debt financing with debt principal and interest payments to be paid using revenue from Clean Bay Charges adopted by the Millbrae City Council on July 11, 2017. Debt financing to fund the Wet Weather Program will be issued in three phases:
- Fiscal Year 2017 -2018 in the amount of $19 million
- Fiscal Year 2019-2020 in the amount of $10 million
- Fiscal Year 2021-2022 in the amount of $15 million