The City has a total area of 4.6 square miles and four main drainage areas that convey storm water through the City:
- The primary storm drainage conveyance through the City is Belmont Creek which conveys 60% of the City’s storm runoff.
- Laurel Creek has a 0.78 square mile drainage area in the northwestern portion of the City and discharges to the City of San Mateo.
- O’Neill Slough is located east of Highway 101 and is hydraulically connected to San Francisco Bay.
- Island Park is east of the Highway 101 which drains to a lagoon that connects to Belmont Creek.
The City’s storm infrastructure consist of 28 miles of storm drain pipes and two storm pump stations. There are a number of areas in the City that do not have any storm drain pipes. The existing 28 miles of storm lines are made up of:
- Corrugated Metal Pipe (CMP) [11,300 feet citywide, 2.1 miles]
- Reinforced Concrete Pipe (RCP) [132,800 feet citywide, 14.3 miles]
- High-Density Polyethylene Pipe (HDPE) and Polyvinyl Chloride Pipe (PVC) [61,526 feet citywide, 11.6 miles]
In 2009 the City completed a Storm drainage study which documented the existing City storm drainage system and identified drainage deficiencies. More detailed information can be found in the June 26, 2007 staff report.
The estimated cost to correct the deficiencies were estimated at $44 million. These costs were updated in late 2013 to an estimated $55.6 million as follows:
- Repair and replacement of deficient pipe ($29.3million)
- Installation of new storm pipes, where currently none exist, to help with storm and flooding issues ($20.2 million)
- Installation of Curb & Gutter Improvements ( $3.3 million)
- Improvements to Belmont Creek to convey a 100-year flood event ($2.8 million)
The storm water forecast increases the City’s infrastructure backlog. Addressing infrastructure issues is one of the City’s highest priorities, but also presents a significant challenge given tight budgetary constraints and valid competing priorities.
City of Belmont National Pollutant Discharge Elimination System