New pipes to help sewage flow in San Mateo 

Installation of two new pipes to help the flow of wastewater in San Mateo could begin this summer if environmental review and designs are approved by spring.

Larry Patterson, director of San Mateo’s Department of Public Works, said both pipes would be a second source of transporting water to the city’s treatment plant during heavy rainstorms.

The work is a result of the city receiving a cease-and-desist order last year to control the excess flows in the system during the winter, deputy director Darla Reams said.

Reams said the city has been aware of flooding in its streets for years, but the order from the state moved planning along quicker than expected.

“We’d been working on a plan for 10 years,” Reams said. “We knew we were having overflows in the winter, which is bad. It just became a high priority.”

San Mateo has put together a 30-year plan that will upgrade systems and improve capacity for an estimated cost of $200 million. The entire upgrade will include new pipes and detention ponds at the main plant, where water can be stored during a storm and treated after the rain subsides.

Patterson said the project will be paid for through an increase in sewer-user rates. Those rates, an estimated 9 percent increase, have already gone into effect.

Two main lines that will help add capacity are being considered under environmental review, but Patterson said he hopes those projects can start this summer.

The pipes will be an additional line that brings water to the plant. One collects water from the Delaware Street area and is known as the southern trunk line; the other is near Los Prados Street in southern San Mateo, known as the Los Prados trunk line, Patterson said.

It is unknown if the work to either line will disrupt traffic, Patterson said. Work on the two lines is expected to last up to 12 months.

Reams said in the past, Delaware Street residents and commuters were subject to flooding during high rains, but since the cease-and-desist order was issued, the city was given the OK to increase capacity during high-flow periods in order to clear the streets and prevent flooding.

“Some residents have probably already noticed an immediate change,” she said. “Raw sewage is not something you want to be in contact with. It’s better for the community to not have that sewage in the rainwater and in the streets.”

Wastewater system

30: Years in upgrade plan
$200 million: Projected cost of upgrades
9%: Rate increase for users
28,000: Connections
2: Pipelines to be replaced this summer

Source: San Mateo Department of Public Works

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