OAKLAND — The city will spend more than $4 million this year to upgrade its sewers, part of a 22-year improvement of its aging system.

The upgrades are required under a 2014 agreement with the Environmental Protection Agency to reduce sewage spills into the bay. That $300 million program is proceeding ahead of schedule, according to the Public Works Department.

The City Council recently approved three contracts for a combined $4.1 million for some of that work, to be completed by fall.

Two of those are for upgrading pipes in Leona Heights, south of Mills College, and on three city blocks in East Oakland off Plymouth Street from 83rd to 87th avenues.

The third contract, the largest at $2.4 million, is to expand capacity at four locations to prevent flooding during heavy storms. This work is needed on Grand Avenue at Harrison Street next to Lake Merritt, along 18th Street from the lake to Park Boulevard, on a block of Maybelle Avenue off MacArthur Boulevard near High Street and a three-block stretch of 61st Street from Vallejo Street to San Pablo Avenue in North Oakland.

Oakland already has installed sensors below manhole covers at a dozen sites where there was a risk of flooding during heavy rains. The sensors were installed as part of the city’s 2014 agreement with the EPA, which sued Oakland and neighboring cities.

That agreement, which also included the East Bay Municipal Utility District and Berkeley, Alameda, Emeryville, Albany, Piedmont and El Cerrito and Kensington’s Stege Sanitary District, settled a 2009 suit by the EPA and California State Water Resources Control Board over sewage overflows and spills into the San Francisco Bay blamed on the condition of thousands of miles of sewage pipes, some a century old or more.

Under terms of the agreement, once sensors were installed, the city had two years to correct any deficiencies they identified.

With the work specified in the $2.4 million contract with Pacific Trenchless, “all of the capacity expansion projects are on track to get done in time,” said Sean Maher, program analyst for the city public works department’s bureau of engineering and construction.

The other two contracts, with Mosto Construction for $394,000 to work on the Plymouth Street sites, and with Pacific Trenchless for $1.3 million to work in Leona Heights, continue the upgrades underway in Oakland since the 2009 lawsuit.

The city already has spent millions upgrading the system. In a statement announcing the consent decree in 2014, the city attorney said Oakland was spending $52 million annually on repairs and upgrades and that under terms of the agreement had committed to spending another $13 million annually, paid for with sewer tax revenue.

Oakland agreed to upgrade 13 miles of sewers annually and, as of the most recent annual report last year, was ahead of pace, with 50 miles completed after three years, Maher said.

For those living close to this summer’s projects, there should be no concern about either flooding or service outages, he said.

Contact Mark Hedin at 510-293-2452, 408-759-2132 or mhedin@bayareanewsgroup.com