PORTLAND — Capisic Brook flows discreetly through Nason’s Corner.

“It is really overgrown, and to get to it, you have to go through people’s backyards,” city Stormwater Coordinator Doug Roncarati said Jan. 31 during a meeting at Sagamore Village.

The stormwater flowing into Capisic Brook faces fewer physical barriers, which is why Roncorati, city Stormwater Project Manager Justin Pellerin and Ransom Project Engineer Tom Nosal hosted a meeting to discuss a $1 million city project to better filter drainage.

“We want to intercept it at the catch basin before it gets into the stormwater drainage,” Nosal said of contaminants that can include oil, metals, salt, and animal waste.

The “green infrastructure” project would add 30 “bio-retention cells” and other filtering areas near or above storm drains throughout the Portland Housing Authority development.

Pellerin said the project, funded with revenues from the monthly stormwater fund city property owners have been paying for three years, should go out to bid in early spring, with work expected to begin in July.

The work is expected to be finished in spring 2020, with a break during the winter months, Pellerin said.

Capisic Brook, which flows between Sagamore Village and the new Amanda C. Rowe Elementary School, is one of five urban impaired waterways in Portland. Its chief source of pollution is unfiltered stormwater, according to the city meeting presentation.

According to the state Department of Environmental Protection, “a stream is considered impaired if it fails to meet water-quality standards because of effects of stormwater runoff from developed land.”

The brook’s entire watershed, which includes a northern branch flowing from Evergreen Cemetery, is 2.5 miles long and covers 1,500 acres. Roncarati said 31 percent of the watershed is impervious surfaces such as streets, parking lots or sidewalks.

The work at Sagamore Village, including its major intersections, has both curbside and public safety appeal, and will resemble the bio-retention cells installed on Anderson Street in East Bayside.

The cells are actually curbside rain gardens, where a catch basin or outlet is connected to a perforated pipe. Above the pipe is a layer of absorbent material such as sand, compost and topsoil. Planted in the layer are hardy perennials that can withstand periods of extended wet or dry weather.

In the center of the cell is a curb cut to draw the stormwater flow. The cell is designed to absorb an inch of rain, and the placement will also narrow streets and perhaps help slow vehicle traffic.

“Big, wide expanses of pavement let people speed and they are bad for stormwater,” Nosal said.

The project would narrow the intersection of Cabot and Popham streets and also eliminate lanes used for turning at Popham and Purchas, and Popham and Josslyn streets.

The city has been looking at how to protect Capisic Brook since a master plan was accepted by city councilors in 2012. On Aug. 3, 2015, councilors approved an $800,000 purchase of 42.5 acres of land off Warren Avenue for a stormwater treatment system to protect the brook.

The funding came from the fiscal year 2014 capital improvements plan for sewer projects, with bonding repaid through sewer fees.

While not connected to the master plan, the city also spent $1.46 million to dredge Capisic Pond upstream from the Capisic Street bridge. The work cleared away 4.5 acres of invasive growth to restore open water.

David Harry can be reached at 780-9092 or dharry@theforecaster.net. Follow him on Twitter: @DavidHarry8.

Capisic Brook, seen from Taft Street on Jan. 30, is considered impaired due to contaminated stormwater.

The overhead view of Sagamore Village depicts where bio-retention cells and other drainage improvements will be installed to help protect nearby Capisic Brook.