POULSBO — The city of Poulsbo plans to decrease pollutants in Liberty Bay by installing pervious pavement and rain gardens in Anderson Parkway.

Changes to the parking lot, located between Front Street and Waterfront Park, will improve stormwater runoff and reduce the amount of fecal coliform bacteria and petroleum hydrocarbons that flow into the bay, according to a plan between the city and the state Department of Ecology.

“What this project’s going to do is intersect the water running off the plot and treat it with a bioswale. It’ll clean up the water before it’s discharged into the bay,” said Poulsbo Councilman Dale Rudolph.

The Department of Ecology will fund roughly $270,500 — or 75 percent — of the improvements, which include laying 7,900 square feet of pervious pavement and 1,700 square feet of rain gardens.

The city will pay the remaining price of about $90,000.

Pervious pavement material allows water to percolate through to soil below and rain gardens are depressions that absorb water runoff from impenetrable surfaces. Both are Low Impact Development concepts.

The improvements will allow 93 percent of stormwater runoff to infiltrate the ground instead of flowing directly into Liberty Bay.

The city has three years to complete the project, according to the terms of the grant. City Engineer Andrzej Kasiniak said it will likely take at least two years, as the construction will be done in stages and a project design that doesn’t eliminate any parking spaces still needs to be drawn.

Crews will first remove the existing impervious pavement on Anderson Parkway.

The parkway was created in the 1950s when then-Mayor Martin Anderson commissioned a dredging and filling along the shore of Liberty Bay. The shoreline formerly reached the western edge of Front Street.

The bay was further filled in the 1970s when Anderson Parkway was expanded to accommodate more cars.

Some city leaders have recently eyed the lot as a potential space for a public park or mixed-use development.

Liberty Bay and several of its tributaries exceed fecal coliform standards according to the state’s 2008 water quality assessment. In 2009 the Department of Ecology conducted area studies to identify measures that could improve water quality in accordance with the federal Clean Water Act and U.S. Environmental Protection Agency.

Fecal coliform bacteria are indicators of harmful bacteria and viruses that can cause illness, according to the department.

Learn more at www.cityofpoulsbo.com and www.ecy.wa.gov.