The back alley in the southwest corner of the city seems like an odd place to showcase progressive city investment.

But Alley 148 had two things going for it: The topography around the city-owned alley forces water toward it, and the alley needed to be repaved.

"That's when you get the best return on your investment, when you integrate it into another project," said Charlotte Katzenmoyer, Lancaster city's public works director.

The alley, between Prospect, Pearl, Hilton and Garnett streets, already was on the repaving list when Katzenmoyer challenged her staff to find ways to "green" projects.

Under orders from the federal Environmental Protection Agency, the city must find ways to keep 1 billion gallons of stormwater, nutrients and sediment from flowing into the city's sewer system during heavy rains.

The rush of stormwater overwhelms the treatment capacity of the city's wastewater treatment plant, and raw sewage gets into the Conestoga River and, eventually, the Chesapeake Bay.

The city could spend an estimated $300 million to build storage tanks, where stormwater would be held until it could be treated.

Instead of investing in so-called "gray infrastructure," however, the city has embarked on a 25-year program to develop dozens of "green infrastructure" projects that would allow the rainwater to soak into the ground.

Those projects include, among other measures, repaving parking lots and basketball courts with porous pavement, planting trees, installing green roofs on buildings and  adding rain gardens along streets.

The alleyway is the city's second green project. It follows a porous basketball court that opened last spring at the renovated Sixth Ward Park last spring.

Repaving the alley with traditional macadam would have cost about $100,000. Instead, at a cost of $130,480, the city repaved with simulated cobblestone paving stones in the center. Car tires will ride on parallel concrete strips on each side of the paving stones.

Before the repaving, puddles formed in the alley after a rain. Now the rainwater is expected to disappear beneath the paving stones as it flows into an area of crushed stone and the ground below the alley.

Katzenmoyer said the alleyway is expected to absorb 200,000 gallons of rainwater per year.

The alley is not in an area of the city where the curbside storm sewers combine with the sanitary sewer system. Stormwater there would not be part of the overflow problem, Katzenmoyer said. But the green alley project does help meet the EPA requirement to prevent nutrients and sediment from entering the system, she said.

Other alleyways on the city's repaving list were considered for green repaving, but they would not have eliminated enough rainwater to justify the investment, Katzenmoyer said.

The number she is trying to beat is 16 cents per gallon for green stormwater improvements. That cost is almost half of the 25-to-30-cents per-gallon cost of building storage tanks.

The next projects on the city's list will begin in the spring.

They include four small parking lots in the southeast area of the city, park renovations and a series of projects done in conjunction with the LIVE Green organization.

The city-owned lots are at Mifflin Street, between South Plum Street and East End Avenue; South Plum Street, between Dauphin and Green streets; Dauphin Street, with entrances on Dauphin and Juniata streets; and Penn Avenue, between Green and Dauphin streets.

Each of the lots is to be covered with porous pavement, and rainwater from surrounding blocks will drain toward the lot. Each lot is expected to capture between 600,000 to 700,000 gallons of stormwater annually.

The lots would be repaved at a cost of about $160,000 each, with the funding coming from a $7 million low-interest loan the city secured from the Pennsylvania Infrastructure Investment Authority and a $400,000 grant from the National Fish and Wildlife Foundation.

Park renovations will begin with Brandon Park in the southwest area of the city. Two parking lots there are slated for repavement with a porous surface and recessed rain gardens, where water can collect and infiltrate the soil.

The Brandon Park improvements are expected to absorb as much as 5 million gallons of rainwater annually, Katzenmoyer said.

Renovations to Crystal and Rodney parks are being finalized, Katzenmoyer said. Those renovations could start next fall after the summer recreation season, she said.

The park improvements are being funded through a combination of a state Redevelopment Capital Assistance grant and city capital improvement bond funds.

In the next two months, LIVE Green, an urban greening organization, will be doing outreach on behalf of the city to private property owners around the Northwest Corridor Linear Park.

Those projects, funded through the PennVEST loan dollars, include adding green roofs, infiltration trenches and retention areas in parking lots; planting trees; and replacing parking pavement with porous surfaces.

The city will bear 90 percent of the cost of those projects, while private property owners will pay the remaining 10 percent.

Contracts with property owners are expected to be signed by the end of January, and work is expected to begin in the spring.

Also starting next year will be the third phase of the city's $2.5 million streetscape enhancement project. In the spring and summer, workers will replace paving stones and install benches, lighting, trees and other fixtures around Central Market and Penn Square.

Katzenmoyer said test borings found a thick slab of concrete under the paving stones now in place. Rather than break up the concrete to allow rainwater to soak into the ground, she said the decision was made to direct the water down East Grant Street, toward Prince Street.

Trees and plants typically found in swampy areas are planned in recessed areas along the sloping street. The plantings and landscaping are expected to cost about $73,000 and absorb nearly 470,000 gallons of stormwater annually.

A total of 35 green infrastructure projects are planned.

bharris@lnpnews.com