PORTLAND — With the flip of a switch, the sun is shining on City Hall and Merrill Auditorium.

On Tuesday, the city and ReVision Energy began drawing power from the solar farm at the capped landfill on Ocean Avenue. The 2,800-plus solar panels spread over 4.3 acres on top of the 45-acre landfill site are expected to generate 1.2 million kilowatt-hours of electricity annually – enough output to power both buildings.

The farm is one of the foundations of the city’s plan to use only renewable energy sources by 2040 and to reduce carbon emissions by 80 percent by 2050, City Hall spokeswoman Jessica Grondin said in a Dec. 12 press release.

The green harvest comes at a cost of time and money far greater than anticipated.

Built by ReVision Energy, which will own the farm for at least seven years and sell the power to the city, the farm itself was completed about a year later than expected and cost the city at least $455,000 more than expected in order to shore up the site. The state reimbursed the city $60,000 for some of the work, Public Works Director Chris Branch said Monday.

Additional remediation work required to comply with the overall landfill closure permit revision granted by the Maine Department of Environmental Protection (which includes the solar farm) carries a cost estimate of $1.1 million, Grondin said Monday.

The city has allocated $540,000 for remediation work in its current capital improvements budget. City Finance Director Brendan O’Connell said Monday the remainder would come from the operating budget.

Conditions at the landfill, closed about 40 years ago, had deteriorated badly enough to be found unsuitable for racks of solar panels by the DEP. The cap above the landfill had worn away, and methane gas accumulated underneath.

The area, used for open space recreation and popular for dog walking, also had water contaminated by leaching from the landfill. The city has posted warnings to visitors advising them to keep pets away from puddles.

To comply with the DEP, the city has to better vent the accumulated methane and rebuild the cap over the landfill to at least 24 inches, with 18 inches serving as a barrier to prevent water from seeping into the landfill.

The permit revision also requires the rest of the landfill to be properly regraded and capped and the city must submit an overall maintenance plan to the state by Dec. 31, 2019.

The city has also committed to testing water in nearby wells.

By terms of the agreement with ReVision, the city will pay 0.1056 cents per kWh for the first two years of the agreement. By year 30, the rate would be 0.2108.

The agreement allows several options for the city to buy the farm, built at ReVision’s expense. The first option, for $1.6 million, could be exercised in seven years. The purchase price would decrease in ensuing years by about $77,500 annually.

Away from the farm, the city has also installed solar panels on a building at Riverside Golf Course and the Portland International Jetport. According to the city website, the Riverside panels are used to charge the golf carts.

The panels installed on the roof of the Jetport garage are expected to produce half the power needed for operations at the garage and rental car facility. It is also believed to be the largest rooftop array in the state, Grondin said.

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

Portland spent more than $450,000 to remediate environmental conditions at its solar farm off Ocean Avenue, but still warns visitors that animals should avoid drinking standing water at the site.

Seen from above, the 2,800 solar panels installed at the former Ocean Avenue landfill in Portland are expected to generate 1.2 million kilowatt hours of electricity annually.