PORTLAND — As the city seeks to meet a 1991 state and federal mandate to reduce the flow of contaminated wastewater in Casco Bay, four sewer separation projects put out for bids this year have all come back with higher costs than estimated.

“Our feeling is that there is a lot of work and not very many contractors to do it, particularly on the larger jobs,” Public Works Director Chris Brooks said April 1.

Those projects create new drainage for stormwater while properly directing wastewater to the Portland Water District treatment plant near East End Beach.

Branch said two projects came in high enough over estimates to cause them to be shelved until fall. A sewer separation project on Brighton Avenue was estimated to cost $1.05 million; the bid was $600,000 more.

Sewer separation work scheduled for the Ocean Avenue/Mackworth Street area in East Deering carried a $4.15 million estimate; a bid of $6.18 million was received, Branch said. That bid will also be sent out again in the fall.

The city is moving ahead on two sewer separation projects around Preble Street in the Bayside and Back Cove areas, although both are also more expensive than estimated.

Phase 1 of the work was awarded to low bidder Grondin Corp. for $1.65 million after the city estimated a $1.58 million cost. The project is underway.

The second phase of work, which extends through Bayside to Cumberland Avenue and links to the new sewer separation work below State Street that drains stormwater into Back Cove, was estimated to cost $2.9 million.

Sargent Corp. was awarded the job with a low bid of $3.94 million. Work is expected to begin June 1.

On Tuesday, Branch said the long-delayed Back Cove South Storage facility also remains in limbo because of escalating costs.

The city did receive proposals for what is envisioned as a facility storing as much as 3.5 million gallons of stormwater at a time, while reducing the flow to the treatment plant from 150 million gallons annually to 18 million gallons, according to the bid outline. The work is a redesign of a 2015 project shelved after bids came in around $35 million, or $10-15 million above estimate.

“We have received the proposals for BCSSF, but have not opened the fees,” Branch said. ” … the proposals need to be rated for qualifications of the design-build teams and their design approach to the project.”

A $23.55 million RFP estimate is outdated, Branch said, by as much as 20-50%.

The city did get a lower bid than estimated for work on Thames Street, where street expansion includes rebuilding the stormwater outflow and seawall, as D&C Construction was awarded the job with a $1.9 million bid. The city request for proposals carried a $2.35 million estimate.

The sewer separation projects are funded through the city capital improvements budget, using bonds typically repaid by revenue from sewer user fees and the stormwater fee the city began assessing three years ago. Sewer use fees are now $8.20 per 100 cubic feet; the monthly stormwater fee for property owners is $6.30 for every 1,200 feet of impervious surface.

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

A second phase of sewer separation work in Portland’s Bayside will begin June 1, but will cost the city $1 million more than estimated.