PORTSMOUTH — Between the frowns and furrowed brows of residents and vigorously waved homemade signs saying things like ‘Flush the sewer project,’ the engineer who presented the final plan for sewers on Oct. 21 had to sell it to a tough crowd.

And if sewers are what’s needed to solve the town’s wastewater issues, it’s the residents who must be convinced, because they will have the final say. Their vote on whether or not to fund a project now pegged at $154 million will decide if it happens.

The engineering firm Woodard & Curran recommends building two wastewater treatment plants and two collection systems. One would service all of the north end to west of Chase Road and now also the Bay View Avenue area, and a second plant and system would take care of portions of the west side, including Weavers Cove, land owned by O’Neill Properties Group, the Navy housing complex, two of the tank farms, the Melville marine district and a nearby mobile-home neighborhood, Raytheon, and now Arnold’s Point and Redwood Farms, too. Building a neighborhood-wide cluster system for the Pine Tree Road area is also part of the recommendation and included in the cost.

Woodard & Curran estimates that this will cost $1,555 per service allotment each year. This does not include the cost of equipment and work to connect to the system which can add up to $8,000; also, property owners will have to pay to cut the connection and fill in their old septic systems. But these figures (in today’s dollars) aren’t final and will be adjusted for the public hearing on Dec. 2.

As for the rest of the town, Woodard & Curran says the Martens Road and McCorrie’s Lane areas need to build neighborhood cluster systems, while septic systems are working fine everywhere else.

Before discussion opened to the nearly 200 residents (who were mostly over the age of 50) in attendance, councilors had a chance to question Woodard & Curran’s project manager Bob Rafferty.

After Mr. Rafferty explained how much contingency is built into the cost — 15 percent for the collection system and 50 percent for the treatment plants — he told Councilor James Seveney that he had concluded correctly from the report that the individual cost would be about the same to build sewers as it would be to install new septic systems and enforce repairs and maintenance under a wastewater management district.

Councilor Dennis Canario criticized the report for not “looking into a wastewater management district as much as sewers.”

Mr. Rafferty said the engineers researched a wastewater management district and determined that it would work for most of the town. But “the areas identified as (needing) sewers, need sewers,” he said.

“I don’t feel as though I have much more information than I did a year ago,” Mr. Canario said to big applause and residents rattling signs like, ‘It didn’t solve Newport and Middletown’s problems’ and ‘Spending $54,000 of my hard earned money is a lot of crap.’ “How can we even think about putting this to voters when we’re not educated enough, when we don’t know enough about the wastewater management district side?”

Councilor Karen Gleason said she thought Woodard & Curran should use more information from the Berger report, a similar study done in 2002. That report said septic systems under a wastewater management district would work, even in the problem areas of Island Park and Common Fence Point, she said.

Saying he does not agree with the conclusions of the Berger report, Mr. Rafferty said that the problem in Island Park is that effluent sinks through the ground too fast for proper breakdown and is then washed into the river, and is compounded by the number of small, densely packed lots.

More than an hour and a half into the discussion, residents got their chance to ask questions.

Phil Driscoll said that as a member of the town’s wastewater advisory committee, he knows the committee has not had a chance to research “innovative or alternative systems.” Woodard & Curran should have evaluated the cost and effectiveness of Tiverton’s wastewater management district, he added, which are different from the estimates given in the engineers’ comparisons of other towns. He added that the town should go after illegal hook-ups to the stormwater system before deciding if sewers are the answer.

Many asked what proof there is that a pollution problem exists and is caused by failed septic systems. Charlie Clark said he thought the problem is more likely caused by the Tiverton and Fall River neighborhoods along the river and bay.

Angelo Liberti, of the state Department of Environmental Management’s office of water resources, said that DEM opened up manholes and looked in storm drains in Island Park and Portsmouth Park (the two areas said to have pollution problems) and saw toilet paper and illegal connections, which indicate that there is human waste being flushed out through the system. (Liz Pedro, of Island Park, said she remembers DEM’s inspection — “that was 20 years ago.”)

When a man from Island Park said his septic system works fine, Mr. Liberti said it’s not a problem from one residence, it’s the “whole neighborhood.” But the man interrupted his explanation and stormed away.

Residents often disrupted discussion or shouted rebuttals from their seats. Council President Peter McIntyre had to exert some crowd control when several people yelled an answer to Ms. Gleason’s question of how much the population would increase with development enabled by a sewer system — from 17,000 to 30,000, they said. (Mr. Rafferty said after the meeting that an estimated population increase to 30,080 was taken from the town’s Comprehensive Community Plan.)

Mr. Rafferty followed that up by saying the town should consider changing its zoning regulations to reflect what the town wants for future development. In particular, he said, the town should educate owners of “dotted-line lots” that they will be charged for service for each lot, even if it’s not developed or not connected to the system. Merging these lots would reduce the capacity need of a treatment plant and bring down the cost of the project, he said.

In response to whether the town would see problems like waste overflow and a rotten odor coming from its sewer system, Mr. Rafferty said new technology has “greatly reduced” the types of problems seen in Newport and Middletown’s sewer systems.