Paul Eisenhardt, the lead consultant for Woonsocket’s wastewater treatment plant, said during a presentation to the city council on Monday night that he estimates Woonsocket sewer rates will rise from an average of $277 per year to $407 in order to pay for $35-$40 million in upgrades to remove phosphorous and nitrates from water discharged from the plant into the Blackstone River.
The upgrades are required as part of new standards set by the Rhode Island Department of Environmental Management to lower levels of phosphorous and nitrates being discharged into the Narragansett Bay watershed by 2014. All wastewater treatment plants that discharge into the Narragansett Bay will require similar upgrades.
Currently Woonsocket has the third lowest sewer rates in the state. After the upgrades the rate will be the tenth lowest, but as other area cities make improvements on their own plants, Woonsocket’s rates will probably settle back in around the third lowest, said Eisenhardt.
The new requirements from RIDEM are among some of the most stringent in the country, said Eisenhardt, but are part of a growing national trend to remove excessive nutrients from wastewater.
The upgrades will be paid for using a 20 year loan from the Rhode Island Clean Water Finance Agency at an interest rate of four percent.
“The city will be paying for it in annual installments,” said Finance Director Thomas Bruce. “Sources of the payments will strictly be user fees from the wastewater fund.”
The sewer rate increases will be determined by the City Council, said Public Works Director Sheila McGauvran. She said that they will not increase until after the project has been bid and construction has begun. She sees two scenarios on when the rates will increase: Either as a step process, where rates increase as payments are due to contractors or the second, where the increase is put off until the upgrades are complete.
“First of all, we are only working off estimates right now,” said McGauvran. The DEM will still need to approve and sign off on the technology that the city selects.
“The engineers do feel that they are being conservative in their price estimates,” she said, “We may realize some savings come bidding time.”
On Monday, the city council approved a consent agreement between the city and RIDEM on a timeline to upgrade the plant. On March 31, a draft facility plan will be submitted to RIDEM for approval. By late fall of 2011 the design documents should be 100 percent done. In early 2012, contractors will be selected and from 2012-2013 new construction will take place. By March 31, 2014 the new facilities will be on-line.
Excessive amounts of phosphorous in freshwater and nitrogen in seawater stimulate the growth of algae in the water, according to a 2005 report on nutrient loading by RIDEM. Algae blocks sunlight from reaching underwater seagrasses causing them to die. As seagrasses die, animals that depend on them leave or also die. Excessive amounts of algae also deprive the water of oxygen, which can lead to fish kills and may cause foul smells.
Eisenhardt recommended that the city use a moving bed bioreactor to remove nitrogen and ballasted flocculation to remove phosphorous.
“This is another improvement to the discharge,” said McGauvran, “I know that EPA Region 1 (New England) is applying the same standards to anything upstream. So the water coming downstream will be just as clean as what Woonsocket will be discharging.”