By Lani Duke
RUTLAND—Heavy rains caused East Creek and, to a lesser extent, Otter Creek, to receive an unexpected addition of nearly 9.7 million gallons of partially treated wastewater and stormwater July 23. A report of the overflow became public July 25, delayed because the public notification system website was not functioning.
“The most rain falls during the 31 days centered around July 23, with an average total accumulation of 3.5 inches,” according to the website weatherspark.com.
During that morning deluge, Rutland received about 1.9 inches in two hours, VTDigger reported. The largest overflow of 2018, it was the most recent of 15 overflows this year.
Most of the time, both wastewater and stormwater are treated in Rutland’s wastewater treatment plant, City Public Works Director Jeff Wennberg told VTDigger July 25. When rain is unusually intense, relief vales open, preventing wastewater from backing up into homes, businesses, and streets.
Fairly typical of wastewater and sewer systems built in the Northeast and Midwest in the late 1800s, these overflows dump fecal coliform and microorganisms in seemingly small quantities, but sufficient to cause a public health risk for a minimum of 48 hours after a combined sewer overflow.
The largest wastewater treatment facility in Vermont, Rutland can successfully treat more than 22.5 million gallons a day, as long as it arrives slowly enough. The plant could process two inches a day without an overflow, but not two inches in 10, 15, or even 60 minutes, Wennberg elaborated.
The city’s public works department has been working to resolve the intermittent overflows but has not yet found a cost-effective counter strategy. Rutland spent $5.2 million to separate some of the stormwater from the wastewater in 2011, but complete separation would cost about $159 million, Wennberg estimated.
Passing untreated stormwater into the downstream waters may not be the wisest course. On its course through the watershed, it picks up contaminants. Developed lands (85 percent of Rutland’s surface area) contribute the highest percentage per acre of phosphorus pollution entering Lake Champlain. Stormwater flowing constantly into streams may produce more total pollution than the overflows do, Wennberg reasoned.
The state Department of Environmental Conservation lists wastewater upgrades Rutland should undertake to reduce overflows. Failure to deliver a plan of which projects it will install risks fines for permit violation.
Wennberg has asked the state for a grant to study various upgrades’ efficacy, contracting with engineering firm Weston and Sampson to model the city’s combined sewer system. Public Works will soon begin testing how assorted solutions would reduce overflows.
Installing rainwater traps such as rain gardens and permeable pavement may be effective. Wennberg is looking at Cincinnati’s “smart sewers” as a possible model, where sensors, gates, and valves redirect flow to higher storage capacity areas.
