Manager's Corner: Dillingham plans improvements to sewage lagoon

Jan 29, 2019

Construction is in the works for Dillingham's wastewater treatment facility. This summer, the city is aiming to install a new aeration system, new baffles that slow the movement of sewage through the lagoon and a new pond for waste from Dillingham and Aleknagik septic tanks.

Avery Lill/KDLG

The City of Dillingham is planning updates to its wastewater treatment system. All of them are aimed to make the system more effective at breaking down potentially harmful bacteria in sewage before the water flows back into the Nushagak River.

Dillingham’s sewage lagoon treats wastewater from the city center, fish processing holding tanks, and home septic tanks. Sewage is held in two “cells,” 1.5 acre ponds, while microorganisms stabilize the wastewater.

City manager Tod Larson explained that the city and Alaska Department of Environmental Conservation monitor the sewage lagoon closely. The system meets standards the vast majority of the time. However, Larson said that there are enough “spiked readings,” results do not meet state standards for water treatment, to cause concern. In particular, he is said that the aeration system is not efficiently circulating oxygen throughout the lagoon, especially during the winter, and the wastewater may be moving through the lagoon too quickly. Oxygen and time are critical for microorganisms to adequately treat raw sewage.

“We want to replace, all of the aeriation and the baffles,” said Larson. Baffles are partial barriers that slow the progress of wastewater through the lagoon. “And then, another issue, when the septage is dumped, when a truck comes out and cleans a septic tank out, that's highly concentrated waste water. And we need that to sit a little bit longer so that it feeds into the system a little bit more slowly. Part of this update will be do dig an extra pond that will be right next to the lagoons that will actually feed into those larger ponds over time so that it won't go in in such a concentrated manner.”

A new aeration system will help keep ice from forming on top of the sewage lagoon during the winter, which will aid in the treatment of Dillingham's wastewater.
Credit Avery Lill/KDLG

These updates to the lagoon will cost an estimated $660,000. The city has applied for a low-interest loan from ADEC to cover the expense. If the loan is approved, construction will begin this summer with the goal of completing the updates by November.  

While these fixes could ensure compliance with state standards in the short-term, the city is also exploring the option of relocating the sewage lagoon. It is situated near the edge of the Nushagak River, and since 1942, the sewage lagoon bluff has eroded up to 12 feet per year. Just this fall a storm chipped away about 20 feet of embankment, exposing part of the pipe that drains treated water from the lagoon into the river.

“We had to cover that up really quick before ice flow came in and damaged the pipe or broke the pipe,” said Larson. “I spoke with Denali Commission folks in Anchorage, and I think we're looking like we may get a grant for studying the movement of that lagoon to see if there's a place that we could move it to.”

In the meantime, organizations like Alaska Sea Grant and the Bristol Bay Native Association have assisted with monitoring erosion at near the lagoon.

This segment is a part of Manager's Corner.If you have a question you would like answered on the next Manager’s Corner, email avery@kdlg.org or call 907-842-2200.