Bellevue water
and sewer systems
reach capacity
Water study illuminates impact
problems
By MATT FURBER
Express Staff Writer
From the source to the sewer,
Bellevue’s municipal water services have reached their capacity 10 years
ahead of predictions.
The sewer system in winter is not
treating effluent sufficiently and the water distribution system in
summer threatens to burn out pump motors, but the city is busy seeking
remedies.
Bellevue City Superintendent
Brian Whipple explains the problems with Bellevue’s municipal sewage
treatment plant. Express photos by David N. Seelig
Prior to 1992 all homes in
Bellevue had septic systems for treating wastewater. Built for $3.2
million in 1992 the municipal system was given a 20-year life span, but
it is bumping up against design limitations 10 years early, especially
during winter months when microorganisms that digest contaminants slow
down.
The distribution system for the
city’s water source, two wells and a spring that are funneled through a
single storage tank is taxed because demand often outweighs collection
capacity. The biggest impact comes during hot summer days when lawn
sprinkling demands are highest. Water pumps get little rest as they work
to keep the storage tank filled to ensure that required fire flows are
maintained.
This winter the city sewer system
is exceeding standards for nitrate levels. Last summer the water storage
tank at times was drained too low to maintain sufficient pressure for
operating fire hydrants sufficiently, city staff said.
A water distribution study
presented last month by Forsgren and Associates, the city’s engineering
firm showed how subdivisions under construction or awaiting approval in
the city will have substantial impact putting the city at risk of having
low flow rates if any part of the system fails.
"There is no redundancy in the
system," said Steven Yearsley of Forsgren and Associates. He also warned
that the city should prepare for pump breakdowns as the latest
development comes on line and further tax city pumps. "I am really
concerned about the Shantrel well. If it went offline (during peak use
periods), there would only be a day and a half of water in the tank."
At the other end of the system the
city is at risk of contaminating ground water. Brian Whipple, Bellevue
city superintendent, said last week that the nitrate levels, 50 parts
per million for nitrites, is what can be expected from septic systems
but exceeds state standards for municipal treatment systems.
City effluent empties through two
pipes into a chain of three treatment ponds at the treatment plant, four
miles south of the city. In the first treatment pond underwater aeration
pipes feed oxygen to the microorganisms, but due to the organisms’
winter lethargy, the treatment ponds essentially become holding tanks
causing nitrite levels to increase, Whipple said.
In the summer treated wastewater
is applied to fields adjacent to the sewer plant. In the winter treated
effluent is recharged into the ground and potential for groundwater
contamination is a concern, Whipple said.
"The sewer system, according to
our engineers, can handle the present and future growth within the city
limits as far as volume," said Jack Stoneback, city administrator.
"However we do have some problems with our nitrites."
A feasibility study of the system
is pending. The city has budgeted $120,000 to pay for the work and has
retained another engineering firm, Boise-based Keller and Associates
design the study.
To get the city through the
interim and bring it closer to state standards, Whipple last month got
approval from the city council to purchase equipment that will further
churn up the effluent ponds and feed more oxygen to the microorganisms
to further improving their efficiency.
"If you keep them happy, (the
microorganisms) do what you want. They break down waste solids," he
said. "There’s a lot of work to do out there, but the problem is not one
that can’t be fixed."
Planning for the next level of
city infrastructure could be completed this year.
"(Keller and Associates) will take
into consideration future growth and the impact it will have on our
system," Stoneback said. "(The study) will tell us what have to do to
accommodate future growth whether it is five years out or ten years
out."
The cost of improvements to the
city’s water and sewer systems is yet to be determined. But, city
council members said completing the sewer feasibility study and a water
distribution system study, not yet planned could help the city secure
outside funding for any necessary improvements.
The city sewer system now in place
cost the city just over $1 million. The loan will be paid in full in
2013. The $1.7 million balance on the project was paid through a state
grant.