Backup power generators add reliability, easy maintenance to new lift stations in an expanding suburb.
Like many municipal officials
throughout North America, those in Camas, WA, consider it a bad day when they
have to address sewage backups as a result of lift stations losing power after a
power outage.
Camas, a city of 15,000, is
located on the north bank of the Columbia River near Portland, OR, and
Vancouver, WA. Like so many other municipalities in North America, Camas is
plagued by an aging infrastructure, including its sewage collection system.
While the power outages that cause
the lift stations to stop working are infrequent, when they do occur, they can
wreak havoc in the community and point to the need for backup power to get them
up-and-running as soon as possible. “We’re pretty much like anybody else—a
sewage spill is not good press,” says Jim Dickinson, the wastewater operations
supervisor for Camas.
If it’s strong enough, a wind can
cause the municipality to lose electrical power and ultimately cause the lift
stations to stop working, says Dickinson. Outside of acts of nature, there are
also human-initiated events that may knock out power as well, such as the
drunken woman who had driven her vehicle into a power transformer, which knocked
out power in one area of Camas for quite some time.
Additionally, “We get ice storms
once in a while, and with things that go bump in the night, we could have a
problem,” says Dickinson. “Generally, it’s not very often. Clark Public
Utilities does a really good job of keeping the power running and getting it
back on when it goes off, so we might experience the problem four times a
year.”
Nature throws other unexpected
curve balls. “We had some problems at the plant with the power feed coming in
over the highway when a bird got into the switch gear and kicked out the breaker
on the fuse,” says Dickinson. “Like anyplace else, we experience the pitfalls of
being a public utility.”
Camas has always had pump stations
go down, but, until recently, city workers would have to physically move
equipment from one location to another to address the emergencies.
“For a lot of years, we only had
maybe five stations, and we’d have a portable trailer generator that we’d haul
around to one site, pump something down, then have to break it down and haul it
to another site, and pump it down,” says Dickinson. “It was kind of futile in as
much as we have a fair distance to cover, and usually the weather conditions
were fairly adverse and it tended to slide around the tandem axles.”
After a fair amount of discontent
in repeating that scenario, Camas officials developed a plan that called for
onsite backup power generation to be installed at any new pump station that
would be erected, as well as retrofits of older systems. “We kept getting quite
a few new stations over the years, so it just becomes part of the specifications
that any developer coming in wanting to develop in the city must provide the
level of equipment and function that we have specified,” says Dickinson. “They
cannot come in with lesser pump controls and generators.”
Presently, the city has numerous
manufactured brands inherited from the past, “but we no longer have one
trailer-mounted generator go around and service all these stations with power
outages, and we didn’t want to have a fleet of trailers, so we started going
with the onsite generation,” says Dickinson.
Until recent history, Camas relied
on gravity-fed lift stations to transport raw sewage to the treatment plant.
About six years ago, in response to a mushrooming population, Camas began
retrofitting older lift stations with pre-engineered pressure systems. Of the
city’s 20 lift stations, seven are new systems, pre-engineered by Romtec
Utilities in Roseburg, OR, for consistency in design and equipment. Camas’
patchwork of different manufacturers’ units had made repairs a challenge due to
the wiring inconsistencies among the various electrical panels.
The new pre-engineered lift
stations include a wet well, two or three submersible pumps, piping, liquid
level sensors, an underground valve vault, electric pump controls, the standby
power generator, an automatic transfer switch, and communication equipment. All
components are delivered as one pre-engineered package and installed in a
week.
Additionally, city officials
recently specified that each new lift station include standby power generators
from Cummins Power Generation. The generators are sized to meet the needs of the
lift stations, which pump large volumes of water against friction losses,
dynamic head, and other factors.
There are no more portable
trailer-mounted units in Camas, says Dickinson. The permanently installed
diesel-powered generator sets at the lift stations range from 20–200 kW. The
power output specification is tied in to the pump size, which can range from
11–35 horsepower. Case in point: At one lift station, twin pump motors require
39.6 kW for starting, and 22.5 kW for running. All lift stations must run both
pumps simultaneously if necessary.
In addition to motor horsepower
and voltage, other critical performance parameters include starting current,
motor efficiency rating, and required auxiliary loads, such as generator set
controls, lights, heaters, and odor control. Additionally, ambient temperature
range, pollution control, elevation above sea level, and anticipated growth in
the area served by the lift station serve as additional requirements for the
systems.
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Photo: Cummins Power Generation
Keeping the lift stations operative during power interruptions is all about protecting the environment. |
The lift stations also include
Cummins Power Generation OTEC open transition transfer switches, providing a
“break-before-make” power transfer from the grid to the generator and back again
for both testing and power outages. The gap between power sources can be
programmed into the OTEC switch to accommodate each lift station’s parameters
and generator set. Additionally, the programmable gap of several seconds between
power sources allows the back-EMF (electromotive force) generated by the lift
station’s pump motors to fully dissipate, a key to protecting the generator
set’s alternator.
That time gap also enables the
generator set to get up to operating speed and stabilize voltage output.
The generator sets are installed
in sound-attenuated enclosures, so as to eliminate noise disturbances in the
surrounding community. The systems also inhabit a small footprint, such as 1,000
square feet. The efficiency of the diesel-powered generator sets also include
reduced fuel storage requirements. Natural gas and propane also can be used as a
fuel sources if they are available at the site.
Until nine years ago, Camas’
wastewater treatment plant did not have onsite power generation, says Dickinson.
The first phase was then installed, and now there are two onsite generators that
can power the entire plant in the event of an outage, he says, adding that the
city’s water department has similar protection.
While in some cases, it was
feasible to move the portable generator from one lift station to another as was
done in the earlier setup, “with the number of stations I have now and the
distance apart they are, we have a fair amount of property here in the city that
covers quite a bit of land, and we just annexed another parcel, so there are
really large distances to cover to get from one end of town to another,” says
Dickinson.
“It is totally unfeasible to think
you’re getting a fleet of portable generators out and about, so the only way to
do it is by and large prevent the ecological catastrophe that will ensue with a
prolonged power outage by using permanent onsite backup power generators,” he
adds.
Reliability was another concern
when Camas officials decided to spec permanent onsite power generation. “Half of
the time, that thing would run, and then it would quit,” says Dickinson. “The
station or several stations would go down, and then there would be a sewage
overflow.”
The suggestion by state
environmental officials that Camas should consider alternatives—along with the
inconvenience of hauling one generator from site to site—bolstered city
officials’ decision to spec permanent onsite power generation from that point
forward.
Additionally, contractors would
finance the new systems as they built new lift stations.
The retrofitting of existing lift
stations has been done in stages over the years, but only when a station needed
rebuilding. At that point, permanent onsite power generation was budgeted into
the retrofit job. “We’ve upgraded existing stations to have onsite generation,”
says Dickinson. “I used to take care of five stations, and two of them were
buildings with stations in them that already had onsite generation. The package
stations over the years have been rebuilt, and during that rebuild they were
equipped with onsite generators.”
Camas now has 21 stations, all
equipped with permanent onsite power generations. Now it’s a matter of
maintaining them, Dickinson says. “Everything is on a one-year maintenance
cycle. We have a company come in and go through each one and let me know what
needs to be done, and then we take care of repairs.”
The Cummins Power Generation
generators replace others that Camas had used before. Not only were there
mechanical issues, but also the former company’s tech support was anything but
supportive, Dickinson says. When Camas encounters problems with the Cummins
units, “they readily admit the fault” and address it, Dickinson says.
There wasn’t much of a learning
curve with respect to the onsite power generation units, he states. “It’s all
pretty standard,” says Dickinson. “Each station is a little bit different—for
instance, each has a different footprint. We get in and get familiar with it,
start monitoring it, and see what happens.”
To ensure that they will work when
needed during a power outage, city workers will test them weekly. “We spend an
awful lot of money to keep these things maintained,” he says, of the generators.
“They are inspected once a year, and if we have a bad battery or blocked heater,
it’s dealt with as soon as it becomes known to us. They are always maintained to
the highest level because you never know when you are going to need them. The
city has stepped up and is paying a good deal of money to maintain them as part
of the environmental stewardship.”
The weekly inspections help to
ensure that the backup power will kick into motion when needed. Even backup
power can go awry at times. One of Dickinson’s employees called him one time to
let him know a rodent compromised one of the generators. “A little mouse got in
there and chewed up some wiring,” he explains. “When our employee went there to
‘exercise’ the generator, he saw the scorch marks. That thing must have really
lit up there for a while, and the little mouse was just fried.
“But that is a problem, and that
was quite a bill to get that generator rewired and rebuilt,” he adds. “But
that’s what happens. The engine was still good, but the generator was toast.
Whatever it takes, we’ll do it.”
Camas derives energy efficiencies
from instituting onsite backup power generation, by not having to haul a unit
from one site to another. Ultimately, keeping the lift stations operative during
power interruptions is all about protecting the environment.
“The whole point of onsite power
is to prevent an environmental problem,” says Dickinson. “In an outage, the
power station will continue to operate and not bypass sewage. We have one
station that just goes right off the top and runs down the driveway and into the
boulevard. That’s really not attractive. In Portland, they are dealing with
combined sewers, and every time it rains just a little bit of a drizzle, their
combined sewers overflow, and then the Columbia River gets a ‘do not swim’
warning, and residents are told to wash their hands after touching it.”
“They are spending a lot of money
trying to separate their sewer system,” he continues. “In our little town here,
we are right on the gateway to the Columbia River Gorge and somewhat well-known
for recreational activities and as an environmentally sensitive area. The city
wants to be known as having good stewardship for the environment.”
That concern comes from outside
the community as well.
Washington’s Department of Ecology
monitors spills, which must be reported. “The Southwest Washington Clean Air
Agency keeps an eye on our generators—how much toxicity is in the emissions they
produce,” he says. “We run them only for emergency use to prevent sewage
pollution. It’s a layer of regulatory oversight we have to deal with that, if
nothing else, makes us ecologically responsible.”