Water drawn from Lake Springfield for the purpose of meeting this community's domestic water needs is
purified at the Water Purification Plant, located just north of the Dallman and Dallman
4 electric generating stations. The Water Purification Plant was first opened in 1935 and
has since undergone several expansions and upgrades to bring it to its present processing
capability of 46 million gallons per day.
Steps taken during the water purification process ensure CWLP's ability to convert raw lake water into a safe,
clean product that consistently meets state water quality standards.
The purification process begins at the intake tower, where water flows into one of the tower's
four gates, passes through a six-foot tunnel, and enters the low-service pump room in the
Lakeside Power Station. (A new low-service pump station is under construction.
Once it is completed in the fall of 2014, the old low-service pump station inside the Lakeside Power Station will be decommissioned.)
There, revolving screens remove fish, leaves and other large debris. It is also at this point that
powdered activated carbon is added to remove unpleasant tastes and odors, as well as residual agricultural pesticides.
The water is then pumped to the Purification Plant, where it passes through a chemical dosing chamber to receive lime,
which softens the water, and ferric sulfate (iron) and polymer, both of which coagulate the suspended particles in the water.
From the dosing chamber, the water passes to one of five upflow clarifiers.
In the clarifiers, 90% of the suspended particles are removed from the water,
which is then sent to the filter gallery for the final step in the purification process.
On its way to the filter gallery, the clarified water receives a dose of carbon dioxide to lower the pH
(which was raised during the lime softening process), chlorine to kill bacteria, and fluoride to prevent tooth decay.
From the filter gallery, the clean water is sent to two clearwells on the plant grounds for temporary storage prior to distribution
(via the utility's new high-service pump station that was completed in spring 2014). At this point,
the purification process is complete. It has taken less than two hours to convert raw lake water into a safe,
clean product that consistently meets state water quality standards.
CWLP has a total of five clarifiers, representing three different technologies.
The oldest technology is the Spaulding Upflow Clarifer, which was designed by the utility's
first Water Plant Superintendent, Charles Spaulding, and placed into operation when the lakeside
Water Purification Plant was built in 1935. For many years, this type of clarifier was considered
state-of-the-art. It is still used by purification plants around the world. In Spaulding Upflow Clarifiers,
water flows downward, through a large inverted cone in the center of the clarifier. At the bottom of this cone,
a series of revolving paddles mix the water and chemicals used in the treatment process—including ferric sulfate and polymer,
which help dirt and other suspended particles coagulate (stick together).
Then, flowing outward and upward into the main body of the clarifier, the water passes through a
"blanket" of lime sludge formed from an accumulation of coagulated particles. Most of the suspended particles
in the upflowing water are trapped there. The cleaned water then flows over the top of the clarifier and heads
to the filter gallery. Of the three original Spaulding Upflow Clarifiers, one remains. The other two have been
rebuilt as Helical Flow Clarifiers (see below). The last of the three original clarifiers is scheduled to be rebuilt
using the helical flow design beginning in September 2013, with construction being completed by early summer 2014.
The second type of clarifier currently being used by CWLP is a Permutit unit, which is simply a
modified version of the Spaulding clarifier. CWLP currently has two Permutit-style clarifiers, which were built in the mid-1950s.
The third and newest model, is the Helical Flow Clarifier, designed by another former CWLP Water Plant Superintendent, Dave Wyness.
In this type of clarifier, the water is introduced into the base of the clarifier where it moves upward in an ever
expanding and slowing spiral motion, passing through the lime sludge blanket on its way. The Helical Flow Clarifier is superior
to the Spaulding unit in two ways. First, it has no moving parts and requires no power to operate. Second,
it is better at removing suspended particles, producing a better overall water quality. As in the Spaulding Clarifiers,
water that has passed through the sludge blanket then overflows the top of the clarifier and heads to the filter gallery for the final stage of purification.
Each of the 12 two-cell filters in the filter gallery contains a layer each of sand and finely crushed anthracite coal,
which screen out additional particles still remaining in the water.
These filters are cleaned about every 96 hours by "backwashing" them with 60,000 gallons of water per filter.
From the filter gallery, the clean water is sent to two underground clearwells for temporary storage prior to distribution.
As part of its multi-phase, multi-year Water Works Infrastructure Improvement Program,
which was launched in 2008, CWLP has constructed a new $8.3 million, six-million gallon
underground clearwell that provides on-site water storage at the utility's Stevenson Drive plant complex.
A clearwell is a large storage tank that holds treated drinking water for a several hours before it is
distributed throughout the city for use by consumers. The holding period allows time for chlorine added to
the water during the purification process to complete its work disinfecting the water of bacteria and other
potential pathogens that might have been present in the raw water supply.
CWLP recently completed construction on a new six million gallon clearwell that was placed into service in May 2014.
Completion of the new clearwell, as well as a new high-service pump station, allowed the utility
to remove from service the oldest of its two existing underground clearwells, which was built in the mid-1930s.
Once the new clearwell—which acts in tandem with the remaining existing underground clearwell
(which was built in the mid-1950s)—was placed in operation, the utility's total clearwell capacity increased
from six million gallons to 10 million gallons. The new clearwell's interior consists of a series of "baffle"
walls that direct the flow of water through the clearwell.. This ensures the chlorine added to the water during
the purification process has adequate time to disinfect the water.
Projects being undertaken as part of the utility's Water Works Infrastructure Improvement Program are being funded
by revenues raised as a result of a four-step rate increase that began in May 2008. The final increase took effect March 1, 2011.
In conjunction with the clearwell, the utility's Water Works Infrastructure Improvement Program
also called for the construction of two water pumping stations: a high-service station located immediately
south of the new clearwell, and a low-service station east of it, along the lake shore just southwest of Spaulding Dam.
These facilities were designed to house the low- and high-service water pumps that have been located in the
Lakeside Power Station since the lake and that facility were built in 1935. The Lakeside Power Station and the
equipment in it have served their useful lives. The electric generating units housed
there were decommissioned after the Dallman 4 Power Station was completed in 2009.
The new low-service pump station, which is located closest to the lake and was completed in the fall of 2014,
pumps raw water from the lake to the Purification Plant. The high-service pump station,
which was completed in May 2014 and is located just south of the new clearwell, pumps water from the
clearwell into the citywide water distribution system. This system consists of over 760 miles of transmission and distribution mains.
The total cost of building the new pumping stations and clearwell was $41 million.
To view photos and documents about the new facilities and progress, visit the documents section of the water division.