Erin Stewart - Aqua Sierra, Inc ATTACHMENT 2

Excellence In Fisheries and
Water Quality Management
Aqua Sierra, Inc. Reservoir Aeration Case Study
Bear Creek Reservoir
Lakewood, Colorado
110 Surface Acres - 652 Million Gallons
Over the past few decades the water quality within
Bear Creek Reservoir has declined. The dissolved
oxygen concentration in the water column was of
primary concern to the Bear Creek Watershed
Association (BCWA).
In 1990 The Denver Regional Council of
Governments ( DRCOG) found that the reservoir
showed advanced signs of eutrophication that
affected aquatic life, water supplies and
agricultural uses. The reservoir trophic state was
listed as hypertrophic, which is considered very
poor water quality. DRCOG recommended that a
hypolimnetic aeration system be installed to
improve these conditions. The system was
installed in 1993 and was met with limited success
as it began to structurally fail due to continued
freezing in the winter. In 1999 a dura - venturi aeration system was installed.
improve the dissolved oxygen conditions throughout the reservoir.
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This system did very little to
In 2002, The Colorado Monitoring and Evaluation
Lists identified Bear Creek Reservoir as potentially impaired
due to low dissolved oxygen conditions in the water column
during the warm summer months.
During the fall of 2002 Aqua Sierra, Inc. was hired by
the City of Lakewood to design and install an Air Diffusion
Systems (ADS) lakebed aeration system. This system
incorporated eleven ADS (LTC) aeration modules and over
15,000 feet of self sinking feeder tubing. This system mixes
242,000,000 gallons per day and turns over the entire reservoir
once every three days.
The ADS system was a complete success. Since the
installation in 2002 the entire water column has maintained
dissolved oxygen levels above 5 mg /L, the level at which
aquatic life becomes stressed. The average annual total
phosphorus load has been reduced by 24% with this system
(see graphs below). There has been a 37% decrease in
chlorophyll -a concentrations within the reservoir.
9094 US Highway 285, Morrison, CO 80465 -8950
(303) 697 -5486
(Toll Free) (800) 524 —FISH (3474)
FAX [phone]
http: / /www.aqua- sierra.com

Excellence In Fisheries and
Water Quality Management
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1"m Bear Creek Reservoir - Lakewood, Colorado
110 Surface Acres - 652 Million Gallons
Aeration by Aqua Sierra, Inc.
Surface
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Aquatic Life Stressed below 5 mg /L
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9094 US Highway 285, Morrison, CO 80465 -8950
(303) 697 -5486
(Toll Free) (800) 524 —FISH (3474)
FAX [phone]
http: / /www.aqua- sierra.com

Excellence In Fisheries and
Water Quality Management
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Bear Creek Reservoir
Average Annual Total Phosphorus
1999 2000 2001 2002
9094 US Highway 285, Morrison, CO 80465 -8950
(303) 697 -5486
(Toll Free) (800) 524 —FISH (3474)
FAX [phone]
http: / /www.aqua- sierra.com
2003 2004 2005
2006
2007

Excellence In Fisheries and
Water Quality Management
Active ADS modules in Bear Creek Reservoir
By installing our diffusers in the deepest reaches of the lake and aligning them perpendicular to the
predominant wind patterns, our systems not only break the thermocline (the layer separating oxygenated
surface waters from deoxygenated layers) but facilitate the continuous mixing of the entire water body.
The removal of the anoxic hypolimnion (the bottom strata of water without oxygen) initiates the oxidation
and particulation of iron, manganese, and phosphorus across the entire basin. Ozone injecting is also
available for enhanced oxidation of metals and the digestion of foul tasting organic material.
Aqua Sierra Inc. and ADS systems aeration technology is second to none in its oxygen transfer, mixing
potential, energy efficiency, and treatment capacity. At only a fraction of the cost of hypolimnetic systems,
our systems are easy to install and maintain, while they enhance the entire system verses just a
symptomatic area.
A Reputation for Excellence and Exceeding Expectations
With thousands of systems in the field, our satisfied clients will attest to the efficiency and effectiveness
of our systems. At Aqua Sierra Inc. we pride ourselves on not just meeting but exceeding your treatment
and fisheries goals. We stand behind the integrity and performance of our work and products and conduct
regularly scheduled maintenance to assure our clients' satisfaction.
Aqua Sierra Inc. is a complete Design/Build firm.
Contact our team of biologists and engineers today to learn how an Aqua Sierra Inc. & Air Diffusion
Systems clean water aeration system can benefit you and your resource.
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9094 US Highway 285, Morrison, CO 80465 -8950
(303) 697 -5486
(Toll Free) (800) 524 —FISH (3474)
FAX [phone]
http: / /www.aqua- sierra.com