Water Production & Distribution

High Quality Raw Water Sources

Anchorage is indeed fortunate. While some regions of the U.S. struggle to protect water sources, Anchorage is virtually free from such problems. Its two major water sources, Eklutna Lake and Ship Creek, provide a continual supply of water free from manmade pollutants.

The nation has become concerned with a decline in drinking water quality associated with growth and industrial development. The need to protect the public's health and minimize costs of providing public water equate to Watershed Quality Management. The protection of source water supplies, both in the present and future, are huge management issues in the Lower 48. Anchorage's watersheds are part of the Chugach Mountain Range and within the Alaska State Park system. Natural barriers and existing park regulations protect both water sources from activities that may adversely impact the water supply.

Water Sources

AWWU must ensure our customers receive high-quality water that meets all public health standards, regulatory requirements and is available at the lowest possible cost. AWWU's Ship Creek Water Treatment Facility and Eklutna Water Treatment Facility process surface water from two local water sources.

The Eklutna Water Treatment Facility has a production capacity of 35 mgd. It diverts its water from Eklutna Lake, which is also recharged from a large watershed within the Chugach State Park. Water from Eklutna is delivered through a buried pipeline to Peters Creek, Chugiak, Eagle River and Anchorage.

Ship Creek Water Treatment Facility has a production capacity of 24 million gallons per day (mgd). It diverts water from an impound dam on upper Ship Creek. The dam is recharged from a protected watershed in the Chugach State Park.

AWWU's well system consists of 18 deep wells located throughout the Municipality. They generally serve as stand-by sources to meet peak water demands and emergencies.

Eklutna Lake Raw Water Quality

Eklutna Lake's drainage area is approximately 119 square miles within the Chugach State Park. It includes Eklutna Glacier. The lake has a surface area of 3,420 acres and a total holding capacity equal to 213,271 acre-feet of water. An acre-foot is equal to approximately 326,000 gallons. The lake has a maximum depth of 200 feet.

Eklutna Lake is an exceptional source of raw water for Anchorage. Its physical characteristics reflect its pristine nature. Throughout the year, the lake's water temperature varies between 39 and 52 degrees Fahrenheit. It is moderately soft water with a pH range of 7.7 to 8.3.

Annual melt from Eklutna Glacier is a major contributor to the lake's inflow. It also adds to its turbidity. Raw water turbidity ranges from a low of 4.0 NTUs in winter to a high of 70 NTUs in summer.

The Eklutna Water Treatment Facility produces water with a clarity that routinely surpasses drinking water standard by over 500 percent. The current national standard is set at less than 0.3 NTU for 95 percent of all samples, treated with either conventional and direct filtration. AWWU's own internal standard is more stringent and strives to not exceed 0.1 NTU.

Ship Creek Raw Water Quality

The Ship Creek watershed established on April 19, 1919 by Presidential Proclamation 1519. Ship Creek drains approximately 100 square miles of the Chugach Mountains, beginning at an elevation of 5,100 feet. The watershed is also part of the Chugach State Park. Various natural characteristics of the Ship Creek watershed have a significant impact on its water quality. Ship Creek's water is moderately soft, with an average pH of 7.5.

Because of seasonal influences, the flow and water quality of Ship Creek vary widely. Turbidity ranges from a low of less than 1.0 Nephelometric Turbidity Unit (NTU) to more than 600. This is due to naturally occurring organic compounds, color and metals which increase each spring when the snow melts. Even though the Ship Creek watershed is almost pristine, water management philosophy is to treat our source water supplies as if they are contaminated with organisms. As a result, treatment is optimized to minimize any possible adverse exposure to the public.

Water Treatment

Natural water supplies must go through several treatment steps to ensure safe and pure drinking water. The water treatment process begins with flocculation/coagulation when a chemical, such as aluminum sulfate or ferric sulfate, is added to the water. As the alum or ferric dissolves, dirt and other minute particles become sticky and cling to one another. This is floc. Under its own weight, the floc sinks to the bottom of the treatment tank.

During the next step, the sedimentation process, the clear water above the floc is skimmed off and separated prior to filtration. In filtration, water passes through layers of sand, gravel and charcoal to remove any remaining impurities.

Before the water is placed in the pipeline for distribution, a small amount of chlorine and fluoride is added to the finished water. Chlorine assures the bacterial levels are safe for drinking and improves its quality. Fluoride is added and increases the natural amount of fluoride in the drinking water to a level recommended by the EPA, to reduce tooth decay.

With the exception of chlorine and fluoride, all chemicals are added to the water for the purpose of meeting clarity, taste, odor and corrosion standards.

EPA's regulatory standard for finished water requires a turbidity reading of less than 0.5 Nephelometric Turbidity Units (NTUs). AWWU operates under a more stringent self imposed standard, not to exceed 0.1 NTUs, to assures even better water quality. When chemicals are added to remove turbidity, minute residuals remain, however, they are only be detectable in the finished water by laboratory analysis.This is an unavoidable by-product of the treatment requirement. The term additive is given to these residuals.

Anchorage Water and Wastewater Utility adds the following chemicals to its water supply:

• Aluminum Sulfate, commonly known as alum, and Ferric Sulfate, are added as primary coagulants, to remove organic and inorganic turbidity. Federal and state laws require that public water supplies maintain a specified standard of clarity, measured by Nephelometric Turbidity Units (NTUs). The clarity standard is for removal of particulate matter that may be able to harbor or sustain the growth of bacteria in water.
• Lime and Soda Ash are added as secondary coagulants. These aid in turbidity removal and adjust the pH of the finished water. They establish opposite electrical charges for a chemical reaction with the primary coagulants. As pH adjusters, they regulate the acidity of the finished water in the distribution system. The standard within AWWU is to maintain slightly alkaline finished water. This reduces the corrosiveness of the water and helps preserve the distribution system. It also reduces the chance of potable water reacting to customer uses which may create undesirable effects.
• Chlorine is added to assure the bacterial safety of the drinking water. A residual is maintained to ensure the wateris not contaminated while in storage or while in transit within the distribution system.
• Fluoride is added to meet the EPA's recommended fluoride level and help reduce the incidence of tooth decay.
• Polymer is added to the water to insure better filtration and coagulation. Polymers are FDA-approved chemicals used to reduce the amount of alum, lime, ferric sulfate and soda ash that is needed in the turbidity removal process.

Concentrations of these chemicals in the water will vary over time. The variations are measured in fractions of a milligram per liter. The variations occur with changes in water sources and accuracy of the treatment equipment at each distribution source. AWWU maintains a stringent documentation record process to ensure these controls are in place.

Storage, Transmission And Distribution

Surface water from Ship Creek and Eklutna Lake is treated and distributed mainly by gravity through 670 miles of transmission and distribution mains. A few isolated areas require booster pumping facilities to maintain adequate pressure throughout the distribution system. The diameter of the mains range in size from four to 60 inches. Water from deep-aquifer wells is used to supplement system demand. The Eklutna Water Treatment Facilities is the major source of water for Anchorage. Ship Creek and the wells are generally used as a back up source. A network of water reservoirs help provide water storage for fire demand and emergency reserves.

Girdwood Alyeska Utilities
Public Water System (PWS) Indentification Number - 212021

Girdwood’s Water System is comprised of two wells, a one million gallon reservoir and seven miles of water distribution lines. The distribution system is in a glacial mountain valley that takes six water pressure zones and is served by two booster pump stations and two pressure reducing vaults. There are 68 public fire hydrants in Girdwood. The source water is of glacial origin with no turbidity and excellent taste. The water system serves the Alyeska and Alyeska Basin Subdivisions and the Alyeska Prince Hotel and Resort.

Girdwood’s Treatment staff hold Alaska certifications in water treatment, water distribution and wastewater treatment. They also perform Customer Service and Field Service duties.

Knik View Water System
Public Water System (PWS) Indentification Number - 218409

An artesian well has served this "stand alone system" in Peters Creek since 1985. AWWU purchased the system in 1996. Two years later, AWWU built a 60,000 gallon reservoir and booster station. These improvements increased the water pressure for customers at higher elevations. AWWU has an application pending with the Alaska Department of Natural Resources to increase the water rights and water service area for the potential of additional private development in the Knik Vista area.