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Sunday, January 21, 2018

Advanced Wastewater Treatment Systems (AWWTS)


Advanced Wastewater Treatment Systems (AWWTS)

There are a number of locations in the Anchorage and Eagle River area where site conditions are unsuitable to support a conventional onsite septic system. In the past, many of these areas were developed, only to find out later that the septic systems would not function properly. Many of these homes have since been put on holding tanks, and others are utilizing some alternative technology systems which are now available. Before determining what systems are viable for any particular lot, there must be a thorough engineering evaluation of the site conditions. Conditions which may prevent the installation of a conventional septic system are summarized as follows


  • The topography is too steep (slopes greater than 25%): Under current regulations, the drainfield must be at least 50 feet away from a downhill slope greater than 25%. The MOA will waive this on a case-by-case basis.
  • Shallow groundwater:  Typically, the bottom of a drainfield must be at least 4 feet above groundwater.  With the use of an AWWTS it is possible to get this separation distance reduced on a case-by-case basis.
  • Soils which percolate too slowly: If the percolation rate is between 60 and 120 minutes per inch, then an AWWTS will be required. If it takes greater than 120 minutes for the water level in the perk hole to drop 1 inch, the soil is unsuitable for any type of septic system.
  • The protective well radius' encompass all of, or a major portion of, the land area necessary to install a conventional septic system:
    1. Private wells (single family residence and duplexes) have a 100 foot protective radius
    2. Class "C" wells (serving less than 25 people) have a 150 foot protective radius
    3. Class "A" or "B" wells (generally these are wells serving greater than 25 people per day for more than 60 days per year) have a 200 foot protective radius
  • There are nearby surface waters, such as creeks, ponds, lakes, etcetera: The septic system must be at least 100 feet away from any surface water, unless mitigation is provided.
  • The area groundwater supply has high concentrations of nitrates (by-product of sewage decomposition), causing the MOA to mandate the installation of nitrogen removing AWWTS
  • Very shallow bedrock: Typically, the site must have at least 2 feet of naturally occurring, permeable soil over the bedrock.

    If site conditions prevent the installation of a conventional septic system, then it may be possible to install one of the alternative technology systems, referred to in Anchorage as "Advanced Wastewater Treatment Systems (AWWTS)". The systems currently being used in the Anchorage and Eagle River area are as follows:


    We would be happy to do a full engineering evaluation of your property and recommend the septic system which best meets your needs.

Order Forms

All costs associated with obtaining a Certificate of On-site Systems Approval (COSA) from the Municipality of Anchorage (MOA) are subject, but not limited to, the following conditions at the time of testing:

  • A legible copy of current as-built survey is provided.
  • All septic pipes are present and exposed (not buried underground or in the snow).
  • All septic pipes are functional (not broken off below ground, or filled with dirt/rocks).
  • The well production is adequate enough to fill the septic system in a reasonable amount of time.
  • The septic tank is pumped per engineer's direction.
  • If the house has been vacant in excess of 30 days, the leachfield will need to be presoaked. There is an additional charge for this service.
  • Well head is accessible and the sanitary cap is functional and removable.
  • Please click here for a detailed disclaimer.

Fill out the selected PDF form and fax or email it to our office, we will call you back to confirm your order. (907 338-3246)

Certificate of On-Site Systems Approval

Well and/or Septic Adequacy Test

Soils Evaluation and Percolation Tests

Engineering Costs and Fees

For undeveloped land, in most cases it will be necessary to have the lot lines flagged by a registered land surveyor (about every 50-75 feet) prior to digging any test holes. In addition to having the property lines flagged, it is necessary that a "site plan" (see below) be developed by GEG.  Prior to doing any design work, it will be necessary to have a legible copy of a current as-built survey, or for new construction, a certified plot plan.  GEG does not provide land surveying services and all surveying costs are in addition to the following fees.  GEG has a list of recommended surveyors we can refer you to.

General Consulting Services

  • Senior Professional Engineer (Jeffrey Garness, P.E.) - $200/hr.
  • Professional Engineer - $150/hr.
  • Engineering Technician - $125/hr.
  • Administrative Services - $65/hr.

Septic Design Services for a Private Septic System in the MOA

  • Site Plan - Required before any test holes or soil analysis can be performed:  $125 per hour, plus surveyor fees so as to establish lot line control and "asbuilt" surface waters, wetlands, topography, and all other pertinent features necessary to design the well and/or septic system
  • Soil Analysis - Includes percolation test and groundwater monitoring for one test hole:  *$700, plus test hole excavation fee
  • Soils Analysis for Additional Test Holes (if performed during the same site visit):  *$400 per test hole, plus test hole excavation fees
  • Septic System Design (for single-family home or duplex in the MOA):  **$900
  • Septic tank only design:  $750

Test Hole Excavation Services in the MOA

  • Test Hole (if a rubber tire backhoe can be used) - *$700
  • Additional Test Holes (done on the same day as the 1st test hole) - *$400/each

Municipality of Anchorage Fees

  • Septic system installation permit - $569
  • Well permit - $215
  • Certificate of Onsite Systems Approval (COSA):  $526
  • Municipal Rush Fees:  Additional 60% charge to all MOA fees
  • MOA or ADEC waiver fees:  Varies depending upon type of waiver

The MOA fee schedule is subject to change without notice; furthermore, GEG charges a 5% markup on all MOA fees paid by GEG on behalf of client.

Inspections & Documentation of Private Septic Systems in the MOA

  • Contact our office for price information


*Additional fees for travel time may apply if the site location is further south than Potter Marsh, or further north than Peters Creek.  Some sites require extensive tree removal or construction of an access trail into the site.  Tree removal and/or access trail construction is not included in this price.  If the site topography or vegetation (tall trees and/or alders) makes the use of a rubber tire backhoe unfeasible, it may be necessary to use a track type backhoe.  There is an additional fees if a track type backhoe is required, or if tree clearing or other work is required to provide reasonable access to the property.

**Does not include preparation of waiver reports nor MOA/ADEC waiver fees or MOA permit fees.




If the site conditions are so poor that neither a conventional septic system or an Advanced Wasteater Treatment System (AWWTS) can be installed, then a holding tank is the only viable option. A holding tank is a steel, water tight, tank, without an outlet. The typical size, for a private residence, varies from 2000 to 4000 gallons. All of the wastewater generated from the home goes into this tank, and once it is full, it must be pumped out. The system is equipped with a high level alarm (located within the house) to notify the residents when the tank is full.

The cost of installing a holding tank varies depending on the site conditions, but one can expect to pay from $10,000 to $15,000, including engineering, permit fees, and installation costs. Although a holding tank is significantly less expensive to install than an AWWTS, it costs more to operate. Depending on water useage, the holding tank may have to be pumped several times per month.

Pumping Costs

Municipal design standards conservatively dictate that a septic system be sized to handle 150 gallons per day per bedroom (which equates to 2 people per bedroom using 75 gallons per day each). Through the use of flow restrictors on the sinks/showers, low volume flush toilets, and the optimum utilization of the dishwater and washing machine (washing only full loads), the flow rates can be significantly reduced, perhaps as low as 35 gallons per day per person. Since approximately 40% of the wastewater generated on a daily basis comes from flushing toilets, anything which can be done to reduce toilet flushing volumes will have a significant impact. The installation of composting toilets, or urinals would be an extreme example of the steps one could take to reduce wastewater volume. 

Because the homeowner must pay for the removal and disposal of every gallon of wastewater, it is imperative that water conservation be practiced. The cost to pump a tank will vary depending upon the size of the tank, the location (accessiblity), and the season of the year. For a 4 person family, served by a 4000 gallon holding tank, assuming 40 gallons per person per day, the tank will have to be pumped every 25 days. This corresponds to 15 pumpings per year (assume $250/each) for a total annual cost of $3,750.

Something to Consider

Although the cost of operating a holding tank may be more than a conventional septic system or an AWWTS, it is not necessarily more expensive to own when one considers the capital and operating costs combined. In short, the owners of such systems will have periodic repairs (new pumps, air compressors, electrical components, etc.) as well as the possibility of having to periodically upgrade portions of the system, such as the drainfield.

Holding tanks, unlike septic systems, have no components to fail, other then the alarm, and their useful life expectancy is about 20 years (the tank eventually rusts out and starts to leak). The only costs associated with owning a holding tank is the original capital cost, and the monthly pumping costs. When these costs are weighed against some of the higher priced AWWTS systems, it becomes clear that holding tanks are perhaps unjustly stigmatized. Another redeeming quality regarding holding tanks is that they, unlike septic systems, are 100% reliable.

If you find yourself in the position of marketing or buying a home with a holding tank, perhaps the most important thing you can do is educate yourself regarding the economics of operating a holding tank and weigh those costs against the capital costs associated with installing a conventional septic systems or an AWWTS system. In some cases, you will find that a holding tank is the most economical solution.

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Garness Engineering Group, Ltd is a 100% Native American owned business enterprise.

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