In 1998 a Certificate of On-Site Systems Approval (COSA) became required for all title transfers (except between spouses) of single family on-site wastewater disposal systems and for wells. This twenty year old process continues to be rigorously enforced by the MOA to protect the health and well -being of its citizens who elect to live in a home not serviced by public water and sewer. In order for a COSA, the acronym used in the industry, to be issued the following guidelines must be met:


1. An absorption field adequacy test has been performed within the last two years or the absorption field has been constructed within the last two years

2. The septic tank has been pumped within the previous year

3. The well has been flow tested within the last two years

4. The arsenic water sample results are less than one year old

5. The nitrate and bacteria water sampling results for private and Class C wells are less than 90 days old


A COSA is valid for two years from the date of the absorption field adequacy test or date of construction as long as the nitrate and bacteria water sampling results are less than 90 days old. Some additional requirements for septic tanks include no depression over any septic or holding tank. There must be at least one 4-inch diameter cleanout on each tank, and the cleanout must have an air tight cap. Septic tanks installed after 1980 must have two cleanouts. There should also be no evidence of heavy equipment movement over the absorption field. There may not be any driveways, parking areas or vehicle storage areas extending over or across any absorption field unless the engineer provides documentation that insures the integrity of the system.


Anchorage’s hillside is a popular move-up area. Last year 241 Anchorage homes sold with well and septic systems which were mostly on the hillside. Add Eagle River and that number jumps to 336.  Sometimes, there are unexpected surprises and costs. For example, an older home originally built with an unfinished lower level and then completed at a later time with additional bedrooms, a seller may find that the original septic was only designed for three beds, not the four or five that now exists, even though it appears to have been adequately working for their family and lifestyle.    


So how much does getting an approved COSA cost? The MOA inspection fee is $600. The permit fee to install a new tank is $250 and the cost for a design by an engineer is usually $700. Once the design and permit are obtained, the MOA requires three bids for the new tank, installation, top soil and seeding. Bids can vary anywhere from $10,000 to $30,000 depending upon the design. During the winter time, construction does not have to take place and a conditional COSA can be issued by the MOA once they have approved all of the above requirements. However, to sell a home requiring a new septic system an escrow will need to be established that amounts to one and a half times the cost of the highest bid. For more information, go to the Community Development Department on the MOA website.