Certificates of On-Site Systems Approval (COSA)

The Certificate of On-Site Systems Approval is issued by the Municipality of Anchorage (MOA) and serves as confirmation to a buyer and lending institution that the well and/or septic system serving a single family or duplex home have been inspected / tested by a professional engineer and were found to be in compliance with the applicable standards established by the MOA.

In August of 1998 the Municipal Assembly passed an ordinance requiring that in order to transfer a title on any property that is served by a well or septic system, a Certificate of On-Site Systems Approval must be obtained. The intent of the ordinance was to help protect the public health by insuring that septic systems are functional and not creating a health hazard. In addition, it ensures that well water quality is safe to drink and in sufficient quantity to meet the basic needs of the family purchasing the house.

Anchorage Municipal Code 15.65 requires a septic system to be sized based on the number of bedrooms in the dwelling unit(s) it serves, and assumes two occupants per bedroom. This sizing procedure is simplistic because: 

  • Many homes have rooms that can be used for more than one purpose, like an office or den that can also serve as a bedroom.
  • The number of bedrooms does not necessarily reflect the number of occupants. A home with six bedrooms may have two residents while a home with 3 bedrooms may have 8. 
  • Although a septic system that is undersized for the number of occupants may fail sooner than a properly sized system, the life of the system depends more on how a system is used and maintained.  

Even though this methodology is simplistic, it is the most practical means we have for sizing septic systems and has functioned for decades. Hence systems are approved to serve a certain number of bedrooms and this number is reflected on the COSA. This number of bedrooms may or may not match the number of bedrooms listed on the municipal tax records. 

For more information go to C.O.S.A. Guidelines.

The Certificate of On-Site Systems Approval inspection and testing process is summarized as follows:

  • Records of the well and septic system are obtained from the On-Site Water and Wastewater Section with the objective to verify if there is a documented and approved well & septic system on the property.  Undocumented  systems will be required to be documented prior to approval.
  • A copy of the as-built survey is reviewed to confirm the location of  the well and septic system.    
  • Standpipes are located.  The first step of the site evaluation is to determine if the septic system shown in the MOA records matches the actual installation at the property. All of the septic system pipes shown in the MOA records must be accounted for. This also applies to pipes buried in the snow.    
  • Field measurements are taken to verify that the required separation distances between all impacted wells and septic systems are in compliance with the separation distances in effect at the time the system was installed. If there are encroachments, then it will be necessary to apply for waivers. There are additional engineering services/charges and MOA fees associated with such waivers.  
  • Verify the well casing extends the required amount above grade. Wells drilled after August of 1998 must extend at least 18 inches above grade.  All other wells must extend at least 12 inches above grade.   
  • Verify the well wires are in conduit (protective pipe) where they extend above grade.    
  • Verify the well has a functional and removable sanitary seal.     
  • Verify from the well log and or field evaluation that the well is cased and unperforated in accordance with code in place at time of construction.    
  • Take water samples from the well and have them tested for nitrates, arsenic, and coliform bacteria.    
  • Verify the septic tank has been pumped and any lift station/pump vault maintained within the past 12 months.      
  • Perform well and septic system adequacy tests.    
  • Complete the standardized forms and submit them to the On-Site Water and Wastewater Section for their review and approval.