COSA (Certificate of On-site System Approval
A COSA is required for the sale of any home with a septic system within the Municipality of Anchorage. The purpose is to protect public safety by ensuring that septic systems are working properly, and not contaminating wells or groundwater.
The COSA involves testing the well and septic system by a licensed Civil Engineer, submitting the certified paperwork along with some additional information from the homeowner.
The well test requires that the engineer take a water sample and submit it to the lab for analysis. This analysis typically takes business 10 days, although for an expedited fee the lab can finish it in 5 days.
The inspector also needs to physically inspect the well and take measurements, including a 4-hour flow test to calculate the well production.
The septic test involves adding water to the aborption trenches according to the number of bedrooms in the home, and verifying that this water is absorbed over a 24-hour period. The inspector will also take measurements of the system.
In addition, the municipality requires a receipt showing that the septic tank has been pumped within the past year. Most pumping companies are familiar with this requirement and can produce a receipt from their records upon request.
We can recommend several pumping companies that can quickly pump a tank if this has not been done.
Finally, the municipality requires an as-built signed by a licensed surveyor that shows all of the pipes from the system.
If the home has been sold in the past, and the system hasn’t changed, the municipality will often have an as-built on file that can be used.
If you would like to look up the on-site septic records for your home, you can do that here.
It is easiest if you have your property tax ID number or the legal description, which you can look up here.