The Certificate of On-site Systems Approval (COSA), formally known as a health authority approval (HAA), is a certificate that is issued by the Municipality of Anchorage (MOA) which serves as confirmation to a lending institution that the well and/or septic system serving a single family dwelling have been inspected/tested by a professional engineer and were found to be in compliance with the applicable standards established by the Municipality of Anchorage.
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 and/or septic system, an HAA (now known as a COSA) 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.