Adopted Codes and Regulations for Septic Systems Septic ("OWTS") regulations and guidelines On-Site Wastewater Treatment Services - Regulation Revision - Effective 07-29-24 On-Site Wastewater Treatment Services - Setbacks (revised 07-07-2019) On-Site Wastewater Treatment Services - Connecting a Building Addition to Your Current System (revised 07-07-2019) Proposed On Site Water Treatment Regulations 43. This regulation will go before the board of health on 5/12/26. Mesa County OWTS Local Regulation pdf