The septic requirements are the same for all types of construction of the ADU (traditional construction, manufactured home, tiny home etc).
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To determine the septic requirements for an ADU/JADU Environmental Health staff will need to review the file for your parcel. Based upon the age of the system, sizing of the system and other required data our staff will determine the sewage disposal requirements for the ADU. More than likely, soils testing (perc and mantle) will need to be completed with Environmental Health and a private sewage disposal consultant. ADUs must be sized for a minimum of 2 bedrooms and be served by a separate septic tank.
If public sewer is physically and legally available within 300 feet of any portion of the property boundary the ADU/JADU will be required to connect to public sewer. Additionally, all structures on the property with plumbing would also be required to connect to public sewer as well.
An ADU must be served by a separate septic tank and the leachfield is required to be sized for a minimum of 2 bedrooms. If the existing septic system is not adequately sized and/or adequate data regarding the system does not exist, soils testing will be required to determine the sewage disposal requirements for the ADU.
The 100% repair area is an area designated on your property where a new leachfield would be installed at the time of failure of the current septic system. An adequately sized 100% repair area is required for all structures on the property. This area must be free of structures, grading, parking, driveways etc. and must meet all required setbacks.
In order to construct an ADU/JADU the parcel must be served by a potable water supply defined as either public treated water or a domestic water well drilled under permit. A domestic water well must produce a minimum of 1 GPM per residential unit. A 4-hour well yield dated within the last 3 years may be required to provide evidence of water quantity. Ditch water, spring water and hand dug wells are not considered a potable water supply. Parcels would be required to obtain a potable water supply prior to Environmental Health approval of the building permit for the ADU/JADU.