The new State law is intended to reduce local agency regulatory barriers for Accessory Dwelling Units (ADUs) in order to increase the available housing supply. Considering that the maximum size of an ADU is only 1,200 square feet, this law would provide housing for small families of lesser means.
ADDED RECOMMENDATION TO THE PLANNING COMMISSION-APPROVED VERSION TO ELIMINATE THE REQUIREMENT FOR A SEPARATE SEPTIC TANK FOR ADUs
Residences which are on public sewer systems do not require separate sewer connections for ADUs.
In addition, Code 13.16.230/2 does not require separate septic tanks for attached two-family dwellings commonly known as Duplexes.
The question which arises is why a separate septic tank is not required for attached ADUs but required for detached ADUs?
NO ENVIRONMENTAL HEALTH REASON FOR A SEPARATE SEPTIC TANK FOR DETACHED ADUs
I had several contacts with Mr. John McDowell along with consultations with Ms. Kim Withrow (meeting on July 26, 2017). The initial guesses as to why this requirement was inserted in the Code were:
• When a septic tank fails (meaning it runs out of capacity) it is easier to detect the source of the problem.
• Attached ADUs usually have a common sewer line which discharges into the common septic tank.
Following further discussion addressing these concerns, it became apparent that when a septic tank runs out of capacity there is no advantage in determining whether it is the discharge from the main residence or from the ADU that caused it. In either case, the remedy is to empty the tank.
The fact that attached ADUs usually but not always share a common discharge sewer line into a septic tank is not a rational justification for requiring separate septic tanks for detached ADUs which themselves may not have separate sewer discharge lines.
Either way, neither of the above initial concerns turned out to provide any operational advantage to the proper function of two vs. one septic tanks provided the one is dimensioned as per the provisions of the Code from 1 to 10 bedrooms.
An environmental health issue arises only when a septic tank is allowed to become full beyond capacity or when a septic field is not functional. But septic field malfunction is unrelated to whether an ADU is attached or detached or whether there is one or two septic tanks.
SEPARATE SEPTIC TANK REQUIREMENT IS AN IMPEDIMENT TO THE STATE DIRECTIVE
The cost of a separate septic tank ranges from $ 12,000 if access conditions are ideal for a backhoe and a dump truck for the export of the displaced soil which at a minimum is 15 cubic yards (two ten-wheeler loads). Such cost can rapidly escalate to $ 25,000 and above if the site is inaccessible, requiring hand-digging, manual labor to carry all the dirt to a location accessible to a dump truck and the use of a crane for hoisting the septic tank to its otherwise inaccessible hole.
One must consider that residences on septic systems are overwhelmingly in the hills and constructed on slopes where accessible level ground is scarce making the disadvantageous location and the higher installation cost more typical.
Adding such cost to a structure of a maximum 1,200 square feet is an inordinate and unjustified penalty, one which is not founded on environmental health considerations.
One can speculate that at the time the Code adopted the requirement, its intent for whatever reason, was to discourage separate families from utilizing them as their homes, which is exactly contrary to the intent of the State's law.
NAPA COUNTY ADVANTAGES IN INCREASING THE SMALL HOME SUPPLY
In view of the fact that Napa county's economy provides the majority of its jobs to lower income families, it is especially important to the county's interest to make every effort to remove any unnecessary restrictions to the housing of such families. By eliminating the county's requirement for separate septic tanks to allow small kitchens in 1,200 homes can facilitate this objective.
I urge you to re-examine and eliminate this provision in the Code which perpetuates a serious financial impediment to the housing supply and is contrary to the State law objective.