§ 3.809. Percolation test.

(a)

Percolation Testing. Percolation tests to determine the absorption capacity of soil for septic tank effluent shall be conducted in accordance with this section and the results interpreted in accordance with this section.

(b)

Application Rates.

(1)

The percolation rate is the number of minutes for a one-inch drop after prewetting is noted.

(2)

The size of the subsurface disposal system can be obtained from the following table for individual residences except single-family dwellings on a shared system:

Conventional Single-Family Residential, Except Single-Family Dwellings on a Shared System, Subsurface Septic System Wastewater Application Rates

Percolation Rate Minimum per Inch	Application Rate gallons per day per square foot
Less than 2	Not suitable*
2—5	1.2*
6—15	0.8*
16—30	0.6*

 

*EPA Design Manual On-site Wastewater Treatment and Disposal System, U.S. Environmental Protection Agency, Office of Water Program Operations, Office of Research and Development Municipal Environmental Research Laboratory, October 1980.

(3)

The size of the subsurface disposal system can be obtained from the following table for commercial and institutional establishments and single-family dwellings on a shared system:

Conventional Commercial, Institutional, or Single-Family Dwellings on a Shared System Subsurface Septic System Wastewater Application Rates

Percolation Rate Minimum per Inch	Application Rate gallons per day per square foot
Less than 2	Not suitable*
2—15	0.8*
16—30	0.6*

 

*EPA Design Manual On-site Wastewater Treatment and Disposal System, U.S. Environmental Protection Agency, Office of Water Program Operations, Office of Research and Development Municipal Environmental Research Laboratory, October 1980.

Note: For commercial, industrial, or single-family dwellings on a shared system, advanced pretreatment may be used to resolve design issues and may increase the application rate, but in no case greater than 1.2 gpd/square feet.

(c)

Number and Adequacy of Observations. An adequate number of percolation and other pertinent observations, as required by the approving authority, shall be conducted within the area designated for the on-site sewage disposal system so as to determine that the area is suitable for sewage disposal. For each 10,000 square feet of sewage disposal area (proposed or approved) five percolation or observations are required proximate to the area designated for the on-site sewage disposal system. This may be waived or altered by the approving authority based on soil conditions.

(d)

Additional Testing. The approving authority may require additional percolation testing:

(1)

Where soil texture or structure varies or limiting geologic conditions are encountered; or

(2)

When the approving authority deems it necessary to evaluate a larger disposal and recovery area for the estimated sewage flow.

(e)

Rates Slower Than 30 Minutes. Percolation rates slower than 30 minutes per inch may not be approved except for conventional sand mounds, alternative sand mounds, and innovative and alternative systems.

(f)

Rates Between Two and Five Minutes. A percolation rate of between two and five minutes per inch after prewetting will require disapproval if the approving authority finds that adequate protection of the ground water may not be provided.

(g)

Distance from Groundwater. The bottom of the septic drainage system shall be at least four feet above ground water. The minimum separation distance may be increased when, in the opinion of the approving authority, additional separation is needed to protect groundwater or where seasonal fluctuations occur.

(h)

Time of Year That Tests May Be Conducted for Certain Soils. In areas where the soil survey maps or soil borings indicate moderate or severe limitations based on seasonally perched or seasonally high water tables, soil percolation tests and any other tests as may be required shall be performed at the time of the year when the highest water table can be expected at the on-site sewage disposal area, except as follows:

(1)

A repair; or

(2)

When there is evidence that a geological formation has a high and fluctuating water table during specified months of the year, the approving authority may specify the times during which the tests are to be made.

(Ord. No. 81, 2006, § 1)