Section 480. Soil profiles and patterns

A. General. The purpose of determining the soil profiles and patterns is to identify the soil characteristics that affect installation of a subsurface soil absorption system.

B. Soil profile. A soil profile is a vertical section of the soil throughout all its horizons.

C. Profile holes.

1. Acceptable equipment.

a. Auger. An auger is defined as a mechanical device which is used to remove a soil sample for evaluation. Devices utilizing the Archimedes screw principle are prohibited because they blend and mast the true soil characteristics.

b. Other equipment. Other equipment may be used in addition to an auger to expose the soil profile as long as it does not mask or blend the true soil characteristics.

2. General location of profile holes. Profile holes to determine design requirements shall be located in the area that is unrestricted by the criteria contained in Part IV (12VAC5-610-591 et seq.) of this chapter and Table 4.2. Additional profile holes outside the unrestricted area may be required to make a complete evaluation of the site.

3. Depth of profile hole. The minimum depth of the profile hole shall be five feet unless prevented or made unnecessary by some physical feature of the soil such as gray coloration, rock or when a potential horizon is found at a lesser depth. Where a potential soil horizon is considered for use, the soil evaluation shall be extended below the potential horizon to assure that there is no interference with seasonal water table, rock or impervious strata (See Tables 4.3 and 4.4 of this chapter).

4. Number and location of profile holes. A minimum of five holes is necessary to determine the design requirements of an area for the placement of absorption trenches. Where there is uniform topography and the profile holes exhibit a uniform profile, a minimum of three holes is necessary. The size of the area investigated shall be based on the soil texture group encountered. As a minimum, holes shall be placed to be representative of the area under consideration for placement of the absorption trenches.

If more than one area is required in which to install the absorption trenches, each area shall be evaluated as described above. If any proposed absorption trench site is found unacceptable due to soil conditions, the site shall have been evaluated with a minimum of three holes which characterize the soil problem or problems and support the reasons for rejection. The actual area and number of holes to be investigated may be more than described above and shall be determined on a case-by-case basis.

5. In situations where a large area is to be evaluated, where the soil is highly variable, where the profile must be exposed below five feet or where the soil is "tight" (dense or compact) and/or rocky, the district or local health department may require that the owner have the soil profile in selected areas exposed by the digging of trenches, auger holes or pits. The actual area and number of holes to be investigated shall be determined on a case-by-case basis.

D. Soil profile documentation. Soil profiles shall be determined and a record made in writing of each boring. Additional documentation may be required by the district or local health department.

Historical Notes

Derived from VR355-34-02 § 3.4, eff. February 5, 1986; amended, eff. May 11, 1988; Volume 16, Issue 16, eff. July 1, 2000.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.