Alabama Administrative Code
Title 420 - ALABAMA STATE BOARD OF HEALTH
Chapter 420-3-1 - ONSITE SEWAGE TREATMENT AND DISPOSAL
Site Evaluation
Section 420-3-1-.38 - Slope And Landform Limitations

(1) EDF sites with slopes greater than 25 percent require an Engineer Design. EDF sites with slopes greater than 40 percent are considered unsuitable for the installation of an OSS. Table 8 shall be consulted for the required trench spacing and required amount of cover needed for a Conventional OSS.

(2) Slope limitation ratings are found in Table 18. See 420-3-1-.51 Lot Modification - Planned and Unplanned, for options for manipulating steep slopes to overcome severe or extreme ratings.

(3) Prior to any cutting and/or filling operations, refer to 420-3-1-.61 Controlled Fill Mound System, and 420-3-1-.51 Lot Modification-Planned and Unplanned.

(4) Drainage ways shall not be filled for the purpose of creating an acceptable EDF or REDF. See Drainage Way and Table 4.

(5) Sites with caves, sinkholes, and similar depressions within 300 feet of the EDF or REDF that are likely to be impacted by the sewage from the system shall be rated extreme. The LHD may consider allowing OSS components in locations less than 300 feet from these features upon receipt of a report prepared and certified by a geologist. This report shall specifically address the susceptibility of contamination of both surface and groundwater by an OSS based on the existing conditions. However, no part of the system shall be allowed within 50 feet of the rim on any sinkhole.

(6) Any site rated extreme because of wetlands, hydric soils, or ponding is considered unsuitable for an EDF except when the conditions of 420-3-1-.61 Controlled Fill Mound System, and 420-3-1-.51 Lot Modification - Planned and Unplanned, apply. Frequently flooded areas are considered unacceptable for an OSS.

(7) Sites that are in a flood easement are considered extreme and are unsuitable for an OSS/EDS.

(8) Natural and artificial landforms such as filled areas with excessive voids (including mine spoil areas) require special consideration because of the high potential for contamination.