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-.49 - Soil Maps

(a) Preliminary maps may be made using a wide variety of scales, but not smaller than 1:24,000. They usually provide sufficient information to make decisions about further land development. Minimum size delineation is approximately 3 acres. A preliminary soil map can be obtained from the USDA NRCS published soil survey. A preliminary soil map is a required part of Part 1 of the Site Development Plan. The map may be used in Part 1 of the Site Development Plan process and can come directly from the published survey or be made by a soil classifier. It is recommended that preliminary maps from USDA NRCS published soil surveys be reviewed and checked for accuracy by a Professional Soil Classifier. The preliminary maps from USDA NRCS published surveys may not be used in the place of soil maps required for site evaluation in Part 2 of the Site Development Plan.

(b) Low intensity maps show the location and extent of soils and landscape features sufficient for most Large-Flow planning but are not site specific to such a degree that allows for individual site determinations. Base maps are 1-inch equals 300 feet scale or larger. One soil observation pit per 3 acres is the minimum. Low intensity maps are excellent planning tools for Large-Flow Development and other areas where an OSS will be used.

(c) High intensity maps are the minimum level of intensity for soil maps when used in lieu of other evaluations or tests, i.e., percolation. The map scale shall be I-inch equals 100 feet or larger. High intensity soil maps can be used for individual lots or in a Large-Flow Development. A minimum of four borings per acre is required to delineate the soils. When a grid system is not used, the boring location shall be dictated by the landscape or in a manner to best define the soils that occur. All borings shall be flagged and numbered. When a high intensity soil map is used to evaluate a site for an OSS on an individual lot, the lot comers shall be staked and flagged, and the lot lines flagged at regular intervals in wooded or uncleared areas. If necessary, the owner shall mow or otherwise clear the site to facilitate the mapping process.

(d) Extra high intensity studies are an intensive soil morphological study that is site specific. A minimum of two borings is required per site. Soil descriptions shall be provided, and the soil classified to the series level whenever possible. Map boundaries are not necessarily required at this level of evaluation.

(a) Soils shall be classified according to U.S. Soil Taxonomy to the series level and map units shall generally consist of consociations. Complexes may only be used under very limited conditions when two or more dissimilar soils or soils and bedrock outcrops cannot be separated.

(b) Soil series boundaries shall be plotted on a map at a scale dictated by the intended soil mapping intensity.

(c) A high intensity soil map requires a carefully prepared base map on which the professional soil classifier shall accurately locate soil boundaries. A minimum of a 2-foot contour interval topographic base map is required for all high intensity soil maps.

(d) The minimum number of soil borings required for soil map(s) depends upon the variability of the relief and the complexity of the soils present.

(a) A title block or caption that states the project or client name.

(b) The date of the survey.

(c) A north arrow for orientation.

(d) The scale of the map including a visual scale.

(e) The soil mapping intensity (i.e., preliminary, high intensity).

(f) The signature, stamp or seal, address, and telephone number of the professional soil classifier.

(g) A special symbols legend, if needed, defining special features identified on the survey map (i.e., springs, rock outcrops, wells, sinkholes, gullies, etc.).

(h) The method by which borings are located on the map.

(a) The name of the soil series (or closest series with similar interpretations).

(b) The percent slope or slope range class.

(c) The depth to ASHES: see footnotes below Table 7.

(d) The depth to other restrictive layer or horizon.

(e) The assigned or adjusted permeability rate and depth at which it occurs.

(f) Additional notes and information as appropriate.

(g) Soil maps shall be color-coded with green for slight, yellow for moderate, orange for severe, and red for extreme.