Ala. Admin. Code r. 420-3-1-.61

Current through Register Vol. 43, No. 02, November 27, 2024

Section 420-3-1-.61 - Controlled Fill Mound Systems

(1)General Requirements. If site conditions and/or characteristics of a given lot prohibit the use of a Conventional OSS in accordance with the requirements of these rules, the LHD may consider approval of plans for the installation of a Controlled Fill Mound System. Controlled Fill Mound System designs may be considered only on sites where the fill selection, placement, natural ground surface preparation, and the entire Controlled Fill Mound System construction process is performed under the direct supervision of, and certified by, a professional engineer. The Controlled Fill Mound System shall be designed in accordance with this rule.

(2)Site Evaluation. Prior to placing the fill, the site shall be evaluated in accordance with the site evaluation criteria of these rules.

(3)Design Calculations. The engineer shall begin the design with the following considerations:

(a) Design Flow as per 420-3-1-.52 Design Flow and Wastewater Concentrations.

(b) Fill Material Loading Rate. This rate is applicable to Controlled Fill Systems utilizing LPP. See Table 13.

(c) Basal Area Loading Rate (BALR). The BALR is based on 420-3-1-.40 Soil Testing Depth Requirements paragraph (2).

(d) Hydraulic Linear Loading Rate (LLR). This rate applies to LPP designs. The Hydraulic LLR is an estimate of the amount of effluent in gallons per day (gpd) that will be dispersed per linear foot Qf) of LPP and is dependent on the direction and rate of effluent flow away from the Controlled Fill Mound System.

(e) Slope Correction Factor. This factor is necessary when the Controlled Fill Mound System is on a sloped lot and shall be applied using an appropriate value.

(4)Distribution Area Size. The distribution area is the space encompassing the EDF and shall be sized according to the type of EDF proposed.

(a) The distribution area for systems containing drip irrigation shall be sized to accommodate the amount of tubing indicated by Table 12. The drip irrigation field shall comply with 420-3-1-.62 Drip Irrigation Requirements.

(b) The distribution area for systems containing small diameter LPP shall be sized according to the fill material loading rate found in Table 13, when compared with the texture of the proposed fill material, the projected hydraulic linear loading rate (from a published manual) of the LPP when based on the upper horizons of the natural ground surface, and the design flow pursuant to 420-3-1-.52 Design Flow and Wastewater Concentrations. The distribution area shall have a minimum width of 3 feet.

1. The pipe distribution network utilizing LPP shall be configured based on a published manual and shall be time-dosed at least six times per day (24 hours) at regular intervals. A programmable timer and control panel shall be employed to regulate the dosing frequency and volume.

(c) The distribution area for other types of EDF (including 4-inch pipe with gravel) is based on the design flow pursuant to 420-3-1-.52 Design Flow and Wastewater Concentrations and the amount of EDF required, based on the permeability and soil textures found in the upper horizons of the natural ground surface. Specifications regarding trench widths, construction, materials, and distances between trenches, etc., are the same as required within these rules for any EDF installation.

(5)Absorption Area Size. The absorption area includes the distribution area plus the required setbacks of 2 feet for drip irrigation and LPP (5 feet for all other EDFs). These minimum distances are required between the shoulder of the fill (the beginning of the end or side slopes) and the nearest sidewall of the bed containing the LPP, the nearest drip tube or end, or the nearest EDF trench sidewall or end.

(6)Basal Area Size. The basal area is comprised of the footprint of the entire Controlled Fill Mound System over the natural ground surface. In addition to accommodating the required EDF amount in the distribution area and the absorption area setbacks, the basal area calculations shall allow for a 3:1 slope or flatter on both ends and both sides (from the shoulders of the fill down to the natural ground surface). When the Controlled Fill Mound System is placed on a sloped lot, the basal area shall incorporate the appropriate slope correction factor. Additionally, basal area calculations for designs utilizing LPP shall include the linear loading rate of the EDF pipes.

(a) For EDFs containing drip irrigation, the basal area shall be sized to accommodate the required amount of EDF, plus the absorption area, plus the required side and end slopes.

(b) For EDFs containing small diameter LPP, the basal area shall be sized according to the figures found in Table 14, or, to accommodate the total area encompassed by the distribution area, the absorption area, and the required side and end slopes (the larger of these two calculations shall be used).

(c) For any other type of EDF besides LPP and drip, the system shall be sized according to the amount of EDF pipe as required from the applicable sizing tables, the required separation distances (5 feet from sidewall to sidewall) between the EDF trenches, the required separation distance (5 feet) from the trench ends or outer sidewalls to the beginning of the Controlled Fill Mound System side or end slope, and the required side slope or end slope lengths (calculated by the product height) based on a 3:1 slope or flatter. No reductions are allowed in the basal area size when based strictly on the type of disposal product.

(d) Basal area sizing for Controlled Fill Mound Systems in high shrink-swell soils (Vertisols or soils with vertic characteristics), or mine spoil shall be as follows:

1. For EDFs containing drip irrigation, a loading rate of .05 gallons per day per square foot (0.05 gpd/sq. ft.} of tubing shall be used.

2. For EDFs containing small diameter LPP, a basal area loading rate of 0.075 gallons per day per square foot (0.075 gpd/sq. ft.) shall be used.

3. For any other type of EDF besides LPP and drip, the minimum EDF amount (and basal area sized to accommodate the EDF) when the effluent entering the Controlled Fill System has received primary treatment shall be based on a minimum percolation rate greater than 180 MPI. Should any portion of the area proposed for the Controlled Fill System yield a higher percolation rate, then that rate (See Table 3) shall be used for the design.

(i) When the effluent entering the Controlled Fill Mound System has received secondary treatment, the minimum EDF amount, the distribution area sized to accommodate the EDF, and the absorption area (to the side or end slopes) may be reduced according to the figures in Table 3. The minimum basal area footprint shall remain as calculated for a Controlled Fill Mound System design receiving non-treated effluent.

(7)Fill Material. Soil used as fill material shall be approved by the design engineer. Table 16 shall be used.

(a) Fill material suitable for use in Controlled Fill Mound System installations shall be commercially available material, material that meets the appropriate ASTM standard for fine aggregate (concrete sand) and others to be approved by ADPH or naturally occurring material such as top layers of some soils and soils from pits located in areas having deep sandy to loamy deposits.

(b) Uniformity of the fill material used for the Controlled Fill Mound construction is essential. The fill shall be free of trash and debris and shall be certified by the engineer as being consistent (with respect to texture and compaction) throughout the construction.

(c) Where possible the fill material shall be compatible with the existing in-situ soil.

(8)Construction of the Controlled Fill Mound. The natural ground surface shall be properly prepared to receive the fill material. Trees within the proposed area shall be cut flush with the ground and stumps left in place unless the engineer determines this is not in the best interest of the system. In such case, the engineer shall address the existing or proposed ground clearing in the design. Where possible, large rocks shall also be left in place. Brush and vegetation shall be removed, taking care not to compact the original soil surface, which shall be scarified to a depth of 6 to 18 inches. Clay soils may require a minimum scarification depth of 18 inches to obtain a proper soil interface. The scarification process shall be accomplished utilizing proper equipment so that the soil structure is not destroyed, and the root mat is removed from the natural surface. A chisel plow or chisel teeth mounted on a tool bar attached to the backhoe bucket is recommended. Tillers, moldboard plows, and backhoe bucket teeth are not recommended.

(a) Compaction and Placement of the Fill. The fill material shall not be moved, placed, disturbed, nor constructed if the material and/or the natural ground surface is wet. The fill material shall be placed in lifts not exceeding 6 to 12 inches and compacted to a proper density to promote stability while allowing for the vertical movement of efiluent. The fill shall be placed from the upslope side, if applicable, or from the edges, with care taken not to create ruts or compaction. A track type tractor, or similar, shall be used to move around and/or across the Controlled Fill Mound System site, but other vehicles may be used to install field lines if the fill is not excessively compacted. The final cover shall include a minimum of 6 inches of topsoil material (properly crowned) placed over the fill material so that a vegetative cover can be established. The Controlled Fill Mound shall be seeded and mulched to avoid erosion.

(b) Engineer's Certification of the Controlled Fill Mound Construction. Following the placement of the fill and construction of the mound but prior to the installation of the EDF, the engineer shall certify the fill material using ADPH Form CEP-6, Part B. Fill material permeability shall be verified by the design engineer. After the fill material is placed, a percolation or permeameter test shall be done in the fill. The test results, upon request, shall be submitted with the engineer's fill certification.

(9)Controlled Fill Mound System Vertical Separation Requirements.

(a) For system designs other than for drip irrigation, no EDF bottom shall be located between O and 5 inches above the natural ground surface.

(b) System designs on sites with less than 6 inches to ASHES shall, at a minimum, be required to treat effluent to secondary effluent standards prior to discharge into the Controlled Fill System Mound.

(c) System designs on sites with less than 12 inches to bedrock shall, at a minimum, be required to treat effluent to secondary effluent standards prior to discharge into the Controlled Fill System Mound.

Ala. Admin. Code r. 420-3-1-.61

New Rule: Filed October 20, 2005; effective November 24, 2005; operative March 19, 2006.

Adopted by Alabama Administrative Monthly Volume XXXV, Issue No. 04, January 31, 2017, eff. 3/5/2017.

Adopted by Alabama Administrative Monthly Volume XLI, Issue No. 03, December 30, 2022, eff. 2/13/2023.

Previous Rule .94 was renumbered .61 per certification published December 30, 2022; effective February 13, 2023.

Author: Thad Pittman, Matthew Conner, Ken Stephens, Bob Bright

Statutory Authority:Code of Ala. 1975, §§ 22-2-2(4); 22-2-2(6); 22-10-1, et seq.; 22-26-1et seq.