Ala. Admin. Code r. 420-3-1-.51

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

Section 420-3-1-.51 - Lot Modification - Planned And Unplanned

(1)General Requirements. Lot modification is the planned or unplanned changing of a lot characteristic that shall impact the EDF.

(a) Planned lot modification shall be accomplished under the supervision of an engineer and in accordance with the applicable sections of these rules to make a lot more conducive for use of an EDF. An OSS for a lot that has been proposed after lot modification shall be designed by an engineer when required.

(b) Unplanned lot modification can make a lot unsuitable as a site for an OSS or EDS. In these situations, the lot to be used shall require additional steps to return it to a useable state. If this is possible, the additional steps required shall be determined by an engineer with the concurrence of the LHD except under (3)(a) and (3)(c) of this rule.

(c) Lot modification, as it impacts the use of an EDF, usually involves the use of fill. Fill is material that is used to modify a lot by filling cuts or is material that is placed over in-situ soil to increase the height of the existing ground surface. Fill can be appropriate or inappropriate for use with an OSS.

(2)Fill Requirements.

(a) Fill that has been in place for more than 5 years over soils that are not surface saturated soils shall be evaluated in accordance with the provisions of these rules. However, additional percolation tests, permeameter tests, observation pits, or soil borings may be required at the discretion of the LHD to determine consistency and compaction of the fill throughout the proposed EDF area.

(b) Fill that has been in place for less than 5 years over soils that are not surface saturated soils, shall be evaluated by a PSC for confirmation of fill characteristics (formation of redoximorphic features, evidence of pedogenesis within the material, consistency, uniformity, compaction, etc.) and description of the original soil underneath the fill. The description shall address characteristics as outlined in the current USDA Keys to Soil Taxonomy. The PSC evaluation shall be submitted on ADPH Form CEP-2/3 Part C. Additionally, the fill must be in place for a period extending through at least one wet season during which average precipitation amounts were experienced. The responsible person shall provide this documentation. The LHD may consider information from the National Weather Service in determining compliance with the normal or average wet season requirements.

(c) Fill that has been in place over surface saturated soils for more than 5 years may be evaluated during the wet season and in accordance with these rules. The LHD or ADPH may, at their discretion, require additional percolation tests and soil borings to determine consistency and compaction of fill throughout the proposed EDF area.

(d) Sites with fill that has been in place over surface saturated soils less than 5 years or sites where fill will be placed over surface saturated soils, with engineer oversight, shall be evaluated by the following criteria:

1. As applicable, prior to filling a jurisdictional wetland, the responsible person shall first receive documented approval to fill the wetland from the U.S. Army Corps of Engineers or other appropriate agency.

2. Fill shall be in place for a period extending through at least onewet season during which average precipitation amounts were experienced, with the site being monitored during this period. The monitoring may be accomplished by use of properly spaced observation wells which are inspected on a weekly basis. The results of these observations shall be certified by a professional engineer, professional soils classifier, or a professional geologist. The monitoring shall be accomplished using two observation wells for every 500 square feet of EDF. Placement of the wells shall be evenly spaced with one well up gradient and one well down gradient for sloping sites. These wells shall be constructed such that water levels are measured every 7 days with a minimum of 20 recordings. Sites on which there is evidence of water rising into, or perching within, the ass shall be designed to secondary effluent standards and maintain an MVS of 12 inches. If no water is observed, the ass shall be designed in accordance with appropriate sections of these rules.

3. The responsible person shall provide documentation that verifies that average precipitation amounts were experienced during the monitoring period, see paragraph (2)(b). The responsible person shall provide documentation pertaining to the amount of time that the fill has been in place. This shall be accomplished by one of the following methods:

(i) The approximate age of the fill based upon the effects of soil development (or lack thereof), determined by a PSC.

(ii) A document (sales invoice, construction billing, etc.) indicating dates and appropriate information such as when fill was placed.

(iii) A method approved by the LHD or the ADPH.

(e) Proposed EDF sites or discharge areas that contain fill material other than soil shall not be considered for the installation of an OSS or EDS.

(3)Cut Requirements.

(a) Design proposals which use cuts with fill placed below the natural ground surface (Deep Excavation with In-Ground Fill) may be used on sites with less permeable soils overlying Texture Group 1 or 2 soils where the construction of a Conventional 08S below the more restrictive layer or horizon is not practical..On such sites, the less permeable soil within the EDF may be stripped away, replaced with a suitable fill material (sand [S], loamy sand [LS] or sandy loam [SL]) which is compatible with the underlying soil, and the EDF installed, provided that the following conditions are met:

1. The site is not located within an area containing high shrink-swell soils, or mine spoil.

2. The existing underlying soils shall be Texture Group 1 or 2 soils, and contain a minimum thiclmess of 36 inches, with ASHES or bedrock no closer than 12 inches to the top of this layer.

3. The design proposal shall provide for a minimum of 24 inches of suitable fill below the bottom of the EDF. The total exposed trench depth after filling shall not exceed 60 inches.

4. The engineer, with concurrence of the LHD or ADPH, shall determine the depth at which the size of the EDF is based.

5. The design proposal shall include advanced treatment.

6. The design proposal is not for waste containing high strength sewage.

7. The OSS design shall contain instructions for removal of the unsuitable material in such a manner as to prevent compaction or disturbance of the underlying material.

8. The OSS design shall contain instructions for preparing the top 6 inches of the existing, in-situ material (under the fill) to provide an acceptable interface with the fill material. The OSS design shall provide a minim.um separation distance of 8 feet (on center) between each EDF pipe (2 feet if small diameter, LPP is used).

9. The OSS design shall have a minimum separation distance of 10 feet (8 feet for LPP), as measured from the side of the outer EDF walls, (or pipe ends) to the outer edges of the fill material (i.e., the sidewall of the cut soils).

10. Provisions have been made to intercept any sub-surface water outside the cut area from flowing into the filled area.

(b) Design proposals which use cuts with fill over the newly exposed surface (surface cut with fill above ground) shall comply with 420-3-1-.61 Controlled Fill Mound System.

(c) Design proposals which involve altering ("bench cut," etc.) a lot with severe (greater than 25 percent) or extreme (greater than 40 percent) slopes to accommodate an EDF are subject to the following requirements:

1. "Cut" material which has been moved to the down-slope side shall not be considered a suitable site for installation of an EDF.

2. The cut (benched) area, when proposed as the EDF site, shall require a high intensity soil map prepared and certified by a PSC, which addresses the impact the cut may have on the proposed EDF and REDF.

3. Sites containing continuous hard bedrock at the newly exposed surface (the cut or benched area) shall not be considered for the installation of an EDF.

4. Sites containing other restrictive rock types at the newly exposed surface may be considered for a Controlled Fill System installation (see 420-3-1-.61 Controlled Fill Mound System), provided that the design includes the following:

(i) The design proposal shall include advanced treatment.

(ii) A minimum separation distance of 24 inches between the trench bottoms and the newly exposed surface.

(iii) Use of small diameter pipe (LPP) providing low pressure disposal of effluent.

(iv) A minimum separation distance of 50 feet from the point where the Controlled Fill System side or end slope meets the newly exposed surface, to the end of the cut or benched area (i.e., the point where the cut meets the natural ground surface of the original slope).

Ala. Admin. Code r. 420-3-1-.51

Filed July 20, 1988. Repealed and New Rule: Filed December 16, 1999; effective January 20, 2000. Repealed and New Rule: October 20, 2005; effective November 24, 2005; operative March 19, 2006. Amended: Filed October 19, 2006; effective November 23, 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 .95 was renumbered .51 per certification published December 30, 2022; effective February 13, 2023.

Authors: Thad Pitman, Lem Burell, Matthew Conner, Ken Stephens, Bob Bright, David Gray, Boyd Rogers, Richard Smith

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