§ 73.55. Elevated sand mounds.
(1) The maximum slope of the undisturbed soil, to the extremities of the berm, of a proposed absorption area where elevated sand mound trenches may be permitted is 12%.
(2) The maximum slope of the undisturbed soil, to the extremities of the berm, of a proposed absorption area where an elevated sand mound bed may be permitted is 12%.
(3) The limiting zone is the base elevation for measuring the required depth of sand to achieve a minimum of 4 feet of satisfactory material between the bottom of the aggregate and the top of the limiting zone.
(4) A minimum of 1 foot of sand shall be placed under the aggregate in all elevated sand mound systems.
(5) Existing mineral soil shall be utilized. No mineral soil in the area of the elevated sand mound may be removed or disturbed for the purpose of adding or mixing fill material.
(6) Elevated sand mound trenches shall meet the requirements of § 73.52(b) (relating to standard trenches) and this section.
(7) Elevated sand mound beds on slopes up to 8% shall meet the requirements of § 73.53 (relating to seepage beds) and subsection (b). Other sand mound beds shall comply with subsection (d).
(1) Vegetation shall be cut close to the ground throughout the area to be utilized for the absorption area and berm. Bushes and trees shall be cut flush with the ground surface; roots shall be left in place. Cut vegetation or organic litter shall be raked and removed from the absorption and berm areas.
(2) The proposed absorption area not obstructed by stumps or other obstacles shall be roughed or plowed parallel with the contour to a maximum depth of 6 inches, using a multiple share chisel plow or similar implement attached to light-weight equipment. Rotary tilling is prohibited.
(3) Under no circumstances may equipment travel on the plowed soil surface until the sand is in place.
(4) Immediately after plowing, sand shall be placed over the exposed plowed surface. Sand shall be placed from the upslope side of the bed using only lightweight equipment.
(5) The slope of the sand not directly beneath the aggregate area shall be approximately 50%.
(6) The top of the sand directly beneath the aggregate shall be level to a tolerance of ±2 inches per 100 feet.
(7) The mound shall be surrounded by a berm consisting of mineral soil containing less than 20% coarse fragments with no coarse fragments greater than 4 inches in diameter, more stable and less permeable than the sand, and lightly compacted during construction to contain and protect the mound interior. The width of this berm shall be a minimum of 3 feet at the top of the aggregate.
(8) Upon completion, the outside slope of the berm may be no greater than 50% and shall be seeded to assure the stability of the berm. The cover over the aggregate shall be a minimum of 1 foot of soil suitable for the growth of vegetation.
(9) No equipment may be permitted on the downslope side of the mound with the exception of lightweight equipment that is used to form the downslope berm. To the greatest extent possible, aggregate and the cover material shall be placed from the upslope side of the mound.
(10) When a mound system with trenches is used, the area between the individual trenches shall be filled with mineral soil. A minimum distance of 5 feet shall separate sand of individual trenches. This measurement shall be from the toe of the sand.
(11) The area surrounding the mound shall be grated to provide for diversion of surface runoff waters.
(c) Sand. Sand suppliers shall provide certification in writing to the sewage enforcement officer and permittee, with the first delivery to the job site from every sand source listing the amount of sand delivered, and that all sand supplied meets the requirements posted in the Department of Transportation specifications Publication #408, section 703. The size and grading shall meet bituminous concrete sand Type B #1 or #3 requirements from a Department of Transportation certified stockpile. The sieve analysis shall be conducted in accordance with PTM #616 and #100.
(d) Elevated sand mound beds. Elevated sand mound beds on slopes greater than 8% shall meet the requirements of § 73.53 and subsection (b). In addition, the following apply:
(1) The absorption area shall have a minimum length to width radio of 4 to 1.
(2) The long axis of the absorption area shall be perpendicular to the slope. The bed construction shall follow the ground surface contours.
(3) Upon completion, the outside slope of the berm may be no greater than 33.3%.
(4) Designing the location of multiple absorption areas so that one absorption area is placed hydraulically upgradient or downgradient from the other may cause the lower absorption area to fail because of excessive hydraulic loading from the upper absorption area. Unless the potential for such an impact is shown to be nonexistent by the applicant through the alternative/experimental system process, this type of absorption area placement is prohibited.
The provisions of this § 73.55 amended under section 9 of the Pennsylvania Sewage Facilities Act (35 P. S. § 750.9); The Clean Streams Law (35 P. S. § § 691.1691.1001); and section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20).
The provisions of this § 73.55 adopted January 21, 1983, effective January 22, 1983, 13 Pa.B. 508; amended November 7, 1997, effective November 8, 1997, 27 Pa.B. 5877. Immediately preceding text appears at serial pages (217335) to (217336).
This section cited in 25 Pa. Code § 71.63 (relating to retaining tanks); 25 Pa. Code § 73.44 (relating to pressurized distribution design); 25 Pa. Code § 73.51 (relating to general); 25 Pa. Code § 73.54 (relating to subsurface sand filter beds and trenches); and 25 Pa. Code § 73.162 (relating to intermittent sand filters).
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