Pennsylvania Code › Title 25 - ENVIRONMENTAL PROTECTION › Part I - Department of Environmental Protection › Subpart C - Protection of Natural Resources › Article I - Land Resources › Chapter 73 - STANDARDS FOR ONLOT SEWAGE TREATMENT FACILITIES › CONSTRUCTION OF ABSORPTION AREAS › Section 73.52 - Standard trenches

Current through Register Vol. 54, No. 28, July 13, 2024
(a)
Design.
The maximum slope of the undisturbed soil of a
						proposed absorption area where a trench system may be permitted is 25%. For
						slopes between 15% and 25%, detailed design in relationship to elevation shall
						be provided. The designer shall inspect the installation and verify that, to
						the best of his knowledge and belief, the system was installed in accordance
						with the plans and specifications. Copies of the plans and specifications and
						the designer's report are to be attached to the applicant's copy, sewage
						enforcement officer's copy and the Department's copy of the application for
						sewage permit.
(b)
Construction.
Trenches in an absorption area shall be
						constructed in accordance with the following:
(1) There shall be a minimum of two trenches
						per field.
(2) Trenches shall
						follow approximately the ground surface contours so that variations in trench
						depth shall be minimized.
(3) There
						shall be at least 6 feet of soil between the treatment tank or dosing tank and
						the nearest trench.
(4) The width
						of the bottom of the individual trench shall be 12 to 72 inches.
(5) The depth to the bottom of the absorption
						area shall be 12 to 36 inches.
(6)
						The bottom of the absorption area shall be level to a tolerance of 2 inches per
						100 feet.
(7) The minimum width of
						undisturbed earth between trenches shall be 5 feet. When elevated sand mound
						trenches are used, the distance between trenches shall be measured from the toe
						of the sand of each trench.
(8) The
						minimum depth of aggregate material under laterals shall be 6 inches.
(9) Laterals shall be placed in the center of
						the trench. The first or last discharge hole of a lateral may be no more than 5
						feet nor less than 2 feet from the ends of the trench.
(10) Laterals shall be level to a maximum
						tolerance of 4 inches of fall per 100 feet toward the terminal end of the
						lateral.
(11) The minimum depth of
						aggregate material over the laterals shall be 2 inches.
(12) The depth of aggregate shall be uniform
						throughout the absorption area.
(13) The top of the aggregate material shall
						be covered with geotextile fabric, untreated building paper or a 2-inch layer
						of hay, straw or similar material to prevent backfill material from settling
						into the aggregate.
(14) The
						minimum depth of earth cover over the aggregate in all installations shall be
						12 inches. Where the top of the aggregate is less than 12 inches from the
						undisturbed soil surface, the soil cover shall extend beyond the absorption
						area by at least 3 feet on all sides.
(15) The backfill material shall consist of
						soil suitable for the growth of vegetation, and be seeded to control erosion.
(16) Trench laterals shall be
						fitted with end caps.