Current through Register Vol. 48, No. 9, September 27, 2024
The Department shall be responsible for the evaluation and
approval of alternative infiltration trench products prior to their use in the
state, unless otherwise regulated by statute. This evaluation shall include a
review of available research data; a review of parameters relating to
structure, geometry, and volume; and the establishment of required equivalency
values for comparing the product to a conventional wastewater infiltration
trench.
204.1. Application.
(1) All requests for approval of alternative
infiltration trench products must be submitted in writing to the Department and
must include the following:
(a) Complete
description of the product and its intended use.
(b) Complete listing of materials used in the
construction of the product, including specifications.
(c) Copies of all available literature
pertaining to the product and a listing of all appropriate reference
materials.
(d) Copies of any and
all available research, testing, and monitoring data, to include records of
performance and/or prior experience in actual field conditions.
(2) The Department will review the
application and may seek other information, including additional
evaluations.
204.2.
Equivalency Value for Infiltrative Surface.
(1) The total infiltrative surface area
surrounding the sides and bottom of a conventional wastewater infiltration
trench (i.e., 5.33 sq.ft./lin.ft.) shall serve as the basis for all geometric
comparisons to alternative infiltration trench products.
(2) The effective infiltrative surface area
of a conventional trench shall include the total of both rectangular sidewalls,
beginning at the top of the aggregate and extending to the trench bottom, in
addition to the width of the trench bottom. Similarly, the effective
infiltrative surface area of a product shall include the total of both
immediately adjacent, rectangular sidewalls, beginning at the top of louvers,
slits, holes or similar orifices, in addition to the rectangular width of the
trench immediately beneath the product.
(3) The equivalency value (E) for any given
product is determined by comparing the total effective surface area of the
product, as defined above, with that of a conventional wastewater infiltration
trench as follows:
(a) Total Infiltrative
Surface Area for One (1) Foot of Conventional Trench:
Trench Sidewalls = 2 x (1.16ft.H x 1.0 ft.L) = 2.33
sq.ft./lin.ft.
Trench Bottom = 1 x (3ft.W x 1ft.L) = 3.0 sq.ft./lin.ft.
Total Infiltrative Surface Area = 5.33 sq.ft./lin.ft.
(b) Equivalency Value (E) Shall Be
Computed As Follows:
E = 5.33 sq.ft./ft ÷ Sum of Three Rectangular Interfaces
Immediately Adjacent to Product (sq.ft./ft.)
(c) The Required Total Length of the Product
Shall Be Calculated As Follows:
Length of Product (L) = E x Length of Conventional 36 in. Wide
Trenches Required by DHEC Regulations and Standards
204.3. Other parameters
to be evaluated for alternative infiltration trench products may include the
following:
(1) Structural Integrity - Products
must be of sound construction and able to adequately withstand the normal
pressures and stresses associated with installation and use.
(2) Inertness - No product can be approved
unless it will remain relatively unaffected for extended periods of time while
in contact with typical domestic wastewater.
(3) Storage Volume - The effluent storage
capacity of a product must closely approximate or exceed that of a comparable
conventional system.
(4)
Maintenance of Permeable Interfaces - A product shall have a direct interface
with the effective infiltrative surface (undisturbed natural soil) or, if
backfill is required, backfill material shall not create a permeability barrier
and shall not hinder the downward or horizontal flow of effluent into the
undisturbed natural soil.
(5) The
unique characteristics of a given product may warrant the evaluation of other
parameters not specifically mentioned in this section of the
regulation.
(6) The design,
construction, or installation methods used with any product shall not conflict
nor violate any other requirements established by the Department.
204.4. Approval for General Use.
If warranted, the Department will issue a letter of approval
for general use of the alternative infiltration trench product in accordance
with equivalency values and other requirements determined herein. At least nine
(9) inches of soil cover is required.
