Illinois Administrative Code › Title 77 - PUBLIC HEALTH › Part 905 - PRIVATE SEWAGE DISPOSAL CODE › Section 905.95 - Illinois Raised Filter Beds

Current through Register Vol. 48, No. 28, July 12, 2024
a)
			 Illinois raised filter bed disposal systems shall have a filter loading rate of
			 4 gallons per square foot per day for residential systems of up to 1,500 GPD
			 flows. Non-residential systems of any size or residential systems in excess of
			 1,500 GPD shall use a filter loading rate of 2.5 gallons per square foot per
			 day. The system shall be designed in accordance with Appendix A, Illustration
			 X, Exhibits A through E.
b) An
			 aeration batch treatment system that has been approved by NSF in accordance
			 with NSF Standard 40 shall be used. The aeration tank volume shall hold at
			 least 2 times the average daily wastewater flow for residential use (including
			 the use of a garbage disposal). Non-residential systems shall have a tank
			 volume size of 3 times the daily wastewater flow. Multiple tanks shall be used
			 to achieve the volume required. Multiple tanks require connection at the bottom
			 of each tank for flow equalization.
c) Filter beds shall not exceed 600 square
			 feet. If a larger area is needed, multiple beds shall be used, separated by a
			 minimum distance of 15 feet, using a common mantle. The filter beds can be
			 placed at any point on the mantle to accommodate existing ground
			 contours.
d) The filter length
			 shall not exceed 3 times the width.
e) The sand filter media shall have an
			 effective size of 0.5 to 2.0 millimeters, a uniformity coefficient of less than
			 3.5, and a 30-inch depth.
f) The
			 mantle shall be sized in accordance with the formula A = QT/25, where A =
			 Mantle Area, Q = Quantity of wastewater per day, and T = Percolation time of
			 the original soil in minutes per inch. (See Appendix A, Illustration X, Exhibit
			 E to convert soil investigation information to T (percolation time).)
g) The mantle shall be at least equal to the
			 area of the filter bed. The mantle shall not be designed for percolation rates
			 that exceed 120 minutes per inch.
h) The mantle area is to be cut into original
			 soil to a depth of 6 inches and back-filled with 12 inches of torpedo sand that
			 is graded as FA1-FA8 in accordance with Standard Specifications for Road and
			 Bridge Construction (Illinois Department of Transportation).
i) The slope of the bottom of the mantle
			 shall be level, plus or minus one inch. The slope of the earth sidewalls of the
			 filter shall be a maximum of 3 feet horizontal to one foot vertical.
j) The mantle area shall be at least 12
			 inches deep. If the maximum high groundwater table is less than 6 inches from
			 the bottom of the filter bed, additional torpedo sand shall be used to increase
			 the isolation distance between the bottom of the filter bed and the high
			 groundwater table to at least 6 inches. Other separation distances (e.g., well,
			 property line) shall be measured from the toe of the filter bed.
k) The distribution piping (4-inch perforated
			 pipe) shall be placed level to 15-inch centers in 12 inches of 3/4-inch
			 stone.
l) Sod shall be placed over
			 the filter beds and mantle.