HomeMy Public PortalAbout366317Metropolitan
St. Louis Sewer
District
2350 Market Street
St. Louis, MO 63103-2555
(314) 768-6200
August 31, 2010
Mr. David Mudd
Kirchner Block & Brick
12901 St. Charles Rock Road
Bridgeton, Missouri 63044
RE: Peinieable Interlocking Concrete Pavement (PICP) - A Structural BMP
Dear Mr. Mudd,
The Metropolitan St. Louis Sewer District (MSD) has reviewed your application of Permeable
Interlocking Concrete Pavement (PICP). MSD hereby grants Provisional Use Level (PUL)
approval for the PICP with a storage bed. MSD understands that the PICP enhance surface
permeability by the drainage openings created by their interlocking block notched design. In
some applications stormwater water quality objectives can be achieved by infiltration into the
surrounding subgrade soils or filtration via an underground sand filter. In addition, the stone
storage bed underlying the PICP could be designed to provide detention storage such as that
needed to meet channel protection requirements.
MSD has determined that PICP with storage bed systems may be used under the following
conditions:
1. Proposed uses and designs of the device (specifically the Eco-Brick, Aqua-Bric, Aqua-
Bric Type 4, and Turfstone) must be in general conformance with the information and
methodologies provided in the Kirchner application dated August 31, 2007, and strict
guidelines of the Interlocking Concrete Pavement Institute (ICPI) and the requirements
set forth in MSD's PICP General Design and Prequalification policy (latest edition).
2. Channel Protection Volume (CPv) storage may be provided in the base stone and subbase
stone beneath the PICP and bedding layer.
3. The minimum pavement section subject to vehicular traffic shall be (from top to bottom)
3 1/8 inch thick paving units, 2-inch thick bedding stone (typically ASTM No. 8 or 9
stone), 4-inch thick layer of base stone (ASTM No. 57 or similar size), and a layer of
subbase stone (ASTM No. 2 or similar size), all underlain by MSD type 4 filter fabric.
The thickness of the subbase will vary depending on storage and anticipated traffic loads.
However, a minimum 12-inch thick subbase will be required for all applications.
4. The post -developed curve number (CN) may be reduced. Reduced CN numbers are
provided below.
Soil A B C D
CN 61 61 74 80
5. The PICP system will be considered as pervious area for the purpose of calculating Water
Quality Volume (WQv) and 5 percent impervious when calculating the differential runoff
with PI factors. However, the PICP will be considered as 100 percent impervious area for
the purpose of calculating pipe sizes downstream.
6. PICP is not to be used as a standalone WQv treatment Best Management Practice (BMP).
However, PICP may be used to provide WQv treatment when used in conjunction with a
properly designed infiltration basin/trench, sand filter, or other supplemented BMP in
order to meet MSD WQv treatment criteria. Those designs are subject to MSD review
and approval.
7. The application of PICP shall be limited to low volume traffic areas.
8. Project specific design calculations and maintenance plans must be included within the
project's "Stonnwater Management Facilities Report" prepared by the consulting
Engineer.
MSD reserves the ability to withdraw or modify this approval based on subsequent information,
including info' illation indicating that PICP with storage beds do not satisfy MSD rules,
requirements, or construction and material specifications. Please provide MSD with one
representative block sample of each different PICP product that each your supplying
manufacture is producing.
Sincerely,
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Michael T. Buechter, P.E.
Principal Engineer (BMP Committee Chainuian
Engineering/Design
Metropolitan St. Louis Sewer District
" K I R C H N E R
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