FDOT Standard Plans Index 440-001: Underdrain Inspection Box

Design Criteria

Design Criteria and Guidance FDOT Design Manual (FDM) ; Drainage Manual (DM) ; Drainage Design Guide (DDG)

Design Assumptions and Limitations

Design Assumptions and Limitations The type of underdrain should be selected to meet design water removal rate and soil conditions. Caution is prescribed in the use of these typical sections since special designs may be required to satisfy project conditions. Type I underdrain is intended for minimum water removal conditions.

Type II underdrain is intended for moderate water removal conditions. Where reactive conditions may create chemical clogging, the use of an inert material and/or elimination of the geotextile may be necessary. Type III underdrain is intended for maximum water removal conditions.

Geotextile is required between the coarse aggregate or fine aggregate including those described in

General Notes

General Notes 2 and 3. Where reactive conditions may create chemical clogging, the use of an inert material and/or elimination of the geotextile may be necessary. Type V underdrain is intended for use in detention with filtration stormwater management systems and other locations which require a filtration system.

Recovery requirements should be the basis for determining length of underdrain. The designer should evaluate whether an external geotextile envelope is required around underdrain Types I and III. When required, specify the fabric in the plans.

In lieu of the inspection box detailed in Index 440-002 , Manhole Type P Alternate A, Index 425-010, with Type I Frame and Cover, Index 425-001 , may be used and is recommended when high ADT increases the chance of repeated vehicle loadings.

Payment

Payment Item number Item Description Unit Measure Index 440 - 002 Underdrain Inspection Box Index 440 - 02 Underdrain Inspection Box - AA Underdrain LF 440- 70- Underdrain Inspection Box EA 440- 73- A Underdrain Outlet Pipe LF See the BOE and Specification 440 for additional information on payment, pay item use and compensation.

What your plans must show

Plan Content Requirements for this index — the SPI's checklist for designers.

• Plan details for underdrains should include the location of: (a) Type V underdrain, (b) nonstandard locations of Type I, II, and III underdrain, (c) underdrain inspection boxes, (d) cleanouts for Type V underdrain, and (e) underdrain outlet pipes. Flow line elevations at the beginning, bends, junctions, and ends of underdrain pipes and outlet pipes should be specified.