SPECIAL PROVISIONS *
DETOUR – CONSTRUCT, MAINTAIN AND REMOVE (CWGS 05-21-07)
A. Description. Describe detour to be constructed. Design for a posted speed of 35
MPH unless approved otherwise by the Project Manager.
B. Construction sequence - when the detour is to be constructed.
C. Drainage. Coordinate with MDT’s District Biologist early in the detour design
process to determine which treatment should be used and to address other environmental
concerns associated with the detour. Culverts should be hydraulically designed to a ten year
design storm event, and where appropriate, fish passage. Prior to installing the detour culvert
place drain aggregate meeting Section 701.10 in the channel bottom extending 0.5 meter
beyond each side of the active channel to an average depth of 150 mm for the entire length of
the culvert. This treatment is typically used in perennial streams or any streams with cold-water
fisheries. Place Class I erosion control geotextile on the upstream and downstream face of the
detour embankment. Keep grades as low as possible. Key the geotextile into the toe of the fill
and the top of the fill and extend at least 1 meter beyond the defined channel banks. Note that
the defined channel banks may not be the same as the active channel.
D. How is the detour to be constructed?
1) To the lines and grades shown on the plans.
2) As designated by the Project Manager.
3) Surfacing - Type, depth and width. Show two typical sections on the plans.
Pave all detours anticipated to last seven days or more with a Grade D Commercial plant mix.
Finish through base course or place traffic gravel with aggregate treatment on all traveled
surfaces that aren't paved. Maintain all surfaces in a smooth and safe condition.
4) Quantities shown on plans. Include quantities of drain aggregate and geotextile
in the detour quantities summary if applicable.
5) Plan and profile of the detour included in the plans. If possible locate the
overtopping point (low point) a minimum of 25 meters from the culvert.
6) A profile detail of the culvert installation including elevations if applicable.
7) Cross section(s) showing the culvert invert elevations, the location of the
geotextile placed on the embankment faces, and the location and extent of either the drain
aggregate or the geotextile placed in the stream channel.
E. Obliteration of detour.
1) By whom.
3) Disposition of material in detour.
F. Measurement and Payment.
1) Quantities paid for separately at their respective unit bid price.
G. The following paragraph should be included when appropriate:
1) Detour signing will be measured and paid for in accordance with Section 618 of
the Standard Specifications and the "Traffic Control Rate Schedule" found elsewhere in this bid