Temporary flow control and conveyance measures

Temporary Pipe Slope Drains

Flexible tubing or conduit extending temporarily from the top to the bottom of a cut or fill slope.

To convey concentrated runoff down the face of a cut or fill slope to a protected stable area without causing erosion.

Used on side before permanent storm water drainage structures are installed where storm water runoff above a cut or fill slope will cause severe erosion if allowed to flow over the slope.

Must be sized, installed, and maintained properly because failure results in slope gully erosion. The entrance must be securely entrenched with watertight connections, with securely staked conduit.

Should handle peak runoff form the 10-year storm. The maximum drainage area per pipe is 10 acres. The entrance should be constructed of standard fared end section of pipe or equivalent. Reinforced hold-down garments should be spaced at 10 ft. or less intervals.

Runoff Control Measures

A temporary ridge, excavated channel, or combination ridge and channel constructed across sloping land at a pre-determined grade.

To divert clean water around work sites to stable outlets and to divert sediment-laden water to sediment control structures such as sediment traps and basins.

• Above slopes to prevent clean runoff from flowing over unprotected soil
• Across unprotected slopes to reduce flow lengths
• Below slopes to divert runoff to a stable outlet
• Within and below disturbed areas to divert sediment-laden water to control structures.

Design as a stable channel with a mild bed slope. Use of either uniform or a gradually increasing grade is preferred over sudden decreases or increases in grade. A permanent vegetative covering is required where the channel grade is between 2% and 3%.

Design drainage area is 5 acres or less based on the peak runoff from the 10-year storm. A channel lining is required if the average velocity is greater than 2 ft./sec. Channel side slopes are 2:1 or flatter. The berm must have side slopes of 2:1 or flatter with a minimum top width of 2 ft. and a designed freeboard of at least 4 inches.