© 2018 HDI

Tina R. Evans, PE, CISECHydroDynamics Incorporated

Parker, CO303-841-0377

© 2018 HDI

ISSUES WITH RUN-ONMain Issues: Quantity of run-on? Where/type? Clean or dirty water? Do you divert it or accept it?

© 2018 HDI

ISSUES WITH RUN-ON Quantity?

Volume of run-on Determined by hydrology

Storm event frequency Where/type?

Location Inflow and outflow

Type Sheet flow Concentrated Urbanized Undeveloped

Designer Responsibility and Obligation

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ISSUES WITH RUN-ON Clean or dirty water?

Pollutant-laden: Sediment Hydrocarbons Etc.

Do you divert it or accept it? Are you obligated to treat it?

Discuss with designers and regulatory agencies

Diversion structures

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Diversion Berm/Channel Conveys flows away/around the

construction site Includes development of berms

and/or channels Requires stabilization of channel

bottom and embankments Requires stabilization at discharge

points

Goal Collect and control the flow of

water Minimize potential of erosion

May require a formal design to convey the flows

Diversion Structures

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Diversion Berm/Channel Slope Drains

Basin Conveys larger quantities of run-on Need containment and control at inlet Need anchoring of the pipe Need controlled and stabilized

discharges

Diversion Structures

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Diversion Berm/Channel Slope Drains

Basin Conveys larger quantities of runoff Need containment and control at inlet Need anchoring of the pipe Need controlled discharges

Roadway Captures road runoff

Entrance way to pipe is important Sandbag barriers Stabilized diversion berm

Diversion Structures

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Diversion Berm/Channel Slope Drains

Basin Conveys larger quantities of runoff Need containment and control at inlet Need anchoring of the pipe Need controlled discharges

Roadway Requires the capture of road runoff Need controlled discharges Need anchoring of the pipe

Requires proper design Pipe diameter Spacing of pipes

Diversion Structures

© 2018 HDI

ISSUES WITH RUN-ON Clean or dirty water? Do you divert it or accept it?

Are you obligated to treat it? Diversion structures Channel stabilization

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Check Structures

Reduces flow velocities Creates a small pond directly

upstream

Requires proper design and installation Low point for discharges

High maintenance

Channel Stabilization

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Spacing is critical between check structures for erosion protection.

Top of the downstream structure must be in line with the bottom of the upstream structure to minimize erosion.

Channel Stabilization

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Steeper the channel slope requires smaller spacing of barriers for erosion control

Channel Stabilization

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Check Structures Rolled Erosion Control

Products (RECPs) Erosion Control Blankets

(ECBs) Temporary Smaller shear stresses

Proper design

Turf Reinforcement Mats (TRMs) Permanent/tong term Higher shear stresses

Proper design

Channel Stabilization

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ISSUES WITH RUN-ON Clean or dirty water? Do you divert it or accept it?

Are you obligated to treat it? Diversion structures Channel stabilization Management

What happens if you cannot divert it?

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MANAGEMENT

What happens when you cannot divert run-on? May have to implement or increase the number of

BMPs specified in the SWPPP to accommodate the increase in flows.

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MANAGEMENT

Downstream sediment control structures May have to increase the number

Sediment traps and basins Increase the number Increase in volume

BMPs may require more frequent maintenance Increase in cost

© 2018 HDI

Summary Is controlling run-on easy?

Requires proper design Requires proper installation and maintenance of BMPs May require additional BMP design and installation Most important is communication and accountability

© 2018 HDI

© 2018 HDI

Tina EvansHydroDynamics, Inc.

303-841-0377