Offi ce of SustainabilityPresented by Sofia Habity

EROSION AND SEDIMENTATION CONTROL

Goals• Difference between sedimentation and erosion controls.• Introductory techniques for site evaluation.• Introduction to ESC best management practice.

Why ESC?• Due diligence• LEED Sustainable Sites Prerequisite • EMS, ISO 14001 requirement• Client compliance program• Site Management & Public Safety• Regulatory Requirement

The fisheries Act – • Subsection 36(3) prohibits the deposition of a deleterious substance of any time into water frequented by fish or in any place where the deleterious substance may enter any such water

• Sediments are considered deleterious substances

Objectives of the ESC Plan• Prevent erosion and manage sediments.• Tailor the ESC measures to site conditions.• Address varying field conditions.• Clearly show the location and type of necessary BMPs.• Provide a stable, well vegetated site.• Protect critical areas.

Key Concepts• Erosion: Movement of soil particles from their place of origin by the action of wind, water or ice, and by the force of gravity.

• Sedimentation: Deposition of soil particles, following processes of weathering and erosion.

Best Management Practice

• Run on controls/diversions• Erosion and sediment control• Site management

Monitoring Water Quality - Turbidity Meter

• Measures light penetration• In general:

<50 ntu: clean water, acceptable for discharge to storm sewer system

>50 ntu: not acceptable for discharge.

>100 ntu: problems on site

>500 ntu: NO Control

Ntu: Nephelometric Turbidity Unit

Monitoring Water Quality• Red river (middle) ~ 300 ntu

Erosion – hierarchy of soil erodibility

Low plasticity silt (more moist-less stable) Silt Sand

Clayey sand

Clay

Silty gravel

Poorly graded gravel

Well grated gravel (most stable)

Site Evaluation• Soil Loss Equation: RUSLEFAC Revised universal soil loss equation for application

in Canada

Equation looks at different factors that effect erosion: which can we control?

Amount of soil loss: LS*K*R*C*P L: length (We can)

S: steepness of slope (We can)

K: soil erodibility

R: rainfall

C: Cover factor (We can)

P: practice factor (We can)

In Canada double the K in spring

ESC plan elements1 - Minimize clearing and grading

2- Protect waterways

3 - Phase construction to limit soil exposure

4 - Immediately stabilize exposed soils

5 - Protect steep slopes and cuts

6 - Employs advanced sediment settling control

7 - Train contractors on erosion control plan implementation

8 - Control construction waste

9 - Install perimeter controls to filter sediment

10 - Inspect and maintain Best Management Practices

Strategies – Erosion Control BMPsEx:• Rain gardens• Top soil stockpile• Temporarily gravel

Techniques- “Controlling the ‘C’ factor”:• Soil preparation• Slope Treatments• Small seeders• Mulch (part of re-vegetation strategy)

Loose straw

Hydro-seeding - no shear strength, flat/rocky ground. Perfect for >= 3H:1V slopes

Blankets- 100% coverage, slopes up to 1:1, smooth ground

Rip Rap (more costly)

Erosion on Campus• Solution: Hydro seeding

• Erosion Control Blankets: stabilize and protect soil from raindrop impact, increase & crusting, and conserve soil moisture:

ECBs consist of bio-degradable or photodegradable netting enclosing straw, wood fiber or coconut fiber.

• Hydro-seeding: application of moisture of wood fiber (containing glue), seed, fertilizer. To protect exposed soils from erosion by water and wind.

Typical Soil Stabilization - ECB• Good soil contact.

• Apply permanent seeding before placing blankets.

• Lay blankets loosely and staple to maintain direct contact with the soil.

Transport Control BMPs• Buffer Strips• Silt Fences• Check Dams/Dikes• Fibre Rolls • Sandbag Barriers

Strategies – Sedimentation Control• Trapping systems• Settling systems

Ex:• Silt fences (ineffective, requires anchoring) – next slide• Fiber roll logs• Ditch checks: divert runoff to a desired location (around the

construction site)• Silt curtains• Sedimentation ponds• Filter system• Water trucks• Jersey barriers• Hay bales checks• Swamp mats

More Visual ExamplesSedimentation basin

Problem

Silt fence overload to failure

Access (and Exit) Roads

AIM for success in ESC Plan by:• Applying the correct BMPs based on side conditions.• Installing and inspecting the BMPs properly•Maintaining and repairing the BMPs as necessary to maintain effectiveness

Responsible ESC Plan• Respect that erosion control is more cost effective than sedimentation control• Employ multiple measure of sedimentation and erosion control• Make personnel responsible•Many plans focus on re-vegetation strategies in N.A. May not be best approach ‘things don’t grow there very quickly’

What are you protecting?• Failure of riprap protection. Even riprap requires maintenance. Water

washed rocks away and exposed geotextiles

Thank you