Construction Site Erosion and Sediment Controls

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Construction Site Erosion and Sediment Controls
Section 4. Temporary Control Measures
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Temporary Control Measures
Temporary control measures are employed during
construction to control erosion and sediment
until permanent protection can be provided
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Erosion and Sediment Control

1. Divert water so it does not flow across disturbed
   areas
2. Establish temporary cover on disturbed areas
3. Implement downslope controls to minimize the
   quantity of sediment that leaves the site
4. Practice good housekeeping

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Temporary Control Measures

• Temporary control measures can be divided into
  three general categories
• Runoff control
• Erosion control
• Sediment control

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Temporary Control Measures

• Runoff control protects exposed soil by diverting
  runoff away from exposed soil
• Erosion control protects the soil and limits the
  amount and rate of erosion on disturbed areas
• Sediment control traps soil particles after they
  have been detached and prevents them from leaving
  the site

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Temporary Runoff Control
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Temporary Runoff Control
Temporary runoff controls are implemented to
prevent formation of rills and gullies of the
exposed soils onsite by controlling offsite
sheet-flow and concentrated flow
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Temporary Runoff Control BMPs

• Diversion ditches and berms
• Slope drains
• Ditch checks and other grade control measures

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Diversion Ditches
A diversion ditch is a temporary berm and channel
combination used to divert water flow
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Diversion ditches intercept runoff and direct it
to a desirable collection or discharge point
Seed and mulch is generally needed for ditches
with slopes less than 5
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Diversion ditches should be installed at the top
of slopes
Riprap can be used to stabilize ditches with
slopes greater than 8
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Diversion ditches can also be installed below
slopes to divert excess runoff to stabilized
outlets
Seed or erosion control matting can be used to
further stabilize ditches with slopes between 5
and 8
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Temporary Slope Drains
A slope drain is a device that conveys surface
water down a slope
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Slope Drains
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Slope Drains
Slope drains may be constructed of various
materials
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Slope Drains
Berms or dikes should direct less than 8 acres of
drainage to slope drains
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Slope Drains
Temporary pipe slope drains
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Slope Drains
Outlet to stone check dams to dissipate energy
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Ditch Checks

• Ditch checks are temporary barriers placed across
  channels
• Ditch checks are usually constructed of rock,
  sandbags, gravel bags, or baled straw

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Rock Ditch Checks
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Rock Ditch Checks
Stone check dams work well to slow flow velocities
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Rock Ditch Checks
Rock has to meet requirements of Section 207
(stone backfill)
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Rock Ditch Checks
Space ditch checks so that the toe of the
upstream check is no higher than the top of the
downstream check
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Sand/Gravel Bag Ditch Checks
Place one line of bags on back (overflow area) of
ditch check to prevent undermining
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Sand/Gravel Bag Ditch Checks
Sandbag ditch checks are adequate for smaller
swales with lower flow rates
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Baled Straw Ditch Checks
Baled straw ditch checks shall only be used in
conjunction with sediment basins, diversion
ditches, other ditch checks, or other site
specific locations
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Baled Straw Ditch Checks
Baled straw ditch check used in a grassed lined
swale
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Baled Straw Ditch Checks
Baled straw ditch checks used in series
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Baled Straw Ditch Checks
Baled straw ditch check in series with a rock
ditch check
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Temporary Erosion Control
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Erosion Control

• Erosion control should be the first line of
  defense against off-site impacts
• Erosion control practices are generally more
  effective and preferred over sediment control
  practices
• Objective is soil stabilization

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Stabilized Soil

• Stabilized soil is defined by the Specifications
  (Section 110.06(d)) as being soil that is
• Covered by grass
• Seeded and mulched
• Mulched
• Covered by erosion control matting
• Covered by permanent stabilization

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Temporary Erosion Control BMPs

• Surface roughening
• Ground cover
• Rolled erosion control products (RECP)

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Surface Roughening

• Surface roughening is a temporary erosion control
  measure to protect disturbed areas and prepare
  areas for seeding
• Roughening creates depressions on the soil
  surface by mechanical means stores rainwater,
  slows runoff, and enhances seed germination

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Surface Roughening

• Roughening is performed parallel to slope
  contours, or perpendicular to runoff direction
• Surface roughening techniques include
• Sheepsfoot rolling
• Track walking
• Scarifying
• Stair stepping
• Imprinting

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Track Walking
Grooves formed during track walking shall be
perpendicular to the flow of water down the slope
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Track Walking
Track walking enhances germination
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Imprinting
An imprinter creates soil texture
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Ground Cover

• Ground cover is vegetation, mulch, or a
  combination of both used to protect the soil from
  the erosive force of water
• Disturbed areas must be stabilized within 14
  calendar days after activity ceases unless work
  is to be performed within 21 calendar days after
  activity ceases

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Temporary Vegetation
Applications must conform to Sections 620 and
621 of the Standard Specifications
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Temporary Seeding

• Rye and cereal grasses shall be planted at the
  rate of 110 kg/ha between August 15 and January
  20
• Brown Top Millet or Sudan Grass shall be planted
  at the rate of 55 kg/ha between January 21 and
  August 14
• Fertilizer shall be applied at the rate of 560
  kg/ha of 10-20-10 or the equivalent amount of
  plant food
• The Engineer may adjust the above limitations

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Straw Mulch
Straw mulch is commonly used for temporary
erosion control
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Mulch
Mulch cover shall be applied at the rate of 4500
kg/ha (4000 lbs/ac)
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Mulch
Mulch shall be spread uniformly over the entire
disturbed area using approved blowing equipment
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Mulch
When approved by the engineer, the Contractor may
use hand methods to apply mulch to small or
inaccessible areas
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Mulch
Immediately following or during the application
of the mulch, the mulch shall be anchored by
crimping or tackifier
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Mulch
Crimpers have teeth that incorporate the straw
into the soil
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Mulch
The anchoring shall be performed so that the
grooves are perpendicular to the flow of water
down slopes
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Mulch
Tackifiers listed on the Departments Qualified
Products List (QPL) shall be applied at
appropriate rates
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Mulch
Mulch armors soil against raindrop impact and
sheet erosion
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Mulch
Mulch protects the soil surface from compaction
and increases infiltration
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Mulch
Mulch moderates the soil temperature and reduces
moisture loss from evaporation
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Mulch
Mulch reduces weed competition for desirable
plants
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Mulch
Mulch should be used in combination with other
BMPs
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Rolled Erosion Control Products

• Erosion control matting allows the establishment
  of vegetative growth in an area of concentrated
  water flow
• Erosion control matting is commonly used on steep
  slopes and in ditches, swales, or channels where
  excessive velocities are expected
• RECP materials shall be furnished according to
  AHTD Class 1, Class 2, and Class 3 (all shall be
  listed in the QPL)

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Rolled Erosion Control Products
The class of matting will be shown on the plans
and/or specs
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Rolled Erosion Control Products
The type of matting used within a particular
Class shall be at the option of the Contractor,
unless otherwise specified
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The matting shall be applied to the area after
the area has been shaped, fertilized, and seeded
as specified
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RECP Installation
The matting shall be installed according to the
manufacturers recommendations
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Questions? 10-Minute Break