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Sediment

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Ponding allows the sediment to settle out before storm water enters the drain. ... Prevents erosion in small channels, ditches, and swales draining 10 acres or less. ... – PowerPoint PPT presentation

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Title: Sediment


1
Sediment Erosion Control
KEEPING THE SOIL ON THE SITE
Miami County Engineers Office Aug 2004
2
What is Sediment Erosion Control?
The use of various methods to reduce or eliminate
the amount of erosion, and resulting sediment
loss, that can occur on a construction site when
bare soil is exposed to rain and/or snowmelt.
3
Why is Sediment Erosion Control Necessary?
  1. There is a legal requirement to practice sediment
    erosion control on most construction sites.
  2. Proper erosion controls will prevent expensive,
    time-consuming rework of finish-grade landscape
    areas after heavy rains.
  3. Keeping soil on the construction site will
    prevent polluted runoff from entering local
    streams, lakes, and rivers.
  4. The Miami County Commissioners and other local
    political subdivisions are committed to the use
    of effective sediment erosion control methods
    on construction projects undertaken by county,
    township, and municipal agencies.

4
Its the Law
Phase II of the EPA Clean Water Act requires that
soil and sediment from construction sites be
contained on-site, rather than being carried off
the site by rainwater or snowmelt into lakes,
rivers, streams, etc. Non point-source pollution,
such as sediment from construction sites, is
currently the most significant threat to clean
water in the United States.
5
Pay Now, or Pay Later
Sediment and erosion control practices, such as
seeding and mulching, stabilize the soil and
prevent costly and time-consuming site rework.
It makes sense to do it right the first time to
keep from having to come back to do the job over
again.
6
Clean Water is Everyones Business
Storm water runoff and the pollution it carries
can threaten drinking water supplies, harm fish
and wildlife, and ruin recreational opportunities
in lakes and rivers. These negative effects harm
the economy, degrade our natural resources, and
pose a potential health risk. Doing our part to
conserve and preserve clean water resources is a
responsibility each of us shares.
7
Local Initiatives
  • Miami County Commissioners
  • Bethel, Concord, Monroe, Union Townships
  • Miami Conservancy District
  • Miami Soil Water Conservation District
  • Miami County Health Department
  • Miami County Planning Zoning
  • Miami County Engineers Office
  • Local Watershed Groups
  • OSU Extension
  • Ohio Environmental Protection Agency
  • You!

8
On average, how many years does it take to form
one inch of topsoil?
9
The scientific study of soil is called what?
10
Sediment Erosion Control Methods
  • Construction Project Phasing
  • Mulching Seeding
  • Soil Bank Stabilization
  • Silt Fence Installation
  • Inlet Protection
  • Ditch Checks
  • Concrete Washout Procedures
  • Construction Entrance/Exit Road Composition
  • Sediment Basins

11
Sediment Erosion Control First things First
  • Sediment results from Erosion. Therefore, if you
    effectively apply erosion controls as a first
    priority on any project, you will eliminate the
    need to deal with sediment control.

X
X
12
Construction Project Phasing
Completion of a construction project in planned
phases to minimize the amount of disturbed soil
subject to erosion and sediment runoff.
EXAMPLE In a ditch setback improvement
involving 6,000 feet of ditch line, typically the
entire length of ditch line is roughed up at
project onset. This has normally been considered
the most efficient use of manpower and machinery.
After ditch improvements are made over the
course of several weeks, seed/mulch is applied to
the entire area at project completion. This
subjects the entire 6,000 feet of disturbed soil
to the effects of erosion and/or sediment runoff
for the life of the project, however long that
may be.
13
Construction Project Phasing (continued)
ALTERNATIVE Phase the work so only the first
2000 feet of ditch line is disturbed (use some
natural terminus like a culvert, field drive,
etc.). Make improvements and complete that
section of ditch line, up to and including the
application of seed mulch. Then move to the
next phase of the project, and so on, until the
entire project is complete. This approach keeps
the soil vegetated or covered as long as
possible, prolonging protection from erosion and
sediment runoff.
14
Mulching Seeding
EPA regulations require that permanent ground
cover in the form of seed and/or mulch be applied
no later than seven days after reaching final
grade on a project site. If no construction
activity is planned at a site for 21 days or
longer, temporary ground cover must be applied no
later than seven days after soil is first
disturbed. In either of the above cases, if the
disturbed area is within 50 feet of a stream, the
time frame for the application of ground cover is
reduced to two days.
15
Mulching Seeding (continued)
Method Straw Mulch over Grass Seed
ADVANTAGES DISADVANTAGES
Low material expense Low manpower costs Material readily available Easy to apply Straw works well as seed bedding if kept moist Does not hold to sloped soils unless an emulsion tackifier is added. Must be kept moist for seed germination Can be blown off-site by passing cars, wind, or large storm event. Straw waste can contribute to site drainage problems.
Approximate Cost 150 per 5000 sq ft coverage
16
Mulching Seeding (continued)
Method Hydroseeding
ADVANTAGES DISADVANTAGES
Seed, mulch, fertilizer water applied simultaneously Low manpower costs, rapid application Holds well to sloped soils Less affected by wind forces Mulch works well as seed bedding holds moisture longer than straw Can be affected by large storm events Must be kept moist for seed germination Requires water source in order to be applied Success of germination is affected greatly by the manner in which the hydroseed is applied
Approximate Cost 300 per 5000 sq ft coverage
17
Mulching Seeding (continued)
Method Straw/Seed Blankets
ADVANTAGES DISADVANTAGES
Seed, mulch fertilizer applied simultaneously Holds well to sloped soils Least affected by wind forces rain events Blanket works well as seed bedding Labor intensive installation Must spike down blanket with non-biodegradable materials More costly than other mulch/seed applications More subject to on-going service maintenance
Approximate Cost 400 per 5000 sq ft coverage
18
Mulching Seeding (continued)
Method Sod
ADVANTAGES DISADVANTAGES
Immediate erosion/sediment control Holds well to sloped soils Unaffected by wind forces rain events Eliminates need for installation of intermediary sediment and erosion control BMPs Low maintenance and/or rework The most labor intensive installation Must be kept moist to allow sod to bond to soil substrate Will be cost prohibitive for most projects Materials may not be readily available
Approximate Cost 675 per 5000 sq ft coverage
19
Soil scientists have identified more than how
many thousands of soil types in the United States?
20
An annelid is an animal that lives in the soil.
What is its common name?
21
Soil Bank Stabilization
To prevent erosive forces from undercutting
stream banks or other steep contours, rocks or
gabions may be used to stabilize the bank. This
application has the side benefit of preventing
rain droplet impact with underlying soils, which
keeps sediment from leaving the site.
22
Silt Fence Installation
Silt fence is a geotextile screen used to pond
storm water and allow sediment to settle out
before the water migrates to catch basins,
ditches, streams, or lakes. The screen is placed
on the downslope side of a construction site,
along the contour of the project topography, with
enough room behind the silt fence to allow
ponding to occur. At each end of the silt fence,
the fabric must be directed up-slope so water
does not flow around the ends of the material.
23
Silt Fence Installation (continued)
SLOPE SLOPE LENGTH
lt 501 250 FT
501 101 125 FT
101 51 100 FT
51 31 75 FT
31 21 50 FT
gt 21 25 FT
Drainage Area
24
Silt Fence Installation - Summary
  • Silt fence needs to be
  • Installed on the contour
  • Trenched to a depth of 6
  • Stretched until tight
  • All joining sections rolled
  • Stakes on downslope side, from 4 to 6 apart
  • Top of fence 16 above ground
  • Ends of fence elevated

25
Silt Fence - Maintenance
Regular maintenance is needed to assure the silt
fence continues to function properly
  • Inspect installation weekly and after each
    heavy rain
  • Re-anchor where needed
  • Remove accumulated sediment as necessary, to
    restore capacity
  • Repair any tears in the geotextile material

26
Silt Fence Improper Uses
Silt fence should never be placed in flowing
channels, streams or waterways. The fabric
cannot withstand the velocity and volume of water
in concentrated flows and will fail quickly.
27
Silt Fence Rule of Thumb
If it doesnt pond water, it doesnt work.
28
These are primarily responsible for keeping soil
in its place?
29
A handful of soil contains more of these than the
number of people alive on Earth?
30
Inlet Protection
Storm drain inlet protection is designed to
increase the time it takes for sediment-laden
water to enter the storm sewer system, through
the use of short-term ponding. Ponding allows the
sediment to settle out before storm water enters
the drain.
31
Inlet Protection - Types
Various methods can be used to control excess
sediment from entering curb drains and surface
flow inlets. While ponding is the overall
objective, it is not the intent of inlet
protection to totally restrict water from flowing
into the drain. A measured flow can be achieved
through the use of geotextile silt fence
material, manufactured inlet control units, or
utilization of construction materials available
onsite.
32
Inlet Protection - Geotextile
These units use silt fence fabric and wire mesh,
wrapped around a metal or wooden frame, as a
means to pond water around inlets.
33
Inlet Protection Manufactured Units
Some of these units use the weight of the metal
inlet grate to hold them in place. Others merely
snake around the inlet to form a makeshift dam.
Usually they are constructed of florescent
material in order to be seen clearly on the
construction site. As with all Inlet Protection
BMPs, their success depends upon maintenance and
upkeep throughout the construction project and
into the post-construction phase, until
vegetation is established on the site.
34
Inlet Protection Using Construction Materials
Gravel, concrete block, and wire screen can be
used to make an effective inlet protection
device. As always, the objective is temporary,
short-term ponding while allowing filtered water
to pass through.
35
Check Dams
A check dam is a small, temporary barrier
constructed in an open channel, swale, or
drainageway. The dam may be constructed of stone,
logs, brush, straw bales, or any other material
that effectively prevents the flow of water. The
primary purpose of check dams is to reduce the
velocity of concentrated storm water flows in
order to limit erosion. Some settling of
water-borne sediment may also occur behind the
dam.
36
Check Dams - Application
  • Prevents erosion in small channels, ditches,
    and swales draining 10 acres or less.
  • Promotes settling of sediment, but not a
    primary sediment trapping method.
  • Used during the establishment of grass linings
    in drainage ditches or channels.

37
Check Dams - Construction
Dams must be spaced so the toe of the upstream
dam is never any higher than the top of the
downstream dam. Maximum dam height should be 2
feet. The center of the dam must be 10 to 16
inches lower than either edge, to form a weir for
outfall in flood event.
Stabilize dams with riprap where appropriate to
limit washout and erosion around the periphery of
the structure. Use stone 2 to 16 inches in
diameter, logs 6 to 8 inches in diameter,
sandbags filled with pea gravel, or other sturdy,
impervious material to construct the dams.
38
Check Dams - Limitations
Not to be used in live streams. Not appropriate
in channels that drain areas greater than 10
acres. Not to be placed in channels that are
already grass-lined unless erosion is expected,
as installation may damage vegetation.
Require extensive maintenance following high
velocity flows. Must remember to remove the dam
once soil is stabilized with vegetation.
39
Concrete Washout Procedures
A central, controlled area should be established
on the construction site so concrete byproducts
from concrete trucks and other equipment can be
contained and disposed of properly, rather than
being subject to runoff into catch basins or
nearby waterbodies.
40
Stabilized Construction Entrance Road
A primary construction entrance should be
identified for access to and from the
construction site. This entry should be graveled
to prevent sediment and soil from being tracked
onto impervious surfaces by vehicles and heavy
machinery.
41
Construction Entrance Road - Composition
  • Rock size 2 to 3 inches
  • Foundation Geotextile material placed beneath
    rock
  • Thickness 6 inches minimum
  • Placement Rock dumped/spread evenly, compacted
    by roller
  • Width Minimum of 14 ft.
  • Length 70 ft. minimum, 30 ft. for single lot

42
Sediment Basins
Per Ohio EPA, a sediment settling pond must be
established for common drainage locations that
serve an area with 10 or more disturbed
acres. The pond shall be constructed prior to
grading and within 7 days from the start of
grubbing, and must continue to function until the
development is restabilized.
43
Sediment Basins - Sizing
Must be sized to provide at least 67 cubic yards
of storage per acre of total contributing
drainage area. Depth must be five feet or less,
and total pond length must be at least twice the
width. Sediment must be removed from the pond
when capacity has been reduced by 40 (typically,
that point at which sediment occupies one-half of
the basin depth).
44
Air and water make up what percentage of all the
ingredients in soil?
45
In a typical year, how many tons of dry soil per
acre pass through earthworms living in the soil ?
46
Other Sediment Erosion Control Methods
  • DUST CONTROL
  • COVERING SOIL STOCKPILES
  • STREET CLEANING

47
Agricultural Sediment Erosion Control BMPs
For information on these and other agricultural
soil conservation methods, contact your local
Natural Resources Conservation Service district
office.
48
Sediment Erosion Control
KEEPING THE SOIL ON THE SITE
Miami County Engineers Office Aug 2004
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