Transcript Stormwater CD Development - Montana Society Of Engineers

Stormwater Control Requirements for
Construction Sites in Montana
Stuart Jennings
Reclamation Research Group, LLC
Erosion
• Accelerated Erosion occurs at construction sites
when stabilizing vegetation is removed
Stormwater Basics
What is stormwater?
• What is the Clean Water Act?
• What is the National Pollution
Discharge Elimination
System?
• What permit is required for a
construction site?
• Which BMPs are appropriate
to my site?
Families of BMPs
• Surface Stabilization BMPs—hydromulch, straw
mulch, erosion control blankets, temporary
seeding, slope roughening, others
• Sediment Control BMPs—silt fence, check
dams, sediment basins, lined channels, straw
bales, others
• Non-storm water BMPs—Equipment decon
areas, stockpile management, tracking control,
stabilized site entrances, others
Examples of BMPs—straw
mulch
Examples of BMPs—rock check
dams
Examples of BMPs—erosion control fabric
Montana Law and Storm
Water Permitting
Montana Code Annotated (MCA) 2001
• TITLE 75. ENVIRONMENTAL PROTECTION
CHAPTER 5. WATER QUALITY
• (29) (a) "State waters" means a body of water, irrigation
system, or drainage system, either surface or
underground.
(b) The term does not apply to:
(i) ponds or lagoons used solely for treating,
transporting, or impounding pollutants; or
(ii) irrigation waters or land application disposal
waters when the waters are used up within the irrigation
or land application disposal system and the waters are
not returned to state waters.
Montana Code Annotated (continued)
• 75-5-101. Policy. It is the public policy of this state to:
(1) conserve water by protecting, maintaining, and
improving the quality and potability of water for public
water supplies, wildlife, fish and aquatic life, agriculture,
industry, recreation, and other beneficial uses;
(2) provide a comprehensive program for the
prevention, abatement, and control of water pollution.
Montana Code Annotated (continued)
25) (a) "Pollution" means:
(i) contamination or other alteration of the physical,
chemical, or biological properties of state waters that
exceeds that permitted by Montana water quality
standards, including but not limited to standards relating to
change in temperature, taste, color, turbidity, or odor; or
(ii) the discharge, seepage, drainage, infiltration, or
flow of liquid, gaseous, solid, radioactive, or other
substance into state water that will or is likely to create
a nuisance or render the waters harmful, detrimental,
or injurious to public health, recreation, safety, or
welfare, to livestock, or to wild animals, birds, fish, or
other wildlife.
(b) A discharge, seepage, drainage, infiltration, or flow
that is authorized under the pollution discharge permit
rules of the board is not pollution under this chapter.
Pollution Authorization
Storm Water Permitting
Authority
• Tribal Lands
(EPA)
• All other lands within the State of Montana
(Montana Department of Environmental
Quality)
General Permit for Storm Water
Discharge associated with construction
Activity (obtained from DEQ)
• Part I. Coverage provided by General Permit
• Part II. Effluent Limitations and Special
Conditions
• Part III. Monitoring, Reporting, Record Keeping
• Part IV. Storm Water Pollution Prevention Plan
(SWPPP)
• Part V. Standard Conditions
General Permit Summary
• Identify areas that may contribute
pollutants to surface waters
• Ensure that minimal sediment reaches
surface water using erosion and sediment
control measures
• Develop and implement a Storm Water
Pollution Prevention Plan (SWPPP)
General Permit Part I.
Coverage provided
• Construction disturbances >1 acre require
permitting
• All discharges must be in accordance with
the SWPPP
• Notice of Intent (NOI) Package must be
submitted to DEQ
• NOI Package contains standard NOI form,
SWPPP and application fee
NOI Form
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Name and address of operator(s)
Contact person telephone number
Project name and location
Name of receiving surface water
Construction schedule
Estimated area of disturbance
General Permit Part II. Effluent
Limitations and Special Conditions
• All discharges to surface water must be
composed entirely of stormwater
• No discharge of process wastewater
• Stormwater discharges must not cause or
contribute to water quality standard
violations
• BMPs must be maintained in accordance
with SWPPP
General Permit Part III. Monitoring,
Reporting, Record Keeping
• All erosion and sediment control measures must
be inspected and maintained by the operator at
least once every 14 days and within 24 hours of
any storm event of 0.5 inches or greater
• DEQ must be notified in writing within 2 days of
the detection of any significant spill or release
• Copy of SWPPP must be available on-site
• Uncontrolled releases must be documented
“significant sediment”
• Mud, dirt, sediment, or similar material
exceeding 1.0 cubic foot in volume which
is deposited in any area of 100 square feet
or less on public or private streets or
property adjacent to the construction site.
General Permit Part IV. Storm Water
Pollution Prevention Plan (SWPPP)
• Operator shall develop a SWPPP and
submit a copy at the same time as the NOI
form
• Operator shall implement the SWPPP at
the time construction activity commences
• Operator is responsible for for ensuring
SWPPP requirements stated in the
General Permit are complied with
SWPPP (continued)
• The SWPPP may include any erosion and
sediment control measures or BMPs
including but not limited to the use of
sediment basins, berms, barriers, filter
strips, covers, diversion structures,
seeding, and sodding
The SWPPP must include
maps(s) indicating:
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Areas of disturbance
Drainage patterns
Location of BMPs
Revegetation areas
Location of Impervious structures
Location of all surface waters
Location of 100 year floodplain
SWPPP (cont.)
• Must include BMP description
• Must preserve existing vegetation
• None of temporary BMPs shall be
removed until permanent vegetation and
site stabilization has taken place
• BMPs must minimize or prevent
“significant sediment” from leaving the
construction site
Notice of Termination (NOT) Form
• Where a site has been finally stabilized the
operator of a site shall submit a Notice of
Termination to DEQ
• “final stabilization” means all soil disturbing
activities have been completed and a
vegetative cover has been established
with a density of at least 70 percent of the
pre-disturbance levels
Storm Water Compliance
• DEQ expects all permit holders to be in
compliance with the provisions of the
General Permit and the site specific
SWPPP
• DEQ will conduct inspections
• DEQ will issue fines for non-compliance
Fines for non-compliance
• 75-5-631. Civil penalties (1) In an action
initiated by the department to collect civil
penalties against a person who is found to
have violated this chapter or a rule, permit,
effluent standard, or order issued under
the provisions of this chapter, the person is
subject to a civil penalty not to exceed
$25,000. Each day of violation constitutes
a separate violation.
Developing a site specific strategy
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Soil type
Slope steepness
Potential rainfall
Adjacent water resources
Seasonality of work
Construction sequencing
BMP selection, installation, monitoring,
maintenance
• Emphasis on surface stabilization or sediment
control BMPs, or both
Erosion Prediction using the Universal
Soil Loss Equation
A=RKLSCP
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A = Average Annual Soil Loss
R = Rainfall Amount
K = Soil Erodibility
L = Slope Length
S = Slope steepness
C = Cover Factor
P = Conservation Practices
Rainfall Factor (R)
• Rainfall intensity and duration
• Built in database for rainfall intensity
• As rainfall intensity increases, erosion
increases
• As rainfall duration increases, erosion
increases
NRCS TR-55 Storm Types
Soil Erodibility Factor (K)
• Relates to soil texture
and rock content
• Silty soils are typically
most erodible
• Sandy soils have
better infiltration,
larger particles
• Clay soil have better
cohesion
Slope Factors
• L = Length of Flow Path
• Longer flow paths have more erosive
power
• S = Slope steepness
• Steep slopes have higher runoff
velocities
Cover Management Factor (C)
• Erosion rate directly proportional to the
amount of vegetation cover protecting the
soil surface
• Vegetation reduces rainfall impact energy
• Vegetation promotes infiltration
• Vegetation reduces runoff velocity
• Vegetation traps sediment
• Have control over this factor
Conservation Practices Factor (P)
• Manipulation of the
soil surface to
discourage erosion
• Provides slope
storage
• Surface roughening
• Pitting
• Implemented on the
contour
Example 1, Consider a 1 acre
area
• In an area that receives 12 in of annual
precipitation, 1 acre-ft of water is applied to the
soil surface
• 1 acre-ft = 325,000 gal
• 1 in rainstorm = 27,000 gal water
• 27,000 gal water = 112 tons
• 112 lbs sediment @ 500 mg/l TSS
• Likely several tons of bedload transported
sediment
Example 2, consider 1 acre of
bare soil
• Apply 1 in of rain over a 1-hour period
• Sandy loam texture
 90% infiltration, 3,000 gal runoff
• Silt loam texture
 40% infiltration, 16,000 gal runoff
• Clay loam texture
 20% infiltration, 22,000 gal runoff
Observations from construction
sites in MT, WY, ID
• http://stormwater.montana.edu/
• CD
Compost Application using Blower Truck
Several hundred feet of hose
can be attached to the blower
truck to allow for distant
installation of compost blankets
on steep slopes
Compost Blanket
Revegetation Results using Compost on steep highway cut slopes
Glacial silt parent material
Alluvial rock parent material
Beartooth Highway
Stabilization
The Problem
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Unstable slopes
Debris on the roadway surface
Undermined roadway/destabilized fill
Denuded soil prone to erosion
Monitoring in response to
precipitation or snow melt
Changing Site Hydrology/Seasonal Changes
in Climate
Some BMPs requires removal
Major Types of Surface Stabilization
BMPs--Regrading
Major Types of Surface Stabilization
BMPs—Soil Replacement or substitution
Major Types of Surface Stabilization
BMPs—Seedbed preparation and seeding
Contour Tillage
Major Types of Surface Stabilization
BMPs—Surface Protection
Major Types of Surface Stabilization
BMPs—Streambank stabilization
Note sediment in
culvert
Nick Point without
appropriate anchoring
Optimized Designs for Enhanced
Stormwater Control
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Progressive Sizing
Enhanced Infiltration
Rapid Vegetation Establishment
Adaptive Maintenance
Progressive Sizing of Sediment
Control BMPs
Progressive Sizing—sediment control BMPs
In this 1 acre hypothetical watershed
100% of the area has been disturbed.
A 1 inch rainfall occurs and 50% of the
rainfall infiltrates into the soil. How
much stormwater runs through each
BMP? Assume that the spacing
between BMPs is constant.
Ditch/Drainage
Bottom
1
2
3
4
5
6
7
Watershed
Boundary
Discharge
Progressive Sizing—sediment control BMPs
BMP Number
Ditch/Drainage
Bottom
1
Subwatershed
Size (acres)
Volume of Water
Generated
(Gallons)
1
0.05 (pink line)
679
2
0.1 (maroon line)
1358
3
0.2 (olive line)
2716
4
0.3
4073
5
0.5
6789
6
0.8
10862
7
1.0
13578
2
3
4
5
6
7
Watershed
Boundary
Discharge
Progressive Sizing—sediment control BMPs
13578 gallons of water exiting the site
containing 500 mg/L of TSS would carry 56
pounds of suspended sediment. The
amount of bedload sediment (not
suspended) left in the BMPs would likely be
several tons.
Ditch/Drainage
Bottom
1
2
3
4
5
6
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Watershed
Boundary
Discharge
Enhanced Infiltration
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Avoid compaction
Maximize surface roughening
Beware of fine textured soils
Consider temporary seeding
Rapid Vegetation Establishment
(the case for temporary seeding)
Slow &
Stunted
Rapid &
Robust
Sparse
The Revegetation Dilemma
• Vegetation is the glue that holds the soil in
place
• Most construction sites use seeded
vegetation and not sod
• Most construction sites are not irrigated
• Vegetation grows slowly
• Stabilization commonly takes 2 years in
Montana
Rapid Revegetation (cont.)
• What we want for stormwater control is
rapid vegetation growth to control
stormwater
• What we commonly get is slow vegetation
growth and accentuated erosion from
typical time of seeding in late fall until mid
summer when a small plant may grow
from the seed planted
Rapid Revegetation (cont.)
• We typically seed perennial native grasses
• The seeding window for perennial native
grasses occurs twice a year—early spring and
late fall.
• An opportunity exists to use a temporary
seeding with an annual grass
• Annual plants grow quickly, can be planted
anytime the soil is warm and damp.
• Annual plants are a good soil stabilizer and the
seed is inexpensive
Wheat versus Western wheatgrass
Western Wheatgrass
(perennial plant)
Wheat (annual plant)
Adaptive Maintenance
Maintenance of Accumulated Sediment
Maintenance of Nick Points
Multiple BMP Iterations
Resources
• Montana DEQ Stormwater Program
• http://www.deq.mt.gov/wqinfo/MPDES/Stor
mwaterConstruction.asp
• U.S. Environmental Protection Agency
• http://cfpub.epa.gov/npdes/stormwater/con
st.cfm
• Montana Dept. of Transportation
• http://www.mdt.mt.gov/research/projects/e
nv/erosion.shtml
Discussion
Contact Information
Stuart Jennings
Reclamation Research Group, LLC
(406)624-6616
[email protected]