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

• 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:

• 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

• 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• 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

• 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

• Progressive Sizing

• Enhanced Infiltration

• Rapid Vegetation Establishment

• Adaptive Maintenance

Progressive Sizing of Sediment Control BMPs

Progressive Sizing—sediment control BMPs

Discharge

Watershed

Boundary

Ditch/Drainage Bottom

76

543

2

1

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.

Progressive Sizing—sediment control BMPs

Discharge

Watershed

Boundary

Ditch/Drainage Bottom

BMP Number 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

76

543

2

1

Progressive Sizing—sediment control BMPs

Discharge

Watershed

Boundary

Ditch/Drainage Bottom

76

543

2

1

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.

Enhanced Infiltration

• Avoid compaction

• Maximize surface roughening

• Beware of fine textured soils

• Consider temporary seeding

Rapid Vegetation Establishment (the case for temporary seeding)

Rapid & Robust

Sparse

Slow & Stunted

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/Sto

rmwaterConstruction.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/

env/erosion.shtml

Discussion

Contact Information

Stuart Jennings

Reclamation Research Group, LLC

(406)624-6616

sjennings@reclamationresearch.net