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
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.
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
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
The Problem • Unstable slopes • Debris on the roadway surface • Undermined roadway/destabilized fill • Denuded soil prone to erosion