1. Stormwater Management

2. Outline Background Colorado Regulatory Requirements
Stormwater Management Plans (SWMPs)
Best Management Practices (BMPs)
Questions

3. Background
In 1992, the State of Colorado stormwater regulation went into effect to control municipal and industrial stormwater discharges, based on EPA regulations.
The State regulation(5 CCR ) covers discharges from specific types of industries including construction sites, and storm sewer systems for certain municipalities. In Colorado, the program is under the Colorado Department of Public Health &Environment.
The Colorado program is referred to as the Colorado Discharge Permit System (CDPS), and regulated stormwater discharges from construction activities are covered under the CDPS General Permit for Stormwater Discharges Associated with Construction Activities (the Stormwater Construction Permit)

4. Background
June 30, 2005 – The Colorado Water Quality Control Division extends permitting for stormwater discharges from construction activities associated with small construction activity (those that disturb between one and five acres)
Stormwater permitting was previously required for all sites with disturbance in excess of five acres

5. Colorado Regulatory Requirements
Stormwater Discharges are Regulated by the CDPHE Water Quality Control Division
Stormwater permit coverage is required for all construction activities that disturb one acre or greater
Coverage is also required for construction that is part of a larger common plan of development
Oil & gas activities covered include construction of well pads, road, pipelines, pumping stations, etc.

6. Colorado Regulatory Requirements (cont.)
Permit coverage for construction activities is obtained under CDPHE’s Construction General Permit
Application for coverage must be submitted at least 10 days prior to the start of construction
A Stormwater Management Plan (SWMP) has to be prepared at the time the application is submitted
Implementation of SWMP must occur immediately upon initiation of construction

7. Colorado Regulatory Requirements (cont.)
CDPHE Permit Requires Routine Self-Inspections
Active Sites (Disturbed but Not Seeded)
Must be inspected at least once every 14 days and after any precipitation or snowfall event that causes erosion
Completed Sites (Seeded but not Stabilized)
Must be inspected at least once every month
Stabilized Sites (at least 70% vegetation established)
Inspections no longer required
Inspections are not required when snow cover exists over the entire site for an extended period and melting conditions do not exist
Inspection records must be maintained for a period of 3 years and must be made available to CDPHE/EPA upon request

8. Colorado Regulatory Requirements (cont.)
CDPHE Allows Some Flexibility in Defining the Area to be Covered by a Stormwater Permit
Single site with disturbance greater than 1 acre
Multiple sites within a common plan of development
Interpreted to be sites up to ¼ mile apart and/or having the area between the sites disturbed

9. Colorado Regulatory Requirements (cont.)
Final Stabilization as Applied to Construction
Construction has been completed and disturbed areas have been built on, paved, or at least 70% of pre-disturbance vegetation has been established or equivalent permanent, physical erosion reduction methods have been employed
Stabilized unpaved surfaces – Dirt road surfaces and portions of pads that cannot be revegetated due to operational necessity are considered finally stabilized as long as they are prepared as to prevent ongoing erosion issues

10. Stormwater Management Plans (SWMPs)
SWMP Goal
to describe appropriate controls and measures to improve water quality by reducing pollutants in stormwater discharges and ensure compliance with the requirements of the stormwater permit. The SWMP must be completed and implemented at the time the project breaks ground, and revised if necessary as construction proceeds to accurately reflect the conditions and practices at the site.

11. Stormwater Management Plans (Cont.)
SWMP Requirements
General Requirements
Prepared in accordance with good engineering, hydrologic and pollution control practices
Identifies Best Management Practices (BMPs)
Identifies potential sources of pollution associated with construction activity
Construction operations must implement the provisions of the SWMP

12. Stormwater Management Plans (Cont.)
SWMP Requirements (cont.)
Narrative Site Description
Describe construction activity
Sequence for major activities
Estimates of total area of site and area that will be disturbed
Estimate of runoff coefficient of the site before and after construction
Location of other potential pollution sources
Location and description of non-stormwater components of discharge (springs, landscape irrigation return, etc.)
Name and description of receiving water(s) or municipal storm sewer

13. Stormwater Management Plans (Cont.)
SWMP Requirements (cont.)
Site Map
Construction site boundaries
Areas of soil disturbance
Areas of cut and fill
Areas used for storage of building materials, soils or wastes
Location of any dedicated batch plants
Location of major erosion control facilities or structures
Surface waters
Boundaries of 100-year flood plains

14. Stormwater Management Plans (Cont.)
SWMP Requirements (cont.)
BMPs and Other Controls
Description of appropriate controls and measures that will be implemented
Structural Practices
Non-Structural Practices
Identify procedures to control spills, etc. (coordinate with SPCC plans)
Identify other measures to control pollutants (waste disposal, limiting off-site soil tracking, etc.)
Site stabilization methods
Inspection and maintenance procedures

15. Stormwater Management Plans (Cont.)
SWMP Requirements (cont.)
SWMP Revision
The SWMP must be modified to accurately reflect the actual field conditions and BMPs used
SWMP Administration
The SWMP must be on site during active construction and site inspections and available to those directly responsible for installing an maintaining BMPs

16. Best Management Practices (BMPs)
Reflect the measures taken to control stormwater as dictated by the SWMP.
Proper selection and implementation of BMPs are the keys to an effective stormwater management program
Common sense approach
There is no one right answer
Often involves trial and error to find what works best
Describe a wide range of structural treatment processes, pollution prevention practices, schedules of activities, prohibition on practices, and other management practices

17. Best Management Practices (cont.)
BMPs fall into 2 general categories
Nonstructural – Operational/managerial techniques, such as
Phasing of operations
Housekeeping practices
Spill prevention
Preventive maintenance
Preserving natural vegetation
Structural – Physical processes
Erosion Control BMPs – Practices to prevent the erosion of soil
Sediment Control BMPs – Practices to remove sediment from runoff

18. BMP Examples

19. Silt Fence The silt fence has been installed correctly
The silt fence needs to be repaired and BMPs should not be placed in drainage waters of the US

20. Straw Bales/Waddles
This technique utilizes bound straw bales to filter sediment from runoff of small areas
Limitations
Filters sheet flow from small drainage areas
Short term use
Decomposes and/or consumed by livestock
Removal of stakes will be necessary after stabilization is complete
Installation
Embed into trench
Anchor with 2 stakes (metal or wood)
Compact backfill on the upgradient side
Use at outfall points from sediment ponds, diversion ditches, turnouts, etc.

21. Straw Bales/Waddles

22. Sediment Pond (Trap)
This technique uses a pond to hold sediment-laden water so that sediment can settle and water is absorbed into the soil. Sediment traps are useful for construction sites where excessive runoff will need to be captured and filtered.
Limitations
Size of surrounding area
Require regular maintenance due to sediment build-up
Installation
Excavate trap or basin within area where runoff may be directed toward
Sideslopes should be machine compacted
Sideslopes should be 2:1 or flatter
Volume of trap should handle runoff from 2-year storm event
Construct spillway or outfall structure with rock, straw bale, or other appropriate BMP

23. Sediment Pond
Vertical and steep slopes should be avoided as these will result in erosion

24. Diversion Ditch
This technique is useful to filter sediment from concentrated flows and/or runoff of moderate grades and larger drainage areas. Additionally, rock berms may be utilized to reduce velocity of flows within diversion ditches
Limitations
Availability and/or cost of rock
Difficult to remove after construction
Require regular maintenance due to sediment build-u
Installation
Use medium to large diameter rock
May secure rock within woven wire sheathing (not required)
Berm side slopes should be 3:1 or flatter
Top of berm should be a minimum of 2 feet wide

25. Diversion Ditch

26. Geotextiles/Erosion Blankets
Geotextiles and erosion blankets are typically a porous fabric constructed of woven fibers. They are useful for stabilization and preventing erosion on slopes, especially adjacent to streams
Limitations
Decompose
Effectiveness depends on proper installation
Expensive
Installation
Select appropriate fabric type for necessary purpose
Remove any protruding rocks and smooth soil prior to installation
Fabric needs to be entrenched into the soil
Anchor fabric securely
Apply seed prior to fabric installation for final stabilization of sites
Follow manufacturer’s recommendations for installation

27. Erosion Control Blanket

28. Surface Roughening (Tracking)
This technique utilizes the horizontal grooves created by tracks of construction equipment to reduce runoff flow velocities. Tracks are established on the slopes perpendicular to water flow.
Limitations
Not for use on rocky slopes
May cause soil compaction which limits vegetation re-growth
Roughening may have to be re-established if lost due to heavy sheet flow runoff
Installation
Tracking should be done up and down the slope, not across the slope

29. Surface Roughening

30. Road-Side Ditches
This technique requires construction channels parallel to access roads. The ditches convey concentrated runoff of surface water from roads and surround areas to a stabilized area
Limitations
Erosion occurring within channel
Channel does not necessarily filter sediment from runoff
Installation
Excavate channel along roadside to a width and depth that can handle expected flows
Slope channels so that water velocities do not cause excessive erosion
Install BMPs into the ditches to slow water velocities and collect sediment

31. Road-Side Ditches

32. Berm/Water Bar
This technique may be used to collect runoff from undisturbed areas and divert around construction activity. Additionally, berms can be used to limit the accumulation of water volume by diverting runoff from construction area into a stabilized outlet (i.e. rundown, sediment pond) or a well-vegetated area
Limitations
Not for use on concentrated flows
May cause concentrated flows from sheet flow
Requires vegetative cover or other filter at discharge point
Installation
Pile and compact soil (berms need to be compacted to hold water, prevent blow-outs and minimize vandalism/intention breaches)
The side slopes should be 2:1 or flatter
Increase the frequency of water bars with an increased slope
Discharge should enter a well-vegetated cover (water bars) or a stabilized out (a constructed sediment pond)

33. Water Bar

34. Questions ?