Stormwater Management

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 1002-61) 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 CDPHEs 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 21 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 31 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 manufacturers 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 21 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 ?