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Stormwater Management

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Background. In 1992, the State of Colorado stormwater regulation went into effect to control municipal and industrial stormwater discharges, based on EPA regulations. – PowerPoint PPT presentation

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Title: 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
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