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Post-Construction Storm Water Control for New Developments and Redevelopment Projects Presenters: Christe Alwin, Lansing District Office Ralph Reznick, Nonpoint Source Unit MS4 Permit References Watershed Permit MIG610000 Part 1.A.4.b.4. (Pages 15-17) Jurisdictional Permit MIS049000

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post construction storm water control for new developments and redevelopment projects

Post-Construction Storm Water Control for New Developments and Redevelopment Projects

Presenters:

Christe Alwin, Lansing District Office

Ralph Reznick, Nonpoint Source Unit

ms4 permit references
MS4 Permit References
  • Watershed Permit MIG610000

Part 1.A.4.b.4. (Pages 15-17)

  • Jurisdictional Permit MIS049000

Part 1.A.8. (Pages 10-12)

City of Battle Creek—porous pavement

core requirement
Core Requirement
  • Develop, implement, and enforce a program through an ordinance or other regulatory mechanism to address post-construction storm water runoff from:
    • all new and redevelopment projects that disturb ≥1 acre, and
    • projects that disturb <1 acre if they are part of a larger common plan of development or sale that would disturb ≥1 acre.

Applies to Permittee and Non-Permittee Projects

what is post construction storm water runoff
What is Post-Construction Storm Water Runoff?

The storm water that would flow from a project site to an MS4 or surface waters of the state followingconstruction.

City of Battle Creek—green roof

scope of post construction control requirements
Scope of Post-Construction Control Requirements
  • Watershed Permit:
    • Across the permittee’s jurisdiction in the regulated area (the Urbanized Area and watershed area).
  • Jurisdictional Permit:
    • Discharges to the permittee owned or operated MS4 within the Urbanized Area.
scope of post construction control requirements7
Scope of Post-Construction Control Requirements
  • Watershed Permit:
    • Across the permittee’s jurisdiction in the regulated area (the Urbanized Area and watershed area).
  • Jurisdictional Permit:
    • Discharges to the permittee-owned or operated MS4 with the Urbanized Area.
how is the post construction program implemented and enforced
How is the post-construction program implemented and enforced?
  • Ordinance
  • Other regulatory mechanism
  • A combination of both
permittee expectations
Permittee Expectations
  • Establish a post-construction control program through an ordinance or other regulatory mechanism.
  • May rely on others to assist with completing the necessary reviews and calculations.

Compliance with permit requirements is ultimately the responsibility of the permittee.

post construction storm water runoff control program required components
Post-Construction Storm Water Runoff Control Program Required Components
  • Minimum Water Quality Treatment Volume Standard
  • Channel Protection Criteria
  • Site Plan Requirements
  • Operation and Maintenance Requirements
  • Enforcement Mechanisms
  • Recordkeeping Procedures

City of Lansing—raingardens

slide14

Program Components

  • Minimum Water Quality Treatment Volume Standard

Channel Protection Criteria

Site Plan Requirements

Operation and Maintenance Requirements

Enforcement Mechanisms

Recordkeeping Procedures

Minimum Treatment Volumes:

  • 1 inch of runoff generated from the entire site (½ inch optional for the Watershed Permit if the Watershed Management Plan supports it)
  • The calculated site runoff from the 90 percent annual non-exceedance storm for the region or locality
simple method to calculate runoff volume
Simple Method to Calculate Runoff Volume

WQv = Water Quality Volume

= [(P)(Rv)(A)] /12

Rv = 0.05+0.009(I)

I = Impervious Cover (Percent)

Minimum Rv = 0.2

P = 90% Rainfall Event Number

A = site area in acres

www.semcog.org/LowImpactDevelopment.aspx

Minimum Treatment Volume

slide17

Treatment Design

  • Treatment methods shall be designed on a site-specific basis to achieve the following:
    • Minimum of 80 percent removal of total suspended solids (TSS), as compared with uncontrolled runoff, or
    • Discharge concentrations of TSS not to exceed 80 milligrams per liter (mg/l)
treatment mechanisms
Treatment Mechanisms
  • Settling
  • Filtering
  • Absorption
  • Chemical Treatment
  • Mechanical Treatment

Minimum Treatment Volume

slide19

National Pollutant Removal Performance Database, 2nd Edition

Table 3.1 Median Pollutant Removal (%) of Stormwater Ponds and Wetlands

slide20

References

BMP Performance data can be found in;

National Pollutant Removal Performance Database, Version 3 at:

www.cwp.org/Resource_Library/Center_Docs/SW/bmpwriteup_092007_v3.pdf

and The International Stormwater BMP Database at:

http://www.bmpdatabase.org/Docs/Performance%20Summary%20June%202008.pdf

BMP design information can be found in;

Low Impact Development Manual for Michigan available at:

http://library.semcog.org/InmagicGenie/DocumentFolder/LIDManualWeb.pdf

and the Guidebook of BMPs for Michigan Watersheds available at:

http://www.michigan.gov/deq/0,1607,7-135-3313_3682_3714-118554--,00.html

Minimum Treatment Volume

minimum treatment volume
Minimum Treatment Volume

Total Area X 1 inch

or

90 percent annual non-exceedance storm and

appropriate runoff model applied to the site.

then

Apply BMP or BMPs necessary to achieve 80% reduction of Total Suspended Solids

Minimum Treatment Volume

slide22

Program Components

Minimum Water Quality Treatment Volume

  • Channel Protection Criteria

Site Plan Requirements

Operation and Maintenance Requirements

Enforcement Mechanisms

Recordkeeping Procedures

Existing levels = runoff flow volume and rate for the last land use prior to the planned new development or redevelopment.

Channel Protection Criteria:

  • Maintain post-development site runoff volume and peak flow rate at or below existing levels
  • All storms up to the 2-year, 24-hour event
slide24

Stream Stability

The ability of a stream, over time, to maintain its pattern, dimension and profile such that, the channel neither aggrades or degrades and is able to transport without adverse impact the flow and sediment from it’s watershed.

Channel Protection Criteria

definition bankfull discharge
Definition: Bankfull Discharge

That discharge which barely overtops the channel banks

Maximumdeposition & erosioncirculation cell development

Channel Protection Criteria

slide27

The most effective

sediment discharge,

over time, occurs at

the bankfull flow rate

which is between the 1 to 2 year recurrence interval.

At the bankfull flow,

the stream bottom picks

up and moves, then

redistributes its self

in the same pool &

riffle patterns existing

prior to the bankfull

discharge.

Channel Protection Criteria

Taken from Rosgen, 1996

slide28

Streams become unstable due to:

  • Changes in Climate
  • Changes in Hydrology
  • Changes in Topography
  • Changes in Vegetation
  • Changes in Geology
  • Alterations of the Stream Channel

Channel Protection Criteria

slide29

The Channel Protection requirements in the MS4 Permit address changes in hydrology due to development and the negative channel responses that result.

maintaining predevelopment hydrology
Maintaining Predevelopment Hydrology
  • Time of Concentration (Tc)
    • The time it takes water to get from the farthestpoint in a watershed to a point of collection.
  • Volume
    • The quantity of water that runs off a site during a storm event.
  • Peak Flow Rate
    • The highest flow rate of a storm event.

Channel Protection Criteria

slide33

CN

CN

Channel Protection Criteria

slide34

Calculates rate and volume of

storm runoff using the unit

hydrograph method for runoff

distribution and the curve

number method of land use

runoff response.

www.michigan.gov/deqstormwater (under the “Municipal Program/MS4 Compliance Assistance” link, then the “Guidance for Calculating Runoff Volume and Peak Flow Rate” link)

slide35

24 HourPrecipitationRainfall Frequency Atlas of the Midwest, Bulletin 71, Midwestern Climate Center, 1992

slide36
Hydrograph for a farm on sandy soil or woods on loamy soil.

Qp=23 cfs V=5 acre-ft.

Dave Fongers - DNRE

Channel Protection Criteria

slide37

Loss of infiltration due to development increases total runoff volume and peak flows.

Qp=65 cfs V=11 acre-ft.

Qp=23 cfs V=5 acre-ft.

Dave Fongers - DNRE

Channel Protection Criteria

slide38

More rapid runoff further increases peak flows.

Qp=90 cfs V=11 acre-ft.

Qp=65 cfs V=11 acre-ft.

Qp=23 cfs V=5 acre-ft.

Dave Fongers - DNRE

Channel Protection Criteria

controlling time of concentration
Controlling Time of Concentration
  • Maintain Natural Drainage Paths
  • Use open swales
  • Increase surface roughness
  • Detain flows
  • Minimize disturbance
  • Flatten grades in disturbed areas
  • Disconnect imperviousness
  • Connect pervious and vegetated areas

Channel Protection Criteria

slide40

CN

CN

Channel Protection Criteria

runoff curve numbers for urban areas
Runoff Curve Numbers For Urban Areas

Channel Protection Criteria

1 acre site on c soils
1 Acre Site on C Soils

Runoff

Volume to Remove

6310 ft3

Building

Meadow

CN = 71

Paved Parking

Paved Commercial Site

100% Impervious

CN = 98

Can be accomplished

with rain gardens on

approximately

20% of site

2 year runoff volume = 1640 ft3

2 year runoff volume = 7950 ft3

Channel Protection Criteria

reduce runoff volume
Reduce Runoff Volume
  • Infiltrate
  • Evaporate
  • Reuse

Channel Protection Criteria

1 acre site on c soils45
1 Acre Site on C Soils

Runoff

Volume Reduction

1331 ft3

Open Space

CN = 79

Woods

CN = 70

2 year runoff volume = 2847 ft3

2 year runoff volume = 1516 ft3

Channel Protection Criteria

slide46

Channel Protection

Determine Existing Runoff Volume Using CN Method

then

Determine Proposed Runoff Volume and Subtract Existing to determine Runoff Volume Increase

then

Apply BMPs to Remove the Runoff Volume Increase

Channel Protection Criteria

slide47

Channel Protection

  • Meeting the Channel Protection Criteria for Volume Control will also meet the Peak Rate Control requirement in most cases.
  • For NEW development, meeting the Channel Protection Criteria for Volume Control will also meet the Minimimum Water Quality Treatment Volume criteria in almost all cases.

Channel Protection Criteria

special conditions
Redevelopment

Transportation

Tight Soils

Brown Fields

Permittees are encouraged to discuss special conditions with District Staff.

Special Conditions

Channel Protection Criteria

slide50
Program Components

Minimum Water Quality Treatment Volume

Channel Protection Criteria

  • Site Plan Requirements

Operation and Maintenance Requirements

Enforcement Mechanisms

Recordkeeping Procedures

Permittees shall include a requirement that the developer prepare and implement site plans for each project subject to the post-construction control requirements.

site plans

Site Plans

Site Plans
  • Allows the permittee to require and evaluate post-construction control details at the planning stage.
  • Sets a foundation for ensuring finished project sufficiently meets post-construction control requirements.
  • Permittees should have a checklist or criteria for plan reviewers.

City of Battle Creek—rain garden

slide52

Program Components

Minimum Water Quality Treatment Volume

Channel Protection Criteria

Site Plan Requirements

  • Operation and Maintenance Requirements

Enforcement Mechanisms

Recordkeeping Procedures

Permittees shall ensure long-term Operation and Maintenance (O&M) plans for the water quality treatment and channel protection controls the permittee requires.

o m requirements
O&M Requirements
  • O&M requirements shall be

incorporated into the permittee’s

ordinance or regulatory

mechanism.

  • Applies to structural and vegetative Best Management Practices (BMPs), including those owned or operated by the permittee.
  • Permittees shall review O&M plans and have a tracking mechanism for long-term O&M.
o m recommendations
O&M Recommendations
  • Construction inspections, performance bonds, and self-certification process
  • Routine ongoing

inspections

  • Maintenance

agreements

  • Tracking O&M
slide55

Program Components

Minimum Water Quality Treatment Volume

Channel Protection Criteria

Site Plan Requirements

Operation and Maintenance Requirements

  • Enforcement Mechanisms

Recordkeeping Procedures

The permittee’s ordinance and or regulatory mechanism is the foundation for implementing and enforcing the post-construction control program.

enforcement mechanisms
Enforcement Mechanisms
  • Ordinance and regulatory mechanism contents include all of the post-construction program components:
    • Treatment Volume Standard
    • Channel Protection Criteria
    • Developer Site Plan Requirement
    • Operation and Maintenance Requirements
    • Enforcement Mechanisms for Resolving Noncompliance
    • Any Recordkeeping Requirements Placed on the Developer
enforcement mechanisms57
Enforcement Mechanisms
  • Resolving noncompliance measures include but are not limited to:
    • Right of entry for inspections
    • Triggers for issuing notices of violation
    • Authority to require mandatory abatement
    • Permittee authorization to conduct BMP maintenance and re-coup costs
    • Ability to issue monetary penalties
slide58

Program Components

Minimum Water Quality Treatment Volume

Channel Protection Criteria

Site Plan Requirements

Operation and Maintenance Requirements

Enforcement Mechanisms

  • Recordkeeping Procedures
  • Recordkeeping procedures shall be in place to document enforcement of the post-construction control program through the ordinance or other regulatory mechanism.
recordkeeping requirements
Recordkeeping Requirements
  • Copies of post-construction storm water control ordinances, regulatory mechanisms, and any supplemental procedures.
  • Applicable records for all development and redevelopment projects required to comply with the post-construction program.
recordkeeping requirements60
Recordkeeping Requirements
  • Developer Site Plan
    • Checklists
    • Correspondence
    • Final approved design
  • O&M Plans or Agreements
    • Inspection and certification records
    • BMP tracking system
    • O&M inspections
  • Enforcement Actions
    • Violations
    • Permittee actions to address violations