Update on the Stormwater Permitting Program Megan Moir Water Quality Division.

Update on the Stormwater Permitting Program

Megan Moir Water Quality Division

Stormwater Permit Programs

Operational

Impervious Surface

(a.k.a. State Stormwater Permits, 9015, INDS)

Construction

Disturbed Soil

(a.k.a. CGP, 9001, 9020, INDC)

MS4

“Big picture” permit for concentrated

population centers

Multi-Sector

“Industrial” facilities

(a.k.a. industrial permit MSGP, 9003)

State Stormwater PermitJurisdictional Thresholds

Thresholds are based on area of impervious surface Impervious = man made surfaces, including, but not limited to, paved

and unpaved roads, parking areas, roofs, driveways and walkways from which precipitation runs off rather than infiltrates.

A State Stormwater Discharge Permit is required for projects which involve: New impervious ≥ 1 acre; Redevelopment of existing impervious ≥ 1 acre. Expansions with ≥ 1 acre total resulting impervious surface

(existing/redevloped + new), unless qualify for exemption expansion < 5000 sf and cumulative expansions since 7/4/2005 < 5000 sf

Thresholds are applied to the common plan of development, not individual phases!!!

State Stormwater Discharge Permits

Are you constructing new impervious or redeveloping existing impervious surfaces? If you are doing both, examine jurisdiction for each type.

Redevelopment of Existing Impervious Surface

Does the surface being redeveloped have an existing, valid stormwater permit?

yes

No additional permit is necessary, but no matter how much you are redeveloping, you must provide the same or better level of treatment that was in the previous permit. Please submit plans of redevelopment to be included in previous permit

file. *

Are you redeveloping ≥ 1 acre?

Must obtain a 9015 permit; must reduce impervious surface by 20% of area you are redeveloping or provide treatment for 20% of the WQv from the redeveloped

area. *

no

yes

New Impervious Surface

Are you constructing > 5000 s.f of impervious?

Has there been any construction of impervious since 7/4/2005?

Will the amount you are constructing plus what has been built since 7/4/2005 exceed 5000 s.f.?

no

no

yes

yes

Is there any existing impervious in the project or on some related parcel (see “total resulting”)?

yes

no

Is the total resulting (new + existing/redeveloped) impervious surface ≥ 1 acre?

yes

You must obtain coverage under a State Discharge Permit for these new surfaces by demonstrating compliance with the 2002 VT Stormwater Management Manual; existing surfaces that were previously permitted must still receive the same treatment as in their original permit. Changes to previously permitted existing surfaces should be submitted for review.

No permit necessary for new surfaces; existing surfaces that were previously permitted must still receive the same treatment as in their original permit. Changes should be submitted for review.

no

You must obtain coverage for the new surfaces under a State Discharge permit by demonstrating compliance with the 2002 VT Stormwater Management Manual.

yes

Are you constructing ≥ 1 acre of new impervious?

yes no

*These areas still count towards your total resulting impervious when dealing with impervious expansions!

no

No permit necessary

no

Do I need to obtain a State Stormwater Discharge Permit?Permitting Flow Chart for Stormwater Discharges from Impervious Surfaces to Waters not Impaired by Stormwater

Permitting thresholds are the same for discharges from impervious surfaces to waters impaired by stormwater. However, the process of obtaining a permit is more complicated. Projects in impaired watersheds should refer to Chapter 22 and/or contact the Stormwater Section.

New impervious ≥ 1 acre

1 ac impervious

Permit REQUIRED!

Remember, the determination must take into account all impervious in common plan of development

Phased development must be looked at as a whole

Undeveloped Land


Redevelopment ≥ 1 acre of existing impervious

0.75 ac impervious in footprint of original impervious

1.0 ac impervious in footprint of original impervious

Permit NOT required!

Permit REQUIRED!

But obtaining permit is not as involved – only have to treat 20% of the Water Quality Volume or remove an amount of existing impervious equivalent to 20% of the redeveloped area.


"Redeveloped impervious": the reconstruction of an impervious surface where an impervious surface currently exists, when such reconstruction involves substantial site grading, substantial subsurface excavation, or modification of existing stormwater conveyance. Redevelopment does not mean management activities on impervious surfaces, including any crack sealing, patching, cold-planing, resurfacing, paving a gravel road, reclaiming, or grading treatments used to maintain pavement, bridges and unpaved roads. Redevelopment does not include expansions.

Expansions: “Total Resulting Impervious”

For purposes of determining whether or not an expansion of existing impervious will require a Stormwater discharge permit, the following apply: Existing impervious, and total resulting impervious shall include all impervious

area within the parcel on which the subject activity is taking place, and the impervious area on other parcels linked by a common plan of development. A common plan of development includes large projects, and subdivisions, the operation or creation of which required or requires state or local permits related to either the regulation of land use or discharge to state waters.



For example, determinations must examine the existing impervious on all parcels that are under the jurisdiction of landuse permits such as an Act 250 permit, parcels that share common infrastructure (wastewater, roads, water supply etc), or parcels that are in some other way part of a discernible common plan of development. i.e. someone subdivides their property into two lots, one of which contained a

house and driveway, and then later subdivided the second lot into multiple lots that were going to be sold for home construction.



One would need to consider both the new impervious as well the existing impervious on the other parcel that was part of the Act 250 process. If not Act 250 permit was involved, the common plan of development might be indicated by a shared private road serving all homes including the existing home, or a shared water/wastewater system.

The new impervious is considered an expansion to the original impervious on the original lot, and the existing impervious must be counted as part of the “total resulting impervious”.

New impervious = 0.95 acres Existing impervious = 0.10 acres Total resulting = 1.05 acres

Thus a permit is required for the expansion!

No treatment is required for the existing impervious.



For purposes of determining whether or not an expansion of existing impervious will require a Stormwater discharge permit, the following apply: Existing impervious, and total resulting impervious shall include all impervious

area within the parcel on which the subject activity is taking place, and the impervious area on other parcels linked by a common plan of development. A common plan of development includes large projects, and subdivisions, the operation or creation of which required or requires state or local permits related to either the regulation of land use or discharge to state waters.

For highway/linear projects, the total resulting impervious shall include all impervious surface with the project limits.

e.g.

expansion

project limits


Allen Brook

Englesby Brook

Munroe Brook

Bartlett Brook

Indian Brook

Potash Brook

Centennial Brook

Morehouse Brook

Sunderland Brook

Rice Brook

Clay Brook

Moon Brook

Roaring Brook

East Branch of Roaring Brook

N. Branch of Deerfield

STORMWATER IMPAIRED WATERSHEDS


Jurisdictional thresholds are the same, but sediment load calculations are required in addition to meeting 2002 VSWMM - see Chapter 22 of the Stormwater Rule for more information

Overview of the 2002 Vermont Stormwater Management Manuals (VSWMM)

Unified Sizing Criteria Water Quality Channel Protection Groundwater Recharge Overbank Flood Protection Extreme Flood Protection

Pre-Approved STP Designs Required Design Elements Design Guidance Cold Climate Required Elements

and Design Advice

Site Design Credits

Volume I – SW Treatment Standards

Now in our 5th printing!


Overview of the 2002 Vermont Stormwater Management Manuals (VSWMM)

Site Design and Landscaping Selecting the most effective stormwater

treatment system Landscaping Guidance and Plant Lists

STP Construction Specs Construction specifications for infiltration, sand

filters, bioretention and open channels

Design Examples 5 complete design examples

Assorted Design Tools Miscellaneous Technical References

Volume II – Technical Guidance


Water Quality Treatment

Goal: Capture and treat 90% of the annual runoff producing events generated by the site Treat = use an approved structural (i.e. pond, filter, infiltration basin)

or non-structural (i.e. disconnection) practice which has been shown to remove 80% TSS and 40% TP

Provide treatment for the entire site’s runoff up to the 0.9” storm

Water Quality Volume (WQv) = (0.9*Rv*A)/12 where: A = site area (impervious + disturbed pervious) Rv = 0.05+0.009I (I = % impervious)

Minimum WQv = 0.2 watershed inches


Amount of impervious area is largest contributor

WQv formula simplifies to:

0.00375A + 0.0675(IA), where IA = impervious area (acres)

Water Quality Treatment

Typical STPs Ponds Wetlands Infiltration Systems Filters (including Bioretention) Grass Swales (specially designed)

Treatment practices included in Volume I of the 2002 SWMM are identified as providing 80% removal of TSS and 40% removal of TP


Groundwater Recharge Goal: To preserve existing water table elevations by maintaining the average annual

recharge rate for the site Replicate pre-development recharge through a standard based upon the annual average

recharge of the site’s existing Hydrologic Soil Groups (i.e. no recharge required for D soils)

Table 2.2 in the VSWMM manual lists acceptable stormwater treatment practices for recharge


0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0 10 20 30 40 50 60 70 80 90 100Site Imperviousness [%]

Rec

har

ge

Vo

lum

e [W

ater

shed

Inch

es]

A Soils

D Soils

C Soils

B Soils

Site Design Credits

Site Design Credits are often used to meet Water Quality and Recharge Requirements

Currently Approved Site Design Credits Conservation Areas Disconnection Stream Buffers Grass Channels Environmentally Sensitive Rural Development

Pay careful attention to each of the criteria that must be met in order to qualify for these credits Slope Land-use/density Contributing length : treatment length, etc.

Slope requirements

Slope and land-use requirements


Channel Protection

Goal: Protect downstream receiving channels from degradation

Provide 12 or 24 hour detention of site runoff from the 1 year – 24 hour storm (approximately 2.1 - 2.3 inches in Vermont) 12 hour detention for cold water

receiving streams 24 hour detention for warm water

receiving streams or wetlands

Waived for sites With < 1 acre of expansion; With < 2 cfs of discharge; or Discharging to waterbody with > 10 sq.

mi. drainage area


Channel Protection: CPv

Qcrt

Qpost –higher Q and larger Vr

Qpre

Qcrt

Qpre

Qpost-controlled

Providing peak discharge control DOES NOT meet CPv The goal is to release runoff gradually so that critical erosive flows/velocities

(Qcrt) will seldom be exceeded downstream. The extended detention is used as a surrogate for the more involved Distributed

Runoff Control method (Appendix D9, 20 pgs long), which is the more involved method of determining the appropriate channel protection release rate.

Q Q

TimeTime

Overbank Flood Protection (Qp10)

Goal: Protection of downstream infrastructure from an increase in the frequency and magnitude of overbank flooding

Provide storage to control the peak discharge of the post developed runoff volume from the 10-year, 24-hour storm (ranges from 3.1 to 4.0 inches in Vermont ) by releasing at the pre-development runoff rate.

Qp10 may be waived for projects where: Discharges to receiving waters with drainage areas greater than 10 sq.

miles; or Site is smaller than 5 acres AND channel has capacity to convey the

post development discharge downstream to the point of the 10% rule


Extreme Flood Protection (Qp100)

Goal: Prevent flood damage from infrequent but very large storm events, maintain the boundaries of the predevelopment 100-year floodplain, and protect the physical integrity of a stormwater management practice itself

Provide storage to control the peak discharge rate of the post development runoff volume from the 100-year, 24‑hour storm (ranges from 5.0 – 6.8 inches in Vermont) by releasing at the predevelopment runoff rate.

Qp100 may be waived for projects where: Discharges to receiving waters with drainage areas greater than 10 sq.

miles; or Impervious acreage < 10 acres; or A downstream analysis is conducted that indicates extreme flood

control is not necessary


Demonstrating Compliance

Design standards Water Quality

Pre-treatment: largely to reduce maintenance frequency Treatment: Standards linked to unit processes of different

types of practices, e.g.:– Ponds: settling/sedimentation; biologic processes– Infiltration– Grass Channels: sedimentation– Filters: physical filtration and/or sorption depending on media– NEED TO KNOW HOW EACH PRACTICE WORKS TO DESIGN

EFFECTIVE TREATMENT

Water Quantity Runoff models with detention components.

Importance of Models

Construction Stormwater Permitting in Vermont - Overview

Since 2002, 5 acre+ projects have required permits

New General Permit issued September 13, 2006 for 1 acre+ disturbance projects, replaces original permit

Required by Federal Clean Water Act and National Pollutant Discharge Elimination System Phase II (NPDES)

Includes smaller projects part of larger common plan of development

Construction Stormwater Permitting in Vermont - Overview

Winter Construction Winter Oct 15-Apr 15

Requires notification of planned work, implementing standard winter EPSC measures, including: Daily mulching (unless work is in a self contained trench and/or no

precipitation is forecast for the next 24 hours) Double the mulching rate

Construction Stormwater Discharge Permits

Construction Stormwater Permitting in Vermont-Filing Applications

CGP Eligibility determined by Risk of Sediment Discharge and receiving water sensitivity Type of Waters (impaired, Outstanding Resource) Extent of Disturbance (2 acres, 5 acres, 7 acres) Duration of Disturbance (7, 14, or 21 days) Slopes and Soils Presence/absence of Vegetated Buffers Work within resource buffer


3 Permitting Possibilities:

1. Low Risk2. Moderate Risk3. Individual Permit

Construction Stormwater Permitting in Vermont-Filing Applications

Eligible for General Permit


Construction Stormwater Permitting in Vermont – Filing Applications

Risk EvaluationRisk Evaluation Series of Yes/ No, Q/A Focused on Erosion Prevention Encourages voluntary phasing,

prompt stabilization, use of vegetated buffers

If project is not automatically low risk, then must do detailed evaluation comparing risk factors and risk mitigation factors.



Basic Risk EvaluationBasic Risk EvaluationProject is automatically Low Risk if meet all of the

following:1. < 2 acres2. 50 ft vegetated buffer3. 14 days maximum disturbance in any area before temporary

or permanent stabilization4. Not discharging to special class of water



Low Risk ProjectsLow Risk ProjectsSubmit Notice of IntentAgree to implement Low Risk Guide ~10 days to authorizationValid for 2 years



Low Risk HandbookLow Risk Handbook Common practices Basic use Suited to low risk

construction



Once AuthorizedOnce Authorized Receives Notice of

Authorization Lists all voluntary limits Posted at site for public and

inspector reference, remind permittee



Moderate Risk ProjectsModerate Risk Projects Submit Notice of

Intent Site specific EPSC

plan with EPSC Summary Forms



Once AuthorizedOnce Authorized Receives Notice of

Authorization for posting Receives OSPC Handbook Receives Field Guide


Construction Stormwater Permitting -Field Implementation-

On-Site Plan Coordinator in charge of compliance

Weekly & Post-Runoff Inspections Discharge Reports Track Amendments On-Site Plan Coordinator Handbook



Projects Requiring Projects Requiring Individual PermitIndividual Permit

Submit Application Site specific EPSC plan Usually WQ

monitoring, EPSC specialist oversight


General ApproachGeneral Approach Minimize Minimize

disturbancedisturbance Manage runoffManage runoff Stabilize Stabilize

promptlypromptly Establish Establish

VegetationVegetation

Erosion Prevention and Sediment Control Erosion Prevention and Sediment Control PlanPlan


Frequent mulchingFrequent mulching

EPSC- StabilizationEPSC- Stabilization

Construction Discharge Permits

Silt fenceSilt fence Show silt fence on EPSCP sheet as it should be - ON THE CONTOUR!Show silt fence on EPSCP sheet as it should be - ON THE CONTOUR! Inspection and maintenance are a must!Inspection and maintenance are a must!

Silt fence should NOT be used for demarcation of the limits of disturbance!Silt fence should NOT be used for demarcation of the limits of disturbance!

EPSC- Perimeter ControlEPSC- Perimeter Control


EPSC- Perimeter ControlEPSC- Perimeter Control


Multi-Sector General Permit for Stormwater

Discharges Associated with Industrial Activities

(3-9003)

Christy WittersDEC Stormwater Section

www.vtwaterquality.org/stormwater.htm

(802) 241-3777

http://www.vtwaterquality.org/stormwater.htm

http://www.vtwaterquality.org/stormwater.htm

MSGP Outline

Purpose Who requires MSGP coverage Types of MSGP coverage

No Exposure Conditional Exclusion Notice of Intent (NOI)

Due dates for applying Application review procedure

MSGP Overview

Goal: Prevent pollution from industrial activities VT MSGP signed August 18, 2006 5 year National Pollutant Discharge Elimination

System (NPDES) permit required by Federal law Requires facilities that have industrial materials

or activities exposed to stormwater to: Prepare a Stormwater Pollution Prevention Plan

(SWPPP) Monitor outfalls for potential pollutants

Regulated Activities

Industrial facilities SIC code of the facility’s primary activity is

listed in Table D-1 of the permit

Regulated Activities Any facility with one of the following activities on site:

Stormwater discharges with specific effluent limitations (Table 1-1)

Types of MSGP coverage

No Exposure Conditional Exclusion Certify that the facility meets the No

Exposure conditions Permit Coverage

Submit Notice of Intent Prepare Stormwater Pollution Prevention

Plan (SWPPP) Implement Best Management Practices

(BMPs) Conduct Monitoring

No Exposure

No Exposure All materials and activities are protected by a

storm resistant shelter to prevent exposure to rain, snow, snowmelt, and/or runoff

Storm resistant shelter

No Exposure Materials that may be stored outdoors

Final products intended for outdoor use & not deteriorating

Lidded dumpstersAbove Ground Storage Tanks not associated with vehicle maintenance

Adequately maintained vehicles

Sealed drums, barrels, tanks without operational taps or valves; not deteriorating

Types of MSGP coverage

Full Application for coverage Notice of Intent (NOI) – application form

Prepare and implement Stormwater Pollution Prevention Plan (SWPPP)

• Best Management Practices (BMPs) Behavioral and Structural BMPs

Conduct stormwater monitoring

Application deadlines

No Exposure – immediately NOI

Existing facilities – immediately New facilities – 90 days prior to commencing

activities SWPPP

Existing facilities – May 15, 2007 New facilities – 90 days prior to commencing

activities

Application Review Procedure No Exposure

Applications checked for completeness and approved

NOI Applications checked for completeness 10 Day Public Comment Period Activity authorized under the permit

SWPPP Reviewed when they are received Expecting most SWPPPs near May 15

deadline

Eight municipalities (Burlington, Essex, Essex Jct, Milton, Shelburne, South Burlington, Williston and Winooski

Three “non-traditional” (systems owned or operated by UVM, Burlington International Airport and VTRANS)

Municipal Separate StormwaterMunicipal Separate Stormwater SystemsSystems

(MS4)(MS4)

MS4 Permits

MS4 6 Minimum MeasuresMS4 6 Minimum Measures

1. Public Education and Outreach www.smartwaterways.org

2. Public Participation and Involvement

3. Illicit Discharge and Detection Elimination

4. Construction Site Runoff Control

5. Post-construction Site Runoff Control

6. Pollution Prevention / Good Housekeeping

MS4 Permits

For questions, contact Jim Pease at VT SWMP

http://www.smartwaterways.org/

Update on the Stormwater Permitting Program Megan Moir Water Quality Division.

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