6/12/2015 Treating Redevelopment: A Watershed Restoration Tool for - - PDF document

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South Carolina Association of Stormwater Managers Quarterly Meeting Mike MacIntyre, PE

June 11, 2015

Treating Redevelopment: A Watershed Restoration Tool for Local Governments Key Terms

• Development

– Land-disturbing activity that creates impervious area or that otherwise decreases the infiltration of precipitation into the soil

• Redevelopment

– Land-disturbing activity that does not result in a net increase in impervious area and that provides greater or equal stormwater control than the previous development

Building Addition

Development Example

Existing Building

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New Building Existing Building

Redevelopment Example Key Terms

• Detention

– Peak Control (flood relief)

• The controlled release of the runoff from 10-, 25-,

and possibly larger 6-hour storms to prevent flooding

• f downstream structures and properties

– Volume Control (stream erosion prevention)

• The slower, controlled release of the runoff from a 1-

year, 24-hour storm in order to protect streambanks from being eroded

Requirements for Development

• Meet each of the following requirements:

– Pollutant Removal

• Remove pollutants from runoff through filtration,

settling or infiltration – Detention

• Stream Erosion Protection and Flooding Relief for

Storm Drainage Systems, Streets, and Downstream Structures

• Hold & slowly release runoff from medium and large

rainfall events – Stream Buffer Protection

• Expands/complements previous efforts to preserve

buffers adjacent to streams – Natural Area Protection

• 10% to 25% depending on density of the

development (treed area)

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Requirements for the Transit Station Areas and the Distressed Business District (Yellow and Green Areas of the Map)

• Choose one of the following requirements:

– Pollutant Removal

• Remove pollutants from runoff through filtration,

settling or infiltration – Detention

• Stream Erosion Protection and Flooding Relief for

Storm Drainage Systems and Streets

• Hold & slowly release runoff from medium and large

rainfall events – Mitigation Fee

• Pay the City a mitigation fee to install water quality

enhancement measures within the same watershed

• And provide:

– Stream Buffer Protection – Peak Detention on Additional Impervious Area

Payment of Mitigation Fee – (Nov 2011-Jan 2015) in respect to Transit/Distressed Geography

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Requirements for Redevelopment (in White Area of the Map)

• Choose two of the following requirements:

– Pollutant Removal

• Remove pollutants from runoff through filtration,

settling or infiltration – Detention

• Stream Erosion Protection and Flooding Relief for

Storm Drainage Systems and Streets

• Hold & slowly release runoff from medium and large

rainfall events – Mitigation Fee

• Pay the City a mitigation fee to install water quality

enhancement measures within the same watershed (may be a larger fee if conditions are met)

• And provide:

– Stream Buffer Protection – Peak Detention on Additional Impervious Area

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Mitigation Fee

• Set by City Engineer based on City’s cost to design and

construct stormwater control measures

• Fee has not changed since inception (still many
• pportunities for cost-effective projects)
• As costs of projects increase and large, regional
• pportunities diminish, fee may increase

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Fee Structure

• Lots less than 1 acre [18-161(a)]- $60,000/impervious acre
• Within Transit Station Area/Distressed Business District

[18-161(b)]– $60,000/impervious acre

• Redevelopment [18-161(c)]-$ 60,000/acre for the first

impervious acre, then $90,000/impervious acre for each additional acre

• Mitigation fee is prorated for partial acres

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Fee Structure

$0 $100,000 $200,000 $300,000 $400,000 $500,000 $600,000 1 2 3 4 5 6 7

Redevelopment Site Size, acres

For Example, a 2 acre redevelopment site outside the transit/distressed areas pays a $150,000 fee in lieu of onsite controls

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Activity Centers

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“70% of new multi-family and 75% of new office to be constructed in Activity Centers and Growth Corridors, with emphasis in Growth Corridors on Transit Station Areas.”

Mixed Used Activity Centers

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Payment of Mitigation Fee – (Nov 2011-Jan 2015) in respect to other priority areas

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Redevelopment Projects paying Fee by Year

• How long have the mitigated projects been there?

Redevelopment Mitigation Payments Received By Fiscal Year 2012 – 4 projects, 3.49 acres 2013 – 1 project, 1.10 acres 2014 – 2 projects, 5.22 acres 2015 – 5 projects, 5.23 acres

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Redevelopment Projects Approved Since November 2011

17 Chart includes 4 redevelopment projects that have not yet been completed/paid the fee

8 2 6

Provided Detention and Paid Fee Paid Fee for Redevelopment and Met Development Standards for Increase Paid Fee Only

50% 12% 38%

Stormwater Control Measures Approved Since November 2011

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66 63 52 45 18 15 4 3 2 2 10 20 30 40 50 60 70

Above Ground Sand Filter Underground Detention Above Ground Detention Wet Pond Bioretention Underground Sand Filter Proprietary Device Wetland Infiltration Trench/Pond Permeable Pavement

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Screening Process to Allow a Fee for Detention

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Screening Process to Allow a Fee for Detention

• Is there an increase of impervious area on the project site?
• Are there open stormwater requests for erosion or flooding?
• Where does the project drainage area become less than

10% of the total drainage area?

• Are there other downstream concerns (e.g. – is there a

residential neighborhood that may be negatively impacted)?

• Is the local infrastructure adequately sized?
• What type of limitations are there on site?

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Limitations of Redeveloping Sites

Redevelopment sites often face substantial challenges accommodating stormwater controls on-site

• Difficult topography
• Underground utility conflicts
• Lack of available space onsite
• Brownfield sites
• Maintain site operations

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Why is there a fee in the first place?

• Existing paved sites typically have no form of runoff control
• Paved surfaces causes runoff that impairs surface waters
• Post Construction ordinance requires on-site measures
• Redevelopment faces challenges accommodating runoff

controls on-site

• Caps the compliance cost of affordable housing,

redevelopment projects, and increases economic development opportunities

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Why is there a fee in the first place?

• Increases flexibility, and predictability for redevelopment

projects

• Reduces greenfield development by making redevelopment

more affordable

• Accelerates watershed recovery by encouraging

redevelopment over green field development

• The offsite, regional approach recovers watersheds at a

faster pace.

• Offsite mitigation is an effective strategy in communities

nationwide to protect environment while considering costs

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What Other Local Governments Use Mitigation Fees?

• What other municipalities have a mitigation fee?

– Atlanta, GA – Austin, TX – Columbus, OH – Orlando, FL – Prince George County, MD – San Antonio, TX – San Francisco, CA – Tampa, FL – Washington, DC

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Operation and Maintenance

• Who maintains stormwater control measures?

– Private commercial projects: owner – Multi-family sites: owner – Single-family subdivisions: HOA may petition City to take over maintenance if the measure is in good order two years after it goes into service – Public projects: owner agency

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Redevelopment Case Study Seven Eleven – N Wendover Rd

Pre-Project Conditions (2011)

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Redevelopment Conditions (2015)

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Aerial Comparison 2013 Aerial 2014 Aerial

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Downstream Analysis

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Open Channel Stormwater Pipe Pipe installed by project.

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Downstream Analysis – 10% Point

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Open Channel Stormwater Pipe

Site Constraints

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• Side/Rear Yards and

Setbacks required by Zoning Ordinance

• Tree Save Areas required

by Tree Ordinance

• Internal Tree planting

required by Tree Ordinance

• Underground Stormwater

Control Measure (SCM) required by Post- Construction Stormwater Ordinance (PCSO)

Tree Save Area

Redeveloped Site Specifics

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Pre-Project (acres) Redevelopment (acres) Tree Save 0.24 Additional Vegetated Area 0.60 0.07 Total Pervious Area 0.60 0.31 Impervious Area 0.47 0.76 Site Area 1.07 1.07

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Stormwater Development Requirements

• Provide onsite detention to reduce downstream

erosion and flooding impacts. This was accomplished by installing an underground detention system.

• Pay mitigation fee for water quality impact at rate of

$60,000 per acre of Built Upon Area (BUA). This site paid $44,340.

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Task Force Questions

• Are current stormwater ordinances working to

stop degradation?

• What are the impacts to the floodplain?

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How The Current Ordinance Improves the Watershed Through Redevelopment

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Redevelopment Requirements:

• Detention is

provided to slowly release runoff to reduce stream erosion

• Detention is

provided on-site to reduce downstream storm drainage system burden

• Detention is

provided on-site to reduce downstream street flooding

0.5 1 1.5 2 2.5 3 3.5 4 4.5

Stream Erosion Flow Storm Drainage System Flow Street Flooding Flow

Stream Protection and Flood Reduction

Pre-Project Redevelopment

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How The Current Ordinance Improves the Watershed Through Redevelopment

37 Undeveloped Pre-Project Redevelopment

Hydrograph for Stream Erosion Flow

How The Current Ordinance Improves the Watershed Through Redevelopment

38 Undeveloped Pre-Project Redevelopment

Hydrograph for Storm Drainage System Flow

Redevelopment Case Study Hendrick Autohaus