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Subtitle goes hereAmes Post Construction Ordinance

Eric Cowles, PECity of Ames

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Iowa DNR Storm Water Permit

“An ordinance shall be adopted or amended as needed and enforced which will address the control of runoff from building activities after construction has been completed. The ordinance shall require water

quality and quantity components be considered in the design of new construction and implemented when practical. The statement shall promote the use of storm water detention and retention, grass swales,

bioretention swales, riparian buffers and proper operation and maintenance of these facilities.”

MS4 Permit

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Public Input• Storm Water Advisory Committee

Tom Sauer, USDA Soil Scientist

Charlie Kuester, Planner, Ames

Steve Mayberry, ISU MS4 Leanne Harter, Planner, Story Co.

Chuck Winkleblack, Developer

Kurt Friedrich, Developer

Scott Renaud, FOX Engineering

Nathan Easter, Bolton & Menk

Jim Colbert, ISU Biologist

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Past Requirements

“Storm water management design shall include grading, facilities, improvements, or some combination thereof, which results in no

increase in the rate of runoff when compared to the undeveloped condition in the area to be

developed.”

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Past Requirements

“The rainfall frequencies that shall be incorporated in the design of the stormwater management system shall include the 5 year, 10 year, 50 year, and 100 year design storm

events.”

Did not address storm water quality and stream channel protection

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Post Construction Ordinance

Goals:• Utilize a combination of BMPs, aka treatment train• Minimize increases in storm water runoff, • Minimize non-point source pollution, and• Minimize mass grading

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Post Construction Ordinance

Applies to:

New development and redevelopment disturbing 1 acre or more of land and to any development disturbing < 1 acre if impervious cover >10,000 square feet

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Post Construction Ordinance

Exemptions:

Any Ag Activity

Additions/Modification to Single Family Lots

Anything within 1,000 ft of Ames Well Fields

DNR Requirements?

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Procedures/Requirements

• A storm water management plan prepared by PE or LA with site plan or preliminary plat

• Graphic inventory of existing natural resources• Including hydric soils (wetland soils) and

landscape features to be protected

• Adopts Iowa SWM Manual as Design Guide

• Requires Unified Sizing Criteria• WQv, CPv, Overbank/Flood Protection

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Procedures/Requirements

• Topographic watershed map• LiDAR or City aerial topo

• Design calculations for proposed BMPs

• Post Construction Design runoff to meet “meadow in good condition”• No Credit for existing impervious

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Procedures/Requirements

• Use Low Impact Development (LID) features: • Preserve open space and natural areas, • Re-establish prairies • Minimize impervious cover• Capture, store, reuse runoff.

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Procedures/RequirementsSoil Management Plan

• General soils information (NRCS website) • Borings as Needed • Identifies Ground Water• Identify “Soil Health”/Needs for

Amendments• Soils Scientist?• Guides placement of BMPs

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Procedures/Requirements

Stream Buffers

• > 3rd Order – Requires Assesment

• 1st and 2nd Order – 100’ Each Side

• Intermittent Streams – 50’ Each Side

• Waterways with Drainage Area > 50 Acres• 30’ Each Side

• Waterways with Drainage Area > 50 Acres• 20’ Each Side

• Maintained with Natives

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Procedures/Requirements

Maintenance, Repair and Landscaping Plan• Addresses routine and long-term maintenance of:

• BMP’s• Vegetation• Responsibilities• Review Schedule of the Plan

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Procedures/Requirements

Proof of Recorded Maintenance Easements for Access to Storm Water BMPs Recorded with the SWM Final Plan

Dedicate Drainage Easements to City

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Procedures/Requirements

All Water Quality Maintenance• Responsibility of Property Owners

Exception:• City Responsible for Large (Flood) Water Quality

Features (i.e. detention basins)• Dredging, Outlet Structures

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For Lots Impacted by Storm Water BMPs

Builder to Provide Elevation Certificate• Lowest Opening/Foundations 3’ Above 100 Year

• Certified by LS, PE, LA

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Waivers

Granted by Municipal Engineer• Written Request

• Doesn’t Impair Ordinance Objectives

• Establish Alternative On-Site SWM

• Establish Alternative Off-Site SWM• Equal or Better than On-Site

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Waivers

• Also Establish No Downstream…• Deterioration of Structures

• Degradation of Bio Functions or Habitat

• Accelerated Erosion or Siltation

• Increase Threat of Flood Damage to Public Health, Life or Property

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Performance Bond

Financial Security with Final Plat or Site PlanIn the amount of the total estimated cost for the construction of the BMPs

Receive as-built plans from owner, City conduct final inspection of site, and then release financial security

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Maintenance

• Inspections 1/Year by Owner or Rep• Keep Inspection Records for at Least 3 Years• Make Inspection Records Available to City

Upon Request

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Outreach

• Technical Assistance Documents• Guide Through Ordinance• Check List

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Today

• Timing of Submittals• Redevelopment• Existing Regional Detention• New Construction

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Challenges

• New Apartment Complex• Next to creek• In flood plain/flood way

• Meeting with Developer’s Engineer

• Waivers

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Challenges

• Redevelopment Site• Next to City Well

• No Perforated/Open Joint Pipe Allowed• Meeting with Development Engineer and Owner

• Waivers

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