EVALUATING STORMWATER SOLUTIONS IN OHIO PREPARING STORMWATER SYSTEMS FOR CLIMATE CHANGE MONROE, MI OCTOBER 10, 2013

Low Impact Development:

A site design approach that attempts to maintain pre-development runoff patterns.

1)Consider site features, not just zoning, during development.

2)Link stormwater management to landscaping.

Result: Lower infrastructure costs & innovative sites.

How did we get here? •Chagrin River Watershed Partners

• Model regulations for stormwater management • LID demonstration & research

•Old Woman Creek NERR • Stormwater design and performance training • Assessment of science and information needs

•ODNR Division of Soil and Water Resources • LID modeling - runoff reduction can exceed

50%

•Lack of widespread LID adoption • Technical and social barriers exist

NERRS Science Collaborative • NOAA-National Estuarine Research Reserve System funds administered by

the University of New Hampshire

• Research addressing local coastal management problems

• Researchers and intended users work together

• Applied for funding in 2010, $821K, 3 year grant awarded in November 2011 to project team led by Chagrin River Watershed Partner, Inc.

Evaluating Stormwater Solutions Project

• Quantify the runoff reduction performance of low impact development (LID) stormwater systems under current and projected future climate conditions and develop science-based design and policy tools that reduce barriers to effective stormwater management.

• 3 year project funded by NERRS Science Collaborative

• Led by Chagrin River Watershed Partners, Inc. with Old Woman Creek NERR with regional partners.

• Guided by input of stormwater planners, designers, utilities, and regulators

Project Components

Monitoring Acquire BMP hydrology data to populate models

Modeling Characterize BMP hydrologic performance under current and projected future precipitation patterns

Tools and Guidance Case studies, model codes, revised design

standards, credit recommendations

Design LID demonstration projects

Monitoring Sites

Orange Village Community Center

Permeable Pavers & Bioretention Cell

Pepper Pike City Hall

Permeable Pavers & Bioretention Cell

Willoughby Hills Community Center

Permeable Pavers

Holden Arboretum Bioretention Cells

Perkins Township Administration Building

Pervious Concrete

Old Woman Creek NERR Originally Planned as

Porous Asphalt

Monitoring Overview • Overall Goal: Quantify performance of LID infrastructure

on poorly draining soils of Erie County and the Chagrin River Watershed • Met with and provided suggestions to local design engineers to

ensure that practices were ‘monitorable’ • Pre-installation soil testing completed at each site to determine

expected infiltration rates • Weather stations installed to continuously quantify weather

parameters (rainfall, temperature, RH, etc.) • Weirs and pressure transducers to monitor peak flow rates and flow

volumes from each practice • Soil moisture sensors, temperature sensors, and conductivity

meters also deployed • Monitoring wells in each practice to determine drawdown rates

Pre-Construction Infiltration Testing

Site Mapped Soil Subgrade Soil Texture

SW Calculator Estimate

Measured Kfs

(in/hr)

Perkins Twp Admin Bennington Silty Clay

Loam 0.02 0.01, 0.01, 0.04, 0.05

Old Woman Creek Delray Silty Clay 0.01 0, 0, 0.003, 0.004

Holden Arboretum

Platea (BRC1) Pierpont (BRC2)

Silty Clay Loam 0.02 BRC1 - 0.02, 0.02

BRC2 - 0.02, 0.08

Orange Village Wadsworth Fill - 0.01, 0.03, 0.05, 0.06, 0.72, 1.54

Pepper Pike Mahoning Silty Clay Loam 0.02 0.01, 0.01, 0.02, 0.04

Willoughby Hills Mahoning Fill - PP1 – 0.01, 0.05

PP2 – 0, 0.01, 0.03, 0.06

Monitoring Site Infiltration Summary

Monitoring Device Installation

Monitoring Installation Continued

Hydrologic Monitoring Hydrologic + Water Quality Monitoring

Perkins Township Holden Arboretum

Orange Village Pepper Pike

Old Woman Creek Willoughby Hills

Quantifying Exfiltration at Perkins Township (Pervious Concrete)

Drawdown Rate Comparison • Monitored inter-event drawdown/exfiltration rate

during 35 inter-event periods

• Two pre-construction single ring infiltrometer tests yielded results of 0.01 in/hr.

• Average measured drawdown rate was 0.016 in/hr with a standard deviation of 0.005 in/hr.

• This suggests that single ring infiltrometer tests are accurate the purposes of permeable pavement design

Volume Reduction – Perkins Township • Total of 3200 ft3 exfiltrated thus far • Equates to 9.7% volume reduction due to

exfiltration • This is quite impressive, given 6.23:1 hydraulic

loading ratio

Peak Flow Rate Comparison at Pepper Pike (PICP)

0.00.10.20.30.40.50.60.70.8

1 2 3 4 5 6

Peak

Flo

w R

ate

(cfs

)

Storm Event Number

Measured Peak Flow Predicted Peak Flow

Monitoring Summary • At six research sites, quantify performance of:

• Four permeable interlocking concrete paver applications • One porous concrete application • Three bioretention cells • One grassed swale

• Use these data to feed stormwater models to predict performance of “design tweaks” for various green BMPs • EPA SWMM • DrainMOD

Modeling Objectives • Appropriately Credit LID BMPs for Volume Reduction and Peak Discharge Attenuation

• Believable/Defensible Models of LID BMP Hydrology • For Ohio standards, and site and climate conditions • Sensitivity analysis • Where data available, calibrate/validate

• Climate Change Impacts on Stormwater System Performance

• Tweak BMP Design Specifications Where Needed • Develop Design and Accounting Guidance/Tools Consistent with Specs, Research Results, Models

Modeled BMPs 1. Soil Quality Preservation/Renovation 2. Vegetated Filter Strip (Impervious Area Disconnection) 3. Vegetated Swale 4. Bioretention (incl. Dry Swales and Tree Planters) 5. Infiltration Trench 6. Underground Retention/Detention 7. Pervious Pavement 8. Dry Detention Basin 9. Green Roofs 10. Wet Detention Pond (Reference)

Modeling Flow Chart 1-ac

Undeveloped

Agriculture Pasture Forest

Development

0.5-ac imp 0.5-ac grass

𝐴𝐴𝐴𝐴𝐵𝐵𝐵𝐴𝐴𝐴𝐴𝐷𝐷

2% 5% 10% 1% 25%

B C D A

B C D A

P depth 0.25-in 0.50-in 0.75-in 1.00-in 1.25-in 1.50-in 2.00-in 2.50-in 3.00-in 3.50-in

Vary BMP parameters for each combination of soil type & BMP size

LEGEND Un-developed

Developed

Absolute Performance Graphs

Data Management & Interpretation

6 12 18 24 48 LS LS/SL SL 18 / 3 21 / 6 24 / 12 30 / 180.250.5

0.751

1.251.52

2.53

3.5

HSG

Even

t Size

(in)

BMPA /WA

Surface Ponding Depth (in)

Soil Thickness (in)

Soil Type Storage Height / Underdrain

Offset (in)

>95%> 75%; < 95%> 50%; < 75%> 25%; < 50%

> 5%; < 25%< 5%

Flow ReductionsLEGEND

Underground Storage: B & C Soils Peak Flow and Volume Reductions

Data Needs for Climate Scenario Analysis • Need guidance for developing climatic data sets to represent projected future conditions (e.g. 2035 or 2050) to support stormwater modeling • Precipitation – event-based and time series

(continuous) projections • Temperature, humidity, solar radiation and wind speed

to model evapotranspiration

Scale • What is the smallest resolution for climate projections?

• Can downscaling (statistical, dynamical, or other methods) be used to achieve a 0.1 – 1 sq. km resolution?

Design event projections • What is projected for the frequency, depth, or intensity of larger rainfall events?

• What are predictions for rainfall distribution for future extreme events? Are commonly used rainfall distributions (e.g., SCS Type II distribution) still valid?

• What will the “1-yr” or “100-yr” event look like in 2035 or 2050?

Projected cumulative distribution of precipitation events • Will the 90th percentile event increase? • Will the entire distribution of events skew toward larger or smaller events? If so, how much?

• Will there be a change to the length of the inter-event period?

• Will there be seasonal changes in precipitation?

Continuous Simulation • Is there enough information on cumulative distribution of precipitation events or design event projections that historic precipitation data records can be modified to project a year of continuous precipitation data at some future date?

• Is there enough information to project evapotranspiration in 2035 or 2050?

Project Contacts Amy Brennan – Project Lead abrennan@crwp.org (440) 975-3780

Heather Elmer – Collaboration Lead heather.elmer@dnr.state.oh.us (419) 433-4601

Jay Dorsey – Applied Science Investigator jay.dorsey@dnr.state.oh.us (614) 65-6647

Breann Hohman and Crystal Dymond bhohman or cdymond @eriecounty.oh.gov (419) 626-5211

Ona Ferguson oferguson@cbuilding.org (617) 844-1127