Innovative Stormwater Solutions for Ohio

Case Studies of LIDImplementation and Performance

1

Project Description

Project OverviewMonitoringModelingTools & Guidance Project Sites

Case Studies Perkins TownshipWilloughby HillsOrange VillageHolden Arboretum

Lessons Learned

BMP Maintenance

Collaborative Process

LID System SchematicsPermeable PavementsBioretention

Acknowledgements

This report is designed to be a technical and educational resource for stormwater professionals and others seeking to learn about the performance of low impact development (LID) stormwater technologies in Ohio. It synthesizes key information about design, construction, and monitoring of LID stormwater practices at projects sites from the first two years of the Stormwater Solutions for Ohio collaborative research project. Data used to create this report was collected from site observations, project documents, and interviews with stormwater professionals.

There are seven sections in the report: project description, project overview, case studies, lessons learned, BMP maintenance, collaborative process and LID system schematics. Each section contains either overall project information or site-specific design, construction, and monitoring information.

This report was prepared by Will Brown, a graduate student project intern from the University of New Hampshire, with the support and guidance of the Stormwater Solutions for Ohio project team. Funding from the NERRS Science Collaborative and the Friends of Old Woman Creek supported this research. Readers are encouraged to provide feedback to the project team on information found in this document to help guide the development of other tools and guidance. Contact information can be found at the end of this report.

Why is stormwater research important?Impervious surfaces associated with historic and new development increase the volume and rate at which stormwater runoff reaches our streams and lakes. Increased runoff volumes result in erosion, causing streambed downcutting, streambank erosion, and increased frequency and extent of streamside flooding. In communities with aging sewer infrastructure, increased runoff volume results in combined sewer overflows (CSOs) that contaminate local rivers and streams with raw sewage. Runoff flushes pollutants and nutrients into water bodies, impairs water quality, degrades habitats, and heightens the risk of waterborne disease. All of these negative impacts are expected to intensify if the frequency and severity of storm events increase in Ohio as predicted. As the built environment expands, the area of impervious surfaces in Ohio’s communities will increase and exacerbate the negative impacts of stormwater runoff. Low impact stormwater technologies can help mitigate some of these problems by mimicking natural hydrologic functions in stormwater system designs. Because many stormwater professionals are still new to these technologies, there is a need for additional research, development, and implementation of these practices.

About this ReportContents

Collaborative Learning Group (CLG)

2

This project is developing science-based tools to promote the implementation of LID stormwater control measures (SCMs) that reduce the impacts of stormwater runoff on Ohio’s coastal communities and Lake Erie. The project team includes the Chagrin River Watershed Partners (CRWP), Old Woman Creek National Estuarine Research Reserve (OWC NERR), Ohio Department of Natural Resources Division of Soil and Water Resources (ODNR-DSWR), Erie Soil and Water Conservation District (Erie SWCD), the Consensus Building Institute (CBI), and North Carolina State University (NCSU). The project is funded by the National Estuarine Research Reserve System Science Collaborative (NERRS SC).

Design Stormwater Retrofit Projects:Funding and technical assistance for storm-water control measures at Holden Arbore-tum, Orange Village, Pepper Pike, Ursuline College, Willoughby Hills, Perkins Township and Old Woman Creek

The project team is working with stormwater professionals in northern Ohio to generate credible and locally verified information about the performance of innovative LID stormwater systems. A collaborative learning approach is being used to engage a group of interested experts. The collaborative learning group (CLG) comprised of stormwater engineers, regulators, stormwater utility managers, and watershed organizations has provided iterative guidance and feedback to the project team on the design, construction, and monitoring of six SCM sites. The collaborative learning process has also enabled group members to share a broad range of knowledge, concerns, and ideas for addressing complex stormwater challenges in northern Ohio.

Monitoring data is being collected at each site to determine hydrologic performance of SCMs and validate models to predict SCM effectiveness with projected climate scenarios. Information generated from this project will be used to develop credits and incentives that promote the implementation of the most effective stormwater systems.

Monitor amount of runoff from sites

Model performance of Stormwater Control Measures: Characterize stormwater control measures’ hydrologic performance under current and projected future precipitation patterns

Develop Tools & Guidance: Case studies, model codes, revised design standards, credit recommendations

Stormwater Solutions for Ohio

Project Description

3

Why monitor stormwater control measures?Monitoring stormwater practices allows the project team to evaluate SCM performance by documenting site-specific hydrologic, atmospheric, and water quality performance. All SCMs designed for this project were monitorable and optimized for hydrologic performance so that stormwater professionals can determine how well these practices function under Ohio conditions.

How are stormwater control measures designed for monitoring?ODNR characterized each site during the design and evaluation process to evaluate infiltration of surface and subgrade soils, SCM drainage area, land cover types, and local climate. Information from site evaluations influenced SCM design parameters (i.e. sizing, aspect, location, etc.) and the types of equipment used for monitoring. Monitoring contractors and the project team collaborated with design engineers to ensure each site plan would accommodate the installation of monitoring equipment and allow performance results to be transferable and scalable to similar LID installations. Monitoring equipment selected for each site had to be durable, reasonably priced, and capable of recording data on a sufficiently short interval (2 minutes) to produce accurate runoff hydrographs. A primary goal was to collect discharge data from every rainfall and runoff event up to and exceeding a 2-3 inch depth. The ability to record nearly all storm events during the monitoring period ensures the data will provide information about SCM performance under a variety of conditions.

What monitoring equipment was used to measure hydrology?NCSU installed monitoring equipment during or shortly after construction of SCMs. This section discusses the primary types of hydrologic monitoring equipment used at every project site. More specific details about the installation differences between sites are discussed in the individual case studies.

Weather stations at each project site provide reliable local data about precipitation, wind speed and direction, solar radiation, relative humidity, and ambient air temperature. To gather this data, each weather station is equipped with a tipping bucket rain gauge, anemometer, wind direction sensor, pyronometer, and temperature/humidity sensor. Ultimately, precipitation data and other site data will be used to calculate the runoff inputs to each SCM. Calculated runoff inputs are compared to measured outflow data to determine hydrologic performance for each storm event, except for with the Orange Village bioretention cell that has direct inflow measurement.

V-notch weirs and pressure transducers are being used to measure outflow rates. V-notch weirs were chosen because they give the best low flow accuracy. Additionally, pressure transducers are calibrated after every data download to prevent equipment drift (and decrease error). Post-processing is required to translate depth measurements to flow rates using standard weir equations. Water table wells equipped with pressure transducers allow for continuous depth measurement of subsurface ponding in each SCM to ascertain depth of the internal water storage layer in the aggregate as a function of time and to increase understanding of infiltration at the site. Select project sites are also being monitored for water quality, clogging rates of permeable paver installations, and soil moisture variations in bioretention cells. Temperature measurements are being made at all SCMs to determine their ability to protect coldwater streams that must maintain cold-water temperature regimes to support fish and macroinvertebrate communities. In addition, conductivity of outflow is being measured at Perkins Township and Willoughby Hills SCMs.

Each SCM needed to be hydrologically isolated from other SCMs in their treatment train to determine individual performance. At least 3 inches of fall from a piped outlet is needed to measure outflow without backflow effects, although six inches is preferred. The cost of monitoring equipment ranged from $6,000-$10,000 per site with NCSU contractors fabricating water table wells and weir boxes to reduce overall costs. At the more expensive sites, the team monitored multiple SCMs and installed equipment to support additional studies. Inflow to LID SCMs is generally as sheet flow making it difficult to accurately measure. Inflow at project sites will be estimated based on drainage area characterization and rainfall. Inflow estimates are fairly accurate if the contributing drainage area is impervious.

Monitoring

Hyrdologic monitoring at Holden Arboretum

V-notch weirs at Orange Village

Project Overview

4

How will information generated by this project be used?The goal is to develop credits for LID stormwater SCMs and promote implementation according to their predicted performance. Characterization and validation of SCM hydrology through monitoring and modeling will inform the development of proper crediting for runoff volume reductions and peak flow mitigation provided by LID stormwater practices. CRWP and others will update model zoning codes for stormwater management, conservation development, riparian and wetland setbacks, off street parking, and flood damage reduction to improve community stormwater regulations in the state. Zoning code updates will be based on research results and lessons learned. Technical assistance for adoption and implementation of community stormwater codes will be provided by project partners. The Ohio stormwater community requested hydrologic performance information for SCMs subjected to site and climatic conditions in Ohio to ground truth the effectiveness of bioretention and permeable pavement practices. Training sessions on design, maintenance, construction, and monitoring of stormwater SCMs will be developed to increase the ability of engineers, contractors, construction site inspectors, and community officials to effectively design, construct, and maintain these systems. The project team also hopes to build stormwater research capacity by hosting additional working sessions with interested universities, agencies, and other organizations.

Tools & Guidance

Modeling How will monitoring data be used?Monitoring data is being used to calibrate and validate stormwater models (SWMM and DRAINMOD) to evaluate the hydrologic performance of bioretention and different types of pervious pavement practices. These models will determine how design parameters and physical factors affect SCM performance. They will quantify and compare runoff reduction, water quality volume treatment, peak discharge control, and flow duration across SCMs to determine how design parameters and varying physical factors impact performance. Projected climate scenarios will be used to assess how these systems may perform in the future.

Is winter monitoring viable in Northern Ohio?In winter 2013-2014, the project team evaluated the viability of monitoring during the winter season to determine if the benefits exceed the risks and costs associated with data collection during the winter months. Winter monitoring was attempted at the request of CLG members interested in understanding how SCMs process rain or snowmelt when the ground is frozen. In January and February 2014, snow was on the ground constantly, with frequent plowing and salting of parking lots. Other challenges and difficulties with monitoring during the Ohio winter included:

• Difficulty accessing equipment in catch basins because of piles of snow and frozen manhole covers.• Equipment had to be extremely durable and needed to be moved to a heated location to make an electrical connection and download data.• Water quality monitoring was not possible because of the potential for snowplows to damage tubing. To facilitate winter water quality monitoring, tubing must be fed through the side of catch basins rather than run over the parking lot surface.• Hydrologic monitoring in catch basins or at surface flow points becomes problematic during extended periods of below freezing temperatures because ice forms behind weirs. • Snowplowing can change the size of the monitored watershed. To address this, plow drivers must be educated or a defined inflow monitoring point must be created. This can be difficult to achieve for practices (e.g. permeable pavement) where no elevation drop or defined inflow location exists.

Top Right: Water spills over a weir at Willoughby HillsTop Left: Water table well at Holden ArboretumBottom Left: Weather station at Holden ArboretumBottom Right: Pressure transducers frozen inside a weir box at Willoughby Hills

BMP construction workshop at Perkins Township

5

Project Sites

!m

!m

Vermilion River

Huro

nRi

ver

Erie

Huron

Lorain

Pipe Creek

Old Woman Creek

Perkins Township Administration Building Pervious Concrete Parking Lot

Old Woman Creek National Estuarine Research Reserve

Pervious Pavers and Rainwater Harvesting

L a k e E r i e

´0 1 2 3 4Miles

Old Woman Creek & Pipe Creek WatershedsMonitoring sites were selected based on the following collaboratively developed criteria:

• Priority SCMs for research• Location in targeted watersheds• Education and training suitability• Maintenance and monitoring accessibility• Quality of downstream water resources

Four project sites (highlighted in green) are featured in case studies found in this report, including:

• Perkins Township Administration Building• Willoughby Hills Community Center• Holden Arboretum• Orange Village Community Center

7 6

Chagrin River Watershed

!m

!m

!m

!m

Lake

Geauga

Cuyahoga

Portage

Summit

Aurora Branch

Chagrin RiverMain Branch Chagrin River

Upper Main Branch

East Branch Chagrin River

Aurora Branch

Silver Creek

Lower Main Branch

Headwaters Aurora Branch

Cuya

hoga

Riv

er

Cuyahoga River

Holden Arboretum Visitor Center Parking Lot

Bioretention CellsWilloughby Hills

Community Center Permeable Paver Parking Lot

Ursuline College Bioretention Cells

Orange VillageCommunity Center

Permeable Paver Parking Lot& Bioretention Cell

L a k e E r i e

´0 2 4 6 81Miles

7

PerkinsTownship About Perkins Township

The Perkins Township Trustees incorporated innovative stormwater practices into their redevelopment design plans for the relocation of the Perkins Township administrative offices to an abandoned commercial plaza. This project drains to the Pipe Creek, a 32 square mile mixed urban and agricultural watershed classified as a warm water habitat stream that directly flows into East Sandusky Bay. The Township applied for and received an Ohio EPA Surface Water Improvement Fund (SWIF) grant to remove portions of the existing parking lot and install LID SCMs. NERRS SC project funds subsidized a portion of the design costs and provided technical support on modifying the design of the pervious concrete parking areas to allow monitoring. This project provided opportunities for design input from stormwater professionals and hydrologic monitoring to determine the performance of two different design cross sections of permeable concrete.

Site EvaluationSoil permeability in much of Ohio is very poor, and the soils at Perkin Township are no exception. Infiltration tests performed by ODNR-DSWR found an infiltration rate of 0.05 inches per hour. The designs were developed by a CLG member with technical assistance from the project team to ensure the size, depth, and location of the SCMs to appropriate address the poor soil permeability at this site. The onsite soils were Bennington silty clay loam. Since site conditions are similar to those at other locations in northern Ohio, performance data from this site should be a good predictor for SCM performance in the region.

DesignDesigning for MonitoringDesign engineers collaborated to ensure that the installed LID practices would be monitorable. Invert elevations of pipes were changed to fit monitoring structures. One difficulty was encountered at the main monitoring catch basin on the site: while the catch basin was 3 ft by 3 ft square, the access-way was only 24 inches

in diameter, causing field changes to be made to monitoring structures. NCSU contractors installed water table wells in the pervious concrete areas in order to monitor water levels in the subbase. Additionally, a location free from tree overhang or other obstructions was identified for placement of the weather station.

Support & GuidanceThe goal was to design the LID practices to promote infiltration, detain additional water beyond the water quality volume, and reduce outflow volume and peak discharge rates to the maximum practical extent given the tight underlying soils. The subgrades beneath the pervious concrete parking areas were level to allow water to pond evenly in the 15 inch subbase. The design of the west pervious concrete application included a six inch sump below the underdrain to create storage to capture and exfiltrate stormwater. Whereas, the east pervious concrete application was not designed to include a sump. Outflow from the west section includes runoff from the downspouts that drain the roof of the administration building.

Challenges Incorporating existing drainage infrastructure and addressing on site physical conditions presented significant design challenges at this site. A proposed bioretention cell was eliminated because the required depth for surface ponding and soil media could not be achieved given the lack of elevation change between the practice and the existing storm sewer. Similarly, the drainage pipes for the pervious concrete had very little slope, which increased concerns about tailwater effects in the catch basins during monitoring and necessitated the addition of multiple clean-outs for the underdrains in the subbase.

Subgrade soils have poor infiltration rates and the ratio of the catchment area to SCM infiltrative surface is 6.23:1 for the west application and 1.95:1 for the east application. The higher than recommended 2:1 ratio (Ohio Rainwater & Land Development manual) on the

Quick FactsInstalled BMPs with Area:Pervious Concrete East- 8,424 ft²Pervious Concrete West- 2,592 ft²

Catchment Area & Loading Ratio:East Application- .57 Acre (1.95:1)West Application- .43 Acre (6.23:1)

Installation Costs:Pervious Concrete- $8.08/ ft²

Recommended Maintenance:Gently Power Wash Post-ConstructionAnnual Vacuum SweepingSteel or Hard Rubber Edged Snow Plow

Installation Dates:Construction- Summer/Fall 2012Monitoring- April 2013

west basin was considered acceptable since much of the contributing drainage is cleaner roof top water. Establishing objectives and desired outcomes early in the process was critical to successfully addressing design challenges.

ConstructionOverview RMH Concrete was hired as the certified pervious concrete installer for this project. For the North and East parking areas, a pervious concrete surface was poured over a 9 inch subbase of #57 stone topped with a 2 inch choker course of #8 stone. Drive aisles were standard concrete surface with no reservoir and 4” underdrains were place along the face of the curb line on the fabric at the soil interface. The subgrade was not scarified before placement of fabric and stone. For the West parking area, pervious concrete parking spaces and standard concrete aisles were placed over 13 inches of #57 and 2 inches of #8 stone creating a reservoir under the entire parking lot. 4” underdrains were placed at 6 inches above the soil interface to create a “sump” that has to infiltrate into underlying soils. This area also receives all roof water (~ 13,000 ft² of roof area) from the building through subsurface tile that outlets into the stone base at the south end of this parking area. This area was scarified prior to placement of fabric and stone.

The washed limestone aggregate was compacted with machine traffic during placement of the stone. Further compaction was unnecessary because of the absence of fines that are present in

traditional pavement base material.Pervious concrete was poured into forms and rolled by hand to achieve the desired grade and structural density. Immediately after grading and rolling the pervious concrete was covered with plastic to facilitate proper curing and protect it from rapid drying. Pervious concrete was used exclusively for the parking stalls and conventional concrete was poured for drive lanes that were crowned to shed water into the parking stalls for treatment.

ChallengesPervious concrete must be covered with plastic sheeting within 10-12 minutes of pouring and must stay completely covered for a week to facilitate proper curing. The construction crew prevented drying during the initial installation by using sprayers and rollers to moisten and mold the surface. Finished sections were quickly covered with plastic to prevent rapid drying. However, the crew did have some difficulty working with the concrete in areas adjacent to curbs, and ultimately weather became the most significant challenge. Strong winds removed plastic covering and exposed a section of the curing concrete during the initial 10 day curing process that eventually resulted in surface raveling. The structural integrity of this pervious concrete section appears to be sound, but the aesthetics in the affected areas are lacking when compared to the rest of the installation.

Site stabilization was another challenge. Some clogging occurred on a small section of pervious concrete that received stormwater runoff from an un-stabilized adjacent area. Proper timing and sequencing of site stabilization during construction can avoid such problems.

MonitoringEquipment & MethodsStormwater engineers from North Carolina State University fabricated and installed two V-notch weir boxes in separate catch basins to monitor outflow from the North-East and West permeable pavement parking areas. Each weir box contains pressure transducers that measure temperature and flow depth. Conductivity sensors were also deployed to monitor spikes in conductivity during runoff (typically caused by deicing salt). A water table well was installed in the west application to measure water levels in the subbase.

Preliminary ResultsInitial monitoring results indicate that five-minute peak flow intensity was approximately 90% lower than that predicted for a conventional parking lot. Drawdown rates in the pervious concrete have been very similar to what was predicted by infiltration testing and the Saxton soil water calculator, which validates the use of these methods (K.E. Saxton et al., 1986). A 9.7% volume reduction has been achieved from exfiltration thus far, an impressive result given the soil type and high hydraulic loading ratio.

Monitoring data show that even with the very low infiltration rates at the site, some hydrologic mitigation (through infiltration) is occurring. Data are being fed into the drainage model DRAINMOD for long-term simulations of performance of the design cross-sections at this site. This will allow determination of current and future performance (under various climate change scenarios) of these SCMs.

8

9

Orange Village About Orange Village

In 2009, Orange Village purchased a property adjacent to their Village Hall and Fire Department. The existing buildings were renovated for use as offices for the Service Department, a community center, and a transfer facility for electronic and hazardous household waste. Orange Village’s proactive approach to stormwater management on this redevelopment property was funded through an Ohio EPA SWIF grant, with design assistance from the NERRS SC project. This site drains to Willey Creek, a coldwater habitat tributary to the Chagrin River. A cul-de-sac style driveway incorporated an extensive permeable interlocking concrete paver (PICP) installation. A small swale conveys roof runoff to a bioretention cell. The hydrologic performance of the PICP installation and bioretention cell are beingmonitored inside a large circular vault.

Site EvaluationThe existing conditions were typical of other redevelopment properties in northern Ohio with highly disturbed soils, primarily consisting of fill from prior construction activity on-site mixed with or covering the native Wadsworth Silt Loam soil. This made evaluation of drainage and infiltrative capacity difficult. The first series of infiltration tests yielded very poor results (0.01, 0.00, 0.01 in/hr). Standing water in two deeper test pits likely reflected a significant amount of rainfall (> 5 inches) in the week prior to testing. A second series of tests performed during excavation for the permeable pavement system in July (about 7 months later) produced highly variable results ranging from 0.01 to 1.54 in/hr, and no standing water was present in the test pits. The stark difference between testing results indicated that the fill material and native soils have different infiltration rates, and that preferential pathways of drainage are likely.

DesignOverviewOrange Village officials wanted the proposed stormwater SCMs to be aesthetically pleasing, and provide drainage and water quality benefits.

Also, the design needed to be practical for the intended uses of the property for service department offices and a community center. Village officials also wanted the design to serve as a model for local developers about stormwater SCMs installed at a commercial scale.

The final design included a large permeable paver cul-de-sac and driveway (9,490 ft²) and a bioretention cell (520 ft²). Both SCM designs were integrated into the landscape so they were visually appealing and did not interfere with existing trees and plantings. All underdrains tied into one large precast circular vault accessible by a single manhole, which required creative weirbox construction for monitoring. Water table monitoring wells were specified and positioned out of the drive lane to allow for easier access, but were mistakenly not installed during construction.

ChallengesThe surprising infiltration results and presence of groundwater during infiltration testing raised concerns about an elevated groundwater table and onsite drainage. In response, two curtain drains were incorporated into the design approximately 2 feet below the bottom of the pervious pavement subgrade to dewater the groundwater table on site, if needed. However, monitoring has shown minimal flow from these drains, thus the high water table during the infiltration testing was likely due to heavy rain (over 5 inches) prior to testing.

The slope of the site raised concerns about uneven ponding in the permeable paver subbase. To address this challenge, the site was extensively re-graded and the subgrade of the paver area was sloped slightly near the building to shed water away from the foundation.

The cul-de-sac design was aesthetically pleasing, but required a lot of manual work for contractors installing the pavers since nearly every paver next to a curb had to be hand cut. Designing permeable paver applications with square, rather than curved, edges may be more cost effective due to labor costs of completing curb cuts.

Quick FactsInstalled BMPs with Area:Permeable Paver Drive- 9,490 ft²Bioretention- 520 ft²

Catchment Area & Loading Ratio:Permeable Pavers- Direct Rainfall Only (1:1)Bioretention- 20,740 ft² (With Roof Drainage)

Installation Costs:Permeable Pavers- $21.13 ft² (Average Bid)Bioretention- $33.99 ft² (Average Bid)

Recommended Maintenance:Power Washer Post-ConstructionAnnual Vacuum SweepingSteel or Hard Rubber Snow PlowBioretention Cell Landscaping

Installation Dates:Construction- Summer/Fall 2013Monitoring- September 2013

10

ConstructionOverview A general contractor coordinated and completed most of the construction, but the permeable paver and curb installations were performed by specialist subcontractors. The paving installer was ICPI (Interlocking Concrete Pavement Institute) certified and experienced with installing pavers. The first tasks were to remove the existing pavement, and excavate the parking area, drive lane, and bioretention cell. Curtain drains were installed underneath the permeable pavement system to prevent groundwater intrusion from affecting monitoring results and system performance. Next, the permeable paver subbase was installed, and 15-21 inches of #1 and #2 aggregate were used for this purpose. A PICP underdrain was embedded in the subbase, creating a 6 inch sump to promote exfiltration. Next, a six inch base course of #57 stone was installed, but was subsequently removed, temporarily stored nearby, and washed before being re-installed after curb installation. The concrete curbs were installed along the driveway by a subcontractor while a separate crew continued to work on construction of the bioretention cell.

To prepare for paver installation, a 2 inch bedding course of #8 limestone was spread and graded. Next, Eco-Optiloc pavers were mechanically installed using a Probst VM-series “PaverMAX” mechanical paver installation system. The machine was able to lay most of the surface area, but pavers abutting curbs needed to be manually cut to size by the installation crew.

The bioretention cell consisted of a 12 inch recharge layer of #57 stone surrounding an underdrain, 3 inches of #8 stone, 3 inches of clean medium concrete sand, and 30 inches of bioretention soil mix. The soil mix was put together onsite and was 60% sand, 40% topsoil, 8% clay/silt, 2% organics, which is too little sand and likely a higher clay content than recommended (10%) when accounting for the probable composition of topsoil plus 8% clay. This cell incorporated a 3 inch sump beneath the underdrain to promote exfiltration.

Following installation of the bioretention cell, a silt fence was erected to help protect the practice from sedimentation.

ChallengesAn abandoned septic tank was discovered that was not recorded on any site documentation. The tank was first examined to make sure that it was not in current use, and then it was pumped dry and removed.

The silt fence used to protect the bioretention cell failed and a 3 inch layer of sediment settled on the surface of the practice. This was corrected by removing the sediment and re-grading the bioretention area.

Aggregates used for the subbase and filter layers of the permeable pavement did not conform to the design specifications which called for “double washed angular stone”. Instead, rounded (non-angular) unwashed #57 stone was used for the filter layer. This could lead to differential settling, rutting, or other long term performance issues. As construction observers, contractors, and engineers are still learning about installation of permeable pavement systems, materials specified and delivered and construction sequencing should get detailed attention.

A non-standard bioretention soil mix specification was used resulting in a higher clay and lower sand content. The bioretention cell was also constructed with an uneven grade, this error will need be fixed so that water can pond evenly over the infiltrative surface. Due to a construction oversight, two monitoring wells were not installed in the practice.

MonitoringEquipment & MethodsMonitoring equipment was installed in fall 2013. Three v-notch weirs were installed in the precast concrete vault to monitor outflow from the permeable pavement, bioretention cell, and curtain drains. The cylindrical vault and number of weirs in the catch basin required creative weir design, construction, and installation. Weirs were constructed so that they could be installed on the curved walls of the vault. In addition the depth of the vault necessitated a creative solution for accessing monitoring equipment to avoid confined space entry. Long PVC pipes and rope were used to extract pressure transducers for monitoring without entering the vault. Another v-notch weir was used to measure outflow from a drainage swale, which was constructed at the inlet to the bioretention cell.

ChallengesThere have been two main challenges for conducting monitoring at this site. The most difficult challenge has been to compensate for the lack of water table monitoring wells. Estimates of inflow to the permeable pavement SCM are being calculated based on the amount of rain and the surface area of the practice. Estimates should be relatively accurate because there is no run-on to the pavers. It’s unlikely that modeling will be completed for this site without the water well data needed for model calibration.

The other challenge has been very slow leaks in two of the weir boxes. The monitoring team has repaired the leaks by using hydraulic cement to ameliorate any dripping. Data will be corrected for the slow leaks by taking them into account during post-processing analysis.

11

WilloughbyHills

Quick Facts

About Willoughby HillsThe City of Willoughby Hills received an Ohio EPA SWIF grant to treat stormwater runoff from an existing impervious asphalt parking lot at the Community Center and Public Library by installing two PICP applications. The Community Center parking lot discharges stormwater runoff into an unnamed tributary of Gulley Brook that flows into the Chagrin River. One PICP application was quite small and located in the western corner of the parking lot where snow storage occurs. The hydraulic loading ratio for this bay is quite high (6.5:1) and will provide useful information on clogging rates under increased flow and debris from snow storage. The east application at the site has a hydraulic loading ratio around 2:1, consistent with the ODNR Rainwater and Land Development Manual recommendation. Both SCMs have been monitored for hydrology since fall 2013. In the spring of 2014, the site will be monitored for water quality as well.

Site EvaluationThe original design called for installation of both PICP and bioretention. After several redesigns with community input, the City installed two bays of pervious pavers with different run-on ratios in September 2013. ODNR conducted infiltration testing during construction to verify the infiltration rates of soils beneath each parking area. Infiltration rates varied from 0.00-0.06 in/hr and soils appeared to be compacted fill.

DesignDesigning for MonitoringThe two bays of PICP represent two different loading ratios. The west bay has a high loading ratio of 6.5:1, while the east bay has an ODNR recommended ratio of 2:1. The permeable paver underdrains were connected to a single catch basin in each section to facilitate monitoring efforts. An existing catch basin positioned at the edge of the paver area receives flow directly off the impervious asphalt, allowing researchers to collect control samples in order to monitor the difference in water quality between the treated and untreated stormwater.

Support & GuidanceThe hydrologic performance of the permeable paver area was enhanced to include a 6 inch sump achieved with an upturned elbow on the underdrain that increased the internal water storage layer. The decision to use an upturned elbow instead of elevating the underdrain was made because the designer felt it would be easier to construct. Subsequent discussions about the configuration of the upturned elbow hypothesized that it would be easier to clean out an upturned elbow if the configuration also included a straight line access to the underdrain.

The project team recommended that the design include a series of baffles (steps) into the subgrade so that the bottom of each step could be constructed with a level grade. These baffles were constructed of #57 stone covered with geotextile on top of the subbase act as small check dams to maximize the infiltrative surface in a sloped parking lot. The final design also accounted for monitoring considerations and redevelopment plans for a pavilion area immediately adjacent to the parking lot retrofit. To effectively incorporate all these modifications, design engineers had to be adaptive and receptive to feedback.

ConstructionOverview Construction was performed by a single certified contractor without employing any subcontractors. This lessened the potential for miscommunication and simplified construction sequencing. During excavation, the operator scarified the underlying soil using the teeth of the excavator bucket to loosen the soil and reduce compaction of the subgrade, allowing for greater exfiltration post-construction. Next, the underdrains were installed and connected to the existing catch basins. A Tensar BX1200 Geogrid was laid down on subgrade, the water table wells were installed, and the excavated area was filled with a mixture of clean #1 and #2 limestone as the subbase. This layer was graded and a plate compactor was used to interlock the stone. Installation of the concrete curbs followed and was performed by hand to ensure

Installed BMPs with Area:Permeable Paver East Bay- 3,978 ft²Permeable Paver West Bay- 482 ft²

Catchment Area & Loading Ratio:East Bay Catchment- 19,651 ft² (~5:1)West Bay Catchment- 3,595 ft² (~7:1)

Installation Costs:Permeable Paver Retrofit- $13.05/ ft²

Recommended Maintenance:Annual Vacuum SweepRotary Brush SweepSteel or Hard Rubber Edged Snow Plow

Installation Dates:Construction- Summer/Fall 2013Monitoring- September 2013

12

that the curbs were formed correctly and dimensions were in accordance with the design. After curb installation, a 6 inch layer of #57 angular limestone was laid, graded, and interlocked. A 1.5 inch layer of #8 limestone was used next and was graded using a specialized machine. The last phase of the construction was to install the PICP. This step was mostly performed by a Probst VM-series “PaverMAX” mechanical paver installation system to lower the cost and increase the speed of installation. Areas adjacent to curbs had to be cut by hand and fit into place manually. Once all the concrete pavers were placed, then #8 stone was swept onto the paving surface to fill the interstitial spaces between the pavers and prevent any movement of the pavers. Lastly, the site was stabilized and the parking stalls were striped.

ChallengesDuring excavation, the weight of the excavator caused compaction of the soil underneath the permeable paver area, so the soil had to be loosened by the excavator bucket before any base could be laid. Soil compaction or smearing of the soil surface can decrease infiltration if not properly loosened following excavation.

Construction of a pavilion immediately adjacent to the parking area necessitated a change in curb design. The problem was resolved by using red line mark ups on the site plans to avoid additional design costs. The ability of the contractor to adapt to the new design was crucial in this situation, and experience ensured that the installation was performed correctly without additional cost. Installation of the concrete curbs was made even more challenging by weather conditions. A 27 ft. section of curb had to be replaced because it dried too rapidly during the initial curing process and cracked as a result. The failed section of curb was poured on a day that exceeded 100°F. All the curbs were installed by hand because machine installation is not feasible for a parking lot retrofit unless a margin of error is allowed in the site design to account for variation in curb width.

MonitoringEquipment & MethodsMonitoring equipment installation occurred both during and after construction. Water table monitoring wells and time-domain reflectometers (TDRs) were installed during construction, which necessitated coordination between the monitoring team and contractor. The water table wells were installed by the contractor during construction so the wells would extend into the subgrade to monitor ponding depth. The TDRs were installed during construction because they needed to be buried a couple inches deep in the base course of #57 stone. They were positioned along three transects at distances of 1, 3, 5, and 10 feet from the interface between the permeable pavers and the asphalt to measure the progression of clogging across the paver surface. Since clogging may occur more rapidly when there is a higher hydraulic loading ratio, the locations of the three transects all had different loading ratios. Using these measurements, the project team hopes to be able to determine a rate of clogging as a function of the amount of run-on from impervious asphalt. After construction, NCSU researchers fabricated two V-notch weir boxes, and installed them in two separate catch basins to monitor underdrain outflow from each PCIP section.

In spring 2014, water quality will also be monitored in addition to hydrology. A broad crested weir box was installed into a catch basin draining a portion of the impervious asphalt to catch untreated water and act as an experimental control. ISCO 6712 portable samplers will be used to gather flow-proportional water quality samples from the untreated runoff

location, the underdrain of the west PICP application, and the underdrain of the east PICP application. In this way, the project team will be able to characterize the hydrologic characteristics, pollutant concentrations, and pollutant load reduction from this parking lot.

ChallengesPlacement of the TDRs only a couple of inches deep within the layer of #57 angular limestone was a concern because of the pressure of heavy equipment passing over them to lay #8 limestone and pavers. Heavier duty TDRs were ordered that have been successfully used on another project in Kentucky. Cables leading to the sensors on each transect were bundled together for additional protection and durability.

The placement of water quality monitoring boxes was negotiated to minimize aesthetic impacts to the grounds around the community center. This challenge was approached by exploring the community’s interests and working to develop a compromise acceptable to all parties.

Preliminary ResultsDuring the first two months of monitoring, 8 outflow producing events were recorded for the West permeable pavement application at Willoughby Hills. Only three such events were noted at the East application. Two factors probably influenced this: (1) the West application has a much higher hydraulic loading ratio, meaning that more stormwater is forced through a smaller stormwater control measure; this would drive more frequent outflow. (2) the West application is used for disposal of snow, whereas much of the snow on the East application was pushed over the back of curb. Each time

snowmelt occurred, outflow was recorded at the West application, but it often was not observed at the East application. The two largest events (11/17 and 12/22) showed that the East application generally produced greater drainage and larger peak flow rates. These results are related to the greater volume of water and higher flow rate that the East application received during rainfall events.

13

About Holden ArboretumHolden Arboretum staff and project team members designed and constructed two bioretention cells to treat stormwater runoff from the Visitor Center parking lot. This site drains to Pierson Creek, a coldwater habitat tributary to the East Branch of the Chagrin River. The cells receive parking lot runoff from similarly sized watersheds, allowing direct performance comparison between the two cells. The partnership with the Holden Arboretum staff has expanded the scope of the research project to use the two cells to explore how different plant communities and horticulture practices impact bioretention performance and aesthetics. Both practices were installed in publicly visible parking lot “islands” located in the main parking area for the visitor center.

Site EvaluationTest pits for each planned bioretention installation were excavated to a depth of approximately 4 feet to measure the infiltration rate at the proposed excavation depth of the bioretention practices. Two tests in the north pit yielded readings of 0.02 in/hr whereas two tests in the south pit yielded readings of 0.02 and 0.08 in/hr, readings similar to the 0.02 in/hr infiltration rate predicted by the Soil Water Characteristics Calculator (K.E. Saxton et al., 1986). The site was surveyed to determine catchment boundaries, slope, and percentage of impervious cover.

DesignOverviewProject team engineers from NSCU and ODNR-DSWR worked collaboratively with Holden Arboretum staff on the design. The surface area of each bioretention cell was sized at 5% of the contributing impervious area to meet the RWLD specification. The design incorporated the existing catch basins and storm sewer, and accommodated hydrologic monitoring in both catch basins. An upturned elbow was attached to the underdrain in each cell to create a 21” internal water storage layer (or sump) to improve hydrologic performance. Water table wells were incorporated to measure ponding depth in the profile of each bioretention cell.

The final design focused on enhancing stormwater treatment by increasing retention capacity, reducing peak flows, removing pollutants, and promoting infiltration and denitrification.

Holden Arboretum staff contributed their horticultural expertise to the landscaping design of each bioretention cell. Plantings had to be aesthetically pleasing, tolerant of a broad range of weather conditions, commercially available to landscapers, and small enough so as to not interfere with visual clearance. Aesthetic considerations that factor into planting selection include: timing and length of bloom, winter appearance, seasonal coloration, and spatial arrangement. Additional considerations about root type and length were also factors in the landscape design process. Holden Arboretum selected plants that use different rooting zones in the rhizosphere to lessen direct competition and increase water uptake and transpiration. Challenges One design challenge was preventing erosion where runoff from a heavy storm flowed into the bioretention cell before it was seeded and stabilized. The area was leveled and seeded to establish root systems to stabilize the surface soil layer and decrease maintenance. Ground cover plantings will help to decrease erosion and can prevent the growth of weeds. They can also decrease the need for mulch, reducing the likelihood of clogged drainage systems or monitoring equipment.

ConstructionOverview Like the design process, construction was a collaboration of the project team and Holden Arboretum staff. The cells were excavated using a small track hoe. A skid

Installed BMPs with Area:Bioretention Cell 1 (North)- 850 ft²Bioretention Cell 2 (South)- 610 ft²

Catchment Area & Loading Ratio:North Catchment- .67 Acres (34.33:1)South Catchment- .43 Acres (34:27:1)

Impervious Area & Percent Cover:North Catchment: .39 Acres (58%)South Catchment: .28 Acres (59%)

Installation Costs:TBD

Recommended Maintenance:Bioretention Cell Landscaping

Installation Dates:Construction & Landscaping- Fall 2013Monitoring- October 2013

Holden Arboretum

Quick Facts

steer was used to deliver layers of gravel and sand. Each layer was spread out and leveled by hand using rakes and shovels. The bottom layer consisted of 12 inches of washed #57 angular gravel that acted as a drainage layer and bedding for the underdrain. Installation of the underdrains required modification of the catch basins. Holden Arboretum staff drilled new outlet holes, installed PVC pipe outlets, and then sealed each outlet with hydraulic cement. Next, a filter layer was installed that consisted of 3 inches of medium concrete sand on top of 3 inches of #78 gravel. The final layer consisted of 36 inches of bioretention soil mix. Following the initial construction, the bioretention cells were allowed to establish for a few weeks. During this time, the slopes leading into each cell were re-graded, seeded and stabilized to prevent erosion. Holden Arboretum staff planted herbaceous species in the south cell, and woody shrub species and a honeylocust tree in the north cell. Plantings were arranged in groupings and sweeps for aesthetic appeal.

ChallengesThe team encountered a few minor challenges during excavation. They cracked the outlet pipe leading to one of the catch basins and repaired it with hydraulic cement. An electrical conduit for a lamppost was also damaged, but was repaired as well. These minor setbacks highlight the challenges that can occur during excavations, such as finding unmarked utilities.

Due to a miscommunication, the height of the catch basins were raised to a height of 15 inches above the filter bed instead of the 12 inch design specified. Because these sites are being closely monitored, it was decided to leave the overflows at the higher elevation to see how the systems perform with the deeper surface ponding.

The catch basin overflows can be lowered if needed.

A few issues with material sourcing occurred during construction. Much too large a quantity of #57 gravel was delivered, highlighting the need to double-check material quantities during ordering. Also, the first delivery of filter sand had to be rejected because it was fill sand instead of concrete sand. This demonstrates the importance of clear communication with suppliers to ensure the accuracy of orders. It also is good practice to inspect materials upon delivery to make sure they comply with design specifications. Another example of a challenge with material sourcing occurred during the first delivery of planting soil media. It was not well screened and there were big chunks of compost in the mix. The construction crew broke up these clumps manually, but a request was put in for the second delivery to be better screened. All the materials installed at Holden Arboretum were high quality, but it took some onsite management to ensure this was the case.

After construction some minor erosion occurred at an area with point source runoff. This issue was resolved once the site was better stabilized, but it demonstrates the importance of site stabilization during or immediately following construction. Use of grass sod or ground cover plantings on side slopes and on pretreatment filter strips can help to combat erosion in areas with concentrated flow.

MonitoringEquipment & MethodsMonitoring equipment installation occurred two weeks after construction. NCSU stormwater engineers installed two V-notch weir plates in each catch basin and water table wells in each bioretention cell to monitor hydrology. Conductivity of flow

was also measured with a separate logger. Soil moisture and temperature arrays were installed in the planting soil layer (at depths of 6”, 1 ft, 2 ft, and 3 ft below the media surface) to monitor soil conditions for bioretention cells.

ChallengesThe catch basins in each bioretention cell were fairly old and there was concern about water leaking into or out of them. To resolve this issue, the monitoring team carefully examined each basin for visible cracks or holes after excavation. The catch basins seemed to be sound, but hydraulic cement was used to line the entire inside of each catch basin as a precaution.

Preliminary ResultsMonitoring began at the Holden Arboretum bioretention cells on October 5, 2013. Through the first three months of monitoring, nineteen storm events were recorded, with rainfall depths between 0.12 and 1.68 inches. During these events, overflow did not occur in either the south or north cell, suggesting that the bowl storage may be slightly oversized or that the infiltration rate of the media is quite high. Peak flow rates varied between 0 and 0.054 cfs at the south cell. The peak flow rates at the north cell were between 0 and 0.066 cfs. Thus far, outflow volume has totaled 2606 cubic feet for the south cell and 3980 cubic feet for the north cell. This is approximately 40% of the expected inflow in both cases, showing that the bioretention cells are performing quite similarly. The larger peak flow rates and flow volumes are reflective of the north cell’s larger watershed area.

14

15

Lessons Learned

The following are some key insights from the design and construction of LID stormwater practices in northern Ohio during the first two years of the project. Feedback from project team members, collaborative learning group members, and interviewees was used to synthesize these lessons learned.

Design is just one step in the implementation process for LID stormwater practices; construction is just as important. Construction oversight must be provided by knowledgeable staff to ensure that LID SCMs are installed correctly and function as intended. Proactive communication is also essential throughout every project phase to ensure everyone understands what needs to be accomplished and how any challenges will be addressed.

The following key insights are organized by project phase.

• Establish goals in advance of the design process and provide opportunities for relevant stakeholders to provide feedback in a timely and coordinated manner to minimize redesign costs.

• Engineers should visit project sites before attempting to create site designs, because a wide range of factors need to be considered at each site that may not be apparent from surveys or aerial photographs.

• Involve people on site visits who know where infrastructure is located and/or have experience with developing conceptual plans for LID systems.

• Conduct soil investigations during site evaluations and identify offsite drainage. It’s helpful to determine the historical context of the site (i.e. soil grading or filling from previous development), since this can affect results of soil investigations.

• Infiltration testing is critical for determining design parameters for LID SCMs

• In greenfield development situations, the Soil Water Characteristics Calculator can be used to estimate infiltration rates and select appropriate LID approaches.

• Aesthetics are important when designing SCMs because they are often constructed at publicly visible locations. Implementation will be much more widespread if projects are visually appealing.

• Design SCMs with a level subgrade to allow for even ponding that will promote exfiltration. Terraced designs with check dams can be used to address changes in slope.

• Design SCM underdrain systems with ample cleanouts to facilitate maintenance and prevent the build-up of sediment in drainage pipes.

• Specify appropriate materials for each type of SCM to make sure they will perform as intended.

• Specify “washed angular limestone” for the base of permeable pavements systems.

• Landscaping of bioretention cells is very important and requires careful consideration. Select plantings that tolerate a variety of soil moisture conditions, avoid visual clearance issues, minimize routine maintenance, provide year-round aesthetic appeal, and are commercially available to landscapers.

Pre-Design

Design

Overall

16

• Educate site owners, designers, inspectors, contractors, and others about purpose and function of LID SCMs to minimize problems during construction.

• Communicate with design engineers, site inspectors, and construction contractors about the importance of using appropriate materials, and provide potential bidders with supporting information about required materials, sequencing, and construction techniques.

• Ensure site inspectors are experienced and knowledgeable about constructing LID SCMs.

• Use specific language to describe LID SCMs when advertising projects. Use key words that differentiate the project from other types of construction and avoid vague terms like “restoration” and “retrofit” unless appropriate qualifiers are used.

• Hire certified and experienced contractors whenever possible. The ability to recognize the need for, and make adjustments during construction is a critical skill refined with experience. Make sure site inspectors are experienced and knowledgeable about LID SCMs. Provide site specific or SCM specific guidance and education as needed.

• Preconstruction meetings should be used to review plans with designers, owners, contractors and inspectors. Review the following key items: 1) construction sequencing and practices, 2) avoiding compaction of subgrade and scarification of underlying soils, 3) monitoring well installation (if applicable), 4) erosion control and site stabilization to prevent clogging, 5) protection of underdrains before and during construction, 6) material specifications, and 7) design engineer verification of critical installation points.

Pre-Construction

Construction

• Permeable paver systems with curved designs are more expensive to install because of the added labor costs associated with making additional curb cuts. Designs requiring fewer curb cuts can drastically reduce overall costs.

• Mechanical installation of permeable pavers and bedding significantly reduces installation costs.

• Permeable pavers can be installed late in the construction season (early winter) provided that the ground is not frozen. Mechanical paving equipment can be outfitted with heaters to ensure that pavers and aggregate bedding do not freeze and bind together.

• Pervious concrete needs to be carefully protected with plastic sheeting during the initial seven day curing period. Ensure that sheeting is properly secured.

• Wetting the subgrade of pervious concrete installations prior to pouring concrete may improve the appearance of final product and reduce surface raveling.

• Use the correct materials and avoid compacting the subgrade soil when constructing LID SCMs. Educate excavators and contractors on how to avoid soil compaction and scarify the subgrade soils beneath LID installations to promote exfiltration.

• Critical points of installation and materials inspection need to be verified (preferably by the design engineer) even with the best contractors. Construction sequencing is important for preventing errors and ensuring SCMs are functional once installed.

• Site stabilization during and after construction is critical for preventing clogging of newly installed SCMs.

BMP Maintenance

Plant Selection

• Careful selection of plantings can minimize erosion, enhance aesthetics, and reduce overall maintenance and maintenance costs.

• Native ground cover plantings are recommended because they reduce the amount of mulch required and prevent growth of weeds. • In Ohio, the aesthetics of plantings during the winter months need to be considered.

• Consider space constraints, visual clearance, arrangement, and rooting zones of plantings.

Maintenance

• Bioretention cells require routine landscaping maintenance to ensure they are working properly and remain aesthetically pleasing. • Diseased vegetation should be treated and dead vegetation should be removed.

• Mowing or pruning may be needed depending upon the types of plantings and the desired amount of visual clearance.

• If a bioretention cell is receiving a heavy sediment load from the watershed, it is necessary to periodically remove accumulated sediment to prevent clogging.

• Prevent sediment from reaching the bioretention cell by ensuring the drainage area for the SCM is vegetated or use appropriate pretreatment or sediment controls.

• The procedures used for maintaining bioretention cells are very similar to those used on most commercial and municipal landscapes. Hiring an experienced landscaper educated on the purpose and function of bioretention cells is a simple and cost effective way to ensure routine maintenance is being performed properly.

• If the bioretention cell is ponded for more than 12 hours after a rain event, the maintenance personnel should check the cell for a clogging layer near the surface of the media.

Pervious Concrete, Asphalt and Permeable Pavers Maintenance

• Power wash pervious concrete (at a shallow angle) after a 10 day curing period following construction to remove any remaining loose gravel and debris.

• Maintenance needs can be determined by visual inspection and infiltration testing. Inspect system during and after rain events to determine need for maintenance.

• Clean pervious pavements with a vacuum sweeper truck or industrial outdoor vacuum at least once per year, preferably during late spring or early summer to prevent clogging. The frequency of vacuuming depends upon the amount of use, surrounding landscape, and stormwater runoff impacting the pervious concrete.

• After sweeping porous pavers, it may be necessary to sweep #78 stone across the pavers to fill any voids between pavers.

• Never dump mulch, leaves, soil, or any other fine materials on the pavement surface that could cause clogging.

• Snow removal can be performed using the same methods used for impervious surfaces. Use of a steel, plastic, or hard rubber edged plow, or a snow blower, is acceptable.

• Limited salt or deicing products should be used on the pervious concrete for a year following construction because they interfere with the long-term curing process and could damage the pavement. If possible, do not use any salt products during the first year following installation.

Permeable Pavements Bioretention

17

Vacuum sweeper trucks can be used for permeable pavements

18

Collaborative Process

Collaborative learning is a process that engages individuals in a group setting to foster creative thought, constructive debate, joint fact finding, and shared knowledge creation. The success of this process hinges upon the participation of collaborative learning group (CLG) members and the project team’s technical and facilitation expertise.

Team members from the Consensus Building Institute (CBI) and Old Woman Creek National Estuarine Research Reserve (OWC NERR) are the primary facilitators and collaboration leads. They engage participants in the research effort and develop a shared learning environment that encourages interaction and fosters creative problem solving. Facilitation ensures that all CLG members have an equal opportunity to participate and keeps the group focused on productive discussion. The CLG is a voluntary group comprised of consulting and community engineers, regulators, stormwater utility managers, and watershed organizations. Meeting frequency is determined by the availability of new information and progress made toward project objectives. Meetings are held 2-3 times a year, which is frequent enough to keep participants engaged, but does not become a scheduling burden. Site tours and presentations from guest speakers are often featured to enhance the shared learning experience and promote constructive discussion. CLG members have stated that these meeting elements are extremely valuable, and have greatly added to their learning experience. They have also said that unstructured periods of the meetings have been valuable for networking and informal discussion with other stormwater professionals. CLG members are sharing project information with others and some are applying what they have learned in site planning and stormwater design.

The CLG has provided input and guidance on research priorities, site selection, SCM design, construction, monitoring, and modeling. CLG members will also provide feedback on training and tools to disseminate project results, including design guidance and SCM crediting tools. The interdisciplinary nature of the group allows the project to benefit from a range of different perspectives and suggestions that might otherwise be overlooked. CLG input ensures this research is relevant to practitioners and helps the project team to hone the research approach.

Project site tour during July 2013 CLG meeting

Why use a collaborative approach?The project’s collaborative learning approach is designed to ensure that stormwater management needs in Ohio are effectively addressed using applied research methods.

How has collaborative learning been used?

How has collaborative learning benefited the project?

Project site tour during September 2013 CLG meeting

19

LID System Schematics

Permeable PavementsPermeable pavement systems reduce stormwater volume and peak flow rates and reduce suspended solids, metals, petroleum hydrocarbons, and other pollutants in runoff. Stormwater is captured either by infiltrating through a highly porous pavement surface (specially formulated asphalt or concrete with most fines removed from the mix design) or through gaps filled with highly permeable aggregate between pavers. Permeable pavement systems have one or more open-graded aggregate layers beneath the pavement surface to provide structural support and temporary storage of stormwater. The recharge layer is designed to be a structurally stable subbase for the pavement and is constructed using #1 or #2 interlocking stone. It is important to note that all aggregates used for these systems should be washed and contain very few fines. Additionally, all stone should be angular (not river run) so it will interlock for structural support of the pavement.

Enhanced outlet designs create an area for internal water storage, promoting exfiltration and reducing the volume of stormwater entering the storm sewer through the underdrain. (Mathews, 2006) The water storage capacity within the recharge layer is determined by the depth of the aggregate between the underdrain and the underlying soil. Exfiltration can be further enhanced by loosening, ripping, or trenching the soils beneath the aggregate subbase using the teeth of an excavator during construction (Tyner et al. 2010).

Many types of permeable pavements are commercially available, including permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (Mathews,2006). Each pavement surface material has different specifications and applications, but all permeable pavement systems have similar subgrade designs.

Permeable Pavements

20

BioretentionBioretention systems are integrated into the landscape of small drainage areas and use soil media, sand, gravel, and plantings to remove pollutants. Research has shown that bioretention SCMs improve water quality by removing heavy metals, suspended solids, bacteria, nutrients, petroleum hydrocarbons, and organic compounds (Hunt et al., 2006). They are designed to promote a variety of different pollutant removal mechanisms including sedimentation, filtration, evapotranspiration, microbial breakdown, adsorption, and nutrient uptake by plants and microbes (Mathews, 2006; Hunt et al., 2006 ). Modification of outlet structures to include an upturned elbow on the underdrain creates an internal water storage layer in the practice that enhances denitrification, promotes exfiltration, reduces peak flow rates, and mitigates outflow temperatures (Hunt et al., 2006).

Bioretention systems capture stormwater runoff in a shallow surface depression (typically 9-12 inches deep) that allows the water to gradually percolate through the soil media. Stormwater is filtered as it moves through the soil media, filtration layer, and gravel layer. The soil media layer consists primarily of loam with no less than 80% sand and no greater than 10% clay mixed with 3-5% decomposed organic matter (Mathews, 2006). The filter layer is comprised of 3 inches of clean medium concrete sand over 3 inches of #8 stone or pea gravel. The gravel layer uses 12 inches of #57 stone to facilitate drainage, water storage, and protection of the underdrain system. Treated water exits the system by either exfiltrating into the ground, evaporating or transpiring into the atmosphere, or flowing into the storm sewer through the underdrain system. If runoff from a large storm event exceeds the surface ponding depth of a bioretention practice, then water overflows into the storm sewer bypassing treatment. Bioretention practices are typically sized to capture runoff from the first flush or water quality event (0.75”-1” of rain). Plantings should be aesthetically appealing year-round, commercially available to landscapers, and tolerant to salt and a broad range of soil moisture conditions.

Bioretention

21

Acknowledgements

Project Coordinator and Fiscal Agent• Amy H. Brennan; Chagrin River Watershed Partners, Inc.

Collaboration Leads• Heather Elmer; Old Woman Creek National Estuarine Research Reserve, Ohio Department of Natural Resources Division of Wildlife

• Ona Ferguson; Consensus Building Institute providing technical assistance

Applied Science Investigator• Jay D. Dorsey, Ph.D., P.E., ODNR, Division of Soil and Water Conservation

Additional project team members• Breann M. Hohman and Crystal Dymond, Erie Soil and Water Conservation District

• Frank Lopez and Cheryl Wolfe-Cragin, Old Woman Creek National Estuarine Research Reserve, ODNR Division of Wildlife

• Keely Davidson-Bennett, Chagrin River Watershed Partners, Inc.

• Ryan Winston, North Carolina State University

• Will Brown, University of New Hampshire TIDES Program

• Dan Bogoevski, Ohio Environmental Protection Agency• Jane Cullen, City of Sandusky• Justin Czekaj, City of Aurora• Eric Dodrill, Erie Soil and Water Conservation District• Alexander Etchill, John Hancock & Associates• John Farschmann, Erie County Engineer• Ken Fortney, Erie County Engineer• Lynette Hablitzel, Ohio EPA• Clyde Hadden, CT Consultants, Inc.• John Hancock, John Hancock & Associates, Inc.• Philip Kiefer, City of Kirtland / CT Consultants• Dave Ritter, Northeast Ohio Regional Sewer District• William Sanderson, Forest City Land Group• Leo Sferra, GPD Group• Rachel Webb, Northeast Ohio Regional Sewer District• Betsy Yingling, Northeast Ohio Regional Sewer District

Collaborative Learning Group

Project Team Members

ODNR Division of Soil and Water Resourceswww.ohiodnr.com/soilandwaterRainwater and Land Development Manual

Erie Soil & Water Conservation Districtwww.eriesoilandwater.org

North Carolina State UniversityStormwater Engineering Groupwww.bae.ncsu.edu/stormwater

Old Woman Creek National Estuarine Research Reservewildlife.ohiodnr.gov/oldwomancreek

Additional Resources

Funders

Collaborative Learning Group Meeting September 2013

This project was made possible with funding from the NERRS Science Collaborative, a NOAA program that funds collaborative research projects designed to bring intended users of science into the research process. http://www.nerrs.noaa.gov/ScienceCollaborative.aspx

The Friends of Old Woman Creek supported the TIDES internship and funded the printing of this document.

22

Perkins Township• Site Representative: Eric Dodrill, Erie Soil and Water Conservation District• Engineer: Alexander Etchill, John Hancock & Associates• Contractor(s): RMH and Star Building, Inc.

Orange Village• Site Representative: Bob Zugan and Mike Drnach, Orange Village• Design Engineer: Brian Mader, Orange Village Engineer and Stephen Hovancsek & Associates• Contractor: Steve Laczko, Seitz Builders

City of Willoughby Hills• Site Representatives: Mayor Robert Weger, Richard Iafelice, Frank Brichacek , Nate Catania and Fred Wyss, City of Willoughby Hills• Design Engineer: John Topolski, P.E., CT Consultants• Contractor: LCI Construction, Joseph Licursi and Nick Licursi Holden Arboretum• Site Representative: Roger Gettig, Holden Arboretum• Design Engineer: Jay Dorsey, Ohio Department of Natural Resources• Landscape Plan Design: Roger Gettig, Holden Arboretum• Contractors: Jay Dorsey, Ohio Department of Natural Resources, Holden Arboretum staff and Will Brown, University of New Hampshire TIDES Intern

Monitoring Contractors• William F. Hunt, North Carolina State University, Ph.D., P.E.• Shawn Kennedy, North Carolina State University• Ryan Winston, P.E., North Carolina State University• Paul Kovalcik, Biohabitats• Kevin Grieser, Biohabitats

Modeling Contractors• Scott Dierks, Cardno JFNew• William F. Hunt, Ph.D., P.E., North Carolina State University• Ryan Winston, P.E., North Carolina State University

Hunt, William F., and William G. Lord. “Bioretention Performance, Design, Construction, and Maintenance.” Urban Waterways Series Factsheet. North Carolina Cooperative Extension Service. 2006. Web. http://www.bae.ncsu.edu/stormwater/PublicationFiles/Bioretention2006.pdf

Mathews, John. Rainwater and Land Development: Ohio’s Standards for Stormwater Management, Land Development and Urban Stream Protection. 3rd ed. Ohio Department of Natural Resources, Division of Soil and Water Conservation. 2006. Web. http://www.dnr.state.oh.us/Portals/12/water/rainwater/8_30_2012RLDFiles/3-3-14RLD_All.pdf

Tyner, J. S., W. C. Wright, and P.A. Dobbs. 2009. Increasing exfiltration from pervious concrete and temperature monitoring. Journal of Environmental Management. 90(8):2636-2641.

K.E. Saxton et al., 1986 Estimating generalized soil-water characteristics from texture. Soil Sci. Soc. Amer. J. 50(4):1031-1036

This material is based upon work supported by the University of New Hampshire under Award No. Cooperative Agreement No. NA09NOS4190153 (CFDA No. 11.419) from National Oceanic and Atmospheric Association. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the University of New Hampshire or the National Oceanic and Atmospheric Association.

Site Representatives, Design Engineers, and Contractors

Sources

Observers/Partners• Carlo DeMarchi, Ph.D. Case Western Reserve University and Oberlin College• Cyndee Gruden, Ph.D., University of Toledo• Anne Jefferson, Ph.D., Kent State University

Interviewees• Alex Etchill, John Hancock & Associates• Nick Licursi and Anthony Licursi, LCI Construction• Bob Zugan, Orange Village Service Department• Eric Dodrill, Erie Soil and Water Conservation District• Roger Gettig, Holden Arboretum• Jay Dorsey, Ph.D., P.E., ODNR, Division of Soil and Water Conservation• John Topolski, P.E., CT Consultants• Betsy Yingling, Northeast Ohio Regional Sewer District

Additional InformationPlease visit the Chagrin River Watershed Partners website (www.crwp.org) for progress reports, meeting summaries, project updates, presentations, and other project resources. Project information can be accessed by selecting Research Projects from the Projects menu and

then clicking on NERRS Science Collaborative.

Direct Link: http://crwp.org/index.php/projects/research-

projects/nerrs-science-collaborative

For Questions, Please Contact: Chagrin River Watershed Partners

www.crwp.org (440) 975-3870

Old Woman Creek National Estuarine Research Reserve

http://wildlife.ohiodnr.gov/oldwomancreek(419) 433-4601