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Prof. Dr. William F. Hunt
WNR Distinguished Professor, Biological & Agricultural Engineering, North Carolina State University, Raleigh, NC 27695-7625, USA

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Journal article
Published: 26 July 2021 in Journal of Environmental Management
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This study evaluates the operational status of twenty-six biofilter facilities across nine cities in Sweden, with respect to their functional design criteria, engineered design features (filter media composition, hydraulic conductivity, and drawdown time), and includes a visual inspection of the biofilter components (pre-treatment, in/outlet structures, filter media, and vegetation). These indicators were used to examine the performance level of each biofilter in achieving their design objectives set by the operators. Furthermore, it was investigated whether the biofilter facilities had been properly maintained to meet the objectives. Results indicate that the soil media used was consistent with respect to percentage sand, fines, and organic matter and comparable to design recommendations used by municipalities in other countries. The field-tested hydraulic conductivity for the biofilters ranged from 30 to 962 mm/h. This range of values, along with noticeable sediment accumulation within the biofilter indicate that not all the sites were operating optimally. Pre-treatment stages in poor condition with high volumes of sediment and litter accumulation were the primary causes for, and indicators of, low hydraulic conductivity rates. The ponding volume calculations revealed that at least 40 % of facilities did not have enough capacity to retain every-day and/or design rainfall due to design and/or construction flaws. These analyses raise concerns that, for a considerable number of the biofilters surveyed, water retention and flood protection identified by operators as prioritised objectives are not being met. This raises significant concerns about the functionality of biofilter in practice. Finally, some suggestions are given for tackling the design and maintenance problems discovered.

ACS Style

Ali Beryani; Alisha Goldstein; Ahmed Mohammed Al-Rubaei; Maria Viklander; William F. Hunt; Godecke-Tobias Blecken. Survey of the operational status of twenty-six urban stormwater biofilter facilities in Sweden. Journal of Environmental Management 2021, 297, 113375 .

AMA Style

Ali Beryani, Alisha Goldstein, Ahmed Mohammed Al-Rubaei, Maria Viklander, William F. Hunt, Godecke-Tobias Blecken. Survey of the operational status of twenty-six urban stormwater biofilter facilities in Sweden. Journal of Environmental Management. 2021; 297 ():113375.

Chicago/Turabian Style

Ali Beryani; Alisha Goldstein; Ahmed Mohammed Al-Rubaei; Maria Viklander; William F. Hunt; Godecke-Tobias Blecken. 2021. "Survey of the operational status of twenty-six urban stormwater biofilter facilities in Sweden." Journal of Environmental Management 297, no. : 113375.

Journal article
Published: 01 January 2020 in Blue-Green Systems
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Wet retention ponds temporarily store and slowly release stormwater to mitigate peak flow rates and remove particulate-bound pollutants. However, with sandy underlying soils, wet retention ponds may provide additional benefits through infiltration, thereby recharging groundwater and supporting baseflow in streams. Current design guidance often requires lining wet ponds to prevent infiltration; however, modern stormwater management strategies recommend maximizing runoff volume reduction through infiltration. Two infiltrating wet retention ponds in Fayetteville, NC, USA, were monitored for one year to assess volume reduction, peak flow mitigation, and water quality. In some months, 100% of stormwater runoff infiltrated and evaporated, with cumulative annual volume reductions of 60 and 51% for the two ponds. For events up to 76 mm (equivalent to the local 1-yr, 24-hr storm), measured peak flow reductions were similar to those of typical (non-infiltrating) wet ponds (median 99% reduction). Dissolved nitrogen species, total and dissolved phosphorus, and total suspended solids (TSS) concentrations were significantly reduced in both ponds; mean percent reductions were greater than 30% for each of these pollutants. Effluent concentrations were on par with typical (non-infiltrating) wet ponds previously monitored in North Carolina. Due to the aforementioned runoff reduction, nutrient and TSS loads were reduced by (at minimum) 35 and 67%, respectively. Infiltrating wet ponds were able to meet both peak flow and volume mitigation goals, suggesting that they could be a common tool in regions with sandy soils.

ACS Style

Joshua B. Baird; Ryan J. Winston; William F. Hunt. Evaluating the hydrologic and water quality performance of novel infiltrating wet retention ponds. Blue-Green Systems 2020, 2, 282 -299.

AMA Style

Joshua B. Baird, Ryan J. Winston, William F. Hunt. Evaluating the hydrologic and water quality performance of novel infiltrating wet retention ponds. Blue-Green Systems. 2020; 2 (1):282-299.

Chicago/Turabian Style

Joshua B. Baird; Ryan J. Winston; William F. Hunt. 2020. "Evaluating the hydrologic and water quality performance of novel infiltrating wet retention ponds." Blue-Green Systems 2, no. 1: 282-299.

Journal article
Published: 21 November 2019 in Journal of Environmental Management
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Dry detention basins (DDBs) are a type of stormwater control measure (SCM) designed to provide flood storage, peak discharge reduction, and some water quality improvement through sedimentation. DDBs are ubiquitous in the urban environment, but are expensive to maintain. In this study, two overgrown DDBs near Raleigh, NC, receiving highway runoff were monitored for up to one year to quantify their water quality and hydrologic performance. Both basins, B1 and B2, have not received vegetation maintenance since construction in 2007. Flow-weighted composite samples were collected during storm events and analyzed for nutrients (Total Phosphorus (TP), Ortho-phosphorus (OP), Ammonia-N (NH3), NO2-3-N (NOX), and Total Kjeldahl Nitrogen (TKN)), total suspended solids (TSS), and total Cd, Cu, Pb, and Zn. An annual water balance was also conducted to quantify runoff volume reduction. Despite low influent concentrations from the highway, significant removal efficiencies were found for all constituents except NH3 in B1. TP, OP, NOX, TSS, and Zn were reduced in B2. Both basins achieved greater than 41% volume reduction through soil infiltration and evapotranspiration, resulting in significant pollutant load reductions for all detected constituents, between 59% and 79% in B1 and 35% and 81% in B2. This study provides evidence that overgrown and unmaintained DDBs can reduce pollutant concentrations comparable to those reported for maintained DDBs, while reducing more volume than standard DDBs. Moreover, carbon sequestration likely increases while maintenance costs decrease.

ACS Style

Austin D. Wissler; William F. Hunt; Richard A. McLaughlin. Hydrologic and water quality performance of two aging and unmaintained dry detention basins receiving highway stormwater runoff. Journal of Environmental Management 2019, 255, 109853 .

AMA Style

Austin D. Wissler, William F. Hunt, Richard A. McLaughlin. Hydrologic and water quality performance of two aging and unmaintained dry detention basins receiving highway stormwater runoff. Journal of Environmental Management. 2019; 255 ():109853.

Chicago/Turabian Style

Austin D. Wissler; William F. Hunt; Richard A. McLaughlin. 2019. "Hydrologic and water quality performance of two aging and unmaintained dry detention basins receiving highway stormwater runoff." Journal of Environmental Management 255, no. : 109853.

Journal article
Published: 12 October 2019 in Journal of Environmental Management
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Regenerative stormwater conveyance (RSC) is a recently developed stormwater control measure that marries the concepts of bioretention and stream restoration. RSC mitigates stormwater runoff by converting surface flow to subsurface seepage using a series of pools and riffles built over a sand media bed. Subsurface seepage flows through media and exits the RSC beneath the outlet weir. Previous studies on RSC pollutant mitigation have focused on surface flow discharges from the RSC. To date, no known research has been conducted on the potential pollutant contributions of RSC seepage, despite the fact that this water also enters receiving waters. This research used Multi-Point Sampling coupled with in-situ ultraviolet–visual spectroscopy to measure nitrogen in seepage during simulated storm events (n = 9) at a field-scale RSC in Raleigh, North Carolina. Calibrations between light absorbance and concentrations were acceptable (Nash-Sutcliffe coefficient > 0.65) for nitrate and total ammoniacal nitrogen (TAN) and very good (Nash-Sutcliffe coefficient > 0.90) for total Kjehdahl nitrogen (TKN). Early storm simulations revealed some initial nutrient flushing from the substrate, which subsided by the third simulation. Overall, subsurface seepage nitrate, TAN, and TKN concentrations were lower by 29%, 57%, and 4% relative to storm inflow concentrations, respectively. Computed subsurface nitrogen concentrations demonstrated temporal variability, highlighting dynamic transport and biogeochemical transformations in saturated and unsaturated conditions. Nitrogen concentrations were lower in seepage than in surface flow; however, due to the high volume of runoff converted to seepage, nitrogen loads discharged in seepage can be larger than those of surface flow. Further research is needed to examine subsurface pollutant reductions under varying hydrologic and seasonal conditions.

ACS Style

Adrienne R. Cizek; Jeffrey P. Johnson; François Birgand; William F. Hunt; Richard A. McLaughlin. Insights from using in-situ ultraviolet–visible spectroscopy to assess nitrogen treatment and subsurface dynamics in a regenerative stormwater conveyance (RSC) system. Journal of Environmental Management 2019, 252, 109656 .

AMA Style

Adrienne R. Cizek, Jeffrey P. Johnson, François Birgand, William F. Hunt, Richard A. McLaughlin. Insights from using in-situ ultraviolet–visible spectroscopy to assess nitrogen treatment and subsurface dynamics in a regenerative stormwater conveyance (RSC) system. Journal of Environmental Management. 2019; 252 ():109656.

Chicago/Turabian Style

Adrienne R. Cizek; Jeffrey P. Johnson; François Birgand; William F. Hunt; Richard A. McLaughlin. 2019. "Insights from using in-situ ultraviolet–visible spectroscopy to assess nitrogen treatment and subsurface dynamics in a regenerative stormwater conveyance (RSC) system." Journal of Environmental Management 252, no. : 109656.

Journal article
Published: 20 June 2019 in Water
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Bioswales are a promising stormwater control measure (SCM) for roadway runoff management, but few studies have assessed performance on a field scale. A bioswale is a vegetated channel with underlying engineered media and a perforated underdrain to promote improved hydrologic and water quality treatment. A bioswale with a rip-rap lined forebay was constructed along state highway NC 211 in Bolivia, North Carolina, USA, and monitored for 12 months. Thirty-seven of the 39 monitored rain events exfiltrated into underlying soils, resulting in no appreciable overflow or underdrain volume. The bioswale completely exfiltrated a storm event of 86.1 mm. The one event to have underdrain-only flow was 4.8 mm. The largest and third-largest rainfall depth events (82.6 and 146 mm, respectively) had a large percentage (85%) of volume exfiltrated, but also had appreciable overflow and underdrain volumes exiting the bioswale, resulting in no peak flow mitigation. Overall, this bioswale design was able to capture and manage storms larger than the design storm (38 mm), showing the positive hydrologic performance that can be achieved by this bioswale. The high treatment capabilities were likely due to the high infiltration rate of the media and the underlying soil, longer forebay underlain with media, gravel detention layer with an underdrain, and shallow slope.

ACS Style

Rebecca A. Purvis; Ryan J. Winston; William F. Hunt; Brian Lipscomb; Karthik Narayanaswamy; Andrew McDaniel; Matthew S. Lauffer; Susan Libes. Evaluating the Hydrologic Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA. Water 2019, 11, 1291 .

AMA Style

Rebecca A. Purvis, Ryan J. Winston, William F. Hunt, Brian Lipscomb, Karthik Narayanaswamy, Andrew McDaniel, Matthew S. Lauffer, Susan Libes. Evaluating the Hydrologic Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA. Water. 2019; 11 (6):1291.

Chicago/Turabian Style

Rebecca A. Purvis; Ryan J. Winston; William F. Hunt; Brian Lipscomb; Karthik Narayanaswamy; Andrew McDaniel; Matthew S. Lauffer; Susan Libes. 2019. "Evaluating the Hydrologic Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA." Water 11, no. 6: 1291.

Journal article
Published: 01 August 2018 in Journal of Environmental Engineering
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Regenerative stormwater conveyance (RSC) is an open-channel, sand-filtering system composed of a series of shallow aquatic pools, riffles and weirs, native vegetation, and underlying media beds. Surface runoff entering a RSC is conveyed as nonerosive surface flow or subsurface seepage through the media, and exits the system as surface flow, seepage out, exfiltration into the parent soil, or evapotranspiration (ET). While RSCs are expected to perform similarly to other sand-media-based low-impact development (LID) stormwater control measures (SCMs), little field research on this emerging technology have been published to date in peer-reviewed literature. Hydrologic and water quality of a RSC in the Piedmont (Alamance County) ecoregion of North Carolina was monitored from July 2013–June 2014. The Alamance RSC reduced volume and peak flow by a median 78 and 76%, respectively, while mimicking both predevelopment hydrograph shape and hydrologic flow pathways. RSC outflow matches the modeled predevelopment hydrograph shape and pathway components, including both pre-event and event water, as determined by deuterium isotope concentrations. Optimal storm mitigation performance is expected when RSCs include (1) a minimum of three pool/riffle cells, (2) established vegetation, and (3) exfiltration trenches to promote exfiltration into parent soils through extended subsurface ponding. By combining seep out water with surface flow from the RSC, the practice reduced incoming total suspended solids (TSS), total phosphorus (TP), and total nitrogen (TN) loads by a median of 70, 20, and 26%, respectively, likely due to filtration. The potential exists for further nutrient reduction if vegetated, wetlandlike conditions are present. Moreover, locating the RSC over more permeable soils would likely improve hydrologic performance.

ACS Style

Adrienne R. Cizek; William F. Hunt; Ryan J. Winston; Sarah E. Waickowski; Karthik Narayanaswamy; Matthew S. Lauffer. Water Quality and Hydrologic Performance of a Regenerative Stormwater Conveyance in the Piedmont of North Carolina. Journal of Environmental Engineering 2018, 144, 04018062 .

AMA Style

Adrienne R. Cizek, William F. Hunt, Ryan J. Winston, Sarah E. Waickowski, Karthik Narayanaswamy, Matthew S. Lauffer. Water Quality and Hydrologic Performance of a Regenerative Stormwater Conveyance in the Piedmont of North Carolina. Journal of Environmental Engineering. 2018; 144 (8):04018062.

Chicago/Turabian Style

Adrienne R. Cizek; William F. Hunt; Ryan J. Winston; Sarah E. Waickowski; Karthik Narayanaswamy; Matthew S. Lauffer. 2018. "Water Quality and Hydrologic Performance of a Regenerative Stormwater Conveyance in the Piedmont of North Carolina." Journal of Environmental Engineering 144, no. 8: 04018062.

Journal article
Published: 23 July 2018 in Journal of Environmental Management
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Permeable pavement is an effective tool for improving stormwater hydrology and water quality when sited over soils with high infiltration rates, but its efficacy over less permeable soils is uncertain. This study examined permeable pavement performance when built over a low-conductivity, clay soil. Four parking stalls (50 m2 total area) were retrofitted with permeable interlocking concrete pavement (PICP) to treat 15.2 m2 of contributing impervious area (0.3:1 run-on ratio). Using an elevated underdrain, the site incorporated a 150-mm internal water storage (IWS) zone to increase exfiltration and promote anaerobic conditions for denitrification. From March 2014 – April 2015, 22% of influent runoff volume was reduced via exfiltration and evaporation. Inter-event drawdown of the IWS zone created storage to capture and exfiltrate more than 70% of the runoff volume from precipitation events less than 8 mm, and peak flows were significantly reduced (median 84%). Relative to stormwater runoff from a nearby impermeable asphalt reference watershed, the permeable pavement produced significantly lower event mean concentrations (EMCs) of all pollutants except nitrate, which was significantly higher. Permeable pavement effluent and reference watershed runoff were 99%, 68%, and 96% different for total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP), respectively. Significantly lower permeable pavement effluent EMCs for copper (Cu, 79%), lead (Pb, 92%) and zinc (Zn, 88%) were also observed. The median effluent concentrations of TN (0.52 mg/L), TP (0.02 mg/L), and TSS (7 mg/L) were all very low relative to the literature. Sampling of nitrogen species in the IWS zone 12, 36, 60, and 84 hours post-rainfall was done to better understand mechanisms of nitrogen removal in permeable pavement; results indicated denitrification may be occurring in the IWS zone. Effluent pollutant load from the permeable pavement was at minimum 85% less than from nearby untreated asphalt runoff for TP, TSS, Cu, Pb, and Zn, and was 73% less for TN. Permeable pavements built over low-permeability soils with internal water storage can considerably improve long-term hydrology and water quality.

ACS Style

Alessandra S. Braswell; Ryan J. Winston; William F. Hunt. Hydrologic and water quality performance of permeable pavement with internal water storage over a clay soil in Durham, North Carolina. Journal of Environmental Management 2018, 224, 277 -287.

AMA Style

Alessandra S. Braswell, Ryan J. Winston, William F. Hunt. Hydrologic and water quality performance of permeable pavement with internal water storage over a clay soil in Durham, North Carolina. Journal of Environmental Management. 2018; 224 ():277-287.

Chicago/Turabian Style

Alessandra S. Braswell; Ryan J. Winston; William F. Hunt. 2018. "Hydrologic and water quality performance of permeable pavement with internal water storage over a clay soil in Durham, North Carolina." Journal of Environmental Management 224, no. : 277-287.

Journal article
Published: 01 June 2018 in Journal of Environmental Engineering
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Regenerative stormwater conveyance (RSC) is a stormwater control measure (SCM) built in a channel that uses a series of riffles, grade control structures, and pools with an underlying sand media layer to detain and treat stormwater runoff. A purpose-built experimental field RSC was subjected to simulated hydrographs by mixing dissolved nitrogen and phosphorus into inflow from a managed retention pond. The system storage capacity of 30.5 m2 within the pools (14.2 m2) and sand layer (16.3 m2) was sized to store the runoff volume from the 25-mm event. Twelve storm simulations were conducted under varying conditions of storm depth (25 and 38 mm) and antecedent dry periods (1 day and 3 days). Simulations confirmed that RSC can convert large portions of flow volumes from surface to subsurface flow; mean reductions in surface flow volumes were 80% for the 25-mm event and 40% for the 38-mm event. Reductions in dissolved pollutant concentrations in surface flow were insignificant or very minor for all analytes. However, mean reductions in subsurface flow concentrations were high for both total Kjeldahl nitrogen (TKN, 79%) and orthophosphate (81%). Because of well-drained subsurface conditions, nitrification of TKN to nitrate was observed, leading to a 250% increase in nitrate concentration. Results of the simulation study indicate that microbial transformation and sorption mechanisms are present in RSC subsurface outflow. Subsurface flow contributed 66% of the total nitrogen load and 42% of the total phosphorus load for the 25-mm event. When adequately sized, RSCs can provide substantial hydrologic mitigation for urban drainage areas. As implementation of RSC continues, regulators and designers are encouraged to consider RSC subsurface flow as an important contribution to downstream pollutant load. Proper filter media selection and differentiated aerobic/anaerobic conditions are essential to optimize subsurface flow treatment.

ACS Style

Kevin M. Koryto; William F. Hunt; Consuelo Arellano; Jonathan L. Page. Performance of Regenerative Stormwater Conveyance on the Removal of Dissolved Pollutants: Field Scale Simulation Study. Journal of Environmental Engineering 2018, 144, 04018039 .

AMA Style

Kevin M. Koryto, William F. Hunt, Consuelo Arellano, Jonathan L. Page. Performance of Regenerative Stormwater Conveyance on the Removal of Dissolved Pollutants: Field Scale Simulation Study. Journal of Environmental Engineering. 2018; 144 (6):04018039.

Chicago/Turabian Style

Kevin M. Koryto; William F. Hunt; Consuelo Arellano; Jonathan L. Page. 2018. "Performance of Regenerative Stormwater Conveyance on the Removal of Dissolved Pollutants: Field Scale Simulation Study." Journal of Environmental Engineering 144, no. 6: 04018039.

Journal article
Published: 01 June 2018 in Land Use Policy
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The terms green infrastructure and natural capital are interrelated. Natural capital as a concept is focused upon environmental assets which can provide ecosystem services, either directly or indirectly to humans; the concepts of natural capital and ecosystem services emphasize the benefits humans obtain from the natural environment. Green infrastructure is a concept with a wide range of definitions. The term is sometimes applied to networks of green open spaces found in or around urban areas. In other contexts green infrastructure can describe alternative engineering approaches for storm water management, with co-benefits of temperature control, air quality management, wildlife habitats and/or recreation and amenity space. No environments are completely free of human influence and therefore no environments are entirely natural. Rather, there is a spectrum of degrees of ‘naturalness’ ranging from environments with minimal human influence through to built environments. A trio of case studies presented herein illustrates how green infrastructure projects are a practical application of the natural capital concept in that they seek to preserve and enhance natural capital via a management approach which emphasizes the importance of environmental systems and networks for the direct provision of ecosystem services to human populations. Natural capital forms critical components of all green infrastructure projects.

ACS Style

Jonathan Chenoweth; Andrew R. Anderson; Prashant Kumar; W.F. Hunt; Sarah Jane Chimbwandira; Trisha L.C. Moore. The interrelationship of green infrastructure and natural capital. Land Use Policy 2018, 75, 137 -144.

AMA Style

Jonathan Chenoweth, Andrew R. Anderson, Prashant Kumar, W.F. Hunt, Sarah Jane Chimbwandira, Trisha L.C. Moore. The interrelationship of green infrastructure and natural capital. Land Use Policy. 2018; 75 ():137-144.

Chicago/Turabian Style

Jonathan Chenoweth; Andrew R. Anderson; Prashant Kumar; W.F. Hunt; Sarah Jane Chimbwandira; Trisha L.C. Moore. 2018. "The interrelationship of green infrastructure and natural capital." Land Use Policy 75, no. : 137-144.

Journal article
Published: 03 May 2018 in Urban Water Journal
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ACS Style

Ryan J. Winston; Jacob T. Powell; William F. Hunt. Retrofitting a grass swale with rock check dams: hydrologic impacts. Urban Water Journal 2018, 16, 404 -411.

AMA Style

Ryan J. Winston, Jacob T. Powell, William F. Hunt. Retrofitting a grass swale with rock check dams: hydrologic impacts. Urban Water Journal. 2018; 16 (6):404-411.

Chicago/Turabian Style

Ryan J. Winston; Jacob T. Powell; William F. Hunt. 2018. "Retrofitting a grass swale with rock check dams: hydrologic impacts." Urban Water Journal 16, no. 6: 404-411.

Journal article
Published: 01 April 2018 in Journal of Hydrologic Engineering
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Permeable pavements benefit urban hydrology through detention of stormwater in the aggregate base and subsequent exfiltration to the underlying soil. The majority of previous research has focused on permeable pavements constructed in sandy soils and/or treating only direct rainfall. Four permeable pavements employing internal water storage (IWS) zones and situated over low-permeability soils were intensively monitored for their hydrologic performance in northern Ohio. Volume reduction varied from 16 to 53% for permeable pavements with low drawdown rates (<0.35 mm/h) and loading ratios (Watershed Area+Permeable Pavement AreaPermeable Pavement Area) exceeding 5∶1. Postconstruction drawdown rates were similar to saturated hydraulic conductivity (Ksat) measured during construction, suggesting that lateral exfiltration and evaporation were relatively minor contributors to volume reduction. Stormwater was completely captured (i.e., no discharge from the permeable pavements) during 4–80% of observed storm events. Average depth of abstraction ranged from 3.0 mm (site with highest loading ratio) to 25.2 mm (site treating only direct rainfall). Substantial peak flow mitigation was observed for all rainfall events not producing surface runoff (i.e., untreated bypass). Under these conditions, peak flow was diminished by more than 80% for seven events exceeding the 1-year, 5-min design rainfall intensity for Cleveland, Ohio. Lower loading ratios, reduced surface runoff, an IWS zone, and higher underlying soil Ksat directly impacted volume reduction and peak flow mitigation. Overall, permeable pavement mitigated negative hydrologic impacts of impervious surfaces even when sited over low-conductivity clay soils.

ACS Style

Ryan J. Winston; Jay D. Dorsey; Alessandra P. Smolek; William F. Hunt. Hydrologic Performance of Four Permeable Pavement Systems Constructed over Low-Permeability Soils in Northeast Ohio. Journal of Hydrologic Engineering 2018, 23, 04018007 .

AMA Style

Ryan J. Winston, Jay D. Dorsey, Alessandra P. Smolek, William F. Hunt. Hydrologic Performance of Four Permeable Pavement Systems Constructed over Low-Permeability Soils in Northeast Ohio. Journal of Hydrologic Engineering. 2018; 23 (4):04018007.

Chicago/Turabian Style

Ryan J. Winston; Jay D. Dorsey; Alessandra P. Smolek; William F. Hunt. 2018. "Hydrologic Performance of Four Permeable Pavement Systems Constructed over Low-Permeability Soils in Northeast Ohio." Journal of Hydrologic Engineering 23, no. 4: 04018007.

Journal article
Published: 01 February 2018 in Journal of Environmental Engineering
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Manufactured treatment devices (MTDs) are increasingly installed to treat pollutants from stormwater in urban areas, but few peer-reviewed studies have assessed their field-scale performance. The Filterra biofiltration unit is a box filter combining high-flow engineered media with potential for biological treatment from a planted tree. A Filterra device was monitored for its impact on hydrology and water quality of runoff from a 0.10-ha impervious watershed in Fayetteville, North Carolina, for 22 months. Undersizing of the system and clogging of the media bed likely caused 22% of runoff to bypass the system. Although peak flows were significantly reduced (p<0.0001) by a median 57% (likely owing to parking lot detention), postdevelopment peak flows were not consistently reduced to predevelopment flows. The Filterra provided stormwater treatment by significantly reducing event mean concentrations (EMCs) and total pollutant loadings for sediment (total suspended solids and suspended sediment concentration), nutrients (total phosphorus, total nitrogen, total ammoniacal nitrogen, and total Kjeldahl nitrogen), and zinc. Median EMC removal efficiency ranged from 35 to 97% and median loading efficiency was 39–80% for these pollutants. The device did not reduce nitrate/nitrite, total dissolved phosphorus, or copper. Nutrient concentrations of stormwater discharged from the Filterra generally met “good” water-quality thresholds established for the state of North Carolina and EMC targets established by the state of Washington for emergent MTDs. Clogging susceptibility and frequent maintenance of the Filterra unit were notable. Overall, results suggest the Filterra is an effective MTD for treating stormwater from small impervious watersheds.

ACS Style

Alessandra P. Smolek; Andrew R. Anderson; William F. Hunt. Hydrologic and Water-Quality Evaluation of a Rapid-Flow Biofiltration Device. Journal of Environmental Engineering 2018, 144, 05017010 .

AMA Style

Alessandra P. Smolek, Andrew R. Anderson, William F. Hunt. Hydrologic and Water-Quality Evaluation of a Rapid-Flow Biofiltration Device. Journal of Environmental Engineering. 2018; 144 (2):05017010.

Chicago/Turabian Style

Alessandra P. Smolek; Andrew R. Anderson; William F. Hunt. 2018. "Hydrologic and Water-Quality Evaluation of a Rapid-Flow Biofiltration Device." Journal of Environmental Engineering 144, no. 2: 05017010.

Case report
Published: 31 January 2018 in Water
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Standard roadside vegetated swales often do not provide consistent pollutant removal. To increase infiltration and pollutant removal, bioswales are designed with an underlying soil media and an underdrain. However, there are little data on the ability of these stormwater control measures (SCMs) to reduce pollutant concentrations. A bioswale treating road runoff was monitored, with volume-proportional, composite stormwater runoff samples taken for the inlet, overflow, and underdrain outflow. Samples were tested for total suspended solids (TSS), total volatile suspended solids (VSS), enterococcus, E. coli, and turbidity. Underdrain flow was significantly cleaner than untreated road runoff for all monitored pollutants. As expected, the water quality of overflow was not significantly improved, since little to no interaction with soils occurred for this portion of the water balance. However, overflow bacteria concentrations were similar to those from the underdrain perhaps due to a first flush of bacteria which was treated by the soil media. For all sampling locations, enterococci concentrations were always higher than the USEPA geometric mean recommendation of 35 Most Probable Number (MPN)/100 mL, but there were events where the fecal coliform concentrations was below the USEPA’s 200 MPN/100 mL limit. A reduction in TSS concentration was seen for both overflow and underdrain flow, and only the underdrain effluent concentrations were below the North Carolina’s high quality water limit of 20 mg/L. Comparing results herein to standard swales, the bioswale has the potential to provide greater treatment and become a popular tool.

ACS Style

Rebecca A. Purvis; Ryan J. Winston; William F. Hunt; Brian Lipscomb; Karthik Narayanaswamy; Andrew McDaniel; Matthew S. Lauffer; Susan Libes. Evaluating the Water Quality Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA. Water 2018, 10, 134 .

AMA Style

Rebecca A. Purvis, Ryan J. Winston, William F. Hunt, Brian Lipscomb, Karthik Narayanaswamy, Andrew McDaniel, Matthew S. Lauffer, Susan Libes. Evaluating the Water Quality Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA. Water. 2018; 10 (2):134.

Chicago/Turabian Style

Rebecca A. Purvis; Ryan J. Winston; William F. Hunt; Brian Lipscomb; Karthik Narayanaswamy; Andrew McDaniel; Matthew S. Lauffer; Susan Libes. 2018. "Evaluating the Water Quality Benefits of a Bioswale in Brunswick County, North Carolina (NC), USA." Water 10, no. 2: 134.

Journal article
Published: 03 January 2018 in Water
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Two stormwater control measures (SCMs) installed in series were monitored for their individual impact on the hydrology and water quality of stormwater runoff from a 0.08-hectare watershed in Fayetteville, North Carolina, for 22 months. Runoff was first treated by permeable interlocking concrete pavement (PICP), the underdrain of which discharged into a proprietary box filter (Filterra® biofiltration) which combined high-flow-engineered media with modest biological treatment from a planted tree. Due to a deteriorating contributing drainage area and high ratio of impervious area to permeable pavement area (2.6:1), clogging of the permeable pavement surface caused an estimated 38% of stormwater to bypass as surface runoff. Fifty-six percent of runoff volume infiltrated underlying soils, and the remaining 6% exited the Filterra® as treated effluent; the hydrologic benefit of the Filterra® was minimal, as expected. Primary treatment through the PICP significantly reduced event mean concentrations (EMCs) of total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), and total Kjeldahl nitrogen (TKN) but contributed to a significant increase in nitrate/nitrite (NO2,3–N) concentrations. Secondary treatment by the Filterra® further reduced TSS and TP concentrations and supplemented nitrogen removal such that treatment provided by the overall system was as follows: TSS (removal efficiency (RE): 96%), TP (RE: 75%), TN (RE: 42%), and TKN (RE: 51%). EMCs remained unchanged for NO2,3–N. Despite EMC reductions, additional load reduction due to the Filterra® was modest (less than 2%). This was because (1) a majority of pollutant load was removed via PICP exfiltration losses, and (2) nearly all of the export load was from untreated surface runoff, which bypassed the Filterra®, and therefore the manufactured device never had the opportunity to treat it. Cumulative load reductions (based only upon events with samples collected at each sampling location) were 69%, 60%, and 41% for TSS, TP, and TN, respectively. When surface runoff was excluded, load reductions increased to over 96%; lower run-on ratios (which would reduce clogging rate) and/or increased maintenance frequency might have improved pollutant load removal.

ACS Style

Alessandra S. Braswell; Andrew R. Anderson; William F. Hunt. Hydrologic and Water Quality Evaluation of a Permeable Pavement and Biofiltration Device in Series. Water 2018, 10, 33 .

AMA Style

Alessandra S. Braswell, Andrew R. Anderson, William F. Hunt. Hydrologic and Water Quality Evaluation of a Permeable Pavement and Biofiltration Device in Series. Water. 2018; 10 (1):33.

Chicago/Turabian Style

Alessandra S. Braswell; Andrew R. Anderson; William F. Hunt. 2018. "Hydrologic and Water Quality Evaluation of a Permeable Pavement and Biofiltration Device in Series." Water 10, no. 1: 33.

Journal article
Published: 01 December 2017 in Environmental Pollution
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Green streets are increasingly being used as a stormwater management strategy to mitigate stormwater runoff at its source while providing other environmental and societal benefits, including connecting pedestrians to the street. Simultaneously, human exposure to particulate matter from urban transportation is of major concern worldwide due to the proximity of pedestrians, drivers, and cyclists to the emission sources. Vegetation used for stormwater treatment can help designers limit the exposure of people to air pollutants. This goal can be achieved through the deliberate placement of green streets, along with strategic planting schemes that maximize pollutant dispersion. This communication presents general design considerations for green streets that combine stormwater management and air quality goals. There is currently limited guidance on designing green streets for air quality considerations; this is the first communication to offer suggestions and advice for the design of green stormwater streets in regards to their effects on air quality. Street characteristics including (1) the width to height ratio of the street to the buildings, (2) the type of trees and their location, and (3) any prevailing winds can have an impact on pollutant concentrations within the street and along sidewalks. Vegetation within stormwater control measures has the ability to reduce particulate matter concentrations; however, it must be carefully selected and placed within the green street to promote the dispersion of air flow.

ACS Style

Kathryn M. Shaneyfelt; Andrew R. Anderson; Prashant Kumar; William F. Hunt. Air quality considerations for stormwater green street design. Environmental Pollution 2017, 231, 768 -778.

AMA Style

Kathryn M. Shaneyfelt, Andrew R. Anderson, Prashant Kumar, William F. Hunt. Air quality considerations for stormwater green street design. Environmental Pollution. 2017; 231 ():768-778.

Chicago/Turabian Style

Kathryn M. Shaneyfelt; Andrew R. Anderson; Prashant Kumar; William F. Hunt. 2017. "Air quality considerations for stormwater green street design." Environmental Pollution 231, no. : 768-778.

Journal article
Published: 09 September 2017 in Water
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Across the globe, water quality standards have been implemented to protect receiving waters from stormwater pollution, motivating regulators (and consequently designers) to develop tools to predict the performance of stormwater control measures such as constructed stormwater wetlands (CSWs). The goal of this study was to determine how well the relaxed tanks-in-series (P-k-C*) model described the performance of CSWs in North Carolina. Storm events monitored at 10 CSWs in North Carolina were used for calibrating the model, and statistical evaluations concluded the model could adequately predict the performance for all pollutants except organic nitrogen. Nash–Sutcliff calibration/validation values were determined to be 0.72/0.78, 0.78/0.74, 0.91/0.87, 0.72/0.62, 0.88/0.73, and 0.91/0.63 for total nitrogen, total ammoniacal nitrogen, oxidized nitrogen, organic nitrogen, total phosphorus, and total suspended solids, respectively. Sensitivity analysis revealed only one calibration parameter with strong sensitivity, the Arrhenius coefficient (temperature dependent model coefficient). With this model, CSWs can be optimized to treat watershed-specific influent concentrations to meet effluent targets. In general, the current design technique used in North Carolina and many other locations (a first flush volume detention method) oversizes CSWs for water quality vis-à-vis the method herein, suggesting improved designs for water quality may be possible through scientifically-informed methods.

ACS Style

Laura S. Merriman; Jon M. Hathaway; Michael R. Burchell; William F. Hunt. Adapting the Relaxed Tanks-in-Series Model for Stormwater Wetland Water Quality Performance. Water 2017, 9, 691 .

AMA Style

Laura S. Merriman, Jon M. Hathaway, Michael R. Burchell, William F. Hunt. Adapting the Relaxed Tanks-in-Series Model for Stormwater Wetland Water Quality Performance. Water. 2017; 9 (9):691.

Chicago/Turabian Style

Laura S. Merriman; Jon M. Hathaway; Michael R. Burchell; William F. Hunt. 2017. "Adapting the Relaxed Tanks-in-Series Model for Stormwater Wetland Water Quality Performance." Water 9, no. 9: 691.

Journal article
Published: 01 September 2017 in Journal of Environmental Engineering
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ACS Style

Adrienne R. Cizek; William F. Hunt; Ryan J. Winston; Matthew S. Lauffer. Hydrologic Performance of Regenerative Stormwater Conveyance in the North Carolina Coastal Plain. Journal of Environmental Engineering 2017, 143, 05017003 .

AMA Style

Adrienne R. Cizek, William F. Hunt, Ryan J. Winston, Matthew S. Lauffer. Hydrologic Performance of Regenerative Stormwater Conveyance in the North Carolina Coastal Plain. Journal of Environmental Engineering. 2017; 143 (9):05017003.

Chicago/Turabian Style

Adrienne R. Cizek; William F. Hunt; Ryan J. Winston; Matthew S. Lauffer. 2017. "Hydrologic Performance of Regenerative Stormwater Conveyance in the North Carolina Coastal Plain." Journal of Environmental Engineering 143, no. 9: 05017003.

Journal article
Published: 01 June 2017 in Journal of Environmental Engineering
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ACS Style

Ahmed Mohammed Al-Rubaei; Laura S. Merriman; William F. Hunt; Maria Viklander; Jiri Marsalek; Godecke-Tobias Blecken. Survey of the Operational Status of 25 Swedish Municipal Stormwater Management Ponds. Journal of Environmental Engineering 2017, 143, 05017001 .

AMA Style

Ahmed Mohammed Al-Rubaei, Laura S. Merriman, William F. Hunt, Maria Viklander, Jiri Marsalek, Godecke-Tobias Blecken. Survey of the Operational Status of 25 Swedish Municipal Stormwater Management Ponds. Journal of Environmental Engineering. 2017; 143 (6):05017001.

Chicago/Turabian Style

Ahmed Mohammed Al-Rubaei; Laura S. Merriman; William F. Hunt; Maria Viklander; Jiri Marsalek; Godecke-Tobias Blecken. 2017. "Survey of the Operational Status of 25 Swedish Municipal Stormwater Management Ponds." Journal of Environmental Engineering 143, no. 6: 05017001.

Journal article
Published: 01 December 2016 in Journal of Environmental Management
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Bioretention cells (BRCs) are an increasingly popular Stormwater Control Measure used to mitigate the hydrologic and water quality impacts of urbanization. Previous BRC research has demonstrated a strong capacity for pollutant removal; however, long-term sequestration of pollutants within soil media can elevate concentrations to levels fostering environmental and human health risks. Soil media samples were collected from an 11 year-old BRC in Charlotte, NC, and analyzed for the accumulation and spatial distribution of zinc, copper, and phosphorus. Pollutant distribution varied significantly with respect to depth and ordinate distance from the BRC inlet. Zinc concentrations (0.9-228.6 mg kg(-1) soil) exceeded environmental thresholds and phosphorus concentrations (5.1-173.3 mg kg(-1) soil) increased from initial levels by a factor of seven; however, notable accumulation was restricted to the BRC forebay. Maximum zinc and copper concentrations in soil media did not exceed 1% of mandatory cleanup levels and with regular maintenance of the forebay, the effective life of BRC media should exceed the life of the developments they treat.

ACS Style

Jeffrey P. Johnson; William F. Hunt. Evaluating the spatial distribution of pollutants and associated maintenance requirements in an 11 year-old bioretention cell in urban Charlotte, NC. Journal of Environmental Management 2016, 184, 363 -370.

AMA Style

Jeffrey P. Johnson, William F. Hunt. Evaluating the spatial distribution of pollutants and associated maintenance requirements in an 11 year-old bioretention cell in urban Charlotte, NC. Journal of Environmental Management. 2016; 184 ():363-370.

Chicago/Turabian Style

Jeffrey P. Johnson; William F. Hunt. 2016. "Evaluating the spatial distribution of pollutants and associated maintenance requirements in an 11 year-old bioretention cell in urban Charlotte, NC." Journal of Environmental Management 184, no. : 363-370.

Journal article
Published: 01 October 2016 in Journal of Environmental Engineering
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Permeable pavements allow stormwater to pass through the pavement surface, filtering out sediment and debris; over time, regular preventative maintenance will be needed to maintain the pavement surface infiltration rate (IR). IR testing is commonly used to determine maintenance needs and frequencies. ASTM standard methods may be used to measure permeable pavement IR; however, these tests can take hours to complete and require infiltrometers not readily available to maintenance contractors. A simple infiltration test (SIT) has been devised which (1) is conducted using easily acquired materials, (2) has a larger surface area (i.e., more representative of average pavement conditions), and (3) requires, on average, 72% less time to conduct than the ASTM test. ASTM and SIT methods were compared by conducting a total of 873 IR tests at the same locations on 12 permeable pavements in North Carolina, Ohio, and Sweden. Results showed that (1) a segmented linear relationship related SIT and ASTM-measured IRs; (2) the SIT and ASTM tests predicted approximately the same IR up to 250 mm/min; (3) the larger surface area of the SIT reduced the variability in measurements (average 40% less) compared to the ASTM method. The SIT took one-quarter the time to run, on average, making this newly-devised tool more efficient when assessing IR than ASTM methods, potentially saving maintenance personnel time and money.

ACS Style

Ryan J. Winston; Ahmed Al-Rubaei; Godecke T. Blecken; William F. Hunt. A Simple Infiltration Test for Determination of Permeable Pavement Maintenance Needs. Journal of Environmental Engineering 2016, 142, 06016005 .

AMA Style

Ryan J. Winston, Ahmed Al-Rubaei, Godecke T. Blecken, William F. Hunt. A Simple Infiltration Test for Determination of Permeable Pavement Maintenance Needs. Journal of Environmental Engineering. 2016; 142 (10):06016005.

Chicago/Turabian Style

Ryan J. Winston; Ahmed Al-Rubaei; Godecke T. Blecken; William F. Hunt. 2016. "A Simple Infiltration Test for Determination of Permeable Pavement Maintenance Needs." Journal of Environmental Engineering 142, no. 10: 06016005.