Stormwater Success Along the Neuse
Pioneering stormwater management techniques are used to clean up a North Carolina river.
The search for the cause of a series of fish kills in 1995 erupted in concern for water quality in North Carolina's Neuse River and its estuary. Nutrient loading, the toxic microbe Pfiesteria piscida, and other factors were linked to water degradation.
Studies rapidly evolved into action with the 1996 drafting of the Neuse River Nutrient Sensitive Waters Management Strategy. The "Neuse Rules" became the first basinwide strategy in North Carolina.
The state's Environmental Management Commission put the rules into effect on August 1, 1998. The first major goal—a 30% reduction in nitrogen loading by the year 2003—was met, and the Neuse River seems to be showing improvement.
"The general tendency for total nitrogen data in the Neuse River and estuary is a slight downward trend over the past five years," says Ken Reckhow, director of the University of North Carolina Water Resources Research Institute. There are various hypotheses as to why the decrease in nitrogen occurred, but, as Reckhow points out, it was likely caused by several factors.
Although agriculture continues to be the largest contributor of nitrogen within the Neuse basin, increased development and the associated urban stormwater issues also need to be acknowledged, explains Barbara Doll, North Carolina Sea Grant water-quality specialist. "In the upper reach of the Neuse Basin, you have to do something about stormwater management to have a positive effect," she says.
In addition to National Pollutant Discharge Elimination System (NPDES) Phase I and II rules, the Neuse stormwater rule—part of the Neuse Rules—targets 10 cities and five counties in the Neuse basin. Affected areas, working in cooperation with the North Carolina Division of Water Quality, have been required to develop a model stormwater plan to meet the objectives of the Neuse stormwater rule.
From there, local governments devised stormwater management plans for their individual municipalities. These plans were required to include a 30% nitrogen reduction goal for new developments—achieved through the use of best management practices (BMPs) and planning considerations, public education, identification and removal of illegal discharges, and identification of potential restoration projects.
In the Neuse River basin alone, a variety of approaches have been taken. Notable successes are apparent in places like the city of Kinston, the city of Smithfield, and the town of Cary. Because each community is unique in age, size, growth rate, or income, "all three communities represent a cross section of North Carolina urban municipalities," says Bill Hunt, a stormwater specialist in North Carolina State University's Biological and Agricultural Engineering Department. In other words, they are representative of the 15 jurisdictions affected by the Neuse legislation, Hunt explains. Therefore, these communities offer a diverse and applicable history regarding stormwater management—what works, what doesn't, and how other areas across the nation can learn from their experiences.
Smithfield Wetland Classroom
Johnston County—the fastest-growing county in North Carolina, with 47% of homes there having been built within the last 10 years—and the Town of Smithfield both recognize the need for innovative solutions to water-quality issues. The county's public utilities department initiated a water reclamation program even before the Neuse Rules, making an immediate, positive impact on the Neuse River. When the Neuse Rules came into debate and were finally implemented, stormwater management at a local level became a high priority.
 |
Because the Neuse Rules were the first basinwide rules in North Carolina, farmers and municipal leaders alike initially met them with apprehension. "It was a change from the status quo. They thought it meant new regulations that would increase their cost of production. It was different and it wasn't production-oriented," explains Kenneth Bateman, county extension director in Johnston County. Yet Bateman facilitated education efforts and gave credibility to a project that would encourage interest in extension activities in Smithfield and elsewhere: the Smithfield-Selma Senior High School Stormwater Wetland. An eyesore ditch filled with broken concrete, algae, and trash was transformed into an attractive wetland to treat runoff, reduce downstream flooding, and serve as an outdoor classroom at both the high school and university levels.
Nearly 26 acres of the high school campus watershed drains to the wetland, which removes pollutants, slows discharge of stormwater, and possibly limits downstream effects such as flooding and erosion.
According to Bateman, "It just wasn't one agency or organization. It became a networking venture for the board of education, the school and school administration, and the Town of Smithfield."
The partnership didn't end there, but continued to grow: the North Carolina Cooperative Extension Service (NCCES), the North Carolina State University Department of Biological and Agricultural Engineering (NC State BAE), and the Natural Resources Conservation Service also became involved.
Site plans for the wetland were created by NC State student Amy Lewis as part of her senior design project, under the guidance of Hunt. The North Carolina Division of Water Resources and the Neuse Education Team (NET), part of NCCES, provided $15,000 in funding.
Concerned about the amount of nutrient leaching that was coming off the high school campus, extension agents envisioned a double use for this wetland. "Our thoughts were that maybe we could use this to do some actual monitoring to see if we did have some leaching [of pollutants]," says Bateman.
The wetland is designed so that two underground storm drains provide almost continuous base flow. Three deep pools intercept groundwater in addition to stormwater and stay wet even during severe droughts. The goal is to force sheet flow of stormwater in order to expose the water to as much vegetation and microbial activity as possible before it flows into the receiving stream.
Twenty-nine species of native wetland plants were used to stabilize wetland soil and slow and treat stormwater. One foot of storage capacity within the wetland limits flooding in severe weather, but shallow water depths range from 1 to 6 inches at normal pool.
Data are collected by Bateman and analyzed by NC State graduate students through use of water samples, rain gauges, and computerized monitoring of water level, flow, and temperature.
According to Bill Lord, area environmental agent, studies have shown a drastic reduction in nitrate, total nitrogen, and total phosphorous concentrations as well as a temperature drop in stormwater that has been treated by the wetland. More than 20 pairs of inlet and outlet samples have been collected that show total phosphorous reductions of 94% and nitrate nitrogen reductions of 85%.
The project has not been without challenges, especially when "wetland" evoked images of a swamp—stagnant water full of mosquitoes and other health hazards. But through careful management and maintenance of a very diverse ecosystem—manipulation of water level, control of invasive cattails, stocking of mosquito fish—the wetland became established without a single mosquito larvae being spotted by Lord, a trained entomologist.
Educational benefits have warmed public perception of the wetland. This site has been the focus of a training session for stormwater professionals statewide, a workshop with North Carolina Department of Transportation engineers, and three international tours. "It's been of tremendous educational value to us in our stormwater program and to the school in its environmental biology program," says Lord.
When Ellen Ennis started teaching at the high school four years ago, there was one environmental science class offered, and it had only partial enrollment. Now there are eight classes, all full. "Students learn the difference between abiotic and biotic systems. They get to get out there and find out what is really alive," says Ennis.
Kinstonians Know "Best"
With industrial roots and a population just under 24,000, Kinston has a growth rate that is actually declining. "Our growth rate really hasn't had much influence over our stormwater program," says Stephen Miller, Kinston's water resources manager. "Our location dictated interest. It doesn't really matter what size your community is; water quality in the Neuse River is affected by everybody."
A 1998 Urban Stormwater Management Conference sponsored by NCCES, NC State BAE, and North Carolina Sea Grant inspired Kinston city officials, who were looking for ways to manage stormwater and educate the public.
"The pending rules we knew were coming, and we wanted to be able to show people that they weren't as scary as they sounded. We also wanted the positive press in being proactive," says Scott Stevens, Kinston's public services director.
Compliance with the Neuse Rules has generated a mixed response from developers. As Miller explains, overall watershed policy has led many regional developers to expect stormwater regulations, while local developers are surprised that Kinston is affected.
Kinston emphasizes public education through its cable access channel, public hearings, brochures, and participation in the Clean Water Education Partnership, which includes all governments that are required to meet the stormwater rules in the Neuse River Basin. Because it has limited resources, the partnerships Kinston established early—beginning with the 1998 conference and continuing with the installation of various BMP demonstration sites—have been a critical addition to regulations.
Kinston has installed three stormwater demonstration sites, firsts in eastern North Carolina: a rain garden, greenroof, and permeable parking lot.
Neuseway Rain Garden
Public perception of standing stormwater is often negative, but alternatives can be positive. Bioretention areas, or rain gardens, are very popular because they lack a permanent water body and are less likely to attract mosquitoes and other nuisances, Miller says. Rain gardens can be landscaped to blend into the surrounding surface features or planted to serve as a functional aesthetic feature.
Kinston installed the first rain garden in eastern North Carolina at the Neuseway Nature Center in 1998. It was designed by NC State faculty and built by Kinston city crews for public demonstration. Flooded by Hurricane Floyd and reconstructed in 1999, the roughly 450-square-foot rain garden now treats about 2,400 square feet of rooftop runoff.
The runoff is directed into the garden from the rooftop of an adjacent building via piping. The garden consists of a depression landscaped with trees, shrubs, and other water-tolerable plants; grass; and mulch overtop of the naturally sandy soil. The city horticulturist chose hydrophilic native plants that can withstand North Carolina weather.
According to Bill Ellis, Kinston/Lenoir Parks and Recreation Department director, the nature center chose to house the rain garden because of the simplicity of the idea, the low cost—roughly $1,500—and the fact that it fit the educational needs of the center. "It's been really positive. We've had a lot of news media coverage and we've had people say, 'Well, I can do that,'" says Ellis.
Neuseway Greenroof
"Greenroofs have the most potential in downtown high-land-cost areas where there isn't as much space," explains Amy Moran, NC State BAE graduate student and intern. An extensive greenroof, constructed in April 2002 atop the Neuseway Nature Center Planetarium, Health and Science Museum in Kinston, became one of the first greenroofs monitored for water quality in North America.
NC State BAE headed the early research efforts to study flood peak mitigation, water-quality improvement, and plant growth associated with two extensive greenroofs—one in Kinston and one in Goldsboro. Rainwater leaving the 290-square-foot greenroof in Kinston is compared to that of the conventional roofing on the building.
"The data collected at this site and its sister site in Goldsboro indicated 62% to 63% water retention," says Hunt. Test results show a decrease in runoff volumes and runoff peak flows associated with both greenroofs. The average peak flow reduction for both the Kinston and Goldsboro greenroofs was approximately 85%, according to a recent NC State BAE study conducted by Moran, Hunt, and Greg Jennings, BAE extension specialist and associate director of the Water Resources Research Institute.
An increase in nitrogen and phosphorous loads in runoff from these greenroofs has also been observed, which is bad news for the nutrient-sensitive Neuse River. Researchers believe that the increase in nutrients is connected with the planting medium used and the amount of compost it contains. "It means that more research needs to be done to try different types of media to see if other media do a better job of removing nutrients from stormwater runoff," explains Hunt.
The soil medium being used for the study is 4 inches deep, lightweight, and composed of a roof garden soil mix of 55% PermaTill, 30% US Golf Association rootzone sand, and 15% approved compost, according to Moran. With this specialized medium, specialized vegetation is required. Succulents—low-water-requirement plants—survive well in the hot, dry, desert-like conditions of the extensive greenroofs. Sedum and Delosperma species were planted. Maintenance requirements are limited. A gravel edging free of plants acts as a buffer zone between vegetated and non-vegetated areas.
A $5,000 mini-grant through NET funded the Kinston greenroof construction and research. American Hydrotech, Carolina Stalite, Emory Knoll Farms, NCCES, the City of Kinston/Lenoir County Parks and Recreation, and NC State BAE all provided either services or materials for free or at a reduced price. As a result, the cost of the Kinston greenroof was low—only about $4 per square foot—compared to the average extensive greenroof BMP that ranges from $8 to $15 per square foot. Those who participated were willing to aid in the greenroof construction because there was so little known about greenroof function and because the Nature Center welcomes approximately 60,000 visitors a year.
Hannibal Permeable Parking Lot
"Initial attempts at using permeable pavement in North Carolina and other states have been hindered primarily by maintenance issuesÖ. Careful engineering design and site selection were also lacking in initial applications, causing North Carolina to suspend any credit for using permeable pavement," according to an NC State Water Quality Group Newsletter issued in May 2001. The newsletter featured the permeable pavement parking lot in Kinston as a great working example of an effective permeable parking lot, despite the overall reputations of such lots as failing systems. The lot, located at the Alice Hannibal Building, has been of tremendous research and demonstrational value to stormwater professionals.
A universitywide extension grant of $20,000 was used to monitor, design, and partially construct the lot in 1999, with the city providing a match of labor and services. NC State students designed the lot as a senior engineering project under the direction of John Stone, associate professor of civil engineering.
The 9,340-square-foot permeable lot includes 26 parking stalls that receive limited levels of traffic—daily parking for city employees. Several factors made this site ideal for a permeable pavement installation: the low use of the lot; its location near the Neuse River; the hydraulic conductivity (8 inches per hour) of the existing soil at the site; and lack of a seasonally high water table—greater than 36 inches from the surface.
Twenty of the stalls are composed of a concrete block paver and the remaining six of plastic grid paver—all laid by hand. Both paver types were installed atop a 2-inch bedding sand layer, geofabric, and a uniformly graded rock layer composed of washed stone. The concrete block pavers were filled with concrete sand and the plastic grid pavers with sandy topsoil seeded with Bermuda grass.
The design of the lot continues to be fairly standard according to Hunt. "Things have changed in that the blocks tend to have smaller gaps, and instead of sand filling up gaps, pea gravel is used," Hunt notes of materials now available.
After construction, the lot was monitored for runoff for two years, from 1999 to 2001. "[Hurricanes] Dennis, Floyd, and Irene all passed over Kinston and pelted our lot with rain," says Hunt. "Over 50 storms that were at least half-an-inch fell over this lot" during the two-year monitoring period.
Rational coefficients, or runoff indicators, were determined for 2-inch and 4-inch storm sizes and ranged from 0.2 to 0.4 respectively, says Hunt. "This is a significant decrease from a standard rational coefficient (0.9 to 0.95) that is typically used for impermeable parking lots."
The state is using data from this research project to begin supporting a limited use of permeable pavement across eastern North Carolina. In addition, the research data collected, coupled with the public exposure gained through the media, tours, and the overall demonstrational aspects of the site, have encouraged similar lots to be constructed in places across the Neuse basin from Goldsboro to New Bern, says Hunt.
Costs to construct a permeable lot at the Hannibal building amounted to approximately 25% more than the usual asphalt lot, according to the NC State Water Quality Group. However, engineers should keep in mind the added benefit of stormwater treatment, as the ponds required with impervious surfaces may increase a developer's cost.
Retrofitting
Kinston has also identified potential restoration sites, including the wetland retrofit on the Lenoir County Boat Ramp on US 70. Construction of a boat ramp isolated a natural depression that could serve as a stormwater wetland. Runoff from both a parking lot and the boat ramp is collected by a trench drain that empties into the depression for treatment before the water reenters the Neuse River.
Costs were low and amounted only to the construction of the trench and the outlet pipe. Meanwhile, Kinston gained the addition of a pocket wetland in an opportune and previously developed area.
Kinston officials were able to do so much with BMPs because they proactively sought to host demonstration sites and identify retrofit sites. From the public services perspective, Stevens advises similar communities to "find those groups that have an interest in stormwater in your area, be it universities, extension services, or community colleges. Then work together to see what you can bring to the table."
The Town of Cary: Regulating High-Density Development
Named "most desirable place to live" in the East by Money magazine in 2003, Cary is a hot spot for developers. And with a median household income of $77,091—one of the highest in the state—Cary puts a boomtown twist on stormwater issues.
When you talk about stormwater regulations in Cary, you're really referring to an extensive web of regulations that began with the city's 1978 floodplain management ordinance, 1985 sediment and erosion control ordinance, 1982 watershed protection rules, 2000 buffer rules, and 2001 Neuse River stormwater rules. The web continues to grow as Cary awaits its stormwater permit under the NPDES Phase II rules. Similar regulations are found in other larger North Carolina communities.
Cary has been able to take state-issued regulations and use them to the benefit of the town. For instance, rather than relying on the state's erosion control regulations, Cary implemented a local program that would grant officials added control over compliance and enforcement activities. Also, state-enforced Neuse Basin buffer rules require 50-foot buffers for most streams. But in Cary, up to 100 feet of buffer may be required depending upon the stream. Residential lots cannot be platted into those buffers, which serves to protect the properties from the impacts of urban runoff.
"We chose to be more stringent to provide additional mitigation for environmental impacts," says Betsy Pearce, stormwater specialist in Cary's engineering department. "I don't know of anywhere else that's doing that [in the Neuse Basin]."
Cary predicts few problems when NPDES Phase II regulations come into effect in 2005. "The town has a very extensive land development ordinance. From a regulation standpoint, we have most of our bases covered," says Pearce.
The Neuse Rules dictated the development of such an ordinance. According to Tom Horstman, Cary erosion control supervisor, "The ordinance was written to be all-encompassing when Phase II kicked in." Cary soon will take further steps to expand all town ordinances to be applied townwide, specifically the watershed rules.
However, NPDES Phase II requirements will challenge Cary to meet public outreach standards that call for public meetings and stakeholder groups. So far, Cary has focused on townwide events, stormwater drain stenciling, and school demonstrations. The town is also a founding partner of the Clean Water Education Partnership. Despite education and outreach actions, a biannual survey conducted by the town showed that many citizens don't think about stormwater enough to know the most basic information. "The survey basically said that we have a way to go," says Pearce.
Cary is currently working to further its outreach program through the development of a demonstration bioretention area at the town-owned White Oak Park. While Cary is not yet required to retrofit, extra funds were available to retrofit an existing site.
BMP Magnitude and Variety
Cary's population reached 107,785 in April 2004. Stringent regulations have set the stage for the installation of roughly 100 BMPs in the town, with 50 more approved or in the process of being constructed. Now, almost every new development is required to house a stormwater BMP.
Once Cary engineers have looked over site plans and gone through an intensive documentation process with the developer to approve a BMP, the developer is required to post a maintenance bond. Thanks to documentation that clearly assigns responsibility to the developer, Cary has never had to tap into the reserve of money from the bonds. The town performs annual inspections of each BMP to ensure not only that the BMPs are being maintained and working properly, but also that the current landowners are aware of them, according to Horstman.
The sheer number of BMPs installed is connected with Cary's growth rate and regulations. "We're doing higher-density projects and still have a significant amount of projects, even with our fairly low growth rate," says Pearce.
Compared to five years ago, the developers' choice of BMPs has changed. "They are starting to use more bioretention areas, because they can use them in conjunction with their landscape buffers. They can get double use out of their land," notes Pearce. There is also a demand for constructed wetlands, because they have the highest nitrogen holding capacities. However, the public doesn't have much experience with them. "Sometimes they take a larger surface area, and people are more hesitant to have the standing water," says Pearce. But she expects to see more wetlands in the future.
Sand filters, level spreaders, and proprietary BMPs also contribute to the variety of BMPs installed in Cary. Level spreaders are required within the Neuse watershed when stormwater outlets flow into a buffer. They also may be used in conjunction with bioretention areas to diffuse the flow of runoff into the BMP, therefore decreasing erosion.
"The idea is to have a number of BMPs available for a designer to choose from," says Horstman. So far Cary has decided against creating a design manual because, according to Pearce, there's more freedom for the developer to design innovative BMPs. However, Pearce expects Cary to develop a manual in the near future that will influence BMP design, especially wet detention ponds, to encourage a more natural look.
In the past five years, developers' perceptions have also changed. According to Sea Grant's Doll, "People know that they've got to deal with stormwater. It's on the designs from the beginning. It's not as much of an afterthought as it used to be, and there's more diversity in the BMPs that they're using."
A Basinwide Effort
Smithfield, Kinston, and Cary have contributed to the solution, but the North Carolina city and towns are not alone in their efforts. "We have been successful in installing BMPs from Havelock to Durham and all the [targeted Neuse] cities in between," says Hunt, NC State engineer.
According to Doll, some cities need to do more. While Smithfield's wetland classroom and Kinston's demonstrational sites are both good working examples of education, and Cary has 100 or more BMPs in the ground, they aren't really successes until there is a mechanism to back the success of each BMP. "If there's no evaluation, no reporting, no regular checkup on these BMPs, then the benefits to other towns and cities is going to be limited," Doll explains.
Advertisement
Towns starting to develop stormwater plans can look to outside resources for examples and models. "The first thing I would do is go to Cary and say, 'Can I get your manual?' You don't have to start from scratch. Take something that they've done and maybe make some improvements," Doll suggests.
If the information the Neuse Basin and Phase II areas are using to control stormwater is compiled and made available to smaller communities, it will be of value on a much larger scale. So far, the information is being well-reported by many. BMP databases are often maintained within a town's stormwater department. The Internet has been essential in raising awareness—Cary maintains an extensive Web site tailored to the needs of both technical and general audiences. Extension-minded organizations—North Carolina Sea Grant and NCCES—continually work to provide online write-ups and issue newsletters featuring projects. Conferences such as "Neuse River Basin: Five Years of Progress" gather professionals from many different locations and arenas of stormwater management. And the idea of a BMP "demonstration" in itself is a giant step toward that larger-scale, big picture of water quality, without which individual efforts would be trivial.
Author's Bio: Lilly Loughner is an undergraduate student at North Carolina State University working as a writer/editor with North Carolina Sea Grant and the North Carolina Cooperative Extension in Raleigh.
November-December 2004
Stormwater Success Along the Neuse
Pioneering stormwater management techniques are used to clean up a North Carolina river.
The search for the cause of a series of fish kills in 1995 erupted in concern for water quality in North Carolina's Neuse River and its estuary. Nutrient loading, the toxic microbe Pfiesteria piscida, and other factors were linked to water degradation.Studies rapidly evolved into action with the 1996 drafting of the Neuse River Nutrient Sensitive Waters Management Strategy. The "Neuse Rules" became the first basinwide strategy in North Carolina.
The state's Environmental Management Commission put the rules into effect on August 1, 1998. The first major goal—a 30% reduction in nitrogen loading by the year 2003—was met, and the Neuse River seems to be showing improvement.
"The general tendency for total nitrogen data in the Neuse River and estuary is a slight downward trend over the past five years," says Ken Reckhow, director of the University of North Carolina Water Resources Research Institute. There are various hypotheses as to why the decrease in nitrogen occurred, but, as Reckhow points out, it was likely caused by several factors.
Although agriculture continues to be the largest contributor of nitrogen within the Neuse basin, increased development and the associated urban stormwater issues also need to be acknowledged, explains Barbara Doll, North Carolina Sea Grant water-quality specialist. "In the upper reach of the Neuse Basin, you have to do something about stormwater management to have a positive effect," she says.
In addition to National Pollutant Discharge Elimination System (NPDES) Phase I and II rules, the Neuse stormwater rule—part of the Neuse Rules—targets 10 cities and five counties in the Neuse basin. Affected areas, working in cooperation with the North Carolina Division of Water Quality, have been required to develop a model stormwater plan to meet the objectives of the Neuse stormwater rule.
From there, local governments devised stormwater management plans for their individual municipalities. These plans were required to include a 30% nitrogen reduction goal for new developments—achieved through the use of best management practices (BMPs) and planning considerations, public education, identification and removal of illegal discharges, and identification of potential restoration projects.
In the Neuse River basin alone, a variety of approaches have been taken. Notable successes are apparent in places like the city of Kinston, the city of Smithfield, and the town of Cary. Because each community is unique in age, size, growth rate, or income, "all three communities represent a cross section of North Carolina urban municipalities," says Bill Hunt, a stormwater specialist in North Carolina State University's Biological and Agricultural Engineering Department. In other words, they are representative of the 15 jurisdictions affected by the Neuse legislation, Hunt explains. Therefore, these communities offer a diverse and applicable history regarding stormwater management—what works, what doesn't, and how other areas across the nation can learn from their experiences.
Smithfield Wetland Classroom
Johnston County—the fastest-growing county in North Carolina, with 47% of homes there having been built within the last 10 years—and the Town of Smithfield both recognize the need for innovative solutions to water-quality issues. The county's public utilities department initiated a water reclamation program even before the Neuse Rules, making an immediate, positive impact on the Neuse River. When the Neuse Rules came into debate and were finally implemented, stormwater management at a local level became a high priority.
|
Because the Neuse Rules were the first basinwide rules in North Carolina, farmers and municipal leaders alike initially met them with apprehension. "It was a change from the status quo. They thought it meant new regulations that would increase their cost of production. It was different and it wasn't production-oriented," explains Kenneth Bateman, county extension director in Johnston County. Yet Bateman facilitated education efforts and gave credibility to a project that would encourage interest in extension activities in Smithfield and elsewhere: the Smithfield-Selma Senior High School Stormwater Wetland. An eyesore ditch filled with broken concrete, algae, and trash was transformed into an attractive wetland to treat runoff, reduce downstream flooding, and serve as an outdoor classroom at both the high school and university levels.
Nearly 26 acres of the high school campus watershed drains to the wetland, which removes pollutants, slows discharge of stormwater, and possibly limits downstream effects such as flooding and erosion.
According to Bateman, "It just wasn't one agency or organization. It became a networking venture for the board of education, the school and school administration, and the Town of Smithfield."
The partnership didn't end there, but continued to grow: the North Carolina Cooperative Extension Service (NCCES), the North Carolina State University Department of Biological and Agricultural Engineering (NC State BAE), and the Natural Resources Conservation Service also became involved.
Site plans for the wetland were created by NC State student Amy Lewis as part of her senior design project, under the guidance of Hunt. The North Carolina Division of Water Resources and the Neuse Education Team (NET), part of NCCES, provided $15,000 in funding.
Concerned about the amount of nutrient leaching that was coming off the high school campus, extension agents envisioned a double use for this wetland. "Our thoughts were that maybe we could use this to do some actual monitoring to see if we did have some leaching [of pollutants]," says Bateman.
The wetland is designed so that two underground storm drains provide almost continuous base flow. Three deep pools intercept groundwater in addition to stormwater and stay wet even during severe droughts. The goal is to force sheet flow of stormwater in order to expose the water to as much vegetation and microbial activity as possible before it flows into the receiving stream.
Twenty-nine species of native wetland plants were used to stabilize wetland soil and slow and treat stormwater. One foot of storage capacity within the wetland limits flooding in severe weather, but shallow water depths range from 1 to 6 inches at normal pool.
Data are collected by Bateman and analyzed by NC State graduate students through use of water samples, rain gauges, and computerized monitoring of water level, flow, and temperature.
According to Bill Lord, area environmental agent, studies have shown a drastic reduction in nitrate, total nitrogen, and total phosphorous concentrations as well as a temperature drop in stormwater that has been treated by the wetland. More than 20 pairs of inlet and outlet samples have been collected that show total phosphorous reductions of 94% and nitrate nitrogen reductions of 85%.
The project has not been without challenges, especially when "wetland" evoked images of a swamp—stagnant water full of mosquitoes and other health hazards. But through careful management and maintenance of a very diverse ecosystem—manipulation of water level, control of invasive cattails, stocking of mosquito fish—the wetland became established without a single mosquito larvae being spotted by Lord, a trained entomologist.
Educational benefits have warmed public perception of the wetland. This site has been the focus of a training session for stormwater professionals statewide, a workshop with North Carolina Department of Transportation engineers, and three international tours. "It's been of tremendous educational value to us in our stormwater program and to the school in its environmental biology program," says Lord.
When Ellen Ennis started teaching at the high school four years ago, there was one environmental science class offered, and it had only partial enrollment. Now there are eight classes, all full. "Students learn the difference between abiotic and biotic systems. They get to get out there and find out what is really alive," says Ennis.
Kinstonians Know "Best"
With industrial roots and a population just under 24,000, Kinston has a growth rate that is actually declining. "Our growth rate really hasn't had much influence over our stormwater program," says Stephen Miller, Kinston's water resources manager. "Our location dictated interest. It doesn't really matter what size your community is; water quality in the Neuse River is affected by everybody."
A 1998 Urban Stormwater Management Conference sponsored by NCCES, NC State BAE, and North Carolina Sea Grant inspired Kinston city officials, who were looking for ways to manage stormwater and educate the public.
"The pending rules we knew were coming, and we wanted to be able to show people that they weren't as scary as they sounded. We also wanted the positive press in being proactive," says Scott Stevens, Kinston's public services director.
Compliance with the Neuse Rules has generated a mixed response from developers. As Miller explains, overall watershed policy has led many regional developers to expect stormwater regulations, while local developers are surprised that Kinston is affected.
Kinston emphasizes public education through its cable access channel, public hearings, brochures, and participation in the Clean Water Education Partnership, which includes all governments that are required to meet the stormwater rules in the Neuse River Basin. Because it has limited resources, the partnerships Kinston established early—beginning with the 1998 conference and continuing with the installation of various BMP demonstration sites—have been a critical addition to regulations.
Kinston has installed three stormwater demonstration sites, firsts in eastern North Carolina: a rain garden, greenroof, and permeable parking lot.
Neuseway Rain Garden
Public perception of standing stormwater is often negative, but alternatives can be positive. Bioretention areas, or rain gardens, are very popular because they lack a permanent water body and are less likely to attract mosquitoes and other nuisances, Miller says. Rain gardens can be landscaped to blend into the surrounding surface features or planted to serve as a functional aesthetic feature.
Kinston installed the first rain garden in eastern North Carolina at the Neuseway Nature Center in 1998. It was designed by NC State faculty and built by Kinston city crews for public demonstration. Flooded by Hurricane Floyd and reconstructed in 1999, the roughly 450-square-foot rain garden now treats about 2,400 square feet of rooftop runoff.
The runoff is directed into the garden from the rooftop of an adjacent building via piping. The garden consists of a depression landscaped with trees, shrubs, and other water-tolerable plants; grass; and mulch overtop of the naturally sandy soil. The city horticulturist chose hydrophilic native plants that can withstand North Carolina weather.
According to Bill Ellis, Kinston/Lenoir Parks and Recreation Department director, the nature center chose to house the rain garden because of the simplicity of the idea, the low cost—roughly $1,500—and the fact that it fit the educational needs of the center. "It's been really positive. We've had a lot of news media coverage and we've had people say, 'Well, I can do that,'" says Ellis.
Neuseway Greenroof
"Greenroofs have the most potential in downtown high-land-cost areas where there isn't as much space," explains Amy Moran, NC State BAE graduate student and intern. An extensive greenroof, constructed in April 2002 atop the Neuseway Nature Center Planetarium, Health and Science Museum in Kinston, became one of the first greenroofs monitored for water quality in North America.
NC State BAE headed the early research efforts to study flood peak mitigation, water-quality improvement, and plant growth associated with two extensive greenroofs—one in Kinston and one in Goldsboro. Rainwater leaving the 290-square-foot greenroof in Kinston is compared to that of the conventional roofing on the building.
"The data collected at this site and its sister site in Goldsboro indicated 62% to 63% water retention," says Hunt. Test results show a decrease in runoff volumes and runoff peak flows associated with both greenroofs. The average peak flow reduction for both the Kinston and Goldsboro greenroofs was approximately 85%, according to a recent NC State BAE study conducted by Moran, Hunt, and Greg Jennings, BAE extension specialist and associate director of the Water Resources Research Institute.
An increase in nitrogen and phosphorous loads in runoff from these greenroofs has also been observed, which is bad news for the nutrient-sensitive Neuse River. Researchers believe that the increase in nutrients is connected with the planting medium used and the amount of compost it contains. "It means that more research needs to be done to try different types of media to see if other media do a better job of removing nutrients from stormwater runoff," explains Hunt.
The soil medium being used for the study is 4 inches deep, lightweight, and composed of a roof garden soil mix of 55% PermaTill, 30% US Golf Association rootzone sand, and 15% approved compost, according to Moran. With this specialized medium, specialized vegetation is required. Succulents—low-water-requirement plants—survive well in the hot, dry, desert-like conditions of the extensive greenroofs. Sedum and Delosperma species were planted. Maintenance requirements are limited. A gravel edging free of plants acts as a buffer zone between vegetated and non-vegetated areas.
A $5,000 mini-grant through NET funded the Kinston greenroof construction and research. American Hydrotech, Carolina Stalite, Emory Knoll Farms, NCCES, the City of Kinston/Lenoir County Parks and Recreation, and NC State BAE all provided either services or materials for free or at a reduced price. As a result, the cost of the Kinston greenroof was low—only about $4 per square foot—compared to the average extensive greenroof BMP that ranges from $8 to $15 per square foot. Those who participated were willing to aid in the greenroof construction because there was so little known about greenroof function and because the Nature Center welcomes approximately 60,000 visitors a year.
Hannibal Permeable Parking Lot
"Initial attempts at using permeable pavement in North Carolina and other states have been hindered primarily by maintenance issuesÖ. Careful engineering design and site selection were also lacking in initial applications, causing North Carolina to suspend any credit for using permeable pavement," according to an NC State Water Quality Group Newsletter issued in May 2001. The newsletter featured the permeable pavement parking lot in Kinston as a great working example of an effective permeable parking lot, despite the overall reputations of such lots as failing systems. The lot, located at the Alice Hannibal Building, has been of tremendous research and demonstrational value to stormwater professionals.
A universitywide extension grant of $20,000 was used to monitor, design, and partially construct the lot in 1999, with the city providing a match of labor and services. NC State students designed the lot as a senior engineering project under the direction of John Stone, associate professor of civil engineering.
The 9,340-square-foot permeable lot includes 26 parking stalls that receive limited levels of traffic—daily parking for city employees. Several factors made this site ideal for a permeable pavement installation: the low use of the lot; its location near the Neuse River; the hydraulic conductivity (8 inches per hour) of the existing soil at the site; and lack of a seasonally high water table—greater than 36 inches from the surface.
Twenty of the stalls are composed of a concrete block paver and the remaining six of plastic grid paver—all laid by hand. Both paver types were installed atop a 2-inch bedding sand layer, geofabric, and a uniformly graded rock layer composed of washed stone. The concrete block pavers were filled with concrete sand and the plastic grid pavers with sandy topsoil seeded with Bermuda grass.
The design of the lot continues to be fairly standard according to Hunt. "Things have changed in that the blocks tend to have smaller gaps, and instead of sand filling up gaps, pea gravel is used," Hunt notes of materials now available.
After construction, the lot was monitored for runoff for two years, from 1999 to 2001. "[Hurricanes] Dennis, Floyd, and Irene all passed over Kinston and pelted our lot with rain," says Hunt. "Over 50 storms that were at least half-an-inch fell over this lot" during the two-year monitoring period.
Rational coefficients, or runoff indicators, were determined for 2-inch and 4-inch storm sizes and ranged from 0.2 to 0.4 respectively, says Hunt. "This is a significant decrease from a standard rational coefficient (0.9 to 0.95) that is typically used for impermeable parking lots."
The state is using data from this research project to begin supporting a limited use of permeable pavement across eastern North Carolina. In addition, the research data collected, coupled with the public exposure gained through the media, tours, and the overall demonstrational aspects of the site, have encouraged similar lots to be constructed in places across the Neuse basin from Goldsboro to New Bern, says Hunt.
Costs to construct a permeable lot at the Hannibal building amounted to approximately 25% more than the usual asphalt lot, according to the NC State Water Quality Group. However, engineers should keep in mind the added benefit of stormwater treatment, as the ponds required with impervious surfaces may increase a developer's cost.
Retrofitting
Kinston has also identified potential restoration sites, including the wetland retrofit on the Lenoir County Boat Ramp on US 70. Construction of a boat ramp isolated a natural depression that could serve as a stormwater wetland. Runoff from both a parking lot and the boat ramp is collected by a trench drain that empties into the depression for treatment before the water reenters the Neuse River.
Costs were low and amounted only to the construction of the trench and the outlet pipe. Meanwhile, Kinston gained the addition of a pocket wetland in an opportune and previously developed area.
Kinston officials were able to do so much with BMPs because they proactively sought to host demonstration sites and identify retrofit sites. From the public services perspective, Stevens advises similar communities to "find those groups that have an interest in stormwater in your area, be it universities, extension services, or community colleges. Then work together to see what you can bring to the table."
The Town of Cary: Regulating High-Density Development
Named "most desirable place to live" in the East by Money magazine in 2003, Cary is a hot spot for developers. And with a median household income of $77,091—one of the highest in the state—Cary puts a boomtown twist on stormwater issues.
When you talk about stormwater regulations in Cary, you're really referring to an extensive web of regulations that began with the city's 1978 floodplain management ordinance, 1985 sediment and erosion control ordinance, 1982 watershed protection rules, 2000 buffer rules, and 2001 Neuse River stormwater rules. The web continues to grow as Cary awaits its stormwater permit under the NPDES Phase II rules. Similar regulations are found in other larger North Carolina communities.
Cary has been able to take state-issued regulations and use them to the benefit of the town. For instance, rather than relying on the state's erosion control regulations, Cary implemented a local program that would grant officials added control over compliance and enforcement activities. Also, state-enforced Neuse Basin buffer rules require 50-foot buffers for most streams. But in Cary, up to 100 feet of buffer may be required depending upon the stream. Residential lots cannot be platted into those buffers, which serves to protect the properties from the impacts of urban runoff.
"We chose to be more stringent to provide additional mitigation for environmental impacts," says Betsy Pearce, stormwater specialist in Cary's engineering department. "I don't know of anywhere else that's doing that [in the Neuse Basin]."
Cary predicts few problems when NPDES Phase II regulations come into effect in 2005. "The town has a very extensive land development ordinance. From a regulation standpoint, we have most of our bases covered," says Pearce.
The Neuse Rules dictated the development of such an ordinance. According to Tom Horstman, Cary erosion control supervisor, "The ordinance was written to be all-encompassing when Phase II kicked in." Cary soon will take further steps to expand all town ordinances to be applied townwide, specifically the watershed rules.
However, NPDES Phase II requirements will challenge Cary to meet public outreach standards that call for public meetings and stakeholder groups. So far, Cary has focused on townwide events, stormwater drain stenciling, and school demonstrations. The town is also a founding partner of the Clean Water Education Partnership. Despite education and outreach actions, a biannual survey conducted by the town showed that many citizens don't think about stormwater enough to know the most basic information. "The survey basically said that we have a way to go," says Pearce.
Cary is currently working to further its outreach program through the development of a demonstration bioretention area at the town-owned White Oak Park. While Cary is not yet required to retrofit, extra funds were available to retrofit an existing site.
BMP Magnitude and Variety
Cary's population reached 107,785 in April 2004. Stringent regulations have set the stage for the installation of roughly 100 BMPs in the town, with 50 more approved or in the process of being constructed. Now, almost every new development is required to house a stormwater BMP.
Once Cary engineers have looked over site plans and gone through an intensive documentation process with the developer to approve a BMP, the developer is required to post a maintenance bond. Thanks to documentation that clearly assigns responsibility to the developer, Cary has never had to tap into the reserve of money from the bonds. The town performs annual inspections of each BMP to ensure not only that the BMPs are being maintained and working properly, but also that the current landowners are aware of them, according to Horstman.
The sheer number of BMPs installed is connected with Cary's growth rate and regulations. "We're doing higher-density projects and still have a significant amount of projects, even with our fairly low growth rate," says Pearce.
Compared to five years ago, the developers' choice of BMPs has changed. "They are starting to use more bioretention areas, because they can use them in conjunction with their landscape buffers. They can get double use out of their land," notes Pearce. There is also a demand for constructed wetlands, because they have the highest nitrogen holding capacities. However, the public doesn't have much experience with them. "Sometimes they take a larger surface area, and people are more hesitant to have the standing water," says Pearce. But she expects to see more wetlands in the future.
Sand filters, level spreaders, and proprietary BMPs also contribute to the variety of BMPs installed in Cary. Level spreaders are required within the Neuse watershed when stormwater outlets flow into a buffer. They also may be used in conjunction with bioretention areas to diffuse the flow of runoff into the BMP, therefore decreasing erosion.
"The idea is to have a number of BMPs available for a designer to choose from," says Horstman. So far Cary has decided against creating a design manual because, according to Pearce, there's more freedom for the developer to design innovative BMPs. However, Pearce expects Cary to develop a manual in the near future that will influence BMP design, especially wet detention ponds, to encourage a more natural look.
In the past five years, developers' perceptions have also changed. According to Sea Grant's Doll, "People know that they've got to deal with stormwater. It's on the designs from the beginning. It's not as much of an afterthought as it used to be, and there's more diversity in the BMPs that they're using."
A Basinwide Effort
Smithfield, Kinston, and Cary have contributed to the solution, but the North Carolina city and towns are not alone in their efforts. "We have been successful in installing BMPs from Havelock to Durham and all the [targeted Neuse] cities in between," says Hunt, NC State engineer.
According to Doll, some cities need to do more. While Smithfield's wetland classroom and Kinston's demonstrational sites are both good working examples of education, and Cary has 100 or more BMPs in the ground, they aren't really successes until there is a mechanism to back the success of each BMP. "If there's no evaluation, no reporting, no regular checkup on these BMPs, then the benefits to other towns and cities is going to be limited," Doll explains.
Towns starting to develop stormwater plans can look to outside resources for examples and models. "The first thing I would do is go to Cary and say, 'Can I get your manual?' You don't have to start from scratch. Take something that they've done and maybe make some improvements," Doll suggests.
If the information the Neuse Basin and Phase II areas are using to control stormwater is compiled and made available to smaller communities, it will be of value on a much larger scale. So far, the information is being well-reported by many. BMP databases are often maintained within a town's stormwater department. The Internet has been essential in raising awareness—Cary maintains an extensive Web site tailored to the needs of both technical and general audiences. Extension-minded organizations—North Carolina Sea Grant and NCCES—continually work to provide online write-ups and issue newsletters featuring projects. Conferences such as "Neuse River Basin: Five Years of Progress" gather professionals from many different locations and arenas of stormwater management. And the idea of a BMP "demonstration" in itself is a giant step toward that larger-scale, big picture of water quality, without which individual efforts would be trivial.