Every individual produces approximately 10 lb. of nitrogen, 3 lb. of phosphorus, and large quantities of bacteria, biochemical oxygen demand (BOD), and suspended solids in wastewater every year. For about 50% of the residents of North Carolina this wastewater is treated and disposed of by on-site wastewater systems (septic systems). The most common type of septic system used is the conventional or gravity flow system. This system is simple and has no moving parts, thus maintenance is limited to periodic pumping of the septic tank and visual inspection of the drainfield. The next most common systems generally require pumps. These systems assure better distribution of wastewater over the drainfield area, but they require additional maintenance and inspection in addition to that required by the conventional system. Overall, these systems, both conventional and pump, adequately remove bacteria, solids, and BOD from the wastewater when they are properly sited and maintained. However, even a properly functioning conventional gravity or pump system will introduce nutrients, particularly N, into the environment. In order to remove N from the wastewater, some advanced form of treatment is needed (sand filters, peat filters, aerobic treatment units). These systems rely on initial aerobic treatment to remove most of the bacteria and convert the NH4+-N present in the septic tank effluent to NO3--N. The NO3--N laden wastewater may then be partially recirculated into the anaerobic septic tank effluent in order to promote denitrification. These systems can remove 30 to 70% of the N in the wastewater. As with pump systems the advanced treatment systems require additional maintenance and monitoring in order to assure that they are functioning properly.
Presently, the siting and design of on-site systems is based on
individual site conditions with little regard for the surrounding environment
or potential cumulative environmental impacts. Years of research
have illustrated the treatment capabilities and environmental impacts of
numerous on-site systems. Therefore, it is possible to determine
how any given system will impact both public health and the environment
on a given site. The matching of system type to the environment and
site conditions represents an alternative to the traditional site
evaluation. This new approach relies upon a risk-based approach that
assesses site conditions, design and management, and overall environmental
risks. This approach begins by assessing the potential environmental
risk in terms of surface and ground water value and vulnerability to contamination.
Once the risk is assessed the degree of control or protection is assessed.
This step determines what siting criteria, treatment performance standards,
system inspection requirements, and environmental impact assessments will
be required. The periodic system inspection (including operation
and management) and environmental impact assessment will become the responsibility
of a local or regional management entity. This approach allows greater
flexibility in all stages of on-site wastewater management. This
flexibility stems from two components. First, it matches the system
type to the environment risk in order to minimize potential impacts.
Second, it requires ongoing assessment and maintenance of systems in order
to assure that proper treatment is maintained. The integration of
these two components assures that both public health and the environment
are protected.
The potential for reducing urban nitrogen and phosphorus loads using structural best management practices (BMPs) and innovative site planning techniques will be examined. The comparative nutrient removal capability of stormwater ponds, wetlands, filters and open channels will be summarized, based on a national review of urban BMP monitoring data. The existence of an “irreducible nutrient concentration” in the discharge of stormwater BMPs will be explored. Based on the performance data and simple urban loading models, approximate loading thresholds for watershed development are calculated. Beyond these thresholds, structural BMPs cannot “hold the line” on predevelopment nutrient loading, based on current technology.
This finding underscores the need to implement more innovative site
planning techniques at new development sites that reduce impervious cover
and conserve green space. These include narrower roads, smaller cul-de-sacs
and driveways, stream buffers, rooftop disconnection, bioretention and
open-space sub-divisions. The significant pollutant reduction that can
be achieved through these techniques will be illustrated by a case study
of the nutrient output from a conventional and innovative sub-division.
In addition, the case study will demonstrate the significant community,
economic and environmental benefits that occur when innovative site planning
techniques are employed.
In 1992 the Town Council appointed a Stormwater Management Committee to determine what stormwater management services the Town should be providing to the citizens of Chapel Hill. New State and Federal regulations regarding the quality of urban runoff as well as continuing concerns about flooding were the nucleus for establishing this Committee.
Over the past five years the Chapel Hill Water Quality Program has established a number of cost-effective projects and policies. The most noteworthy of these accomplishments are:
1. Completed a basic inventory of the Town’s Stormdrain Network, following
both the natural and man-made elements of the system.
2. Established a baseline inventory of stream bottom organisms (benthic
monitoring) as an initial indicator of stream health.
3. Established a Chemical, Physical, and Biological Stream Water Quality
Monitoring Program in coordination with Carrboro and U.N.C.
4. Organized student and citizen stream monitoring projects.
5. Coordinated periodic Stream Clean-up Projects with citizens, scouts,
and student volunteers.
6. Established a basic Public Education Program.
7. Established a Stormdrain Stenciling Program aimed at heightening
public awareness of the consequences of introducing pollutants into the
stormdrain system.
8. Created Geographic Information System (GIS) applications and coverages
for both natural and engineered drainage systems (as well as monitoring
results).
9. Through testing, observation, and analysis, determined the health
of our streams to be relatively good, and not posing chronic or significant
public health hazards.
10. Completed an initial stormwater runoff sampling effort to evaluate
the impacts of urbanization.
11. Stormwater Management Section 22 Study in conjunction with the
Army Corp of Engineers, Town of Carrboro, Orange County, and the University
of North Carolina at Chapel Hill. The purpose of this study is to
correlate water quantity and water quality with land use.
12. Final draft of a Drainage Assistance Program is being prepared.
The specific water quality programs and policies that will be addressed
during the conference include:
Nitrogen fertilizer applied to any land use can potentially impact water quality, including turf whether residential lawns or golf courses are potential sources of pollution. In the Neuse River, it is estimated that urban sources of nitrogen account for 8 % of the total load at New Bern. Nitrogen sources in urban areas derive from fertilizers applied to turf, pet waste, atmospheric deposition, and urban wildlife. In order to obtain a better picture of residential-lawn fertilization patterns, a fertilizer survey of Cary homeowners was conducted. Preliminary results from this survey will be presented, as will results from a paired watershed study that compared a golf course to a residential area.
In order to reduce nonpoint source (NPS) pollution derived from residential
and recreational landscape management, a number of new educational
initiatives are underway for homeowners in the Neuse River Basin.
One such initiative is a focus group survey, which is currently being conducted
throughout the Basin. The intent of the focus groups is to ascertain water
quality awareness, in order to better focus educational programs. Several
focus groups will be held on turf issues with focus-group participants
comprised of golf course superintendents, lawn care company owners
and operators, and homeowners. A 319 US Environmental Protection
Agency project in the Upper Neuse (Cary and Raleigh vicinity) is using
a neighbor-to-neighbor approach to transfer appropriate lawn care practices,
including water and nutrient management. Water quality monitoring
to characterize different urban land uses is an additional part of the
Upper
Neuse project. A similar 319 program is also being implemented
in the Lower Neuse Basin (New Bern area). The Neuse Education Team
has developed a traveling educational mobile unit. Activities associated
with this unit are providing homeowners information on appropriate nitrogen
fertilization rates and timing, as well as soil testing materials.
The North Carolina Cooperative Extension Service (NCCES) is developing
materials to assist Master Gardeners in answering lawn care questions so
that homeowners can have nice lawns and still protect water quality. The
NCCES, in association with the Turf Grass Council of North Carolina, is
developing an eight-part training program (including a section on nutrient
management) for professional turf managers. Participants will be
required to pass a test on each of the eight sections. A less rigorous
version of this educational program is being developed for retail personnel.
Nutrient management modules are currently being developed for applicators
applying fertilizer to 50 acres or more of either residential or recreational
turf. The educational programs developed for residential and recreational
turf management in the Neuse River Basin are targeted at reducing both
the sources as well as the transport of nitrogen into the Neuse River.