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PAVING THE WAY TO A “GREENER” CAMPUS: ALTERNATIVE PAVING MATERIALS FOR POLLUTION CONTROL AND AESTHETIC APPEAL
Impact/Purpose:
The purpose of the project will be to develop a cost-effective, sustainable design for parking areas sited on or near stream floodplains.
Description:
There were two major areas of focus in this project: a) determination of potential water quality improvements using sustainable paving alternatives and b) determination of potential aesthetic improvement by the use of the sustainable alternatives. In order to address both objectives, it was necessary to gather data that would help the team determine what paving and landscape methods would produce the most sustainable design solution. Throughout the P3 process, it was stressed to the team that they must use “scientific” methods to find the information that they needed to address both water quality and aesthetic aspects of the project.
Initially, water quantity delivered off a non-permeable, traditional asphalt paved surface was examined by the Hydrology laboratory class. After surveying a campus parking lot, it was found that for an area of approximately 1.3 acres (5300 square meters), a rainfall of 0.25 inches (0.635 cm) would deliver approximately 8800 gallons (33,500 liters) of runoff to Rock Creek. This was extrapolated to 1.05 MG (4.00 ML) per year based on 30-year average annual rainfall of 29.90 inches (75.95 cm).
One senior P3 student developed an independent research project specifically aimed at determining flow rates of water through several permeable paving materials: gravel, permeable asphalt and recycled high density polyethylene (HDPE) chips. The HDPE chips were scrap from a local sign company and were chosen as a possible recycled material to incorporate. Using a centrifugal pump and 15” diameter clear PVC cylinder apparatus modeled after Al-Darby (2006) and others, flow quantity and rate were measured to determine whether runoff to the creek could be reduced using one of these paving alternatives to encourage infiltration rather than runoff. Other materials could have been examined as well, but the use of locally-available materials enhances sustainability, so it was decided to use only materials available within the county for our project. These tests (Figures 1 and 2) illustrated how runoff could be reduced by Figures 1 and 2. Water flow rates (L/min) through HDPE plastic shavings, soil, stone and permeable asphalt, also showing reduced flow due to compaction after successive trials choosing a permeable paving material that allowed infiltration of water through the material rather than using traditional sealed concrete or asphalt which does not permit infiltration, but they also illustrate the importance of determining effective infiltration rates after compaction of materials when estimating how much runoff could be reduced. Each successive run had lower infiltration rates due to compaction regardless of the material being tested. Greatest rate of infiltration was achieved in the plastic chips, followed by soil, limestone gravel and porous asphalt.
The water permeability experiments also provided the opportunity to determine the effects of pavement choice on water quality. Samples of effluent that drained through the flow testing columns used to determine permeability of “virgin” paving materials were analyzed for organic compounds to simulated leaching of such compounds from a newly paved surface. Results of HPLC analysis by the Instrumental Analysis class (Table 2) using EPA method 550.1 proved to be interesting: slightly more polycyclic aromatic hydrocarbons were found in water samples that permeated Walmart-brand bagged topsoil only compared to samples that flowed through new permeable asphalt from a local paving company plus soil. Future studies should examine whether other soils also leach PAHs in similar concentrations, and/or whether the larger pore size in the permeable asphalt samples resulted in the lower PAH concentrations from those samples.
Actual metals deposited from vehicles onto one of the campus parking lots closest to Rock Creek were measured to determine a “first flush” level of contaminants from a rain event. Immediately after a rainfall event of 0.41 inches (1.04 cm), a water sample was collected directly from effluent pipes that delivered runoff from the existing parking lot to Rock Creek and was tested for metals concentrations. Students in the Water Pollution Analysis course collected and digested the sample and corresponding metals standards with nitric acid according to EPA method 200.0. The sample was then analyzed using ICP-MS. Metals found in greatest quantities were aluminum, iron, titanium and zinc (Table 3). However, several metals in the runoff (cadmium, copper, lead and zinc) were found to be in excess of the Ohio EPA aquatic life standard concentrations. These values suggest that methods to reduce these metals concentrations should be included in any sustainable design.
The US EPA extensively reviewed Best Management Practices (BMPs) for urban stormwater remediation, so the team referred to the document Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (USEPA, 2008) in order to choose appropriate sustainable alternatives to consider for this P3 project. Table 4 summarizes the BMPs selected for possible implementation. The P3 team also decided to consider a “hybrid” option not specifically included in the EPA BMP report. During literature review, the concept of “rain gardens” was encountered and the team members decided to further explore the installation of a wider variety of flowering plants in a vegetated swale or wetland. Two students in the Limnology class performed a four-week laboratory bench-scale experiment to test the tolerance of the aquatic plant Lizard Tail (Saururus cernuus) to power steering fluid and antifreeze. They observed that both wet weights and plant heights were reduced with concentrated exposure to these two fluids and determined that this native plant, typically found along the banks of Rock Creek, was negatively affected by exposure to either of these automotive fluids at concentrations of 10% or higher. The team discovered that careful selection of plant materials would be necessary to insure that any plants chosen would be tolerant of runoff contaminants from vehicles.
Campus stakeholders have realized the important financial connections between campus appearance and student, parent and alumni pride – an “attractive” campus increases financial benefits. In our designs, aesthetic components were also required to meet sustainability criteria before inclusion. Initially, we needed to determine whether aesthetic improvement in the existing parking lot was valued by campus users. The P3 students constructed Survey #1, consisting of 10 questions about perceptions of campus parking lots, which revealed that 54.4% of the 382 respondents thought that the appearance of a parking lot was important to them, while a slightly smaller number (41.1%) thought that the existing lots needed improvement and listed new pavement, increased greenery and additional lighting as some of the more common improvement responses. In addition, 30.1% of the respondents indicated that the view of adjacent Rock Creek as in need of improvement. The survey also queried whether recent campus beautification has improved the look of campus and 84% of the respondents agreed, citing flowers, trees, brick walkways, benches and gardens as the items they liked the most. A second survey was administered to 258 campus stakeholders to refine which kind of aesthetic improvements would be most valued for a parking lot redesign. Drawings of three sustainable design choices were displayed along with questions about viewer preferences. Over 70% of the respondents preferred designs that included aesthetic elements such as plants or garden structures over designs that featured gravel swales with no vegetation or structures. Stakeholders responded most strongly (76.5%) to one design that included perennial plants and shrubs and small decorative bridges crossing the swale inserts in the parking lot. As the campus community responses to two surveys illustrates, aesthetic additions such as vegetation and human-scale structures like benches, arbors and footbridges increase the visual appeal of paved parking lots.
Considerations of water quality effectiveness and aesthetics must also be balanced with installation and maintenance costs of chosen parking lot installations. The costs of various materials for possible use in the parking lot project were obtained from local suppliers so they could be factored in with other considerations (Table 5). It was not surprising that traditional asphalt or concrete paving choices were least expensive, but it was interesting to discover that vegetated swales and concrete paver systems were less expensive than either pervious asphalt or porous concrete on an annual cost basis.
