An Environmental Management System roadmap (RMS) developed for AASHTO's EMS Workshop for State DOTs recommends the following stewardship practices in rest area planning. The main objective of the process is to consider environmental issues and opportunity areas in the design process and then to establish a process to routinely and consistently identify and implement pollution prevention and energy efficiency (P2/E2) opportunities in the operation and maintenance of rest areas. To do this, it is helpful to identify environmental issues and opportunity areas and prioritize. For example, desired environmental benefits and fiscal gains could include the following objectives: [N]

• Reduce energy costs. Rest areas average around $10,000/year for electricity and $7,000 for natural gas.
• Control chemicals/materials used in maintenance (e.g., cleaning products) and switch to "green" cleaners wherever possible. Each rest area requires 500 gallons per year of cleaners and 1,000 pounds per year of herbicides and pesticides.
• Reduce water consumption. Each rest area (lavatories, drinking water, and cleanup) uses an average of 1,000,000 gallons per year of water, DOT cost for treating well water or purchasing water averages $1.75 per 1,000 gallons.
• Reduce the number of and the potential for wastewater treatment upsets per month at each area's treatment facilities(e.g., discharge parameters not met).

A substantial amount of pollution prevention and energy efficiency (P2/E2) information has been developed by USEPA and Defense Department agencies. Among the DOTs, PennDOT has prepared a P2/E2 Guide identifying and characterizing the costs and benefits of various P2/E2 options.

The Washington State Roadside Manual describes environmental stewardship practices for parking area design as such: [N]

• Provide areas for snow storage requirements in parking area design.
• Adjust design to comply with local regulations and requirements.
• Design aisles and breaks in planting strips to provide for easy maintenance. Aisles should be wide enough to allow access by street sweepers. High points in corner areas will allow water to drain away from these locations so they do not collect water and leaves.
• Ensure environmental quality by addressing air, drinking water and noise concerns, watershed restoration, and preservation of habitats and public green spaces.
• Use transportation facilities to enhance community aesthetics by incorporating unique local features (scenic views, community neighborhoods, historic districts, cultural and natural resources, etc.) and providing focal points for communities through those facilities such as multimodal stations, pedestrian plazas, and parkways.

Vegetated/Bioinfiltration Swales in Parking Facility Design

• Integrate vegetated/bioinfiltration swales into the facility to collect and detain stormwater. These can be designed within planting islands and around the perimeter. These swales also serve as water quality filtration strips and can be an amenity on the site. Long, linear swales break up the large expanse of pavement, collect stormwater, and allow for tree planting. A minimum width of 10 feet is recommended for these planted swales. If curbing is not placed around the swale, stop blocks should be used for each parking space surrounding the swale to prevent vehicles from entering the swale. Rip soils in planting islands before adding soil amendments and plant materials and/or install subsurface drainage . See the EPA Bioretention websitefor information on design of planting islands within parking areas.
• Use on-site stormwater drainage to provide water for plants. For example, plant trees on the edges of swales in parking islands. Trees should be spaced a minimum of every 75 feet on center within the parking lot, and aligned with stall lines. If curbing is used around swales, regular gaps in the curbing should be provided to allow stormwater runoff to drain into the swale. The elevation of the swale in relation to the pavement should be low enough for water and debris to drain into the swale without continuous maintenance. However, these locations will require periodic maintenance to clear debris build-up .

Permeable Pavements

Consider vegetated pervious open grid-type parking stalls to allow infiltration of stormwater. These are most effective for peripheral or overflow parking. Alternative modular paving systems that can support long-term parking are available.

Porous Concrete Pavement

No-fines porous concrete pavement is an emerging technology that has been used in the eastern United States and in Europe for years. Costs are slightly higher (approximately 25 percent more) than for conventional Portland cement concrete pavement. However, because porous concrete pavement infiltrates water at 270 to 450 inches per hour per square foot (3-5 gallons per minute per square foot), stormwater detention facilities are usually not needed to mitigate those surfaces, thereby reducing costs for stormwater mitigation.

Porous concrete pavement uses large aggregate and Portland cement with an additive to slow the rate of evaporation of the mix during placement. The thickness of the pavement is greater than conventional concrete and is laid over an aggregate subbase in order to provide structural stability. Because of the large pore spaces (15 to 25 percent of the total volume), porous concrete pavement is more resistant to frost heave than conventional concrete pavement. With regular (4 times per year) vacuuming or blowing to remove fine materials that can clog the pore spaces, these systems can continue to infiltrate stormwater and last as long as conventional concrete pavement systems. Higher installation and maintenance costs might be balanced by savings in stormwater storage and treatment costs. Because these systems infiltrate water at high rates, they are not appropriate where pollutants, such as fluid drips are likely to occur and where ground water tables are close to the surface.

The large pore spaces may cause problems with people in spiked heels, or people with pointed-tip canes. For this reason the use of this system may be more appropriate on outlying areas. Information on pavements can be found in WSDOT's online engineering publication, the WSDOT Pavement Guide. [N]