Arizona Construction Entrance Detail
Beautiful desert landscapes, Ponderosa Pine forests, rolling plains, and snowcapped mountains are right at home in the Grand Canyon State. The vast agricultural industry relies on the water quality of the lakes and reservoirs to support livestock and crops. Maintaining water quality is a shared goal for both residents and industry.
Arizona NPDES Stormwater Permits
In Arizona, the Department of Environmental Quality administers the NPDES established in the Clean Water Act and issues permits for stormwater discharges. Construction activities that disturb an area larger than an acre are issued a Construction General Permit or AZG2020-001 CGP. This permit authorizes stormwater discharges in accordance with state and federal regulations. As part of this regulation, strategies are implemented to reduce erosion, sedimentation, and stormwater contamination.
To apply for a Construction General Permit, an operator must create and submit a Stormwater Pollution Prevention Plan (SWPPP), which identifies potential pollution sources and outlines strategies that will be implemented to reduce pollutants from contaminating surface waters. Potential pollution sources include hazardous building materials, oils and fuels, plastics, and some natural pollutants, including metals contained in soils. Soil and dust, which are carried into surface water, can carry pollutants and cause harmful sedimentation. Sedimentation can increase the water temperature and decrease the amount of oxygen needed for aquatic life. The measures taken to prevent pollution, erosion, and sedimentation, called Best Management Practices (BMPs), are outlined in the SWPPP. The Department of Environmental Quality inspects the implementation of the SWPPP. It may require adjustments if the BMPs chosen are not sufficient to contain the dust and pollution generated from the construction project.
ADOT SC-10: Stabilized Construction Entrance/Exit Detail in Arizona
Construction Site egress points are required to use a stabilized construction entrance/exit to reduce roadway tracking. A construction entrance is designed to reduce sediment that is tracked out by vehicles onto roadways. The Arizona Department of Transportation (ADOT) has implemented a Statewide Stormwater Management Plan (SSWMP) to reduce erosion pollution for all DOT projects throughout the state. This SSWMP includes the Erosion and Pollution Control Manual which offers stabilized construction entrance detail as well as guidelines for maintenance and removal.
According to Sediment Control Section SC-10 of the Manual, a stabilized construction entrance/exit should consist of a layer of nonwoven, high survivability filter fabric below at least 6” of aggregate that is graded to allow drainage when necessary. The length should be no less than to allow four complete tire rotations of the largest vehicle that will be entering the jobsite. (Maricopa County standards specify 50’ of length in the EC-5: Stabilized Construction Entrance section of the Erosion Control manual.) Maintaining aggregate tracking pads involves redressing with additional stone when sediment builds up or the tracking pad becomes compacted. Regular street sweeping and cleaning is required to contain residual dust or sediment that is tracked onto the roadways.
Shaker plates, rumble strips and wheel washes are mentioned as additional measures to use in conjunction with aggregate pads when sediment is still being tracked onto roadways. The SC-10 Sediment control BMP is only effective at reducing dust and erosion pollution if all vehicle traffic is restricted to stabilized construction entrance/exit locations.
FODS Reusable Construction Entrances
FODS Construction Entrance/Exit mats are a reusable and rockless alternative to standard rock construction entrances. Unlike rumble strips and shaker plates, FODS are designed to completely replace rock and satisfy the stabilized construction entrance goals of removing mud from vehicle tires, minimizing sediment leaving the job site, and preventing rutting. Roadway tracking is reduced more effectively with FODS mats compared to aggregate tracking pads, which can result in as much as 59% reduction in street sweeping. Vehicles of all sizes can use the same entrance mats, which can be quickly installed over existing soil, concrete, or asphalt. The FODS system is well-suited for highway projects because the mats can be relocated throughout the project. Providing more effective sediment removal than aggregate, FODS allows contractors to lower their risk of fines and project delays. With an expected service life of over ten years, the FODS construction entrance provides industry-leading ROI.
