Caltrans Storm Water Quality Study - Open and/or Gap Graded Asphalt Pavement Pilot Study

Client: California Department of Transportation

Prime Contractor: MACTEC

Locations: Salinas and Atascadero, California

Period of Performance: Ongoing since February 2007

Project Description: The Open and/or Gap Graded Asphalt Pavements (OGGAP) Stormwater Quality Project pilot study was planned to evaluate stormwater runoff water quality by comparing open-graded and gap-graded pavements to that of conventional (dense-graded) pavements. The overall objective of this project is to investigate the impacts of various types of asphalt pavement on water quality from:

• Rubberized Hot Mix Asphalt - Open Graded (RHMA-O)
• Open-Graded Friction Course (OGFC)
• Dense-Graded Hot Mix Asphalt (DGHMA)

The project includes eleven pilot study sites located statewide. Nine of the pilot study sites consist of two paired monitoring stations each: one overlay test station, and one control station. For the paired sites, the test stations consist of a freeway section with a relatively new pavement overlay (RHMA-O or OGFC), up to 5 years old. The test station is paired with a control station consisting of a nearby section of the same road, paved with conventional dense-graded pavement (DGHMA). An additional two pilot study sites consist of one test station of recently applied dense-graded pavement.

For this water quality monitoring pilot study, ADH, as a subcontractor, is responsible for three site locations within Caltrans District 5 including the Atascadero test and control sites, and the Salinas test site. After site selections were performed in 2006, twenty-one storm events have been monitored at the Atascadero test and control sites and twelve storms have been monitored at the Salinas site.

ADH Responsibilities:

• Site selection including thorough written and photographic documentation of proposed test and control sites throughout Caltrans districts 1 and 4.
• Preparation of Site Selection Technical Memoranda.
• Installation, maintenance and operation of automated, flow-weighted stormwater monitoring and sampling stations.
• Remote instrument communication for data acquisition and programming control.
• Storm event forecasting.
• Storm event monitoring including composite and grab sampling, field documentation, preparation and transfer of environmental samples to analytical laboratories.
• Side study of field filtration for dissolved metals analysis.
• Preparation of the Post Storm Technical Memoranda components.
• Equipment demobilization.
• Maintenance of site vegetation.
• Participation in semi-monthly project status meetings.
• Review and editorial comment for end of season monitoring reports.
• Senior review of statistical analysis methods for the comprehensive 2009 - 2010 annual monitoring report.