Caltrans Headquarters - Stormwater Quality Monitoring Program - Open/Gap Graded Asphalt Pavements (OGGAP) Stormwater Quality

Porous pavement conceptual design
Specialized runoff collection systems, accurate flow measurement devices coupled with...
...highly experienced staff to ensure valid BMP effectiveness testing
Prime Contractor: 
Location: 
Period of Performance: 
February, 2006 to July, 2011
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 was 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 included eleven pilot study sites located statewide. Nine of the pilot study sites consisted of two paired monitoring stations each: one overlay test station, and one control station. For the paired sites, the test stations consisted of a freeway section with a relatively new pavement overlay (RHMA-O or OGFC), up to 5 years old. The test station was 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 consisted of one test station of recently applied dense-graded pavement.

For this water quality monitoring pilot study, ADH, as a subcontractor, was responsible for three paired site stations and one single control site station within Caltrans Districts 1 and 5. ADH monitored sites in Willits, Boonville, Salinas and Atascadero. After site selections were performed in 2006, up to twenty-one storm events have been monitored at each paired 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, and sample handling
  • Side study of field filtration for dissolved metals analysis
  • Preparation of the post storm technical memoranda components
  • Equipment demobilization
  • Site decommissioning
  • 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 and 2010 – 2011 annual monitoring reports