The State of Hawaii Department of Transportation Stormwater Monitoring Program was implemented on January 1, 2001. The program includes the collection of rainfall, streamflow, and water-quality data at selected sites in the Halawa Stream drainage basin. Rainfall data were collected at two sites, and streamflow data were collected at 3 sites for the year July 1, 2001 to June 30, 2002. Water-quality data were collected at five sites, which include the three streamflow sites.

Six storms were sampled during the year July 1, 2001 to June 30, 2002, for a total of 44 samples. For each storm event, grab samples were collected nearly simultaneously at all five sites, and flow-weighted, time-composite samples were collected at the three sites equipped with automatic samplers. Samples were analyzed for nutrients, trace metals, oil and grease, total petroleum hydrocarbons, fecal coliform, biological oxygen demand, chemical oxygen demand, total suspended solids, and total dissolved solids. Quality assurance samples were also collected to verify analytical procedures and insure proper cleaning of equipment.