Report Number: 5
Year: 1978

Urban Runoff Pollutant Quality in Northern Guam

The purpose of this study was to obtain qualitative information on urban runoff in northern Guam. To accomplish this, runoff was collected over an 18-month period from ponding basins and storm drains and analyzed for common water quality parameters.

Results indicate that pollutant concentrations in ponding basins [on Guam] are relatively low in comparison to levels measured in other communities in the U.S., [although] moderate to high concentrations of oil, grease and soaps are occasionally measured at storm drain outlets emptying into ponding basins. Coliform bacteria levels are generally low with geometric means of 900 total coliform per 100 mL and 215 fecal coliform per 100 mL. However, total coliform counts range from near zero to several hundred thousand (106) per 100 mL, depending on rainfall occurrence and basin sampled.

Urban runoff being discharged into coastal waters is generally low in pollutants with the exception of nitrate-nitrogen (NO3-N) and coliform bacteria. Counts of bacteria in excess of the Guam Water Quality Standards established for Agana Bay shore waters were observed on most samplings. Groundwater seepage and tap water sources are the suspected source of the high nitrate-nitrogen concentrations (ranging up to 3.4 mg/L) which also exceed Guam Water Quality Standards.

William J. Zolan
Russell N. Clayshulte
Stephen J. Winter
James A. Marsh, Jr.
Reginald H.F. Young