Other Sponsored Research


Guam Septic Tank Survey

The Guam Septic Tank Survey project was assigned to WERI under the USEPA Revolving Fund in 2001. Guam law requires that unconnected buildings within 200 feet of existing sewer mains, or sewered buildings, be connected to the sewer system. The objective of this project was to identify buildings that were not connected to the existing sewer mains in order to implement the law. Over 13,000 buildings were manually surveyed over the entire island.


The Northern Guam Lens Aquifer (NGLA) supplies about 80% of Guam’s population with potable water. Protecting this vital resource from contaminants associated with domestic wastewater (e.g., nitrates and fecal coliform) is crucially important both from a public health and sustainable development perspective. Septic tanks and pit toilets are major sources of these contaminants, and several thousands of these are located right above the NGLA. It is estimated that septic tanks alone discharge around 5 million gallons of wastewater into the Guam environment each day. To what extent these facilities have impacted the chemical and biological integrity of the NGLA is currently unknown.

In completing this work, we gratefully acknowledge access to the Bureau of Statistics and Plans GIS data of Guam buildings with house tags, and GWA’s customer database. We are also indebted to GWA’s field personnel for technical assistance during the gathering of crucial GPS data that allowed us to join the data-bases.

The data for each village on island are summarized below in high-resolution downloadable pdf format.

Download PDF (2MB)

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