The U.S. military proposes to build independent wastewater systems to support base camp, munitions storage, and port activities on Tinian.
According to the draft environmental impact statement on live-fire training on Tinian and Pagan, these wastewater facilities will be built and maintained in accordance with CNMI regulations.
Right now, Tinian is unsewered. Most buildings use septic tanks. There are some decentralized collection and treat systems, like in the San Jose area, that lead to a central septic and leaching field system. The Tinian Dynasty Hotel and Casino owns the only treatment system that does not use a septic tank.
The EIS notes that the existing U.S. military septic tank and leaching field system on Tinian would not have adequate capacity for operations. Their largest wastewater needs would come from their base camp, which is proposed north of the Tinian airport.
The EIS describes an average daily wastewater flow of 47,052 gallons when no training is ongoing. Peak average flow is 51,327 gallons.
During “basic max training,” with up to 1,500 personnel, the EIS lists 122,052 gallons per day, with a peak of 238,827 gallons per day.
During surge training with up to 3,000 personnel, the EIS lists an average daily wastewater flow of 197,052 gallons per day, with a peak of 426,327 gallons per day.
Per CNMI regulations, any project above 5,000 gallons of wastewater flow a day would have to use technology other than a septic tank and leaching field.
CNMI regulations would also require the military to have secondary treatment, or sewer treatment.
But the EIS notes that a “critical issue” with the effluent, or sewage discharge, limits is the total nitrogen parameter, which the CNMI lists at a limit of 1.0 milligram. The EIS finds that is “lower than what is attainable using best available control technology.”
The EIS notes that CNMI regulatory agencies are aware of this issue and evaluates this on a case-by-case basis.
For the munitions storage area located outside the base camp, average wastewater flow would be 3,880 gallons per day.
Facilities at the Port of Tinian would treat industrial wastewater. This would come from the wash-down of vehicles, estimated at 12,000 gallons per day when the facility is in use.
This wastewater would flow into a sedimentation basin, followed by sand filtration system, before being discharged into a storm retention pond.