A foreign substance of some kind can be seen floating atop water at the Philadelphia Navy Yard. (6ABC)

A leaking diesel fuel tank caused last week’s oil spill at the Philadelphia Navy Yard, in which approximately 100 gallons of diesel slid into the nearby Naval Reserve Basin.

The Aug. 3 spill activated the response of the U.S. Coast Guard, the Philadelphia Fire Department, and Navy 1, the Navy Yard’s fire department, according to PFD communications director Rachel Cunningham.

Lewis Environmental, an environmental services company, responded to clean up the spill, which the Coast Guard will continue to monitor, Coast Guard spokesperson Matthew West told Billy Penn.

“It is estimated 100 gallons of diesel fuel spilled into the basin, there are no major environmental sensitive areas in the immediate vicinity of the spill,” West said, adding that the faulty tank held a total of 275 gallons.

The Coast Guard believes the remaining diesel fuel will “naturally dissipate,” he said.

Officials said that none of the material entered either the Schuylkill River or the Delaware River.

Responders used a “hard and soft boom” at the 26th Street Bridge to prevent the diesel from spreading further, per West. Booms, which are long and cylindrical and float atop the water’s surface, are one of the more common tools used to contain oil spills, according to Elastec, an environmental product company. 

Oil-like substances in a body of water can expand along the surface. For example, 300 gallons of oil can spread to cover a 160-foot radius. The size of the spread also depends on the water’s surface tension and the thickness of the oil. When spilled in water, diesel can spread to a thin film, per the National Oceanic and Atmospheric Administration

Once a spill is contained, the oil can then be recovered from the surface, according to the Environmental Protection Agency.

The Navy Yard spill was contained pretty quickly, per authorities. It was first reported just before 9:30 a.m. last Thursday, and by 9:38 a.m. the PFD had declared the situation “under control,” meaning no additional resources were required. 

Billy Penn previously reported that the spill originated either from a faulty pump hose or a tanker that exceeded its fuel limit of 75k gallons.

The severity of harm from a spill depends on the type of oil, location, weather, season, and the clean-up process, according to NOAA. Spills can harm animals and habitats, and affect the local economy. While diesel can be highly toxic to fish, small spills in deeper, open waters dilute rather quickly and no fish kills have been reported in those situations.

Could this affect Philly drinking water?

There is no drinking water treatment plant near the Philadelphia Navy Yard.

Philly has three main drinking water plants. The Baxter treatment plant, which takes in water from the Delaware River, is located in Torresdale, according to The Philadelphia Inquirer.

What agencies were involved in responding?

The Fire Department’s hazmat team responded to the incident, but PFD was not the lead agency during this situation, Cunningham noted. The Pa. Dept. of Environmental Protection was also at the scene, she said.

PFD has special equipment to deal with various circumstances, meaning many agencies call them in to help with an incident, according to Cunningham.

Have spills happened on the Delaware River? How were they handled? 

The Navy Yard is located right where the Schuylkill River meets the Delaware River. Although officials say neither river was contaminated in the latest spill, oil has spilled into the Delaware water several times throughout history, with multiple instances in the 2000s. 

In 2015, 400 to 500 gallons of oil spilled near Wilmington and then washed up in New Jersey, but officials deemed it not a threat to the public.

Roughly a decade before that, more than 263k gallons of heavy oil spilled into the Delaware River after an oil tanker, Athos I, unknowingly ripped its outer body on an anchor. NOAA’s Office of Response and Restoration was deployed to conduct cleanup assessments, wildlife recoveries, and natural resource damages assessments. 

This story originally published Aug. 3 and has been updated.