Oil/Sand interceptors are typically installed in industrial and maintenance facilities. They are large-capacity, underground vaults designed to intercept and collect oil and sand in a wastewater flow and prevent it from reaching the sanitary sewer system. These vaults feature baffles and pipes that trap sediments and retain oils. When wastewater flows into the vault, it slows down, causing oils to float to the surface and solid material to sink to the bottom. The remaining wastewater flows freely from the vault to the treatment plant.

Olympus Technical Services was contracted by the Montana Department of Transportation (MDT) in early 2021 to clean an oil/sand interceptor at their maintenance facility in Cascade, Montana. The 1,000-gallon tank had accumulated 2-3 feet of sediment in one of its two chambers.

High-pressure water jets were used first to clean out a 20-foot floor drain and the line that ran from the drain to the oil/water separator. Petroleum products liberated from the drain in this process were captured with absorbent pads. We then brought in our 1,000-gallon liquid vac trailer to pump most of the water from the vault and employed our hydrovac to extract approximately three cubic yards of sediment from the vault. The recovered material was transferred to a bermed cell (constructed by MDT and lined by Olympus) where it could dry out and MDT could later characterize it for proper disposal.

The final step in this process was to restore the functionality of the oil/sand interceptor by refilling the vault with water.

Oil/Sand interceptors must be maintained and cleaned on a regular basis. Frequency is dependent upon the size of your system and the volume of oil and sediment generated. We recommend that you monitor how much sediment you have accumulated. If you observe your vault or tank to be half-full of sediment, it is time to call Olympus.

View of the oil/sand interceptor vault through the manhole
floor drain with grates removed
First step: Cleaning the floor drains
floor drain with a tube sticking out
Using high-pressure water jets to clean the line from the floor drain to the oil/sand interceptor
gray sludge in a plastic-lined cell
Bermed cell constructed by MDT and lined by Olympus for drying the recovered sediment
gray sludge being pumped out of a vac trailer into a holding cell
Pumping recovered sediment from our hydrovac to the temporary drying bed