DENVER -- Crews are packing a trench with clay to meet a deadline for completing an underground wall to hold back contaminated groundwater from an oil refinery.

Petroleum dissolved in groundwater beneath Suncor Energy near downtown Denver is continuing to seep into the bottom of Sand Creek near the confluence with the South Platte River and the company has until Thursday to complete the trench.

The pollution continues three months after state regulators ordered an intensified cleanup of northeastern Colorado's main waterway.

According to the Denver Post, Suncor Energy has also expanded a hose system blowing air bubbles into Sand Creek attempting to expel the pollution from the refinery.