Major Freeway Truck Stop

Issue: A truck stop is changing ownership, and the existing onsite sewage treatment system is noncompliant. The truck stop includes a full-service restaurant, convenience store and shower facilities. A major chain submarine shop will also be added. The onsite system includes 26,000 gallons in treatment tank capacity, a recirculating gravel filter and 16 septic mounds for soil dispersal. The recirculating filter is overwhelmed and nonfunctioning, and the mounds are noncompliant due to saturation and/or surfacing effluent. Flow averages about 6,700 GPD with influent BOD5 820-1,900 mg/L, FOG 41-220 mg/L, TSS 100-620 mg/L.

Action: Install a new 4,200-gallon grease trap and an MBD-12 aerator in one existing septic tank; add a new 10,000 gallon tank equipped with an MBD-8 aerator; abandon the recirculating filter; and install new pumps and valves for dosing the mounds.

Results: Year-end service provider report

• Average flow: 6,738 GPD
• Effluent CBOD: 24 mg/L
• Effluent TSS: 66 mg/L
• Effluent FOG: 5.61 mg/L