Sand/oil interceptors are in-ground tanks designed to capture dirt, sand, sweepings, minor petroleum spills, etc. from car washes and vehicle maintenance facilities to keep these substances out of our wastewater system. The interceptor treats these wastes by allowing substances lighter than water, such as oil, to float and substances heavier than water, such as sand, to sink. Only the grey water between these two zones should flow to the wastewater system.
What’s the problem?
If the sand/oil interceptor is not pumped frequently enough, the heavier dirt, sand, sweepings (sludge) and/or the lighter oil and grease will occupy too much space in the interceptor and be siphoned through the outlet pipe to the wastewater system.
Wastes can also backup into your wastewater service line and cause a blockage and/or odor problems. Additionally, sand/oil interceptors can overflow into the environment causing damage and bring about public health issues.
What are my responsibilities?
Inspect the sand/oil interceptor monthly to assure that it is pumped as needed to keep prohibited wastes out of the our wastewater system. See Section 12-5-702: Wastewater Discharge; Prohibitions in the Wastewater Treatment Code.
Immediately following pumping, make sure the “tee” on the outlet pipe of the sand/oil interceptor is present, that the “tee” is properly secured to the wall, and that no holes are present in the “tee” that might cause it to short circuit. The primary purpose of the “tee” is to trap floating materials from exiting the interceptor. See Section 12-5-804: Pretreatment Facilities; Operations in the Wastewater Treatment Code.
Sand/oil interceptor maintenance records must be kept on site for at least three years. Colorado Springs Utilities-Industrial Pretreatment or other authorized personnel may ask for these records. See Section 12-5-902: Records and Monitoring in the Wastewater Treatment Code.
The sludge from the sand/oil interceptor must be tested every three years by an accredited laboratory to ensure that it is not hazardous waste. In the event of a process change the test must be re-performed. Avoid using any chemicals that have hazardous characteristics.
Use a reliable and trustworthy hauler authorized to pump out sand/oil interceptors.
When should the sand/oil interceptor be pumped?
Due to differences in design and construction, sand/oil interceptors may have varying holding capacities. To prohibit wastes from siphoning through the outlet “tee” into the wastewater system, the bottom sludge layer or the floating materials layer shall not occupy a depth beyond eight inches from the bottom of the “tee”. The amount of waste in the sand/oil interceptor can be determined by using a “sludge judge” or long rod.
Remember: It costs you more money in the long run to wait until the last minute to have your sand/oil interceptor pumped. Pump it regularly.
Recommended best management practices (BMPs) to reduce pumping frequency
- Don’t wash spills into the sand/oil interceptor. Instead, use dry clean-up methods.
- Consider not having floor drains.
- Wash vehicles and engines less often.
- Filter solids out of the sand/oil interceptor using grates and screens over floor drains.
- Use reusable absorbent pads that absorb only floating oil and grease. Once saturated, squeeze the oil into your used oil drum.
- Use microbes to minimize the oil content in the sand/oil separator.
- Post signage near floor drains to remind employees to follow BMPs.