Here is some great information provided by Oregon REALTORS® about septic systems with sand filters :
Section 7 of the Form 2.9 On-site sewage addendum references the DEQ “Be Septic Smart” brochure and includes the language, “Buyer understands that owners of certain sewage systems, including sand filter systems permitted on or after January 2, 2014 and all alternative treatment technology systems are required by law to maintain an annual service contract with a certified maintenance provider.” This tip will help you get to that brochure, and understand what systems need that maintenance contract.
The “Be Septic Smart” brochure comes in two variations, Septic Smart for Homeowners, and Septic Smart for Home Buyers. Both can be found at: https://www.oregon.gov/deq/Residential/Pages/Septic-Smart.aspx.
The Oregon Septic Smart initiative is designed around giving Oregonians greater access to information about septic systems and giving Oregonians easier access to septic inspectors. Septic inspectors can be added to the SepticSmart Inspectors list, making it much easier for a home buyer or homeowner to find and contact the inspector.
Under guidance by the Oregon Department of Environmental Quality, owners of sand filter systems, pressurized distribution systems, recirculating gravel filters, and alternative technology systems, that were permitted before January 2, 2014, must have the septic tank and dosing tank inspected at least once a year for sludge and scum accumulation. If the sand filtration/recirculating gravel/pressurized distribution/alternative tech system was permitted on or after January 2, 2014, the owner must have an active service contract with a certified maintenance provider, must submit a copy of that service contract to DEQ before the system is installed, and must submit annual reports and annual evaluation fees to DEQ under OAR 340-071-0130(17) and OAR 340-071-0140(3).
The various septic systems that have additional maintenance requirements are defined as follows:
Sand filter systems: an alternative system that combines a septic tank or other treatment unit, a dosing system with effluent pump and controls or dosing siphon, piping and fittings, a sand filter, and an absorption facility to treat wastewater. The wastewater is pumped to the top of the sand filter and allowed to trickle down at a controlled pace, catching significant quantities of waste before the water gets to the native drainage soil. Sand filters are best used in areas where there is limited location for a drainage field, or where the soil is too porous to effectively treat water while draining [if the sludge goes through the soil too fast, untreated sludge may get to groundwater, which is bad.]
Pressurized distribution systems: a system that uniformly distributes septic tank or other treatment effluent under pressure in an absorption facility or treatment unit. It blasts the effluent evenly through the entire drainfield, ensuring rapid, even draining; whereas normal septic systems rely on gravity and may have areas where drainage is more concentrated.
Recirculating gravel filters: gravel filter wastewater treatment system where portions of the filtered effluent is mixed into the septic tank effluent to recirculate through the filter. These systems snatch some of the effluent through repeatedly running the wastewater through the same filter tank. The heavy stuff gets filtered over and over again until it gets cleaned, while the cleaner wastewaters gets discharged into the soil dispersal systems; reducing odors and contamination in the discharge.
Alternative technology systems: under OAR 340-071-0100(11), these are “an alternate system that incorporates aerobic and other treatment technologies or units not specifically described elsewhere in this division.” Basically, all the fancy space-age technology that isn’t otherwise described in the rules.