.htm_cmp_ice010_vbtn.gif){kind=small}
.htm_cmp_ice010_vbtn.gif){kind=small}
The septic tank is nothing more than a large settling chamber where semi-solid materials settle to the bottom of the tank (sludge) and buoyant materials such as greases, fats and paper products float on the liquid surface of the tank (scum). The septic tank is constructed out of either concrete, steel, fiberglass or polyvinyl chloride (PVC). All new septic tanks sold in Oregon maintain a minimum liquid capacity of 1,000 gallons. The 1,000 gallon septic tank has sufficient capacity to process effluent flows from a one bedroom to a four bedroom single family residence. Larger capacity septic tanks with liquid capacities exceeding 1,500 gallons are installed where wastewater flows exceed the discharges that would typically be discharged from a four bedroom maximum single family residence. Septic tanks predating an installation date of 1980 may have liquid capacities of 500 gallons, 750 gallons or 1,000 gallons.
The purpose of a septic tank is really quite simple. As previously stated, the septic tank is a large settling chamber. Primary, typically anaerobic (without oxygen), treatment of the effluent takes place in the septic tank. Plumbing fixtures in the structure served by a septic system discharge liquid and semi-solid wastes to the septic tank. Wastes, both liquid and semi-solid, are detained in the septic tank for approximately two to three days. This time period allows the semi-solid matter to settle to the bottom of the septic tank. Greases, fats, and other buoyant materials such as toilet paper accumulate on the liquid surface of the tank. A turbid, semi-clear zone of liquid referred to as effluent forms between the sludge and scum layers. The effluent is then discharged by gravity flow or by an effluent lift pump to either a pretreatment unit such as a sand filter or directly to the absorption field.
The septic tank is designed to detain and store solid and semi-solid matter as well as various buoyant materials. Over time, these materials will accumulate and build up in the septic tank. If the materials are allowed to accumulate for an excessively long period of time, they will eventually reduce the volume of the effluent zone in the septic tank. At this point sludge and scum can be discharged directly to the pretreatment unit or the absorption field. The discharge of these materials directly to a pretreatment unit or to the absorption field is the single leading cause of septic system failures in Tillamook County. Therefore, regular pumping of the septic tank which will remove these materials is required. The septic tank should be pumped at intervals of approximately four (4) years by a licensed septic tank pumper. Regular septic tank pumping is the cheapest form of insurance you can purchase that will guarantee the long term satisfactory operation of your septic system.
There are many types of septic tank additives on the market. Many claim to provide thorough cleaning of the septic tank which will result in the septic tank not requiring periodic pumping. Other products attest to their ability to enhance digestion of the septic tank contents by introducing bacteria or enzymes to the septic tank effluent. A great many of these products claim to be the only product available which will prevent a complete failure of the septic system from occurring. All these claims are simply unsubstantiated .
The septic tank is designed to operate satisfactorily with all the discharge components from the plumbing system of a commercial structure or a single family residence. The septic tank is designed to settle and remove materials from the effluent waste stream that could adversely effect a pretreatment unit or an absorption field. The septic tank is not designed to provide a high level of digestion and treatment of the effluent contained in the tank. In fact, the anaerobic environment of a septic tank is not conducive to the complete digestion and treatment of the effluent in the septic tank. The addition of chemical additives, bacterial additives or enzymes will not stimulate the chemical and biological properties inherent in the septic tank to digest and treat the effluent more efficiently. A recent study by the EPA clearly showed that septic tank additives are not effective in producing effluent discharges from septic tanks that were radically different than septic tanks into which no additives were introduced. Simply stated, do not waste your money on septic tank additives. Save the money you may spend on septic tank additives and use it to have the septic tank pumped every four (4) years by a licensed septic tank pumper.
Septic tank pumpers advertise in the phone directory Yellow Pages under Septic Tanks & Systems - Cleaning. The companies in this section of the Yellow Pages should all be licensed septic tank pumpers. Verification of a current septic tank pumping license can be obtained by calling the Tillamook County Community Development Department, On-Site Sanitation Division, phone number (503) 842-3409. The Tillamook County Community Development Department, On-Site Sanitation Division also maintains a current list of septic tank pumpers operating in Tillamook County. You can obtain this list by either visiting our office in the Tillamook County Courthouse, 201 Laurel Avenue, Tillamook, OR, contact us by phone at (503) 842-3409 or simply click pumper list for the list of septic tank pumpers providing services in Tillamook County.
There are no State statutes or administrative rules limiting the use of a garbage disposal when a septic system is used to process sewage wastes. However, it is strongly recommended that you do not use a garbage disposal when you discharge sewage wastes to a septic system. Excessive use of a garbage disposal can cause a septic system to prematurely fail. The septic system failure results from the garbage disposal discharging a finely ground mix of solid matter that will not completely settle in the septic tank. This fine material passes through the septic tank and then either completely clogs the distribution network of a pretreatment unit or clogs the distribution network of an absorption field.
If you do use a garbage disposal, use this unit sparingly. One suggestion to avoid the use of a garbage disposal would be to use a composting bin. Reuse of the compost wastes benefits not only the plants where the compost is spread but it also benefits the environment by reusing materials that could cause a septic system failure.
The absorption field is also called a drainfield, leachfield or subsurface disposal field. The absorption field consists of a series of trenches containing an approved drainfield media into which effluent is discharged from the septic tank. The approved drainfield media consists of either clean drainrock with the rock ranging in size from 3/4 inches to 2 1/2 inches, gravel-less PVC chambers or Styrofoam bundles. Trenches utilizing drainrock or Styrofoam bundles discharge effluent through a perforated pipe into the drainrock or the Styrofoam bundles and then into the soil. Trenches utilizing gravel-less PVC chambers discharge effluent directly through the chamber to the soil.
The purpose of the absorption field is to utilize the unsaturated portion of the soil to provide aerobic (with oxygen) treatment of the effluent through the chemical, physical, and biological properties of the soil. Viruses, parasitic worms, pathogenic microbial organisms and various chemicals and chemical compounds are effectively treated and removed by passage of the effluent through the unsaturated soil surrounding the absorption field trenches. Research has shown that the passage of effluent through as little as twelve inches of unsaturated soil removes all of the harmful constituents contained in the effluent. The effluent has been effectively cleansed leaving only water. The soil absorption field provides secondary and final treatment of the effluent discharged directly from a septic tank or tertiary and final treatment of effluent discharged from a pretreatment unit such as a sand filter.
A sand filter is an alternative type of septic system used to pretreat effluent discharged from a septic tank. The sand filter discharges the pretreated effluent to either an absorption field or directly below the sand filter unit itself. A sand filter that discharges effluent directly below the sand filter unit is called a bottomless sand filter. This type of sand filter is only used where rapidly draining soils such as sands or gravels are present. In either sand filter type, a very high quality (clean) effluent is discharged for final treatment in the soil. The sand filter represents a tertiary treatment system where primary treatment of the effluent occurs in the septic tank, secondary treatment of the effluent occurs in the sand filter, and tertiary treatment of the effluent occurs in the soil. The sand filter is used to insure that surface water and subsurface water resources are not adversely impacted by effluent discharges from a residence or a commercial structure. Parcels with soils that evidence high water tables, parcels that have rapidly draining soils overlying shallow water tables, parcels that are in close proximity to surface water bodies or parcels with limited development area are all potential candidates for the use of a sand filter system<.
A sand filter, in simple terms, is nothing more than a biological treatment unit that utilizes natural processes to treat and cleanse the effluent. Effluent that passes through a sand filter is broken down and consumed by aerobic bacteria that populate the individual sand grains of the medium sand in the sand filter. Additionally, the relatively large surface area of the individual sand grains in the medium sand provides an area of high ionic potential and an area which maintains a constant exchange site for gases and oxygen which facilitates the treatment and destruction of the constituent viral, biological and chemical compounds contained in effluent. In other words, a sand filter utilizes beneficial bacteria, oxygen, and chemical reactions to treat and purify the harmful components of the effluent.
This question is often asked as people compare a sand filter to an oil filter that a car utilizes to cleanse engine oil. The real truth, however, is that the sand filter is not really a filter but a biological treatment unit. A sand filter can operate for a considerable number of years if regular maintenance of the sand filter occurs. There are sand filters that have been operating in Tillamook County in excess of twenty years with no operational failures. Sand filters do, however, require regular maintenance to remain operational for extended periods of time. Regular maintenance is the periodic but regular pumping of the dosing septic tank by a licensed septic tank pumper, and a yearly inspection of the effluent pump components to determine if they are operating satisfactorily. All operational problems associated with a sand filter system must be corrected immediately to maintain the satisfactory operation of the sand filter system.
Sand filter systems are expensive. The high price associated with a sand filter system is due to the materials and system components required to construct the system and the amount of time it takes to build the system. A typical standard system takes approximately two (2) to three (3) days to construct while the alternative sand filter system can take seven (7) to fourteen (14) days to construct. The time it takes to construct a sand filter system increases the costs associated with equipment time necessary to build the system and equipment operator expenses.
Oregon Administrative Rules grant the legal parcel owner or a licensed septic system installer the authority to install a standard system or an alternative system such as a sand filter system once a permit has been issued for the construction of the system. It is strongly recommended, however, that you should not try to install a sand filter system yourself unless you have experience installing this type of system sometime in the recent past.
The requirements for submitting a complete set of sand filter plans are quite extensive. A handout is available from the Tillamook County Community Development Department, On-Site Sanitation Division that details the plan requirements for a sand filter system. After reviewing these plan requirements you will either grasp the complexity of their development or you will be unable to envision how the plans can be developed. If you are able to develop the required plans and specifications thereby allowing you to secure the construction installation permit, the next step is constructing the sand filter system. As previously stated, the sand filter system takes a considerable amount of time to build and requires special skills and abilities as well as specialized construction equipment to properly build the system. Any cost savings you might envision by building the sand filter system yourself, quickly disappear as you struggle to find and rent the right construction equipment, purchase the sand filter system components and then, if required construction inspections establish that the system components were incorrectly installed, correct the noted problems. It has been repeatedly experienced that owner installations of any type of septic system usually result in the system installation taking a considerable time to complete and the cost of installing the system amounting to a great deal more than the owner anticipated. It is, once again, strongly recommended that you seek the services of a licensed septic system installer to install a sand filter system.
Septic system installers advertise in the phone directory Yellow Pages under Septic Tanks & Systems - Contractors, Designers & Dealers. Most of the companies in this section of the Yellow Pages should all be licensed septic system installers. Verification of an installers current septic system installation license can be obtained by calling the Tillamook County Community Development Department, On-Site Sanitation Division, phone number (503) 842-3409. The Tillamook County Community Development Department, On-Site Sanitation Division also maintains a current list of licensed septic system installers operating in Tillamook County. You can obtain this list by visiting our office in the Tillamook County Courthouse, 201 Laurel Avenue, Tillamook, OR, contact us by phone at (503) 842-3409 or simply click installer list for a current list of Tillamook County licensed septic system installers.
A standard septic system is a system that has a septic tank that discharges effluent by either gravity flow or by an effluent pump discharging effluent under low pressure to an absorption field where the effluent is distributed to the absorption field trenches by gravity flow. The absorption field trenches contain a twelve (12) inch depth of drain media and the depth of the trenches, based upon soil and site conditions, ranges from a maximum depth of thirty-six (36) inches to a minimum depth of eighteen (18) inches.
The alternative septic system designation applies to all other septic systems that deviate from a standard septic system configuration. The alternative septic tank can discharge effluent by either gravity flow or by an effluent lift pump. A pretreatment unit, such as a sand filter, can be installed between the septic tank and the absorption field. The absorption trenches, depending on soil and site conditions, can contain drain media that ranges in depth from twelve (12) inches to thirty (30) inches. Gravel-less, shallow installation, low pressure distribution chambers can be installed, in some sand filter system installations, that have no drain media in the trenches and are no deeper than ten (10) inches below the ground surface. The minimum burial depth for an alternative septic system absorption trench, again depending upon soil and site conditions, can be ten (10) inches to the base of the trench and a maximum burial depth of forty-two (42) inches to the base of the absorption trench.
Tillamook County maintains a contract with the Oregon Department of Environmental Quality (DEQ) which enables personnel employed by the Tillamook County Community Development Department, On-Site Sanitation Division to administer and regulate the State mandated requirements for the installation of new and repair septic systems. Part of this administration and regulation is associated with the proper siting and installation of a septic system as it applies to the soil and site conditions within the parcel boundaries and directly surrounding the parcel boundaries of a proposed or existing development site.
Establishing the proper septic system for installation within the bounds of a parcel requires that test pits must be dug in the area of the proposed absorption field installation site. Oregon does not perform percolation tests for the installation of septic systems as is common in other states. Direct observation of the soil profile and close attention to features in the soil indicating where a water table perches along with a detailed mapping of the parcel are all utilized to establish the type of septic system that must be installed. The review and description of a soil profile is accomplished by personnel from the Tillamook County Community Development Department, On-Site Sanitation Division physically entering the test pits and describing the soils exposed on the side walls of the test pits. The test pits are usually dug by a backhoe and have minimum dimensions of two (2) feet wide by three (3) feet long by five (5) feet deep.