Septic Systems. A Buyer s & Seller s Guide. First American Title Insurance Company of Oregon

Transcription

1 Septic Systems A Buyer s & Seller s Guide First American Title Insurance Company of Oregon

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3 Created by Tod Hunt, Regional Marketing Manager Education Program Director Jackson & Josephine Counties First American Title Insurance Company of Oregon Medford, Oregon April 2006

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5 Table of Contents How Septic Systems Work pp 1-3 Septic Tank: Wastewater Separation p 2 Drainfield: Wastewater Distribution p 3 Locating System Components p 4 Septic System Inspection & Pumping p 5-7 Inspection Items p 5 Septic Tank Pumping pp 5-6 Septic Tank Inspection p 7 Installing a New System pp 8-19 Permit Process pp 8-10 Site Evaluation pp 8-9 Soil Evaluation pp 9-10 Construction & Installation Considerations pp Setback Requirements p 12 Drainfield Construction pp Sand Filter Systems pp Alternative Treatment Technology pp Preventative Maintenance pp Control Water Usage p 20 Drainfield Care pp Pools, Spas, Runoff & Softener Issues pp Stream Crossings p 24 System Alterations p 24 System Failure & Repair pp Signs of Septic System Failure p 25 Causes for System Failure pp 25-7 System Repair p 27 Contractors pp Site Development Plan Samples pp Index p 33 Acknowledgments p 34

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7 How Septic Systems Work Owning a Private Sewer System Do you know where the water goes when you empty a sink or flush a toilet? If your home is in a city, the wastewater goes into a municipal sewer system and to a sewage treatment plant. If your home is in a rural area or a small community, chances are your wastewater goes to your own private septic system. A septic system treats and disposes of your sewage right in your own yard. The septic system, if properly sited and when performing properly, safely treats and disposes of your sewage without creating any danger to your health or to the environment. Normally you don't have to worry about sewage in your yard. However, if the septic system is not functioning properly, there can be health concerns. Therefore, it is a good idea to understand how a septic system works and what you can do to make sure it continues to work properly. How A Septic System Works The purpose of on-site disposal systems is to provide for the treatment of household waste using natural processes. A septic system with an absorption field is the most common method for treating waste from a rural residence. A typical septic system has three main components: 1. a plumbing collection system 2. a septic tank 3. a drainfield Plumbing: Wastewater Collection All wastewater containing human wastes, nutrients, dirt, and other contaminants must be collected and delivered to the septic tank and drainfield for treatment and disposal. All water used in bathing, toilets, laundry, and dishwashing must be treated by the system. Drains allowing wastewater to enter the system should be equipped with strainers and other filtration devices to reduce the amount of food particles, hair, and lint entering the system. septic tank diversion box replacement area Some older homes may have been plumbed to bypass the septic tank with wash water but this has proven unsuccessful and damaging to drainfields. Oregon's rules require all wastewater to be treated. However, water from roof drains, basement drainage sump pumps, hot tubs, and swimming pools should not be put into the septic system. These large volumes of clean water will overload the system. Original and remodeled plumbing systems must be correctly designed and installed to allow trouble-free operation. Before remodeling, consider the impact of changes on the septic system ft. well soil absorption system

8 How Septic Systems Work Septic Tank: Wastewater Separation The purpose of the septic tank is to separate the solids from the liquids in the wastewater stream and to begin the process of breaking down contaminants. The tank is a buried, watertight container typically constructed of concrete, steel, fiberglass or polyethylene and can range in size from about 1,000 to 1,500 gallons or more. To give you an idea of how large this is, consider that up to 50 gallons of water fit in a standard bathtub and ordinary toilets use up to 3.5 gallons per flush. So, depending on the size of your household, it doesn't take too long to fill the septic tank. Two-chamber septic tank Most septic tanks have just one interior chamber into which the wastewater from your house enters; though a 2-chamber system will process influent more efficiently. When the influent enters the first chamber, its velocity slows so that the heavier solids can settle out of the water into the bottom of the chamber, and lighter materials can float to the surface. The accumulation of settled solids at the bottom of the tank is called sludge and the lighter solids (greases, fats and soaps) which form a mass on Courtesy of Landmark Inspection Service the surface of the liquid in the septic tank is called scum. In between the sludge and the scum is liquid waste or wastewater. Micro-organisms, like bacteria, and other natural processes act to decompose the waste materials in the liquid waste. Incoming water should be held in the tank for at least 24 hours in order to improve settling. Up to 50 percent of the solids will decompose into liquids and gases. Sludge and scum are also digested and compacted into a smaller volume. This is the first step in the process of purifying your household wastewater. When the first chamber of the tank becomes filled, the liquid waste begins to fill the second chamber. The chambers of the septic tank are designed to prevent the movement of sludge and scum to the second chamber, allowing only the movement of liquid. Once the second chamber is filled, and more influent enters the first chamber, an equal amount of the partly-treated liquid waste flows into the second chamber, while an equal amount flows out of the second chamber into the leaching bed or drainfield. The water flowing out into the leaching bed is called effluent. This is often referred to as primary treatment. Pathogens in the waste are NOT destroyed in the septic tank. Bacteria in the septic tank prepare the wastewater for final treatment in the drainfield. The separate chambers, a T-shaped outlet, and often screens in the septic tank prevent sludge and scum from leaving the tank and traveling into the drainfield area. Biological and chemical additives are not needed to aid or accelerate settling or decomposition. As a general rule, no solids other than human wastes and toilet paper should be flushed. 2

9 How Septic Systems Work The Drainfield: Wastewater Distribution The majority of the treatment of the wastewater occurs in the drainfield. A gridwork of perforated pipes or clay tiles in the leaching bed area evenly distributes the effluent over the natural soil or imported fill. Sometimes a distribution tank is used at the head of the pipes to more evenly distribute the effluent to the pipes. Gravel supports and forms an envelope around the pipe, to protect it from roots and burrowing animals. The perforations in the pipe allow the effluent to escape to the soil. Uncompacted, unsaturated, undisturbed soil must surround the soil treatment system. This system, typically referred to as secondary treatment, may be a series of trenches or a mound. As the effluent filters through the soil, microorganisms in the soil digest and remove the remaining impurities (such as suspended solids, organic chemicals and viruses and/or bacteria). There are millions of naturally-occurring beneficial microscopic organisms in every tablespoon of soil that kill disease-causing organisms in the sewage and remove nutrients. These beneficial bacteria in the soil need air to live. Therefore, a zone of unsaturated soil must be present below the drainfield for complete treatment. Courtesy of Landmark Inspection Service A biomat, or thin layer of fine solids, dead bacteria, and soil bacteria forms where the sewage meets the soil. This biomat layer regulates how fast liquid passes out of the trench or bed into the soil so the soil beneath the trench remains unsaturated. Once the wastewater is through the biomat layer and three feet of unsaturated soil, many harmful pathogens have been destroyed. Eventually, the purified water reaches the groundwater. If a soil has a high permeability or high water table, the effluent can reach the groundwater before it is fully treated. To avoid this, a shallow trench or mound system design is sometimes used. Both usually require a hydraulic pump to ensure uniform distribution of effluent over a field. As you can see, the operation of your septic system is fairly automatic and can work quite well by itself with very little maintenance required by the homeowner. Note the key words though, little maintenance, not no maintenance. 3

10 Locating Your System Components Finding Your System Most people have never seen their septic system, and if the system is properly maintained, most may never need to see it. A septic system is generally composed of two main parts: a watertight septic tank and a network of perforated pipes, called a tile bed, leaching bed or drainfield. All these parts are buried under your lawn so you may not even be aware of them. Yet, your septic system receives all the wastewater from your house, including toilets, showers, sinks, dishwasher, washing machine, etc. and purifies that water so it is safe to re-enter the ground water system. Locating Your Septic Tank & Drainfield plumbing vent Locating a tank, distribution box or drainfield can be difficult. You might see lids or manhole covers for your septic tank. Older tanks are often hard to find because there are no visible parts. septic tank groundwater leachfield/drainfield Effluent absorption and purification To locate your drainfield, look for clues such as shallow, parallel depressions, which may mark the drainfield trenches. It is unlikely that a drainfield could have been installed among large trees or in very rocky areas. If all that fails, you can contact your county health/sanitary department or the Department of Environmental Quality to see if they have a copy of the as-built drawing for the septic system for your home. The approved diagram would show where your septic system components are located. The quality and detail of as-built diagrams varies greatly. An older diagram, from before 1980, may be a very rough, simple sketch showing the layout of your system. Even if they do have a drawing on file, it probably will not match exactly what is in the ground, but it should be close. A newer diagram will show the tank, drainfield, reserve area (to be protected until the time when a replacement field is needed), and any other components of your system such as a pump chamber or mound. The size of the tank and length of the drainfield lines may also be noted. If you can find out who installed the system they should be able to tell you where everything is. Often a good contractor can tell where everything is just by the lay of the land. And if they can t spot it by eye, they have the tools to find them. Some even have small radio transmitters that they can flush down the drain and track as it goes through the system. Of course, once you have the pro find everything, you can mark it (there are small markers you can use to landmark the system) and know where everything is. 4

11 Septic System Inspections & Maintenance Proper Maintenance of Your System As a homeowner, you re responsible for the maintenance of your septic system. If properly designed, constructed and maintained, your septic system should provide long-term, effective treatment of household wastewater. A malfunctioning system is not only a health hazard to your family and your neighbors, but will likely harm surface and ground water resources, and cost you thousands of dollars to repair or replace. Keep in mind that when you sell your home, your septic system must be in good working order. Septic System Inspection You should have a typical system inspected at least every 3 years by a professional and your tank pumped as recommended by the inspector (generally every 3 to 5 years). An inspection should include: Locating the system Uncovering access holes Flushing the toilets Checking for signs of back up Measuring scum and sludge layers Identifying any leaks Inspecting mechanical components Pumping the tank if necessary Pumping the Tank Septic systems cannot dispose of all the material that enters the system. Solids that are not broken down by bacteria begin to accumulate in the septic tank and eventually need to be removed. As the septic system is used, sludge will build up in the bottom of the septic tank. The rate of the build-up will depend on the size of your tank (bigger is better), the volume of wastewater entering the tank, and the volume of solids in the wastewater stream. If the sludge is allowed to accumulate to the height of the outlet pipe, it could flow into the next chamber and then out into the tile bed. The pipes in the tile bed can become rapidly clogged by sludge. When the pipe is all blocked and the wastewater can no longer leach into the soil, it will seep to the surface of the ground, or worse yet, back up into your house. Not only can a clogged septic system be hazardous to the environment and to your family's health, it also represents a very expensive repair bill. Once the pipes become clogged, there is no quick fix; the entire system must be dug up and replaced. Properly designed tanks have enough capacity for three to eight years use before needing service. The tank should be checked each year starting with the third year to determine how much sludge is there. It is important to understand that septic tanks always appear full because both the inlet and the outlet are at the top of the tank. The homeowner needs to determine how much of the tank s volume is being taken up by solids, scum and sludge. When sludge and scum take up more than 35 percent of the tank volume, these solids need to be removed by pumping. 5

12 Septic System Inspections & Maintenance Pumping the Tank Pumping should be more frequent for a smaller tank, where more people are living in the house, and for houses with garbage disposals. Not only will this increase the capacity of the system by creating more room for the wastewater, but it will also prevent the sludge from entering the tile bed area. Older homes (built prior to 1974) may have a 500 or 750 gallon tank. The smallest approved tank size since 1974 is 1,000 gallons. Suggested Pumping Frequency (Years) Tank Size Household Size (No. of People) (gal.) It is recommended that you employ a septic tank pumper licensed by the Department of Environmental Quality (DEQ) to pump and clean your tank. This is primarily for homeowner safety, since septic systems produce harmful fumes and can be dangerous to clean for those not adequately prepared. Using qualified professionals also reduces the chance of improper monitoring or possible damage to the system during pumping. It is worth stressing again that it is much less expensive to maintain a system than to repair or replace it later. It is a good idea to supervise the cleaning to ensure that it is done properly. The material pumped out is known as septage. To get all of the material from the tank, the scum layer must be broken up and the sludge layers stirred up into the liquid portion of the tank. This is usually done by pumping liquid from the tank and reinjecting it into the bottom of the tank. The best time to clean out the tank is summer to early fall. At these times, the ground will not be frozen, allowing easier access to the tank, and the biological activity in the tank can re-establish itself before it gets too cold (micro-organisms like it warm). In the spring, hydrostatic pressure from an elevated water table the result of melted snow or heavy rainfall can sometimes create sufficient pressure on the underside of an empty tank to push it up out of the ground. This is more of a concern with lighter tanks made of polyethylene, fiberglass or steel. Single chamber septic tank Diagram Courtesy of the EPA 6

13 Septic System Inspections & Maintenance Inspecting Your Septic Tank All septic tanks should be checked on an annual basis to ensure they are working properly. Baffles, specially designed pipes which allow the sewage into and out of the tank, need to be checked to ensure they are not worn or damaged. The level of sludge (the material that accumulates at the bottom of the tank) needs to be measured to determine when the system should be pumped. Before closing the tank, check the condition of the tees or baffles. If they are missing or deteriorated, replace them with sanitary tees. Never enter a septic tank. Any work to replace the baffles or repair the tank should be made from the outside. The septic tank produces toxic gases which can kill a person in a matter of minutes. When working on a tank from the outside, make sure the area is well ventilated and someone is standing by. Never go into a septic tank to retrieve someone who was overcome by toxic gases or the lack of oxygen without a self-contained breathing apparatus. In the event someone falls into a septic tank the best thing to do is call for emergency service and put a fan at the top of the tank to blow in fresh air. To facilitate cleaning and inspection, install a watertight riser and a gasketed cover from the central service hole at least one inch above the surface before burying the tank. Do not bury the riser cover. Before You Buy Property Before you buy undeveloped property, ask if the property has been evaluated for a septic system. If not, have DEQ or a local government contract agent evaluate it for a septic system before purchase. When checking an existing septic system in a home you might want to buy, DEQ advises that you hire a qualified inspector to check out the system. Here are the main things to investigate: Is the system legal? Was it installed with a permit? Is the system the proper size to accommodate the needs of your family or business? How old is the system and has it been properly maintained? When was the septic tank last pumped? Have there been any problems in the past? Are all plumbing fixtures connected to the septic tank? How many people previously lived in the house? Are there signs of septic system failure such as soggy areas over the septic tank or drainfield areas? If you anticipate purchasing a property with intentions of making some changes in the use or size of the home, you may need to secure an Authorization Notice. This inspection procedure is performed when connecting or re-connecting to any existing septic system, when replacing one residence for another, rebuilding or replacing any structure, even if destroyed by fire or other natural disaster, when adding bedrooms or additional apartment facilities to an existing dwelling, connecting additional dwellings, or when any proposed change in use results in an increase to either sewage flow or waste strength. An Authorization Notice is usually not needed if you are adding more square footage, bathrooms, or garages. 7

14 Installing a Septic System Installing a New System The design and installation of a septic system is controlled by local and state rules through the permit process. The permit takes into consideration all specific site characteristics including the type of soil, size of house, and wastewater-contributing fixtures and appliances. The permitting process ensures that septic systems are sited and constructed so that human health and the environment are protected. In some counties DEQ administers the on-site program, while in other counties the County government administers the program as the agent for DEQ. The system must be installed by licensed contractors and inspected by qualified officials to ensure proper installation. Operation and maintenance of the system is the owner's responsibility. Contact the local responsible agency (planning and zoning, environmental services, etc.) with questions about local requirements. In Jackson County, contact Chuck Henke at In Josephine County, contact Chuck Costanzo at Permit Process Getting a new septic system installed is a two step process. The first step is to apply for a site evaluation. A septic system specialist will evaluate your property and identify the type of septic system needed and the best location for it. The second step is to apply for a septic system construction permit. Call your local DEQ office for application forms. There is a fee for a site evaluation as well as for the permit. Step 1: Site Evaluation A. Site Evaluation Criteria The suitability of a proposed site for a septic system is largely determined by the type and depth of soil and the depth to the water table. Other factors include the size of the property, how steep the site is, location of the system relative to streams, wells, cuts and fills, and whether sewer service is available. There must also be enough area available for a full system replacement in case the system fails. B. Site Evaluation Process 1. The Site Evaluation Application form must be completely filled out, signed by the owner or legally authorized representative, and submitted to the appropriate office along with the fee. A tax lot map, a detailed drawing of the proposed development, and directions to the property must be included. You must also provide at least 2 test pits at least 75 feet apart (more are necessary for large systems) in the proposed drainfield area. The specific requirements for test pits are provided with the Site Evaluation information packet. 2. After a completed application is received, an On-site Specialist will visit your property to perform the Site Evaluation. Depending on weather, test pit placement and if additional test pits need to be dug, more than one visit may be necessary. DEQ s goal is to respond to completed Site Evaluation applications within 3 weeks of receiving them however during the summer it may take up to 5 weeks. 8

15 Installing a Septic System B. Site Evaluation Process You will receive a Site Evaluation Report that specifies the approved area, the type and size of the septic system required and any special requirements. Should the site be rejected, you have 90 days in which you may provide additional test pits for evaluation with no additional fees. The Site Evaluation Report will also give you information such as applying for a site evaluation report review and the opportunity to apply for a variance from any rule or standard. Test Pits When you apply for a permit to construct an onsite sewage disposal system, a DEQ or County inspector will have to visit the proposed construction site. A test pit allows the inspector to test and examine the soil and soil layers and will help determine if it is appropriate to proceed with construction. This process is often referred to as a site evaluation. To provide for pit stabilization and safe access, standard test pits for site evaluations must be prepared in the following manner: The bottom of the pit shall be at least 2 feet wide and 4 feet long. The depth shall be at least 4.5 feet and shall not exceed 5 feet In some instances, pits need only be excavated to the layer of hard rock or to the water table if that layer is less than 5 feet. Soil Evaluation Soil is not only the foundation of your dwelling, but the foundation of wastewater treatment as well. Every site has unique soil characteristics that are critical in determining the size and type of system required. All soils are composed of sand, silt, clay, and some organic matter. The relative amount of each determines the soil's texture. Coarse soils are composed primarily of sand. They may also contain small amounts of fine gravel or rock. Intermediate soils are ones composed of a mixture of sand and silt. Soils composed primarily of clays are called fine soils. Soils are further classified into four basic structural groups. The four basic types of structure are: granular, platy, blocky, and prismatic. The structure of a soil, as well as the texture, determines the permeability of the soil. Underlying your site are several layers of soil composed of different minerals and amounts of organic matter. Each of the four soil structures has a specific location within these layers. These layers make up what is called the soil profile. In ordinary, undisturbed soil, the four types of structures are visible in this soil profile. Granular structures predominate on the top, followed in succession by platy, blocky, and finally prismatic structures. Below the topsoil and subsoil is the substratum. It is in the substratum where a limiting layer would exist. This layer of rock or very coarse sand limits the effectiveness of the absorption field. 9

16 Installing a Septic System Soil Evaluation There is much more to soil than just the inorganic particles that contribute to it. Soil can be thought of as a miniature ecosystem. The soil particles are surrounded by voids that can be filled with air or water. Soils are classified as well drained, moderately well drained, somewhat poorly drained, or poorly drained. Unsaturated soil is necessary to provide oxygen to promote chemical reactions or bacterial degradation. Therefore soils with groundwater that is at least 2-3 feet below the trenches are essential to promote proper treatment. The type of soil is also important. Soils such as sand allow the water to percolate downward. This will enhance treatment and prevent water from flow upward to the surface. Clay soils are less ideal, because the water does not flow as readily through it, and areas with shallow bedrock, do not allow the use of absorption fields at all. Step 2. The Permit A. Permit Criteria A Construction-Installation Permit is usually what is needed to install a septic system for a single-family dwelling or a system that has a projected sewage flow less than 2,500 gallons per day. This permit is valid for 1 year. For an additional fee it may be renewed or reinstated if it takes longer to complete construction and installation. If you have questions about permits for larger or more complex systems, contact DEQ at (503) or toll free in Oregon at (800) or the local Grants Pass DEQ at You must have a favorable Site Evaluation Report in order to apply for a Construction-Installation permit. A permit application packet can be obtained from the onsite agent for your county. B. Permit Process 1. To prevent a delay, fully complete the application, including the owner s or legally authorized representative s signature, and submit it along with the required fees. At a minimum, the following documents must be attached: A. A copy of the Site Evaluation Report. B. A Land Use Compatibility Statement signed by your county s land use agency. C. A vicinity/locator map. D. A detailed Site Development Plan and directions to the property. E. Detailed plans and specifications for the installation of the system. For Construction-Installation permitted systems, the plans must be drawn by the property owner or a DEQ-licensed installer. 10

17 Installing a Septic System Construction, Installation and Inspection 2. A Construction-Installation Permit will be issued within 20 days of receiving a completed application. Once you have the permit in hand, you may proceed with the installation of the septic system prescribed in the permit. Any changes must receive approval from the on-site agent for your county. Note: A septic system must be installed and constructed by the owner or a DEQ-licensed installer using DEQ-approved materials and equipment that meet minimum standards. All equipment must be installed and operated according to the manufacturer s specifications. If you have questions about installers or approved materials and equipment contact DEQ at or toll free in Oregon at A pre-cover inspection (before it is covered with soil) of the installation is required unless waived by the on-site agent for your county. Some complex systems, such as sand filter systems, require inspections at various stages of construction these requirements are specified in the permit. To initiate the pre-cover inspection the installer must complete the As-Built Drawing and Materials List form (included in the permit packet) and submit it to your county s on-site agent. This form must be signed by the installer certifying that it was installed according to DEQ specifications. Within seven (7) days of receipt of this completed form, the on-site agent for your county will either waive or conduct the inspection. After completion of a satisfactory inspection, you may cover the installation. You will be sent a Certificate of Satisfactory Completion (CSC) in the mail. Upon receipt of the CSC, you may begin using the septic system. The design, size, and location of a septic system are dependent on the characteristics of the site. These include topography, soil conditions, geology, and drainage. As the properties are identified, decisions regarding the design and construction can be made. Critical to the location of the absorption field is the topography of the site. A topographic profile shows the basic types of landforms. A contour map shows varying elevations in which each line represents a set elevation change. When locating the absorption field on the site, areas where water naturally converges should be avoided. Depressional areas and floodplains must be avoided since these areas may become saturated and be unable to adequately treat the effluent flow. A "useable area" of soil absorption should be located in an area of diverging flow. This area can be triangular, or trapezoidal in shape, but is most commonly rectangular. The larger the available area, the easier the system layout will be. 11

18 Installing a Septic System Constructing a Drainfield The absorption trenches should be placed perpendicular to the slope. Another way of saying this is that the trenches will be parallel to the contour lines. The exact slope of the site must be determined. Knowing the elevation change from the house to the absorption field is critical. If the field is located uphill from the house, hydraulic pumps will need to be included in the design. A complete layout of your site, including dimensions and locations of roads, buildings, neighboring residences, wells and drainage-ways, is needed before a septic system is designed. Setback Requirements Oregon code requires that the septic tank of a septic system must be located at least: 5 feet from any building 50 feet from any well or year-round body of water 5 feet from the property line 25 feet upgrade or 50 feet downgrade from an irrigation ditch Oregon code requires that the drain field of a septic system must be located at least: 10 feet from any building. 100 feet from any well or year-round body of water 10 feet from the property line 25 feet upgrade or 50 feet downgrade from an irrigation ditch 10 feet from any utility lines Other Pre-Construction Site Considerations After accounting for all of these separation distances, you can determine the useable area remaining. Don't forget to allow for any possible future construction. Don't place your drain field in a location that would be ideal for a pool, deck, basketball court, or some other future addition. Before any construction is allowed to proceed, precautions should be taken to ensure that the absorption site is protected from the compaction that might occur from construction traffic. Be sure to stake off and fence this area as well as an additional 90 feet down-slope. Under no circumstances should construction traffic be in this area. Nor should it be used for storage of construction materials. Even the backhoe used to construct the trenches can cause compaction if soil conditions are not ideal for construction. Dig from the upslope side! Before allowing construction to proceed, be sure that the soil is relatively dry. If the soil is too wet, construction will damage soil structure. This could cause the septic system to fail or function poorly. A good test for determining if the soil is too wet to excavate is to take a small amount and try to form a ribbon of soils in your hand. If the soil holds the ribbon when you open your hand, it is too wet to allow construction to proceed. If the soil crumbles and will not stay formed when you open your hand, then it is probably safe to allow construction to begin. 12

19 Installing a Septic System Excavate in the Dry Months It is best to plan the construction of your septic system to take place from the middle to late summer months. This is when the ground will generally be the driest and the water table be at its lowest. In the autumn the water table usually rises due to the fall rains. It may be difficult to find a time during the fall when the soil will be dry enough to work and the water table not so high that it floods the trench construction. During the winter, the water table may fall some from its fall level, but the soil is often too wet or even frozen to work. In the spring, the water table is often very high as a result of spring rains and runoff from thawing snow and ice. Do not plan construction for the spring unless an early and dry summer is expected. The Drainfield: Soil Treatment System Common terms for the soil treatment system are: drainfield, leachfield, subsurface disposal field, and soil absorption field. The soil treatment unit is where the final treatment and disposal of the septic tank effluent takes place. A properly sited, designed and installed soil treatment system will destroy most disease-causing pathogens and filter out the fine solids contained in the septic tank effluent. Leaching fields generally consist of a network of perforated pipes laid in a gravel-lined trench into which effluent is discharged from the septic tank. 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. 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. Drainfield Installations Site conditions and local requirements determine the soil treatment system for each site. If there is four feet of separation from the bottom of the disposal to the saturated soil, a gravity flow, standard system may be approved. A standard system is the least expensive sewage treatment system. Courtesy of Landmark Inspection Service 13

20 Installing a Septic System Conventional Trench System Drainfield trenches effectively treat liquid flowing from the septic tank. They are the most economical to install and are preferred when possible. A drainfield trench is a level excavation 18 to 36 inches wide. The depth of a trench can vary from one foot to a maximum of three feet and up to 100 feet long. The trench contains a perforated pipe in a bed of 3/4-inch to 2-inch diameter rock covered by natural or synthetic permeable fibers. Some soil treatment systems use large plastic tubing or some other chamber wrapped with fabric in the trench in place of rock. A 6 to 12-inch deep layer of topsoil covers the trench. Parallel trenches are used to ensure adequate treatment and are generally 10 feet apart from center to center. A typical bed is about fifteen feet in width. Sewage flows through the holes in the distribution pipe, to the rock (or tube), through the biomat, and into the soil. Bacteria and fine sewage solids are removed or destroyed in this process. Courtesy of Landmark Inspection Service The trench system may be laid out in one of many configurations including serial and equal distribution methods to allow for the necessary square feet of surface. The ground surface level of the soil treatment area should always be level or slightly raised above the surrounding ground to avoid excess rainfall flooding the system. Proper design and installation of the field is critical to ensuring proper and complete treatment. Professional installers licensed by the state must be used to design the entire septic system. The soils are examined by a local DEQ or county agent to ensure that the soils are appropriate for use of the field system. Proper design requires that an additional reserve or repair area be set aside in case the current system fails. Some counties may also require the installation of the additional field. Diagram courtesy of Oregon Department of Environmental Quality Distribution System Each site has a unique shape and slope. The soil type, percolation rate, water volume to be treated, and other factors determine how large an area is needed to properly treat sewage. To provide the necessary area, the design may be a series of many pipes, or "stepped" down a slope. The distribution of effluent into the soil treatment system is accomplished using drop boxes and diversion or distribution boxes. 14

21 Installing a Septic System Sand Filter Systems Septic tanks with soil absorption systems are the most commonly used wastewater treatment system in rural and suburban areas. Unfortunately, in many rural areas of Oregon, soil and site conditions make it impossible to use a conventional subsurface soil absorption system for wastewater treatment and disposal. On these problem sites, sand filter systems may be an alternative. A single-pass sand filter system pre-treats septic tank effluent by filtering it through sand before sending it to a soil treatment system. Various sand filter types and designs have been extensively tested and used in the United States. Other wastewater treatment filters use peat, pea gravel, crushed glass, or other experimental media, but sand is the best understood and the most predictable. Treatment mechanisms in a sand filter include physical filtering of solids, ion exchange (alteration of compounds by binding and releasing their components), and decomposition of organic waste by soil-dwelling bacteria. A properly operating sand filter should produce high-quality effluent with less than 20 mg/liter BOD (biological oxygen demand, a measure of organic material), less than 20 mg/liter TSS (total suspended solids), and less than 200 cfu/100 ml fecal coliform bacteria, an indicator of viruses and pathogens. Raised sand filter bed Sand filter system construction Septic tank pump tank Sand filter pump tank Distribution system Since wastewater leaves a sand filter system as high-quality effluent, the soil in the trench or mound soil treatment system may be better able to accept it, and the system should last longer. Because sand filters produce cleaner wastewater, they are useful for sites that are small; and for sites that are environmentally sensitive like those near lakes, in shallow bedrock areas, aquifer recharge areas, and wellhead protection areas. Pretreatment may allow a reduction in the separation required between the soil treatment system and the limiting soil layer. Sand filter enhanced septic system Sand filter systems may also be successfully retrofitted into conventional trench drainfields that have failed because of excessive organic loading from lack of maintenance. 15

22 Installing a Septic System How Sand Filter Systems Work Sewage flows from the house into one or several septic tanks, depending upon the size of the house and local requirements. Effluent from the septic tank(s) flows into a pump or lift tank. A pump introduces the effluent at the top of the sand filter, using pressure distribution to apply the wastewater evenly to the filter surface to maximize treatment. A timer can be used to dose the entire surface of the filter intermittently with wastewater. This draws oxygen from the atmosphere through the sand medium and its attached microbial community. The effluent is treated by physical, chemical, and biological processes. Suspended solids are removed by mechanical straining due to enhanced contact and sedimentation. Treatment occurs through the bacteria that colonize in the sand grains. Microorganisms use the organic matter and nutrients in the effluent for growth and reproduction. Intermittent Sand Filter With an Intermittent Sand Filter, effluent is applied in intermittent doses to a bed of sand or other suitable media. The ISF system is a one-pass system, meaning that the effluent percolates through the sand media just once before it is passed onto the drainfield for the tertiary and final treatment. The dosage, delivered at either a timed interval or on demand, is expressed at a maximum of 1.25 gallons / square foot or 45 gallons per dose. Timed intervals prevent system overload, but require adequate septic tank storage to hold the high-volume effluent created during peak hours of use. Recirculating Gravel Filter With a Recirculating Gravel Filter, partially clarified effluent from the septic tank flows into a recirculation tank. In the recirculation tank, raw effluent from the septic tank and the sand filter filtrate are mixed and pumped back to the sand filter bed. Through this process 80% of the effluent in the tank is reprocessed, while the remaining 20% of the effluent is passed on to the drainfield for final treatment in the soil. These RGF systems are typically used for commercial or industrial applications, like restaurants which have a much higher oil and grease content in the wastewater. Dosing rates for RSF systems can distribute effluent at a maximum rate of 5 gallons / square foot or 180 gallons per dose. To determine the design size of the filter, the volume of wastewater flow from the residence is divided by the loading rate. The length to width ratio is not as critical as providing a system that distributes wastewater evenly across the filter surface at regular intervals. from dwelling Septic tank Recirculating Gravel Filter Recirculating tank Pump Recirculation line return to pump To drainfield gravel, 12 sand, 24 gravel, min. 12 with slope of base = 1 per 8 16

23 Installing a Septic System Site Placement Site flexibility is probably the biggest advantage of a sand filter system. Because the filter is usually watertight and uses media for treatment, the soil where it is constructed is not as important as the ability of the media in the filter to transfer oxygen. Without enough oxygen, bacterial action will be compromised. The system should be constructed to keep surface water from entering the filter. Outflow drainage from the filter is provided by a four-inch pipe surrounded by pea rock. Depth of outflow should be one foot to 18 inches below the bottom of the sand. The effluent must drain freely out of the sand, since filter saturation reduces treatment effectiveness. A Bottomless Sand Filter, where wastewater is discharged directly to the soil beneath the sand filter may sometimes be allowed. High-rate sand filter Final Disposal of Wastewater Effluent discharged from this system will be very clean, but must still be applied to the soil for final treatment. Effluent leaving the sand filter is sent to a soil treatment system, usually a drainfield. The effluent is so "clean," a biomat layer does not form the way it does in soil treatment systems receiving effluent from septic tanks. A pressure distribution network may be used to apply effluent evenly throughout the system. Options for the soil treatment system include trenches, and drip distribution. Low-rate sand filter Operation and Maintenance All the routine operation and maintenance practices suggested for any onsite treatment system apply to sand filters. Sand filters require more maintenance than a conventional septic-tank-drainfield system, however. A maintenance contract therefore is strongly recommended. Maintenance includes inspecting all components and cleaning and repairing when needed. Visual inspection of the effluent is required and often a laboratory analysis is necessary. A flow meter should be installed and periodically checked to ensure the right amount of effluent is being applied to the system. Daily running costs for a sand filter are based on the operation of a small submersible pump, and average less than a dollar per month for an individual home. Overall operational costs of $200-$500 per year includes cleaning tanks, repairs, maintenance, and electricity. 17

24 Installing a Septic System Sand Filter System Costs 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. 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 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. Alternative Treatment Technology Orenco AdvanTex Orenco Systems provides complete wastewater treatment and disposal systems. Products range from effluent filters that can be retrofitted to an existing septic tank/soil absorption system to complete turnkey systems for new construction. These systems provide a higher level of treatment (organic content and solids removal) than most conventional designs, and can be modified to meet particular treatment objectives. They can provide nutrient removal, disinfection, and enhanced organic and solids treatment. The systems are very maintainable, and are available in a number of configurations to meet a wide variety of site constraints. Treatment methods are based on fixed film biological growth and physical straining, and units include AdvanTex Textile Filters (AX & RX), Recirculating Sand Filters (RSF), and Intermittent Sand Filters (ISF). All three are designed to support a diverse bacterial population on the surfaces of the media. The bacteria use the nutrients and carbon sources in the wastewater for food and energy. The pore structure of the treatment bed media enhances solids removal by physically filtering out contaminants. Ultraviolet Disinfection Units for disinfecting the treated effluent before final discharge are also available. Orenco's AdvanTex Treatment Systems are an innovative technology for onsite treatment of wastewater. The heart of the system is the AdvanTex Filter, a sturdy, watertight fiberglass basin filled with an engineered textile material. This lightweight, highly absorbent textile material treats a tremendous amount of wastewater in a small space. For example, the AX10 model has more than 20,000 square feet of surface area for biological breakdown of wastewater components, yet has a footprint of only 10 square feet. 18

25 Installing a Septic System Orenco AdvanTex AdvanTex -AX systems are loaded up to 45 gallons per ft2 per day, RX systems are loaded at 20 gallons per ft 2 per day. ISF's are typically loaded between 1.25 and 2.0 gallons per ft 2 per day. RSF's are loaded at up to 5 gallons per ft 2 per day. These systems provide a very high level of treatment with a relatively low capital expense and very low operating costs. In addition, the long-term performance of the systems is enhanced thanks to excellent access to all system components and overall ease of maintenance. A typical three-bedroom home with flows up to 450 gallons per day, using screened septic tank effluent, would require 10 square feet for an AdvanTex -AX system, or 90 square feet for an RSF or 360 square feet for an ISF. Disposal field requirements depend on state allowances for secondary or tertiary-level treated effluent. These systems require a primary settling basin, typically a septic tank, space for the treatment unit, and an available disposal area. The AdvanTex systems commonly are placed right on top of the septic tank between the inlet and outlet access risers. The sand filter treatment units are not more than 4 feet deep so, as long as a septic tank can be installed, there will be sufficient depth for the entire system. The effluent from these systems is considered secondary or tertiary. It is typically disposed of in a conventional subsurface soil system sized at 25 to 50%. An easily installed and cost-effective pressurized gravel-less chamber system is also available. If required, effluent can be disinfected for reuse or delivered to a receiving body of water, wherever local regulations allow this method of disposal. As with all wastewater treatment and disposal systems, periodic inspection of systems is recommended. For a typical three-bedroom system, an annual inspection and maintenance for the system is performed in less than one hour. OSI systems are designed with alarms and safeguards in order to alert the user of any problems that can develop with alarms, pump and float failures, and Biotube effluent filter clogging. Homeowners or system installers can easily remedy all of these potential problems. A new line of 'smart' control panels can diagnose a problem and make recommendations for what should be done to rectify the problem; troubleshoot the system automatically and make self-adjustments, and if needed, based on trend data; notify the operator of needed maintenance. Costs can vary widely depending on chosen system components, level of product supply and site constraints. A typical three-bedroom application would cost between $7, and $15, Costs will obviously vary due to locally available products, site constraints, and labor rates. Construction generally requires a backhoe operator and crew of 2, plus an electrician. A typical installation will takes one to four days from start to finish. 19