Septic tank and Infiltrator Leach Field System

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Notes:  With plastic infiltrator system, there is no need to use pipes inside them. 

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For this design: a 1200 gallon concrete tank. Two (2) field lines, 75 feet each.  Using plastic infiltrator system, 2feet wide and 18 inches tall.  Total project cost about $4,100 dollars. 

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Make note of row of small holes on green pipes

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File:Septic tank not in ground.jpg

A septic tank before installation

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File:Septic tank.jpg

The same tank partially installed in the ground

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File:Septic tank EN.svg

Septic tank scheme

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Septic tank and septic drain field

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A septic tank is a key component of the septic system, a small-scale sewage treatment system common in areas with no connection to main sewage pipes provided by local governments or private corporations. (Other components, typically mandated and/or restricted by local governments, optionally include pumps, alarms, sand filters, and clarified liquid effluent disposal means such as a septic drain field, ponds, natural stone fiber filter plants or peat moss beds.) Septic systems are a type of On-Site Sewage Facility (OSSF). In North America, approximately 25% of the population relies on septic tanks; this can include suburbs and small towns as well as rural areas (Indianapolis is an example of a large city where many of the city’s neighborhoods are still on separate septic systems). In Europe, they are in general limited to rural areas only.

The term “septic” refers to the anaerobic bacterial environment that develops in the tank and that decomposes or mineralizes the waste discharged into the tank. Septic tanks can be coupled with other on-site wastewater treatment units such as biofilters or aerobic systems involving artificial forced aeration.[1]

Periodic preventive maintenance is required to remove the irreducible solids that settle and gradually fill the tank, reducing its efficiency. In most jurisdictions this maintenance is required by law, yet often not enforced. Those who ignore the requirement will eventually be faced with extremely costly repairs when solids escape the tank and destroy the clarified liquid effluent disposal means.

A properly maintained system, on the other hand, can last for decades or possibly even a lifetime.

Description

A septic tank generally consists of a tank (or sometimes more than one tank) of between 4000 and 7500 liters (1,000 and 2,000 gallons) in size connected to an inlet wastewater pipe at one end and a septic drain field at the other. In general, these pipe connections are made via a T pipe, which allows liquid entry and exit without disturbing any crust on the surface. Today, the design of the tank usually incorporates two chambers (each of which is equipped with a manhole cover), which are separated by means of a dividing wall that has openings located about midway between the floor and roof of the tank.

Wastewater enters the first chamber of the tank, allowing solids to settle and scum to float. The settled solids are anaerobically digested, reducing the volume of solids. The liquid component flows through the dividing wall into the second chamber, where further settlement takes place, with the excess liquid then draining in a relatively clear condition from the outlet into the leach field, also referred to as a drain field or seepage field, depending upon locality.

The remaining impurities are trapped and eliminated in the soil, with the excess water eliminated through percolation into the soil (eventually returning to the groundwater), through evaporation, and by uptake through the root system of plants and eventual transpiration. A piping network, often laid in a stone-filled trench (see weeping tile), distributes the wastewater throughout the field with multiple drainage holes in the network. The size of the leach field is proportional to the volume of wastewater and inversely proportional to the porosity of the drainage field. The entire septic system can operate by gravity alone or, where topographic considerations require, with inclusion of a lift pump. Certain septic tank designs include siphons or other methods of increasing the volume and velocity of outflow to the drainage field. This helps to load all portions of the drainage pipe more evenly and extends the drainage field life by preventing premature clogging.

An Imhoff tank is a two-stage septic system where the sludge is digested in a separate tank. This avoids mixing digested sludge with incoming sewage. Also, some septic tank designs have a second stage where the effluent from the anaerobic first stage is aerated before it drains into the seepage field.

Waste that is not decomposed by the anaerobic digestion eventually has to be removed from the septic tank, or else the septic tank fills up and undecomposed wastewater discharges directly to the drainage field. Not only is this bad for the environment but, if the sludge overflows the septic tank into the leach field, it may clog the leach field piping or decrease the soil porosity itself, requiring expensive repairs.

How often the septic tank has to be emptied depends on the volume of the tank relative to the input of solids, the amount of indigestible solids, and the ambient temperature (as anaerobic digestion occurs more efficiently at higher temperatures). The required frequency varies greatly depending on jurisdiction, usage, and system characteristics. Some health authorities require tanks to be emptied at prescribed intervals, while others leave it up to the determination of the inspector. Some systems require pumping every few years or sooner, while others may be able to go 10–20 years between pumpings. Contrary to what many believe, there is no “rule of thumb” for how often tanks should be emptied. An older system with an undersize tank that is being used by a large family will require much more frequent pumping than a new system used by only a few people. Anaerobic decomposition is rapidly re-started when the tank re-fills.

A properly designed and normally operating septic system is odor-free and, besides periodic inspection and pumping of the septic tank, should last for decades with no maintenance.See [1]

A well-designed and -maintained concrete, fiberglass, or plastic tank should last about 50 years

Potential problems

  • Excessive dumping of cooking oils and grease can cause the inlet drains to block. Oils and grease are often difficult to degrade and can cause odor problems and difficulties with the periodic emptying.
  • Flushing non-biodegradable items such as cigarette butts and hygiene products such as sanitary napkins, tampons, and cotton buds/swabs will rapidly fill or clog a septic tank; these materials should not be disposed of in this way.
  • The use of garbage disposers for disposal of waste food can cause a rapid overload of the system and early failure.
  • Certain chemicals may damage the components of a septic tank, especially pesticides, herbicides, materials with high concentrations of bleach or caustic soda (lye) or any other inorganic materials such as paints or solvents.
  • Roots from trees and shrubbery growing above the tank or the drainfield may clog and/or rupture them.
  • Playgrounds and storage buildings may cause damage to a tank and the drainage field. In addition, covering the drainage field with an impervious surface, such as a driveway or parking area, will seriously affect its efficiency and possibly damage the tank and absorption system.
  • Unsupervised septic tanks may cause serious injury or death to children playing nearby.
  • Excessive water entering the system will overload it and cause it to fail. Checking for plumbing leaks and practicing water conservation will help the system’s operation.
  • Very high rainfall, rapid snow-melt, and flooding from rivers or the sea can all prevent a drain field from operating and can cause flow to back up and stop the normal operation of the tank.
  • Over time, biofilms develop on the pipes of the drainage field, which can lead to blockage. Such a failure can be referred to as “biomat failure”.
  • Septic tanks by themselves are ineffective at removing nitrogen compounds that have potential to cause algal blooms in receiving waters; this can be remedied by using a nitrogen-reducing technology,[3] or by simply ensuring that the leach field is properly sited to prevent direct entry of effluent into bodies of water.
  • Not all varieties of toilet paper have been suitable for disposal in a septic tank, as some in the past did not deteriorate sufficiently (or, at least at some points in history, some toilet paper was specifically marked as suitable for use in septic systems and some was not).

 

Helpful tips

  • As mentioned above, many chemicals such as household cleaners and detergents can damage the septic system, including the bacteria involved in breaking down solid waste. However, products such as enzyme, chemical, or bacterial additives are not the solution – they can actually cause more problems, not only to your system, but to the environment as well. The best method is to stop using caustic cleaners, and to allow the natural bacteria found in waste to re-accumulate. Check your local legislation to find out what is allowed and what is not if additives must be used.[4]
  • Oftentimes, septic systems back up due to non-biodegradable items — either flushed objects or hair from shower drains — that make their way through the inlet T pipe and into the septic tank, which then can clog the outlet T pipe and cause the liquid to overflow. To try to avoid such a problem, installation of a filter is recommended. A filter acts as a security guard and stops unwanted items from making their way into the tank. It can be installed in either the inlet or outlet T and protects the septic system.
  • Septic system cover safety is an extremely important topic and ongoing issue in the U.S. Older septic system covers were concrete, which over time can crack and corrode and should be regularly checked for guaranteed security. Metal or cast iron covers also have the ability to be unsafe. Metal and cast iron are such heavy materials that if not properly installed and/or with an incorrect bottom structure, can flip themselves like a revolving door, which can be especially unsafe for children and animals. It is so important that covers should be regularly checked, preferably by a professional, who can determine whether the cover is up to code standards. It is recommended that covers be checked twice per season (such as once in the beginning of spring and once at the end of spring, once at the beginning of summer and once at the end of summer, etc.). It is also highly recommended that covers are inspected after winter in colder regions, as heavy snow and ice can damage even a newer cover.
  • Many chemicals can damage septic tanks. A good solution is to allow the natural bacteria found in waste to re-accumulate or use of a product that contains natural bacteria that eat the toxic waste.

Environmental issues

Some pollutants, especially sulfates, under the anaerobic conditions of septic tanks, are reduced to hydrogen sulfide, a pungent and toxic gas. Likewise, methane, a potent greenhouse gas, is another by-product. Nitrates and organic nitrogen compounds are reduced to ammonia. Because of the anaerobic conditions, fermentation processes take place, which ultimately generate carbon dioxide and methane.

The fermentation processes cause the contents of a septic tank to be anaerobic with a low redox potential, which keeps phosphate in a soluble and, thus, mobilized form. Because phosphate can be the limiting nutrient for plant growth in many ecosystems, the discharge from a septic tank into the environment can trigger prolific plant growth including algal blooms, which can also include blooms of potentially toxic cyanobacteria. See http://www.septictank.org

Soil capacity to retain phosphorus is large compared with the load through a normal residential septic tank. An exception occurs when septic drain fields are located in sandy or coarser soils on property adjoining a water body. Because of limited particle surface area, these soils can become saturated with phosphate. Phosphate will progress beyond the treatment area, posing a threat of eutrophication to surface waters.[5]

In areas with high population density, groundwater pollution levels often exceed acceptable limits. Some small towns are facing the costs of building very expensive centralized wastewater treatment systems because of this problem, owing to the high cost of extended collection systems.

To slow development, building moratoriums and limits on the subdivision of property are often imposed. Ensuring existing septic tanks are functioning properly can also be helpful for a limited time, but becomes less effective as a primary remediation strategy as population density increases.

Trees in the vicinity of a concrete septic tank have the potential to penetrate the tank as the system ages and the concrete begins to develop cracks and small leaks. Tree roots can cause serious flow problems due to plugging and blockage of drain pipes, but the trees themselves tend to grow extremely vigorously due to the continuous influx of nutrients into the septic system.

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Septic drain field

Septic drain fields, also called leach fields or leach drains are used to remove contaminants and impurities from the liquid that emerges from the septic tank. A septic tank, the septic drain field, and the associated piping compose a complete septic system. The septic drain field is effective for disposal of organic materials readily catabolized by a microbial ecosystem. The drain field typically consists of an arrangement of trenches containing perforated pipes and porous material (often gravel) covered by a layer of soil to prevent animals and surface runoff from reaching the wastewater distributed within those trenches.[1] Primary design considerations are hydraulic for the volume of wastewater requiring disposal and catabolic for the long-term biochemical oxygen demand of that wastewater.

Hydraulic design

Many health departments require a percolation test (“perc” test) to establish suitability of drain field soil to receive septic tank effluent. An engineer or licensed designer may be required to work with the local governing agency to design a system that conforms to these criteria.

Wastewater from toilets is assumed to contain bacteria and viruses capable of transmitting disease. Disinfection methods used prior to surface disposal of municipal sewage cannot be used with septic tanks because disinfection would prevent wastewater treatment by killing the septic tank and soil ecosystems catabolizing the putrescible contents of the wastewater. A properly functioning drain field holds and deactivates pathogens before they leave the drain field soil.

The goal of percolation testing is to ensure the soil is permeable enough for septic tank effluent to percolate away from the drain field, but fine grained enough to filter out pathogenic bacteria and viruses before they travel far enough to reach a water well or surface water supply. Coarse soils – sand and gravel – can transmit wastewater away from the drain field before pathogens are destroyed. Silt and clay effectively filter out pathogens but allow very limited wastewater flow rates.[2] Percolation tests measure the rate at which clean water disperses through a disposal trench into the soil. Several factors may reduce observed percolation rates when the drain field receives anoxic septic tank effluent:[3]

  • Microbial colonies catabolizing soluble organic compounds from the septic tank effluent will adhere to soil particles and reduce the interstitial area available for water flow between soil particles. These colonies tend to form a low-permeability biofilm of gelatinous slime at the soil interface of the disposal trench.[4]
  • Insoluble particles small enough to be carried through the septic tank will accumulate at the soil interface of the disposal trench; non-biodegradable particles like mineral soil from laundry or vegetable washing, or bone and eggshell fragments from garbage disposals will remain to fill interstitial areas formerly available for water flow out of the trench.[5]
  • Cooking fats or petroleum products emulsified by detergents or dissolved by solvents can flow through prior to anaerobic liquifaction when septic tank volume is too small to offer adequate residence time, and may congeal as a hydrophobic layer on the soil interface of the disposal trench.[6]
  • Rising groundwater levels may reduce the available hydraulic head (or vertical distance) causing gravitational water flow away from the disposal trench. Effluent initially flowing downward from the disposal trench ultimately encounters groundwater or impermeable rock or clay requiring a directional shift to horizontal movement away from the drain field. A certain vertical distance is required between the effluent level in the disposal trench and the water level where the effluent is leaving the drain field for gravitational force to overcome viscous frictional forces resisting flow through porous soil. Effluent levels in the vicinity of the drain field will appear to rise toward the ground surface to preserve that vertical distance difference if groundwater levels surrounding the drain field approach the level of effluent in the disposal trench.[6]
  • Frozen ground may seasonally reduce the cross-sectional area available for flow or evaporation.

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Dosing schedules or resting periods

A drain field may be designed to offer several separate disposal areas for effluent from a single septic tank. One area may be “rested” while effluent is routed to a different area. The nematode community in the resting drain field continues feeding on the accumulated biofilm and fats when the anaerobic septic tank effluent is no longer available. This natural cleansing process may improve hydraulic capacity of the field by increasing available interstitial area of the soil as accumulated organic material is oxidized. The resting improvement may approach, but is unlikely to exceed, the original clean water percolation rate of the site.

Catabolic design

Just as the septic tank is sized to support a community of anaerobic organisms capable of liquifying anticipated amounts of putresible materials in wastewater, the drain field should be sized to support a community of aerobic soil microorganisms capable of decomposing the anaerobic septic tank’s effluent into aerobic water. Hydrogen sulfide odors or iron bacteria may be observed in nearby wells or surface waters when effluent has not been completely oxidized prior to reaching those areas.[6] The biofilm on the walls of the drain field trenches will use atmospheric oxygen in the trenches to catabolize organic compounds in septic tank effluent. Groundwater flow is laminar in the aquifer soils surrounding the drain field.[7] Septic tank effluent with soluble organic compounds passing through the biofilm forms a mounded lens atop groundwater underlying the drain field. Molecular diffusion controls mixing of soluble organic compounds into groundwater and transport of oxygen from underlying groundwater or the capillary fringe of the groundwater surface to micro-organisms capable of catabolizing dissolved organic compounds remaining in the effluent plume

Biofilter

When a septic tank is used in combination with a biofilter, the height and catabolic area of the drain field may be reduced. This technology may allow higher density residential construction, minimal site disturbance, more usable land for trees, swimming pools, or gardens. With adequate routine maintenance it may reduce the chances of the drain field plugging up. The biofilter will not reduce the volume of liquid that must percolate into soil, but it may reduce the oxygen demand of organic materials in that liquid.

Inappropriate wastes

Septic tank and drain field microorganisms have very limited capability for catabolizing petroleum products and chlorinated solvents, and cannot remove dissolved metals; although some may sorb onto septic tank sludge or drain field soils, and concentrations may be diluted by other groundwater in the vicinity of the drain field. Cleaning formulations may reduce drain field efficiency. Laundry bleach may slow or stop microbial activity in the drain field, and sanitizing or deodorizing chemicals may have similar effects. Detergents, solvents and drain cleaners may transport emulsified, saponified or dissolved fats into the drain field before they can be catabolized to short-chain organic acids in the septic tank scum layer.[6]

File:Klamath Septic Leach Field.JPG

Septic drain field exposed by flood damage

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What Size Septic Tank Do I Need?

If you are planning a construction project away from a municipal area, you will most likely need to include plans for a septic tank and field lines. The location and number of field lines will be determined by the percolation test (sometimes called a perc or perk test) and local codes. The size of the septic tank can be based on water usage or home size.

  1. Calculation by Water Usage

    • There are a number of methods of calculations to determine the size tank required or needed for your home. The most accurate and reliable way is with water usage. The size of the septic tank required is based on the amount of water it will handle and in turn will be dispersed into the field lines. It should be noted that in many parts of the country, the minimum size tank allowed is 1,000 gallons. Based on the total water usage of your home, the following is a recommended tank size.

      Up to 500 gallons per day: 900 gallon tank
      Up to 700 gallons per day: 1,200 gallon tank
      Up to 900 gallons per day: 1,500 gallon tank
      Up to 1,240 gallons per day: 1,900 gallon tank

    Calculations By House Size

    • A less accurate guide to calculating your tank size is the number of bedrooms in your home. These calculations assume all bedrooms will be occupied and base the estimated water usage on this data. If you live alone in a three bedroom house, these calculations will be off. The reasoning for using these calculations is that a new owner may occupy all the bedrooms and the tank must be of an adequate size to handle the load. Listed here are the recommended tank sizes based on number of bedrooms.

      One or two bedrooms: 750 gallon tank
      Three bedroom: 1,000 gallon tank
      Four bedrooms: 1,200 gallon tank
      Five or six bedrooms: 1,500 gallon tank

    Estimated Cost

    • As with any materials or services, the cost can vary widely depending on where you live and the market conditions. For planning purposes we will assume you are planning to use a concrete septic tank. These are by far the most common and have a long life expectancy. The average 1,000 gallon septic tank will cost you between $500 and $700. If you want to move up to a 1,250 gallon tank, you should expect to pay at least an additional $100. If the tank is properly sized you can expect to need to clean it out every three to five years. On average, it will cost you between $75 and $150 to have your tank emptied.

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Read more: What Size Septic Tank Do I Need? | eHow.com http://www.ehow.com/way_5183882_size-septic-tank-do-need_.html#ixzz1aFpyQrld

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How Large of a Septic Tank Do I Need?

The septic tank is the heart of your septic system. If the tank is too small you may experience serious and expensive problems, and most certainly will need to empty the tank more frequently. If you get too large of tank, then you waste money purchasing unneeded capacity. Fortunately, with minimal research you can determine the proper tank size for your situation.

  1. Local Codes and Requirements

    • Most areas have strict guidelines regarding the minimum size tank for a particular application. This requirement will be based on the results of your perc test and the number of bedrooms in the home. In many areas, the minimum size tank allowed is 1,000 gallons, although some areas still allow smaller tanks to be used.

    Perc Test

    • The perc test determines the absorption rate of the soil where the field lines are to be located. This test will determine the amount of field line required for your system. The size of the actual septic tank will need to coordinate with the amount of field line and the anticipated usage. This is estimated by the number of bedrooms in the home, but is actually determined by the number or residents living in the home.

    Frequency of Cleaning

    • Once you have satisfied local codes, you may install a larger tank if you so desire. The main advantage to installing a larger tank is to decrease the frequency of cleanings. For example, if there are four people living in the home, a 1,000 gallon septic tank would need to be cleaned out approximately every 2.6 years. If you go up to a 1,500 gallon tank, this increases to every 4.2 years. With the average cleaning cost at $350, this would result in annual savings of $51. You will need to determine if the increase in the initial investment is offset by these savings, and the reduced frequency of cleaning.

Read more: How Large of a Septic Tank Do I Need? | eHow.com http://www.ehow.com/way_5444316_large-septic-tank-do-need.html#ixzz1aFxvQt3K

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SoilFacts Septic Systems and Their

The septic-tank-soil-treatment system (also called a septic system) is an effective, long-standing method for collecting, treating, and disposing of sewage from rural and suburban homes. Septic systems are used in every county in North Carolina: more than 50 percent of the homes have them, and new systems are being installed at a rate of 40,000 per year. This fact sheet will answer some typical questions about septic systems and their maintenance.

Why Use a Septic System?
Septic systems are used when sewage treatment plants are not accessible. They safely treat and dispose of wastewaters produced in the bathroom, kitchen, and laundry. These wastewaters may contain disease-causing germs and pollutants that must be treated to protect human health and the environment. Although septic systems are usually a permanent solution to wastewater treatment and disposal, they sometimes serve as a temporary solution until sewer lines are installed.

What Is a Septic System?

There are a number of different septic systems, each with its own design. The conventional system is the one most commonly used in North Carolina (Figure 1). It consists of three main parts: the septic tank, the drainfield, and the soil beneath the drainfield.

The septic tank is a watertight concrete box about 9 feet long and 5 feet tall. It is buried in the ground just outside the home. The tank is usually precast from reinforced concrete and can be purchased from concrete manufacturers. While typically designed with a 1,000-gallon liquid capacity, the size of the tank is legally determined by the number of bedrooms in the home. The tank temporarily holds household wastes and allows a small amount of pretreatment to take place (Figure 2).

The tank is connected to the drainfield by a buried pipe. A typical drainfield consists of two to five trenches excavated into the subsoil. In many systems, a distribution box or a flow divider helps move wastewater to each trench. In most conventional septic systems, the trenches are 3 feet wide, 2 to 3 feet deep, and 9 feet apart. In each trench, a 1-foot thick layer of washed gravel or stone is placed around a 4-inch-diameter perforated distribution pipe. After the trenches are covered with soil, the area must be landscaped to keep surface waters from ponding over the drainfield.

The drainfield has also been called the nitrification field or the soil absorption field. The sole purpose of the drainfield is to deliver wastewater to the soil. The soil purifies the wastewater by removing the germs and chemicals before they reach the groundwater or any adjacent surface waters such as rivers, lakes, and estuaries.
 

 

fig1.gif (49572 bytes) Figure 1. A conventional septic system.

 

fig2.gif (57403 bytes) Figure 2. A two-compartment septic system.

What Takes Place in the Tank?

All of the wastewaters from the home should flow into the septic tank. Even waters from the shower, bathtub, and washing machine can contain disease-causing germs or environmental pollutants. As wastewater flows into the tank, the heavier solid materials settle to the bottom (forming a sludge layer), the lighter greases and fats float to the top (forming a scum layer), and the liquid (sewage effluent) flows out of the tank. An outlet baffle (or a sanitary tee at the outlet end) prevents solids from flowing out with the liquids. The tank’s primary purpose is to retain the solids while releasing sewage effluent to the drainfield.

What Happens in the Drainfileld and the Soil?

The real treatment of the wastewater occurs in the soil beneath the drainfield. Sewage effluent flows out of the tank as a cloudy liquid that still contains many disease-causing germs and environmental pollutants. Effluent flows into the perforated pipe in the trenches, passes through the holes in the pipe, and then trickles down through the gravel to the soil. As effluent enters and flows through the soil, many of the bacteria that can cause diseases are filtered out. Some of the smaller germs, such as viruses, are adsorbed by the soil until they are destroyed. The soil can also retain certain chemicals, including phosphorus and some forms of nitrogen.

Where Can a Septic System Be Used?

Unlike a sewer system, which discharges treated wastewater into a body of water, the septic system depends on the soil around the home to treat and dispose of sewage effluent (Figure 3). For this reason, a septic system can be used only on soils that will adequately absorb and purify the effluent. If a septic system is installed in soil that cannot do so, the effluent will seep out onto the soil surface overlying the drainfield. In addition to causing an unpleasant smell, this untreated effluent can pose health problems.

In some cases where the soils do not adequately absorb the wastewater, the toilets and sinks might not drain freely. If the soil can absorb the effluent but not treat it, the sewage may contaminate the groundwater.

fig3.gif (41182 bytes)
Figure 3. Wastewater treatment and disposal in the soil.
(Adapted from Tyler et al., 1977)

What Kinds of Soils Are Best Suited to Conventional Systems?

Gently sloping, thick, permeable soils with deep water tables make the best sites. The soil should be a uniform brown, yellow, or bright red, and it should not have spots of gray, which often indicate that it is excessively wet. The soil texture should be neither too sandy nor too clayey, and it should have good aggregation, or structure (that is, a handful of the soil should easily break apart into small aggregates). Avoid areas that have rock close to the surface, very sticky clays, or soil layers that restrict the downward flow of water.

How Do I Know If My Site Is Suitable for a Septic System?

There are more than 400 kinds of soils in North Carolina, more than one of which are often found within a 1-acre lot. Because many of these soils are unsuitable for septic systems, you should always have your county environmental health specialist (sanitarian) conduct a comprehensive soil and site investigation. If you are considering purchasing a piece of land for a homesite, you can obtain additional information from the Cooperative Extension Service publication (AG-439-12), Investigate Before You Invest.

How Large Is a Typical Drainfield?

Usually, the drainfield can fit within the front yard or the backyard of a typical 1-acre homesite. The precise area requirements will depend upon the kinds of soils at the homesite, the size of the house (the number of bedrooms), and the topography of the lot. A site with clayey, slowly permeable soils needs a larger drainfield to absorb the sewage effluent than does a site with sandy, permeable soils. Adequate land area must be available to isolate the entire septic system from any nearby wells, springs, streams, lakes, or other bodies of water. There also must be enough area to install a replacement system in case it is ever needed. This replacement area must meet the same soil and site requirements as the original system.

What Legal Requirements Regulate Septic Systems?

State law requires that soils be evaluated by the local health department and that an improvement permit be issued before house construction begins or the septic system is installed. Also, the installation must be approved by the health department before electrical service can be permanently connected to the home and the septic system put into use.

What Maintenance Is Needed?

Both the septic tank and the drainfield must be properly maintained. With conscientious maintenance, the system should work correctly for many years. Such maintenance begins with water use and waste disposal habits. Since your family will determine which materials enter the system, you should establish rules for proper use and maintenance.

The suggestions outlined in the box will save you anguish and money when applied to most conventional systems. More sophisticated systems require additional maintenance, possibly at much greater cost. Also, recent rule changes now require owners of some alternative septic systems and community septic systems to hire a certified operator to maintain their systems. For more information about these requirements, contact your local health department.

http://www.soil.ncsu.edu/publications/Soilfacts/AG-439-13/

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