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Septic Install

Septic Install

After the home owner interview has been completed, which will only be a few minutes of your time, we can discuss the soil sample, which will help determine where the septic field will be located within your property.

For the septic install, the design process needs to take into consideration a lot of factors, also the size of field and which design suits the home owners needs.

There are different options for septic field designs:

  • Conventional Field Septic Systems
  • At Grade Septic Systems
  • Raised Treatment Mound Septic Systems
  • Pressure Distribution Systems
  • Holding Tanks

See below for descriptions of septic systems.

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Conventional Field Septic Systems

A conventional system consists of a septic tank and subsurface soil absorption trenches. After the initial treatment in the septic tank, the effluent (partially clarified water from septic tank) travels to the conventional component. The effluent travels to the conventional component by gravity or pump. If the conventional is higher than the tank, a pump must be used to get the effluent up to the conventional.

The conventional component consists of a series of trenches. The quantity and size of the trenches depends on the loading rate of the soil in which it will reside and how many bedrooms are in the house.

Every bedroom is worth 150 gallons/day. If it is a business, than the designer of the septic system must refer to the AOWMA Safety Codes to determine how many gallons/day the business will produce. The installer obtains the loading rate from the soil test. The total gallons/day the house/business produces is divided by the loading rate of the soil.

This number is how many square feet the conventional component must equal. The formula using leaching chambers or EZ-flows is different.

conventiona-in-ground-system

The soil test has a loading rate of 0.5.

450/0.5 = 900 square feet

The square footage of all the trenches must equal 900 square feet. Most commonly, the trenches are 6 feet wide. In this case, the conventional component could have 2 trenches 6 feet wide and 75 feet long or 3 trenches 6 feet wide and 50 feet long.

There are three ways the conventional component distributes effluent into the soil. The three ways are through stone & pipe, leaching chambers, or EZ-flows. Please click on the appropriate link to learn about more.

The final treatment of the effluent occurs in the soil. Each trench or cell receives an equal amount of effluent. The soil at the beginning of each trench receives the effluent generated by the house/business. Once the soil is saturated or clogged the effluent moves further down the trench. The soil beneath the conventional component removes pathogens, organic matter, reduction of contaminants by aerobic microorganisms and ion bonding to negatively charged clay particles. The soil serves as a fixed porous medium on which beneficial aerobic microorganisms grow. These organisms feed on organic matter present in the wastewater and help eliminate pathogens. Unless pre-treatment is used, a minimum of 48 inches of suitable soil is required for a conventional.

Advanced Treatment And At Grade

The At-Grade effluent treatment and disposal system is a method of accomplishing the final treatment and disposal of effluent from an advanced sewage treatment plant. The At-Grade is arranged utilizing pressurized distributional laterals above virgin ground surface. The pressurized pipe is supported 1 ½ inches above ground surface utilizing feet spaced every meter along the length of the pipe. The pressurized lateral is then covered with a 4 – 6 inch insulated shield. The entire assembly is then covered with wood chip cover or leaf mold or peat moss. The width will vary between 3 and 6 feet depending on slope and terrain variables.

Freezing is avoided by adequate cover, proper timed dosing, and proper drainage of pipes. All of these parameters are site specific and require specialized training to accomplish this task. At-grade systems are not allowed in all jurisdictions and may require a variance for installation.

A typical At-Grade will perform at a rate 4.3 times better than any subsoil absorption method. Within 2 – 6 years, the entire area of the At-Grade will become infiltrated by local flora and fauna, blending it in with the surrounding terrain. The efficiency of the At-Grade is expected to improve as time passes, decomposition and growth in the area aid in the absorption/distribution of water. Research indicates that At-Grades out perform all other methods of final treatment in high water table areas and tight clay soils.

At-Grades perform best in treed areas where protection from wind and vehicles is greatest. The vegetation in the forest provides the best infiltration available. Areas with sloping terrain are preferred, but level areas are also acceptable.

Raised Treatment Mound Septic Systems

A mound system consists of a septic tank and soil absorption bed. The soil absorption bed is used to distribute the effluent (partially clarified water from septic tank) into the soil. Each mound contains ASTM C-33 sand, 1.5″ washed stone, a distribution network, synthetic geotextile fabric, and a top-soil cap. The amount of sand needed in a mound is determined by the soil test.

The bottom of the absorption bed must be three feet higher than the limiting factor i.e. bedrock, ground water, or impermeable soil. For example, a soil test reveals bedrock at 24 inches. The mound must have 12 inches of sand to get 3 feet of separation. The absorption bed consists of stone, pipe, and synthetic fabric.

First, 6 inches of stone is laid down on a flat sand bed. The distribution network is laid on top of the stone. The distribution network is created by drilling equally spaced holes in pipe. Another 2 inches of stone is placed on top of the distribution network. Synthetic fabric is placed over the stone to protect the stone from dirt and roots. Sand is than placed around the absorption bed. Finally, a top soil cap is placed over the entire mound area. The mound must have a 3:1 slope to prevent erosion and to divert water away from the mound. The entire mound is planted with grass seed.

Mound Cross-Section
After the initial treatment in the septic tank, the effluent travels to the mound component. A pump is used to control the amount of doses delivered to the mound and to pressurize the distribution network in the mound. After every dose, the mound has a “rest period” which will result in superior pathogen and nutrient removal. Also, a pressurized distribution network reduces the chances for localized clogging.

The size of the mound is dependent on the slope of the site in which the mound will be built on, gallons produced per day by a residence or business, and the loading rate of the sand used underneath the absorption bed. The higher the slope of a mound site the bigger the mound.

This is due to the requirement to maintain a 3:1 slope on the mound. The gallons/day produced by a residence is based on the number of bedrooms in the house. Each bedroom is 150 gallons/day. The loading rate of ASTM C-33 mound sand is 1.0. The square footage of the absorption bed must equal to or greater than the total gallons/day produced by a residence/business divided by the loading rate of the sand. Thus, a three bedroom house produces 450 gallons/day divided by the loading rate of ASTM C-33 sand, 1.0.

450/1.0 = 450 square feet

Mound Distrubution NetworkThe square footage of the bed must equal 450 square feet. Common bed sizes are 6 feet by 75 feet or 5 feet by 90 feet. Generally speaking, beds that are longer and narrower are better functioning mounds. However, constraints like lot size and code setbacks can limit mounds to shorter, wider mounds.

The final treatment of the effluent occurs in the soil. The soil beneath the mound component removes pathogens, organic matter, reduction of contaminants by aerobic microorganisms and ion bonding to negatively charged clay particles. The soil serves as a fixed porous medium on which beneficial aerobic microorganisms grow. These organisms feed on organic matter present in the wastewater and help eliminate pathogens. Unless pre-treatment is used, a mound requires 6 inches to 36 inches of suitable soil.

Pressure Dose Septic Systems

 

A TYPICAL PRESSURE DOSE DISPOSAL TRENCH
A TYPICAL PRESSURE DOSE DISPOSAL TRENCH

‘Engineered’ systems come in a variety of types and flavors.  The most basic of these systems is the Pressure Dose system.  In this configuration, sewage flows from the dwelling into a septic tank.  After primary treatment in the tank, the wastewater flows into a dosing chamber that is equipped with a pump, filter screen and float control switches.  The wastewater is dosed to the disposal field in discrete doses throughout the day.  This pressurization dosing provides better distribution to the entire disposal field and better treatment of the wastewater in the soil.   These trenches can be filled with clean drainrock or a chamber-type dispersal unit.  In some instances, a capping fill is required.  This blanket of soil cover is spread over the disposal field to mitigate shallow native soils and provide protection for the disposal trenches.

Maintenance operations for a pressure dose system consists of regularly pumping the septic tank (we recommend once every 3-4 years) maintaining the electro-mechanical components and caring for the soil cover over the disposal field to prevent surface water (storm water) from traversing and/or ponding on top of the system.  Maintenance is important to prolonging the life of the system and should be done on a regular basis by a certified professional.

Holding Tanks

A holding tank is a tank that collects all wastewater from a residence or business. Technically, not a septic system because there is no treatment of the wastewater. The tank fills up with wastewater and an alarm is triggered when it is full. The owner calls a pumper and he pumps out the tank. Holding tanks come in any number of sizes. Anywhere from 2000 gallons all the way up to 13,000 gallons. They are made of concrete, steel, and plastic.

Advantages

  1. Inexpensive to install
  2. Requires the least amount of room
  3. Little or no maintenance

Disadvantages

  1. County and Province agencies prefer soil absorption septic systems
  2. Requires periodic pumping
  3. May leak ground water into tank
  4. Tank must be within 25′ of service pad, unless ISD is used

Call us to talk about your project today!