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Sunday, January 21, 2018

Undeveloped Land

Purchasing Undeveloped Land

Are you in the market to buy an undeveloped lot on which to build your new dream home? If the property is not served by public water and sewer utilities, perhaps one of the most important factors to consider when deciding whether to purchase the lot, is whether it will support an onsite well and septic system. Be aware, there are a number of properties in the Anchorage and Eagle River area which have such poor site conditions that the installation of an onsite septic system is not possible. Furthermore, there are a few areas where the chance of drilling an adequate well is somewhat uncertain.

Given these facts, it is imperative to determine whether the lot will support an onsite septic system, and whether there is a reasonable chance of obtaining an adequate well, prior to purchasing the land. The purpose of this page is to guide you through some of the factors which should be considered when purchasing undeveloped land. To further protect your interests, you should always seek representation from a realtor who has experience in all of the legalities and disclosure requirements associated with the purchase of raw land. Their involvement costs you, the buyer, nothing and can save you a tremendous amount of headache and heartache. Furthermore, you should always retain a registered civil engineer who has extensive experience with onsite wells and septic systems to act as your technical representative. Do not rely solely on information provided to you by the seller's engineer.

If the lot will not support an onsite septic system, the Municipality of Anchorage (MOA) will not issue a building permit or land use permit for construction. In short, you can't build on a lot if you cannot put a septic system on it. Furthermore, the Municipality will not allow the installation of a holding tank for new construction. Consequently, it is imperative that any offer to purchase undeveloped land be contingent upon soils testing and an engineer's site evaluation.


General Guidelines

The following links will help guide you through the factors that must be considered when developing a property which will be served by an onsite well and/or septic system.

If you have any questions or need further assistance, please feel free to contact us.

Septic System Design

The first step in the septic system design process is to identify locations on the property that have suitable site conditions to support an onsite septic system. For more information on septic systems in general, please see our Description of a Typical Septic System page. Consideration of potential sites must take into account the following regulatory constraints:

  • The drainfield must be at least 50 feet away from any downhill slope greater than 25%; however, the MOA can waive this requirement, on a case-by-case basis.
  • Percolation test: If the percolation test results yield an absorption rate of less than 60 minutes per inch, a conventional system can be installed. Percolation rates between 60 and 120 minutes per inch necessitate using an Advanced Wastewater Treatment System (AWWTS). If it takes greater than 120 minutes for the water level in the percolation hole to drop 1 inch, the soil is unsuitable for an onsite septic system.
  • There must be adequate room to install 2 drainfields (primary and reserve) on the lot and not encroach upon the protective radii of the neighboring wells and proposed well for the lot. The protective radii are summarized as follows:
    • Private wells (single-family residence and duplexes) have a 100 foot protective radius.
    • Class "C" wells have a 150 foot protective radius.
    • Class "A" or "B" wells have a 200 foot protective radius.
  • The septic system must be at least 100 feet away from any surface water. The MOA can waive this on a case-by-case basis. If the lot is covered with snow it may be difficult to assess whether there are surface waters present. Clearly, there are some areas where surface waters are not a concern, and there are others where it is always questionable. Typically, it is not possible for an engineer to make absolute statements regarding surface waters during winter conditions, unless he/she has done work in the immediate vicinity during summer months. The only other options are to talk to the neighbors owning adjacent developed lots, or to rely on statements from the sellers.
  • If the groundwater supply (aquifer) has a high concentration of nitrates (a by-product of decomposing organic material), the MOA may prohibit the installation of a conventional onsite septic system and require the installation of a more expensive AWWTS system that is designed to reduce nitrates.  There are two nitrogen reducing systems approved for use in the Municipality of Anchorage, the  AerocellTM system, manufactured by Quanics Inc, and the AdvantexTM system manufactured by Orenco Systems Inc.  The MOA classifies these as "Catetory III Nitrogen Reducing Systems"

Prior to making the initial site visit and identifying a potential septic system site, records research is done on the subject and adjacent properties to identify the locations of pertinent wells, septic systems, structures, surface waters, wetlands, easements, and topographical features within the vicinity of the subject property. This information is usually compiled from records on file at the MOA, ADEC, and/or GEG historical records.  In some cases it may be necessary to retain a registered Land Surveyor to survey the location of specific features, like streams, wetlands, existing wells, and other features.  This information is compiled and used to create a preliminary site plan. In short, there is a considerable amount of preparatory work before the initial site visit.

With the site plan in hand, the engineer can make some preliminary determinations as to what areas on the lot may be potential septic sites. If the property lines are not clearly identified in these areas, they should be flagged by a registered land surveyor prior to the initial site visit.

During the site visit, the engineer will make a visual assessment of the potential septic sites previously identified and select the site/s which are best suited. Typically, the following objectives are considered:

  • If possible, the septic system should be downhill from the existing or proposed house so as to insure that there is gravity flow from the house to the septic tank and drain field. There are cases where this cannot be achieved and the installation of a lift station is necessary.
  • Ideally, the septic system should not be under an existing or proposed driveway/parking area.
  • The septic site should be as accessible as possible for purposes of construction and maintenance.
  • The septic tank must be in a location where it can be reached by a pump truck.
  • The septic system should not be in a drainage swale or depression that may seasonally carry or have standing water in it.
  • The drainfield must have adequate separation to any existing septic systems, structures, and other features specified with MOA code.

With the septic site(s) selected, the field engineer then narrows the site selection down to the most suitable areas and establishes the location for the test holes. If the property is undeveloped, and this is the first septic system to be installed on it, the MOA will also require that the engineer establish the location for a reserve (future) drainfield site. In short, there will need to have the room to install two septic systems; however, only one will have to be installed. If the property is currently developed and the existing septic system is being upgraded (because it has failed) then identification of a reserve drain field site is not required, unless the number of bedrooms in the house has increased since the original septic system was installed. If so, then a reserve drainfield site will need to be identified. Both the upgrade and reserve drainfield will need to be adequately sized to serve the current or proposed number of bedrooms in the residence.

Once the test holes are excavated, the soils are classified and percolation tests are performed. Per MOA requirements the groundwater levels are monitored in the test hole for a period of at least 7 days. The information and data gathered in this investigation are used to establish what type of septic system can be installed and how large the drainfield will be. The size of the septic tank is not dependent upon the site conditions, but rather the number of bedrooms in the residence.

Typically, the most cost effective system to install is a conventional septic system; however, the soil and site conditions may be such that installation of a conventional septic system is not feasible. For marginal sites, the utilization of an AWWTS may be necessary.  For some properties the site conditions may be so poor that the only viable alternative is to install a holding tank.

Utilizing the information gathered to this point, the engineer will prepare the design drawings and specifications. This package is then submitted to the applicable regulatory agency for plan review and issuance of a permit. For single-family residences and duplexes inside the MOA (Girdwood to the Knik River), the permit is issued by the MOA, Development Services Department. For multi-family dwellings the permit (called a certificate to construct) is issued by the State of Alaska, ADEC. Both regulators charge a fee for review of the design package and issuance of the permit.

The cost for the contractor to install a septic system can vary widely, depending up the type of system, the size of the system, and the unique site conditions. The property owner should obtain bids from several reputable contractors that specialize in the installation of septic systems.  During the installation of the system, the engineer must perform mandatory inspections at various stages of the construction. The final step of the process is for the engineer to prepare record drawings of the new system and submit the drawings to the applicable regulatory agency for review and final approval the system.

Soil Analysis

Test Holes

The first step in the soils evaluation process is to dig test holes. For information on establishing the location of the test holes see the Septic System Design page. Per State and Municipal regulations, the new septic system will have to be placed at least 6 feet above the bottom of the test hole. In other words, if the test hole was 10 feet deep, the drain field could be no deeper than 4 feet, severely restricting the type of system that could be installed. For this reason, it is usually desirable to dig the test hole as deep as practical, or until bedrock or groundwater are encountered. Most test holes are excavated with a backhoe that is capable of digging to 16 or 18 feet deep.

Once the test holes are dug, the field technician will visually classify the type of soils observed. The technician will also look for the presence of bedrock, impermeable soils, or groundwater. In addition, he or she will identify the soil profile in/on which the septic system should be placed. A perforated pipe is then placed vertically in the excavation and the hole is back filled. This is referred to as the test hole monitoring tube and it is used to monitor for the presence of groundwater. The Municipality of Anchorage requires that groundwater levels be monitored for a period of at least 7 days.

It is important to note that groundwater levels can vary significantly, depending upon the locale and time of year. If the lot has high groundwater during winter conditions, to the extent that the installation of a septic system is marginal, it is likely the conditions will be unsuitable for an onsite septic system after spring run-off recharges and raises the groundwater table. In short, if the groundwater conditions are marginal for the installation of an onsite septic system, it is essential to know whether the data was obtained during winter or spring conditions. The importance of this cannot be overemphasized.

Percolation Testing

After the test hole is backfilled, the backhoe operator will then dig an additional hole off to the side. This depth is referred to as the "perk bench". The bench is excavated to the soil profile which was specified by the field technician. The percolation test is then performed in order to determine the application rate used for the design of the septic system. The percolation test involves digging a 6 inch diameter hole that is 12 inches deep into the bench that was excavated by the backhoe operator. This is usually done with a post hole digger. The hole is then filled with a standing head of water for a period of at least 4 hours. this is called the presoak period. The MOA will waive the requirement of a presoak for the soil if when filled with water to a depth of 12 inches, two times, it will drain away completely in less than 10 minutes each time. For most soils, a presoak is required.

After the presoak period the percolation test is performed. The "perk" test is performed by filling the perk hole with 8 inches of water and measuring how much the water level drops in 30 minutes. If all of the water drains away in less than 30 minutes, the time interval is changed to 10 minute readings. At the end of the 30 minute period, the hole is again filled to the 8 inch level and the process repeated. A minimum of three 30 minute readings are taken. From this, the percolation rate is calculated by dividing 30 minutes by the drop in inches during the 30 minute period. The following is a general classification of the percolation rates:

  • Less than 1 minute per inch: Coarse sands/gravels that may require the installation of a sand filter to slow down the flow of waste water through the soil
  • 1-5 minutes per inch: Excellent
  • 6-15 minutes per inch: Good to Fair
  • 15-30 minutes per inch: Fair
  • 30-60 minute per inch: Fair to Poor
  • 60 - 120 minutes per inch: poor
  • Greater than 120 minutes per inch: Unsuitable for an onsite septic system

With the soil profile identified, the groundwater levels established, and the percolation rate determined, the engineer can then proceed with the septic system design

Purchasing Undeveloped Land?

If possible, negotiate the transaction so that the sellers pay for the soils testing (however, you should retain the right to select the engineer), with the agreement that you will reimburse them for their costs upon closing of the sale, assuming the test results are acceptable. Bear in mind that most sellers will not be receptive to this idea. Nonetheless, by heeding this advice, you won't risk investing money into a piece of land that turns out to be undeveloped.

In addition, you should retain the right to accept, or reject, the suitability of the percolation results. The reason for this is that if you make your only stipulation that "the lot be suitable for installing an onsite well and septic system", you may be bound to purchase a lot that, although suitable, will require an investment of $30,000 - $50,000 worth of engineering, drainage systems, and "high-tech" septic system technology in order to make it developable. If this turns out to be the case, then you want to right to re-negotiate the price of the lot.

Septic Testing

Absorption Requirements

The amount of water that a drainfield must be capable of absorbing is specifically defined by the Municipality of Anchorage (MOA) as 150 gallons per day, per bedroom, of the serviced residence. This corresponds to the following absorption requirements:

  • 2 bedroom house: 300 gallons per day
  • 3 bedroom house: 450 gallons per day
  • 4 bedroom house: 600 gallons per day
  • 5 bedroom house: 750 gallons per day

It is important to note that the septic system must be capable of absorbing the required volume and not just accepting it. In other words, the ability to introduce 450 gallons into a drainfield serving a 3 bedroom house does not mean that the system is adequate. The engineer must confirm that the water is being absorbed at an adequate rate.

Monitoring Tube

In order to perform the SAT, a functional monitoring tube must be present in the drainfield. The monitoring tube allows the field engineer to measure the liquid level in the drainfield. If a monitoring tube is not present then arrangements must be made for a contractor to install one.  A list of the typical costs associated with this can be found in our cost list.

Septic Tank and/or Drainfield Pumping

If the septic tank has not been pumped in the last 12 months it will be necessary to have it pumped in order to obtain a municipal Certificate of On-site Systems Approval. Even if the tank has been pumped in the last 12 months, it may be necessary to pump the tank in order to safely run the SAT and/or ensure the property owner the maximum chance of passing the SAT.

The advantages of pumping the septic tank immediately prior to performing the SAT are summarized as follows:

  • SO THE BASEMENT WON'T GET FLOODED!: During a SAT, a considerable amount of water is added to the drainfield. If it is overfilled, it may back-up into the septic tank. If the septic tank is empty, the water will merely collect in the tank. However, if the septic tank is full (not pumped), the back-up from the drainfield may result in flooding the residence. When there is a significant drop in elevation from the house to the septic tank and/or drainfield, it may be physically impossible to cause a back-up. In such cases, it may be feasible to avoid pumping the septic tank. In most situations, there will be a potential for backing-up water into the house; therefore, the engineer will require that the septic tank be pumped. Under no circumstances should the drainfield be pumped, simply because it will reduce the chances of the drainfield passing an adequacy test (see next section).
  • PROPERTY OWNER CAN RESUME NORMAL WATER USAGE: After the drainfield is filled with the required amount of water, the field engineer may need to monitor (for up to 24 hours) the recovery of the drainfield. If the septic tank is empty, the property owner will be able to use water in the residence normally since wastewater will merely flow into the empty septic tank and not reach the drainfield. However, if the tank is full (not pumped), any water used in the residence will flow into the drainfield and adversely affect the results of the adequacy test. In short, if the tank is not pumped, the resident may need to severely restrict water usage for up to 24 hours.
  • PROPERTY OWNER SAVES MONEY!: The engineer will usually want to inspect the drainfield before the septic tank is pumped so that the normal operating level can be observed. In some cases, the engineer can visually determine that a drainfield is failed (operating with an excessive amount of water in it) without having to run the adequacy test, saving the property owner money. If the tank and/or the drainfield are pumped prior to the engineer’s inspection, the liquid levels will be artificially low, leading the engineer to believe an adequacy test is justified. Consequently, he/she will proceed with the test on a system that is certain to fail to meet the necessary absorption requirements.
  • PUMPING THE SEPTIC TANK PREMATURELY OR PUMPING LIQUID OUT OF THE DRAINFIELD CAN REDUCE THE CHANCE OF A SYSTEM PASSING THE ADEQUACY TEST: A drainfield fails progressively over its life of operation (see Failed Septic System?). This progressive failure causes the liquid level in the field to rise into the uncontaminated drainrock, where the liquid can be absorbed into surrounding soils. This rising liquid level also increases the pressure below the water line, increasing the absorption rate. This progressive failure occurs until the system becomes so full that it eventually backs-up into the residence or overflows onto the ground. When a drainfield is pumped, the liquid level is lowered to a level where the drainrock and soil interface is more contaminated and the absorption rate is less. In short, the level in the drainfield will have been lowered into the failed portion of the system. If the engineer is not aware of this condition, he/she will not introduce enough water into the drainfield to get it above the normal operating level, and into the cleaner portion of the system where water can be more easily absorbed. This same condition occurs when a septic tank is pumped in the week prior to an adequacy test. During the time the septic tank is re-filling (after being pumped), no water will reach the drainfield. This will allow for the liquid level in the drainfield to drop down into the failed region. In order to maximize the chance of passing an adequacy test, water should be added to a drainfield that is operating at its normal liquid level, so that it can be filled into the uncontaminated portion of the system.

Septic Adequacy Test

The septic system adequacy test is performed as follows:

  • The liquid level in the drainfield monitoring tube/s is measured
  • A hose and flow meter are connected to an outside faucet
  • The water is turned on and introduced into a drainfield clean-out or monitoring tube
  • The amount of water introduced and the rise in the liquid level are recorded throughout the filling period. This information is used to calculate the gallons per inch of rise.
  • Once the required amount of water has been introduced, the flow is stopped.
  • The drop in the liquid level is monitored for as long as 24 hours and the total absorption rate calculated.

The engineer then evaluates the data and determines whether the system meets municipal absorption requirements. The MOA considers the data from the adequacy test to be valid for up to two (2) years. Consequently, they will issue a Certificate of On-site Systems Approval based upon the data for up to two (2) years after the testing date. If the system is deemed to be failed, an upgrade is usually the recommended course of action.

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