Buying a Lot - Well and Septic Concerns
Within the Municipality of Anchorage
The purchase of a lot that is not on public sewer or water involves many factors. Besides the view, access, neighborhood and other personal considerations, the prospective buyer needs to consider the feasibility of well and septic service on the lot.
Well water in sufficient quantity is an important consideration. In some area of the city wells are typically bedrock and of varying flow rate and depth. When a well is drilled at $25-30 per foot of depth, this is an important consideration. A lot purchaser can do their own research by accessing the records available at the Onsite Services department at the permit center at Tudor and Bragraw streets, between the hours of 7:30 and 5 pm. Records for developed lots in the area are kept on microfilm and can be copied. This will give you a general trend as to well depth and flow rates and possibly even water quality. The staff is also helpful in this area. Records are also now available on the web by clicking the link below.
General Information on the Onsite Services department is available at the link below: http://onsite.ci.anchorage.ak.us/scripts/LFWebLink.exe/weblink/default2.htm?templateID=2
The ability of the ground to accept the septic waste depends on the percolation rate of the soil and the ground water table levels. Some of this information can be obtained by a record search in the same office mentioned above, however to be sure that you have an adequate lot for your planned dwelling a test hole. percolation test and preliminary design should be undertaken by a registered engineer familiar with this work.
The typical sequence is to contact an engineer familiar with the area involved and provide them with the number of bedrooms of the dwelling and your proposed house location on the lot. This will typically require an onsite lot meeting. If the lot survey corners and boundary are distinguishable then the engineer can get by at this point with out a separate survey. If the corners or lines are unknown, if there are conflicts or possible conflicts with neighboring improvements, or if there is limited area on the lot, then a survey should be undertaken at this point to determine the exact lot line location and available area for a septic system. This is money well spent. Many times the location of the septic system over rides the well and even the home locations in terms of priority. You will want the septic system to be away from existing neighbor wells, low drainage features, surface waters, earth cut banks, steep slopes, driveways and located downhill of the house if possible. Usually there is one clear-cut location for the septic and it's reserve or replacement area.
The next step is to roughly locate the house, access driveway and the septic tank and leachfield locations. A test hole is precisely located so that it can prove out the area of the initial leachfield and a future replacement area
A test hole is then excavated as deep as possible or until the groundwater table is reached. A ground water monitor tube is placed in the hole to determine the stabilized water table level after 7 days. A percolation test is accomplished on a dug bench in a representative soil layer. The design of the leachfield is dependant on the soil percolation rate and water table level. A quick calculation can be made at this point and another hole excavated if needed. Sometimes more than one hole is required in order to prove out the replacement area or to explore the lot to determine if there are better soil conditions. A test hole is only good for a 30' radius when completing a design. This is a Municipal requirement. A preliminary design can be accomplished that is dependent on confirmation of the water table level.
The lot buyer can now expect to receive a report that includes, soil logs, percolation test results, and a short narrative that describes the situation and feasibility of this lot. Some lots are subject to variability in water table and therefore feasibility can change without predictability. The only way to guarantee the system can be installed as designed, in this case, is to install it immediately.
If there is an existing well on the lot it should be tested for flow rate and water quality.
NOTE: The land available for building in Anchorage decreases every year. Many lots platted prior to 1991 did not have to meet the rigorous inspection and testing procedures in place today for subdivisions and may not meet current code requirements for septic leachfield installation. It is increasingly important to have land parcels evaluated prior to purchase.
The basic testing procedure written above is the same for the valley except that the report is written entirely by the inspecting engineer and there is no government approval required.
There are other considerations to lot purchase such as zoning, access, setbacks, covenants, etc that are not discussed here but you should be aware of prior to lot purchase.