What is a well adequacy test (WAT) and why is performed? Typically, the purpose of a WAT is to determine whether a well is able to meet the production requirements established by the State of Alaska and/or the Municipality of Anchorage for the residence served. In some cases it will be necessary to meet even more demanding flow requirements in order to satisfy the lending institution, particularly the Federal Housing Authority (FHA).
State and Municipal Well Production Requirements:
Per State and Municipal regulations, a well must be capable of producing at least 150 gallons per day, per bedroom. This corresponds to the following minimum flow rates:
- Five (5) bedrooms: 0.52 gallons per minute = 750 gallons per day
- Four (4) bedrooms: 0.42 gallons per minute = 600 gallons per day
- Three (3) bedrooms: 0.31 gallons per minute = 450 gallons per day
- Two (2) bedrooms: 0.21 gallons per minute = 300 gallons per day
These minimum flow rates have been established to meet only household uses and do not account for watering lawns/gardens, washing cars, or filling your new king size Jacuzzi tub. Consequently, if the flow rate of the well meets only minimum standards, it may be necessary to install water storage tanks, which serve as a reservoir to supplement the well production during peak flow requirements. It is common for residential water systems with low producing wells to have 500-1000 gallons of water storage. These tanks are often located in a crawl space or in the garage. A storage tank, the supplemental jet pump, and the associated controls can add several thousand dollars to the water system cost.
Wells which do not meet the aforementioned minimum flow standards must be equipped with a water storage system. Per the 1998 Municipal well ordinance, if the flow rate is less than the required amount, but greater than 150 gallons per day, a 500 gallon storage tank is required. If the daily production of the well is less than 150 gallons per day, a 1000 gallon storage tank is required.
The primary reason for the storage tank is to allow for potable water to be delivered to the house on an as-needed basis. There are several companies that deliver potable water, typically charging a fee based upon the number of gallons purchased.
If the property is being financed by the FHA, the water system must be capable of producing at least 3 gallons per minute per dwelling unit. This corresponds to 3 gpm for a single family residence, 6 gpm for a duplex, and 9 gpm for a triplex (and so on......). If the well is incapable of producing this amount of water, the deficiency can be made up for by adding storage tanks.
Well Production Can Vary Seasonally:
It is important to know that well production can vary seasonally, and sometimes quite dramatically. Wells will typically produce better in the late spring, after the aquifer is recharged by the snowmelt, and in the late fall (mid October) after the aquifer is recharged from the August/September rains. It is also possible that well production will decline in the middle of the winter, because the aquifer is not being recharged by melting snow or rainfall. Given these facts, it is reasonable to assume that if a well barely meets minimum flow standards in late spring, there is a good chance that its production will be below minimum standards in January and February. If you are purchasing a property with a low production well, this fact will be of particular significance.
How Long is the Well Test Data Considered Valid?
The MOA considers that data from the adequacy test to be valid for up to two (2) years. Consequently, they will issue a HAA based upon the data for up to two (2) years after the testing date.
How is the Well Test Performed?
Prior to starting the test the field engineer removes the protective cover (called a sanitary seal) off of the top of the well and measures the distance from the top of the casing down to water. This measurement is typically made with an instrument called an acoustic well sounder (AWS). The AWS is placed over the top of the well and activated. The activated AWS bounces a sound signal down to the water level and back to the AWS where the distance is internally calculated and shown on an electronic display. This measurement is recorded by the field technician. The test then proceeds as follows: A hose is connected so as to by-pass any water storage tanks connected to the water system. This may require some plumbing modifications if it is not possible to isolate the storage tanks from the well.
A water meter is connected to the hose and the meter reading is recorded by the field technician.
The water is turned on. Throughout the pumping period the drop in the water level in the well is measured at numerous time intervals and recorded. In addition, the water meter readings are simultaneously recorded.
Pumping is continued until the well produces enough water to meet/exceed the required minimum daily flow rate. The flow is then turned off and the recovery of the water level in the casing measured and recorded at various time intervals, typically over several hours.
If the well runs out of water before the minimum flow rate can be established, the field engineer will deactivate the pump by turning off the electrical breaker in the house, and allow the well to recover for a period of time (typically about 30-60 minutes). The well will then be reactivated, deactivated, rested, and reactivated over several cycles, until the recovery rate can be established by the field engineer.
The above acquired data will be used by the engineer to establish well production rate.
What if My Well is Found to be Inadequate?
The performance of a low production bedrock well can often be enhanced by a process referred to as hydrofracturing. Hydrofracturing is performed by well drillers or well pump service companies. The objective of the process is to fill the well with water and pressurize it so as to fracture the surrounding bedrock and open up paths for groundwater to reach the well. Hydrofracturing costs several thousand dollars and is often successful in obtaining at least some increased production, however, there are no guarantees. If the well's production is still inadequate, the installation of storage tanks can be used to bring the water system into compliance with any regulatory and/or lending institution requirements.
I Am Selling or Refinancing My House. When Should I get the Well Tested?
If you are selling your house, it is recommended that you have the well tested as early as possible in the marketing process. This way, if there are any deficiencies, there is time to get them resolved to the satisfaction of the MOA, the lender, and most importantly, the buyer.