Groundwater often contains minerals (calcium, magnesium, iron, ect.), and other organic/inorganic substances that can effect its aesthetic quality. If the concentration of these substances are high enough, it may be necessary to install a treatment system in order to make the water suitable for household use. Common treatment systems include water softeners, greensand filters, and cartridge filtration systems. Most of the "contaminants" typically encountered in groundwater can be removed with these treatment systems; however, there are several contaminants, which, if encountered at excessively high levels, can significantly impact the viability of the well and the value of the property.
The three major contaminants that concern the Municipality of Anchorage ( MOA) are arsenic, fecal coliform bacteria, and nitrates. For extensive testing on the water water quality of a particular well, many buyers will have us pull a PIWA sample. PIWA is an acronym for Personal Individual Water Analysis. This extensive test is not required to obtain a COSA but performed by many homebuyers. The PIWA includes sampling for the following: Total Coliforms, Nitrate, Nitrite, Chloride, Sulfate, Fluoride, Aluminum, Arsenic, Barium, Cadmium, Calcium, Chromium, Copper, Iron, Lead, Magnesium, Manganese, Phosphorus, Potassium, Silicon, Silver, Sodium, Zinc, Conductivity, Total Dissolved Solids, Hardness (as CaCO3), Alkalinity (as CaCO3), and PH. Please visit our our COSA page for pricing details.
Arsenic is a very poisonous metallic element that occurs in natural deposits in the earth’s crust. It can dissolve in groundwater and be present in wells used for drinking water. Chronic exposure to arsenic levels over 10.0 parts per billion (ppb) has been linked to health complications, including cancer of the skin, kidney, lung, and bladder, as well as other diseases of the skin, neurological and cardiovascular systems.
The United States Environmental Protection Agency (EPA) has classified arsenic as a Class A human carcinogen (USEPA, 2000). The primary mode of exposure is ingestion of water containing arsenic. The EPA Maximum contaminant levels (MCLs) for arsenic is 10 parts per billion (ppb). Although private wells are not regulated by the EPA, the MOA policy, when issuing a Certificate of Onsite Systems Approval (COSA) for title transfer (sale of a home), is to issue an advisory notice if the Arsenic level in the well exceeds 5.0 ppb.
The presence of Coliform bacteria is an indicator of sewage contamination. If coliform bacteria are present, the water should be deemed unsuitable for human consumption until proven otherwise. Wells that are contaminated with coliform bacteria are not as prevalent as ones contaminated with nitrates, but there are a few of them out there. Again, research records on the neighboring wells, or arrange to pull samples if there is any reason to be suspect.
Nitrates are one of the by-products associated with the natural breakdown of organic material, such as wastewater. Nitrates are generally not toxic to adults, or children older than two or three; however they can have an adverse impact on infants, causing a condition referred to as methemoglobinemia, or "blue baby" disease. This condition occurs when nitrate in the water is converted to nitrite, absorbs into the bloodstream and bonds with the hemoglobin in the blood. This bond prevents the hemoglobin from carrying oxygen (its intended "job"), resulting in an oxygen deficiency in the infant. The State of Alaska Department of Environmental Conservation (ADEC) has adopted the EPA standard of 10 milligrams per liter (mg/l) as the maximum Nitrate level allowable. If a well has Nitrate levels of more than 10 mg/L, the standard practice is to install what is termed a "point-of-use (POU) treatment system on the sinks used as a drinking water source. There is no need to treat the water used for showers, toilets, hand-washing, laundary, or any other non-potable use.
Although there are simple treatment method available for removing nitrates from drinking water, such as reverse osmosis and anion exchange, wells which have nitrate levels above 10 mg/l can be subject to the following inspection requirements prior to issuance of a COSA:
A visual inspection of the well bore, using a down hole camera, performed by a certified well driller or pump installer, or engineer shall be used to evaluate the integrity of the casing and the well is cased, without perforations, to the required depth.
An evaluation of the annular seal around the well casing shall be performed by a certified well driller, pump installer, or engineer in accordance with procedures established under subsection F. Fluorometric dye and water shall be introduced into a temporary basin dug into the ground surface surrounding the well casing stick up. Well water samples for laboratory analysis shall be collected for a minimum of forty-eight (48) hours after dye is introduced and analyzed by a certified laboratory for the presence of the dye. Presence of the dye within forty-eight (48) hours is evidence of an inadequate annular seal around the well casing. The annular seal shall be deemed satisfactory if dye cannot be detected within the first 48 hours of introduction.
If the annular seal around the casing is determined satisfactory through dye testing, the Developmental Services Department (DSD) may issue a COSA provided the well is cased and un-perforated to a minimum depth of 40 feet and meets all other well code construction standards in place at the time the well was originally constructed. If the well does not meet the minimum 40 feet casing depth at the time approval is requested from the DSD, a COSA may be issued if the well is retrofitted with a pressure-grouted well liner installed to a minimum depth of 40 feet.
If water producing zones with greater than 10 mg/L nitrates are found below the well casing and there are also other water producing zones with less than 10 mg/L nitrates, the well will be retrofitted to eliminate cross connection between the water producing zones.
If the well casing or annular seal around the casing are determined to be inadequate or unsatisfactory, or if cross connections between water producing zones are found, the well must be repaired or modified to meet current well construction standards or the well must be decommissioned. After the well is brought up to applicable standards the DSD may issue a COSA. The DSD may require additional monitoring.
Upon completion of any rehabilitative well work, the temporary basin created around the well casing for the dye test shall be filled with a bentonite slurry and re-graded. The well must also be disinfected and retested for nitrates. *Per MOA COSA "Guidelines for Approval". Please contact the MOA for specific requirements.
It is important to note that nitrate levels can vary seasonally, typically being lower in the late spring/fall when the aquifer is recharged (nitrates are diluted with the increased groundwater) and higher in the middle of winter, when there is less water to dilute the nitrates present in the aquifer. In short, if you find a well to have nitrates concentrations approaching the (ADEC) maximum, in later spring/fall, the chances are that nitrate levels will be above 10 mg/l in the middle of winter.
When purchasing raw land, it is recommended that you research what the arsenic and nitrate levels are for the wells on adjacent developed properties. If current information is not available in the Municipal records at the DSD (907 343-7904) it may be worth obtaining permission from the neighbors to pull samples from their wells. Most labs charge a fee of about $100 (Year 2016) to run an arsenic and nitrate analysis. There are certain subdivisions which historically have had high nitrate and/or arsenic levels, and DSD, your Realtor, or your engineer should be able to enlighten you as to which subdivisions may require closer investigation.