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Feasibility Study <br />Water Treatment Plant <br />City of Lino Lakes, MN <br />WSB Project No. 015822-000 Page 7 <br />3.2.2 Maximum Contaminant Levels (MCLs) <br />Maximum Contaminant Levels (MCLs) are set by the United States Environmental <br />Protection Agency (US EPA) and enforced by MDH. All public water supplies in <br />Minnesota must meet these standards. MCLs are established through a scientific process <br />that evaluates the health impacts of the contaminant and the technology and cost <br />required for prevention, monitoring, and/or treatment. States are allowed to enforce lower <br />(more strict) standards than MCLs, but are not allowed to enforce higher (less strict) <br />standards. New MCLs or changes to existing MCLs are rarely made. <br />3.2.3 Health-Based Values (HBVs) and Health Risk Limits (HRLs) <br />Health-Based Values (HBVs) and Health Risk Limits (HRLs) are developed by <br />toxicologists at MDH using the best peer-reviewed science and public health policies <br />available at the time of their development. An HBV or HRL is the level of a contaminant <br />that can be present in water and pose little or no health risk to a person drinking that <br />water. HBVs and HRLs are developed to protect sensitive or highly exposed populations. <br />HBVs and HRLs are guidance used by the public, risk managers, and other stakeholders <br />to make decisions about managing the health risks of contaminants in groundwater and <br />drinking water. HRLs are guidance values that have been through the Minnesota <br />rulemaking process, which includes at least one public comment period for stakeholders <br />to provide feedback on the proposed guidance values. <br />3.2.4 Primary Drinking Water Contaminants <br />Primary drinking water contaminants are regulated contaminants that may pose an <br />immediate, or acute, risk to human health if they are found in drinking water. Primary <br />Contaminants include the following main categories of contaminants: <br />Bacteriological -Total coliform bacteria are common in the environment and are generally <br />not harmful themselves. The presence of fecal coliform bacteria and E. coli in drinking <br />water is serious because the bacteria are usually associated with sewage or animal <br />waste. The presence of these bacteria in drinking water generally is a result of a problem <br />with water treatment or the pipes which distribute the water and indicates that the water <br />may be contaminated with organisms that can cause disease (pathogens). <br />Nitrates - Nitrate is a man-made contaminant and also occurs naturally in the <br />environment, but elevated nitrate levels in drinking water are usually associated with the <br />use of fertilizer, or the breakdown of human and animal waste. It is a health concern <br />primarily for infants under the age of six months. If the federal standard for nitrate is <br />exceeded, an advisory is issued regarding consumption of the water by infants. The <br />advisory remains in effect until steps can be taken to correct the problem. Nitrates have <br />not been detected at significant concentrations in Lino Lakes’ water supply. <br />Disinfection Byproducts - Disinfection rids drinking water of microbiological organisms, <br />such as bacteria, viruses, and protozoa, that can cause and spread disease. The most <br />common method of disinfection is the addition of chlorine to drinking water supplies. <br />However, chlorine can combine with organic materials in the raw water to create <br />contaminants called trihalomethanes (THMs) and haloacetic acids (HAAs). Repeated <br />exposure to elevated levels of THMs over a long period of time could increase a person’s <br />risk of cancer. All community water systems that add a disinfectant to the water must <br />regularly test their treated water to determine if THMs and HAAs are present. If the THMs <br />or HAAs exceed the limits set by the U. S. Environmental Protection Agency (EPA), the <br />water system must take action to correct the problem. The corrective actions include <br />notifying all residents served by the water system. Disinfection byproducts have been <br />detected in Lino Lakes’ water supply but at concentrations that are significantly lower <br />than the MCLs for haloacetic acids and total trihalomethanes.