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HomeMy WebLinkAbout20070604 - VII-3 VII-3 MEMO To: Honorable Mayor and City Council From: Tom Montgomery Date: May 30, 2007 Re: Public Hearing - Wellhead Protection Plan A public hearing has been scheduled for the June 4th City Council meeting on Part II of the City's Wellhead Protection plan. John Greer with Barr Engineering will make a presentation and be available to answer questions. I have enclosed some background information on the Wellhead Protection plan. The Wellhead Protection Plan requirement is a State mandate managed by the Minnesota Department of Health (MDH). The intent of the program is to protect our groundwater supply by developing education and management programs covering the ground surface area where a spill would infiltrate the aquifer and be drawn into our municipal water supply wells within a 10 year period - defined as our Drinking Water Surface Management Area (DWSMA). Part I of the Wellhead Protection Program was to delineate our DWSMA, which was accomplished through extensive ground water modeling and pumping tests. A map illustrating our DWSMA is enclosed with the Wellhead Protection background information. Our DWSMA covers about 2/3 ofthe City, and includes a large area outside of the City limits. The required Part I public hearing was held at the October 6, 2003 City Council meeting. Part II of the Wellhead Protection Plan includes requirements for maintaining a potential contaminant source inventory - a list of storage tanks, dump sites, hazardous waste generators, private and public wells, septic systems and chemical spill sites within our DWSMA. Other plan components include educational programs, land use controls, continued coordination with Dakota County and the Hastings Area Nitrate Study (HANS) goals and activities, and storm water management activities to promote storm water quality improvements. No Council action is required. The Wellhead Protection Plan has been reviewed by the MDH, who will be notified upon fulfillment ofthe public hearing component. Final MDH approval ofthe plan is expected later this summer at which time the Public Works will begin performing the annual activities required in the plan and submitting an annual report to the MDH on these activities. ern' OF HASTIN6S ...... ~ ;"\ ~ ~~ ~ c .c ~ ~" OJtt: iU;'; 8 r-..' !:::! ".. t-.... = Ole:: "Cl'. 0 ~ ~ '-~ ~ 0 G =.Cl '" 1;Ij ==...c;:::) =:::= ~ ~ ~ ~ ...~ ~ ~ <::::> ~ CI> = ~ co Q,) >. = to twHJ .... ~I ~ ~~-< >. =- ~ i3> == ",..... ", >. e:= - ;.:: ~ ~ :'iI "ill ~ Q;t = :: = .- 1.0 "'C ~ ~ ~ ~ Q. QJI .S! ~ "- .Cl c::i ,,+ ai ~ ._ ,~"" ~ iIi;: Q. =... = " = ~ 0 ~ ~ ~ ..... = =.... .. - . ~ _ ~ ~~~ (/l='s ~ ftJ~ 1~ ~ rI:J ~ ~ .. ~ 0 - .. c ')~ ~ Q(l ~ ~ "':: ~ ~ ~ > := :; ~~ ~ =:!:::! ~ ~ ~ ~ ~ -< -< ;;.-.> 0 ~ ~ ~~~ ~~~~~ ~~ =:~~ii' ~e~~~ >.. .t ~ ~ ~ Po. r..1 ~ Q Q " :I: t!"\ '" == ODD' := 1/ ~ ~ ;;;) @ c.... >:I: 0 , ._, ~ .~ . ~ " '--;' 1..." "J"'" :!II ~ --~ -~r' ,\, 4\ "-~' ',' <io\..' ~ ,:,,"-.;'~~ ~ "- 'v'""- 1-: ~---,"1--- " '" . ~ ~ . ','. 'i~.'" "- 't ',lli.1 ,r:: :"; ,.. ~~ ." '" ~ ~ ~ ~ ... ... Minnesota's Wellhead and Source Water Protection Program This document provides a short summary of the State of Minnesota's Wellhead and Source Protection Program (a.k.a. the Wellhead Protection Program). Program Background The State of Minnesota's Wellhead and Source Water Protection regulations are covered in Rule 4720, administered by the Minnesota Department of Health (MDH). Wellhead and Source Water Protection Plans are mandated by these regulations. Preparing a public water supply's Wellhead and Source Water Protection Plan is a two-part process. Part I of the process includes: . Scientific delineation of well capture zones for a specified groundwater travel time not less than 10 years, which then defines the Wellhead Protection Area (WHPA) . Designation of a Drinking Water Supply Management Area (DWSMA) . Vulnerability assessment for the public water supply wells, and . Vulnerability assessment for the aquifer(s) within the DWSMA tapped by the public water supply wells. Part 2 of the process includes: . An inventory of potential groundwater contamination sources within the portions of the DWSMA classified as vulnerable to contamination and . Development and implementation of a management plan to reduce the risk of contamination of the drinking water supply. The following section is a step-by-step description of this process. Part 1 Initial Scoplng Meeting The Wellhead Protection process begins with a meeting between the public water supplier and MDH. At this meeting, MDH staff summarize the Wellhead Protection process and give the public water supplier an idea of the data resources available through MDH. The public water supplier must designate a person to be the Wellhead Protection manager, responsible for seeing that the plan is developed and implemented. At this meeting, MDH staff will also help the public water supplier determine the type of delineation method appropriate for the community's hydrogeologic setting and well use. An initial assessment will be made as to whether sufficient data exists to meet the Rule's requirements for a pumping test. MDH will send the public water supplier a scoping decision notice within 30 days of the meeting, identifying the delineation method and whether a pumping test is needed. Pumping Tests In almost all cases, MDH will require a pumping test and, in some cases, more than one pumping test in the source water aquifer. A typical test involves coordinating the time of the test so as not to interfere too much with water supply demands and well use, installing automatic water-level measurement devices in BaIT Engineering Company 1 at least one well (near the pumping well) that is not being pumped, and careful monitoring of the pumping rate to assure that fluctuations in the rate will be small. It is best to perform the pumping test early in the process and definitely before work on the groundwater modeling described in the next section gets too far along. Analyzing pumping test data to determine aquifer transmissivity is not difficult but takes some specialized training and software. WHPA Delineations Wellhead Protection Areas (WHPAs) must be delineated with consideration of five criteria: (I) hydrologic boundaries; (2) ambient groundwater flow field (direction); (3) groundwater time-of- travel; (4) aquifer transmissivity; and (5) daily volume of water pumped. In almost all cases, the delineation method involves a combination of hydrogeologic mapping and computer modeling. A well- constructed groundwater flow model will account for all five criteria. The resulting delineations must, at a minimum, show the one-year and ten-year "groundwater time-of- travel areas" for each well. These are the areas in which it takes less than or equal to one year and less than or equal to ten years for water in the source water aquifer to reach the well. The "ambient groundwater flow field" describes the slope of the water table (or piezometric surface in the case ofa confined aquifer) and the direction of flow. This is typically in the form ofa contour map of the water table from published sources and from database records of water levels. The groundwater model is calibrated to these data. The "aquifer transmissivity" is a measure of the aquifer's ability to allow groundwater to move, with groundwater typically moving faster in aquifers with high transmissivity. Transmissivity must be estimated from a pumping test performed for each well field or, away from the well field, estimated using specific capacity data available from databases. Transmissivity is affected by the physical characteristics of the aquifer. The groundwater model must be of sufficient regional extent to include major hydrogeologic boundaries, such as major rivers. The pumping rate of each well has a significant effect on the size and shape of the WHP A. Minnesota Rule 4720 has specific requirements on how pumping rates must be determined. The pumping rate must be a daily average of the highest annual average pumping rate from the past five years or projected five years into the future. How that future pumping is projected can have a major impact on the size and shape of the WHPA. In the first submittal to MDH, the method of WHP A delineation must be described in detail and computer data files must be delivered to MDH. It is essential that those performing the computer modeling for the delineations work closely and regularly with MDH staff throughout the project so that there are no surprises during the review. Designation of the DWSMA The Drinking Water Supply Management Area (DWSMA) is determined after the WHPAs are delineated. Barr Engineering Company 2 The DWSMA defines the management area for protecting the drinking water supply and must encompass all the 10-year groundwater time-of-travel WHP A zones and must have boundaries that are easily identifiable on a map. DWSMA boundaries typically are defined using roads, parcel boundaries, and political boundaries. Geographic information system (GIS) procedures are useful in defining the DWSMA. Well Vulnerability Assessments A well vulnerability assessment must be performed for each municipal water supply well in the system to evaluate several criteria. A well is considered vulnerable to contamination if: . The well water contains 10 mgIL or more of nitrate+nitrite nitrogen . The well water contains quantifiable levels of either pathogens or chemical compounds that indicate groundwater quality degradation . Water from the well contains one tritium unit or more when measured with an enriched tritium detection method or . An enriched tritium analysis of the well water has not been performed in the past 10 years, and either information on well construction is not available or the geologic materials between the land surface and the well screen are conducive to rapid vertical migration of contaminants. Aquifer Vulnerability Assessments An aquifer vulnerability assessment is performed only inside the DWSMA, but data outside the DWSMA may be useful in performing the assessment. This assessment is important because the types of potential contaminant sources that must be included in the inventory performed in Part 2 vary depending on the DWSMA vulnerability. The vulnerability assessment involves evaluating the soil/rock types between the land surface and the source water aquifer using well logs from existing wells within the DWSMA. A map is prepared showing parcel boundaries, roads, and political boundaries and various zones of vulnerability within the DWSMA. First Submittal to MDH The first submittal to MDH contains the WHPA and DWSMA delineations and the vulnerability assessments. A typical submittal will contain: . A description of the Conceptual Hydrogeologic Model, . A detailed description of the groundwater model, including model development, data, parameter selection, model calibration, sensitivity analyses, uncertainty, and data files, . Maps of the WHP As with travel times of I year, 5 years, 10 years, (and 20 years if the Public water supplier so chooses), . Maps of the DWSMAs showing parcels and streets, . Well vulnerability assessments, . Aquifer vulnerability assessment, including a description of the method, two geologic cross sections through the well field, and a parcel map showing the various levels of vulnerability. . Appendix describing the pumping test method, data, and analyses, . Appendix describing the method for selecting the pumping rates and projecting future pumping rates. A copy ofthe map that accompanied the MDH's approval of Part I of the Hastings Wellhead Protection Plan is attached to this document. Barr Engineering Company 3 Part 2 Second Seoplng Meeting Part 2 of the Wellhead Protection process begins with a second scoping meeting between the public water supplier and MDH, at which MDH staff summarize the Part 2 requirements and give the public water supplier an idea of the information required in the management plan developed during Part 2. MDH staff will also identifY the data elements that must be addressed in the management plan. If the DWSMA delineated during Part I has more than one vulnerability zone, MDH staff will identifY potential contaminant sources that must be included in the inventory for each aquifer vulnerability zone in the DWSMA. MDH will send the public water supplier a scoping decision notice within 30 days of the meeting, in which it will identifY the information that must be used to prepare the management plan, information that must be submitted to the Department as part of the plan, and the deadline for submitting the management plan to the Department. Potential Contaminant Source Inventory An inventory of potential contaminant sources within the DWSMA must be compiled. These include privately owned wells completed in the source water aquifer, hazardous waste generators, properties with storage tanks, dump sites, Class V injection wells (i.e., disposal pits connected to floor drains from auto repair shops), and chemical release sites. Privately owned wells are considered potential contaminant sources because, if not properly constructed and maintained, they can provide a pathway for contaminants to migrate from the surface to the source water aquifer. Typically, only privately owned wells and Class V injection wells are included in the inventory for a DWSMA, or portion thereof, if its vulnerability to contamination is classified as "low." Only privately- owned wells, Class V injection wells, and properties with storage tanks are typically included in the inventory for a DWSMA, or portion of one, if its vulnerability is classified as "moderate." All potential contaminant sources must be included in the inventory for a DWSMA, or portion of one, if its vulnerability to contamination is "high" or "very high." Information on the location of potential contaminant sources is available from various state and county databases. This information is generally compiled and mapped using GIS techniques, after which it must be verified. Verification may involve contacting property owners and conducting windshield surveys of properties; this can be done during development of the management plan or identified as one of the strategies in the plan. Management Plan Development The management plan includes a discussion of the data elements identified in the second scoping decision notification from the MDH. In addition to complying with Rule 4720, the management plan must address criteria related to hydrologic management of water, health and environmental protection, and management. As defined in Rule 4720, criteria related to hydrologic management of water include: . Upgradient and downgradient effects on groundwater by actions impacting water and related land resources, . Interrelationships between surface water and groundwater, land and water use, and quality and Barr Engineering Company 4 quantity of water, . Effects of potential variations in precipitation. As defined in RuIe 4720, criteria related to health and environmental protection include: . Prevention of potential water and related land resource problems, . Anticipated improvements in the overall quality of the environment, . Public health and safety, . Potential cumulative effects of past, present, and future, actions. As defined in Rule 4720, criteria related to management include: . Estimated cost of implementing the wellhead protection plan, . Methods used to fund the wellhead protection plan, . Ways that wellhead protection planning is coordinated with other related planning programs, . Approaches used to identifY problems and opportunities. Strategies for addressing potential contaminant sources within the DWSMA are presented in the management plan. These strategies may include public education initiatives, sponsorship of household hazardous waste collection days, encouragement of best practices for handling of hazardous waste, ordinances restricting water use for activities such as lawn watering, ordinances regulating construction of new privately-owned wells and/or sealing ofuoused wells, periodic updating of the potential contaminant source inventory database, and gathering of new geologic information for future revisions/amendments of the Wellhead and Source Water Protection Plan. Barr Engineering Company 5