Minnesota Pollution Control Agency 

Link to:Minnesota Pollution Control Agency Groundwater Information

 

NGWMN Contact:

Sharon Kroening

(651) 757-2507

sharon.kroening@state.mn.us 

 

The Minnesota Pollution Control Agency (MPCA) is a water-quality data provider to the National Groundwater Monitoring Network (NGWMN). MPCA is a state agency that monitors environmental quality, offers technical and finical assistance and enforces environmental regulations. MPCA maintains a network of about 270 monitoring wells and currently serves data from 133 well sites to the NGWMN Portal. MPCA took part in the 2010 NGWMN Pilot Program and has been an active contributor to the Network since 2016. 

MPCA provides water-quality data from the Cambrian-Ordovician, Sand and gravel (glaciated regions), and the Surficial aquifer systems.

 

NGWMN Products: 

NGWMN Minnesota Pilot Report

 

NGWMN Projects:

2016 Round 1: 6/1/2016 to 5/31/2018

Initial project to become a NGWMN data provider. Water-quality data from 127 wells was added to the NGWMN.

2020: 8/1/2020 to 7/31/2022

This project is to drill 5 new wells in the Cambrian-Ordovician aquifer system to fill gaps in the NGWMN.

 

NGWMN Presentations:

December 2016 presentation to SOGW

 

Site Selection and Classification

Site Selection 

The process used to select MPCA Ambient Groundwater Monitoring Network wells for the NGWMN closely followed the requirements specified by the NGWMNFramework Document and the NGWMN Tip Sheets.

The two main considerations when selecting sites for the NGWMN were that:

  1. The well was installed in an aquifer of national interest, and
  2. The site met the network's requirements.

When selecting MPCA sites for the NGWMN, it was recognized that the individual aquifers that comprise the Cambrian-Ordovician aquifer system are very productive, and the major aquifers within the Cambrian-Ordovician aquifer system (the St. Peter, Prairie du Chien-Jordan, Tunnel City/Wonewoc, and Mount Simon-Hinckley aquifers) were considered separately when determining the number of MPCA well sites to select for the NGWMN.

The preferred sites considered for the NGWMN met the baseline requirement of at least five years of data. The number of selected wells was based on the NGWMN's trend site density since all of the sites in the MPCA's network are scheduled for annual sampling. The NGWMN trend network density of 1-5 wells for every thousand square miles and the extent of each of the major aquifers in the state was used to determine the proposed number of sites for each aquifer.

Ninety-four wells installed in the sand and gravel aquifers were selected for the NGWMN. The selected wells represented the variety of urban land use settings and deep parts of these aquifers that are sampled by the MPCA's Ambient Groundwater Monitoring Network. Eighty of the selected wells intersected the water table underlying urban and undeveloped land. Fifteen of the selected wells were installed in commercial/industrial areas. Eighteen wells were selected in residential areas that use centralized sewer systems for wastewater treatment and disposal, and an additional eighteen wells were located in residential areas that use SSTS. Twenty-eight of the selected wells were located in undeveloped areas. The remaining wells primarily were installed in deep parts of the sand and gravel aquifers, and the depth of these wells ranged from 52 to 112 feet. The aquifer type also was consistent with the MPCA Ambient Groundwater Monitoring Network's design. Most of the wells selected for the NGWMN represented unconfined aquifers which is consistent with the MPCA's monitoring network design; however, one-half of the selected deep sand and gravel wells represented confined aquifers.

Most of the Upper Carbonate Aquifer and Cambrian-Ordovician system wells in the MPCA's Ambient Groundwater Monitoring Network were selected for inclusion in the NGWMN. The only well that was not selected had an unknown depth and no corresponding lithology information.

Four Upper Carbonate Aquifer wells were selected for the NGWMN. These were the same wells that were offered to the network in 2011 pilot study, and all of them were installed in the Galena aquifer. One well that originally was included in the pilot study, W0000143, was dropped from the NGWMN because there is no driller's log available for this well. The depths of these wells ranged from 52 to 340 feet below the land surface. Two of the wells represented confined conditions in the aquifer, and the other two wells represented unconfined conditions.

Thirty-three Cambrian-Ordovician aquifer system wells in the MPCA's Ambient Groundwater Monitoring Network were selected for the NGWMN. Three of these wells were from the St. Peter aquifer. The depths of these wells ranged from 49 to 172 feet below the land surface and primarily represented unconfined conditions. Twenty-five wells from the Prairie du Chien-Jordan aquifer were selected for the NGWMN and mainly were the same wells selected for the network during the 2011 pilot study. The depth of these wells ranged from 75 to 350 feet below the land surface. Sixteen of them were installed in the Prairie du Chien Group, and the remaining nine wells were installed in the Jordan sandstone. The wells also represented a mix of aquifer types. Eighteen of the wells represented confined conditions, and the remaining seven wells represented unconfined conditions. Five wells of the selected wells were installed in the Tunnel City, Wonewoc, or Mount Simon aquifers. The depth of these wells ranged from 125 to 940 feet below the land surface and all of them represented confined conditions. Three of the wells were installed in the Tunnel City Group, and the remaining two wells were installed in the Wonewoc and Mount Simon sandstones. The Mount Simon aquifer well was nested with one of the Tunnel City wells. The Wonewoc well, site identifier 453790, is slated for sampling in 2018. 

Site Classification

All wells selected for the NGWMN that had sufficient water-quality data were assigned to the "Background", "Suspected Changes", or "Documented Changes" subnetworks. The "Background" subnetwork contains wells located in areas where the water-quality represents the natural conditions. The "Suspected Changes" subnetwork contains wells located in areas where the land use has changed resulting in subsequent or anticipated water quality changes. The "Documented Changes" subnetwork contains wells located in areas where the groundwater quality is known to be degraded. The NGWMN requires that each well in the NGWMN undergoes a baseline process of five years of data collection in order to properly classify the well into each of these subnetworks.

The available nitrate and chloride data collected from each well were used to classify each well into the three subnetworks. In order for a well to be assigned to the "Background" subnetwork, the reported chloride concentrations were required to be less than 35 mg/L or the measured nitrate concentrations were required to be less than 1. In addition, the chloride to bromide ratio of the well water was required to be less than 200, which represents background conditions. The criteria used to assign sites to the "Documented Changes" subnetwork were that the nitrate concentrations exceeded 1 mg/L or the chloride concentrations were greater than 35 mg/L. The sites that were not assigned to the "Background" or "Documented Changes" subnetwork were assigned to the "Suspected Changes" subnetwork. This would include wells where the chloride/bromide ratios were greater than 200 and indicated a wastewater or water softener or deicing chemical source but had a chloride concentrations that was less than 35 mg/L.

For most of the wells selected for the NGWMN, the land use settings corresponded to the NGWMN subnetwork assignment. Over 80 percent of the shallow sand and gravel aquifer wells located in the various urban land use settings were assigned to the "Documented Changes" subnetwork, and the remainder were assigned to the "Suspected Changes" subnetwork. In contrast, over 85 percent of the shallow sand and gravel aquifer wells assigned to the "Background" subnetwork were located in undeveloped areas.

Similarly, most of the bedrock and deep sand and gravel aquifer wells selected for the NGWMN also were assigned to the "Documented Changes" subnetwork. Seventy-one percent of the deep sand and gravel aquifer wells, and seventy-eight percent of the bedrock aquifer wells selected for the NGWMN were assigned to this subnetwork. Only one of the deep sand and gravel aquifer wells and eight of the bedrock aquifer wells were assigned to the "Background" subnetwork. There were fewer "Background" subnetwork wells selected for the NGWMN compared to "Documented Changes" subnetwork wells because the MPCA's monitoring network primarily focuses on monitoring groundwater-quality conditions in areas that are most likely to be impacted by urban contamination sources.

 

Data Collection Techniques

MPCA collects field data according to the standard operating procedures found here. The sampling process used by the MPCA generally is consistent with the NGWMN Framework Document.

Briefly, the field staff uses standard groundwater sampling procedures to collect water from each well. Prior to sample collection, each monitoring well is purged using a submersible pump outfitted with new polyethylene tubing. While the well is purged of any stagnant water in the casing, field measurements of water temperature, specific conductance, pH, and the dissolved oxygen concentration in the water are made using a calibrated multiparameter meter. Water samples are drawn from each well for laboratory analysis only after these field measurements have stabilized. Water samples are collected to determine over 100 field and laboratory parameters. Each well is tested for field parameters, general chemistry, major cations, trace elements, and volatile organic compounds. These analyses either are conducted in the field by trained MPCA staff or sent to the MDH Environmental Laboratory. Each year, contaminants of emerging concern (CEC) samples also are analyzed in a subset of 40 wells from the network. The CEC samples currently are sent to SGS AXYS Analytical Services in Vancouver, Canada for analysis.

Water samples are collected from the wells in the MPCA's Ambient Groundwater Monitoring Network for the most of the chemicals on the NGWMN's standard, extended, and supplemental analyte lists. All field parameters are measured by MPCA staff using calibrated meters according to the standard operating procedure. The general chemistry, cation, trace element, and volatile organic chemical analyses are performed by the MDH Environmental Laboratory which is accredited by the US Environmental Protection Agency. All samples for chemicals of emerging concern, which are collected from 40 MPCA network wells each year, are analyzed by SGS AXYS Analytical Services, which is accredited for pharmaceutical and personal care product and triclosan analyses in water by the Canadian Association for Laboratory Accreditation and the Maine Center for Disease Control and Prevention, Department of Health and Human Services. The only constituents listed in the Framework Document that are not routinely analyzed by the MPCA's network are oxygen reduction potential and isotopes.

 

Data Management

MPCA manages data according to the standard operating procedures found here.

All NGWMN wells were assigned a site number that corresponds to the "Minnesota Unique Well Number." This is a well identifier that is unique within the State of Minnesota and issued by the Minnesota Department of Health (MDH) when a well installation permit is received. The data elements associated with describing the well location were provided as suggested in the well registry. This included the horizontal coordinates, national and local aquifer codes, and confinement status. The well construction and lithology information was provided to the NGWMN using web services developed by the MGS for the County Well Index (CWI). The CWI is the water well database for the State of Minnesota and contains information both raw and interpreted data derived from driller's logs. The water-quality data were provided to the NGWMN from the EPA's Water-Quality Exchange or WQX. This project did not provide any groundwater level data to the national network.

For this project, the MPCA coordinated with the Minnesota Geological Survey (MGS) to develop web services to the lithology and well construction data associated with the wells selected for the NGWMN. In the state of Minnesota, this information is stored in the CWI database which is jointly managed by the MGS and Minnesota Department of Health. CWI contains the construction and lithology information reported by the well driller as well as stratigraphy and lithology that were interpreted by the MGS as part of their investigations. The web service developed for the NGWMN contains the well construction information reported on the driller's logs and the MGS-interpreted stratigraphy and lithology. Some of the wells in the web service are missing stratigraphic or lithologic information because the MGS has not reviewed the driller's logs for all of the wells in the MPCA's Ambient Groundwater Monitoring Network.

 

Other Agency Information

Additional information on groundwater from the Minnesota PCA is available at: https://www.pca.state.mn.us/water/groundwater-data

This includes links to Recent reports, archived reports, fact sheets and summaries, and manuals. 

Data