Groundwater Concerns for the Redeye River Watershed Redeye River - - PowerPoint PPT Presentation

Groundwater Concerns for the Redeye River Watershed

Redeye River 1W1P Meeting May 23, 2019 George Minerich, MDH – Drinking Water Protection

GRAPS

Interagency Effort One Coordinated Voice on Groundwater

Background Information

Land Cover /Land Use Geology/ Hydrogeology Pollution Sensitivity (Aquifer Vulnerability) Drinking Water Information Groundwater Withdrawals/Use

3

Groundwater Quality Information

Nitrate Contaminated Sites Arsenic · New Well Samples SSTS Pesticides Animal Feedlots

4

· Active Tank & Leak Sites · Closed Landfills · Ambient Monitoring · Private Well Sampling Initiative

· New Well Samples

· Private Well Sampling Initiative · Ambient Monitoring

Groundwater Quantity Information

Surface Water vs. Groundwater Water Level Trend Interpretation

Groundwater Use Trends

Trout Streams Calcareous Fens Lakes

Animals Plants Native Plant Communities

Groundwater Connected Features

5

Wellhead Protection Planning

• Eight of the nine community public water systems, within the RRW are

engaged in the wellhead protection planning process or are implementing their plans. Of the eight systems with approved plans, the vulnerability varies across the watershed from very low to high.

• Two of the approved wellhead protection plans exhibit a high vulnerability in

their DWSMA and considered vulnerable to contamination from the land surface, with all others exhibiting moderate to low vulnerability.

• Verndale is experiencing elevated nitrate conditions, one well exceeding

10mg/l nitrate (closed by MDH order) the other above 5mg/l and climbing. City installing nitrate treatment plant.

Redeye Water Supply Management Areas

• Drinking Water Supply Management
• Areas. There are 14 approved

Drinking Water Supply Areas (DWSMA) for community public water supply systems in the watershed.

6/7/2019 9

Private Wells

• The RRW has 2,135 private wells

with known locations ranging from 12 feet to 415 feet deep that provide drinking water to residents. Private well users are not afforded the same water quality safeguards as people who get their water from public water systems.

10

Pollution Sensitivity of Near Surface Materials

• This figure is an estimate of time it

takes water to infiltrate the land surface to a depth of 10 feet.

Redeye Pollution Sensitivity of Wells

Sensitivity rating and the associated recharge travel times for surficial and buried aqu Pollution Sensitivity Aquifer Recharge Time Period Aquifer Recharge Time Period Rating for Surficial Aquifers for Buried Aquifers High Hours to a week Days to Months Moderate A week to weeks Years to one or two decades Low Weeks to a year Several decades to a century

Public Health Issue: Nitrate

6/7/2019 13

Aquifer vulnerability Nitrate in new private wells (1991-2016)

Source: MDA Source: MDH Source: MDH

Percent of population served by CWS

mg/L mg/L

Nitrate

• Contamination problems that arise from human activity sources. Large areas of MN

geologically vulnerable to groundwater contamination from surface activities (prior map).

• Nitrate is one example: We are concerned about nitrate because infants that drink water or

formula made with nitrate-contaminated water can develop a condition known as blue baby syndrome, which reduces the oxygen supply in their blood. Nitrate levels are highest in the geologically vulnerable area of state (2nd map).

• We also see that the counties least served by CWS are those in the geologically vulnerable

Central Sands region (3nd map).

• Fertilizer applied to land used for row-crop production is biggest influence on MN’s nitrate
• levels. Global markets continue to drive up the amount of MN farmland devoted to corn and

soybeans, which require high fertilizer input to maximize yield. . We are highly agricultural state - MN currently ranks 3rd and 4th in nation in corn and soybean acreage respectively.

6/7/2019 Optional Tagline Goes Here | mn.gov/websiteurl 14

Nitrate

• Nitrate-nitrogen (referred to as nitrate) is a

compound that occurs naturally and has many human-made sources. When nitrate levels are above 3 milligrams per liter (mg/L) in groundwater, human activity is the likely cause (State of Minnesota Workgroup). Human-induced sources of nitrate include animal manure, fertilizers used on agricultural crops, failing SSTS, fertilizers used at residences and commercially, and nitrous oxides from the combustion of coal and gas.

• Nitrate is one of the most common contaminants of

groundwater in Minnesota and is a public health concern where found in groundwater used for drinking water. The SDWA standard for nitrate in drinking water is 10 mg/L. Most of the samples taken from wells within the watersheds did not exceed the SDWA standard for nitrate.

Table 1: Summary of nitrate results in drinking water wells of the Redeye River Watershed.

Depth Completed Range (feet) Total samples (nitrate) Minimum concentration (mg/L) Maximum concentration (mg/L) Median concentration (mg/L) Samples at or above 3 mg/L (%) Samples at

• r above 10

mg/L (%) < 50 165 17.72 0.5 26.7 3 50 - 99 697 24.3 0.5 6.3 2.7 100 - 149 352 10.04 0.5 2.6 0.3 150 - 199 158 7.1 0.5 1.9 >= 200 116 2.35 0.5 Total 1488 24.3 0.5 6.7 1.7

High levels of nitrate are present in areas where there are both human-caused sources of nitrate and high pollution sensitivity. The absence of elevated nitrate concentrations throughout most of the watershed may be a function of low-impact land use near the wells or the presence of favorable geochemical conditions in the aquifers

Public Health Issue: Arsenic & Manganese

6/7/2019 17

Percent of new private wells >10 µg/L arsenic by county, Aug. 2008-Jul. 2013 Probability of manganese >100 μg/L in groundwater

Source: MDH Source: MDH

Naturally-occurring contaminants:

• Arsenic: Arsenic exposure is associated w/increased risk of cancer of the bladder, lungs, liver, and other
• rgans; nervous system problems, skin effects, high blood pressure, and reduced intelligence in
• children. State-wide, 11% of wells exceed max contaminant level established for PWS. >11% in about

half of MN counties.

• Manganese: Can cause neurological problems, including learning and behavior problems in infants and
• children. In 2012, MDH developed “tiered” water guidance for manganese to provide an appropriate

level of health protection for different groups based on age-related susceptibility to the harmful effects

• f manganese. The guidance is:
• •100 μg/L for infants 12 months of age or younger who are drinking the water
• •300 μg/L for exclusively breast-fed infants, children older than 12 months and adults.
• Based on a statewide sample of >9,000 private wells in Minnesota, about half (49%) are estimated to

exceed the 100 μg/L guidance value for manganese. Manganese distribution in groundwater is highly variable throughout the state - many areas have concentrations consistently above 100 μg/L (2nd map).

6/7/2019 Optional Tagline Goes Here | mn.gov/websiteurl 18

MDH Priority Concerns:

• Prioritize Drinking Water Supply Management Areas in the Redeye River

Watershed 1W1P.

• Prioritize Sealing Abandoned Wells
• Prioritize Protection of Private Wells
• Prioritize Protecting Noncommunity Public Water Supplies
• Prioritize protection activities in highly vulnerable DWSMAs where there are

not currently water quality impacts to drinking water aquifers.

6/7/2019 20

Existing Landscape:

• Protection of existing land – plan development
• Natural Vegetation – keep intact when possible
• Water Quality - "The movement of water between ground water and surface

water provides a major pathway for chemical transfer between terrestrial and aquatic systems“ (USGS Circular 1129)

• What happens in the watershed directly effects what we drink!

6/7/2019 21

Questions?

6/7/2019 22