Minnesota 2012 Beachwater Quality Summary
Reported Sources of Beachwater Contamination
(number of closing/advisory days)
- 216 (55%) stormwater runoff
- 178 (45%) unknown contamination sources
Minnesota has 79 public beaches along about 58 miles of Lake Superior coastline. There are also a number of Lake Superior beaches that belong to the Grand Portage Tribe, which was the first tribe in the country to have a beachwater quality monitoring program. The Minnesota Lake Superior Beach Monitoring Program is fully administered by the Minnesota Department of Health; the Grand Portage Beach Monitoring Program is fully administered by the Grand Portage Tribe.
What Are the Water Quality Challenges and Improvements in Minnesota?
Flooding Caused by Heavy Rains
Duluth and surrounding areas experienced unprecedented flash flooding after record-breaking rain fell on June 19 and 20, 2012. Nearly 10 inches of rain fell in some areas; nothing comparable had occurred since 1876. The governor declared a state of emergency as flooding forced the evacuation of 250 residences, roads and bridges were washed out, and several zoo animals died. The flooding also caused Duluth’s sewage system to fail and triggered a statewide health advisory and closure for all Lake Superior beaches for two days. It caused an estimated $80 million in damage to Duluth’s public infrastructure alone.
What Does Beachwater Monitoring Show?
In 2012, Minnesota reported 92 coastal beaches, of which 7 (8%) were assigned a monitoring frequency of more than once a week and 46 (50%) once a week; 39 (42%) were not assigned a monitoring frequency. In 2012, 12% of all reported beach monitoring samples exceeded the state’s daily maximum bacterial standard of 235 colonies/100 ml. The beaches with the highest percent exceedance rates of the state standard in 2012 were Park Point 20th Street/Hearding Island Canal Beach (47%), Park Point Sky Harbor Parking Lot Beach (32%), and Park Point New Duluth Boat Club/14th Street Beach (31%) in St. Louis County; Grand Portage Bay Monitoring Location 6 (29%) and Grand Portage Bay Monitoring Location 2 (22%) in Cook County; Agate Bay Beach in Lake County (21%); and 42nd Avenue East Beach in St. Louis County (20%). St. Louis County had the highest exceedance of the state standard (16%) in 2012, followed by Cook (9%) and Lake (6%). NRDC considers all reported samples individually (without averaging) when calculating the percent exceedance rates in this analysis. This includes duplicate samples and samples taken outside the official beach season, if any.
Minnesota Percent of Samples Exceeding the State's Daily Maximum Bacterial Standard for 47 Beaches Reported 2008-2012*
* Please note that only samples from a common set of beaches monitored each year from 2008-2012 are included in the bar chart.
What Are Minnesota's Sampling Practices?
The Minnesota Department of Health (MDH) monitors beaches from the week before Memorial Day to the end of September, with some beaches not monitored until June due to cold weather. The state determines sampling practices, locations, standards, and notification protocols and practices at the beaches monitored under the program. Water quality at beaches in the Grand Portage Reservation, located on the north shore of Lake Superior near the Canadian border, is monitored in a program separate from the state’s Lake Superior Beach Monitoring Program.
MDH collects samples at a depth of 6 to 12 inches in water that is knee deep, while samples in Grand Portage are collected in water that is 2.5 feet deep. Beaches monitored by the state program are assigned high, medium, or low priority, depending on the potential for impacts from stormwater runoff, bather loads, and waterfowl populations as well as proximity to concentrated animal feeding operations and wastewater treatment discharges.
When an MDH beach is placed under advisory, monitoring occurs daily (Monday through Thursday) until the site meets water quality standards. States that monitor more frequently after an exceedance is found will tend to have higher percent exceedance rates and lower total closing/advisory days than they would if their sampling schedule did not increase after an exceedance was found.
The Park Point Southworth Marsh Beach is no longer monitored due to its increasing unsuitability for water recreation.
How Many Beach Closings and Advisories Were Issued in 2012?
Total advisory days for 57 events lasting six consecutive weeks or less more than tripled to 394 days in 2012 from 121 days in 2011. The duration of advisories was shorter at the majority of beaches; however the number of beaches with one or more advisories rose sharply from 2011. This change is likely due in part to the flood event that occurred in June and affected the entire Minnesota Lake Superior shoreline. For prior years, there were 61 days in 2010, 99 days in 2009, and 257 days in 2008. In addition, there were no extended or permanent events in 2012. Extended events are those in effect more than six weeks but not more than 13 consecutive weeks; permanent events are in effect for more than 13 consecutive weeks. For the 57 events lasting six consecutive weeks or less, 80% (314) of closing/advisory days were due to monitoring that revealed elevated bacteria levels, and 20% (80) were preemptive due to heavy rainfall.
How Does Minnesota Determine When to Warn Visitors About Swimming?
The Lake Superior Beach Monitoring Program does not issue beach closings; its policy is to issue advisories only. The Grand Portage Tribe, however, does issue closings. Minnesota applies a single-sample maximum E. coli standard of 235 cfu/100ml and a geometric mean E. coli standard of 126 cfu/100ml for the most recent five samples collected during a 30-day period. When a sample exceeds either the single-sample or the geometric mean bacteria standard, an advisory is issued. Advisories are posted on the Minnesota Lake Superior Beach Monitoring Program website and are available through a 24-hour hotline. Additionally, signs are posted on the beach and news releases are sent to the media to alert the public to health advisories. There is no protocol for delaying or forgoing an advisory when a sample exceeds standards. The Grand Portage Tribe applies the same water quality standards as the state.
Because traditional processes for determining bacteria levels in beachwater take a day to complete, beachgoers don’t know if the water they are swimming in meets quality standards until the following day. Consequently, there is a great deal of interest in techniques that will allow for faster notification of water quality issues. Among these is Virtual Beach, a software package that can be used to develop beach-specific models for predicting fecal indicator bacteria levels in real time based on easily measurable beach conditions such as wind, current, and waves. Previously collected data on beach conditions and bacteria counts are fed into the software to create a model that predicts beachwater quality based on the most important variables.
Minnesota is working to gather the inputs needed for Virtual Beach and to build a model for certain beaches. The Grand Portage Tribe is planning on using predictive models at Grand Portage Bay locations 1, 2, and 2.5. Minnesota has no preemptive rainfall standards but does post advisories after known sewage overflows or other events that are considered likely to result in high bacteria levels. In addition, the public is advised to wait 24 hours before going swimming after rainfall in urban areas.
Minnesota 2012 Monitoring Results and Closing/Advisory Days