Testing the Waters: North Carolina

Most of North Carolina's 240 public coastal beaches, which stretch along 320 miles of Atlantic waters, are located on barrier islands. The North Carolina Department of Environment and Natural Resources (NCDENR) administers the state's BEACH Act grant.

Investigating the Use of Rapid Test Methods in Carteret County

In 2012, several beaches in Carteret County are being monitored using quantitative polymerase chain reaction (qPCR), a DNA detection technique that has been used to get same-day results and issue beachwater quality notifications for pilot projects in California, Wisconsin, and New Jersey. Current approved methods for determining fecal indicator bacteria counts in beachwater depend on growth of cultures in samples and take at least 24 hours to complete, and there is a great deal of interest in technologies that can provide same-day beachwater quality results. If the Carteret County project is implemented, qPCR results will be compared with culture results in order to verify correlations between qPCR and culture methods at these locations.1

What Does Beachwater Monitoring Show?

In 2011, North Carolina reported 240 coastal beaches. Of these, 114 (48%) were assigned a monitoring frequency of once a week, and 126 (52%) every other week. In 2011, 1%2 of all reported beach monitoring samples exceeded the state's daily maximum bacterial standards of 104 colonies/100 ml for Tier 1 beaches, 276 colonies/100 ml for Tier 2 beaches, and 500 colonies/100 ml for Tier 3 beaches. The beaches with the highest percent exceedance rates of the state standards in 2011 were Park on Fish Factory Road in Southport (17%) and Waterway Park (14%) in Brunswick County; Sound Access at the intersection of E. Main Street and Tooley Street in Belhaven in Beaufort County (11%); North Side Mouth of Town Creek in Beaufort in Carteret County (11%); Intracoastal Waterway, beach area between marker #28 and marker #29 (10%), and Oak Island Wildlife ramp off Fish Factory Road (10%) in Brunswick County; Carolina Beach Inlet, north end of Carolina Beach in New Hanover County (10%); and Neuse River/Union Point in Craven County (10%).

Beaches in Pasquotank County had the highest exceedance rate of the state standard in 2011 (5%), followed by Pamlico (3%), New Hanover (2%), Beaufort (2%), Craven (2%), Carteret (2%), Brunswick (2%), and Pender (1%) counties. There were no exceedances in Bertie, Camden, Chowan, Currituck, Dare, Hyde, Onslow, Perquimans, and Tyrell counties. In this analysis, all reported samples were used to calculate the 2011 percent exceedance rates, including duplicate samples and samples taken outside the official beach season, if any.

* Please note that only samples from a common set of beaches monitored each year from 2007-2011 are included in the bar chart.

What Are North Carolina's Sampling Practices?

North Carolina's swim season is from April 1 to October 31. Monitoring occurs year-round but is less frequent during the off-season, and alerts and advisories are not issued during the off-season.3 Monitoring is conducted in the off-season because it can allow the beach program to find and correct bacteriological problems before the swim season begins.1

NCDENR conducts sampling and notification activities throughout the coastal waters of the state; these duties are not delegated to local authorities. Samples are collected in a variety of ways. Samples in the ocean surf are taken 16 feet from the sampler's body using a telescopic golf ball retriever in knee-deep water, 6 to 12 inches below the surface of the water. Approximately half of the samples are collected by boat, and these samples are taken in water that is 3 feet deep, 12 inches below the surface. Samples taken from piers must be taken in the most-used area, 6 to 12 inches below the water's surface.

North Carolina prioritizes its beaches for sampling on the basis of usage.1 Tier 1 beaches are adjacent to resort areas, public accesses, and sailing camps and are used on a daily basis. All ocean beaches are considered Tier 1. Tier 2 beaches are those in such areas as the intracoastal waterway, tidal creeks, and exposed shoals. People frequent Tier 2 sites mostly on weekends and usually access them by watercraft. Tier 3 beaches are used an average of four times per month, or less frequently but intensively for special events such as triathlons. North Carolina regularly monitors all of its beaches, including its Tier 3 beaches.

Beaches with storm drains that extend to the water's edge are sampled 10 feet on either side of the drain when practical. Beaches with storm drains that do not extend to the water's edge are sampled where the water flowing back down the beach from the previous wave meets the next incoming wave.3 States that deliberately sample near potential sources of pollution, such as storm drains, tend to have higher percent exceedance rates than states that don't. Lateral sampling to determine the extent of the bacteria plume from discharging storm drains after a storm is done in Dare County. Lateral sampling is also done at some sites when the running monthly geometric mean water quality standard is exceeded in order to determine the extent of the contaminated area.3 NCDENR samples after storm events, sewage spills, dredge disposal, and floodwater pumping to confirm safe bacteria levels before lifting preemptive advisories.1 States that monitor more frequently after exceedances are found and after storm or pollution events will tend to have higher percent exceedance rates and fewer total closing/advisory days than they would if their sampling frequency did not increase after storm or pollution events.

North Carolina also monitors for Karenia brevis, a marine algae responsible for causing "red tide," a type of harmful algal bloom. Once a K. brevis bloom is detected off the east coast of Florida, satellite imagery is used to locate the Gulf Stream. When the Gulf Stream comes near the North Carolina coast, sampling for K. brevis begins.1If nearshore K. brevis levels present a health concern, beach advisories will be issued, but as yet, such advisories have not been warranted.1

How Many Beach Advisories Were Issued in 2011?

Total advisory days for 22 events lasting six consecutive weeks or less decreased 75% to 126 days in 2011 from 496 days in 2010. For prior years, there were 233 days in 2009, 168 days in 2008, 123 days in 2007, 346 days in 2006, and 197 days in 2005. There was 1 extended event (47 days) and no permanent events in 2011. 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. All advisory days in 2011 were due to monitoring that revealed elevated bacteria levels.

On August 28, 2011, NCDENR issued a press release saying that there was an increased chance that beaches impacted by the rainfall and flooding from Hurricane Irene were contaminated with elevated levels of pollutants, and that anyone swimming at those beaches had an increased chance of becoming ill.4 The press release mentioned sewer overflows and floodwater pumping from coastal towns as potential sources of contamination during and after the storm. Two days later, NCDENR announced that water samples at New Hanover and Carteret county beaches had been tested and were meeting water quality standards for swimming.5 On September 1 it was announced that beaches in Brunswick, Pender, Onslow, and Currituck counties were meeting water quality standards, as were Dare County beaches from Kitty Hawk to the Oregon Inlet. At that time, Dare County beaches between the Oregon Inlet and Ocracoke couldn't be tested because of damage caused by Hurricane Irene.6 NCDENR does not report this type of blanket advisory to the EPA, so advisory days in this state summary do not include days associated with Hurricane Irene.

How Does North Carolina Determine When to Warn Visitors About Swimming?

NCDENR does not have the authority to close beaches; it issues alerts and advisories only. However, the state and county health directors do have the authority to close any body of water if necessary for the protection of public health.1 The public is notified of alerts and advisories through avenues that include the Internet and press releases, but signs are posted at the beach only for advisories. Also, advisory days are reported to EPA and included in this state summary, but alerts are not.

North Carolina uses the Enterolert® method for analysis instead of the membrane filtration method. Enterolert® produces bacterial counts in terms of most probable number (mpn) rather than colony forming units (cfu), but both of these values are intended to represent the number of viable organisms in a sample. From May 1 to September 30, North Carolina's water quality standards at its Tier 1 beaches are a single-sample maximum of 104 mpn/100 ml water and a geometric mean of at least 5 of the most recent regularly spaced samples within a 30-day period of 35 mpn/100 ml.1 This matches the EPA's criterion for designated beach areas. At Tier 2 beaches, the standard is a single-sample maximum of 276 mpn/100 ml, and at Tier 3 beaches, the standard is a single-sample maximum of 500 mpn/100 ml.7 North Carolina's single-sample maximum standard for Tier 2 beaches matches EPA's single-sample criterion for moderately used full-body-contact marine beachwater, and its standard for Tier 3 beaches matches EPA's single-sample criterion for lightly used full-body-contact marine beachwater.8 The geometric mean standard is not applied to Tier 2 and Tier 3 beaches. During April and October, the standard for Tier 1 beaches is generally the same as the standard for Tier 2 beaches.2 However, NCDENR generally opts to apply Tier 1 standards during those months if temperatures are warm enough for high recreational use.1

North Carolina has an elaborate process for determining when to issue a notification, based on its three tiers.

• Tier 1 beaches whose water quality exceeds standards more than just occasionally are sampled in triplicate, while other Tier 1 beaches have one sample taken per sampling event. For Tier 1 beaches that are sampled in triplicate, an advisory is issued without resampling when two out of three simultaneous samples exceed 104 mpn/100 ml. Between May 1 and September 30 at Tier 1 beaches that are not sampled in triplicate, an alert is issued for beaches when enterococcus levels are between 104 and 500 mpn/100 ml. A second sample is collected immediately when an alert is issued, and if levels in the resample exceed 104 mpn/100 ml, the alert converts to an advisory. It is rare for an alert at a Tier 1 beach to convert to an advisory, in part because alerts are rarely issued at these beaches, which have a history of good water quality. Resamples taken after an alert is issued almost never exceed standards. Alerts do not apply to beaches that are sampled in triplicate. An advisory is issued without a resample at Tier 1 beaches if a single sample is greater than 500 mpn/100 ml or if the geometric mean of at least five of the most recent regularly spaced samples taken over the space of 30 days exceeds 35 mpn/100 ml.
• For Tier 2 beaches, an alert is issued if a sample is between 276 and 500 mpn/100 ml, and a resample is conducted. This alert converts to an advisory if the resample level exceeds 276 mpn/100 ml. An advisory is issued without a resample at Tier 2 beaches if a single sample is greater than 500 mpn/100 ml.
• Alerts are not issued at Tier 3 beaches. Instead, Tier 3 beaches are resampled if fecal indicator bacteria levels are higher than 500 mpn/100 ml, and if the second sample is above that level, an advisory is issued.3

NCDENR observes fecal coliform results from the state's shellfish-growing waters in order to get an indication of water quality at nearby recreational sites, but fecal coliform results are not used to issue advisories or alerts.

During extreme rain events such as tropical storms and hurricanes, NCDENR sometimes issues blanket advisories that cover large regions or all of coastal North Carolina.1 This type of advisory is not reported to the EPA and does not appear in NRDC's data analysis. In addition, permanent signs are posted on either side of storm drain outfalls stating that swimming between the signs is not recommended and that waters may be contaminated by discharge from the pipe (NRDC data do not include this type of standing advisory).1 Otherwise, preemptive rainfall advisories (advisories issued after rain before monitoring results are available) are not issued, because according to the state, the beachwater quality monitoring data indicate that water quality at ocean beaches is not affected by rainfall except near storm drains. Preemptive advisories are issued after known sewage spills, when pumping of floodwaters between the primary dune and the ocean beaches occurs, or when dredge material from closed shellfishing waters is placed on ocean beaches.3

Notes

1. Why don't the 2011 percent exceedance values in this summary match? The value at the top of the first page (3%) reflects the proportion of samples exceeding the national single-sample maximum standard for designated beach areas. North Carolina applies this standard at its high-use Tier 1 beaches but applies EPA standards that are not as strict at its moderately and lightly used beaches (Tier 2 and Tier 3 beaches, which are generally accessible only by boat). The value in the "What Does Beach Monitoring Show?" section (1%) reflects the proportion of samples exceeding the state standards.
2. J.D. Potts, North Carolina Department of Environment and Natural Resources, personal communication, February 2012.
3. North Carolina Department of Environment and Natural Resources, North Carolina Beach Monitoring Project Quality Assurance Project Plan, revised July 28, 2009
4. North Carolina Department of Environment and Natural Resources, "Coastal Swimming Waters May Be Affected by Excessive Rains, Flooding from Hurricane Irene" (press release), August 28, 2011.
5. N.C. Department of Environment and Natural Resources, Bacteria Testing at New Hanover and Carteret Ocean Beaches Meet Swimming Standards (press release). August 30, 2011.
6. N.C. Department of Environment and Natural Resources, Bacteria Levels at Most Ocean Beaches Meet Swimming Standards (press release). September 1, 2011.
7. North Carolina Department of Environmental and Natural Resources. Coastal recreational waters monitoring, evaluation, and notification. 15A NCAC 18A .3400. Accessed at www.deh.enr.state.nc.us/shellfish/Water_Monitoring/RWQweb/images/15ANCAC8A3400Rules.pdf, January 2012.
8. US EPA. Ambient Water Quality Criteria for Bacteria - 1986. January 1986.
9. Reported closing or advisory days are for events lasting six consecutive weeks or less. Days in parentheses are for events lasting more than six consecutive weeks.