North Carolina 2012 Beachwater Quality Summary
Reported Sources of Beachwater Contamination
(number of closing/advisory days)
- 55 (60%) stormwater runoff
- 44 (48%) wildlife
- 8 (9%) unknown contamination sources
(Totals exceed total days and 100% because more than one contamination source was reported for some events.)
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.
What Does Beachwater Monitoring Show?
In 2012, 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 2012, 1% of all reported beach monitoring samples exceeded the state's daily maximum bacterial standard of 104 colonies/100 ml (276/100ml for Tier 2 beaches and 500/100ml for Tier 3 beaches). The beaches with the highest percent exceedance rates of the state standard in 2012 were Waterway Park in Brunswick County (10%), "Sound Access at the Intersection of E. Main St. and Tooley St. Belhaven" in Beaufort County (9%), "Vehicle Access, 600 yds. N. Carolina Beach Pier at Dune Mark" in New Hanover County (8%), and Jockey's Ridge Soundside Access in Dare County (8%). Beaufort County had the highest exceedance rate of the daily maximum standard in 2012 (2%), followed by New Hanover (1%), Dare (1%), Carteret (1%), Brunswick (1%), Craven (1%), Pender (1%), and Onslow (<1%). There were no exceedances in Bertie, Camden, Chowan, Currituck, Hyde, Pamlico, Pasquotank, Perquimans, and Tyrell Counties. 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.
North Carolina Percent of Samples Exceeding the State's Daily Maximum Bacterial Standard for 229 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 North Carolina's Sampling Practices?
North Carolina's swim season runs 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. 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.
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 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. 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. Tier 1 includes beaches that are adjacent to resort areas, public accesses, and sailing camps and are used daily. All ocean beaches are considered Tier 1. Tier 2 beaches are in areas such as 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 those in Tier 3.
Beaches with storm drains that extend to the water's edge are sampled 10 feet from 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. States that deliberately sample near potential sources of pollution, such as storm drains, tend to have higher percent exceedance rates than states that do not. In Dare County, lateral sampling is performed after a storm to determine the extent of the bacteria plume from discharging storm drains. 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. NCDENR samples after storm events, sewage spills, dredge disposal, and floodwater pumping to confirm safe bacteria levels before lifting preemptive advisories. 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 an exceedance or a storm or pollution event.
North Carolina also monitors for Karenia brevis, a marine alga responsible for causing a harmful algal bloom often called a red tide. When 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. If nearshore K. brevis levels present a health concern, beach advisories will be issued, but as yet, such advisories have not been warranted.
How Many Beach Closings and Advisories Were Issued in 2012?
Total closing/advisory days for 21 events lasting six consecutive weeks or less decreased 28% to 91 days in 2012 from 126 days in 2011. For prior years, there were 496 days in 2010, 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 (78 days) and no 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. All closing and advisory days in 2012 were due to monitoring that revealed elevated bacteria levels.
How Does North Carolina Determine When to Warn Visitors About Swimming?
The 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. he public is notified of alerts and advisories through press releases, the NCDENR website, and other avenues. 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 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. 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. 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. However, the NCDENR generally opts to apply Tier 1 standards during those months if temperatures are warm enough for high recreational use.
North Carolina has an elaborate process for determining when to issue a notification, and the process varies according to tier.
- 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 the enterococcus level is between 104 and 500 mpn/100 ml. A second sample is collected immediately when an alert is issued, and if the level in the resample exceeds 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 5 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.
The 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, the NCDENR may issue blanket advisories that cover large regions or all of coastal North Carolina. 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 outfall (NRDC data do not include this type of standing advisory). Otherwise, preemptive rainfall advisories (advisories issued after rain, before monitoring results are available) are not issued because, according to the state, 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, or when dredged material from closed shellfishing waters is placed on ocean beaches.
North Carolina 2012 Monitoring Results and Closing/Advisory Days