Characterization of water-quality and bed-sediment conditions in Currituck Sound, North Carolina, prior to the Mid-Currituck Bridge construction, 2011–15

Abstract

The North Carolina Turnpike Authority, a division of the North Carolina Department of Transportation, is planning to make transportation improvements in the Currituck Sound area by constructing a two-lane bridge from U.S. Highway 158 just south of Coinjock, North Carolina, to State Highway 12 on the Outer Banks just south of Corolla, North Carolina. The results of the Final Environmental Impact Study associated with the bridge and existing roadway improvements indicated potential water-quality and habitat impacts to Currituck Sound related to stormwater runoff, altered light levels, introduction of piles as hard substrate, and localized turbidity and siltation during construction. The primary objective of this initial study phase was to establish baseline water-quality conditions and bed-sediment chemistry of Currituck Sound in the vicinity of the planned alignment of the Mid-Currituck Bridge. These data will be used to evaluate the impacts associated with the bridge construction and bridge deck stormwater runoff. Between 2011 and 2015, discrete water-quality samples were collected monthly and after selected storm events from five locations in Currituck Sound. The sampling locations were distributed along the proposed alignment of the Mid-Currituck Bridge. Water samples were analyzed for physical parameters and water-quality constituents associated with bridge deck stormwater runoff and important in identifying impaired waters designated as "SC" (saltwater-aquatic life propagation/ protection and secondary recreation) under North Carolina's water-quality classifications. Bed-sediment chemistry was also measured three times during the study at the five sampling locations. Continuous water-level and wind speed and direction data in Currituck Sound were also collected by the U.S. Geological Survey during the study period. For the water samples, measured concentrations were greater than water-quality thresholds on 52 occasions. In addition, there were 190 occurrences of censored results having a reporting level higher than specific thresholds. All 52 occurrences of concentrations greater than water-quality thresholds were confined to seven different physical properties or constituents, namely pH (25), turbidity (8), total recoverable chromium (6), total recoverable copper (6), dissolved copper (3), total recoverable mercury (2), and total recoverable nickel (2). Concentrations of 17 other constituents were never measured to be greater than their established water-quality thresholds during the study. The focus of the water-quality characterization was on concentrations of constituents identified as parameters of concern in a 2011 collaborative U.S. Geological Survey/North Carolina Department of Transportation study that characterized bridge deck stormwater runoff across North Carolina. The occurrence and distribution of parameters of concern identified in the 2011 study, including pH, nutrients, total recoverable and dissolved metals, and polycyclic aromatic hydrocarbons, and some additional pertinent physical propert...

Impacts of Hurricane Winds and Precipitation on Hydrodynamics in a Back‐Barrier Estuary

“…CS, in the northernmost segment of the larger APES system (Figure 2), is an ∼58‐km‐long and 8‐km‐wide microtidal estuary with averaged depth of 2.5 m (Fine, 2008; Moran et al., 2015). Characterized by muddy to sandy sediments, CS is typical of back‐barrier estuaries along the east coast of North America (Wagner et al., 2016). CS is protected from the ocean by the northern Outer Banks, and does not have any inlets connecting it directly to the ocean.…”

“…Previous studies in this area have highlighted that the high variability in wind speed and direction during storm events can have dramatic effects on waves (Mulligan et al., 2015b), water levels (Clunies et al., 2017), productivity (Corbett, 2010; Giffin & Corbett, 2003), and morphology (Mulligan et al., 2015a; Paerl et al., 2006). Flooding in this low‐lying area frequently occurs during storm events (Bales, 2003; Peng et al., 2004; Wagner et al., 2016), presenting a risk that is likely growing in conjunction with increased urban development (Miselis et al., 2016), sea level rise (Field et al., 2014), storm frequency (Knutson et al., 2010), and intensity (Wahl et al., 2015). CS, in the northernmost segment of the larger APES system (Figure 2), is an ∼58‐km‐long and 8‐km‐wide microtidal estuary with averaged depth of 2.5 m (Fine, 2008; Moran et al., 2015).…”

“…Previous studies in this area have highlighted that the high variability in wind speed and direction during storm events can have dramatic effects on waves (Mulligan et al, 2015b), water levels (Clunies et al, 2017), productivity (Corbett, 2010;Giffin & Corbett, 2003), and morphology (Mulligan et al, 2015a;Paerl et al, 2006). Flooding in this low-lying area frequently occurs during storm events (Bales, 2003;Peng et al, 2004;Wagner et al, 2016), presenting a risk that is likely Figure 1. Map of the model domain including bathymetry, model boundaries, validation sites, selected meteorological stations, and RAP forecast tracks for Tropical Storm Hermine and Hurricane Matthew.…”