3.4  Cape Fear River Subbasin 03-06-17
Includes Town Creek, Smith Creek and the Brunswick River
Municipalities: City of Wilmington and Town of Southport

 
LCFRP Station Codes (DWQ #):  LVC (74), AC (61), DP (92), IC (71), NAV (72),
HB (73), BRR (75), M61 (86), M54 (87), M42 (88), M35 (89), M23 (90), M18 (91),
SPD (93)
DWQ/UNCW ambient monitoring site(s):  NAV, M61, M54
Waterbody:  Lower Cape Fear River and Estuary
Location:  Lower Cape Fear River including Livingston Creek, downstream to 
estuarine area off Town of Southport
Lat/Lon:  N 34.35180    W 78.20128   (LVC)
                N  33.91708    W  78.03717   (SPD)

Use Support Ratings, from NCDENR, DWQ (Cape Fear River Basinwide Water Quality Plan, July 2000): 
Freshwater Streams
Fully Supporting:                   251.5 mi.
Partially Supporting:             3.8 mi.
Not Supporting:                     0.0 mi.
Not Rated:                              65.5 mi.

Estuarine Waters
Fully Supporting:                   16,314 ac.
Partially Supporting:             7,211 ac.
Not Supporting:                     0.0 ac.
Not Rated:                              925 ac.

        This subbasin is located in the outer coastal plain and in estuarine regions of the basin.  Significant dischargers in this subbasin are the City of Wilmington and the Town of Southport.  There are 49 permitted dischargers in the subbasin; half of which discharge directly into the Cape Fear River.  The largest dischargers are International Paper, Wilmington North Side WWTP and Wilmington South Side WWTP.  (NCDENR, DWQ Cape Fear River Basinwide Water Quality Plan, July 2000)

        Portions of Livingston Creek, the Cape Fear River and estuarine areas were identified as impaired in the 1996 Basinwide Water Quality Plan (NCDENR, DWQ).  Currently Livingston Creek is listed as fully supporting (FS) and is no longer on the 303(d) list of impaired waters.  The Cape Fear River is currently partially supporting (PS), because of an impaired biological community.  The International Paper Board discharge and nonpoint source pollution are possible causes of impairment, and this segment of the river is on the state’s year 2000 303(d) list.  The Cape Fear River Estuary (5000 acres) is partially supporting (PS) and is on the state’s year 2000 303(d) list.  The cumulative impacts from WWTP discharges in the subbasin as well as nonpoint source pollution are suspected to be the significant contributors to the impairment.  Swamp water drainage may also be a source of low dissolved oxygen (DO) waters feeding into the estuary.  Possible sources of nonpoint source pollution include marinas, canal systems, and septic systems.  (NCDENR, DWQ Cape Fear River Basinwide Water Quality Plan, July 2000)

        Approximately 45% of the waters in this subbasin are impaired by nonpoint source pollution.  All the waters of the subbasin are affected by nonpoint sources.  The 303(d) list approach will be to develop a TMDL for this segment of the Cape Fear River because of low DO levels.  Because of the nature of the river/estuary system in this portion of the basin, addressing water quality issues must not be limited to problems in impaired segments alone.  Because this segment of the river and estuary are impaired, issuance of new and expanding discharges that would further increase the load of oxygen-consuming waste into these waters will be considered on a case by case basis.    (NCDENR, DWQ, Cape Fear River Basinwide Water Quality Plan, July 2000)

UNC-Wilmington – Center for Marine Science, LCFRP
Station Names:  LVC, AC, DP, IC, NAV, HB, BRR, M61, M54, M42, M35, M23, M18, SPD
Data collection:  some stations since 1995, all sampled since 1998
Sampling relevance:  below point source dischargers, including City of Wilmington,
and nonpoint source pollution

          AC - representative of riverine system
          stations, low salinity, fairly narrow channel

 
       HB - riverine station, upstream of Wilmington, shows 
           change of landscape from upland forested areas 
                        to more open, wider river channel  

 
                 M35 - representative of the estuarine
           stations, wider channel, strong tidal influence

        Most sites within this subbasin were fully supporting (FS) for dissolved oxygen.  Exceptions were Indian Creek (IC), which was partially supporting (PS) for dissolved oxygen.  The state standard of 5.0 mg/L was not met 25% of the time.  Also Navassa (NAV) had low dissolved oxygen in several summer samples.  It was rated by UNCW as non supporting (NS) due to dissolved oxygen levels, which were lower than 5.0 mg/L in 33% of the monthly sampling trips (Figure 3.4.1).  In summer months, all of the riverine stations in this subbasin are monitored weekly, and the estuary stations are monitored biweekly.  Low dissolved oxygen levels are a concern during summer months because there is generally less rain, more transpiration, lower flow levels, and the warmer waters hold less dissolved oxygen than colder waters.  The summer values are represented graphically in Figure 3.4.2.

        All sites were found to be fully supporting (FS) for chlorophyll a concentrations.  No samples exceeded the North Carolina State Standard for chlorophyll a of 40 mg/L. 

        Most sites within the subbasin were found to be fully supporting (FS) for fecal coliform bacteria concentrations, when measured by the North Carolina State Standard for human contact of 200 CFU/100 mL.  The only exception was Horseshoe Bend (HB), which was rated as partially supporting (PS), with samples exceeding the standard 25% of the time.  The North Carolina State Standard for fecal coliform bacteria for shellfishing waters is no more than 14 CFU/100 mL.  When looking at this subbasin from a shellfishing perspective, the middle estuary stations (from river channel marker 42 (M42) and upstream) were non supporting (NS) due to high fecal coliform bacteria concentrations.  The lower estuary stations (from river channel marker 35 (M35) and downstream) were rated as fully supporting (FS) for shellfishing.  The higher salinities found in the lower estuary significantly increase mortality of fecal coliform bacteria. 

        Most sites within this subbasin were found to be fully supporting (FS) for turbidity, rarely exceeding the North Carolina State Standard for brackish waters of 25 NTU.  The exceptions were the Brunswick River (BRR) site, and river channel marker 54 (M54) site, both of which were found to be partially supporting (PS).  These two sites had turbidity levels that exceeded the state standard 17% of the time, with means of 16 NTU and 15 NTU respectively. 

Figure 3.4.1  Dissolved oxygen concentrations (mg/L) are shown for river and estuary
stations DP, IC, NAV, M61.  The line shows the NC State Standard of 5.0 mg/L, and
the dashed line shows the NC State Standard for swampwater of 4.0 mg/L. 

Figure 3.4.2  Dissolved oxygen concentrations (mg/L) in summer months, weekly
sampling of DP, IC, and NAV; and biweekly sampling of  M61.  The line shows the
NC State Standard of 5.0 mg/L and the dashed line shows the NC State Standard
for swampwater of 4.0 mg/L.