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

        Sites rated as good quality for dissolved oxygen concentrations include:  AC, M42, M35, M23, and M18.  The following sites were rated as fair quality for dissolved oxygen, with the percentage of samples not meeting the standard of 5.0 mg/L shown in parentheses:  LVC (17%), DP (25%), IC (17%), HB (25%), BRR (17%), M61 (25%), and M54 (17%).  Navassa (NAV) was rated as poor quality for dissolved oxygen concentrations due to levels below 5.0mg/L in 33% of all samples.   Dissolved oxygen concentrations are represented graphically for DP, NAV, HB and M61 in Figure 3.4.1.  In summer months, the riverine sampling sites 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 within this subbasin were found to be good quality in terms of chlorophyll a concentrations.  None of the sampled locations exceeded the 40 mg/L North Carolina State Standard on any sample occasion.

        All sites within this subbassin were rated as good quality for fecal coliform bacteria concentrations.  No site exceeded the 200 CFU/100mL NC State Standard for human contact waters.  The NC State Standard for Shellfishing states that geometric mean cannot exceed 14 CFU/100mL and no more than 10% of samples may exceed 43 CFU/100mL.  When considering this subbasin from a shellfishing perspective, the stations in the middle estuary (from river channel marker 35 (M35) and upstream) are poor quality due to concentrations with a geometric mean above 14 CFU/100mL (NC State Standard for Shellfishing).  The lower estuary stations (M23 and downstream) were more suited for shellfishing.  M23, M18 and SPD all maintained fecal coliform bacteria geomeans below 14 CFU/100mL and did not exceed 43 CFU/100mL in more than 10% of samples.  The higher salinities found in the lower estuary significantly increase mortality of fecal coliform bacteria.

        For turbidity, the upper stations within this watershed were evaluated using the North Carolina State Standard for freshwater of 50 NTU.  All stations downstream of NAV were evaluated with the NC State Standard for brackish waters of 25 NTU.  The following stations were good quality for turbidity:  LVC, AC, DP, IC, NAV, M23, M18, and SPD.  The following sites were rated as fair quality for turbidity:  M61, M42, and M35.  The sites that were rated as poor were found in the lower estuary, and rated by the brackish water standard of 25 NTU.  HB and BRR were both poor quality for turbidity, exceeding the standard 33% of the time.  M54 was also rated poor quality, exceeding the standard in 50% of sampled months. 

Figure 3.4.1  Dissolved oxygen concentrations (mg/L) for DP, NAV, HB, and M61 
for the 2003-2003 monitoring period.  The solid line shows the NC State Standard 
of 5.0 mg/L and the dashed line shows the swampwater standard of 4.0 mg/L.  

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