The Bradley Creek watershed is of particular current interest as a principal location for Clean Water Trust Fund mitigation activities, including the purchase and renovation of Airlie Gardens by the County.  This creek is one of the most polluted in New Hanover County, particularly by fecal coliform bacteria (Mallin et al. 2000b).  Seven stations were sampled in the past year, both fresh and brackish (Fig. 3.1).

            As with last year, turbidity was not a problem during 2002-2003 (Table 3.1).  The standard of 25 NTU was not exceeded during our brackish water sampling except with a construction-related episode in July 2003 (198 NTU - Table 3.1).  There were only minor problems with low dissolved oxygen (hypoxia), with BC-NB having DO of less than 5.0 mg/L on two occasions and BC-CA having substandard dissolved oxygen conditions on three of 12 sampling occasions (Appendix B). 

Table 3.1  Parameter concentrations at Bradley Creek sampling stations, August 2002-July 2003
(BC-CA from August 2003 – September 2003).  Data as mean (SD) / range, fecal coliform bacteria
as geometric mean / range.
_____________________________________________________________________
Station            Salinity                     Turbidity            Dissolved Oxygen         Fecal coliforms
                            (ppt)                        (NTU)                   (mg/L)                        (CFU/100 mL)
_____________________________________________________________________

BC-76            28.8 (7.0)                    9 (15)                 7.7 (2.2)                           NA
                        9.0-34.2                      2-55                   5.0-11.0    

BC-SB           12.5 (12.8)                25 (55)                 7.4 (1.9)                          NA
                        0.1-31.6                    2-198                   4.9-11.1    

BC-SBU         0.1 (0.0)                    6 (6)                    7.2 (1.4)                           NA
                        0.1-0.1                      2-22                     5.3-9.4       

BC-NB            21.1 (11.6)              10 (9)                   7.1 (2.2)                          NA
                         0.2-32.8                   2-35                    3.9-10.2    

BC-NBU         0.1 (0.0)                   9 (10)                   7.6 (1.1)                           NA
                         0.1-0.2                     3-40                     6.1-9.3       

BC-CR            0.1 (0.0)                  4 (6)                      7.6 (0.8)                          NA
                        0.0-0.1                   0-18                      6.5-8.8       

BC-CA            0.1 (0.0)                  8 (4)                      6.3 (2.1)                       1093
                        0.1-0.2                   3-13                      4.4-10.6                   155-13000
_____________________________________________________________________

Only BC-CA was sampled for fecal coliform concentrations last year, with elevated counts exceeding the State standard of 200 CFU/100 mL occurring during 9 of 11 collections for an 82% exceedence rate (Table 3.1).  We consider that station to have poor water quality in terms of fecal coliform counts (Appendix B).

            Nitrate concentrations were highest at stations BC-CR, BC-SBU (upper south branch) and BC-NBU.  Nitrate increased considerably over the previous year (in some cases more than doubling), possibly as a result of the drought breaking and increased streamflow (and stormwater runoff).   Ammonium was also elevated at BC-CA, and low at other locations.  The highest orthophosphate levels were found at BC-CA, with relatively low orthophosphate levels at the rest of the stations (Table 3.2).  Bradley Creek did not host excessive algal blooms in 2002-2003, except for a few minor blooms at BC-CA (20-32 mg/L, Table 3.2). 

Table 3.2.  Nutrient and chlorophyll a data at Bradley Creek sampling stations, August 2002-July 2003
(BC-CA from August 2003 – September 2003).   Data as mean (SD) / range, nutrients in mg/L, chlorophyll a as mg/L.
_____________________________________________________________________
Station            Nitrate                        Ammonium               Orthophosphate        Chlorophyll a
_____________________________________________________________________

BC-76             0.021 (0.032)            0.026 (0.024)            0.007 (0.007)            1.97 (1.6)
                         0.006-0.121              0.006-0.087              0.001-0.027               0.7-6.4 

BC-SB            0.088 (0.058)            0.036 (0.023)            0.011 (0.013)            3.2 (2.3)
                        0.013-0.212              0.004-0.069              0.002-0.052              0.8-8.4 

BC-SBU          0.186 (0.108)                        NA                 0.009 (0.011)            2.5 (2.9)
                         0.044-0.464                                                 0.001-0.044              0.2-10.2 

BC-NB            0.029 (0.033)            0.032 (0.031)            0.009 (0.010)            3.9 (5.4)
                         0.005-0.123              0.006-0.105              0.001-0.036              0.7-20.5 

BC-NBU        0.116 (0.047)                        NA                   0.004 (0.007)            1.5 (2.7)
                        0.069-0.250                                                  0.001-0.023               0.1-9.2 

BC-CR           0.270 (0.060)                        NA                   0.005 (0.007)            1.8 (2.9)
                        0.150-0.372                                                  0.001-0.027               0.2-9.0 

BC-CA           0.090 (0.056)            0.125 (0.073)            0.021 (0.012)            10.6 (9.6)
                        0.016-0.170              0.020-0.270              0.0102-0.045             1.7-32.0
_____________________________________________________________________