appendix b final 2008 biological surveys of los angeles and long ...

2.0 Water Quality
influenced by a combination of shallow water (4 m maximum depth), solar heating, and reduced
mixing with inner and outer harbor waters (see station location in Figure 2.2-1).
The Basin Plan does not specify water quality objectives for temperature. (Limitations on the
temperatures of thermal discharges are covered under the Thermal Plan.)
2.3.2 Salinity
Salinity values for surface, mid-depth, and bottom waters ranged from 33.0 to 33.6 parts per
thousand (ppt) or practical salinity unit (PSU), 33.4 to 33.6 ppt, and 33.3 to 33.5 ppt,
respectively (Table 2.3-2). Salinity typically increased with water depth, although the range of
salinities at individual stations was relatively small (e.g., less than 0.5 ppt). The vertical salinity
profiles for individual stations did not show any rapid changes in salinity with depth (i.e.,
pycnocline) or other obvious stratification as would be expected in these relatively shallow
depths.
The Basin Plan does not specify water quality objectives for salinity.
2.3.3 Density
Density values for surface, mid-depth, and bottom waters ranged from 22.5 to 23.7
kilograms/cubic-meter (kg/m 3 ), 23.6 to 24.4 kg/m 3 and 23.4 to 24.8 kg/m 3 , respectively (Table
2.3-2). Density typically increased with water depth although the range of densities at individual
stations was relatively small (e.g., approximately 0.5 kg/m 3 ), consistent with the salinity data
which is a key component of density. Profiles for individual stations did not exhibit strong
density stratification or other evidence of density layering.
The Basin Plan does not specify water quality objectives for density.
2.3.4 Acidity/Alkalinity (pH)
Average pH values for surface, mid-depth and bottom waters at individual stations were 7.37,
7.26 and 7.19 respectively (Table 2.3-2). Changes with depth in pH at individual stations
typically were minimal, varying by 0.2 pH unit or less. However, differences between surface
and bottom depths at some shallow and deep stations (e.g., 5 m and 20 m, respectively) were
on the order of 0.2 pH units. There were no apparent gradients or consistent spatial patterns in
pH conditions.
The Basin Plan established an acceptable range for pH in bays or estuaries of 6.5 to 8.5 with a
change in tolerance level of no more than 0.2 due to discharges. All pH values measured
during the July 2008 survey were within this range.
2.3.5 Dissolved Oxygen
DO concentrations ranged from 7.58 to 10.7 milligrams per liter (mg/L), 6.24 to 8.57 mg/L and
4.38 to 8.57 mg/L for surface, middle, and bottom depth waters, respectively (Table 2.3-2). DO
concentrations were higher near the surface, decreasing with depth, with the lowest
concentrations in the near-bottom waters. DO measurements at most stations indicated a well
oxygenated water column (i.e., DO concentration above 5 mg/L). All surface water and middepth
DO concentrations were above the 5 mg/L (Table 2.3-1). Near-bottom DO concentrations
fell below 5 mg/L at three locations (LA8, 4.38 mg/L; LB1, 4.58 mg/L; and LB3, 4.94 mg/L).
The Basin Plan specifies that the mean annual DO concentration of waters shall be 7 mg/L or
greater with no event less that 5 mg/L, except when natural conditions cause lesser
concentrations. The Basin Plan also specifies that the mean annual DO concentration in the
2008 Biological Surveys of Los Angeles and Long Beach Harbors 2–3
April 2010