3.3 Water Resources
Water temperatures near the receiver sites tend to be more uniform throughout the water column due to
turbulent mixing and shallower depths. Nearshore locations are shallower and have slightly higher
temperatures in the range of 57 to 75 F.
Salinity
Historical salinity levels are fairly uniform ranging from approximately 32 to 34 parts per thousand (ppt)
throughout the study area. Salinity levels tend to be homogenous throughout the water column with
differences typically less than 1 ppt from surface (near receiver sites) to bottom waters (borrow sites). The
exception is during winter storms when freshwater runoff reduces surface water salinity, especially at
nearshore locations. Salinity levels in both surface and bottom waters may be slightly higher from April to
August due to upwelling of more dense bottom waters.
Dissolved Oxygen
Historical dissolved oxygen values range from 5.0 to 11.6 mg/L throughout the study area. Surface water
dissolved oxygen at proposed borrow sites SO-5 and SO-7 were 8.3 mg/L and 7.8 mg/L, respectively,
during the June 1999 survey. Bottom water dissolved oxygen at both sites was 8.6 mg/L. Surface and
nearshore waters generally have higher concentrations of dissolved oxygen due to continuous wave action
and atmospheric mixing. A dissolved oxygen level equal to or greater than 5 milligrams per liter (mg/l) has
been recommended as a generalized standard of acceptable water quality for aquatic life. Dissolved
oxygen concentrations are routinely measured off the coast of Encinitas. Average recorded dissolved
oxygen levels at that location are 6 to 10 mg/l.
pH
Historical pH values range from 7.7 to 8.4 throughout the study area. Slightly higher pH values occur
during May through September when water temperatures are warmer. Little variance occurs from surface
to bottom waters.
Turbidity
3.3.3
Turbidity is a result of particles suspended in the water column. Turbidity may result from natural causes,
e.g., plankton concentrations, as well as from sediment particles suspended by waves, river discharge
Regional Beach Sand Project EIR/EA
Page 3.3-3
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