Data Series 233
U.S. GEOLOGICAL SURVEY
Data Series 233
The study consists of two phases: Phase One sampling started in October 1998 and will continue until construction starts for SR 125, when Phase Two sampling will begin. The objectives of Phase One are to determine the occurrence and concentration of selected organic and inorganic compounds in water, air, and bed sediments and to establish baseline conditions for the target analytes before construction of SR 125 begins. The objectives of Phase Two are to continue monitoring for the same chemical constituents, to compare the analytical results with those from Phase One, and to assess the impact of SR 125 on water quality in the SWR. Two types of studies were done: a study using primary samples to determine a common set of compounds and special studies to assess the occurrence of specific chemicals of concern.
Each of the environmental media (water, air, and sediment) in the Sweetwater watershed is being sampled and analyzed for those compounds expected to accumulate in them. The media and compounds that will be sampled throughout the study, the core (primary) data, include the following:
Originally, Phase One incorporated seven water-sampling sites at SWR (sites 1–7, fig. 2), and two at LLR (fig. 3). Regularly scheduled water sampling began at these sites during the first year of the study (water year 1999). Starting with the second year, only three of the seven sites at SWR and one site at LLR were used for sampling.
Phase Two sampling will start when construction of SR 125 begins. Water and air monitoring will continue at the established sites during and after the construction of SR 125. Data from the California Air Resources Board (CARB) Air Toxics monitoring site at Chula Vista will be used to assess the number and concentration of airborne anthropogenic compounds originating from areas upwind of the SR 125 alignment. Phase Two monitoring also will be used to assess the continuing inputs of anthropogenic compounds resulting from the land-use practices in the watershed by comparing compound detections and frequency with data collected in Phase One.
The air-sampling site is located adjacent to SWR, downwind of the proposed SR 125 routes and upwind of SWR along a transect of the predominant wind direction (site denoted by a star symbol on fig. 2). Air samples were not collected at LLR because its foothill location (30 km east of SWR) is considered sufficiently downwind of SR 125 to be minimally affected by any airborne contaminants originating from this highway. The air-sampling site is wired for AC power (120 volts), equipped with telephone modem access, and secured from the general public by a 2-m high chain-link fence.
Surficial bed sediments were not sampled during the time frame covered by this report, but were sampled at the beginning of Phase One, as previously reported by Majewski and others (2002), at each reservoir water-sampling site and at the urban-runoff diversion system ponds. Also, at the beginning of Phase One, a one-time coring of the SWR bed sediments was completed (Majewski and others, 2002). The bed sediments will be resampled at the beginning of Phase Two and again several months before the completion of the study.
During the course of this project, several special studies have been initiated to help the Authority better understand the effects that different operational modes have on water quality. These special studies, which are of limited scope and only conducted at a targeted subset of sampling locations, are expected to provide up-to-date water-quality information on chemicals of current concern. Six special studies were conducted during the 2-year time frame covered by this report (1999–2001). Two of these special studies involved analysis of ground water.
U.S.
Department of the Interior | U.S. Geological Survey
Persistent URL: https://pubs.water.usgs.gov/ds233
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Page Last Modified: March 8, 2007
