Grassland Bypass Project (GBP) Toxicity Program

Phase l

Phase l of the Grassland Bypass Project (GBP) Toxicity Program stretched over the period of October 1, 1996 to September 30, 2001.  The program was initially composed of two parts: Laboratory Toxicity Testing, and in situ Toxicity Testing. However, in 1997, in situ toxicity testing was discontinued.  For 1998, sediment bioassays were conducted in lieu of in situ toxicity testing.  Selenium and sulfate concentrations were measured every other day during seven day tests.

Phase ll

Phase ll of the Grassland Bypass Project Toxicity Program started on October 1, 2001 and will stretch over a period of 8 years.  Tests, sampling procedures and protocols used in Phase l will stay the same for Phase ll with the following changes:  Testing will be done quarterly, however, sampling frequency can be changed depending on the quarterly results; and sulfate concentrations will no longer be measured during the seven day tests.

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A complete description of these tests, the sampling procedures, and protocols can be found in the Grassland Bypass Project Compliance Monitoring Work Plan.

Toxicity Testing Reports

Beginning in 2006, electronic copies of all data reports can be found here.  All reports are subject to approval prior to being posted

Laboratory Toxicity Testing Program

Samples are collected  from the five sites listed below for the Laboratory Toxicity Testing Program. Results are provided in the links below.

• Site B - San Luis Drain (SLD) at footbridge opposite Kesterson Pond 7
• Site C - Mud slough upstream of SLD discharge
• Site D - Mud slough downstream of SLD discharge
• Site F - Salt slough near Highway 165
• Control - Delta Mendota Canal (DMC) at Highway 33

Fathead Minnow (Pimephales promelas) Percent Survival (Phase l  //  Phase ll)
Fathead Minnow (Pimephales promelas) Mean Growth (Phase l  //  Phase ll)
Daphnia magna Percent Survival (Phase l   //  Phase ll)
Daphnia magna Mean Reproduction for Surviving Females (Phase l  //  Phase ll)
Selenastrum capricornutum Cell Counts (Phase l   //  Phase ll)

Total Suspended Solids (TSS)

TSS measurements in mg/L taken for each sample at BES laboratory.

TSS Concentrations (Phase l  //   Phase ll)

Selenium and Sulfate Concentrations

Selenium and sulfate collected at the same time and location as samples described above. For seven day Laboratory Toxicity Testing Program, selenium concentrations were determined from each of the three renewal samples collected on test days 0, 2, and 4. For the in situ Toxicity Program, these data correspond to the first, third, and fifth test day.

Selenium Concentrations (Phase l   //  Phase ll)
Sulfate Concentrations (Phase l)

In Situ Toxicity Program

In situ studies were conducted on a quarterly basis in 1997. These studies consisted of placing four-day old fathead minnow larvae in plexiglass containers directly into the water at stations described below. A detailed description of the protocol used can be found in the GBP Compliance Monitoring Work Plan.

• Site B - Described above
• Site D - Described above
• Site F - Described above
• Control l - Windmill site at the Kesterson National Wildlife Refuge

In situ Toxicity Program Results

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