Draft EIS_072312.pdf - Middle Fork American River Project ...

20120723-4002 FERC PDF (Unofficial) 07/23/2012
Figure 3.3.2-5. Ralston afterbay water temperature and dissolved oxygen profiles at site
RA1 for all years (2005–2008) and sampling months (June–October)
(Source: PCWA, 2011a).
• In situ sampling conducted in spring 2007 in Duncan Creek just upstream of its
confluence with the Middle Fork American River and Middle Fork American
River just upstream and downstream of the confluence of Duncan Creek
showed anomalously low DO of 6.3 mg/L and 6.2 and 6.3 mg/L, respectively.
Samples collected farther upstream and downstream of these sampling sites
showed DO above the basin plan criteria minimum level of 7.0 mg/L. PCWA
believed the values were incorrect and attributed them to either instrument
malfunction or sampling error. All other sampling locations had DO values
between 7.1 and 11.7 during spring 2007 and fall 2007 sampling events.
• Sampling of seepage water through French Meadows dam (sampled from
leakage channels) had high concentrations of manganese (4.04, 3.61, and 3.86
mg/L) and iron (20.4, 16.0, and 19.4 mg/L) and low pH (5.3, 5.6, and 5.5) and
DO (1.1, 5.2, and 2.9 mg/L). All of these values are not within basin plan
water quality objectives. Samples collected 800 feet downstream showed
concentrations that were within the ranges of relevant water quality objectives
due to dilution by instream flow releases and accretions downstream from the
leakage channels.
• One-time fecal coliform sampling conducted at North Fork Long Canyon
Creek below the diversion (RM 2.9) exceeded the basin plan water quality
objective for fecal coliform during the fall 2007 sampling event (300/100 mL).
No follow-up sampling was conducted.
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