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

20120723-4002 FERC PDF (Unofficial) 07/23/2012
access road to the new spillway gates; and (5) modify the instream flow outlet to
maintain proposed increased instream flows.
2.2.1.4 North and South Fork Long Canyon Diversion Modifications
PCWA proposes to modify the North Fork Long Canyon and South Fork Long
Canyon diversions as follows: (1) construct a new wedge-wire screen intakes on the
upstream side of the existing ogee section of the diversion weirs; (2) construct new
concrete chambers to connecting the intake channels with the existing intakes to the
existing buried discharges that convey the diverted flow to the top of the shafts that drop
into the Hell Hole-Middle Fork tunnel; (3) increase the height of the weir abutments by
2.7 feet at the North Fork diversion and 3.5 feet at the South Fork diversion for adequate
freeboard during floods; (4) install a remote controlled slide gate to control tunnel inflow;
(5) modify the existing low-level outlets through the dams for dewatering the
impoundments and for discharging instream flows downstream of the weirs and
decommission of the existing instream flow release outlets at the North Fork diversion;
(6) modify existing instream flow outlets to maintain increased instream flows, facilitate
bedload transport, and establish first priority for water flowing into the wedge-wire
intake; (7) implement security improvements; (8) install new communications uplinks;
and (9) install a self-contained solar/thermal electric power supply system.
2.2.1.5 Middle Fork Interbay Dam Outlet Works Modification
PCWA proposes to modify the existing instream flow outlet at the dam to
maintain the proposed increased instream flows and facilitate bedload transport.
2.2.1.6 Proposed Flow Measurement Equipment
PCWA proposes installing new flow measurement equipment and adding two
existing stream gages (Rubicon River above Ralston powerhouse and Rubicon River
above Ellicott Bridge) as part of a new license, including the following:
• a new gage on the Duncan Creek diversion tunnel;
• new flow measurement equipment on the Middle Fork American River at the
outlet of the French Meadows dam instream flow maintenance pipe and the
low level outlet pipe;
• new flow measurement equipment on the Rubicon River at the outlet of the
Hell Hole dam instream flow maintenance pipe and low level outlet pipe;
• a new gage on the Rubicon River at the Hell Hole spillway;
• a new gage on the North Fork Long Canyon Creek downstream of the
diversion dam;
• a new gage on the South Fork Long Canyon Creek downstream of the
diversion dam;
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