Operational Plan for the Restoration of Diadromous Fishes to the ...

channel would carry almost 1000 cfs when the river flows are approximately 8000 cfs. At
summer low flow, almost all of the river discharge would go into the bypass.)
3. Low flow channel – Relative to 2 above, passage during critically low flows will need to be
addressed with a low flow channel.
4. Water control structure – It is anticipated that the nature-like fish bypass will include a
water management structure to maintain flows throughout the migratory run period.
Outline of information to be requested in the RFP
Narrative:
Description of bypass fish channels that have been designed and/or constructed elsewhere
in the world: brief discussion of concepts of fish bypasses; examples from elsewhere
Description of Howland site: location - relationship to existing infrastructure (dam,
powerhouse, roads & bridges, etc.); current/former ownership and uses of land, including
any restrictions contained in deeds or regulatory orders; soil borings along channel (likely
materials to be excavated, contamination); topography using one-foot contours
Hydrology and hydraulic considerations: (reference previous HEC-RAS modeling by Milone
and MacBroom) (supplement with tables to show data) river flows during passage season;
high and low flow issues; range of operating flows (up to 9,000 cfs); relationship between
bypass and river flows; range of water depths/widths/velocities in bypass during low, mean,
and high flow events, including conditions when high flows in the Penobscot drown out the
entrance to the bypass channel; relate hydraulic conditions to swimming abilities (design
criteria) of target species; flooding and ice jams; results of additional modeling (computer
derived), including analysis of flow field and velocity vectors below spillway near bypass
entrance; need for control gate in upper end of bypass; assess the need for, and potential
methods to enhance attraction flow under high flow conditions using powerhouse, flood
gates, or other existing structures; future impoundment levels, head pond and tailwater
elevations; hydraulic conditions at spillway and immediately below dam during downstream
migration periods (to inform on whether downstream migrating fish will travel over the dam
without injury or mortality, or if additional structures or modifications may be needed for
downstream passage at the dam).
Bypass design: layout (length, slope – not to exceed 3 % , width, depth, low flow channel,
rock weirs/chevrons/resting pools, rip-rap side slopes, entrance and exit relative to existing
spillway, gates and attraction flows); use of surrounding land; public safety issues
Construction: construction equipment access and road grading; removal of existing turbines,
flashboards, etc.; use of powerhouse and adjacent gates for attraction flow purposes;
bypass materials and construction methods (earthen cuts and fills, boulders for weirs and
rip-rap); need for modifying ledge material below bypass entrance to enhance fish
movement; erosion/sedimentation controls; disposal of excavated materials; removal of
temporary access and revegetation of banks areas; schedule (start, finish, work during
winter, expected milestones); mitigation for affected infrastructure (existing storm drains,
boat ramp, etc.); duration of construction; costs
Also information (including itemized cost estimates) for:
- mobilization and demobilization
- installation and removal or restoration of construction access roads
PRFP Page 287