REMOVAL OF SAVAGE RAPIDS DIVERSION DAM – PART ONE
Richard D. Benik1
ABSTRACT
Savage Rapids Diversion Dam is a combination concrete gravity and multiple-arch
diversion facility located on the Rogue River, in southwestern Oregon. The facility
consists of a pumping plant, canals, an overflow dam, and fish ladders. Originally
constructed in 1921-22 by private developers, the facility has been diverting flows for
irrigation to both sides of the river ever since. Species of anadromous fish are present in
the Rogue River year round, sometimes in very large numbers. Despite having a fish
ladder on each abutment, the dam is considered to be a major impediment to fish
migration. The recommended least-cost alternative to improve fish passage and maintain
irrigation diversions is to construct a new diversion facility and remove a portion of the
existing dam. The removal of the dam will restore fish passage and river navigation to
natural conditions. Dam removal is currently scheduled for 2009.
INTRODUCTION
Savage Rapids Diversion Dam, also known as Savage Rapids Dam, is located in
southwestern Oregon on the Rogue River at river mile (RM) 107.6 (107.6 miles upstream
from the Pacific Ocean); and about 5 miles upstream from the town of Grants Pass. The
facility is owned, operated, and maintained by the Grants Pass Irrigation District (GPID)
and is their primary irrigation diversion facility. The purpose of the dam is to seasonally
raise the surface of the Rogue River by an additional 11 feet to provide a sufficient
reservoir head to efficiently operate a gravity canal headworks and a hydraulicallypowered pumping plant which provides water to approximately 7,000 acres of irrigated
land on both sides of the river. The dam was originally constructed in 1921-22 by private
developers and has diverted river flows for irrigation since then. Irrigation season
typically is from mid-May to mid-October.
Diversion for irrigation using the dam and reservoir begins in the spring with stoplogs
placed across the overflow portion of the dam raising the water surface of the upstream
reservoir up to an additional 11 feet of head. This additional head enables gravity
releases through the fish ladder on the right abutment, the upper portion of the fish ladder
on the left abutment, the gravity canal, and operation of the direct-connected hydraulic
turbine-driven pumps that supply irrigation water to the canals located at higher
elevations on each abutment. At the end of irrigation season in the fall, most of the
stoplogs are removed to accommodate winter floods over the overflow portion of the
dam. During the non-irrigation season, fish passage occurs through the lower portion of
the fish ladder on the left abutment while the pumping plant, the fish ladder on the right
abutment, and the gravity canal headworks are shut down.
1
Civil Engineer, Bureau of Reclamation, PO Box 25007, Denver, Colorado 80225, rbenik@do.usbr.gov
Species of anadromous fish are present in the Rogue River, sometimes in very large
numbers. Steelheads (trout) are present in the river year round. Chinook and Coho
(salmon) are present in the non-winter months. In 1997 the National Marine Fisheries
Service (now NOAA Fisheries) listed the Southern Oregon-Northern California Coho
salmon as threatened under the Endangered Species Act. Savage Rapids Diversion Dam
is considered to be a major impediment to fish migration in the Rogue River.
Fish passage and screening at Savage Rapids Diversion Dam have been a concern since
the original construction of the dam. A fish ladder was constructed on the right abutment
at the time the dam was built (north fish ladder). A second fish ladder on the left
abutment was added in 1934 (south fish ladder). The fish ladders at the dam are outdated
and do not meet current criteria of the National Oceanic and Atmospheric Administration
(NOAA) Fisheries. Fish passage improvements made in the late 1970s helped reduce
losses, but fish passage problems continued. During high flows, fish tend to jump out of
the fish ladders and become stranded on the rocks below. Water overtopping the dam,
especially during high flows, distracts the adult fish from locating the attraction flows at
the fish ladder entrances. Early attempts to provide fish screening of the pumped
irrigation diversions were unsuccessful. Irrigation diversions remained essentially
unscreened until 1958 when fish screening facilities were included as part of the pumping
plant intake structure modification. However, these fish screens do not meet current
criteria of the NOAA Fisheries (the openings in the screens are too large, there are no
sweeping velocities, and the approach velocities are excessive). The fish screens were
replaced in kind in the late 1970s.
The recommended least-cost alternative to improve fish passage and maintain irrigation
diversions is to construct a new diversion facility and remove a portion of the existing
dam. Other alternatives considered included completely removing the dam, rehabilitating
the existing pumping plant, and locating new pumping plants on either side of the river
both upstream and downstream of the dam. The proposed dam removal will restore fish
passage and river navigation to natural conditions. The new diversion facility includes a
new pumping plant on the downstream left abutment and a new pipe support bridge to
fulfill irrigation demands on both sides of the river. The pipe support bridge was
preferred by GPID, as opposed to a buried pipe across the river channel, for ease of
access and maintenance purposes. Construction of the new pumping plant and bridge
began in 2006. The new diversion facility is scheduled to become operational in time for
the 2009 irrigation season. The existing dam and pumping plant continue to be used until
the new diversion facility is completed. The dam will not be removed until the new
diversion facility is operational in 2009.
DAM AND APPURTENANCES
Savage Rapids Diversion Dam is a combination reinforced concrete gravity and multiplearch diversion facility. The facility consists of the north fish ladder and pumping plant on
the right abutment, an overflow portion or spillway across the river channel, and the
headworks to the gravity canal (South Main Canal) and south fish ladder on the left
abutment. The existing pumping plant uses hydraulically-driven pumps to supply water
to the Tokay and Evans Canals on the right side of the river and to the Highline and
Savage Canals on the left side of the river via a 42-inch diameter pipe through the dam.
The dam was rehabilitated in 1953-54 when metal stoplogs were installed to replace the
original crest gates across the overflow portion of the dam, and two radial gates were
installed to serve as the river outlet works. In 1957-58 a new pumping plant intake
structure with fish screens was constructed.
The dam has a structural height of 33 feet between the foundation and the concrete crest
of the overflow portion. An additional 11 feet is attained during the irrigation season
through the addition of stoplogs on top of the concrete crest. The dam has a hydraulic
height of 30 feet between the original river channel and the crest of the dam. The dam
has an overall length of 465 feet which includes the entrance to the north fish ladder and
pumping plant on the right abutment, the overflow portion of the dam, and the headworks
to the gravity canal and south fish ladder on the left abutment.
The overflow portion of the dam is 394 feet long between the gravity canal headworks
and the pumping plant, and is divided into 16 bays. The bays are separated by piers or
buttresses. Steel stoplogs are inserted between the piers in the 16 bays on top of the
overflow portion of the dam to raise the upstream river surface. The bays are numbered
sequentially from 1 through 16 from right to left, starting at the pumping plant on the
right side of the dam. Bays 1 through 7 are located within the deepest portion of the river
channel and are supported by the multiple-arch portion of the dam, each bay supported by
one arch. The maximum base width of the multiple-arch portion of the dam, including an
approximately 25-foot-wide downstream concrete apron, is approximately 85 feet. Bays
8 through 16 are supported by the gravity portion of the dam, and the maximum base
width of the gravity section is approximately 30 feet. Bays 1 through 6 are underlain by a
foundation of cemented river gravels, while bays 7 through 16 are founded on bedrock.
The piers between the bays are numbered sequentially from 1 through 17 from right to
left, with pier 1 as part of the pumping plant wall and pier 17 as part of the gravity canal
headworks. The 2-foot-wide piers are located on 25-foot centers. The river outlet works
radial gates are located in bays 10 and 11.
A gallery through the dam exists between the pumping plant and the radial gates. The
gallery consists of a walkway through the interior of bays 1 through 7, and continues as a
narrow gallery through bays 8 and 9 to the radial gates in bays 10 and 11. Bays 1 through
7 communicate with the downstream tailwater through openings near the bottom of the
arch sections. A 42-inch diameter pipe passes through the gallery, providing irrigation
releases from the pumping plant on the right abutment to the Highline and Savage Canals
on the left side of the river.
An 18-inch thick concrete apron extends from the downstream toe of the dam to 50 feet
downstream from the axis of the dam, along bays 1 through 5 and partially bay 6. The
apron was placed on cemented gravels and has a 4-foot deep cutoff at the downstream
end. There also is a 6-inch thick concrete apron in the pumping plant tailrace area.
Erosion downstream of these aprons has been an ongoing concern. By 1952, scour had
formed a large pit stretching approximately 70 feet downstream from the apron with a
maximum depth of about 12 feet. During the 1953-54 modification of the dam, the scour
damage was repaired with grout, concrete and rockfill. Recent surveys of this area
indicate that a 12 to 13 foot deep scour hole has re-developed.
River Outlet Works
The original dam did not include an outlet works. During the 1953-1954 rehabilitation,
bays 10 and 11 were completely removed, the foundation was excavated, and the bays
were rebuilt to house two top-seal radial gates. A diversion channel upstream and
downstream of the new radial gates also was excavated. These gates now serve as the
river outlet works for the dam and are used to lower the reservoir for installation and
removal of the stoplogs. The gates are normally in the closed position.
Stoplogs and Cableway
Originally, each of the bays in the overflow portion of the dam had a timber-faced radial
gate to regulate the upstream water surface elevation. Over the years, the gates
experienced problems with damage from debris impact and vibrations during high
overflows. By 1953, only four of the 16 radial gates were operable. During the 1953-54
rehabilitation of the dam, these radial gates were removed, as well as the top portion of
every odd-numbered pier, and a removable stoplog guide and supporting strut anchor
were provided for each shortened pier. Stoplog guides also were permanently attached to
the even-numbered piers. Steel stoplogs were fabricated for each bay, and when installed
in their guides, raise the reservoir behind the dam 11 feet.
The stoplogs are removed and installed using an overhead motorized steel cableway and
hoist that was added as part of the 1953 rehabilitation of the dam. The cableway spans
580 feet between the structural-steel head and tail “A” frame towers located on the right
and left abutments, respectively.
Gravity Canal (South Main Canal)
With the stoplogs in place and the reservoir raised 11 feet, water can be diverted by
gravity into the South Main Canal through the gravity canal headworks. The gravity
canal headworks also provide water and passage to the upper portion of the south fish
ladder. The headworks consists of two hand-operated slide gates, a wasteway into the
upper resting pool of the south fish ladder, a fish screen structure, the entrance to the
south fish ladder, and the original fish screen structure at the entrance to the earth-lined
South Main Canal. Reservoir diversions into the South Main Canal entrance channel are
controlled by the two slide gates and typically are 50 ft3/s to the South Main Canal and
approximately 20 ft3/s to the south fish ladder.
The entrance to the South Main Canal originally contained a water-driven paddle wheel
that operated two rotating fish screen drums, separated by a concrete pier, that prevented
migrating fish from entering the canal. The paddle wheel and fish screen drums were
removed and replaced in the spring of 1998 with flat-plate bar steel fish screens. The
1998 fish screen structure consists of six fish screens, approximately 4 feet high by 12
feet long, in six steel frames. A brush, driven by a motorized traversing mechanism,
periodically cleans these fish screens.
EXISTING PUMPING PLANT INTAKE STRUCTURE
The pumping plant concrete intake structure (also known as the fish screen structure),
located at the upstream end of the pumping plant, was modified and extended
approximately 42 feet upstream from the original structure during the 1957-58
rehabilitation. The pumping plant intake structure contains trashracks, bulkhead gates
and slots, traveling water screens, a fishport bypass system, curtain gates, sluice gates,
and a debris boom. During operations, approximately 800 ft3/s are diverted through the
pumping plant intake structure which leads to the two hydraucone turbines and three
pumps located within the pumping plant. Water not pumped into the canals returns to the
river through the tailrace downstream of the pumping plant.
Trashracks and Bulkhead Gates
Trashracks are located at the sloping upstream end of the intake structure. Bulkhead
gates are used to dewater either or both water passages of the intake structure for
inspection and maintenance, and during the non-irrigation seasons.
Traveling Water Screens
Two electrically-powered traveling water screens (fish screens), each 10 feet wide and 32
feet high, are located downstream of the bulkhead gate slots and consist of wire fabric
screens. The traveling water screens were installed in 1958. The purpose of the traveling
water screens is to prevent small fish (fingerlings) from entering the waterways leading to
the turbines, pumps, and canals. The water screens are continuously rotated by two
electric motors at an approximate rate of 10 feet per minute. The screens consist of 4.5
meshes with No. 16 gage carbon steel wires, double crimped and hot-dipped galvanized
after weaving. High pressure spray nozzles continuously clean the screens with wash
water. The 4.5 mesh means that there are 4.5 wires per inch of opening in both
directions. Using the No. 16 gage wire (0.0625 inch diameter) the width of each opening
in the screen works out to be 0.15972 inches in both directions. This is equal to an open
area of 51.7 percent. The latest criteria requires the screen openings not to exceed 3/32
(0.0938) inches in the narrow direction for woven wire screening. A minimum open area
of 27 percent in the screen material is also required.
Fish Port Bypass System
A fish escape or port bypass system, consisting of a number of small inlets, is located in
the water passages of the intake structure between the trashracks and the traveling water
screens, immediately downstream of the bulkhead gate slots. There are nine small
vertically spaced inlets, or fish ports, on each side of each water passage (36 total
although some of the lower fish ports have been sealed to increase entrance velocity and
fish attraction to the other ports). Each fish port is 6 inches wide and 9 inches high. The
fish ports are illuminated from above to provide attraction to fish at night. The fish port
bypass system prevents small fish from being trapped between the trashracks and the
traveling water screens, or from migrating downstream and entering the turbines.
Instead, fish enter the small inlets, travel through passages in the concrete structure and
into a 24-inch diameter steel pipe. The steel pipe discharges into the river downstream of
the existing pumping plant. The elevation of the discharge end of this pipe was originally
adjustable by a cable and a hand-winch assembly located on the pumping plant deck.
Discharge from this pipe also serves as an attractant to the north fish ladder.
Curtain Gates
A wooden curtain gate is located in each water passage between the traveling water
screen and the inlet to the hydraucone turbine. The curtain gates are used to regulate the
flow to the turbines. At the beginning of the irrigation season, the curtain gates are rolled
up to the desired height to permit flow into the turbines and flumes.
Sluice Gates
Four slide gates are mounted on the original upstream face of the pumping plant and were
used for sluicing reservoir sediments. These sluice gates discharge into conduits beneath
the existing pumping plant turbines and pump units. Opening the sluice gates has
reportedly caused a high mortality rate of migrating fish through the open gates, as well
as put a lot of sediments into the river downstream. The sluice gates are no longer used
and are currently buried in sediments in the closed position.
Debris Boom
A debris boom is located in the reservoir upstream of the pumping plant intake structure
during the irrigation season. The debris boom is used to prevent floating trash material
from entering the pumping plant intake structure. The debris boom consists of 55-gallon
metal barrels with a plywood deck platform attached to the top and protective wooden
trash deflector panels attached to the upstream side. The trash deflector panels extend
below the water surface. Debris that collects against the wooden panels is manually
raked loose by operating personnel and the debris is swept away by the river overtopping
the dam. The debris boom is removed during the non-irrigation season.
EXISTING PUMPING PLANT
The existing pumping plant is located on the right abutment and supplies water to the
Highline and Savage Canals on the south or left side of the river and to the Tokay and
Evans Canals on the north or right side. The Highline and Savage Canals are above and
to the south of the South Main Canal on the left abutment. The pumping plant contains
three pumps powered by two hydraucone turbines located in each of the two water
passages. Water to power the turbines and supply the pumps comes from the pumping
plant intake structure. Approximately 800 ft3/s flows into either the turbines or the
chambers surrounding the turbines, referred to as the flumes or the turbine rooms. Water
passing through the turbines is directed downwards into two outlet conduits. These outlet
conduits are also used by the sluice gates. The outlet conduits are located beneath the
flumes, pump room, and a portion of the north fish ladder. Water flowing through the
outlet conduits returns to the river through the tailrace located downstream of the
pumping plant. Water that does not pass through the turbines flows into the two flumes.
Water within the flumes is pulled into either a 24-inch or a 30-inch diameter suction pipe,
located in the floor, which leads to the pumps and pipelines to the irrigation canals.
Hydraucone Turbines and Centrifugal Pumps
A hydraucone turbine consists of a fixed metal cone which forms part of the water
passage. The two hydraucone turbines have a 900-horsepower capacity each when
operating with an effective head of 28 to 30 feet and a total combined discharge of
approximately 800 ft3/s. Power for the three centrifugal pumps located at the
downstream end of the pumping plant is provided by the two hydraucone turbines. The
left turbine drives a single centrifugal pump, with a capacity of 67 ft3/s against a 90-foot
head, which discharges into the 42-inch-diameter steel pipe that runs longitudinally
within the dam to the left abutment and then up to the Highline and Savage Canals. The
right turbine drives two centrifugal pumps, connected in series (a low and a high pressure
pump), with a combined capacity of 40 ft3/s against 150 feet of head. These pumps
supply a 42-inch-diameter steel pipe that rises vertically out of the pumping plant and
then runs up the right abutment to the Tokay and Evans Canals.
FISH LADDERS
There are two fish ladders located on each abutment to allow fish to migrate past the
dam. The north fish ladder is located on the right abutment and the south fish ladder is
located on the left abutment. During the irrigation season when the reservoir is raised,
both fish ladders are used. During the non-irrigation season when the reservoir is near
the crest of the dam, only the lower portion of the south fish ladder is used. The north
fish ladder is not used during the non-irrigation season because of the shallow depths near
the upstream entrance due to sediment buildup. The upper portion of the south fish
ladder is not used during the non-irrigation season because the entrance is above the crest
of the dam. During the non-irrigation season, the river overtops bays 1 through 16, with
fish passage provided by the lower portion of the south fish ladder by flows overtopping
bays 14 through 16. Fish jump over the dam crest from the upper resting pool of the
south fish ladder into the reservoir. The radial gates in the outlet works are typically not
used for fish passage and are usually kept closed. However, the radial gates are the only
viable fish passage whenever the reservoir is drawn down below the crest of the dam.
North Fish Ladder
The north fish ladder is a rectangular concrete structure with pools 8 to 9 feet long and 9
feet wide. The upstream entrance to the fish ladder, which supplies water from the
reservoir, is located in a wing wall connected to the right wall of the pumping plant. The
upstream entrance is controlled by a hand-operated cast iron slide gate. The north fish
ladder extends downstream, going through three wing walls between the right abutment
and the right abutment wall of the pumping plant, for a distance of about 150 feet. It then
turns 180 degrees and extends back toward the pumping plant for about 100 feet, then
turns 90 degrees and extends along the downstream wall of the pumping plant (suspended
above the tailrace area) for about 40 feet to the first pier in the dam and the downstream
entrance into the river. Supporting the north fish ladder is a reinforced concrete gravity
wing wall anchored into the right abutment. The wing wall is located below the fish
ladder to prevent erosion from the river. The downstream entrance of the north fish
ladder is located next to the tailrace area of the pumping plant. The 24-inch diameter
steel pipe from the fishport bypass system discharges into the tailrace area and is used as
an attractant for fish to the downstream entrance of the north fish ladder.
South Fish Ladder
The upstream entrance to the south fish ladder is located within the right wall of the
gravity canal headworks, approximately 150 feet downstream from the face of the dam.
The upstream entrance is controlled with wooden stoplogs. Water from the gravity canal
headworks flows into the upstream entrance of the south fish ladder and makes an
immediate 90-degree turn. The water then flows down the upper portion of the fish
ladder approximately 100 feet back toward the dam and discharges into a large upper fish
resting pool, located immediately downstream from the dam. The upper portion of the
fish ladder contains 10 pools. Releases from an 18-inch-diameter steel pipe between the
reservoir and the upper fish resting pool are meant to attract migrating fish to the upper
portion of the south fish ladder. Migrating fish then swim up the upper portion of the fish
ladder, into the gravity canal headworks and into the reservoir. The lower portion of the
south fish ladder, constructed on rock downstream from the dam, consists of a series of
ladders, pools, and concrete walls, extending from the upper fish resting pool to the river.
RESERVOIR
Savage Rapids Diversion Dam creates a reservoir that extends ½ mile upstream during
the non-irrigation season (2,300 acre-feet) and 2 ½ miles upstream during the irrigation
season (3,200 acre-feet). The reservoir is relatively narrow, only two to three times wider
than the natural river channel within the ½-mile reach just upstream from the dam.
Because Savage Rapids Diversion Dam serves principally as a diversion for irrigation,
there is no carryover storage in the reservoir and no flood protection.
Reservoir Sediments
There is an estimated 200,000 cubic yards of sediments deposited within the one-half
mile immediately upstream of the dam. This represents approximately 2 to 2 ½ years of
the average annual sediment load transported by the Rogue River at downstream Grants
Pass. The reservoir sediments consists of 2 percent fines (silt and clay-sized particles),
71 percent sand, and 27 percent gravel overall with 20 percent of the deposit being
cobbles 3 to 5 inches in diameter. A finer-grained bar deposit is present on the south side
of the reservoir, but is less than 10 percent of the total sediment volume.
Of the 200,000 cubic yards of reservoir sediments, approximately 175,000 cubic yards is
located within a 25-foot deep “gravel bar” on the right side of the reservoir, just upstream
of the dam and existing pumping plant, in the deepest part of the original river channel.
Reservoir sediments accumulating in front of the existing pumping plant intake structure
have to be periodically removed to keep the pumping plant operational. The sluice gates
remain buried in sediments.
The reservoir probably filled with sediments within the first few years of operation.
Sediment transport on the river typically occurs during the high flow periods of winter
floods and spring snowmelt runoffs. Most of the sediments currently transported by the
river pass over the dam during the non-irrigation season. Testing of the sediments
indicated that there are no hazardous materials or contaminants with concentrations
significantly higher than naturally occurring background levels.
Operating the radial gates to draw down the reservoir effectively unwaters the right side
of the reservoir and exposes the gravel bar that leads to the existing pumping plant intake.
Opening the radial gates also sluices an upstream channel in the reservoir sediments.
HYDROLOGY
Flood events at Savage Rapids Diversion Dam pass over the overflow portion of the dam,
or the installed stoplogs, depending on the time of year. There is no flood surcharge
capability in the reservoir and floods pass over the dam without attenuation. Flood
events typically occur during the winter, non-irrigation, months. Winter floods can occur
anytime between November 1 and May 31, with June and October considered to be
transitional months. July 1 through September 30 is considered to be the summer low
flow period. The largest floods typically occur between November 1 and March 31, with
most occurring in December and January. The magnitude of the flood peaks have been
significantly reduced following construction of upstream Lost Creek Dam (1977).
The dam has safely passed numerous floods in the past, including a 1927 flood having a
peak discharge of 117,000 ft3/s. The largest flood that has occurred at Savage Rapids
Diversion Dam since Lost Creek Dam began regulation was in January 1997, with a
maximum mean daily peak of 69,000 ft3/s and an instantaneous peak of 90,800 ft3/s.
Prior to Lost Creek Dam, the largest flood occurred in December 1964 with a mean daily
peak of 124,000 ft3/s and an instantaneous peak of 152,000 ft3/s (December 23, 1964).
With the partial removal of the dam, the maximum water surface of the river at the dam
site during the 100-year flood is estimated to be 11 feet above the top of the remaining
left side of the dam. The peak flow for the 100-year flood is approximately 109,500 ft3/s.
DAM REMOVAL
Initial alternatives focused on removing the entire dam and pumping plant. However, an
economic decision was made to only remove portions of the dam necessary to restore
permanent fish passage and river navigation through the site. Partial removal of the dam
includes removing that portion of the dam in the deepest part of the river channel (bays 1
through 9, including piers 2 through 9). The top of piers 10, 12 14, and 16 down to the
top of the dam also will be removed to eliminate a boating hazard. All of the mechanical
equipment associated with the dam, including the cableway, will be removed by the
GPID for salvage.
The structures that will remain on the right side include the existing pumping plant, the
north fish ladder, a vertical upstream concrete wall supporting a roadway, the
downstream concrete apron in the tailrace area, a gravity wing wall beneath the north fish
ladder, and the upstream concrete cutoffs at the base of the arches in bays 1 through 7. It
is anticipated that the concrete apron and cutoffs will be near the top of the cemented
gravels and the invert of the original river channel after the right side of the dam is
removed. The structures that will remain on the left side include bays 10 through 16, the
gravity canal headworks, and the south fish ladder. All of the upstream openings in the
remaining structures will be plugged with reinforced concrete. All exposed
reinforcement will be cut flush with the remaining concrete surfaces so they do not
become a hazard to fish. Removal of the dam is expected to take place during 2009.
Fish Passage and River Diversion
Fish passage and river diversion through the site must be maintained during removal of
the dam. Fish passage and river diversion will be provided by opening the radial gates in
bays 10 and 11 during reservoir draw downs, over the left side of the dam into the lower
portion of the south fish ladder during removal of the right side of the dam, and through
the original river channel on the right side during removal of the left side of the dam.
Once the dam is removed, fish passage and river diversion through the site will have been
permanently restored in the original river channel on the right side. The north fish ladder
will not be used during the removal of the dam.
Fish normally employ cruising speed for movement (migration), sustained speed for
passage through difficult areas, and darting speed for feeding or escape purposes. Fish
passages should be well under the darting speed of the species involved, but may exceed
their cruising speed. Chinook and Coho have cruising speeds of approximately 4 ft/s,
sustained speeds of approximately 11 ft/s, and darting speeds of approximately 22 ft/s.
Steelhead have cruising speeds of approximately 5 ft/s, sustained speeds of
approximately 15 ft/s, and darting speeds of approximately 27 ft/s. Velocities of 8 to
12 ft/s are considered to be the upper limit for fish passage. Fish passage was considered
possible for a maximum flow velocity of 10 ft/s during dam removal.
Fish passage through the open radial gates has been observed in the past, but is dependent
upon the velocity of the flow through the gate openings and in the downstream diversion
channel back to the river. Flow in the diversion channel has been observed to be a very
turbulent, high velocity plume. Calculations indicate that fish passage through the radial
gates and diversion channel is possible for flows up to approximately 2,200 ft3/s and
velocities up to approximately 10 ft/s. It is anticipated that the radial gates will be
operated slowly and velocities through the partially open gates may prohibit fish passage.
Fish passage and river diversion through the open radial gates are anticipated to be kept
to a minimum of a few days each time the gates are operated during dam removal.
Fish passage and river diversion over the left side of the dam into the lower portion of the
south fish ladder will be similar to what is currently done during the non-irrigation
seasons. Overtopping bays 14 through 16 into the lower portion of the south fish ladder
provides fish passage while overtopping bays 9 through 13 into the river channel
provides river diversion. Diverting the entire river over bays 14 through 16 alone would
likely overwhelm the lower portion of the south fish ladder. Flow velocities overtopping
bays 9 through 16 are less than 10 ft/s for flows less than approximately 6,000 ft3/s. For
larger flows, the radial gates could be re-opened to provide additional discharge and keep
flow velocities over bays 14 through 16 below 10 ft/s for fish passage.
Considerations
Partial removal of the dam will take place in two stages. The first stage removes the right
side of the dam and uses the left side for fish passage. The second stage moves the river
to the right side for permanent fish passage and removes the left side of the dam. Access
needs to be provided to both sides of the dam for removal. The right side of the dam is
located within the deepest portion of the original river channel and the gravel bar of
sediments. It is anticipated that the river will return to the original channel on the right
side once the dam has been removed and reservoir sediments have eroded. While
removal of the right side of the dam will occur during the irrigation season, diverting the
river to the right side will not take place until the end of the irrigation season to prevent
eroding sediments from damaging the intakes of the new pumping plant.
The Oregon Department of Fish and Wildlife (ODFW) has established guidelines for the
timing of in-water work to minimize potential impacts to fish, wildlife, and habitat
resources. For the Rogue River at Savage Rapids Diversion Dam, the currently
established in-water work period is from June 15 to August 31, which occurs during the
irrigation season. In-water work periods are established to avoid the vulnerable life
stages (migration, spawning and rearing) of important fish species including anadromous
and other game fish and threatened, endangered, or sensitive species. For Savage Rapids
Diversion Dam, this includes the spring Chinook salmon and winter steelhead. It has
been observed that fall salmon spawning at the dam begins October 1. To accommodate
the in-water work period, the dam removal site will be isolated from river flows by
cofferdams and drawing down the reservoir to enable work to be done in the dry.
Underwater blasting to remove the dam was not considered due to adverse impacts to fish
(including eggs and larvae) and habitat, residual concrete debris left in the channel, lime
dust in the river resulting from the blasting, and the permitting process. In addition,
underwater blasting would have to be done during the in-water work period which
coincides with the irrigation season. Removal of the dam during the irrigation season
would expose the new downstream pumping plant intakes to eroding reservoir sediments.
The worksite will be protected up to the 5-year flood event for construction efforts, and
up to the 2-year flood event for deconstruction efforts. The 5-year flood is an annual
event, but the 2-year flood is only a seasonal event. The right side cofferdam was
designed for the 2-year seasonal flood, and to accommodate overtopping the left side of
the dam for fish passage through the lower portion of the south fish ladder
A hazardous materials survey of the existing pumping plant determined the only
hazardous materials present which may potentially impact dam removal operations were
small quantities of oils and greases, along with very few painted surfaces. Lead-based
and zinc-chromate paints may exist on the railings and grates used on top of the pumping
plant. There are no transformers in the pumping plant.
Reservoir Drawdown and Right Side Access Roads
The first step for dam removal is opening the two radial gates to draw the reservoir down
below the dam crest and expose the sediments on the right side. This permits
construction in the dry of the upstream and downstream access roads, and a cofferdam on
the right side while the river is diverted through the open radial gate. This first step will
be done during a three week period in April, which is during a low level in fish
migration. The upstream access road provides access to the cofferdam and reservoir area
for removal of the right side of the dam. The upstream access road also serves as part of
the cofferdam and eventually will extend down to the bottom of the dam-removal
excavation. The downstream access road provides access to the downstream portion of
the right side cofferdam. The two access roads connect at the top of the right side
cofferdam, as shown in figure 1.
Right Side Cofferdam
The right side cofferdam enables the right side of the dam to be removed in the dry. The
right side cofferdam extends from the upstream access road, along the upstream channel
to the river outlet works, continues across the dam at approximately bay 8, ties into a rock
knob just downstream of bays 8 and 9, around the downstream concrete apron and ties
into the downstream access road downstream of the north fish ladder on the right
abutment. It is anticipated that the right side cofferdam will consist of reservoir
sediments, fabric bags filled with reservoir sediments, vertical sheet piles, and riprap for
slope protection. The area between the upstream portion of the right side cofferdam and
the right side of the dam will have been dewatered during reservoir draw down. The area
between the downstream portion of the right side cofferdam and the right side of the dam
will be unwatered and trapped fish will be salvaged and returned to the river.
The upstream portion of the right side cofferdam will be constructed in the dry with the
river diverted through the open radial gates. Permission was given to build the
downstream portion of the right side cofferdam in the wet outside of the in-water work
period because of low fish migration during this time. The sour hole will be filled with
cobbles, pit run sand, and a gravel cap before placement of the downstream portion of the
right side cofferdam. It is anticipated that the cobbles and cap will remain in place after
the dam and cofferdams are removed.
Figure 1 – Right side cofferdam and access roads.
Excavation of Reservoir Sediments
Once the right side access roads and cofferdam are in place, and the radial gates have
been closed to refill the reservoir to provide fish passage over the left side of the dam, the
next step in dam removal is excavating the reservoir sediments to provide access to the
upstream face of the dam. The top of the sediments is within a few feet of the top of the
dam. The sediments will be excavated approximately 15 to 20 feet to nearly foundation
to fully expose the arches in the right side of the dam for removal, as shown in figure 1.
The upstream concrete cutoffs at the base of each arch will remain. It is anticipated that
the top of the remaining cutoffs will be near the top of the cemented gravels and the
invert of the original river channel.
Removal of Right Side of Dam
Removal of the right side of the dam consists of removing the reinforced concrete in the
1- to 2-foot-thick arches and piers of bays 1 through 7. The 42-inch diameter steel pipe
located within these bays also will be removed. It is anticipated that removal of the right
side of the dam will begin at bay 1 near the existing pumping plant and proceed from
right to left. Sawcutting between concrete to be removed and concrete to remain was
determined to be unnecessary. The remaining rough surface will not to be harmful to
fish. Removal of the concrete from the right side of the dam will most likely be done
using mechanical methods (hoe rams, jackhammers, etc.) to break up the concrete, and
backhoes and dump trucks to remove the concrete debris via the upstream access road.
Mechanical methods are more suited for removal of the thin arch sections of the dam. It
may be difficult to drill and blast the thin sections of the arches. Mechanical methods
also will be effective in removal of the gravity sections in the left side of the dam if the
compressive strength of the concrete is less than 3,500 to 4,000 lbs/in2. Mechanical
methods may be faster than blasting in during dam demolition and will create about the
same amount of dust and debris.
Excavation of reservoir sediments and removal of the right side of the dam is expected to
take place over approximately 18 weeks, prior to the end of the irrigation season. Ending
the irrigation season prior to October 1st would accelerate removal of the left side of the
dam prior to winter flooding.
Erosion of Reservoir Sediments
Once the right side of the dam has been removed, the reservoir will again be draw down
by opening the radial gates. Riprap, fabric bags, and sheet piles in the right side
cofferdam will either be completely or partially removed. Partial removal of these
materials allows the remaining materials to be reused as part of the left cofferdam for
removal of the left side of the dam. A pilot channel excavated through the upstream and
downstream portions of the right side cofferdam, and through the reservoir sediments,
will facilitate removing the cofferdam when the river is moved to the right side. Opening
the radial gates, drawing down the reservoir, partially dismantling the cofferdam and
excavation of the pilot channel will take place over approximately 3 weeks. Removal of
the right side cofferdam, access roads, and reservoir sediments will be done by the river
flowing into the pilot channel and moving to the right side of the channel. It is important
to note that the river will not be redirected to the right side until the end of the irrigation
season. The intakes of the new pumping plant will be damaged if they are operating and
subjected to eroding sediments.
Moving the river to the right side may require closing the radial gates, allowing the
reservoir to rise and the river to flow into the pilot channel. Erosion of the right side
cofferdam, access roads, and most of the reservoir sediments is expected to occur rapidly
as the river flows through the pilot channel and moves back to the original channel on the
right side. The sediments are expected to erode vertically, in an upstream direction,
through a head-cut process until the pre-dam riverbed slope is achieved. Following the
head-cut process, the pilot channel is expected to erode laterally (widen). The degree of
widening is dependent on the magnitude of flow. As flows increase the widening will
increase until the majority of sediments are eroded. Approximately 150,000 cubic yards
are expected to be eroded away within a one to two week period, depending upon the
flow. The erosion is not expected to cut below the original channel invert.
This initial flushing of the reservoir sediments will cause sediment concentrations
downstream from the dam to increase significantly for a short duration of time. The
remaining 50,000 cubic yards of sediments are expected to be flushed downstream during
higher winter flows. The city of Grants Pass water intake and treatment plant are located
about 5 miles downstream of the dam. Erosion of the sediments could adversely impact
the treatment plant. Winter flooding is necessary to move the sediments downstream past
the city of Grants Pass intake. It is recommended that sediment levels in the river be
closely monitored during the initial flushing.
Left Side Cofferdam and Access Road
Construction on the left side cofferdam and upstream access road will begin while the
river is eroding the right side cofferdam, access roads, and reservoir sediments. This will
occur at the end of the irrigation season and outside of the in-water work period. It is
anticipated that with the eroding sediments, construction of the left side cofferdam and
upstream access road will not significantly add to the turbidity in the river. The upstream
access road on the left side is required to provide access to the left side cofferdam and
reservoir area for dam removal. A cofferdam on the left side is required for removal of
the left side of the dam in the dry. It is assumed that a downstream access road on the left
side will have been provided by construction of the new pumping plant. It is anticipated
that the left side cofferdam will consist of reservoir sediments, fabric bags filled with
sediments, and riprap for slope protection, all taken from the right side cofferdam. The
left side cofferdam will extend around the left end of the dam to facilitate removal and
will cover the upstream and downstream diversion channel to the radial gates, as shown
in figure 2. The area behind the left side cofferdam will have to be unwatered and any
trapped fish salvaged and returned to the river. Construction of the left side cofferdam is
expected to take approximately 2 weeks.
Figure 2 – Left side cofferdam and access road.
Removal of the left side of the dam consists of removing the reinforced concrete in bays
and piers 8 and 9 down to foundation. The top of concrete piers 10, 12, 14, and 16 will
be removed down to the top of the dam so they do not become a boating hazard or a
potential debris barrier. The 42-inch diameter pipe opening and narrow gallery in pier 10
will be plugged with reinforced concrete. After the radial gates are removed, bays 10 and
11 will be plugged with reinforced concrete and riprap. The two gate openings in the
gravity canal headworks will be plugged with reinforced concrete. The concrete in bays
10 through 16, the south fish ladder, and the gravity canal headworks will remain.
Removal of the left side of the dam is expected to take approximately 7 weeks.
Once the left side of the dam is removed, the left side cofferdam and upstream access
road will be removed outside of the in-water work period. Removal of the cofferdam and
access road will be done by mechanical methods down to the water surface. Winter
flooding will remove the rest of the cofferdam and access road.
CONCLUSIONS
Partial removal of the Savage Rapids Diversion Dam will permanently eliminate a major
source of anadromous fish mortality in the Rogue River. Construction of a new diversion
facility and removal of the dam will protect juvenile fish from entrainment into irrigation
canals and will eliminate migration blockages caused by the dam. Removal of the dam
also will provide boat passage on the river through the site. Removal of the dam will not
take place until new pumping plant is available for irrigation.
Constructing a new diversion facility just downstream of the dam and partial removal of
the dam provides the least-cost alternative for providing permanent fish and boat passage
through the site, and for fulfilling irrigation demands on both sides of the river. Partial
removal of the dam leaves abandoned structures on both abutments. For safety and
security reasons, the remaining portions of the dam will be surrounded by fencing to keep
the public out. Upstream openings in the remaining structures will be plugged with
reinforced concrete. These remaining structures may be removed at a later time if
needed. There is no significant hazardous material issues related to the removal of the
dam or the reservoir sediments. Relocating the river to the right side will not take place
until the end of the irrigation season and when the intakes for the new pumping plant are
protected from the eroding sediments. Erosion of the sediments will damage the intakes
of the new pumping plant if they were operating.
Erosion of the cofferdam and a large portion of the reservoir sediments are expected to
take place quickly (within a one to two week period), depending upon the rate of flow.
Modeling of the river shows that once the dam is removed, virtually all the existing
sediments will eventually be eroded from the reservoir. Any sediments remaining after
the initial flushing will erode during high-flow periods that most likely will occur during
the non-irrigation seasons (winter floods and spring snowmelt runoffs) when the new
pumping plant is not operating. River flows and natural sediment loads are expected to
return to pre-dam levels during future irrigation seasons. Therefore, future sediment
impacts on the new pumping plant are expected to be minimal.
The initial reservoir draw down to construct access roads and the right side cofferdam
will take approximately 3 weeks. Excavation of reservoir sediments and removal of the
right side of the dam is expected to take approximately 18 weeks. Opening the radial
gates to draw down the reservoir to partially dismantle the right side cofferdam and
excavate a pilot channel will take approximately 3 weeks. Construction of the left side
cofferdam will take approximately 2 weeks. Removal of the left side of the dam will take
approximately 7 weeks.
REFERENCES
Bureau of Reclamation, Fish Passage Improvements, Savage Rapids Dam, Planning
Report and Final Environmental Statement, August 30, 1995.
Bureau of Reclamation, Savage Rapids Dam, Sediment Evaluation Study, February 2001.
Corps of Engineers, North Pacific Division, Portland, Oregon, Fisheries Handbook of
Engineering Requirements and Biological Criteria, Fish Passage Development and
Evaluation Program, 1990.
National Marine Fisheries Service, Northwest Region, Portland, Oregon, Anadromous
Salmonid Passage Facility Guidelines and Criteria, January 31, 2004.
Oregon Department of Fish and Wildlife, Oregon Guidelines for Timing of In-Water
Work to Protect Fish and Wildlife Resources, June 2000.