(7.1) WATER DATA - Ocklawaha River Cross Florida Barge Canal structures
Cross Florida Barge Canal structures:
Eureka Lock and Dam
Rodman Dam, Pool, and Spillway
SR-40, CR-316, and SR-19 high-profile bridges
Henry H. Buckman Lock
An Information, Opinion, & Sources Report
Compiled by Ocklawahaman Paul Nosca
Created: 13 October 2013
Last Revised: 29 May 2015
This webpage shall be revised from time to time for accuracy and better grammar
or as additional pertinent information is obtained!
Eureka Lock and Dam (including Spillway and "Eureka Pool")
Construction: Eureka Lock and Dam was constructed in Marion County by the U.S. Army Corps of Engineers (USACOE) between 1966 and 1970, as part of the 107 mile Cross Florida Barge Canal (CFBC) project. Although the lock and spillway structures are complete, they have never been operational because the earthen dam was never closed across the Ocklawaha River main channel at Eureka. All further construction of the CFBC was halted by President Richard M. Nixon on 19 January 1971 and the project was later de-authorized by the U.S. Government.
Earthen Dam: Would have been 4000 feet in length (including the 2-gate spillway and lock) across the Ocklawaha Valley at Eureka--if the final 400-foot river channel gap had been filled. The top of the dam's "crown", wherever completed, is 48 feet above mean sea level (MSL).
Lock: Like the "Buckman" Lock except for higher elevations above MSL. Operation of Eureka Lock for barges required a 38 to 40-foot above MSL "Eureka Pool" to maintain a water depth of 12 to 14 feet because the top of the upstream "sill" is 26 feet above MSL. The top of the downstream sill is 6 feet above MSL.
No UPSTREAM water flows into it.
Spillway: Similar to Rodman Spillway but has 2 gates (each 40 feet wide and 15 feet high), instead of Rodman's 4 gates, making Eureka Spillway half as wide. The top of the spillway's concrete "crest" (which the water would spill-over) is 26 feet above MSL. Its "sloping apron" is 139 feet long and ranges from 10 feet to -4 feet MSL.
No water flows through it.
Spillway Discharge Channel: Extends north 0.6 miles to its junction with the river. Its bottom width is up to 150 feet and its depth ranges from 8 to 20 feet (if water elevation "stage" is 20 feet above MSL).
River miles upstream from Rodman Dam: Eureka Lock and Dam is about 21 river miles upstream, on the Ocklawaha River, from Rodman Dam.
Present use: Land is leased to Marion County (deputy sheriff and his family lives onsite).
Planned "Eureka Pool": Had the earthen dam been closed across the Ocklawaha River, an approximately 19,700 acre impoundment for navigational purposes would have been created (upstream of Eureka Lock and Dam). Eureka Pool was engineered to have a "full pool" of 40 feet above MSL with a "maximum pool" of 43 feet above MSL. The mean elevation at Silver Springs, some 23 miles upriver from Eureka, is only about 40 feet. About 20 river miles of the natural Ocklawaha River would have been flooded plus maybe an additional 20 stream miles or so of its secondary channels and tributaries.
Rodman Dam (and Spillway) and Pool
Construction: Rodman Dam (and Spillway) was constructed in Putnam County by the USACOE between 1966 and 1968, as part of the 107 mile CFBC project. The earthen dam was closed on 30 September 1968.
Earthen Dam: Some 7200 feet in length (including the 4-gate spillway) across the Ocklawaha Valley at Rodman with a base 300 feet wide and a crown 30 feet wide. The top of the dam's crown is 28 feet above mean sea level (MSL) or 22 feet above natural ground elevation.
Spillway: 4 metal gates (each 40 feet wide and 15 feet high) which mechanically lift above the concrete crest. The top of the spillway's concrete crest (which the water spills-over) is 6 feet above MSL. Its sloping apron is 100 feet long and ranges from -3 feet to -15 feet MSL.
Spillway Discharge Channel: Extends southeast 1 mile to its junction with the river. Its bottom width is 150 feet and its depth is about 8 to 20 feet (depending upon discharge through the spillway).
River miles upstream from St. Johns River: Rodman Dam (and Spillway) is about 11.6 river miles upstream, on the Ocklawaha River, from its mouth at the St. Johns River.
Rodman Pool (a.k.a. Rodman Reservoir or Lake Ocklawaha): Created upstream of Rodman Dam, Rodman Pool was engineered to have a "full pool" for barge navigation purposes of 20 feet above MSL with a "maximum pool" of 22 feet above MSL. Since 1969, however, it has usually been maintained at its "minimum pool" of 18 feet above MSL by the USACOE. Rodman Pool at 18 feet above MSL covers some 9,200 acres, and is about 15 miles long and nearly 2 miles wide near the dam. At 20 feet above MSL, it floods about 13,000 acres and is about 16 miles long. Natural terrain slopes upward toward the upstream (Eureka) end of the pool.
Pool elevation above MSL = approximate acreage flooded:
20 feet above MSL = 13,000 acres;
19 feet above MSL = 11,000 acres;
18 feet above MSL = 9,200 acres;
17 feet above MSL = 8,300 acres;
16 feet above MSL = 7,500 acres;
15 feet above MSL = 6,500 acres;
14 feet above MSL = 5,750 acres;
13 feet above MSL = 5,150 acres;
12 feet above MSL = 4,600 acres;
11 feet above MSL (targeted low level of recent draw-downs) = 4,300 acres.
Pool Clearing: Rodman Pool was only partially cleared prior to 30 September 1968. Using the 306 ton "Crusher-Crawler" (or "Monster") where the 12-foot deep CFBC was to be dug through the pool, trees were "crushed-down" entirely along a 400-foot wide path throughout the length of the route. In other areas, trees were selectively cleared or left standing for fishery habitat. In all, 5,500 acres were totally cleared. The remaining forest was partially cleared or left standing (possibly 2,000 acres of these woods have since "drowned"). The 13,000 acre "Rodman Reservoir" achieved the USACOE 1969 "Conservation of Natural Beauty Award" for leaving 5,500 acres of natural wetlands un-cleared.
Opinion of Ocklawahaman about Rodman Pool Evaporation:
Ever since its creation, Rodman Pool has exposed some 4,300 to 13,000 surface acres of impounded water to evaporation losses. Ocklawahaman opines that the natural Ocklawaha River between Eureka and Rodman, including its secondary and tributary streams, would only amount to perhaps 500 surface acres of swift-flowing water usually exposed to evaporation losses.
Backwater Effect of Rodman Dam upon the Ocklawaha River upstream:
According to the Florida Department of Environmental Protection fact sheet, "When maintained at 18 feet above sea level the backwater effect of the reservoir ends about 2 miles downstream of Eureka Lock." This would place the end of the backwater effect (from an 18-foot pool) at about 2.5 miles downriver (N) of the CR-316 Eureka Bridge.
Opinion of Ocklawahaman about Backwater Effect of Rodman Dam:
Ocklawahaman, however, opines that the backwater effect (river level held up higher than natural) caused by Rodman Dam at 18 feet may reach miles further upriver. Review of USGS "gage height" data of annual high water and low water river levels over a 13-year period from 2000 to 2012 shows the following result. The gage at the CR-316 Eureka Bridge recorded all 5 of its lowest elevation periods (at 17.62 feet or less above MSL) during Rodman DRAW-DOWNS while the 17.9-mile further upstream SR-40 Delks Bluff Bridge gage posted only 2 of its 5 lowest elevation periods (at 34.58 feet or less above MSL) during Rodman DRAW-DOWNS. Ocklawahaman theorizes that when maintained at 18 feet above MSL, the backwater effect of Rodman Dam can extend upriver as far as the CR-316 Eureka Bridge crossing.
Calculations by Ocklawahaman about Backwater Effect of Rodman Dam:
The natural flowing Ocklawaha River descends 56 miles to the St. Johns at an overall average of 0.7 feet per mile from its usual Silver Springs headwaters but the fall varies somewhat between these 4 segments:
Silver Springs to SR-40/Delks Bluff (5.0 river miles) drop = about 0.8 feet per mile average.
SR-40 to CR-316/Eureka (17.9 river miles) drop = about 0.9 feet per mile average.
CR-316/Eureka to Rodman Dam (21.5 river miles) drop = about 0.74 feet per mile average.
Rodman Dam to the St. Johns (11.6 river miles) drop = about 0.3 feet per mile average.
Ocklawahaman estimates that every extra 0.74 feet of higher elevation pool at the upstream side of Rodman Dam increases the backwater effect by one mile.
Approximate "backwater effect" of Rodman Dam in river miles from Eureka Bridge:
11 feet above MSL = backwater effect up to 9.5 mi downriver (N) of Eureka Bridge.
12 feet above MSL = backwater effect up to 8.1 mi downriver (N) of Eureka Bridge.
13 feet above MSL = backwater effect up to 6.8 mi downriver (N) of Eureka Bridge.
14 feet above MSL = backwater effect up to 5.4 mi downriver (N) of Eureka Bridge.
15 feet above MSL = backwater effect up to 4.1 mi downriver (N) of Eureka Bridge.
16 feet above MSL = backwater effect up to 2.7 mi downriver (N) of Eureka Bridge.
17 feet above MSL = backwater effect up to 1.4 mi downriver (N) of Eureka Bridge.
18 feet above MSL = backwater effect up to Eureka Bridge.
19 feet above MSL = backwater effect up to 1.3 mi upriver (S) of Eureka Bridge.
20 feet above MSL = backwater effect up to 2.7 mi upriver (S) of Eureka Bridge.
21 feet above MSL = backwater effect up to 4.0 mi upriver (S) of Eureka Bridge.
SR-40, CR-316, and SR-19 high-profile bridges
Marion County SR-40 "Bert Dosh Memorial Bridge" a.k.a. "Delks Bluff" Bridge: Originally constructed for the CFBC project in the late 1960's (but completed in 1972) with a vertical clearance of 49 feet over the Ocklawaha River at "low" water and a vertical clearance of 70 feet above the nearby dry CFBC route.
Marion County CR-316 "Eureka" Bridge: Originally completed for the CFBC project in 1969 with a vertical clearance of 49 feet over the Ocklawaha River at "low" water and a vertical clearance of 70 feet above the nearby dry CFBC route.
Putnam County SR-19 "Cross Florida Barge Canal" Bridge: Originally completed for the CFBC project in 1967 with a vertical clearance of 65 feet above the water of the CFBC.
Henry H. Buckman Lock
Construction: Henry H. Buckman Lock (originally "St. Johns Lock") was constructed in Putnam County by the USACOE between 1964 and 1968, as part of the 107 mile CFBC project. The CFBC project would have built a 12-foot deep and 150-foot wide (at the bottom) canal crossing Florida using 5 planned navigational locks and 3 planned dams. Henry H. Buckman Lock opened on 14 December 1968.
Construction Method: A 50-foot deep hole was excavated to the dimensions of the lock structure and was dewatered, and construction took place in the dry. When the concrete and steel lock chamber had been completed, dirt was pushed up to the sides of the lock and plugs of earth between the excavated sections of the canal were removed to allow water to flow into, and out of the lock, to connect the St. Johns River with Rodman Pool.
Lock Size: 600 feet long and 84 feet wide, and 14 feet over gate sills. The top of the concrete gate sill on the upstream side is 6 feet above MSL. The top of the sill on the downstream side is 15.5 feet below MSL. In addition, more than 7 miles of 14-foot deep (150 feet wide at the bottom) canal on either side of the lock have been completed.
Purpose of Lock: To lift boats and barges from the level of the St. Johns River to the level of Rodman Pool, usually about 18 to 20 feet above MSL.
Type of Lock: Concrete with reinforced steel, constructed on wooden poles driven into the ground to a solid foundation.
Number of Pilings: Some 2,141,000 pilings (wooden poles) were used as a foundation for the lock. If placed end to end the wooden poles would stretch about 40 miles.
Type of Gates: Miter gates, which resemble large barn doors. The gates seal at an angle so that water pressure on the upstream side keeps them sealed.
Weight, Size of Gates: Each leaf of the downstream (easterly) gates is 48 feet wide and 41 feet high and about 4 feet thick. The upstream (westerly) gates are 48 feet wide, 19 1/2 feet high and 4 feet thick. Each leaf in the upstream gates weighs 80,640 pounds, while the leaves in the downstream gates weigh 158,449 pounds each.
Filling and Emptying: Filling and emptying the lock chamber is by gravity. When filling the lock chamber, large valves are opened on the upstream side to allow water from Rodman Pool to flow into the lock chamber, via a 10-foot square tunnel and 17 ports on either side of the walls. When emptying the lock chamber the water is discharged via the 17 ports, tunnels and downstream valves to the downstream side of the lock chamber.
Water Level Gauges: Water level gauges inside the lock chamber and immediately beyond each end of the lock chamber show depths of water above the bottom.
Gallons of Water: Some 8,501,170 gallons of water are used in each lockage when the elevation of Rodman Pool is at 20 feet above MSL.
Transit Time: Normally it takes 15-20 minutes to lock a craft through the lock. This may vary slightly with the number of vessels going through at one time. Closing the gates takes about 2 minutes.
(1) The Lock Tender can only operate the miter gates from the control house located at each gate to assure proper miter and clearance of vessels and people.
(2) Lock operators give special instructions to boat operators as needed during locking operations.
(3) Pull-chain installed at each end of lock long wing-wall for use by small boats not equipped with signal devices or for boats too small to be observed by the lock operator or for signaling the lock operator.
(4) Floating mooring bits for boats and barges to tie-up to in the lock chamber rise and fall with water level in the lock.
(5) Standby generator will provide power for operation of the entire lock even when commercial power fails.
(6) Lock gates automatically slow down and stop near the full close and full open positions.
(7) Special procedures are followed when manatees (endangered aquatic mammals) are in the Lock or approach areas.
Who Operates the Locks: Operations and maintenance activities at the locks are performed by state employees under the direction of the Florida Department of Environmental Protection.
Canal miles from St. Johns River: Henry H. Buckman Lock is about 1.8 miles west-southwest, on the CFBC, from the St. Johns River.
Canal miles from Rodman Pool: Henry H. Buckman Lock is about 5.5 miles mostly east, on the CFBC, from Rodman Pool.
Links to online reports concerning the Ocklawaha River and its CFBC structures:
REFERENCE AS: Nosca, P. 2015. "Ocklawaha River Cross Florida Barge Canal structures" webpage report. "Ocklawahaman Paul Nosca reports" website. Paul Nosca, Eureka, FL.