SWT-2015-775

Description of Work:  The applicant proposes the placement of approximately 65,610 cys of fill material below the ordinary high water mark (OHWM) of the Arkansas River.   This proposal would result in the placement, redistribution, and the excavation of riverbed materials within waters of the United States.   A total of approximately 27,400 cys of earthen material (after compaction) would be excavated and used to construct the LWD.  Additionally, 13,700 cys of excavated rock and 33,904 cys of concrete fill material consisting of stone and gravel, sand, cement, and water would also be used to construct the LWD.   

The applicant proposes bank stabilization along the riverbank at eight locations.   These locations would be armored by utilizing revetment riprap with launchable stone toe, stone toe wedge, or longitudinal peaked stone toe.  A total of approximately 14,973 cys of fill material consisting of 18- to 24-inch riprap/rock boulders and geotextile fabric would be used for bank stabilization to protect 6,441 linear feet (lf) of riverbanks.  

The applicant also proposed seven public access features which would result in approximately 12,749 cys of rock and soil/sand fill material placed below the OHWM.  The public access features would be placed on both banks of the Arkansas River.  Approximately 871 cys of rock fill material would be used to construct the public access areas.  Approximately 11,274 cys of sand/soil fill material would be used to construct acess areas to accommodate recreational features.  These features would consist of boat docks, ramps, landing areas, water features, playgrounds, splash pads, multi-use trails, climbing walls, overlooks, restrooms, and a 20-foot wide bicycle/pedestrian bridge.

The work associated with construction of the LWD and appurtenant features would be completed using wheeled and tracked excavation equipment (backhoes, track hoes, dozers, dump trucks, and front-end loaders), drilling rigs, concrete trucks, concrete pumping equipment, compactors, and graders.

The table of impacts below depicts the breakdown of excavated materials, fill materials, and quantities by acres and linear impacts.

Table of Impacts:

Dimensions of Dam Structures:

The new dam construction is 1,850 ft in length with a total gate area of 5,880 square (sq) ft or approximately 44 percent of the total dam face area. The full-height gate length is 600 ft, crest gate length is 560 ft, and fixed crest dam length is 690 ft.  Gates will be installed to the dam to facilitate flow management and sediment transport.  The low water dam has three different cross-sections: a fixed crest section, a 3-ft crest gate section, and a full-height gate section. The full-height gate section is 7 ft high at low water dam. The low water dam geometry is included below.  The proposed dam sections will be constructed of mass concrete founded upon the underlying shale bedrock and extending up to the design crest (or sill) elevation at each section to meet crest elevation and sediment management requirements. 

Additionally, steps will be installed immediately below the dam to mitigate the dangerous hydraulic roller effect.  A hydraulic roller is the hydraulic condition below a dam caused by the vertical drop in water surface that creates dangerous conditions. The geometry of the stepped face is hydraulically determined; however, these steps have relatively low structural demands and could be constructed of mass concrete, grouted riprap, anchored stone blocks, or other material with density similar to concrete.

The dam includes inflatable air bladder operated gates.  A specific gate layout was developed for the dam using both full-height and crest gates to provide for the operational level control, allow sediment passage, and address the Federal Emergency Management Agency’s (FEMA’s) floodway requirements.

The dam will provide support for the 20 ft wide pedestrian bridge structure and aid in the performance of some maintenance functions.  The bridge will include several seating, fishing, and overlook areas to enhance recreational opportunities. The dam will incorporate integral columns to support a pedestrian bridge across the river.  These columns will be structurally connected to diaphragm walls that separate the various sections at the dam (fixed crest, crest gate, and full-height gate).

South Tulsa/Jenks Dam Elements

Note #1:  The applicant has noted that potential waters of the United States identified within the proposed study area included the following below:

1. Vegetated and Non-Vegetated Sandbars (R2UBH/R2USJ) – 457.11 acres
2. Emergent Marsh Wetlands (PEM1F) – 12.37 acres
3. Scrub-Shrub Wetlands (PSS1C) – 0.78 acre
4. Vensel Creek (R2UB1J) – 408 lf
5. Fred Creek [remnant] (R4UBH) – 584 lf

Note #2:  The construction of the LWD would establish a static pool at elevation 597 ft above MSL, resulting in a lake depth of 7 ft at the dam.  Under low-flow conditions (essentially no releases from Keystone Dam), the new static pool would cover an area of approximately 468 acres and be approximately 3.5 miles (19,000 ft) long and lake depth ranging 0 ft at the end of the pool length to 7 ft at the dam.