JAP Additional Information Sheet

JAP Additional Information Sheet Block 15: Purpose and Need The USACE purpose of the project is to provide a safe and reliable whitewater park for the recreational public in a city park, which will provide economic development opportunities within the city limits. Block 16: Detailed Description of Each Activity Within Overall Project The Project consists of modifications in and along the Boise River occurring along an approximately 0.65- mile stretch extending from the pedestrian bridge, just downstream of the existing Thurman Mill Diversion, to the northwestern end of Veteran s Pond. The project is divided into three reaches, with Reach 1 extending from the pedestrian bridge to the existing Farmer s Union Ditch Company (FUDC) pushup berm diversion and canal intake. Reach 2 extends from the end of reach 1 to approximately 300 feet downstream of proposed drop structure 3. Reach 3 extends from the end of Reach 2 to the northwestern end of Veteran s Pond. The project measures for each reached are described in detail below. Reach 1 Side Channel / Islands: To add channel complexity and minimize impact to forested wetland, an approximately 600-foot-long side channel would be excavated with 2 islands separating it from the main channel. The new side channel would be excavated in the upland between the existing ESP parking lot and the Boise River. The riverbanks along this section are currently comprised of miscellaneous fill and are steep. Select areas along the existing bank that are forested wetland and contain large cottonwood trees would be maintained in place to create two island barriers. The islands would be stabilized and protected by installing rock armoring and woody debris. At the north end of the northern island a low-profile flow deflector would be constructed to direct flows away from the right bank and to the wave feature of drop structure 1. The new side channel would be lined with 4-inch minus river gravels and cobbles that would extend up the bank to the normal average spring runoff flow. This channel would have an approximately 2-foot water depth through the summertime when river flows typically range between 800 and 1,200 cfs. Riparian vegetation would be planted along the new shoreline in the southern and northern lengths. Remove Concrete Abutment: The old concrete abutment from the collapsed FUDC diversion and bridge structure on the left bank would be removed and the shoreline graded to match the upstream and downstream bank slopes. Reach 2 Drop Structure 1: The FUDC irrigation diversion (push-up berm) would be replaced with an adjustable crest gate structure (drop structure 1). Drop structure 1 consists of an Obermeyer spillway section, wave feature structure, fixed crest grouted rock riprap, fish ladder and a sluice channel. A sheetpile wall would be installed below the structure and would tie into each bank. The sheetpile wall would provide structural stability to the bank. The wave feature structure would house additional Obermeyer gates that can be adjusted to create a wave suited to public recreationists. The fixed crest grouted riprap section and sluice channel would be constructed between the wave feature and the right riverbank and designed to be aesthetically pleasing. A fish ladder would be constructed adjoining the left structure abutment to provide fish passage and would

be designed to incorporate fish passage for native fish species including bottom dwelling and weaker swimming species. The design would provide a more dependable and safe option to ensure irrigation delivery for the FUDC diversion and allow for fish passage and recreation opportunities for expert level users. The adjustable spillway crest gates would have the ability to lower and be flush with the streambed, providing better conveyance during high flow stages to more efficiently pass water, sediment, and debris. Pools would be excavated both upstream and downstream of the structure with associated armoring. Drop Structures 2 and 3: Two drop structures (drop structures 2 and 3) would be constructed downstream of drop structure 1. Drop structures 2 and 3 would consist of fixed crest classic U-drop structures. These structures would be designed to provide intermediate and beginner level recreation opportunities. Drop structures 2 and 3 would be approximately 20 feet wide and extend across the main river channel. Both structures would be constructed of boulders with all joints grouted to provide a stable structural section. Alternatively, these structures could be constructed with reinforced concrete with a rock pattern stamped on the concrete apron for aesthetics. A sheetpile wall would be installed below the structure and would tie into each bank. The sheetpile wall would provide structural stability to the banks. Pools would be excavated both upstream and downstream of each structure with associated armoring. Existing Side Channel: A side channel exists along the left bank that extends from the left bank at the existing push-up berm to approximately just upstream from proposed drop structure 3. This channel sees a low base flow throughout the year, but starts to become submerged as the river flows increase above 1,000 cfs. In order to maintain this side channel function, a gate structure and pipe would be installed west of the proposed new fish ladder at drop structure 1. The pipe would be routed to discharge at the upstream end of the side channel, maintaining flow to the channel. The design would allow more frequent sustained flow into the side channel than the current condition provides. A depression would be provided in drop structure 2 to allow flow to pass in the channel over this structure. This channel could flow year round and during high flow events the channel would become submerged as it does under existing conditions. Access Ramp 1: An access ramp would be constructed along the right bank downstream from drop structure 3. The ramp would consist of an approximately 30-foot-wide section with sloped stone steps to the river and provide safe and stabilized access for recreationists. Armoring would be required along the banks upstream and downstream of the ramp. Boulder Terrace: The steep and highly eroded right bank between proposed drop structures 1 and 3 would be stabilized by excavating the miscellaneous fill materials and stepping the banks at a more appropriate gradient. Boulders would be placed and secured in a tiered manner along the stepped bank. The boulders would be placed in steps with all joints fully grouted to provide a unified, stable structural section. Where required, steps would be attached to the back side of the boulders and embedded in the bank to provide additional pullout resistance. Select areas between boulders would be filled with soil and planted with trees and shrubs. Under the boulder terrace a sheetpile wall would be installed to provide additional stability along this section. The boulder terrace is designed to be a spillway section to accommodate flows entering back into the river at this point. At flows above 7,000 cfs floodwaters expand on the BPR managed lands and enter back into the river along the boulder terrace stretch. The boulder terrace provides erosion protection at

Reach 3 this bend in the river, a stabilized spillway section for flows entering back into the river during flood stage (flows over 7,000 cfs), and an area for the public to sit and overlook this section of the river. Access Ramp 2: An approximately 130-foot length along the right bank of the river at the northern project extents consists of a non-vegetated sandy shoreline. A stone access ramp with stone revetment walls would be installed along this stretch to provide safe and stabilized access for recreationists. The ramp would be 12 feet wide at the top of the bank and widen to 40 feet wide at the bottom. Access Ramp 3: A stone access ramp would be installed in Veteran s Pond adjoining Access Ramp 2 from the Boise River. The ramp would be constructed as described for Access Ramp 2 above. Bridge Replacements: Two bridges adjoining Veteran s Park would be replaced to accommodate a new alignment of the Greenbelt path. One of the bridges crosses the Veteran s Pond outlet channel (Bridge 2) and the other the Farmer s Union Canal ditch return to the Boise River (Bridge 1). The two existing bridges would be realigned and/or widened to meet the BPR design standards. New spread footings and abutments would be constructed for the bridge replacements. Construction Sequencing Construction would take place over an approximate 9-month span starting in August of 2018 and completing in May of 2019. The proposed construction sequence for the J.A. and Kathryn Albertson Family Foundation is as follows: August 2018 Construction Mobilization. Greenbelt Traffic Closure. Install Temporary Erosion Control BMPs. Rerouted Greenbelt Alignment Around Veteran s Pond. Vegetation Clearing (Upland). Excavation of Banks in Reaches 1 and 2. Remove and Reconstruct Bridges 1, 2 and 3 (Dewater as Needed). Construct Control Building and Utilities for Drop Structure 1. September 2018 Excavate Side Channel in Reach 1. Native Riparian Vegetation Planting. Begin Construction on New Greenbelt Alignment. Install Cofferdam and Divert Boise River Flows to FUDC Irrigation Canal. Perform Fish Salvage in Dewatered Portions of the Boise River. October 2018 Construct Habitat Islands and Complete Side Channel in Reach 1.

Begin Construction of Drop Structures 1, 2, and 3 and Boulder Terrace. November 2018 Finish Drop Structures 2 and 3. Finish Control Building and Utilities for Drop Structure 1. January 2019 Construction of Access Ramps 1-3. February 2019 Finish Construction of Ramps 1-4. Finish Drop Structure 1 and Boulder Terrace. Remove Cofferdam and Direct Flow Back to the Boise River. Convert Existing Greenbelt Path into Pedestrian Path March 2019 Finish Conversion of Greenbelt Path to Pedestrian Path April 2019 Finish Construction of New Greenbelt Alignment Select Riparian Planting. Upland Landscaping and Irrigation. Install Fencing and Signage. May 2019 Complete Landscaping and Irrigation System. Remove BMPs. Open the Greenbelt. Construction Complete. Note: This estimated construction schedule is subject to change pending final design.

Block 19, 20, 27 and 28: Type and Quantity of Materials to be Discharged Below the OHWM or Wetlands and Associated Type and Quantity of Feature Side Channel / Islands Remove Concrete Abutment Table 1. s and Excavation/Fill Activities within Wetlands Wetland Excavation Area(SF) (CY) Permanent s Fill (CY) Forested 3,224 1064 158 24" Riprap Scrub-Shrub 358 82 41 Drop Structure 1 Forested 1,938 194 261 30" Riprap Drop Structure 2 Forested 2,124 350 665 30" Riprap Boulder Terrace Forested 1,884 1,100 612 Fill Type* Native material excavated from channel bottom 60" Riprap (410 CY) 27" Riprap (202 CY) Drop Structure 3 Forested 375 115 101 30" (101 CY) Access Ramp 1 Forested 534 23 18 Access Ramp 3 Forested 460 67 45 Bridge 1 Forested 211 16 40 36" Riprap (12 CY) 1 1/2" minus crushed rock (6 CY) 36" Riprap (35 CY) 1 1/2" minus crushed rock (10 CY) Concrete (20 CY) Native material (12 CY) Bridge 2 Forested 301 17 40 Concrete (20 CY) Native material (12 CY) Total Permanent Forested / Scrub-Shrub 11,409 3,028 1,981 - Temporary s Portadam 1 Scrub-Shrub 509 - - - Portadam 2 Scrub-Shrub 320 - - - Total Temporary *Riprap will be D50 Scrub-Shrub 829 0 0 -

Table 2. s and Excavation Fill Activities within the OHWM Feature Side Channel / Islands Water Area (SF) Linear Feet Excav. (CY) Permanent s Fill (CY) Boise River 9,806 390 578 303 24" Riprap Flow Deflector Boise River 1,657-196 74 30" Riprap Fill Type* Drop Structure 1 & 2 and Armoring Boise River 32,633 302 6,342 5,473 Drop 1 - Concrete (837 CY); 1 1/2" minus crushed rock (268 CY) Armoring - 60" Riprap (2,343 CY) Armoring - 36" Riprap (1710 CY) Drop 2 - Riprap (285 CY); 1 1/2" minus crushed rock (30 CY) Drop Structure 3 Boise River 7,405 81 1,304 1,126 30 " Riprap (733 CY) Riprap (356 CY) 1 1/2" minus crushed rock (37 CY) Access Ramp 1 Boise River 1,358 110 67 45 Access Ramp 2 Boise River 2,043 71 50 36 Access Ramp 3 Minor Channel Contouring Total Permanent Veteran's Pond 1,447 71 50 36 Boise River 48,253 550 2,323 - - Boise River/ Veteran's Pond *Riprap will be D50 Excav. = Excavation 36" Riprap (35 CY) 1 1/2" minus crushed rock (10 CY) 36" Riprap (28 CY) 36" Riprap (28 CY) 104,602 1,575 10,910 7,093 -