R E C L A M A T I O N Managing Water in the West

Transcription

1 R E C L A M A T I O N Managing Water in the West DESIGN FOLDER Mill Diversion Dam Oregon Water Management Assistance Program Little Butte Creek Watershed Fish Passage Program RBCC/FBFAT Southwest Oregon October 2006

2 Table of Contents INTRODUCTION 4 CRITERIA 4 EXISTING HYDROLOGY...5 EXISTING HYDRAULICS.6 STRUCTURAL STABILITY... 6 IMPROVEMENTS TO PROTECT FISH 7 Alternative #1 Rock Weir....7 Alternative #2 Concrete Weir... 8 Alternative #3 Rock Fishway Drop Alternative #4 Concrete Fishway Drop. 10 COSTS.10 FIGURES: Hydraulics 1. HEC-RAS Results Incipient Motion Structural 3. Hydrostatic Forces Rock bolt, Buoyancy, Overturning Force Cost Estimate 5. Total Cost Cross-Vane, Rock Weir Cross-Vane, Concrete Weir Rock/Concrete Fishway Drop Concrete Fishway Drop DRAWINGS EXISTING DRAWINGS 10. Fishway Plan 11. Fishway Longitudinal Section & Sections 12. Fishway Sections PROPOSED DRAWINGS All Alternatives 13. Location Map 2

3 14. Existing Site Plan Rock Weir Alternative 15. Site Plan, Cross-Vane, Rock Weir 16. Plan, Cross-Vane, Rock Weir 17. Profile and Sections, Cross-Vane, Rock Weir Concrete Weir Alternative 18. Site Plan, Cross-Vane, Concrete Weir 19. Plan, Cross-Vane, Concrete Weir 20. Profile and Sections, Concrete Weir Rock Fishway Drop Alternative 21. Site Plan, Rock Fishway 22. Plan, Rock Fishway 23. Profile and Sections, Rock Fishway Concrete Fishway Drop Alternative 24. Site Plan, Concrete Fishway 25. Plan, Concrete Fishway 26. Profile and Sections, Concrete Fishway. 3

4 INTRODUCTION Design and construction of a fish passage project was completed for Mill Dam on the Little Butte Creek, near Medford, OR, that allowed for fish passage in the fall of As per the recommendations of Dave Rosgen, the Rosgen type weir downstream of the dam was constructed without any anchors into the bedrock. A pool/weir drop style fish ladder on the right side of the dam was also constructed. The fish ladder was constructed with materials consisting of rock and grout. The weir downstream of the dam consisted of rock and gravels. The downstream weir provided backwatering to minimize the jump for fish that traveled up the fish ladder. A large storm event, late in November, 2005, lifted and carried away all gravels and cobbles immediately upstream of the weir. The uplift pressure then lifted the header rocks and carried them downstream a small distance. Late in December, 2005, an even larger storm event dramatically battered the Little Butte Creek drainage and the surrounding area leaving remnants of the weir. Some of the remnants of the weir were still in tact residing near the bank tie-in, while large boulders were wildly strung hundreds of feet downstream. Resulting from the breach of the weir, the water surface upstream of the weir dropped. As a result of the lowered water surface elevation, the last drop of the fish ladder fell out of the scope of NOAA s criteria. Resulting from the weir breach, different alternatives to improve fish passage over Mill Dam will be reviewed in this report. The report will cover criteria, existing hydrology, existing hydraulics, and structural integrity to show the proposed weir s ability to withstand breaching forces. CRITERIA The prior weir design had previously been approved and authorized by NOAA and ODFW. Fish passage criteria were considered in the designing process for the proposed alternatives which was obtained from two different sources. The first source is Anadromous Salmonid Passage Facility Guidelines and Criteria [Draft], National Marine Fisheries Service and Oregon Administrative Rules, Oregon Department of Fish and Wildlife, Division 412. For alternative # 1 Rock weir downstream of Mill Dam, the following criteria was considered: 1. Hydraulic drop across weirs =.5 ft (Juveniles) and 1.0 ft (adults) 2. Design fish passage flow 5 95 percent exceedance flows in stream 3. 2 deep jump pools downstream of drop Due to the approval of the previous design, the proposed elevations will be the same as the previous design. The weir will be located downstream approximately.5 feet from the previous location to utilize the deep jump pool just downstream. The final location will be field-located. 4

5 For alternative # 2 Concrete weir downstream of Mill Dam, the following criteria was considered: 1. Hydraulic drop across weirs =.5 ft (Juveniles) and 1.0 ft (adults) 2. Design fish passage flow 5 95 percent exceedance flows in stream 3. 2 deep jump pools downstream of drop Due to the approval of the previous design, the proposed elevations will be the same as the previous design. The weir will be located downstream approximately.5 feet from the previous location to utilize the deep jump pool just downstream. The final location will be field-located. The low-flow notch, from the upstream end of the fishway, will be duplicated at the thalweg of the channel to allow for passage at the 95% exceedance flow. Alternative # 3 Rock/concrete fishway drop: 1. EDF = [Gamma*Q*S] / A < for roughened channel 2. 2 ft deep jump pools downstream of drop 3. 2 feet per second transport channel velocities 4. Width to length ratios of 2:1 5. Design fish passage flow 5 95 percent exceedance flows in stream 6. Pool volume V = [Gamma*Q*H] / (4 ft-lb/s)/cft 7. Hydraulic drop across weirs =.5 ft (Juveniles) and 1.0 ft (adults) This alternative does not agree with criteria. The width to length ratios do not correlate to 2:1 and the hydraulic drop is approximately 1 ft, as opposed to.5 ft. To cut down cost, one additional drop is proposed at the downstream of the fishway, as opposed to two. The proposed fishway drop is located where the bedrock rises in elevation downstream of the existing downstream fishway drop. Alternative # 4 Steel weirs starting at the downstream end of the culvert and continuing downstream until all necessary drops are met to meet criteria. The following criterion was used: 1. EDF = [Gamma*Q*S] / A < for roughened channel 2. 2 ft deep jump pools downstream of drop 3. 2 feet per second transport channel velocities 4. Width to length ratios of 2:1 5. Design fish passage flow 5 95 percent exceedance flows in stream 6. Pool volume V = [Gamma*Q*H] / (4 ft-lb/s)/cft 7. Hydraulic drop across weirs =.5 ft (Juveniles) and 1.0 ft (adults) This alternative does not agree with criteria. The width to length ratios do not correlate to 2:1 and the hydraulic drop is approximately 1 ft, as opposed to.5 ft. To cut down cost, one additional drop is proposed at the downstream of the fishway, as opposed to two. The proposed fishway drop is located where the bedrock rises in elevation downstream of the existing downstream fishway drop. EXISTING HYDROLOGY Existing Little Butte Creek hydrology differs, depending on the source. Developing new hydrology may add more discrepancies to the already debatable hydrology. With that thought in mind, no new synthesized hydrology will be developed. 5

6 The following are results from hydrologic analyses conducted from different sources and peak flow recordings: Hydromet Gage downstream from Mill Dam at the Crater Lake Highway Bridge near Eagle Point, OR: Recorded flows of cfs and a corresponding gage height of 5.77 feet, and a recorded flow of cfs with a corresponding gage height of 8.27, indicated the gage height values differed largely. The gage has limited historical data, less than ten years and the datam has been re-established more than once. Oregon Water Masters from District s 13 and 14 had stated a report had been released containing flood event values. The report was developed from an individual that no longer works in the Water Master s office, thus they were unable to locate the report. The Water Master mentioned the report was sent to Reclamation. Personnel within Reclamation, with access to the report, were on annual leave for the week of Oct. 2. The report will be reviewed post October 10 th. Reclamation: Generated from Little Butte Gage (# ). The gage was not operating when large flood events occurred, thus the high points on the hydrograph are not recorded in the historical data. Q5% Q95% Q Low Flow Q25 Q50 Q100 (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) In conversation, results of ODOT s hydrologic analysis for the Crater Lake Highway bridge, near Eagle Point was discussed. It was brought to my attention the 100 year flood event resulted in a magnitude of close to 12,000 cfs. EXISTING HYDRAULICS Existing channel hydraulics was analyzed with HEC-RAS, a Corps of Engineers modeling tool prior to completion of the prior weir design. Results from the HEC-RAS runs were used to analyze incipient motion. Existing HEC-RAS results are located on Figure 1. Incipient motion results are located on Figure 2 at the end of the report. STRUCTURAL INTEGRITY Analyzing the different alternatives for structural integrity can be approached in different ways. Different procedures that were approached included the following: Hydrostatic pressure, including velocity head - Active force from the pressure distribution acting on the weir was calculated. The active force was multiplied by a factor of 2 for added safety. The resulting passive moment was calculated and was acting at the downstream edge of the boulder, where the boulder makes contact with the bedrock. The passive force from the pressure distribution was also calculated. The passive moment was calculated and was acting at the same point as the passive moment. The difference of the two moments is the moment 6

7 that needs to be resisted. In order to resist the moment, rock bolts were analyzed as a resisting force. Results from the rock bolt analysis concluded the rock bolt capacity needed is 1520 lbs due to hydrostatic pressure. The Williams Anchor 5/8 inch diameter Mechanical anchor bolts have a capacity of 13,550 lbs for the recommended design load, more than enough to resist the hydrostatic forces on the boulders (See Figures 3 and 4). Incipient motion calculations, as noted above - Incipient motion calculations are not meant for cross-vanes, in particular, because the velocity vectors are not parallel with flow 100% of the time. Due to the discrepancies with the application of incipient motion in this case, a large safety factor would be added to the diameter of the boulder. Specialists from Reclamation assisted with the incipient motion calculations. Results from incipient motion calculations conclude a 3.7 feet diameter boulder is required to resist boulder movement, without boulder anchorage. Applying a 150% safety factor for impact and discrepancy for application, the boulder diameter results in 5.5ft (See Figure 2). Buoyant Force Resistance The buoyant force required to float a 4x3x2 feet boulder was calculated. The force resulted in approximately 2550 lbs. The rock bolt capacity of one bolt is 13,500 lbs, enough capacity to resist buoyant forces (See Figure 4). Impact from floating debris The force required to tear the anchors from the bedrock was calculated. The calculations included assuming a conservative height of the boulder of 3 feet. The impact force would act on the boulder at the upstream top corner, causing an overturning moment at the downstream edge of the boulder, where the boulder meets the bedrock. The rock bolt capacity of 13,500 lbs was used to calculate a boulder stabilizing moment. The force required to uproot the anchored boulder resulted in 13,500 lbs (See Figure 4). Moment stability analysis The boulder weight underwater acts at the centric of the boulder and normal to the creek bed. The assumption was made that an overturning force acts at the top of the boulder for the worst-case scenario. Assuming the boulder would roll about a point located on the downstream, bottom corner of the rock, a moment stability analysis was conducted. The force required to topple the boulder, if no anchor bolts are installed is approximately 1900 lbs. The calculation assumes a 4x3x2 feet boulder (See Figure 4). IMPROVEMENTS TO PROTECT FISH Description Alternative #1 Rock Weir Alternative #1 includes constructing a proposed rock weir approximately 6 inches downstream of the prior rock weir location to utilize the downstream pool for fish passage. Construction procedures for the weir include: Construct a ramp to enter streambed from the south side of the riverbank. The river will be entered from private property, just east of the Eagle Point boundary. The weir layout will be marked. The bedrock within the layout area will be sawcut and jack-hammered 6 inches in depth. 7

8 Boulders used for the weir will be drilled from atop the flood plain. The minimum diameter size drill bit that can go 4+ feet deep is 1-5/8inches, according to A CORE in Boise, ID. There will be two holes drilled in each boulder, from top to bottom. The boulders will be set in place, within the excavated layout area. Using the pre-drilled holes in the boulders, as a guide, the bedrock will be penetrated to a depth of 2 feet. Post drilling, 5/8 diameter mechanical anchors will be set at each hole, and torque to a capacity of 125 ft-lbs to ensure shell expansion. A water compatible epoxy, mixed with sand, will be injected in the open space between the mechanical anchor and the circumference of the drill hole through a hole drilled in the washer at the top of the rock. Each bolt will be examined to determine the length of the bolt beyond the nut. The bolt will be sheared off at the top of the nut. A grout cap will be placed over the top of the nut and bolt assembly to assure fish friendliness. Creek bed material will be placed upstream of the weir at a 5:1 slope. The gradation will be such that the D84 is 1.5 ft. The material will be well-graded, with 10% fines. Advantages Disadvantages Improved fish passage is obtained. Aggredation to the channel slopes, downstream of the weir, is obtained by channeling flow at the center of the channel. Weir will withstand large forces. If boulders from prior weir can be salvaged, material costs will be minimal. Elevations have been set prior, thus less cost for design and hydraulic analysis. Aesthetically pleasing, natural look The possibility of boulder cracking is apparent, due to drilling, if the boulder is fractured. Description Alternative #2 Concrete Weir Alternative #2 includes constructing a proposed concrete weir approximately 6 downstream of the prior rock weir location to utilize the downstream pool for fish passage. Construction procedures for the weir include: Construct a ramp to enter streambed from the south side of the riverbank. The river will be entered from private property, just east of the Eagle Point boundary. The weir layout will be marked. The bedrock within the layout area will be sawcut and jack-hammered 6 inches in depth. The bedrock will be penetrated to a depth of 2 feet. The remaining length of the rock bolt will be utilized as structural steel. 8

9 Post drilling, 5/8 diameter mechanical anchors will be set at each hole, and torque to a capacity of 125 ft-lbs to ensure shell expansion. Forms will be constructed and concrete poured to complete the concrete weir. Advantages Disadvantages Improved fish passage is obtained. Aggredation to the channel slopes, downstream of the weir, is obtained by channeling flow at the center of the channel. Weir will withstand large forces. Elevations have been set prior, thus less cost for design and hydraulic analysis. Larger cost than boulder weir Aesthetically not natural Description Alternative #3 Rock Fishway Drop Alternative #3 includes constructing a rock/concrete wall, approximately 12 feet downstream of the existing downstream fishway drop. The application of the wall is a fish weir. The wall will consist of a concrete base. After the concrete wall is constructed, boulders will be placed on top to give a more natural look. Construction procedures for the weir include: Construct a ramp to enter streambed from the south side of the riverbank. The river will be entered from private property, just east of the Eagle Point boundary. A coffer dam will be constructed around the proposed fishway drop location in order to drill the bedrock and place the anchors and place the concrete in the dry. The weir layout will be marked. The bedrock within the layout area will be sawcut and jack-hammered 6 inches in depth. The bedrock will be penetrated to a depth of 2 feet at 18 inch centers. Mechanical anchors will be set and nuts placed. Forms will be constructed and the wall placed. Boulders used for the weir will be drilled from atop the flood plain. There will be two holes drilled in each boulder, from top to bottom. The hole-placement, in the boulders, will coincide with the previously placed anchor-spacing. Two drill holes in the boulders is required for boulder stability. Post drilling, 5/8 diameter mechanical anchors will be set at each hole, and torqued to a capacity of 125 ft-lbs to ensure shell expansion. A water compatible epoxy, mixed with sand, will be injected in the open space between the mechanical anchor and the circumference of the drill hole through a hole drilled in the washer at the top of the rock. 9

10 Each bolt will be examined to determine the length of the bolt beyond the nut. The bolt will be sheared off at the top of the nut. A grout cap will be placed over the top of the nut and bolt assembly to assure fish friendliness. Advantages Disadvantages Improved fish passage is obtained. If boulders from prior weir can be salvaged, material costs will be minimal. Natural look. Difficult to place coffer dam. Difficult to place rocks. Description Alternative #4 Concrete Fishway Drop Alternative #4 includes constructing a concrete wall, approximately 12 feet downstream of the existing downstream fishway drop. The application of the wall is a fish weir. Construction procedures for the weir include: Construct a ramp to enter streambed from the south side of the riverbank. The river will be entered from private property, just east of the Eagle Point boundary. A coffer dam will be constructed around the proposed fishway drop location in order to drill the bedrock and place the anchors and place the concrete in the dry. The weir layout will be marked. The bedrock within the layout area will be sawcut and jack-hammered 6 inches in depth. The bedrock will be penetrated to a depth of 2 feet at 18 inch centers. Mechanical anchors will be set and nuts placed. Forms will be constructed and the wall placed. Advantages Disadvantages Improved fish passage is obtained. Less detailed work with absence of boulders Difficult to place coffer dam Possibly aesthetically displeasing. COST See Figures 5, 6, 7, 8, and 9 for all alternative costs. 10

11 HEC-RAS RESULTS FIGURE 1. HEC-RAS results. Cross section number 4 is taken at the same location as the proposed weir. 11

12 INCIPIENT MOTION FIGURE 2. Incipient Motion Calculations. 12

13 WEIR HYDROSTATIC FORCES FIGURE 3. Resulting hydrostatic forces on weir rock. 13

14 ROCKBOLT, BUOYANCY, OVERTURNING FORCE FIGURE 4. Different analysis to determine rock stability. 14

15 TOTAL COST FIGURE 5. Total cost includes unlisted items and contingency. 15

16 CROSS-VANE ROCK WEIR FIGURE 6. Cost estimate for listed items only. 16

17 CROSS-VANE CONCRETE WEIR FIGURE 7. Cost estimate for listed items only. 17

18 ROCK/CONCRETE FISHWAY DROP FIGURE 8. Cost estimate for listed items only. 18

19 CONCRETE FISHWAY DROP FIGURE 9. Cost estimate for listed items only. 19