McCoy-Linn Dam Removal
Gleim
Environmental Group has been chosen as the contractor to remove the McCoy-Linn
Dam, located between Bellefonte and Milesburg on Spring Creek. URS is the
project engineer and is providing construction management.
Objectives of this PA Fish & Boat Commission and ClearWater Conservancy project are to restore stream habitat, natural biodiversity, and ecosystem function; improve water quality; decrease trapped sediment to augment the stream channel and floodplain; restore stream and riparian habitat; eliminate invasive species; preserve, create, and enhance public space and access; provide educational opportunities on the benefits of dam removal; and eliminate a public safety hazard to water recreation such as fishing, canoeing, and kayaking.
Water Quality Sampling of Spring Creek (from Geoff Smith, Water Resources Coordinator for the Spring Creek Water Resources Monitoring Project)
Relatively little is known about the instantaneous impacts of a dam removal on water quality. The McCoy-Linn Dam is being monitored (before, during, and after) to collect data and for review and use in later dam removal projects. Throughout the duration of the project, automated samplers will be in place sampling water both upstream and downstream of the project at various times around the clock.
Besides the obvious sediment plume that is created, compounds may also be bound to the sediment based on their physical and chemical properties and “hitch a ride” with the re-suspended sediment. It is also believed that other materials, once locked up, may become soluble again and dissolve back into the water.
Analysis of samples from the sediment behind the dam have shown little in the way of harmful compounds that could behave in this fashion, but without water collection and testing there is may be some level of doubt. A suite of metals and nutrient analyses will be conducted on these samples, as well as physical measurements such as turbidity and total suspended solids (TSS), consistent with normal sampling of the Spring Creek Water Resources Monitoring Project.
Unfortunately, these analyses take time and will not be reportable on a daily basis with all the other updates. These data will not only be useful for determining the effects of the removal of the McCoy-Linn Dam on Spring Creek but could be used for planning and decision making for other similar projects.
Dam Removal Updates (from URS)
September 14, 2007
Work Completed
the week of September 14 (5th week of work):
Crossed over creek to left bank (far side from road) with long reach excavator and graded stream bank beginning at approximately 1450’ upstream of the former dam. Also removed two large clay deposits from the middle of the stream; Seeded and mulched the upper 1000’ of the graded left bank area; Performed additional demolition of concrete from the former dam on both banks; Moved additional silty material (muck) from upstream of the former dam, rock from the core of the dam, and gravel into the former canal area; Separated concrete dam rubble from other material and began breaking into appropriate-sized pieces for bank stabilization. As part of this process, rebar in the concrete was removed or cut flush; Built the new left bank in the area downstream of the former dam. Gravel captured in the coffer dams was placed at the toe of the walls and stabilized with rubble from the dam; A handful of juvenile and adult trout were accidentally scooped up in the excavator bucket from just below the former dam while removing gravel captured in the coffer dams. These trout were retrieved by hand and returned to the water. They appeared fat and healthy, and show that trout have remained in the area of the dam throughout the project; The current stream channel is now down to the original, pre-dam streambed, as evidenced by cobble-sized rocks in the streambed. These rocks will provide important habitat in the restored stream for aquatic insects and other organisms, which are the primary food resources for brown trout in Spring Creek.
Work projected for next week:
Complete right stream bank and floodplain grading of the lower 450’ upstream of the former dam. This is the final section of stream bank grading upstream of the dam; Build the right stream bank downstream of the dam and stabilize with concrete rubble; Stabilize additional streambank areas as appropriate with concrete rubble; Seed and mulch remaining disturbed areas and install erosion-control matting on stream banks.
September 5, 2007
Work Completed Wednesday:
Continued shaping stream channel to appropriate dimensions from approx. 600 feet to 300 feet upstream of the former dam on the right bank (looking downstream; Completed final grading of upstream floodplain from 600 feet upstream of dam down to 300 feet upstream of dam; Excavated additional sediment from the right bank floodplain from 350 feet to 150 feet upstream of the former dam.
Work Projected Tomorrow:
The entire project area on the right bank of the stream will be hydro-seeded and mulched from the road down to the stream bank from the upstream limit of the project down to approx. 500 feet upstream of dam; Grading will continue from 300 feet upstream of the dam down to the dam; The remaining 1.5 feet of the dam will be removed and the final breach dimension widened; Miscellaneous activities may include grading in the former canal and cutting metal (rebar) from dam debris so that it can be used for downstream bank stabilization.
Project Schedule (Total Project expected 4-6 weeks)
After 17 working days, the project is on schedule.
September 4, 2007
Work Completed Tuesday:
Continued shaping stream channel to appropriate dimensions from approx. 600 feet to 500 feet upstream of the former dam on the right bank (looking downstream); Completed final grading of upstream floodplain from 1600 feet upstream of dam down to 600 feet upstream of dam; Excavated additional sediment from the right bank floodplain from 550 feet to 350 feet upstream of the former dam.
Work Projected Tomorrow:
Work will resume to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain, and area adjacent to floodplain to approx. 200 feet upstream of dam.
Project Schedule (Total Project expected 4-6 weeks)
After 16 working days, the project is on schedule. No work was completed on Monday due to the Labor Day holiday.
August 31, 2007
Work Completed Friday:
Continued shaping stream channel to appropriate width from approx. 750 feet to 600 feet upstream of the former dam on the right bank (looking downstream); Excavated additional sediment from the right bank floodplain from 750 feet to 550 feet upstream of the former dam; Removed accumulated gravel trapped in coffer dams immediately downstream of dam. Very little gravel was found as expected.
Work Projected Next Week:
Work will resume to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain, and area adjacent to floodplain. Goal will be to reach the dam area by the end of next week; Install erosion control matting, seed, and mulch along right bank from 1450 feet to point where final grading is complete.
Project Schedule (Total Project expected 4-6 weeks)
After 15 working days, the project is on schedule.
August 29 and 30, 2007
Work Completed Wednesday and Thursday:
Continued to final grade the stream channel and floodplain starting approx. 1400 feet upstream of the former dam on the right bank (looking downstream) down to approx. 750 feet upstream of the dam; Received a total of 7 loads of large rock for streambank stabilization. This caused temporary backup of traffic as the rock delivery trucks maneuvered to their dump points along SR 144. Traffic was managed by the contractor. Large rock is placed in the new streambank to help provide stability to the bank.
Work Projected Tomorrow (8/31)
Remove captured sediment from cofferdam, and store on-site; Work will resume to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain, and area adjacent to floodplain.
P
roject Schedule (Total Project expected 4-6 weeks)After 14 working days, the project is on schedule, and grading upstream of the dam should be completed next week, and the entire area will be seeded next week, barring weather delays.
Photos from Katie Ombalski
August 27 and 28, 2007
Work Completed Monday and Tuesday:
Excavated sediment captured in downstream cofferdams three times. Removed approx. 100 cubic yards of sediment that was captured in the cofferdams, and stored on site for future use in grading. Most of the sand and gravel mobilized during the dam removal has now been captured in the cofferdams, removed and placed as fill on site where needed. The cofferdams have been very successful in capturing sand and gravel. The stream remains turbid during the active work due to very fine-grained suspended sediment in the water.
Demolished additional portions of dam including lowering the main breach from the emergency spillway on the left bank to roughly the center of the dam down to el. 702’ (about 10 feet below original dam crest).
Began to final grade the stream channel and floodplain starting at the upstream limit of the project approx. 1450 feet upstream of the former dam on the right bank (looking downstream). Completed final grading downstream for approx. 30 feet on Monday, and another 50 feet on Tuesday am, before one of the excavators got stuck in the mud and stopped work. The excavator got stuck about 300 feet upstream of the dam, and was not stuck in the stream, nor did this cause any mud or sediment to enter the stream. It is not unusual on dam removal projects for equipment to occasionally become stuck, and this project is not an exception.
Received several loads of large rock for streambank stabilization. This caused temporary backup of traffic as the rock delivery trucks maneuvered to their dump points along SR 144. Traffic was managed by the contractor.
Work Projected Tomorrow (8/29):
Remove captured sediment from cofferdam, and store on-site; Work will resume to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain, and area adjacent to floodplain; Slightly widen dam breach, and remove additional portions of dam; Continue to manage "trash" uncovered during sediment excavation; Control sediment mobilization within Spring Creek through phased breach and construction of rock berm downstream of dam.
Project Schedule (Total Project expected 4-6 weeks)
After 12 working days, the project is ahead of schedule. While the equipment getting stuck lost us a half day, the project is still several days ahead of schedule. Barring any further delays, the channel and floodplain grading will continue through the end of this week, and should be close to being finished in the portion upstream of the dam by the end of the week.
August 24, 2007
August 22, 2007
Work Completed Monday and Tuesday:
Monitored rainfall and stream level, as well as larger weather patterns including hurricanes and tropical storms in the event that precautions for high flows were needed. No conditions materialized that resulted in significant increases in water levels in Spring Creek; Excavated sediment captured in downstream cofferdams three times. Removed approx. 300 cubic yards of sediment that was captured in the cofferdams, and stored on site for future use in grading;
Demolished additional portions of dam including lowering the main breach from the emergency spillway on the left bank to roughly the center of the dam down to el. 703’ (about 9 feet below original dam crest). This lowered the water surface of the impoundment by approximately 6 - 7 feet below the initial level; Continued to monitor stream turbidity in downstream Milesburg. Since it was raining both days, observations made include that Bald Eagle Creek at the confluence in Milesburg was nearly as turned from the rainfall as Spring Creek was from the dam removal; Completed significant grading of the sediment from the upstream impoundment, including digging and rough shaping the new stream channel for a distance of approximately 1000 feet upstream of the dam. This included using specially designed "mats" and a long reach excavator to limit sediment disturbance and eliminate the need for any equipment to enter the water upstream of the dam; Reconstructed the cofferdams, and "rough-built" the new streambanks downstream of the dam by placing large rock and rubble along the alignment of the future streambanks; Increased the size of the downstream cofferdam to capture more sediment; Performed site stabilization in anticipation of potential thunderstorms prior to leaving site for the day; Collected timbers, tires, metal, and other large items for disposal off-site at licensed facilities; Posted informational sign for public providing web address to access these reports.Work Projected Tomorrow:
Remove captured sediment from cofferdam, and store on-site; Continue to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain and area adjacent to floodplain; Slightly widen dam breach, and remove additional portions of dam; Continue to manage "trash" uncovered during sediment excavation; Control sediment mobilization within Spring Creek through phased breach and construction of rock berm downstream of dam.
Project Schedule (Total Project expected 4-6 weeks)
After 7 working days, the project is ahead of schedule. Rain was not significant enough to delay progress on Monday or Tuesday, but it sure made everyone very soggy. Barring any delays the rest of the week, we project to be completed with the main dam removal work this week, and will continue to work on excavating sediment from the former impoundment and developing a new stable stream channel. That work will continue into next week.
August 21, 2007
Monitored rainfall and stream level, as well as larger weather patterns including hurricanes and tropical storms in the event that precautions for high flows were needed. No conditions materialized that resulted in significant increases in water levels in Spring Creek; Excavated sediment captured in downstream cofferdams three times. Removed approx. 300 cubic yards of sediment that was captured in the cofferdams, and stored on site for future use in grading; Demolished additional portions of dam including lowering the main breach from the emergency spillway on the left bank to roughly the center of the dam down to el. 703’ (about 9 feet below original dam crest). This lowered the water surface of the impoundment by approximately 6 - 7 feet below the initial level; Continued to monitor stream turbidity in downstream Milesburg. Since it was raining both days, observations made include that Bald Eagle Creek at the confluence in Milesburg was nearly as turned from the rainfall as Spring Creek was from the dam removal; Completed significant grading of the sediment from the upstream impoundment, including digging and rough shaping the new stream channel for a distance of approximately 1000 feet upstream of the dam. This included using specially designed "mats" and a long reach excavator to limit sediment disturbance and eliminate the need for any equipment to enter the water upstream of the dam; Reconstructed the cofferdams, and "rough-built" the new streambanks downstream of the dam by placing large rock and rubble along the alignment of the future streambanks; Increased the size of the downstream cofferdam to capture more sediment; Performed site stabilization in anticipation of potential thunderstorms prior to leaving site for the day; Collected timbers, tires, metal, and other large items for disposal off-site at licensed facilities; Posted informational sign for public providing web address to access these reports.Work Completed Today (Monday and Tuesday):
Work Projected Tomorrow:
Remove captured sediment from cofferdam, and store on-site; Continue to grade new stream channel upstream of dam and remove sediment from the new stream channel using the long reach excavator. This sediment will be graded back away from the stream to help create new streambanks, floodplain and area adjacent to floodplain; Slightly widen dam breach, and remove additional portions of dam; Continue to manage "trash" uncovered during sediment excavation; Control sediment mobilization within Spring Creek through phased breach and construction of rock berm downstream of dam.
Project Schedule (Total Project expected 4-6 weeks):
After 7 working days, the project is ahead of schedule. Rain was not significant enough to delay progress on Monday or Tuesday, but it sure made everyone very soggy. Barring any delays the rest of the week, we project to be completed with the main dam removal work this week, and will continue to work on excavating sediment from the former impoundment and developing a new stable stream channel. That work will continue into next week.
August 16, 2007
Conducted site safety meeting; Nearly completed demolition of generating station. Removed steel rebar from rubble from generating station. Steel rebar is being stockpiled for removal from site for recycling; Received 2 loads each of R-4 (coarse) rock and 2A stone to complete access roads and stabilize access points so that erosion and sedimentation related to access is limited;
Completed additional removal of the dam at the initial breach area along the left side (looking downstream). The breach was lowered to elevation 708 (4 feet of the dam was removed) over a length of about 35 feet along the left side. This lowered the water surface of the impoundment by an additional 1 foot from the start of the day. Work was stopped several times during this process to keep the stream from becoming too turbid; Began to construct downstream rock cofferdam to help capture coarse-grained sediment moving through the water flowing through the dam breach. This cofferdam is not capable of capturing the very fine-grained grey silt, which will continue to make the stream appear cloudy while work is going on in this area; Limited sediment mobilization through breach phasing and periodically monitoring stream turbidity at three points downstream from the dam site to Bald Eagle Creek in Milesburg; Performed site stabilization in anticipation of potential thunderstorms prior to leaving site for the day.Work Projected Tomorrow:
Survey the dam and the breached area; Complete first phase of dam removal by lowering left section of dam by 2 more feet, which will lower the water level another 1.5 to 2 feet. By lowering the water upstream of the dam to this level, the sediment in the impoundment will be exposed and dry so that removal of that can begin; Place removed sediment in temporary berms on-site until final grading begins in 5-7 days; Remove top 2-3 feet from remainder of dam; Complete construction of rock cofferdam downstream of dam; Control sediment mobilization within Spring Creek through phased breach and construction of rock cofferdam downstream of dam; Diverted all flow to left bank diversion channel upstream of dam by building earthen diversion berm.
Project Schedule (Total Project expected 4-6 weeks):
After 4 days, project is ahead of schedule. Will work short day Friday due to being ahead of schedule and additional equipment needed to continue not being delivered to site until Monday. Specialty work platforms (equipment mats) were brought on-site so that equipment can work in soft mud. Long reach excavator to be delivered on Monday next week to provide additional ability to reach impounded sediment from greater distance to avoid too much equipment tracking in muddy conditions.
Friday and next week will begin initial phase of sediment removal. This will go on for a number of days and will result in rough shaping of the first 400-600 feet of the new stream channel upstream from the dam. This work will be completed in a contained area so that equipment is not working in Spring Creek and sediment mobilization is minimized. All sediment will be used on site for grading, and will not be taken off-site.
August 15, 2007
Conducted site safety meeting; Performed additional demolition of generating station; Continued to build and improve access for on-road truck access; Demolished additional portions of dam including lowering yesterday’s breach in the emergency spillway and widening this breach to include about ¼ of dam crest to el. 708’ (about 3 feet below original dam crest). This lowered the water surface of the impoundment by approximately 2.5 feet below the initial level; Limited sediment mobilization through breach phasing and monitoring stream turbidity in downstream Milesburg; Performed site stabilization in anticipation of potential thunderstorms prior to leaving site for the day.
Work Projected Tomorrow:
Complete first phase of dam breach by lowering left section of dam by 2 more feet, which will lower the water level another 1.5 to 2 feet; Finish stabilizing access roads and stream access with rock; Control sediment mobilization within Spring Creek through phased breach and construction of rock berm downstream of dam.
August 14, 2007
Conducted site safety meeting; Demolished above grade portion of generating station; Continued to build and improve access; Completed initial breach of emergency spillway to el. 709 to begin dewatering impoundment; Improved security around site; Segregated waste materials from building demolition for proper disposal; Limited sediment mobilization through breach phasing and monitoring stream turbidity
Work Projected Tomorrow:
Remove remaining portions of generating station; Remove sediment from immediately upstream of dam in breach area; Remove remaining portions of spillway and left side of dam to draw down water level 2-3 feet; Finish stabilizing access roads with rock; Control sediment mobilization through phased breach and construction of rock berm downstream of dam
August 13, 2007 - Removal begins
Photos courtesy of Bob Donaldson.
For more information about the McCoy-Linn Dam removal, please contact project manager Katie Ombalski at (814) 237-0400 or katie@clearwaterconservancy.org.