Davis Brook CSO Storage Tank
Work completed 9/21/20 to 9/25/20
S.E. MacMillan had a crew of 19 on site this week. Working on wall placement #2, they finished tying reinforcement steel, building and mounting the first weir bond-out, standing concrete framework, connecting form ties, plumbing the formwork with bracing, and erecting form-top scaffolding. Concrete pump trucks are currently in high demand locally and MacMillan had intended to make the wall placement on Thursday but could not get a pump truck until Friday. Mainely Concrete Pumping set up at 7:30 a.m., two S.W. Cole technicians were on site at 8:00 a.m. for concrete batch testing, and Hughes Brothers delivered the first batch of concrete at 8:30 a.m. They tested, pumped, and placed 244 cubic yards, or about 45 cubic yards an hour, and finished at 4:00 p.m. Eddy Hughes was on site observing quality control. Friday was his last day at Hughes Brothers; he is retiring after more than 40 years overseeing more than two million yards of batched an delivered concrete.
H.B. Fleming had a crew of five on site this week. They welded interior corner bracing against the southwest and northwest shoring walls. They also installed threaded corner tensioners in both locations which act as an opposing tensioned force through the shoring wall and connected to wailers on the box wall and the ramp walls.
Work completed 9/14/20 to 9/18/20
H.B. Fleming had five men on site this week. They welded wailers in the southwest shoring corner between soldier pile SP#14W to SP#1W, and they welded into place two upper inside corner braces. They also welded wailers between soldier pile, from #20W to #31W.
S.E. MacMillan had a crew of 19 on site this week. They stripped some formwork from last week's wall placement #1 and began tying reinforcement steel and standing gang forms for wall placement #2. With favorable dry weather conditions in place, they split the crew and began removal and replacement of two sluice gates which control the sewer flow at the intersection of the 48" RCP Penobscot Interceptor and the Davis Brook 8'x9' CSO box culvert conduit. On Tuesday, MacMillan set up five 6", three-phase electric pumps for bypass pumping. On Wednesday, they removed the frame and gate for the 42" Davis Brook conduit and installed the new 42" frame and gate. On Thursday, they removed the gate for the 48" Penobscot Interceptor. At a later date, they will continue removal of the 48" Penobscot Interceptor frame, installation of the new 48" frame and gate, and installation of new actuators for both gates.
Work completed 9/7/20 to 9/11/20
S.E. MacMillan had a crew of 15 on site for the short Labor Day holiday week. They completed the formwork and reinforcement steel for wall placement #1, located in the southeast corner of the Tank and on foundation slab #5. On Thursday, N.S. Giles' pump truck set up at 6:00 a.m., along with two concrete testing technicians from S.W. Cole. O.J. Folsom delivered 210 cubic yards of concrete between 7:15 a.m. and 1:00 p.m. and Giles pumped the concrete into the forms. Each concrete truck was tested for air, slump and test cylinders were cast for later compressive strength testing. MacMillan placed the pumped concrete into the forms in 4-5' lifts, vibrating each successive lift together. The wall placement was 3' thick and just over 24' high. There are 14 more 3'-thick, 24'-high Tank wall placements. MacMillan plans on continuing with Tank wall placements until cold weather concreting is necessary, and then they will switch back to placing foundation slabs through the winter. MacMillan also began the process of removing and replacing the 48" and 42" slide gates in the gate chamber on the southern end of the project.
H.B. Fleming had a crew of three on site this week. They completed threading and driving sheet pile into place and closed the shoring box for the Tank in the northwest corner. They began welding wailer bracing between soldier piles and installed wailers from SP#20W to #14W.
Work completed 8/31/20 to 9/4/20
S.E. MacMillan had a crew of 14 on site this week. They completed standing/closing the wall form panels for wall placement #1, which is scheduled for Wednesday, 9/9/20. They worked on installing form ties, wailer braces, and construction joint bulkheads, and they tied reinforcement steel for wall connection to the top slab. They began excavating to elevation 0.00 in the southeast shoring corner so Fleming can install wall wailers next week.
H.B. Fleming had a crew of two on site this week. They spent two days moving drilling equipment off site, organizing their work space, and taking delivery of sheet pile. They drove sheets about 100 linear feet, from soldier pile #24W to #38W. #38W is on the northwest corner of the shoring system. They have approximately 40' to close the entire sheet pile shoring system. They expect to close early next week and then begin installing wailers and raker braces.
Work completed 8/24/20 to 8/28/20
S.E. MacMillan had a crew of 14 on site this week. MacMillan took delivery of a Meva wall form system and another delivery of reinforcement steel. They tied 19.5 tons of reinforcement steel in place for wall section #1. They set the first two sections of gang forms on the outside wall face of the southeast tank corner. They expect to make the first wall placement next week.
H.B. Fleming had a crew of three workers on site. They drilled in the final casing and determined that the bedrock depth had fallen off enough that another soldier pile was not necessary. They spent a couple of days loading out miscellaneous tools, casing, steel, and equipment. On Thursday, they brought the vibro-hammer back to the site and began driving sheet pile against the soldier piles. They drove approximately 80 linear feet of sheets to bedrock or refusal, from soldier pile #9W to #24W.
Work completed 8/17/20 to 8/21/20
H.B. Fleming had four workers on site this week: two worked days, and two worked nights. The night crew predominantly drilled soldier pile sockets into bedrock. The day crew drilled and set casing into place for #36W, #37W, #38W, and #39W piles. Three days this week, Fleming placed Hughes Brothers' concrete for setting soldier piles #36W to #39W. With #37W pile, Fleming completed the west side soldier pile line, and also turned the corner and set two piles on the northwest shoring line. They have one more soldier pile to set near the northwest ramp wall. On Thursday, they removed the upper corner brace in the southeast shoring wall, which allowed MacMillan to start tying vertical wall reinforcement steel.
S.E. MacMillan had 14 workers on site this week. They transitioned from excavating, forming, and tying steel for foundation slab placements, to starting work on concrete wall construction. They spent four days moving, cleaning, and organizing slab formwork and related materials to a lay down area on the south end of the site. They excavated a 30'x70' Tank section about six feet deeper (to +/- el. -3.00) just north of the north ramp wall. This gives them a lower platform for better crane pick radius. On Thursday, they tied all the horizontal steel they could reach for the first wall section. On Friday, they started tying the 22.5' tall vertical bars for the exterior face of the wall over slab section #5.
Work completed 8/10/10 to 8/14/10
S.E. MacMillan had 14 workers on site this week. They completed tying the steel for the southeast Tank corner, slab section #5. They built and installed starter wall forms for the full height Tank walls and secured water stop in place for all construction joints. On Thursday, N.S. Giles' pump truck and S.W. Cole testing technicians arrived on site at 4:30 a.m. and set up slab placement #5. Hughes Brothers delivered 216 cubic yards of concrete, N.S. Giles pumped it into place, and MacMillan finished it with mag floats and steel trowels. On Friday morning, SEM stripped the form panels. N.S. Giles arrived at 9:30 a.m. and Hughes Brothers brought fill concrete to be pumped into the space between the new foundation slab and the shoring wall. MacMillan used about 40 cubic yards to fill the slab-to-shoring gap. The entire east shoring wall is securely pinned between the Tank slab, fill concrete, and undisturbed earth. Ground water is evident in the Tank excavation but not to the extent to which it was expected. SEM has six 3" electric pumps set in deep sumps and they are easily handling the groundwater. Next week MacMillan will transition to ganging together panel forms, tying wall steel, and placing the full height Tank walls onto the five east-side slab sections they have in place.
H.B. Fleming is still running a two-man day crew and a two-man night crew. This week they drilled six casings to bedrock, drilled six sockets to depth in bedrock, and set in concrete, soldier piles 29W, 31W, 32W, 33W, 34W, and 35W. They have five more soldier piles to drill and set. Once the soldier piles are in place, the drill and drilling crew will move off site and a sheet pile crew will return with a vibro-hammer to drive the remaining 250' of sheet pile and complete the shoring wall behind the soldier piles.
Work completed 8/3/20 to 8/7/20
H.B. Fleming had a crew of four on site this week: two worked days and two worked nights. They drilled casings to bedrock, augured soil out of the casings and drilled bedrock piling sockets. They placed concrete for and set soldier piles 23, 24, 25, 26, 27, 28, and 30 West. They have 14 more soldier piles to drill and set, and then they will finish driving west side sheet piling behind the soldier piles. Fleming and MacMillan are considering a couple different bracing systems to complete the shoring system once the west side sheet pile wall is complete.
S.E. MacMillan's crew numbered 14 this week. They completed installing reinforcement steel and formwork for slab section #4, and placed concrete on Tuesday. N.S. Giles' concrete pump truck was on site at 4:30 a.m., S.W. Cole had two concrete testing technicians on site, and O.J. Folsom delivered 248 cubic yards of concrete between 5:00 and 10:45 a.m.
On Wednesday, SEM finished excavation for slab section #5. On Thursday and Friday, they put down filter fabric, graded 1.5" and 0.75" base stone, tied the bottom mat of reinforcement steel, built formwork, and connected form ties from existing slab concrete to #5 slab form panels. They will complete reinforcement steel and formwork and place concrete for slab section #5 next week. Once #5 is complete, they will begin construction of the full height wall sections, working from slab section #5 north along the east side Tank wall, back toward slab section #1. The concrete Tank walls will be 23' high and 3' thick.
Work completed 7/27/20 to 07/31/20
S.E. MacMillan had a crew of 14 on site this week. They started the week having completed the excavation for slab section #4 last week. They fine-graded the base stone and set the concrete brick which provide the correct spacing between the reinforcement steel and the slab bottom. They set up the first lift of formwork on the three sides away from the existing concrete, put the bottom reinforcement steel mat into place and built the second tier of formwork. The lower steel mat is held between the bottom and second tiers of formwork. Once the lower mat is in place and the second tier of formwork has been erected, they tie the "chairs" which hold the top mat and install the form ties, which holds the form in place. Each slab section is a rectangle, three feet thick. The form ties are steel rods running north and south about 50' long, and east and west about 40' long. After all the tie ends are secured in steel slots at the forms, both the N/S and E/W tie sets have their ends welded inside the formwork. After the ties are in place, the top reinforcement mat is partially tied into place and vertical steel is tied. The vertical wall steel is tied to both the top and bottom mats, therefore for better accessibility only part of the top mat is tied before the wall steel is tied. The final top mat bars are placed and tied last, along with formwork for bond-outs and water-stop. MacMillan has needed about seven work days to complete formwork and reinforcement steel construction for each slab section. They will place number four (of 15) next week.
H.B. Fleming ran two work shifts this week, two men on days and two men on nights. They are drilling through soil overburden and into bedrock. They drill into bedrock to make a "socket" which, along with concrete fill, provides a solid anchoring cylinder for the "H" shaped soldier piles. The soldier piles are the structural support for the sheet piles which will be driven behind them, forming an interlocking sheet wall once all the soldier piles are in place. Fleming has about 20 more soldier piles to install. They're drilling to a design depth and the bedrock height has varied. This week they were drilling fairly deep into the rock, about 15' of rock socket depth for each pile. The piles are about 37.50' long and just barely can be seen above the current ground surface where Fleming is working. Fleming drilled the casings and set the piles #21West and #22West this week, and drilled casings #23West and #24West to bedrock.
Work completed 7/20/20 to 7/24/20
S.E. MacMillan had 14 people on site this week. They finished tying the reinforcement steel, formwork, form ties, and water stop for Tank slab section #3. On July 23rd, N.S. Giles set up their concrete pump truck at 4:30 a.m. Hughes Brothers began delivery of 240 cubic yards of concrete at 6:30 a.m. The concrete was placed by 11:15 a.m. and the slab was finished by hand with steel trowels. MacMillan excavated to subgrade, hammering out bedrock 1-3' above subgrade, put down fabric and base stone for slab section #4 to be placed on August 4th.
H.B. Fleming had four people on site week split into two-person crews: one crew worked a ten-hour day, and the other worked a ten-hour overnight shift. They installed west side soldier piles #16, #17, #18, #19, and #20.
Work completed 7/13/20 to 7/18/20
S.E. MacMillan completed formwork and reinforcement steel for the second (of 15) Tank slab concrete placements. On Tuesday, July 14, Owen J. Folsom delivered 245 cubic yards of concrete and N.S. Giles' pump truck pumped it into the forms. Eighty cubic yards an hour was placed from 5:45 to 9:45 a.m. The slab was finished by hand with steel trowels, covered with a curing blanket, and kept moist with a sprinkler. The forms were stripped the following day and fill concrete was pumped between the slab and the shoring wall for extra sheet pile anchor. MacMillan excavated to subgrade for the next slab section, put down fabric and fine graded the stone base. They started formwork and tying reinforcement steel. They plan on making another slab pour, #3, next Thursday, July 23.
H.B. Fleming set piling #15West in place on Thursday, July 16. They are into a section of the shoring on the west side shoring wall that requires a deeper design depth and the bedrock there is higher than anticipated so their progress has been slowed. They are drilling soldier piling sockets 15 to 20' into bedrock at about 6" an hour. They are drilling 42" diameter casings, 24' long through about 10 or 15' of overburden to bedrock. The soldier piles are H-14/89 and are 37' long. The casings act as formwork for setting the H-pile into place.
The photo above is a view from the south looking north into the Tank excavation. The Penobscot River is on the right, Pan-Am's rail tracks are on the left. MacMillan is working on placing the Tank concrete base slab on the right and Fleming, on the left side, is working on the west side shoring wall. Fleming has installed roughly 640' of shoring wall, about 230' remain to be installed. On the east side, MacMillan is working 30' below finish grade. On the west side, Fleming is drilling and setting soldier pile 53' below finish grade. Ground water has been managed so far by four 3" electric pumps.
Work completed 7/6/20 to 7/10/20
S.E. MacMillan had 14 people on site this week. They excavated to subgrade, put down fabric, crushed stone base, formwork, and tied both bottom and top reinforcement steel mats. Concrete placement #2 is scheduled for Tuesday, July 14.
H.B. Fleming's crew size was diminished this week by four, with only two on site the last three days. They completed drilling sockets in bedrock, placing concrete and settling soldier piles for #11West, #12West, #13West, and #14West. They have been drilling about 15' into bedrock at a rate of 6" of depth an hour. The sheet pile crew will return once the drilling crew has moved far enough ahead to warrant more sheet pile work
Work completed 6/29/20 to 07/03/20
S.E. MacMillan had 15 people on site this week. They completed formwork, installed water stop, reinforcement steel, and form ties for placement of the first Tank foundation slab section. On July 2, N.S. Giles' concrete pump truck arrived on site at 4:00 a.m. The first Hughes Brothers mixer arrived on site at 4:30 a.m. Hughes Brothers assigned six mixers for the placement. Two S.W. Cole technicians, along with a Hughes Brothers representative, were on site to monitor concrete quality and take test cylinders. They started pumping concrete at 4:45 a.m. and finished at 8:45 a.m. 210 cubic yards were pumped into the formwork. An average of five trucks per hour were delivered, tested, and pumped into the formwork.
H.B. Fleming had a crew of six people on site this week. They finished work on the east side shoring wall. They welded the final wailer braces, finished checking and driving all sheet piling to a final depth. Fleming also determined that no further raking braces will be installed on the east side. MacMillan will dig to subgrade as necessary for each slab section, place the slab, and then place fill concrete between the slab and the shoring wall. Fleming finished drilling sockets in bedrock for #6West and #10West soldier piling. Drill depth into bedrock for these two sockets was 19.30' for #6W and 13.68' for #10W. Both of these piles were set in concrete. Casings for #11W and #12W were drilled into place.
Work completed 6/22/20 to 6/26/20
S.E. MacMillan had 13 people on site this week. They received the first reinforcement steel delivery on Tuesday, about 50,000 pounds out of 1,600,000 pounds to be delivered to the site before the end of next year. MacMillan bought a Grove hydraulic crane and it was delivered to the site on Monday. The first concrete section to be placed is the northeast corner of the tank, a 41' x 47' section, 3' thick. They excavated to subgrade, put down a non-woven filter fabric, put down 1' of crushed stone to grade, set formwork, and tied about 90% of the reinforcement steel. The first placement is scheduled for Wednesday, July 1, 2020. MacMillan had an excavator operator excavating for Fleming at sheet locations where obstructions were impeding full sheet depth.
H.B. Fleming had six people on site this week. They welded wailer braces on the east shoring wall and hammered sheets to full depth where there had been obstructions. Fleming worked on connecting the southeast ramp and shoring walls with threaded corner anchors. They drilled 10' deep sockets into bedrock for soldier pile #8West and #9West, placed concrete into the sockets, and set the piling into place. On Wednesday, their drill suffered a breakdown and a man was sent to Pennsylvania for replacement parts. There is a total of 46 soldier pile on the west side Tank shoring wall.
Work completed 6/15/20 to 6/19/20
S.E. MacMillan had a 12-person crew on site this week. There are 15 separate concrete placements necessary for the base of the Tank. The first section is in the northeast corner of the Tank, is 3' thick, and measures 41' x 47'.
MacMillan excavated to subgrade for placement #1, put down a non-woven geotextile and then a foot of crushed stone to a fine grade. On top of the stone they will set the form work, tie reinforcement steel, and place the first section of the concrete Tank foundation slab. There were four men building concrete forms which will be hauled to the site and assembled. MacMillan hopes to make the first concrete placement on July 1st.
MacMillan bought a 100-ton Grove hydraulic crane this week and will have it delivered to the site on Monday, June 22nd. This crane will move forms and reinforcement steel into place.
H.B. Fleming had six people working on site this week. The drilling crew drilled casings, sockets into bedrock, and set piling into concrete for soldier pile #1W, #2W, #5W, and #7W. Fleming says the bedrock is at about elevation -10.00, or about 9' along the southwest shoring wall.
The pile driving crew worked on bracing. They hung and welded corner bracing into place for the southeast Tank corner and ramp wall and welded another 40' section of raking brace wailer between soldier pile #22E to #28E. Fleming also installed another course of threaded through-wall, wailer to wailer tie backs, from the southeast Tank wall the southeast ramp wall.
Work completed 6/8/20 to 6/12/20
S.E. MacMillan had ten men on site this week. MacMillan worked on excavating the northeast corner of the Tank. They worked with H.B. Fleming on timber lagging between soldier pile #8East and #9East and welded steel covering to patch voids in the sheet pile wall where obstructions denied the desired sheet depth. MacMillan excavated to elevation -6.00 in the northeast corner, where the first concrete placement will take place. Elevation -6.00 is 28' below finish grade (elevation 22.50). MacMillan will still need to excavate six more feet to -12.00 where a foot of crushed stone will be placed, on top of which the concrete tank will be built. De-watering is currently being managed with three 3" electric pumps. Previous soil borings had indicated more ground water than is currently being realized. If necessary, MacMillan has over 40 three-phase electric pumps ready for de-watering.
A representative of Dimension Steel from Scotia, New York was on site this week to discuss the first reinforcement steel delivery on June 23rd. The first concrete placement will need 26 tons of reinforcement steel and 220 cubic yards of concrete.
H.B. Fleming had six men on site. Fleming set soldier pile #3West and #4West. They hammer-drilled sockets in casings #1W, #2W, and #5W. They encountered bedrock at elevation -9.00. Ten feet deeper at -19.00 is the sub-grade elevation in the southwest Tank corner, 41 feet below finish grade.
Fleming installed threaded shoring anchor restraints in the corner of the northeast shoring wall to the northeast ramp wall. They finished driving the east side sheet pile to desired depth and installed wailer bracing at elevations -6.00 and -2.00 between SP#1E to SP#12E.
Work completed 5/26/20 to 6/5/20
H.B. Fleming had a crew of six men on site during the last week of May, and five men for the first week of June. S.E. MacMillan was not on site during the last week of May, and had ten men on site for the first week of June.
The primary activities on site were pile driving and iron work. Fleming has completed about a third of the shoring system. MacMillan can begin the final excavation phase on the east side in earnest once Fleming has completed the soldier pile, sheet pile, and bracing on the east side of the Tank excavation.
MacMillan's construction progress schedule indicates Fleming is on schedule and likely to complete the shoring system by September 1, 2020. The first concrete placement is shown on the schedule for September 1, 2020.
Fleming drilled anchors through the shoring wall which were meant to act as tie-back restraint. They drilled in four anchors and began to use a hydraulic testing mechanism to pull tension against the anchors. The anchors would not achieve desired test resistance pressure and so Fleming decided to use an alternative, inside the wall, bracing method. The inside bracing method was initially less favorable for reasons of space limitations inside the shored area. The anchors did not pass because of the granular nature of the soils and their instability due to the ground water pressure.
Fleming set the last four east side soldier pile in place and completed the east side sheet wall from the north to south ramp walls. Fleming also braced the northeast corner, attaching wailers to soldier pile and between soldier pile.
S.E. MacMillan excavated to elevation -5.00 (about 32 feet below original grade) in the northeast corner for the installation of an added wailer which will be part of the change from drilled anchor restraints to a bracing system. A few of the sheets are still above the desired depth, leaving voids in the sheet pile wall. Some of these voids will be covered with 8x6 timbers placed inside the vertical soldier pile flanges. MacMillan worked with Fleming to excavate boulder obstacles and try to drive sheets to the full desired depth.
Work completed 5/18/20 to 5/22/20
H.B. Fleming had a six-man crew on site. They welded H-pile wailer sections between soldier pile. These are part of a shim system providing complete support for the sheet wall against the continuous wailer which will be put in place across the Tank side flange of both the vertical soldier pile and the H-pile wailer filler. These shim/filler wailers are complete across soldier pile bays from SP#1 to SP#14, and are necessary as the sheet pile are in place on an irregular line.
Fleming installed SP#22, SP#23, SP#24, and SP#25. They drilled into place casings #26 and #27.
S.E. MacMillan was not on site this week.
Work completed 5/11/20 to 5/15/20
H.B. Fleming had a crew of six on site. They installed soldier pile #19, #20, and #21, and they drove sheet pile approximately 100 linear feet from soldier pile #18 and they attached the 14x89 H-pile wailer to the northwest shoring ramp wall.
S.E. MacMillan had a crew of ten on site. They began excavating east of the Tank centerline to elevation -2.00 from soldier pile #4 to pile #14, and also cleared the wooded strip of MDOT land between the I-395 Main Street off-ramp and the Roundhouse fill site.
S.W. Cole had a crew of five on site for two days this week. They made ten soil sample borings. Lab analysts will determine whether the deeper site soils have not been contaminated and therefore can be safely used off site.
Work completed 5/3/20 to 5/9/20
H.B. Fleming had two men on site this week. They drilled in the casings and installed four soldier pilings: #15, #16, #17, and #18 along the east side of the Tank excavation. Soil conditions have prompted MacMillan to pre-dig casing locations.
S.E. MacMillan had an eight-man crew this week. They excavated to remove boulders and timber obstacles at casing locations to facilitate pile work along the southeast line of the Tank excavation. They also finished rip-rapping the soil filter pond outlet, screened loam at the Roundhouse site, installed perforated pipe for dewatering along the entire length of the west side of the Tank excavation, and stockpiled gravel on the former Barret Paving site.
Work completed 4/27/20 to 5/3/20
H.B. Fleming had a five-man crew on site. They drove about 38 linear feet of sheet piling along the northeast end of the Tank excavation, around the corner, and south along the east wall of the Tank. There are boulders below grade in some locations holding the sheets up from their designed depth and these boulders will have to be excavated out.
Fleming also drilled casings to bedrock for soldier pile. Two casings this week had sockets drilled into bedrock. Fleming pumped concrete into these two sockets this week, set the soldier pile into the concreted sockets and removed the casings. Sixteen of 32 soldier pile have been set into bedrock on the east side of the Tank excavation. The west side of the Tank excavation has another 45 soldier pile to be installed.
Fleming began building the bracing necessary for the ramp wall shoring. Three of four wailer braces were welded into place, two on the south ramp and one on the north ramp.
S.E. MacMillan had an 11-man crew on site. They put up a fence and a gate between the Roundhouse fill site and the haul road as a barrier against the public's access to the VRAP material being stockpiled there.
MacMillan ran an underground temporary power cable from temporary panel #1 to temporary panel #2. Each of these panels will service ten three-phase electric pumps meant to dewater the north and east sides the shored excavation. Another 20 pumps will be powered by mobile generators.
MacMillan built the rip-rapped outfall for the soil filter pond, ran the 12" pipe and set the 4' diameter catch basin. The pond itself will not be built until the Tank is completed and finish grade is established. They also built a gravel lot for rebar laydown and fabrication.
Work completed 4/20/20 to 4/24/20
S.E. MacMillan excavated for dewatering sumps and ran discharge lines to silt bags in sediment ponds this week. They have been running pumps off generators from sumps on the west and east sides of the Tank excavation in an attempt to gauge the ground water elevation ahead of the sheet pile shoring construction. The shoring system is meant to hold back the earth outside of the construction area and provide a cofferdam-type barrier, not completely watertight but impermeable enough that existing ground/tide water elevations can be successfully managed and pumped out of the excavation area into the sedimentation control ponds.
Pictured above: Two silt bags filter water inside MacMillan's southern-most sedimentation pond.
MacMillan added to the concrete cover wall they've been placing along the face of the existing Davis Brook 8'x9' box culvert sewer. This is an added support against the exposed joints/seams in the structure.
H.B. Fleming set four soldier piles into concreted bedrock sockets this week; piling #9, #10, #11, and #12. They started drilling/excavating for #13 and #17 casings. They also finished driving sheets for the southern ramp walls and began to weld bracing support on those walls.
Work completed 4/13/20 to 4/17/20
S.E. MacMillan excavated to install vertical pipe as sump sleeves for dewatering pumps. They installed three of these sumps, each used 36" diameter PVC pipe. They cut slots in the spigot pipe ends and stood them on a bed of 2" crushed rock. MacMillan buried these sumps to elevation -16.00, about 30' below the original walking path finish grade. They connected these sumps to each other with a stone trench wrapped in non-woven filter fabric. Each sump can accommodate a 6" or 3" pump as necessary. This sump/trench line when finished, will extend across the entire length of the Tank foundation. Once the shoring has been installed around the entire foundation excavation, MacMillan will have to dig some of these sumps down another 5' in order to be dewatering 2' below the lowest Tank concrete foundation elevation.
H.B. Fleming drove sheet pile for the south east and west ramp walls. These walls will provide shoring for the ramps on the north and south ends of the Tank. The ramps will be used for further excavation access. Fleming is using an 11,000 pound vibrational hammer to drive the sheet pile.
Fleming also drilled casings into the ground for soldier pile. They are working on the northeast corner of the Tank excavation. They drilled/excavated into place casings for piling 3, 8, 9, 10, 11, and 12. Casings and soldier pile are numbered consecutively from the northeast Tank corner to the southwest Tank corner. They also set H-piling 3, 4, 7, and 8. There are 37 soldier pile on the east side of the Tank.
Work completed 4/6/20 to 4/10/20
S.E. MacMillan had a ten-man crew this week. They built a six-foot high concrete wall as protective cover against the exposed 8'x9' box culvert sewer. Soldier and sheet pile shoring will be installed near this sewer conduit. MacMillan also worked on site access roads, dewatering sumps, and pump discharge piping.
This week, H.B. Fleming had a four-man shoring crew. Fleming is working in the northeast corner of the Davis Brook CSO Tank. They are building the shoring system necessary for excavating the deepest material from the Tank foundation. Fleming has two Soilmec drill rigs on site, they are built for large diameter drilling into soil and rock. Both drill rigs are capable of drilling over 100 feet into the earth. They are drilling 30 and 36 inch steel casings down to bedrock. Inside the casings, they drill through and excavate out soil and rock. Once the casing is at refusal they drill inside the casing, into the bedrock, with a large pneumatic rock drill. Into these bedrock drill holes, or sockets, Fleming pumps concrete and then stands thirty-foot long H-pile into the concreted socket. These are soldier pile, embedded in the bedrock and reinforcing the entire sheet pile shoring wall. The soldier/sheet pile system will remain in the ground after the 3.8 million gallon Davis Brook CSO Tank has been built. The bottom of this shoring system will be approximately 40 feet below finish grade.
Fleming installed four soldier pile this week on the northeast Tank corner and drilled casings for two more. There are 83 soldier pile to be installed, 37 on the east Tank wall and 46 on the west Tank wall. Two of the four casings have sockets drilled into bedrock and are ready for concrete and soldier pile next week. They are progressing south along the east side of the Davis Brook CSO Tank foundation.
Work completed 3/23/20 to 3/27/20
S.E. MacMillan completed their first Tank excavation phase, which included the removal of the amphitheater mound (finish grade elevation 32.00) to elevation 5.00. MacMillan has hauled just over 50,000 cubic yards of soil to the Roundhouse fill site. This fill has been compacted and graded up against the MDOT's retaining wall along the I-395 Main Street off-ramp. The second phase of excavation will take place after shoring has been installed. This second phase excavation will reach elevation -24.60 to the bottom of the deepest footing, or 56' below the top of the amphitheater mound.
MacMillan stabilized the east and west backslopes of the Tank excavation with a cover of stone ballasted 6 mil reinforced poly on the east (river) side and non-woven filter fabric and 6 mil poly over the west (railroad) side. The permanent fence against the railroad right of way was taken down and a temporary fence was erected closer to the tracks to allow for the erection of sharing and Tank concrete construction.
Shoring contractor H.B. Fleming continued to mobilize. They started driving sheet pile for the north side access ramp on Monday and finished the east side sheets of the ramp on Wednesday. They have been receiving a steady stream of sheet pile deliveries. They have received the entire H-pile pieces for the project, 41 sixty-foot H-beams each weighing 10,680 pounds. Fleming started drilling the first H-pile to be set into the bedrock with concrete. There are 83 of these soldier piles in the shoring system. Each 30'-long soldier pile will be placed in a 30" diameter socket drilled 6' into the bedrock and then set in concrete.
Work completed 3/16/20 to 3/20/20
S.E. MacMillan excavated about 9,000 cubic yards from the CSO Tank location and hauled it to the roundhouse fill site. They are excavating to elevation 5.00 around the entire perimeter of the CSO Tank, with another twenty feet outside the tank perimeter to accommodate the necessary shoring system to be constructed.
H.B. Fleming, the shoring contractor, arrived on site Tuesday. They hope to start driving sheet pile on Monday, 3/23/20. They set up a crane, a 90-ton augur drill, and unloaded sheet pile and 30" diameter augur bits.
Surveyors from Plisga & Day were onsite to survey recently established monitoring points on the railroad and 8'x9' Davis Brook sewer. These points are markers indicating the existing locations of the train rail and the sewer structure and the points will be continually monitored for movement throughout the excavation, dewatering, and construction process.
S.E. MacMillan dug a test sump to elevation -7.5, which is still about six feet above subgrade or bottom of stone bedding for the new CSO concrete tank. This depth is about 39.50 feet below the top of the amphitheater mound's original existing finish grade elevation 32.00. They dug this well/sump to see what the soil condition is at that elevation and see if it was possible to lower the water level in the sump pipe with one three-inch, three phase electric pump. They found they could lower the water in the sump even at high tide on Wednesday morning.
A section of in-place railroad track and ties was excavated this week at elevation 5.00, which is about ten feet below the elevation of the rail yard when it was closed in 1992.
The roundhouse fill site has risen to near the top of MDOT's retaining wall at the I-395 Main Street off-ramp.
Work completed 02/03/20 to 03/06/20
Fenced and closed to the public the lower end of the Waterfront Park and walkway from the southern end of the Railroad Street parking lot to Dutton Street beneath the train bridge.
Installed erosion control for the 3.8-million gallon CSO tank site and roundhouse fill site. The roundhouse fill site is part of the land acquired by the City from the railroad, as well as a VRAP site that MaineDOT has agreed to allow the City to fill up against the I-395 retaining wall. VRAP is the City's agreement with Maine DEP for voluntarily managing the contaminated soils from the acquired railroad property.
MacMillan built four 50'x100' sedimentation control ponds for handling the dewatering pumps. MacMillan expects to use 32 three phase electric pumps: 16 3" and 16 6". They are excavating to elevation -12.00 and the average height of ground water at high tide is elevation 5.00.
MacMillan built haul roads for the CSO tank excavation and the roundhouse fill site. The lower end of Dutton Street has been closed to the public and a ramp was built at the entrance of the roundhouse to ease truck access and to safely separate the haul traffic from the public.
Eighteen light poles from Waterfront Park have been taken down and stored for reinstallation in 2022.
MacMillan has excavated and hauled about 13,000 cubic yards of material to the roundhouse site.
Davis Brook CSO Storage Tank project details
In preparation for the 3.8 million gallon Davis Brook CSO storage tank, the City of Bangor will close a portion of the Bangor Waterfront trail beginning Monday, February 10, 2020. The Davis Brook CSO storage tank is a significant project that will reduce the number and volume of combined sewer overflows that enter the Penobscot River. The project is expected to take two years to complete. The closure will begin at the south side of the parking lot behind the Waterfront Concerts venue and will continue to Dutton Street. No public access will be allowed during the closure to allow for a safe and secure construction zone.