Presentation on theme: "City of Ottawa’s Lemieux Island Transmission Main Replacement Program Low and High Pressure Transmission Mains by Mike Willmets, City of Ottawa Derek."— Presentation transcript:
1City of Ottawa’s Lemieux Island Transmission Main Replacement Program Low and High Pressure Transmission Mainsby Mike Willmets, City of Ottawa Derek Potvin, P.Eng., Robinson Consultants
2Presentation Outline Water Works History Existing Conditions Construction
45 km of 1200, 1675, 1980 mm diameter Transmission Main Project Overview5 km of 1200, 1675, 1980 mm diameter Transmission MainServes 400,000 people within City of Ottawa.Replaces three discharge mains from Purification Plant.One of the Transmission Mains operates as a low pressure (gravity) suction supply for a Fleet Street Pumping Station and the other operates at distribution system pressure.
6Why Supply Drinking Water? Water delivered by horse & wagon in wooden barrelsEra of Great Fires: Quebec City in 1845, Montreal in 1852, Carleton County in 1870, Chicago in 1871Fire Insurance UnderwritersToronto , Kingston , Hamilton
7Thomas Coltrin Keefer 1821 - 1915 Father of the Ottawa Water WorksOne of Canada’s greatest engineersBuilt similar water systems in Montreal, Hamilton & Toronto
13Typhoid Epidemics 1 epidemic in 1911, 2 epidemics in 1912 Mill refuse and sewage - polluted water enters the system through corroded intake pipes1 epidemic in 1911, 2 epidemics in 19121900 to related deaths1916 to related deathsNepean Bay pollutionwood stave intake replaced in 1890 with 40 inch steel pipe1 epidemic in 1911, 2 epidemics in 19121900 to related deaths1916 to related deathsNepean Bay pollution
14ABC Lines Three of the most important mains Lemieux WPPFleet P.S.Three of the most important mains in the entire systemSupply water to 400,000 people – 60% of population (including downtown)“backbone” of the systemRole in the systemLines B and Line C supply water to the Fleet Street Pumping Station by gravity flow (200 MLD of average 300 MLD). Low pressure feed to Fleet St. P.S. Fleet Street PS boosts the water pressure to the distribution system at a savings of $750 K/yearHigh pressure to system Line A is currently operated as the only high pressure link between the Lemieux Island WPP and the distribution SystemThree of the most important mainsCritical to operation of systemUnique Pipes in a Unique Setting
15Lock Bar Pipe Two semi-circular sections joined by a ‘lock bar’ Lock bar is long strip of metal with an ‘H’ shaped cross sectionRiveted joints to join pipe to pipeUse of steel pipe originated in 1870 where no cast iron foundries existed(Australia Western North America)Steel was cheaper and easier to transport in plates for large diameter pipesLock-bar originated in Australia in 1896 and used in 1897 for the 915 mm 557 km Coolgardie lineCorrosion problems (British firm Sir Alexander Binnie was hired to investigate)Binnie was also hired to investigate water supply for City of Ottawa at the time of construction of ‘A’ and ‘B’ Lines
18Existing Pipe Condition Corrosion pitting leads to leakage.Corrosion of rivets & lock bar can lead to pipe failure.“A” & “B” Line’s cement lining (circa 1950) was delaminating which accelerated internal corrosion.“C” Line was in good condition but required relocation for planned development.90 years later this is what the pipe looked likeThe exterior coating was in poor condition, the interior lining was delaminatingLike all steel pipe this lead to corrosion pitting and leakage,Of greater concern was the corrosion of the lock bar which could lead to rupture of the pipe.
19Site Constraints Federal Land LeBreton Flats Development Past Land UsesBreezehill/Scott FeedermainsSubsurface ConditionsThe landscape had changed since the transmission mains were originally installed,Much of it was Federally owned, it was identified by the Federal government for a large redevelopment projectand several key feedermains had been connected to the transmission mains.
20Existing Site Conditions Adjacent to former Municipal Waste Site » Contaminated Soils and Groundwater » Highly Corrosive Environment.Area formerly part of Ottawa River » Significant area of unconsolidated fill material.Adjacent to Ottawa River » Dewatering issue during construction.Area formerly an industrial development » Subsurface remnants and contamination.Crossing major transportation corridors » Traffic Implications.Construction within existing aqueduct channel » Protection of watermain.Construction within existing AWWA Canadian Waterworks Landmark and Heritage Structure » Fleet Street Pumping Station.Lemieux Island WPPHad to understand the history of the site to complete the design.Fleet Street Pumping Station
22Subsurface Conditions High Pressure Transmission MainAlbert StreetWellington StreetBayview YardsLemieux Island WPPNepean BayLow Pressure WMThis photo summarizes many of the issues we were faced with on the project.
23Geotechnical Conditions The soil profile shows the fill in brown over bedrock in grey. The fill was placed during the filling of Nepean Bay. This posed some geotechnical difficulties. Will discuss more later..Admittedly, the LPTM has a few more unique features than a typical feedermain, but the point is,it is important to understand what impacts, past, present or future activities may have on the pipe.Unconsolidated fill from Nepean Bay and Ottawa River Parkway over bedrockLong term settlement concerns and significant dewatering
24Dynamic CompactionLarge Un-consolidated Fill Zone on reclaimed land » former bay of the Ottawa River.Dynamic Compaction used to prepare watermain alignment prior to construction.Large steel weight dropped from crane to achieve consolidation.Compaction can be achieved to over 10m depth.Compaction carried out using grid pattern to cover area.Compaction testing carried out after completion.
25Corrosion Potential Investigation As a result of the past land uses and the landfills we compiled existing data and completed our own investigations to define the contaminated areas – to assist in the selection of the best route – point out landfills and snow dumps and contaminated hot spots with potential to corrode the pipeObtaining the information is not that difficult, for example a Phase I ESA combined with contaminant and corrosion potential testing can be completed for any project and will produce the findings shown above.
26Preferred AlignmentIntroduce the location of the aqueduct, Parkway, rail line, transitway, major roadsWithin the middle of the proposed development
27Design Requirements 100 Year Design Life Required. Must maintain water supply to customers.LPTM to serve dual purpose » Operate primarily at low pressure with conversion to high pressure based on demand.HPTM to supply water to distribution system from pumping station at WPP.In addition to the challenges of identifying a suitable alignment for the transmission mains, the project had some challenging design requirements.Must maintain access to existing purification plant.Must protect existing heritage structures » Fleet Street Pumping Station and Open Aqueduct.
28Watermain MaterialsConcrete encased, polyurethane coated, steel pipe and concrete pressure pipe utilized to protect against corrosion.Gasketless, double lap welded, bell and spigot joints specified to protect against groundwater ingress in landfill zones.Transition between material types at valve chambers.Cathodic protection installed throughout.Two pipe materials were used on this project. Concrete encased…(1st bullet)In the landfill zones and highly contaminated areas, gasketless, double (2nd bullet)
29Ruins from Previous Development Previous railway structures, bridge abutments, building foundations and superstructure debris uncovered in the watermain excavations.Previous factory foundation and tunnel uncovered within the excavations.Shows some of the remains of former developments uncovered on the site.
30Concrete Encasement 150 mm concrete encasement Pipe strapped to concrete slabs to counterbalance buoyancyThe corrosion control system involved three systems, concrete encasement, polyurethane coatings, and cathodic protection.Bottom slab placed first, then pipe strapped to slab, then concrete backfill placed.
31Open Aqueduct Installation Coated concrete pressure pipe installed in existing open aqueduct channel.Channel is a “neighbourhood feature” and a designated heritage structure.High density polyethylene shield added to protect watermain from objects falling or being thrown into water.Gasketless expansion joints used between fixed supports to allow for temperature movements.
32Fleet Street Pumping Station Existing AWWA Canadian Water Works Landmark and heritage structure.Turbine pumps driven by water from Ottawa River » fed by aqueduct system.Connection of new transmission main with valve chamber to switch to high pressure operation » by-passes pumping station.Included replacement of existing suction header piping in station.Installation of sluice gates to isolate pump turbines from aqueduct flows during maintenance.Included measures to protect existing structure from damage during construction.
33Bridge Pipe Rehabilitation Couplings repaired and internal joints seals installed.The existing pipes on the bridge form the Lemieux island WPP to the mainland were in good condition,We simple refurbished the couplings and installed internal joint seals.
34Tunnel ConstructionTransmission Main constructed in casings across major roads, parkways, railways and rapid transit bus route.Steel pipe electrically isolated from casing pipe via casing spacers.Annular space grouted.The transmission mains was installed in casings at several locations. Photos show the pipe in the casing with the casing spacers, grout hoses and restrained couplings.
35Ottawa River Parkway Crossing Crossing of existing federally owned four-lane, divided parkway required.Open trenching construction due to presence of methane from landfill » explosion hazard during jacking and boring operation.Existing fill material not suitable for jacking and boring » large boulders.Installation of concrete casing pipe completed over one weekend road closure.Welded steel watermain inserted by jacking methods after completion of casing.Installation of the welded steel transmission main was slow. To speed up road crossings, reinforced concrete pipe was installed across roadways to limit the duration of the road closures or detours.Tunneling across the four lane arterial road would have been preferred, but methane levels at the crossing were above the explosive limit, photos show the crossing of the four lane roadway.
36Not all goes as planned!Steel pipe partially collapsed during grouting.Protrusion cut out, grout removed and new repair sleeve welded in place.
37Valve Chambers Steel pipe continued through the valve chambers. Features: air valves, drain valves, line valves, branches and access manholesAppreciation of scale – this is the smallest of the valve chambersThe valves on the 78” water main are about the size of a small house.