1. Summary
The demolition project in Whistler involves transforming a three-room basement into a flat living space. The site is characterized by a promontory of hard volcanic rock covered with varying layers of gravel and concrete. The project presents unique challenges due to its location near neighboring properties and environmentally sensitive areas. Careful planning, coordination, and adherence to safety measures are essential. The demolition methodology includes drillhammering, expanding grout application, jackhammering, debris removal, and site cleanup. The silicified basaltic andesite zone proved to be the most challenging due to its exceptional hardness, due to this, the project took longer than anticipated, but the desired level was eventually achieved.
2. Introduction
The Whistler demolition project aims to convert a three-room basement into a flat living space. The site’s unique geological characteristics pose challenges as it sits atop a hard volcanic rock promontory covered with layers of gravel and concrete. With neighboring properties and environmentally sensitive areas nearby, careful planning and coordination are crucial for ensuring safety and minimizing disruptions. This article explores the methodology, equipment, and tools employed in the demolition process, as well as key recommendations based on the project’s experiences.
3. Objective
The demolition project poses unique challenges due to the characteristics of the site, as it is located in a three-room basement primarily occupied by a promontory of very hard volcanic rock covered with a layer of gravel of variable thickness and concrete of 2’, as shown in the next image. The objective of this project is give rise to a flat surface in a lower level, to create a living space in the basement. Surrounded by neighbouring properties, careful planning and coordination are essential to minimize disruption to adjacent buildings and ensure the safety of the public and workers involved. Additionally, the site’s proximity to environmentally sensitive areas requires adherence to strict regulations to protect the natural environment and maintain Whistler’s commitment to sustainability.
4 . Context of the Site
Located in the stunning mountains of British Columbia, Canada, the site of this demolition project in 2231 Gondola Way, Whistler Creekside, showcases the unique combination of natural beauty and modern infrastructure for which the region is famous. Whistler, located in the Coast Mountains, is a world-class resort community known for its stunning scenery, outdoor recreation, and a vibrant tourism industry (image 2).
The Coast Mountains, where Whistler is situated, are part of the larger Pacific Cordillera, a mountainous region extending along the western edge of North America. These mountains are a result of intense tectonic forces associated with the ongoing collision between the Pacific and North American tectonic plates. The bedrock underlying Whistler primarily consists of various types of metamorphic and intrusive igneous rocks. Metamorphic rocks such as schists, gneisses, and amphibolites are prevalent, formed through the transformation of pre-existing rocks under high pressure and temperature conditions. Intrusive igneous rocks, including granites and diorites, are also present, representing solidified magma that intruded into the Earth’s crust (Cui, Y., Miller, D., Schiarizza, P., and Diakow, L.J., 2017). The younger volcanic rocks in the region, like an andesites, basalts and mixes of both, make up volcanoes built on older granitic and metamorphic rocks.
The volcanic rocks are the most important within the context of the work site, since it is located on some hard basaltic andesite lava flows that have undergone three different processes, which have given rise to a zoStructural Fault & Dip.nation in the structure, hardness, texture and physical-chemical composition of the rocks on which the house is located. The structures, with a preferential NW-SE course and almost vertical dip, configure the rock mass it in such a way that it can be subdivided into three textural and hardness units (Image 3 & map 1):
a) Coarse-grained basaltic andesite: Rich in plagioclase, feldspar and amphiboles minerals. Quartz and pyroxene minerals may be absent or present in trace amounts. Coarse mineral grains indicate slow cooling. They are common rocks of the continental crust above subduction zones. It is usually one of the hardest rocks on the earth’s surface, when weathering factors has not affected him significantly.
b) Silicic fine-grained basaltic andesite: With the same mineralogical content as coarse-grained basaltic andesite, but with a fine grain due to its relatively fast cooling and later affected by hydrothermal activity that injected silica between the fractures and porosity of the rock. This process callled silicification made of this unit the most hard rock and difficult to fracture unit in the work site.
c ) Shear zone andesite: It consists of a unit of a soft and brittle basaltic andesite affected by efforts that gave rise to a fault zone with a preferential NW-SW course, which were affected by hydrothermal activity that gave the rock porosity, converting its original minerals into clays and giving rise to the deposition of sulfides mainly of iron, lead, zinc, copper, as well as silver and gold in trace amounts.
4. Used Gear and Materials
4.1. Drillhammers (40 lb) with 1.5” bits and drillsteels (2′ to 4′ long): Used for drilling holes at a 90-degree angle in the rock mass.
4.2. Expanding Grout (Nexpro type II for 1°C to 25°C): Mixture used to fill the drilled holes, expand, and exert pressure on the surrounding material.
4.3. Diesel & Electrical Heathers: To speed up the grout expansion process.
4.4. Safety Equipment: Half-mask respirators, safety glasses, earplugs, helmets, impact gloves, overalls, and vests for worker protection.
4 .5. Safety Barriers and Signage: Installed to restrict access to the demolition site and ensure public safety.
4.6. Lamps, Fans, and Misters: Used to enhance visibility, control excess dust, and maintain a comfortable working environment.
4.7. Jackhammers (60 lb and 40 lb) with flat and point demolition chisels: Used to break apart the weakened rock, create cracks, and systematically demolish the structure.
4.8. Crowbars, picks, compressed air, and shovels: Essential for debris removal, including extracting large and small fragments from the site.
4.9. Skid Steer Loader: Used to transport debris and waste material to designated bins.
4.10. Surveying Equipment: Employed to assess site characteristics, determine the best demolition approach, and maintain a safe distance from walls and foundations.
4.11. Gasoline Flattener: Used To give a uniform finish to the terrain.
5. Demolition Methodology
Chronologically, the project began with the demolition of room b), followed by c) and a) (map 1), later a uniform surface was achieved to place a set of reinforcement frames and with this the weight of the construction was removed from the foundations in order to dismantle the walls and demolish the pillars on which they were located.
In general it was a reiterative process, firstly have to prepare and planning the demolition, then drill, pour the expanding grout mixture (Nexpro type II for 10°C to 25°C), wait for the cracks and open it through jackhammering and crowbars, then all the debris and weakened rock its removed and carried out in a bin (image 4).
Given the layout of the rooms and foundations, the geometry, hardness and structures of the rock mass, the procedure was as follows:
5.1. Project Planning: A survey was carried out to know the characteristics of the area and determine the best way to demolish and reach the level objective. Once identified it was limited to maintain from 1’ to 2´ of distance from walls and foundations to prevent structural damage to the home. Subsequently, the layer of concrete (2’’) and gravel (variable thickness) located on the rock mass was removed. Afterwards, the drilling template was traced with a quadrangular pattern of variable distance and according to the hardness of the rock; in the shear region (softer) from 1’ to 1.5’, in the chloritized basaltic andesite region (hard) 1’. and in silicic basaltic andesite region (harder) from 0.8’ to 1’.
5 .2. Safety Considerations and Preparations: Made sure all necessary safety measures were in place, including personal protective equipment (PPE) for workers like a half-mask respirator, safety glasses, earplugs, helmet, impact gloves, overall and vest; as well as security barriers and signage were placed to restrict access to the demolition site and protect the public, follow local codes and guidelines for safe demolition practices. Additionally, good lighting was placed, as well as fans and misters to keep excess dust controlled.
5.3. Drillhammering:
Drillhamers of 40 lb equipped with 1.5” bits and drillsteels from 2′ to 4′ long were used for create holes of same dimensions at angle of 90° (to achieve greater depth) and according to the drilling template.
5.4. Expanding Grout Application:
The expanding grout mixture (Nexpro type II for 10°C to 25°C) was prepared adding 1.5 L of water for bag of grout. Before pour the expanding grout into the pre-drilled holes it be cleaned the dust exceed with pressurized air and avoiding the moisture inside for better results. Once filled of grout the holes a heather and tarps were placed for maintain the temperature and speed up the process (from one day to another usually 1 to 4 days) to expand and exert pressure on the surrounding material, causing cracks and fractures.
5.5. Jackhammer Demolition: Firstly, the degree of fracture of the rock mass is evaluated through percussion tests or by hitting the rock to ensure it is effectively weakening the structure. If the rock is loose enough, it can be removed with the help of crowbars (image 11), otherwise (image 10) jackhammers were used 60lb and 40lb jackhammers were used , with flat and point demolition chisels as appropriate to open the cracks, apart the weakened structure and systematically breaking into manageable pieces and through the generated cracks by the expansion of grout (Nexpro type II for 10°C to 25°C) and the points of natural weakness of the rock.
5.6. Debris Removal and Waste Management: Once the rock mass is weakened and loose, the largest fragments are extracted with the help of crowbars and a pick, while the smallest fragments are extracted with compressed air, a pick and a shovel that will finally be transported in a skid steer loader to the bin for his recollection following established protocols and guidelines.
5 .7. Site Cleanup and Restoration:
When the required level its reached, the unevenness and demolished excess was back filled with gravel, to later flatten the land and leave a uniform surface. A thorough cleanup of demolition site was carried out, removing any remaining debris, dust or hazardous materials.
6. Conclusion & Recommendations
The Whistler demolition project faced significant challenges due to the hardness and complex composition of the volcanic rock, leading to an extended timeline for completion. The reiterative demolition process involved drilling, pouring expanding grout, jackhammering, debris removal, and site cleanup (in the image such a 50% progress is observed, while in the image such 100% progress, and in the map 2 the arrangement of the rooms with respect to the workplace is shown), that gave rise to a living space with an area of 719.1 ft2 and a perimeter of 117.8 ft. The silicified basaltic andesite zone proved to be the most difficult to break due to its exceptional hardness resulting from hydrothermal processes. To optimize grout expansion in pseudostratified (structure that separates this kind of rocks horizontally) volcanic regions, it is recommended to limit drilling depth to 2′, because when drilling to 3′ or 4′ there was a decrease in the generation of expansion fractures and to prevent grout seepage into natural cavities. Future projects should anticipate longer timelines when dealing with exceptionally hard rock formations, considering the potential need for reapplication of expanding grout. Close attention to safety measures, including appropriate personal protective equipment and effective dust control, remains paramount throughout the demolition process.
7 . Bibliography
-Cui, Y., Miller, D., Schiarizza, P., & Diakow, L.J. (2017). British Columbia digital geology. British Columbia Ministry of Energy, Mines and Petroleum Resources, British Columbia Geological Survey Open File 2017-8, 9p. Data version 2019-12-19. Obtained from: https://www2.gov.bc.ca/gov/content/industry/mineral-exploration-mining/british-columbia-geological-survey/geology/bcdigitalgeology
-Ospino, M. (2023). Hydrothermal Alteration Types. Obtained from: https://www.explorock.com/tipos-alteraciones-hidrotermales/
-Turner, B. (2021). Canadian Geoscience Education Network: Vancouver Rocks, obtained from: https://www.cgenarchive.org/vancouver-rocks.html
-Turner, R. J. W., Paige, J., Klassen, M. Quo Valdis, H., & Jensen, A. (2000). Vancouver Rocks: Geological Survey of Canada, Miscelanous Report 68, Obtained from: https://mineralsed.ca/site/assets/files/3451/vancouverrocksposter.pdf