Bryce Phelps
Design 040A Section 2
Christina Cogdell
December 1st, 2016
Life Cycle of Golden Gate Bridge Materials
All over the state of California exists classic landmarks that make the golden state the iconic image of success exploration and pushing the limits. From Yosemite, National Park being a shining example of environmental conservation to the Hollywood sign being a beacon to the dreamers chasing the American dream and fame, California has been a pioneer for big thinking and progress, but of all the landmarks and tourist attractions across the state none stand out more than that of the Golden Gate Bridge. The bridge connected San Francisco city to Marin county on 1937 after 4 years of construction. This civil engineering masterpiece, headed by Chief Engineer Joseph B. Strauss, created jobs for thousands of people, and took its place as one of the longest suspension bridges ever developed. However, a commonly overlooked aspect of the bridge is the level of painstaking effort that was put into assembling the materials to make the bridge. So, through a thorough life cycle analysis of the Golden Gate bridge’s materials, an understanding of the totality of efforts needed to create and maintain large civil engineering wonders. To maintain a main overview of the materials the life cycle will only cover the concrete, steel, and paint in the bridge in the initial construction and how it has changed over the years.
With any bridge, it is imperative that a foundation be set for the steel structural components of the bridge to set into. The material of choice for foundation setting in civil engineering projects is concrete. This is because of the astounding compressive strength that concrete possess. For the Golden Gate Bridge, concrete is used in the following places: the San Francisco pier and fender, the Marin pier, anchorages, pylons, cable housing, approaches, and paving. In the original construction of the Golden Gate Bridge a total of 389,000 cubic yards of concrete was used in developing the features of the bridge. With the importance of concrete for the building of the bridge an easy question to have is, “How is concrete made? And formed in bridge construction?”
Concrete is a composite of air, cement, coarse aggregate, fine aggregate, and water. Coarse and fine aggregate are the filler materials for concrete, and commonly consist of gravel, pebbles, stones, and sand. Aggregates can be natural or man-made; natural aggregate comes from pits, rivers, lakes, and sea beds; where as one example of man-made aggregate can be gravel coming from quarries. Cement is used as the binding agent in concrete and comes from raw limestone, clay, and sand. These three materials are harvested from quarries where the rock is blasted apart so that it may be transported into a crusher. The rock is then processed through a plant where they determine the proportions of all the elements that are needed to synthesize the cement. The large gravel pieces are then ground down to a fine powder. They are then heated and transported to a kiln where the chemical structure of the raw materials is changed into calcium silicates which is cements primary constituent; this new hot material is called clinker. After the heat treatment, the clinker is then cooled and ground into a fine powder and at this step Portland cement is now made.
With each of the components made the all need to be distributed to the site in which the actual mixing occurs. With large civil projects like the Golden Gate Bridge, contractors for the bridge had to buy the aggregate and Portland cement in bulk. The cement for the golden gate came from three companies: Cemex in Davenport, Ca, Monterey Portland Cement Company in Monterey, CA, and Permanent Portland Cement Company in Milpitas, CA. The cement was purchased by the barrel and shipped on trucks, whereas the aggregate was shipped by barge and then both cement and aggregate was mixed with water on site. After the concrete solution was synthesized, the concrete was poured into a mold with steel rebar that is laid in a grid. The steel is used as a skeletal structure to hold the concrete in place. After the concrete is set in place it is left to harden for a few days, but after it has been hardened for use, concrete eventually degrades and erodes and maintenance needs to be done on it.
In the entire history of the bridge, the only maintenance involving the bridges concrete was the removal of the cement paved deck of the bridge. This was done to the deck because the salt and moist air of from the ocean caused the concrete deck to deteriorate, thus a steel orthotropic deck was the choice to replace the old decrepit deck. Once the deck was removed, what most likely happened to the wasted concrete was that it was recycled and used as aggregate for more concrete somewhere else. Instead of dumping all the excess concrete in landfills, which was the common practice, the waste concrete was instead trucked to a processing facility where the wasted concrete was crushed into aggregate to be used in more concrete for another project.
After the laying of the concrete the Steel structure must be erected and the cables strung across the towers. About 83,000 tons of steel was used on the bridge where it was used in a multitude of ways. The main areas that had steel were the main towers, suspended structure, anchorages, and approaches. For simplicity, the main steel will be covered will be that of the towers, the suspended structures, and the steel cables. Though these three items are different in function they all share common origin.
All steel is made of iron and carbon and other alloyed elements. And for Bethlehem Steel, the steel contractor for the towers and suspended structure, their iron ore came from Grace Mine in Berks County, PA. Due to the close location of the iron ore mine made it ideal to deliver the ore by truck or train. The carbon for the steel comes from the co*ke that is developed to be an additive in the steelmaking process. The manufacturing process performed on the steel pieces used were varied based the part of the bridge the steel was developed for. The two towers are made of steel plates that were casted to achieve their shape. Each plate was maneuvered into place and then riveted. This process was repeated over and over till they achieved the full tower height of 746 ft. The I beams used to create the truss took 3 rolled steel bars, one in the center and smaller widths sections on the sides and welded them on either side which is typical for I beam fabrication. Once the different I beam sections were fabricated they were assembled to create the interlocking truss system for the super structure. Construction teams started on either side of the bridge assembling each section one beam at a time until the eventually met in the center over the strait. Lastly, the cables are made of many parallel steel wires that are eventually wrapped with a galvanized steel wire. The steel wires are made by the same process as each other which is an extrusion process. The hot steel is pushed through a circular die and then is fed around a spindle as it is cooled. Since most of the steel was manufactured on the east coast a form of transportation obviously needed to be used to travel the great distance the construction site. From primary material acquisition to the construction site, a combination of train, truck and boats were used in transporting the material from the east coast to the west coast. For the steel made by the Bethlehem Steel Corporation, their steel was delivered by train to the Philadelphia, PA docks where it was placed on a ship. The ship then traveled from Philadelphia to Almeda, CA where another branch of the company was stationed. The steel was then trucked and barged to the construction site of the bridge.
The maintenance involved for the steel parts of the bridge predominantly lie in the paint which will be discussed further soon, but one steel item that needs replacing from time to time are the steel rivets that hold the larger steel members together. Rivets are removed by drilling them out of the holes that they fasten. And then replaced with brand new rivets. Assuming they are recycled any paint that is on the waste rivets will have been removed and dealt with as will be mentioned later. Then the rivets themselves will be melted down and used in making more steel for other projects. If the rivets do not get recycled, then typically most construction material tends to be discarded to landfills once they are of no use. Another interesting form of recycling that was found is that a company by the name of Golden Gate Furniture develops furniture out of old pieces of the steel that are removed from the bridge.
The most iconic piece of the bridge is the vibrant international orange color. The painting of the bridge was a length process that has not stopped even till today. Not a lot of information is available on the original paint other than it was lead based and needed to be replaced by 1968, but apparently, the modern-day paint is manufactured by Sherwin Williams and can be only be purchased in bulk.
Not too much is known about the individual ingredients of the raw materials but what can be said is that the original paint was lead based. While the newer paint that replaced it was a zinc silicate based paint. Both the lead and the zinc in the paints are used as sacrificial materials to be eroded rather than the steel underneath. But if the only special part about the paint is its specific use in protecting the bridge, all paints consist of resins, solvents, additives, and intermediates. Throughout the process of creating the paints they will be like all other paints developed. The mixer that is used is usually a cylindrical vessel that has a machine that is attached and mixes the contents of the vessel. Step by step different parts of the ingredient are added till the right proportion of them creates the desired color with the expected properties. Once made the paint will be stored in barrels or buckets depending on its use. Since the paint for the golden gate bridge is purchased in bulk the paint will most likely have been kept in barrels and then trucked to the site of the bridge.
The maintenance for the paint is extensive. Averaging roughly 5,000 gallons to 10,000 gallons a year used. The painting crew continuously inspects the bridge for signs of corrosion and paint flecking. When an area has been identified as a place that needs painting the old paint is blasted off with a light abrasive or scraper. Once old paint is removed new paint is applied to the area; first the primer is applied then a top coat is applied after. For paint costs alone, the average fiscal year expected cost is about $20,412.64. The problem with paint is that it is not recyclable since the paint that is used for the bridge contains many hazardous materials like lead in the original paint and other harmful dangerous chemicals in the new paint. Since the both paints can’t be recycled they get taken to treatment-storage-disposal facilities and are made non-hazardous by applying other chemical additives that depend on the material they are trying to make inert. After the materials are no longer a problem they will be trucked to landfills where they will be stored.
Every step of developing a bridge of this size is a large undertaking. As shown many materials must be accumulated and processed into their final materials. But not only are careful designs made in the acquisition and fabrication of these main materials, but there are also transportation and waste management methods need to be designed to handle when sections of the bridge may degrade or possibly fail. As there are many facets to take into consideration for the design process of the bridge it is important to be aware that it took many minds and efforts to organize and construct the Golden Gate Bridge.
Bibliography
“Aggregates”, Portland Cement Association, 2016, <www.cement.org/cement-concrete-basics/concrete-materials/aggregates>. Accessed 1 Dec. 2016.
"American Experience: TV's Most-watched History Series."PBS. PBS, n.d. 2016. <http://www.pbs.org/wgbh/americanexperience/features/general-article/goldengate-spinning/>. Accessed 1 Dec. 2016
Anika, “The Maintenance of the Golden Gate Bridge”, Fog city, 7 Sept. 2015, <www.fog-city.co/the-maintenance-of-the-golden-gate-bridge/>. Accessed 1 Dec. 2016.
Building the Golden Gate Bridge. Prod. Bethlehem Steel.Archive. Golden Gate Bridge District, n.d. <https://archive.org/details/0808_Building_the_Golden_Gate_Bridge_05_01_00_00>. Accessed 1 Dec. 2016.
"From Ore to Steel."ArcelorMittal. ArcelorMittal, n.d.<http://corporate.arcelormittal.com/who-we-are/from-ore-to-steel>. Accessed 1 Dec. 2016.
"Golden Gate Bridge Research Library."Golden Gate Bridge. Golden Gate Bridge Highway &Transportation District, 2015. <http://goldengatebridge.org/research/>Accessed 1 Dec. 2016.
Hinz, Christopher. "Grace Mine: Working up to 3,000 Feet Underground."Reading Eagle Reading, PA. Reading Eagle, 8 May 2007. <http://www2.readingeagle.com/article.aspx?id=54101>. Accessed 1 Dec. 2016.
“History Of Concrete Recycling In Sacramento”, GR Trucking, 16 July 2014, <grtrucking.net/sacramento-aggregate-material-transport/history-concrete-recycling-sacramento/>. Accessed 1 Dec. 2016.
Hopwood, Theodore. "The removal of Lead-Based Paint from Steel Bridges."UKnoledge, Kentucky Transportation Cabinet, Jan. 1993,<uknowledge.uky.edu/cgi/viewcontent.cgi?article=1600&context=ktc_researchreports>. Accessed 1 Dec. 2016.
How Concrete is Made, Portland Cement Association, 2016, <www.cement.org/cement-concrete-basics/how-concrete-is-made> . Accessed 1 Dec. 2016
Lambourne, R, and T A. Strivens.“Paint and Surface Coatings: theory and practice.” seconded., Cambridge, Woodhead Publishing, 1987. <https://books.google.com/books?hl=en&lr=&id=cRKkAgAAQBAJ&oi=fnd&pg=PP1& dq=paint+manufacture+process&ots=QfBbW9aMX8&sig=c7NpL0bV9ro2K9HjG7imRS llKk8#v=onepage&q=paint%20manufacture%20process&f=false>. Accessed 1 Dec. 2016.
Ludke, Richard. "The Golden Gate Bridge Art Deco Suspension Bridge Masterpiece."The Golden Gate Bridge Art Deco Suspension Bridge Masterpiece - Structures Congress 2013 (ASCE). American Society of Civil Engineers, 2013. <http://ascelibrary.org/doi/pdf/10.1061/9780784412848.051>.
Metcalfe, John. "The Fascinating, Never-Ending Job of Painting the Golden Gate Bridge."CityLab, The Atlantic, 15 Apr. 2015, <www.citylab.com/work/2015/04/the-fascinating-neverending-job-of-painting-the-golden-gate-bridge/390453/>. Accessed 1 Dec. 2016.
Snyder, Michael T.“Golden Gate Bridge has roots in Pottstown”, The Mercury, 7 May 2012, <www.pottsmerc.com/article/MP/20120507/LIFE01/120509548>. Accessed 1 Dec. 2016.
Stamberg, Susan.“The Golden Gate Bridge's Accidental Color Listen”, NPR, 26 Apr. 2011, <www.npr.org/2011/04/26/135150942/the-golden-gate-bridges-accidental-color.Accessed 1 Dec. 2016>.
Tam, Vivian W. "Economic comparison of concrete recycling: A case study approach."Resources, Conservation and Recyciling, vol. 52, no. 5, 2008, pp. 821-28. Accessed 1 Dec. 2016.<www.sciencedirect.com/science/article/pii/S0921344907002248>
"The Company."Golden Gate Furnituregoldengatefurniture.com/company. Accessed 1 Dec. 2016.
STEPHEN SUCHESKl
998361097
DES 40A Cogdell
The Golden Gate Bridge- Embodied Energy
Introduction
The Golden Gate Bridge is an icon of the United States of America, California, and San Francisco in particular. While some people think of the Golden Gate as simple tourist attraction what is rarely thought of is the energy embodied in the entire life cycle of the bridge. Embodied energy is a summation of all the energy consumed by intermediate processes from beginning to end for a product. For many of us the Golden Gate has been standing our entire lives, and the actual construction of the bridge doesn’t come to mind, however we could see the end of the Golden Gate Bridge, thus the dismantling and recycling of the Bridge could take place in our lifetime. In this report, I will present a life cycle assessment of three main components of the bridge, the steel, the concrete, and the paint. This life cycle assessment of the Golden Gate will highlight the energy embodied in each step of the materials use from when they gathered, to when they were used in construction and continued maintenance of the bridge. From this we will gain a general idea of which stage of the Bridge’s life had the largest impact on the environment and required the most energy. I will also extrapolate as to how much energy might be necessary to take down the bridge by comparing the Golden Gate to other suspension bridges. From raw material extraction to the eventual destruction of the Golden Gate, I will present my findings on the energy that is embodied in each step of the Bridge’s life.
Raw Materials and Processing-
The first step in any product life cycle is, the harvesting of the raw materials to be processed into secondary materials. Of the three components analyzed, concrete was the most abundant by weight with 788,000 tons poured during the construction (Golden Gate Transportation District). The bridge’s foundations in both the land and sea were made from concrete as well as the providing structure on the steel spans for the road. The embodied energy in the harvesting and creation of concrete, is primarily thermal, mechanical and chemical energy. Concrete is can be made from different formulas but a common one is comprised of 41% gravel, 10% cement, 25% sand, 6% air, and 18% water (Penttala). Cement is the key ingredient because it acts as the bonding agent to harden concrete after it is poured. Cement is made up of a few different raw materials (limestone, sand, clay) and then processed by being baked and pulverized until correct consistency is met (Portland Cement Association). Studies on how much energy all these processes use to make cement have estimated that it takes about 1.4 GJ (giga-Joule) per ton of regular concrete and 2.5 GJ per ton of reinforced concrete (Penttala). Therefore, I estimate it took about 1,970,000 GJ of energy to make all the concrete for the Golden Gate. I used 2.5 GJ per ton because a mix of both were used in construction and these are more modern studies as well so the actual efficiencies could have been worse in the 1930’s.
Steel is the second most abundant material by weight and volume, where over 83,000 tons of steel have been used in the construction and maintenance. Steel is used in the bridge span, the towers, the cables, and all the rivets that connected these pieces together (Golden Gate Transportation District). The embodied energy that goes into gathering and processing the raw materials for steel is primarily thermal, chemical, and kinetic energy. Machines first mine for taconite ore containing iron, the key ingredient in steel (ArcelorMittal). These machines expend lot of kinetic energy during the grinding and removing of rock while being powered by fossil fuel engines which embody chemical energy. Finally, the iron is separated and melted in a furnace that embodies a lot of thermal energy (ArcelorMittal). The same studies from earlier estimate that the production of a ton of steel costs 30 GJ, totaling about 2,490,000 GJ of energy to produce all the steel (Penttala).
There is 10 million square feet of space that need to be painted on the Golden Gate continuously to prevent corrosion from destroying the steel (Stamberg). Painters need to be continuously reapplying paint throughout the year to make sure rust and corrosion don’t deteriorate the steel. The embodied energy that goes into making the paint is again thermal, kinetic, and chemical energy. The raw materials of paint are rocks, minerals, resins, solvents, water, and other various additives. These are mined and transported to a plant via kinetic, mechanical, and chemical energy being consumed by the machines (Advameg). After the constituents are mixed to the desired amounts they are placed in an oven to be treated and then 33mixed with the liquid agents that make them applicable. Although I could not find an exact amount on the energy cost per gallon of paint, I did find, for each gallon of paint recycled will save “An estimated 100 kilowatt-hours (kWh) of energy” (EcoCoat) or 0.360 GJ of energy. If this is the cost of production for each gallon and one gallon covers about 250 square feet, we can extrapolate that at least 40,000 gallons needed each time the Golden Gate is painted, 14,400 GJ per paint job.
Transportation-
After the materials were made they needed to be transported to San Francisco to be installed. The embodied energy that is associated with the transportation of the materials is almost all chemical energy. A company by the name of Bethlehem Steel in Pennsylvania manufactured and shipped the steel to California (Golden Gate Transportation District). The steel was transported via cargo ships that went from the docks on the east coast through the Panama Canal and into San Francisco Bay (Golden Gate Transportation District). The ships used fossil fuel diesel engines that are powerful and relatively efficient but embody a lot of energy. Based on the weight for how much steel was used, the density of steel, and the standard ship size, I calculated that all the steel for the Golden Gate would fit in a ship size of less than 1000 TEU (TEU= 39m^2) (LogisticGallery). This ship moving at 19 knots would arrive in San Francisco in about 10 days using about 65 tons of fuel a day. That totals about 710 kL of diesel fuel, and 25,414 GJ of energy stored in that fuel (EngineeringToolBox). Although this number is large the cost only happens once and per ton of steel it is less than the gathering and processing costs.
For the concrete and paint, I assumed most was transported by train and then truck to the construction sites. It was difficult to find the exact manufactures of the paint and concrete for the Golden Gate so it was hard to get the same embodied energy numbers like I did for the steel transportation. I am assuming because paint and concrete are made from common materials bought all over the world that they didn’t need to go as far for them and hence less energy. But because concrete was probably mixed on site (cutting down on cost) and there was so much concrete it had to be comparable amounts of energy to transport to the site as to the steel.
Construction-
The actual construction of the bridge took over four years but its unclear on how many people worked on the project at any given moment (Golden Gate Transportation District). The energy embodied during the construction was kinetic, thermal, electrical, chemical, and animate to power all the machines, ships, trucks, and workers used to assemble and transport the and parts of the bridge. Initially the foundations were built on both sides of the bay and a pier was made to access the tower foundations in the middle of the ocean. Kinetic and chemical energy was embodied in the removal of all the rock and sea bed, for the foundation of the anchorages and towers in the middle of the bay. They often used dynamite (chemical) and other crude but effective ways of removing chunks of land (PBS). Chemical energy was embodied in the boats, trucks, and machines that helped lift and move materials for the workers. Finally, thermal and electrical energy was embodied in all the welding and riveting of the entire structure. The amount energy exactly associated was very hard to extrapolate on though. The numbers of machines and workers was not well documented across all the contracts used in during the construction of the Golden Gate so coming up with estimates would be a little difficult. What I can assume is that this part of the life cycle embodies less energy, as there are fewer processes taken place and much of the work was animate, or done by humans. The amount of energy expendable by human force is not as great as the amount of energy used by fossil fuel machines to gather, produce, and transport the resources.
Maintenance-
Maintenance of the of the Golden Gate is a constant process but does not require a lot of labor. A crew of 33 painters and 16 iron workers continuously repair and monitor the bridge (Golden Gate Transportation District). Most of the embodied energy goes into chemical energy as new materials are made for the continual maintenance of the bridge. As mentioned earlier the painting is a continual process, where surveyors inspect the bridge and make note of places where the steel is corroding. 40,000 gallons of paint are needed each time and as we know there is a lot of embodied energy in the harvesting and processing of paint primary materials. Other maintenance projects like surveying and replacing corroded bolts, and support cables, are done on an as needed basis and systematically to prevent an accident but embody chemical, thermal, and mechanical energy in the production and replacing of said parts.
Recycling and Waste Management-
Lastly in the event of the destruction or necessary removal of the Golden Gate, its pleasant to know that almost all the materials are recyclable (SteelConstruction.info). Experts have stated that one ton of steel recycled saves about 10.9 million BTU’s of energy or about 11.5 GJ per ton (Stanford). That is a third of the construction costs, so every three tons of recycled steel produces one ton of new steel and other aggregates. Concrete is recyclable and embodies chemical energy to remove and transport the concrete to the recycling center. Here it is crushed and separated to be remade into cement and other components. Sometimes it even gains desirable quality in cement (PCA). Current projects to take down bridges of similar age have been successful. Looking across the bay we can see a prime example of how they are dismantling and recycling the old Bay Bridge at this moment (Smillie). But recycling isn’t free and this project is costing $240 million dollars and is embodying tons of chemical and thermal energy when using all those machines to dismantle and re-melt the steel.
Although the paint is not recycled and mostly deteriorates until a reapplication is needed, there was a project that focused on recovering the paint on the Golden Gate. In the 1970’s they had a project that took nearly thirty years to remove all the lead paint that was initially applied, while applying a new coat of less toxic paint (Golden Gate Transportation District). The environmental impact of all the lead paint left over has not yet been fully explored but we know they have detrimental effects to human health.
Conclusion-
Over all the Golden Gate Bridge was a massive feat of human engineering. The project brought together people of all backgrounds to come together and build something remarkable. The energy associated with each step in the bridge’s life has been laid out, and after seeing it from this perspective it’s interesting to see how much more energy went into the production of the secondary materials used in the construction rather than the construction itself. Although we might gaze upon the Golden Gate today and think of its beauty, its truly baffling to think about the embodied energy that went into creating such a historic landmark.
Bibliography
Raw Materials and Processing
Advameg, Inc. "Paint."How Products Are Made. Advameg, Inc., n.d. Web. 27 Nov. 2016. <http://www.madehow.com/Volume-1/Paint.html>.
ArcelorMittal. "From Ore to Steel."From Ore to Steel. ArcelorMittal, 2016. Web. 27 Nov. 2016. <http://corporate.arcelormittal.com/who-we-are/from-ore-to-steel>.
EcoCoat. "Additional Links and Information."EcoCoat - Additional Information. EcoCoat, 15 Apr. 2016. Web. 27 Nov. 2016. <https://www.ecocoatpaint.ca/additional-links-and-information>.
"Golden Gate Transportation District."Golden Gate Transportation District. Ed. Julie Vetter and Hoi Moon Marketing. Golden Gate Bridge, Highway and Transportation District, 2015. Web. 27 Nov. 2016. <http://goldengatebridge.org/>.
"How Cement Is Made."How Cement Is Made. Portland Cement Association, 2016. Web. 27 Nov. 2016. <http://www.cement.org/cement-concrete-basics/how-cement-is-made>.
Penttala, Vesa. "Concrete and Sustainable Development."Polysteel.com. ACI Materials Journal, Oct. 1997. Web. 27 Nov. 2016. <http://www.polysteel.com/Green_page/Website%20Docs/Concrete_and_Sustainable_Development.pdf?lbisphpreq=1>.
Stamberg, Susan. "The Golden Gate Bridge's Accidental Color."NPR. NPR, 11 Apr. 2011. Web. 27 Nov. 2016. <http://www.npr.org/2011/04/26/135150942/the-golden-gate-bridges-accidental-color>.
Transportation
LogisticGallery. "TEU."Logistics Glossary. Logistic Gallery, 2016. Web. 27 Nov. 2016. <http://www.logisticsglossary.com/term/teu/>.
Penttala, Vesa. "Concrete and Sustainable Development."Polysteel.com. ACI Materials Journal, Oct. 1997. Web. 27 Nov. 2016. <http://www.polysteel.com/Green_page/Website%20Docs/Concrete_and_Sustainable_Development.pdf?lbisphpreq=1>.
EngineeringToolBox. "Engineering ToolBox."Engineering ToolBox. N.p., n.d. Web. 29 Nov. 2016. <http://www.engineeringtoolbox.com/>.
Construction
"Golden Gate Transportation District."Golden Gate Transportation District. Ed. Julie Vetter and Hoi Moon Marketing. Golden Gate Bridge, Highway and Transportation District, 2015. Web. 27 Nov. 2016. <http://goldengatebridge.org/>.
PBS. "Men Who Built the Bridge."PBS.org. PBS, 2013. Web. 27 Nov. 2016. <http://www.pbs.org/wgbh/americanexperience/features/biography/goldengate-workers/>.
Maintenance
"Golden Gate Transportation District."Golden Gate Transportation District. Ed. Julie Vetter and Hoi Moon Marketing. Golden Gate Bridge, Highway and Transportation District, 2015. Web. 27 Nov. 2016. <http://goldengatebridge.org/>.
Recycling and Waste Management
PCA.Concretethinking.com. PCA, n.d. Web. 27 Nov. 2016. <http://www.concretethinker.com/solutions/Recyclable.aspx>.
Smillie, Eric. "The Dangerous Art of Tearing Down Bridges, Dams, and Aircraft Carriers."Wired.com. Conde Nast Digital, 17 Dec. 13. Web. 27 Nov. 2016. <https://www.wired.com/2013/12/demolish-the-bay-bridge/>.
Stanford. "Buildings & Grounds Maintenance."Frequently Asked Questions: Benefits of Recycling | Buildings & Grounds Maintenance. Stanford Building & Ground Maintenance, n.d. Web. 29 Nov. 2016. <http://bgm.stanford.edu/pssi_faq_benefits>.
SteelConstruction.info. "Sustainable Steel Bridges."Steelconstruction.info. TATA Steel, BCSA, Steel For Life, n.d. Web. 27 Nov. 2016. <http://www.steelconstruction.info/Sustainable_steel_bridges>.
Sze Ling Liu
Professor Cogdell
DES 40A
11/30/2016
Waste and Emissions of the Golden Gate Bridge
The Golden Gate Bridge is a famous tourist attraction in San Francisco, California. It is a suspension bridge that was built in 1937. The main materials used in building the Golden Gate Bridge include concrete, steel and paint. During the production of those materials, some waste and emissions are also produced that bring impact to the environment. This life cycle assessment will be discussing the waste and emissions produced during the six steps in the life cycle of the Golden Gate Bridge.
In the process of raw materials acquisition, air and water emissions occur. One main raw materials used in the production of concrete is cement. Raw materials needed for the production of cement are extracted by quarrying in the case of hard rocks such as limestones, slates, and some shales, with the aid of blasting when necessary. Some deposits are mined by underground methods. Softer rocks such as chalk and clay can be dug directly be excavators [1].The extraction of those raw materials result in dust and machine emissions [2]. Iron is the raw material for steel production. Most iron ore is extracted through opencast mines[3] and mining causes air pollutions[4]. The process of extracting iron from haematite releases carbon dioxide that contributes to the greenhouse effect, carbon monoxide which is poisonous and sulfur dioxide which is also poisonous and causes acid rain[5]. In addition, extraction of iron from haematite also create large amount of waste produced by ore mills and slag[6].
The manufacturing, processing and formulation of concrete, steel and paint all create some sort of air emissions, water emissions and solid waste. For the production of concrete, a huge amount of carbon dioxide is produced. Cement production is the third ranking producer of man-made CO2 in the world after transportation and energy generation and 4-5% of the worldwide total of CO2 emissions is caused by cement production [7]. The carbon dioxide emissions during the cement production come from two sources. The first one is from the combustion of fossil fuels to operate the rotary kilns which produces approximately ¾ tons of CO2 per ton of cement [8]. Another source of CO2 is from the chemical process of calcining limestone into lime in the cement kiln. This chemical process produces approximately 1/2 ton of CO2 per ton of cement. Combining these two sources, for every ton of cement produced, 1.25 tons of CO2 is released into the atmosphere [9]. In addition, cement production also result in air-pollutant emissions such as dust. The U.S. EPA estimates total particulate (dust) emissions of 360 pounds per ton of cement produced. Other sources of dust include handling raw materials, grinding cement clinker, and packaging or loading finished cement, which is ground to a very fine powder--particles as small as 1/25,000 of an inch.[10]. The production of cement also result in water emissions. One problem with the concrete production is that it releases wash-out water with high pH as high as 12. Production of cement also creates solid waste. Concrete accounts for up to 67% by weight of construction and demolition waste, with only 5% currently recycled[11].
The manufacturing of steel also create air emissions including carbon dioxide, nitrogen oxides, Sulphur dioxide and dust. A large amount of carbon dioxide comes from several sources: from iron reduction that takes place in blast furnaces and sponge iron plants, production fluctuations of ore-based steel and also the use of fossil energy to generate heat[12]. Air emissions also come from the co*ke production. co*ke oven releases air emissions including co*ke oven gas, naphthalene, ammonium compounds, crude light oil, sulfur and co*ke dust[13]. Nitrogen oxides is produced mainly in co*king plants, electric arc furnaces, reheating and heat treatment furnaces. The formation of nitrogen oxides is unavoidable during the fuel combustion process because high temperatures are necessary within the iron and steel industry[14]. Emissions of sulphur dioxide during the steel production come from the combustion of oil, above all in reheating furnaces and for co*ke production[ 15]. The steel production also result in dust and water emissions. Water is used to cool co*ke after it finishes baking and quenching water becomes contaminated with co*ke breezes and other compounds[16].
The manufacturing of paint create air and water emissions. Titanium Dioxide is a component of making paint. It can be produced in two ways which both have significant environmental impact. Emissions during manufacture of Titanium Dioxide are CO2, N2O, SO2, NOx CH4 and VOCs. There are also a lot of waste streams such as spent acid and metal sulfates, emanate from the manufacturing process that all have environmental impact [17].The production of paint also leads to emission of volatile organic compounds(VOCs), heavy metal dusts from pigments and particulate matter emission. Moreover, the paint production also result in wastewater that contains solvent, heavy metals, and other toxic materials[18].
Air emissions occurred in the distribution and transportation. For the concrete, dust is generated during the transportation. Common sources are sand and aggregate mining, material transfer, storage (wind erosion from piles), mixer loading, and concrete delivery (dust from unpaved roads) [18]. Air pollutions also result from burning fossil fuels for transportation use.
The use of the paint also creates air emissions. Organic solvents used in paint have a large amount of Volatile Organic Compounds, VOCs. In California’s emission profiles, it is suggested that 9% of all VOC emissions is from coating [19]. VOCs have high enough vapour pressures so that they can vaporize into the atmosphere. In addition, when nitrogen oxide, VOCs and carbon monoxide react in the atmosphere in the presence of sunlight, ozone is formed[20].
VOCs can be emitted during the application and the time periods afterwards. VOCs can also affect health. It is suggested by The American Lung Association that VOCs can cause some physical problems including eye and skin irritation, lung and breathing problems, headaches, nausea, muscle weakness and liver and kidney damage[21]. Also Many metal pigments used in paints such as cadmium are highly toxic. There are impacts of paint on both health and the environment.
Both concrete and steel can be recycled. The process of recycling concrete involves breaking, removing and crushing concrete to make it into specific size and quality. The process of crushing refers to the use of large powerful crusher to turn the concrete into pieces. In this process, dust can be generated and result in air pollution. Steel can also be recycled. Iron and steel are both easy materials to reprocess by separating magnetically from the waste stream. 42% of crude steel produced is recycled material [22].
During the steel production, some solid wastes mainly are co*ke and co*ke dust, slag, mill scale, scrap, oil sludge, fly ash, acid sludge and refractory wastes[23]. Some of the wastes can be reused again. For example, in the sinter making, some solid wastes generated such as dusts and sludges are rich in iron and contain lime, magnesia and carbon which are good materials for recycling back in sinter making. The major solid waste in steel production, blast furnace slags, are used in the production of cement, road base, light weight concrete block[24].For the waste management of paint, some of the waste generated are aqueous liquids and solvents, liquid wastes from equipment cleaning and scrubber water. The cleaning solvent, rinse water and alkaline cleaning solution during the process of producing paint can be recycled and reused[25].
From the life cycle assessment of the main materials used in building the Golden Gate Bridge, it shows that from the process of raw materials acquisition to the manufacturing and transportation, air emissions, water emissions, solid waste are generated.
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