Project ID: GFS-2002 The Design and Construction of the Wachusett Dam: Contractor’s Perspective and Contemporary Considerations A Major Qualifying Project Report Submitted to the Faculty of Worcester Polytechnic Institute In Partial Fulfillment of the Requirements for The Degree of Bachelor of Science By: Emma Fields Rebecca Johnson Julia Saldanha Advised By: Paul Marrone Gillermo Salazar March 25, 2020 Abstract The Wachusett Dam is located in Clinton, Massachusetts, and was constructed beginning in 1895. This project reviews the original construction of the dam as documented in archival photographs and reports. It also develops the construction schedule for the work directly managed by the contractor who took responsibility after October 1, 1901. It then analyzes the productivity of modern plant and equipment supporting construction operations and compares the results with the ones observed more than 100 years ago. The design of the dam’s structure is also reviewed. II Acknowledgments We would like to thank everyone who assisted our team throughout the course of completing our MQP (Major Qualifying Project). We would like to thank our advisors Professor Paul Marrone and Professor Guillermo Salazar for taking their time to guide us week after week with understanding and knowledge. We would also like to thank Professor Mingjiang Tao for his direction and guidance on the capstone design portion of our project. We would like to thank the West Boylston Historic Society for inviting us to present some of the details of our project for its members. In addition, we would like to thank the Department of Conservation and Recreation (DCR), the Massachusetts Water Resource Authority (MWRA). Finally, we’d like to thank Ranger Andrew Leahy, from the DCR, and Mr. John Gregoire, from the MWRA, who on separate occasions, both escorted us across the walkway of the Wachusett Dam which is closed to the general public. Mr. Gregoire also allowed us to enter the out-of-commission powerhouse structure while sharing more knowledge of the Boston Water System with us. III Executive Summary Figure 1: The Wachusett Dam and Pool The Wachusett Dam in Clinton, Massachusetts was constructed between 1895 and 1905 as an extension of the Boston Water System. This dam was conceptualized and built more than 100 years ago in an attempt to meet the growing water needs of the expanding city of Boston after the development of plumbing and the sanitary sewer system in the late 1850s (Boston Standard, 2013). The goal of this project was to develop a deeper understanding of the practices used to construct the Wachusett Dam compared to today’s methods. To accomplish this goal, the following objectives were completed: (1) Recreation, to the best possible degree, of the original construction schedule of the Wachusett Dam, (2) Analyzation of the productivity of modern plant and equipment supporting construction operations and compared the results with the ones observed more than 100 years ago and (3) Review of the structural design of the Dam to better understand the implications of the design on the construction methods. The objectives were completed by reviewing the Annual and Engineering Reports of 1900 to 1906, photos taken during the original construction, research of modern practices, and research of retaining wall design. Additional resources included trips to the Wachusett Dam, interviewing staff from the Department of Conservation and Recreation (DCR) and the Massachusetts Water Resource Authority (MWRA), and consulting with Professor Mingjiang Tao, a WPI faculty member from the Department of Civil Engineering. IV Using the Annual Reports, the original construction schedule of the Wachusett Dam was determined, from the point in time when the contractor took over the excavation of the site until the masonry of the Dam reached the height of the waterline. The duration of each major activity was determined, along with the total duration of all activities being from October 11, 1900, until April 11, 1903. Using the knowledge of the original construction, modern construction practices for Dams were researched. A fleet of equipment was chosen and activities were compared to the original activity durations. Every activity duration that was analyzed for the present-day schedule was significantly shorter than the original duration. Lastly, the structural design of the Wachusett Dam was reviewed to quantify the extent of its structural integrity and to better understand how it has been standing and operating successfully for more than 100 years. The chief engineer for the Wachusett Dam, Frederic P. Stearns, designed the Dam with a “very large” factor of safety to minimize the risk of failure. The factor of safety against overturning, which is the most probable way the dam would fail, was found to be about 5.5 (more than double the minimum requirement of 2). All three of the original deliverables were ultimately accomplished. These objectives enhanced the knowledge in relationships between activities, scheduling in primavera, interpersonal skills, modern equipment, and the structural design of Dams. They ultimately allowed for relationships between construction activities to be better understood, for past and present interpretations of the Wachusett Dam construction schedule of events to be created. The review of the dam’s design ultimately revealed a high factor or safety, which confirms the dam’s ability to continue standing more than 100 years after it was originally constructed. In completing these objectives soft skills of critical thinking, problem-solving, dependability, and teamwork through the various tasks and deadlines we were required and developed. These skills will continue to be useful throughout our careers and professional lives. Recommendations were made that the next Major Qualifying Project team either continue the scheduling process up until the last rock is placed, recreating the rest of the original schedule using modern equipment and practices, construction of the spillway, construction of a section on the CMRR realignment from the North Dike to the tunnel at Clamshell, or creating a cost analysis of the modern equipment used in the Plant and Equipment and compare it to the original cost of the project. For a longer-term project, it could include stripping the basin soil and constructing the dikes. V Capstone Design Statement The Wachusett Dam was designed and constructed over 100 years ago. The understanding of the engineering concepts of the 19th century were very limited in terms of applied science, experimentation, and computational mechanics. They did not have the benefit of the advances in these areas attained since then. Therefore, design and construction practices at the time incorporated experience and sound and conservative engineering judgment in their approaches. The fact that the Wachusett Dam today stands structurally safe and functional after more than 100 years provides a meritorious testimony of their approaches. The capstone design objective was to conduct static analysis of the dam to prove its structural integrity. This report conducts a design review of the Wachusett Dam structure as a retaining wall. In conducting this review the weight of the Dam was calculated, as well as the pressure on both the upstream and downstream sides of the dam, the various depths (of the water, of the toe slab, and of the toe), and the resisting and overturning moments. The weight was calculated using the Engineering Report of 1905. In the report the materials used were identified along with the total volume of each material. Using this information, the density of each material could be multiplied by the total volume to get the weight. The necessary dimensions of the dam were also found in a cross-sectional drawing of the Dam from the Engineering Report in 1900. The other values (pressures and moments) were calculated using the given weight and dimensions. All of these values could then be used to determine the factor of safety against sliding and against overturning. A high enough factor of safety would prove the stability and structural integrity of the dam. In accomplishing this capstone design, several realistic constraints were addressed. The following constraints are addressed below: economic, environmental, social, and health & safety. Economic: The construction schedule and operations and their corresponding economic implications were analyzed in detail. Scheduling is an important part of any construction project as delays can affect the economics. Environmental: The creation of a dam does change the ecosystems of the surrounding environment. However, after the operation of a dam begins, the uses allowed surrounding the VI dam is highly regulated and protected. Therefore, the positive impact on the surrounding environment tends to outweigh the negative. Social: The Dam was created to serve the Boston Metropolitan people with enough clean drinking water for their growing population. A static analysis ensures a minimal risk of failure, which means that no one will be without enough water. Health & Safety: A static analysis is an essential part of the construction of any structure. It ensures a minimal risk of failure, which is necessary in ensuring the safety of nearby residents. VII Professional Engineering Licensure In the United States of America, Civil Engineering Professional Licensure is governed by the state in which the engineer is practicing and is obtained after fulfilling certain requirements and passing an exam. The license represents ability, trust, and achievement (NSPE, 2019). The license provides a means to earn clients’ trust and demonstrate one’s capabilities as a practicing engineer. For an engineer it also illustrates one’s achievements in their professional career and why the engineer deserves respect. Civil Engineers are required to be licensed, unlike other types of engineering, because Civil Engineering directly impacts the safety and wellbeing of the public (Kumar, Mattei, Musselman, & Smith, 2016). To become a Civil Engineer, one must pass the Principles and Practices of Civil Engineering (PE) Exam. One qualifies to take the exam after working under a licensed Civil Engineer for 5 years.