A Boiler Plant Upgrade's Tough College Course
Here’s a task: bridge the new mechanical room to the utility connection in the old space - located in an adjacent building in Chicago’s South Loop. Room for equipment is frequently tight, but in the case of this steam pipe, the room for error was less than one inch. The kind of planning that navigated that challenge accounted for (almost) everything in this tricky retrofit.
When it was time for the historic college campus to upgrade its infrastructure, Columbia College worked with McGuire Engineers to install a new, efficient boiler plant to replace its aging system. McGuire and Columbia worked together closely to design an approach that would minimize disruption to campus activities as well as identify potential problems that would drive up cost or extend the project timeline. With careful planning, extensive collaboration, and 3-D modeling, the team was able to design a new boiler plant and work through few surprises that are inevitable in a turn-of-the-century building.
The Project: New Boiler Plant For An Historic Urban College CampusColumbia College Chicago is the largest private arts and media college in the U.S. Located in the heart of Chi-cago’s South Loop - near Lake Michigan, Grant Park, and the Art Institute of Chicago - the urban college serves more than 12,000 students in a campus that consists of 22 buildings, many of them historic. The build-ings slated for the boiler replacement were some of the oldest, built between 1905 and 1910.
The project was not a simple boiler replacement. The existing, aging plant, located at 624 S. Michigan, was to be cleared entirely from the basement of the building to free up usable space. The new plant was to be built in Columbia’s adjacent property at 618 S. Michigan. In addition, both facilities would be occupied throughout the duration of the construction, and student activities were not to be disrupted. Avoiding disruption meant more than managing noise and keeping the facility open for use; it also meant maintaining a comfortable thermal environment for the occupants. This objective was further complicated by the project’s construction start date, which was scheduled for the beginning of August, leaving only two months before the start of the heating season.
Similar to most construction projects, the success of this project would be a function of the project team’s ability to meet its goals in three main areas: technical performance, budget, and schedule.
Identifying ChallengesMeeting the challenges of Columbia’s project requirements required a classical engineering problem-solving approach assisted by some modern design tools. The traditional engineering problem-solving approach consists of the following six steps:
- Problem identification
- Identification of possible solutions
- Evaluation of possible solutions
- Anticipation of negative consequences
- Overcoming obstacles to carry out solutions
- Detailed plan for carrying out solutions
- Where would the new boiler plant be located?
- How would the new equipment be transported to the new mechanical room with the least impact to the building’s structure and daily activities?
- How would McGuire make connections to existing utilities (natural gas and electric) and distribution (low-pressure steam supply and low-pressure steam condensate return) in the most cost-effective manner while maintaining proper component function (pitch of steam supply and condensate return lines) as well was clearances for egress and equipment access?
- Where could the boilers draw combustion air and where would the hot flue gases exhaust
- What was the contingency plan for heating the building if the new boiler plant was not operational by October?
First Challenge: Where Should The New Boiler Plant Go?The team approach provided invaluable insights into the basic but biggest issue of the project: Where should the new boiler plant go in the 618 S. Michigan building?
The basement at 618 S. Michigan already had its own boiler plant for the building, which was to remain intact. The team first agreed that the basements of the 624 and 618 buildings should be physically connected so build-ing engineers could access the boiler plant from either building. The team also decided that the new boiler plant should be built close to the existing plant for several reasons:
- Ability for the new boiler plant to draw combustion air from an established source
- Means to exhaust products of combustion to an established termination point
- Possibility to interconnect the two plants, which would provide flexibility to heat both buildings from either plant and also provide a contingency plan for providing heat to the 624 S. Michigan building if the new boiler plant was not fully functional
- Option for the building operators to heat both buildings from the new, more efficient plant during part-load periods and to provide the same contingency heating plan for the 618 S. Michigan building in the future when upgrading the 618 S. Michigan boiler plant.
Choosing The Equipment: High-Tech Modeling And Site VisitsSatisfied with the direction of the schematic design, the team moved to the next steps in designing the plant: es-tablishing how much space would be needed for the new equipment and then selecting the equipment that would meet the space and capacity requirements. To size the new boilers, the team performed a heat-load analy-sis for the 624 S. Michigan building by simulating the building’s heat-loss performance with a computer model and utilizing past weather data to determine the required heat capacity of the plant to maintain space heating setpoints. The design team needed to select boilers that: (1) could efficiently meet the heat load for the building; (2) fit within the space allotted for the new mechanical room; and (3) be transported to the new mechanical room with minimal impact (in terms of cost and disruption) to the building.
McGuire team members made multiple site visits to measure the critical components of the access route to transport the boilers from the building loading dock to the basement mechanical room. The challenge was to fit 300 nominal boiler horsepower of heating capacity through an existing 118- x 73-in. lift slab that connected the loading dock to the service corridor in the basement (which would then allow for a straight shot to the new me-chanical room). Adding to the complexity, the mechanical room height was limited. The overall height of the steam supply and flue outlet connections for the boilers could be no more than 66 in. from the mechanical room floor.
After coordinating the technical and physical constraints with several boiler manufacturers, the design team made a decision to use three smaller boilers. These three boilers would satisfy the building’s heat load and fit through the access route. In addition to meeting the project’s technical criteria, the three-boiler solution also fit Columbia’s project schedule and budget.
Steam Supply Pipe With Less Than An Inch To SpareAfter confirming the footprint of the new boilers would meet the space available and allow for an economical and non-disruptive access route from the loading dock to the new mechanical room, the focus shifted to examin-ing the feasibility of connecting to existing utilities (gas and electric) and distribution (low-pressure steam sup-ply and steam condensate return). The design team recognized this as a critical component for the success of the project.
The most difficult obstacle was the route of the low-pressure steam supply main (an 18 in. overall diameter pipe with insulation) from the new mechanical room in the 618 S. Michigan building to the existing steam header in the 624 S. Michigan building. The low-pressure steam main would need to be pitched in the direction of flow one inch for every 40 ft to allow the steam condensate to flow through the pipe properly, and the distance from the new boilers to the existing steam header was over 150 ft.
The design team utilized 3-D drafting software to demonstrate the route of the new steam pipe. To make sure the model was right, the team conducted extensive site surveys and spent time on-site drafting the intended pipe route. There was very little margin for error, as the route crossed many existing services that could not be dis-rupted (without major cost and loss of building use to Columbia). Once the pipe entered the 624 building, it had to cross an egress corridor before entering the room where the existing steam header was located. The success of the route came down to less than an inch.
Collaborating To Plan Installation, Anticipate IssuesWhen McGuire felt the design solution was complete, the team presented the plans to Columbia to ensure the design met Columbia’s expections and to start collaborating on the next step: how to anticipate and mitigate negative consequences of the installation.
Even though the design team had already determined the ideal size and configuration of the boilers and low-pressure steam main, there were installation challenges that needed to be addressed. One issue was unexpected cold weather. Interconnecting the 618 and new 624 boiler plant would allow for a contingency heating plan to heat the 624 S. Michigan building in the event the new boiler plant would not be fully functional by October 1st, but what if cold weather occurred sooner or severe cold weather occurred that exceeded the capacity of the existing 618 boiler plant? Also, would the increased combustion intake air requirements and exhaust products of combustion for the 618 S. Michigan building (as a result of the additional boiler plant) be able to be met both physically and economically?
The design team and Columbia made innovative decisions to overcome these obstacles. In order to provide peace of mind that heat (and at peak demand capacity) would be available for the 624 S Michigan building at all times, the team members decided to phase the demolition for the project. The existing 624 S. Michigan boilers could remain in place until the new boilers were installed and commissioned. While this added some extra cost to the project (for the phased demolition and additional valves between the old and new plants) the added security value was deemed to be worth the cost.
Next, to solve the issue of the increased combustion air requirements of the new, larger 618 boiler plant, the team developed an efficient and economical scheme by retrofitting existing exhaust louvers and ductwork near the new mechanical room. They rerouted the exhaust air ductwork through the 624 S. Michigan building and provided new exhaust louvers. The existing flue stack from the basement of the 618 S. Michigan building to the roof was evaluated and the size was determined to be sufficient for the increased products of combustion. However, the common breeching from the existing boiler plant serving the 618 S. Michigan building was redesigned and replaced to allow the new boiler plant and the existing boiler plant to share a common breeching.
Construction PhaseAll the hard work - the detailed due diligence, collaboration, modeling, and planning - was ready to be put on paper. The team issued detailed construction plans and specifications to a team of general contractors to implement the design solutions, finally entering the last phase of the engineering problem solving approach: the detailed plan for carrying out solutions.
The design team remained actively involved during the construction administration phase of the project to ensure that the design concepts were clearly communicated and coordinated with the construction team. Weekly construction meeting were held with a representative from Columbia, the building engineer, and the contractors to coordinate construction implementation, progress, and upcoming milestones. The construction schedule was evaluated at each meeting and activities for the week as well as for the next two weeks ahead were discussed in detail. Multiple site visits were made by the design team to respond to contractor requests for information and bi-weekly progress reports were issued to track progress and review installation details to avoid a lengthy punchlist at the project closeout.
Unanticipated CostsWhat the team learned is that even the best-laid plans can still lead to complications, especially when dealing with historic buildings. For instance, part of the project scope was to insulate existing piping. Before demolition, it was impossible for McGuire to determine the full extent of the issue. Knowing this, the design team built the cost of this portion into the bid by asking for unit pricing.
After demolition, the team saw that the scope of this aspect of the project was much larger than expected but moved forward. The team didn’t address the issue with Columbia until after the contract had been executed. The unanticipated costs could have been avoided if a changeorder request was made when the extent of the insulation became known after Phase I demolition.