Infrastructure Planning

Unfortunately, with underground utilities there is no “bury them and forget it!”  Steam lines leak, sewer lines collapse, and water lines break, and all of them someday reach full capacity. When planning the campus infrastructure, some thought must be given to the routing of underground utilities, keeping in mind that they eventually will have to be repaired, enlarged, or replaced. An essential part of any campus master plan must be the utilities master plan, which lays out a logical pathway around and through a campus to supply existing and future buildings with electrical, telecommunications, chilled water, steam, water, gas, and storm and sanitary sewer systems. Creation of these pathways, or grid, should consider such things as maintaining campus access to buildings and other facilities when the time comes to repair or replace the buried systems. Often such failures come at the most inopportune times, so important spaces such as a lawn used for commencement, while convenient for placement of utilities, may prove to be disastrous if the utility fails two days before graduation ceremonies! Thorough planning in the placement of underground utilities can avoid major inconvenience, unnecessarily high repair costs, lost revenues, and broken hearts.

Even on campuses that have not been developed with a utilities master plan guiding utility placement, it is never too late.  Creation of such a plan can document existing locations and identify opportunities for rerouting or future building site modifications in order to reorganize the utility infrastructure over time. When a utility corridor grid system is developed, space can be allotted for essential utilities as they are upgraded or replaced, allowing the abandonment of poorly routed utility systems.  In the case of buried utilities, one thing is certain: “Time heals all wounds!”

Following is a review of the major underground utility systems and the characteristics to consider in their placement.

Utility corridors. Development of a utility grid with designated corridors for utility placement organizes a campus and helps guide decisions on building expansion or new construction. Such corridors should follow streets or access drives, a practice found in most towns and cities for municipal utilities. Such corridors should optimally run parallel but outside the paved street or drive, unless consideration has been given to how traffic would be detoured during major utility repairs or reconstruction. Designating a 5- to 10-foot strip on either side of a paved roadway is recommended, allowing room for sidewalks and lawn. However, the placement of street trees should be considered to avoid the utility lines, because trees do grow and no one likes to see a mature tree cut down. If use of the paved area is necessary, lines should be kept to one side or the other. Parking lots, recreation fields, important gathering spaces, and the underside of building foundations should be used only when there is no other feasible alternative.

Sewer Systems. Unlike many of the other systems, sewers are typically nonpressurized, gravity flow systems. Thus topography largely dictates placement of sewer mains and collectors. However, with some creative thinking even sewers can be developed along a logical grid, intercepting the major lines to municipal or campus treatment facilities or storm outfalls. Over time, two major issues arise with sewers: they collapse or reach their original design capacity. Thus sewers, manholes, and collection vaults should be placed where large and deep excavations are possible and are least disruptive to campus operation.

Many campus sanitary sewer lines were originally located to minimize the length of runs and to maintain slope for adequate flow and minimize clogging. In some cases, as campuses expanded, lift stations were necessary to regain elevation to major sewer mains. Depending on the topography of the site and the elevation of the main sewer interceptors, it may be possible to develop a future collection grid that eliminates or minimizes the reliance on lift stations.

Storm sewers, since they normally collect surface run-off as well as roof drains, usually follow roadway systems. Under severe rainfall, it is not unusual for stormwater systems to reach capacity for a short period of time, thus surcharging and pressurizing the system. This results in backflow that may evidence itself in building flooding, street flooding, or, if improperly interconnected with sanitary lines, through building floor drains. Thus proper design and sizing of collection mains as well as use of retention/detention systems must be carefully considered.

Electrical Systems.  Four aspects of campus electrical distribution need to be considered when planning the electrical grid: cable routing, substations, transformers, and emergency generators. High-voltage distribution cable routing is not constrained by elevation, like sewer systems, but it does have unique requirements. Electrical cable should not be next to other underground utilities because of the hazards associated with cable failure or nearby excavation. Thus, while it may be placed in a utility corridor, sufficient spacing from other utilities is necessary. Furthermore, the cable needs to be clearly identified, either with locator tape or utility maps. The creation of loops or secondary circuits to serve critical facilities should be planned, such as for hospitals, data centers, research buildings, and other facilities demanding fully redundant service.

Substations are essential but often unsightly, so their location requires some careful consideration. Today the substation is at the edge of campus; tomorrow it could be at its center. Therefore, as part of the master planning effort, plans for current and future locations should be developed in conjunction with the local electrical utility company.

Step-down transformers may be located inside a building, in a vault, or adjacent to the building on a pad. For various safety and maintenance reasons, primarily fire/explosion (although rare) or replacement, it is preferable to locate transformers outside, which creates its own set of requirements. First, access, especially under emergency conditions, should be planned for. This access should consider large flatbed trucks and hydraulic crane placement to lift and set a transformer. In addition, screening of the transformer using building orientation, enclosures, or landscaping will be required. Thoughtful advance planning can help these installations “vanish” from view.

The last aspect of electrical systems is the provision of emergency generation. The location of these is often thought about only when a new building is under design, and then many unforeseen problems may arise. Generators require supply air, are loud, and produce exhaust gases, often with an odor if they are diesel-fired. Advance planning can avoid potential problems by considering prevailing winds, adjacent building orientation and heights, fresh air intakes, pedestrian walkways and green areas, and so on. Opportunities to size emergency generation capacity for multiple buildings can also be considered when planning for future development of a campus.

Telecommunication Networks.  Low-voltage cable, optical fiber, and wireless networks fuel today’s information technology, well beyond the traditional telephone circuit. Since modern telecommunication systems were never planned for in master plans, a satellite x-ray of most any campus would reveal a spider web of cables, fiber, and antennas. But it is never too late to develop a cable plant and wireless network master plan. Since cable is always being upgraded with newer requirements and improved bandwidth, the consolidation of the underground cable ducts should be planned for. Again, looped or redundant cable feeds are important since many building automation, fire alarm, and security systems now run on campus data networks. In similar fashion, radio and wireless coverage planning can help identify optimal and unobtrusive antenna placement as well as equipment room locations.

Chilled Water. Central chilled water plants, or interconnected building chillers, are often an efficient way to cool campus buildings. Underground chilled water distribution systems are pressurized, but routing and elevation change can influence pump sizing and overall system efficiency. In addition, looping the system provides redundancy in the case of piping failures or routine valve station maintenance. In planning for chilled water, consideration should be given to routing, valve vault locations, disruption due to piping failures, and system sizing to accommodate future growth, during either initial installation or the construction of future upgrades. Unlike steam systems, insulation repair and maintenance is a less critical factor in that the lower temperature differential between the chilled water and the surrounding soil makes it more durable.

Steam and Pressurized Hot Water. Central heating plants have long been employed on college campuses due to the proximate location of a large number of buildings. The resulting distribution systems are often direct buried or placed in utility tunnels. The tunnels are often quite expensive, so proper placement and routing is important to minimize costs.  However, maintenance of insulation and valves, and upgrading of capacity for future growth is greatly simplified. The chief factor in maintenance is not the steam piping, which is normally quite long lived, but the condensate piping, owing to the caustic chemistry of condensate (which is avoided in pressurized hot water systems). Therefore regular maintenance and future piping replacement must be planned for. This maintenance requirement is amplified if the steam and condensate piping is direct buried. In this case not only must the piping and associated valve pits be maintained, but the surrounding insulation as well. Water saturation of insulation materially reduces its efficiency, leading to piping corrosion and ground heating, which will kill all adjacent vegetation. Excavations around direct bury heating pipes should be seriously considered when planning the placement of these systems.

Gas. Natural gas lines rarely leak but when they do, the result can be quite “explosive.” Gas lines are one of the few utilities where placement under paved areas is permissible and may be desirable if properly marked. Since gas mains are pressurized, they may be run parallel to other pressurized lines such as water mains. However, some distance should be maintained from utilities that may require more common excavation (steam) or sewer lines, especially sanitary.  Nonpressurized mains can provide a conduit for leaking gas, routing them to building locations where they may be trapped and possibly ignited.

Domestic Water. Water mains serving a campus, like some other utilities, are best if looped and sized liberally for future growth. However, unlike other utilities, they are more prone to leaks because of the dynamics of pumping long distances from wells or reservoirs. It is important to maintain water pressure for fire safety. Because of these characteristics, large swings in water pressure are common, often leading to over-pressurization that causes old lines, valves, and joints to fail. So it’s not a question of if water mains will spring a leak, but when, and it usually happens at the worst possible times.  While water mains may be placed near paved roadways, they should be placed on one side or the other so that excavation for repair can be performed without closing the entire roadway. Where water mains cross important intersections or other utilities, buildings, and tunnels, the risk of leaks can be managed by sleeving the line. In designing the best routes for water mains, remember that minor leaks can quickly grow into a major one, undermining or destabilizing surrounding soil that other utility lines or foundations rely on for their support.

Irrigation. Traditional irrigation systems have used potable water sources. However, increasingly, the use of collected rain or grey water is being used to conserve water. In order to use this resource, holding tanks and cisterns, must be constructed, and the water held by them must be piped to the areas requiring irrigation. A well-planned system for both collecting and distributing the water can be developed as part of overall infrastructure plan. However, special precautions must be exercised to route and clearly mark grey water irrigation systems to prevent inadvertent cross-connection with domestic water supplies.

Looking Ahead.   In an era of rapid technological advancement, innovations in sustainable energy, water, waste, and telecommunications are reshaping how we design and use campus buildings. This will certainly affect future decisions on campus utilities.  Wireless transmission of voice and data is now commonplace but this same technology may apply to electrical power transmission in the future. Heating and cooling of campus facilities using new and different technologies such as solar, wind or geothermal sources directly affect utility sizing and distribution decisions.  Water supply and sewage systems must now be considered in light of storm water retention, groundwater recharging, the use of gray water for irrigation and other non-potable water purposes, and newer treatment technologies such as desalinization of sea water.  The planning of campus utility systems must now be cognizant of such changes in technology and policy and prudent strategies developed to accommodate this continuing evolution.