Version 1.1, March 1997

Introduction

The George Washington University is preparing for a vast increase in the use of communications technologies in support of all aspects of the campus' operation. The ability to install and enhance these technologies easily will be critical to the campus' programs over the next decade, and beyond. The existing underground conduit infrastructure is irregular, does not have adequate capacity, and is not ubiquitous. Therefore a new infrastructure, designated the Interbuilding Communications Conduit System (ICCS), has been planned for all future conduit additions.

The ICCS provides the underground physical infrastructure between buildings that supports all campus communications system media. Since "right of way" underground is very difficult to acquire, the capacity of the ICCS has been defined to serve the campus well into the next century. It is intended to be viable for a great number of different applications, both production and research, requiring a wide variety of media. For these reasons, the design of the ICCS must be constrained by a number of important criteria, as specified below.

The ICCS is being constructed in sections as needed, and each section must interface properly with adjacent sections. Additional sections are planned in the near future to serve a new dormitory and wellness center. Ultimately the ICCS will serve all buildings on the main campus and some buildings on adjacent university owned land.

External communications service providers must have limited underground service access to the ICCS as well. In particular, Bell Atlantic needs access at several points around the campus from their conduit systems. Any such interconnect points must be designed to meet individual needs, but general criteria are specified below.

General Topology of the ICCS

The completed ICCS will consist of a north run and a south run of conduit beginning at the Academic Center. The north conduit run will connect the medical center buildings into the general campus infrastructure. The south conduit run will serve the majority of university buildings. A conduit structure may be placed between the proposed Wellness Center and the new dormitory. This will provide for physical route redundancy in case of natural disaster or the need to relocate a section of the system in the future. Campus buildings are connected to the ICCS at specific locations where underground vaults are located.

The new ICCS consists of a bank of fifteen (15) four inch diameter conduits, encased in steel reinforced concrete, interconnecting a series of underground "communications vaults" (CV's). These vaults provide physical access for installation and splicing of media, and may be used to locate some in-line communications equipment. They also serve as interconnect points for smaller conduit banks feeding individual buildings. A communications vault is located wherever a significant change in direction of the main conduit bank is required, or a building feeder is needed. By minimizing bends in the conduit bank and minimizing pull distances, it should be easy both to install and to remove media over the life of this system.

ICCS Design Parameters

The parameters stated below are to be used for the design of any new section of the ICCS. Specific designs also must take into account existing underground utilities and other subsurface constraints. These parameters have been chosen to ensure that the overall functional goals of the ICCS are met.

The critical design parameters of the ICCS are:

1. The Communication Vaults

The underground communications vaults (CV's) provide work space for the installation or removal of media, mounting points for dressing the media neatly within the vaults, and space for mounting some limited electronics such as in-line amplifiers or splitters.

CV's are reinforced concrete, typically precast and brought to the site in 2 sections. Access is through the top and may require variable extension of the "neck" to reach ground surface level. CV's may be cast in place if conditions require it.

See Figure 1 and Figure 2 for typical vault designs.

1.1. Vault Location

Vaults are to be located wherever a significant change in direction of the main conduit bank is needed, or a building feeder is to intersect the ICCS. See the attached plan of the ICCS Section 1 for a good example of this.

A "significant change of direction" is defined as a change in alignment that would exceed the maximum total bend parameter allowed. See below.

Vaults are installed under roadways as necessary to run along with or cross public streets. It is preferred that vaults on university property be installed under walkways or under landscaped areas if they don't interfere with tree roots, etc.

The exact locations may be heavily constrained by existing underground utilities, especially drainage systems which can not be realigned. Contact the Facilities Management office for the most recent survey data or drawings of known underground obstacles.

1.2. Vault Dimensions

There are two standard sizes for communications vaults. Where a vault is required only to accommodate a change in direction, the smaller "pull box" size may be used. These vaults are to have exactly 2 conduit bank penetrations. All other vaults must be the larger size, referred to as an "access box."

1.2.1. Access Box Dimensions

The interior of an "access box" CV is to be at least 6 feet by 8 feet in plan, and 7 feet high. Larger dimensions may be used to accommodate more penetrations or other criteria. The 6 foot sides are used typically for the main conduit bank penetrations. The 8 foot sides are used for feeder conduit banks or for branch main conduit banks. A standard telephone company 38Y type manhole and collar should be used in public roadways.

1.2.2. Pull Box Dimensions

The interior of a "pull box" CV is to be at least 5 feet by 5 feet in plan, and 7 feet high. The main conduit banks usually will penetrate 2 adjacent sides.

1.3. Access Hatch

Access to the CV is to be provided by a 36 inch diameter hatch centered over the top of the vault. The removable metal cover will be typically 40 inches diameter and must be designed for "light traffic" loads. Manholes placed in roadways will have one or preferably two 30 inch cast steel manhole covers. The hatchway and manhole covers must be bolted down when closed, using McGard Intimidator high security bolts. The CV hatchway shall be even with the finished grade of the surrounding terrain.

The assigned CV number is to be marked on the hatchway cover in a permanent manner. Current practice is to use an arc welding setup to put a bead on the cover forming 4" high lettering. Any alternative that has equivalent permanency is acceptable. The marking will be specified by the university; a typical marking would be "CV19" to designate "communications vault number 19".

1.4. Drainage

CV's may include provision for drainage of ground and rain water from the interior. Typically, a small sump is provided in the center of the CV floor. This will leave a minimal depth of standing water in the CV when pumped out. The floor sump is to be fitted with a cast iron grate, or equivalent.

1.5. Internal Surface Preparation

Conduit bank identification and individual conduit labeling will be painted on the inside surface of the CV. Therefore, the internal surface must be relatively smooth and paintable with epoxy paint. It is recommended that precast CV sections be spray primed in the yard before transport to the site. Cast in place CV's must be formed in such a way that a smooth interior surface is created.

1.6. Internal Fittings

Each CV must be constructed to include common interior fittings. These are intended to support the use and management of the CV. All exposed metal fittings shall be rust resistant, typically galvanized steel.

1.6.1. Unistrut Mounting Channel

Unistrut P-3200 series channel is to be cast horizontally into the walls of the CV.

In a "pull box", at least two 4 foot long sections are to be provided separated vertically by at least 2 feet. They need be only on the two walls that do not have conduit penetrations.

In an "access box", there must be at least four 4 foot sections on each wall, separated vertically to accommodate conduit bank penetrations.

1.6.2. Access Ladder

A removable metal ladder is to be provided inside each CV. The ladder will be used by staff to enter the CV. It should be held in place at the top by metal loops or similar anchors, and must rest on the bottom of the CV. The ladder must be easily removable in order to facilitate cable installation and routing within the CV.

1.6.3. Pulley Anchors

Anchors must be provided suitable for cable installation pulleys.

In a "pull box" CV, the anchors should be roughly opposite the conduit bank penetrations.

In an "access box" CV, the anchors are to be in each of the eight (8) corners of the CV.

1.6.4. Lighting

Permanently installed lighting is not required in the CV. It may be provided if electrical power is readily available. Light fixtures must meet OSHA requirements. In all cases, at least 2 hanger loops are to be provided in the CV ceiling to accommodate temporary utility lighting.

1.6.5. Power

Electrical outlets are not required in the CV's but may be provided if conditions warrant. Such power would be used for test equipment or lighting during operations within the vault, not for permanently installed equipment. If provided, outlets must be GFCI protected and should be mounted on the roof of the CV with weather resistant covers.

1.6.6. Conduit Penetrations

Conduits are to penetrate at right angles to the CV wall. Penetrations should be located in the upper half of CV walls wherever possible in order to minimize the depth of the conduit bank trenching required. Penetrations must be at least twelve (12) inches from an adjacent wall.

Conduit penetrations are to be sealed against water seepage and finished inside the CV to present a smooth, tapered entry. Unused conduits are to be capped or plugged to prevent gases or wildlife from migrating between CV's.

Planned conduit penetrations, such as for the main ICCS conduit bank or building feeder conduits, should be accommodated via "knock out panels" precast into the sides of the CV's. See the detail in the ICCS Section 1 CV design for examples.

1.6.7. Grounding Rod

All CV's shall have a 6 foot long by 3/4" diameter copper plated grounding rod installed through the floor of the CV near one corner. The rod shall protrude no more than 4 inches above the floor. The hole through the CV floor shall be sealed against seepage with either epoxy filler of RTV caulking.

1.7. Installation

The CV shall be set on 6 inches of level, 90 percent compacted granular fill, 3/4 to 1 inch size, extending 12 inches beyond the CV on each side. Granular fill shall be compacted by a minimum of four passes with a plate type vibrator. Drain sumps shall be provided for precast vaults, as required. Installation also shall conform to the manufacturer's instructions.

1.8. Minimum Ground Cover

The top of the CV chamber must be at least twelve (12) inches below grade, but no deeper than necessary.

2. The Conduit Banks

The ICCS conduit banks consist of fifteen (15) four-inch diameter conduits, arranged in a pattern 5 wide and 3 deep. The center-to-center spacing of the conduits is six (6) inches, in both directions. The set of conduits is encased in reinforced concrete with approximate finished dimensions of three (3) feet wide by two (2) feet high. See Figure 3 for a typical cross section. Other configuration may be used with approval.

Whenever possible, the installed conduit bank should not have any "low spots" that would collect water.

2.1. Maximum Length

The maximum length of any new individual ICCS conduit bank is 300 feet. This is to ensure minimal total friction when installing or removing media.

2.2. Maximum Allowable Change of Direction

The total accumulated change of direction allowed in any new ICCS conduit bank is forty five (45) degrees. No bend radius may be less than ten (10) feet. By avoiding sharp bends, or large accumulated change of direction, these requirements are intended to ensure that media can be installed and removed easily. If a change of direction greater than this amount is required, a "pull box" CV must be installed to effect this.

2.3. Conduit Material

Normally schedule 40 PVC conduit is to be used. In cases where the ICCS conduit bank runs parallel to a 4KV or higher voltage distribution system for more than ten (10) feet, any ICCS conduit with less than a four (4) foot separation from the high voltage conduit system must be EMT, and must be grounded in at least one of the attached CV's.

2.4. Encasement

The concrete encasement must be reinforced with #4 steel reinforcing as shown in Figure 3. The concrete is to have a 28 day strength of 4,000 psi and a slump of no more than three (3) inches when placed.

2.5. Minimum Ground Cover

The top of the concrete encasement must be at least 24 inches below finished grade. The ICCS conduit bank depth should be kept as shallow as possible within this constraint.

2.6. Location Marking Tape

A burial marking tape shall be laid in the backfill over the ICCS conduit bank. This tape should be at least twelve inches below the finished grade and 12 inches above the conduit bank. The material must be rated for at least 50 years direct burial. The tape shall be at least 3 inches wide, and marked every five feet with 2 inch high wording similar to the following:

WARNING: COMMUNICATIONS CONDUIT BURIED BELOW

2.7. Pull Cords

A polypropylene pull cord shall be installed in each conduit. The cord must have a tensile strength of at least 400 lbs. The cord shall be attached to the conduit cap at each end of the conduit bank in such a way that the cord is stored inside the end of the conduit when the cap is in place, and is readily accessible when the cap is removed.

3. Connection to External Systems

Connection to external systems, such as Bell Atlantic service distribution conduit, is to be designed as needed. Typically this will include two or more 4" diameter conduits penetrating a CV and leading to a service supplier's pull box. No fewer than 2 such conduits should be provided in order to allow easy upgrade of installed service cables, and to avoid excessive repeated penetrations of the CV. The CV wall penetration must be cored, not broken, unless a "knock out panel" has been provided for this penetration. The penetration should be as near the ceiling of the CV as practical. The penetration must be sealed from the outside with epoxy filler or RTV. The conduit penetrating the CV must not protrude into the CV at all.

4. Connection of the ICCS to Campus Buildings

The size of the conduit bank feeding individual buildings should be determined by consideration of the size of the building and its foreseeable use. The smallest structures are to be served by no fewer than four (4) 4" conduits; larger structures will require as many as twelve (12).

As a guideline, the following capacities should be provided:

          Total Building Area         Number of 4" Conduits

	Less than 50,000 ASF                   	4


	50,000 - 100,000 ASF                   	6


	100,000 - 300,000 ASF                  	8


	300,000 -  500,000  ASF                	9


	500,000  - 700,000 ASF                 	10


	More than 700,000 ASF               	12

The building feeder conduit bank may be encased in reinforced concrete, or not, to be determined by the expected life of the structure.

See section 5.2 of the EIA/TIA-569 standard for further considerations regarding interbuilding conduit systems and service feed requirements.