Perimeter Security Kit of Parts

Introduction

As the U.S. government’s principal provider of office space for federal workers, the General Services Administration (GSA) has played a leading role, since its inception, in the development of design standards and model approaches to building upgrades and alterations. In security design for existing buildings, this means seamlessly retrofitting buildings to feel safe and be safe, in urban settings that still welcome the public. Constructability — the design-builder’s specialty — assumes paramount importance, demanding second-sight grasp of retrofit issues and optimal collaboration between architecture, engineering, and building trades.

Design-build teams are uniquely positioned to provide this second sight by bringing to the table design and execution players in a concurrent, rather than sequential, manner to anticipate existing conditions and retrofit challenges. This article showcases emerging best practices for design-build teams who are or want to be contenders in cutting-edge security retrofit.

GSA’s principal security retrofitting efforts focus on protection of building perimeters against truck or car bombs through vehicular barriers, surveillance and visitor monitoring systems, and protection against blast hazards such as glass fragmentation, including modification of entrance lobbies to control circulation and ensure the effectiveness of visitor monitoring processes.

Nowhere is the goal of seamless integration more important than at GSA’s 454 historic buildings. Many are monumental courthouses, custom houses, and other public buildings that are focal points of towns or cities. At these properties, GSA needs to respect what makes the historic property significant. Foremost in security retrofit planning is the original architect’s design intent behind public entrances and gateways into the building, from the point where the property meets the city sidewalk through security processing and interior circulation. Preserving this gateway experience is a major goal.

To address these challenges, GSA’s Center for Historic Buildings, in collaboration with agency security engineering experts and 11 regional preservation programs, has developed a number of prototype designs for seamlessly integrating security improvements into sensitive settings. GSA’s vehicle barrier kit of parts, the most complex prototype, offers a variety of elements that can be combined in different ways in response to differing streetscape conditions. Elements in the basic prototype are designed to blend with a monumental courthouse built in the early 20th century. Two variations on the prototype use modernist and Victorian architectural vocabularies to blend with buildings of other styles and eras.

In his September 2004 Design-Build DATELINE article “Juggling the Demands of Security with Design and Construction Excellence in Public Facilities,” GSA glass fragmentation expert Steven Smith detailed GSA’s security retrofit program from the advent of Interagency Security Standards in the aftermath of the 1995 bombing of GSA’s Alfred B. Murrah Building in Oklahoma City to today’s risk assessment decision framework with quality standards maintained by integrating security into GSA’s Design Excellence and Construction Excellence programs. The Design Excellence process uses top national architecture firms as peers in design team selection and design review. Construction Excellence similarly employs top experts in the construction field to bring out the most from GSA’s construction teams to ensure that design goals are achieved.

GSA guiding principles for security retrofitting at historic buildings are:

• Reversibility;
• Minimizing adverse effects on historic spaces and materials through thoughtful placement of necessary equipment;
• Maintaining access to important public buildings and spaces;
• Tailoring security design to preserve character-defining features and respect historic design intent;
•  Designing new features to contribute to the quality of Federal public spaces;
• Integrating new security features to maintain overall cohesiveness by relating their design and placement to the historic site; and
• Promoting a continued federal presence in city centers.

Camouflaging Surveillance Cameras

Exterior cameras reinforce physical perimeter barriers by allowing activity around the building to be continuously monitored from a single remote location. Cameras are either fixed or movable and are generally placed to allow as wide a viewing plane as possible. Design goals include minimizing the visibility of surveillance camera equipment and avoiding damage to historic materials.

Institutions involved in volume procurement of security equipment most commonly choose camera assemblies in which both lens and moving components for remote operation are contained in a globe-like protective housing. Separate component systems (Figure 1) may be more troublesome to install and maintain, but are generally less conspicuous because all but the lens and attached portion of the pan-tilt device can be placed out of view. There are a variety of ways to reduce the visual and physical impact of both types of camera systems:

• Avoid damage to historic façade materials by mounting cameras in masonry joints on the rear side of parapet walls, on the underside of overhang framing members, on adjoining building rooftops, or on existing or specially designed poles or other freestanding elements.
• Consider poles or offsite mounting to eliminate the risk of damaging historic materials, reduce visual impact, and gain a wider field of vision.
• Design and finish poles to blend into the streetscape along with lamp standards and other street furniture.
• Camouflage camera housings and supporting brackets by painting to match adjoining materials.
•  Locate cameras away from the front of the building, from public rights of way, and from public areas of the building for minimum visibility to visitors and pedestrians.
•  Specify the smallest camera components needed to satisfy functional requirements.

GSA’s model pole developed for monumental federal buildings in Washington, DC, features a slender gooseneck profile, statuary finish, and contoured base suggesting turn of the century lamp standards (Figure 2). Globe housings are offered in a range of sizes, so the smallest diameter housing should be specified. Colored portions of the housing should match the pole.

Prototype Vehicle Barrier Systems

Garden Wall Barrier System

The concept of a kit of parts including hardened street furniture originated with National Capital Planning Commission (NCPC) security design recommendations calling for “an integrated Urban Design and Security Plan” for Washington’s monumental core. NCPC advocated “permanent security and streetscape improvements,” including a “kit of parts — an array of landscape treatments, street furniture, bollards, etc.” for high profile locations such as Pennsylvania Avenue, President’s Park, and the Federal Triangle. In 2001, GSA commissioned Cox, Grae+Spack (formerly KressCox Associates PC) to translate these principals into a master plan for better integrating security enhancements, landscape design, and urban planning to increase public use and enjoyment of the outdoor spaces of the Federal Triangle complex fronting on Constitution and Pennsylvania Avenues in Washington, DC.

Design parameters for anti-ram vehicle barriers included:

• Concealment of the protection.
•  Retention of pedestrian access, requiring permeability.
•  Integration of security design and urban design.
•  Incorporation of streetscape elements such as trees and light standards only as non-structural components of the barrier design.
• Use of a variety of security elements rather than relying on a single type of element, such as bollards.
•  Combining of elements for the best aesthetic effect and public benefit appropriate to the particular street condition and site location.

The Federal Triangle design (Figures 3 and 4) includes several different vehicle barrier solutions incorporating custom-designed structural and non-structural elements configured to respond to the unique pedestrian conditions of each location. The most elaborate solution, proposed for the two grand avenues defining the Triangle, incorporates structural iron railings, low stone pillars, raised planter boxes and seating into a garden wall designed to visually strengthen the pedestrian right of way. Whereas the existing temporary planters convey no relationship to the sidewalk or street and simply appear as obstacles, the architectonic planters and benches of the garden wall barrier system are placed within the sidewalk zone parallel to the street and read as a landscape ensemble. The inner wall of the planter is set in at selected locations to accommodate street furniture such as benches and bus shelters. Openings between planter boxes permit pedestrian circulation at building entrances and street corners. Freestanding integrally designed bollards permitting pedestrian circulation are used to block vehicle access at building entrances and street intersections.

The garden wall approach makes a grander public gesture than barriers located within the property line, at the logistical cost of requiring coordination with municipal authorities on whose land the security features are installed.

Kit of Parts Design Pilot

In 2002 GSA commissioned van Dijk Westlake Reed Leskosky to further develop the garden wall perimeter security barrier concept. The purpose of this second study was to test the garden wall barrier system as a prototype through development of construction drawings, specifications, and construction cost estimates. The prototype design would apply the KressCox garden wall model to a specific, center city, monumental public building site presenting a variety of street conditions and site-specific engineering requirements. These streetscape variations were to serve as the basis for template design documents adapting the multiple-element garden wall concept to a variety of architectural contexts. The barrier design vocabulary would then be expanded to suit buildings of different styles and eras. The two pilot variants for expanding the barrier design vocabulary were a 19th century Romanesque building constructed of red brick and a boldly contoured 1960s modernistic building constructed of concrete.

The principal pilot study building is an imposing, early 20th century Beaux Arts courthouse faced in limestone. Special challenges and constraints of the principal pilot location included proximity to the street, vaults under the sidewalk requiring structural reinforcement, high visual prominence on a public square, and site-specific amenities such as a bus shelter under jurisdiction of the municipality.

Landscape features that can be designed to serve as vehicle barriers include:

• Bollards with deep set foundations.
• Knee walls three feet or higher.
• Planters with foundations.
• Surface mounted planters engineered to vehicle speed and height.
• Seating with foundations.
• Pools, fountains, or water features offering sufficient anti-friction surface or depth to impede vehicle motion.

Figure 5 shows the prototype kit of parts designed to relate to the classical vocabulary of the Beaux Arts building — using stone, molded concrete, cast iron, bronze—except in utilitarian areas, for which simple structural steel bollards were designed.

Structural and non-structural features of the system included:

Garden Wall Components

• Monumental screen wall (stone, concrete) — barrier visually screening utilitarian streetscape amenities, integrated with design of the other elements of the garden wall.
• Ornamental railing (cast bronze, iron) — freestanding or incorporated into garden wall, detailing derived from historic grilles, railings, or balusters able to meet structural requirements.
• Monumental planter (stone, concrete) — masonry faced, formally articulated to relate to principal façade, ceremonial area.
• Monumental bench (stone, concrete) — structural features designed to complement the building façade and site elements.

Bollards

• Monumental bollard (stone, concrete) — masonry clad, detailed to relate to building design, combined with structural benches to form an element group, serving as transition between benches and ornamental metal bollards.
• Ornamental bollard (cast bronze) — detailing derived from areaway posts.
• Basic bollard (steel) — simplified geometry for secondary façades where a more economical approach is appropriate.
•  Retractable bollard — for vehicle access to garage, loading dock, and one-way exit roads.

The site analysis established five streetscape zones for tailoring the arrangement of security elements to the streetscape conditions and pedestrian requirements of each façade:

• Permeable: Using fixed bollards for maximum pedestrian access and retractable bollards for vehicular access.
• Partially Enclosed: Providing seating and public amenities along ceremonial façades, public spaces.
•  Setback: Incorporating permanent and seasonal plantings into barrier design where building to curb depth permits.
• Discontinuous/Compromised: Incorporating screen walls to conceal or obscure grouped utilitarian amenities such as vending, trash receptacles, and bus shelters.
•  Enclosed: Using articulated walls to discourage pedestrian access.

Figures 6 through 8 illustrate how the perimeter barrier elements can be arranged to respond to the property’s varying pedestrian needs, building façades, and urban conditions. Ornamental bollards are placed at principal entrances, street corners, pedestrian crossings, and other high traffic areas. Utilitarian bollards protect service areas at the rear façade; retractable bollards provide vehicular access to the loading dock and parking. At the building’s main ceremonial entrance across from the city’s public square, the sidewalk is partially enclosed with public amenities such as seating, planters, and ornamental railings. An articulated wall of stone and ornamental iron railings is used where pedestrian access is discouraged, such as mid block sidewalk areas lacking crosswalks. In areas where necessary but intrusive public amenities such as a bus shelter, trash receptacles and vending machines are located, a more solid screen wall of stone is used. Plantings, both permanent and seasonal, are incorporated into the barrier scheme where setback distance permits.

A number of site-specific conditions required coordination with municipal authorities, including city planning, traffic management, and street departments as well as the regional transit authority. Two issues introduced by site conditions concerned public rights of way in which accommodations for vehicular and pedestrian activity conflict with perimeter security goals; the others concerned below-grade conditions that increased the complexity of the project’s design and construction.

Municipal bus shelters, newsstands, and other basic urban amenities compromise the efficacy of a perimeter security system by providing opportunities to conceal bombs at easily accessible locations. However, since relocating a single shelter triggers a disruptive ripple along affected routes, after discussing the possibility of relocation with city officials, GSA agreed to instead improve surveillance and undertake minor modifications as necessary to reduce opportunities for concealment.

Identifying utilities and below-grade conditions is perhaps the most important factor in accurately assessing the cost of structural barriers requiring foundations. Modifying the perimeter security foundation design to accommodate major storm and sanitary sewer pipe penetrations in foundation walls increased the complexity and cost of the project. Working around existing utility banks also required close coordination with municipal officials. Vaults extending the property’s below-grade building space to the sidewalks introduced the greatest unanticipated cost, principally for drilling and additional material to drive structural supports beyond the depth of the vaults.

In place of the Triangle’s granite and ornamental metal garden wall, an impact-engineered ornamental railing adapted from the building’s original areaway railings was developed to provide enclosure without visually separating the sidewalk and street. A simplified version of the building’s richly sculptural areaway railings, the vehicle barrier railing provides a decorative contrast to the more austere stone benches that makes the new perimeter ensemble less noticeable against the building’s ornamental façade than it might otherwise be.

Adapting Prototype Security Elements to Different Building Styles

Design parameters for adapting the prototype to buildings and sites of different styles and eras include:

• Landscaping design responsive to the particular site conditions climate, and maintenance/operational environment
• Selection of plant materials suitable for the particular site including hardiness, sun exposure, disease resistance, and tolerance for salt, soil compaction, and pollution. Plant choices should consider site visibility for safety purposes and year-round or seasonally rotating planting options.
• Consideration of site circulation, utilities, and other (potentially concealed) conditions, to be determined in coordination with facilities staff or other experts intimate with the building.
•  Taking cues from historic features, details, proportions, scale, and materials in new security features.
•  Relating perimeter elements to building massing and features (new site security elements at the pilot building are placed to correspond to historic sculptures, a central entrance, and flanking colonnade sections on the principal façade).
•  Responding to the overall character of the historic building and site in choosing from among security retrofit options.

The optional kit of parts developed for the prototype 19th century and modernist building variants demonstrate that the concept of a multiple component perimeter barrier system is adaptable to buildings of different materials and architectural vocabularies: barriers can be clothed in an infinite number of ways (Figures 9 through 12). Elements can also be extracted from the kit of parts and used or not used as site conditions warrant. All sites do not necessarily require all barrier elements and there are other types of site features that might be engineered to serve as barriers while meeting other site needs.

Lobby Screening and Circulation Control

The federal government’s facility standards specifically call for principal public entrances to remain open, with the intent of maintaining a gracious entry experience. Rather than relegate visitors to below grade security processing areas, ceremonial lobbies can be thoughtfully modified to provide appropriate protection for building occupants, while continuing to serve their intended function.

Security Desks

One positive result of the increased focus on security design is a growing trend toward architecturally designed desks. At the Main Archives Building on the National Mall in Washington, DC, semicircular contours and axial placement of the guard desk within the space reinforce the monumental symmetry of the entrance lobby. At-tention to detail, color, texture, and linear elements such as base mold-ings, maintain visual continuity with the adjoining stone walls (Figure 13).

Desks and security-related enclosures should be designed to conceal computer monitors and other equipment without substantially increasing the bulkiness of the enclosure. Enclosures should provide ample tolerances for removal and replacement of equipment. Desks can be designed and fabricated to accommodate dual orientation and directional signs.

Security Screening

Architecturally integrating sizable security screening equipment and circulation control is more challenging in a number of ways than integrating vehicle barriers into historic sites. The cost and bulk of architecturally concealing metal detectors, X-ray machines, and circulation control devices, such as turnstiles, in casework tends to make equipment enclosure an impractical alternative, especially given rapid technology changes that lead to equipment becoming obsolete quickly.

Where space layout permits, locating security-processing functions in ancillary space allows ceremonial lobbies to remain gracious and useful as queuing space and, ideally, as receiving areas once security screening is complete (Figure 14). Design goals for security screening include:

• Creating effective security and an inviting first impression.
•  Providing ample security control, queuing space, and appropriate amenities.
•  Using quality materials and detailing reflecting the building’s noteworthy historic qualities.
• Encouraging visitors to enjoy the entrance experience intended by the building’s original architects.

Transparent barriers can be used to provide discrete physical separation between adjoining spaces, such as entrance and elevator lobbies or entrance lobbies and corridors. Glazed partitions should not be used to bifurcate spaces lacking a natural division.

Where ancillary space is not available, glazed partitioning is not appropriate, and greater circulation containment is necessary, thoughtfully clustered amenities can create a subtle physical separation within a welcoming environment.

Furnishings that can be arranged or engineered to serve as circulation barriers include:

• Concierge-like security desks
• Wayfinding kiosks
• Benches
• Interpretive displays
• Ornamental grilles

Like the ancillary space approach, this alternative avoids truncating historic lobbies and allows building occupants and visitors to enjoy the originally intended entry experience. To avoid the appearance of a walled enclosure, furniture groupings should be of non-uniform height and well below eye level to allow open views of the lobby. Alterations for circulation containment should allow visitors to step into an open queuing area, even if passage into the larger lobby area is restricted. Avoid introducing narrow passageways or chute-like enclosures, even glazed enclosures, directly at the entrance door. Ballistic protection for security screening personnel should be incorporated into screening stations, rather than being used to create a visitor containment chamber (Figures 15 and 16).

Conclusion

GSA’s security retrofit prototypes demonstrate that high performance can be achieved without compromising gracious sites and spaces. Design-build teams have an opportunity to raise the standard by educating property owners on options for integrating security features into existing architecture and landscape settings. Forging the closest possible collaboration between design and execution, they can be ahead of the curve on constructability issues to improve the quality and consistency of retrofitting projects at buildings of all types and eras.

Every location is unique and benefits from site-specific design tailoring. In some cases, landscape solutions such as berms, plinths, or other grade modifications may be less costly and less conspicuous than structural barrier elements, if grade changes can be accommodated without compromising the character or integrity of the site. Appropriate surface finish variation and geometry-softening contours can also help to make new features less intrusive.

Several principles emerge:

• There are many ways to clad or detail structural barriers to relate to the visual qualities and character of a historic site;
• Barrier concealment can be tailored to particular property locations and project budgets, reserving more costly cladding materials for more sensitive locations;
• Incorporating a variety of barrier elements into the site design eliminates the repetitive appearance of long rows of bollards or barriers;
•  Locating barrier elements with sensitivity to pedestrian traffic and incorporating public amenities into the barrier system can create a more welcoming urban environment;
• Pedestrian amenities such as benches can be engineered to meet impact resistance requirements;
• Multi-element barrier systems can be tailored to respond to a variety of settings, pedestrian needs, and site-specific security requirements;
• The number of elements and level of design complexity in a perimeter barrier system can be tailored to the complexity, significance, and sensitivity of a site;
• Placing perimeter barriers at the street edge, rather than at building entrances, protects pedestrians from deliberate or accidental injury by vehicles;
• Placing lobby barriers away from entrance doors creates a more open, welcoming environment;
• Placing perimeter barriers along the street rather than clustered around building entrances can reduce adverse visual impact on the historic building façade;
• Knowledge of below-grade conditions is critical to accurately estimate project complexity and avoid unnecessary expense;
• Early coordination with municipal officials is key to successful urban design in perimeter security installations.

In the hopes of raising the bar nationwide, GSA actively publicizes these prototype design approaches and is pleased to distribute design concepts, excluding engineering details of a sensitive nature. Our hope is to promote greater choice and higher quality. Design-build teams can tip the balance by encouraging opportunities to integrate amenities into perimeter security programs.

Acknowledgements

We wish to acknowledge the following individuals and firms who contributed to this article: lead principal Paul Westlake, Jr., FAIA, project director Amy Dibner, AIA, and designer Nick Doichev, AIA, of van Dijk Westlake Reed Leskosky; GSA Project Team: Metzenbaum project manager Pamela Wilczynski and Regional Historic Preservation Officer Regina Nally; landscape architect Neil Dean of Sasaki; Hinman Consulting Engineers’ blast expert Lorraine Lin; structural consultant Larry Prickett of Barber & Hoffman; William Spack of Cox Grae+ Spack, for the garden wall concept; Bruce Hall, GSA Security Engineer, and Steven Smith, AIA, Manager of GSA’s Glass Fragmentation program, Office of the Chief Architect, for reviewing and assisting with this paper; and Rolando Rivas-Camp, FAIA, Director of the Center for Historic Buildings, GSA Office of the Chief Architect, for supporting this work and tirelessly advocating good design.