2.7 Site Circulation Design
channels or a piped system with inlets and manholes.
These site strategies should coordinate with building
strategies such as vegetated roofs.
Site circulation design for GSA projects will vary greatly
In most cases building roof drainage will be collected
depending on the context, which can range from tight
by the plumbing system and discharged into the storm
urban sites to suburban campuses or isolated rural
drains; exceptions are small buildings in rural areas where
settings. Yet the basic criteria remain the same in all situ-
gutters and downspouts may discharge directly onto the
ations: the site design should segregate, at a minimum,
adjacent ground surface.
pedestrian access, vehicular access (including parking)
Most storm drainage systems will be designed for a 25-
and service vehicle access.
year minimum storm frequency, unless local criteria are
Security is an important consideration in site design.
Refer to Chapter 8: Security Design for detailed criteria
related to this matter.
Gravity Drainage. Storm drainage systems should always
use gravity flow.
Urban Site with Structured Parking
Location of Storm Drainage Pipes. Storm drainage pipes
will be located in unpaved areas wherever possible. It is
Service Traffic. Service dock access may be from an
desirable to offset inlets from main trunk lines to prevent
alley, from a below-grade ramp or from a site circulation
drive. If large trucks are to service the facility, sufficient
maneuvering space must be provided, and the service
Rainwater Harvesting. Strategies for rainwater
drive shall be screened as much as possible. It should
may be considered where appropriate, including filtering
always be separate from the access to the parking garage.
and retaining rainwater in cisterns for irrigation or
Where possible, a one-way design for service traffic is
flushing of toilets. Rainwater harvesting systems must
preferable to avoid the need for large truck turning areas.
comply with all local codes and standards.
The service area of the facility shall not interfere with
public access roadways. See Chapter 3: Architectural and
Interior Design for criteria on ramps and service areas.
Public Transportation. GSA encourages the use of public
transportation among employees and visitors. The poten-
tial need for a bus stop should be considered early in the
design of a GSA building in an urban setting and should
be discussed with planners of the mass transit system. The
project team should consider how to treat the orientation
of the building and the site design and landscaping to
encourage use of public transit and to address pedestrian
traffic `desire lines' between the building entrance and
Site Circulation Design
Revised March 2005 PBS-P100