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OCR for page 18
18 A Handbook for Addressing Water Resource Issues Affecting Airport Development Planning
Summary of Fact Sheet 3:
Storm Water Quantity and Floodplains
Many of the most common airport development projects can affect the quantities of storm
water discharged from the airport site. Those storm water discharges can in turn affect the
propensity for regional flooding and runoff-related impacts. Airports are frequently located near
water bodies and as such, airport projects can affect, and be affected, by floodplains.
Regulation of storm water quantities associated with development projects has occurred pri-
marily at municipal, regional, and state levels to date. Storm water quantity regulations are typ-
ically designed to protect downstream infrastructure and minimize flooding during large,
infrequent storm events. The regulations often include requirements allowing little, if any,
change in the runoff quantities before and after development projects. A series of federal orders
and guidelines, plus some state regional requirements have been enacted and developed to pro-
tect floodplains. The key elements of the regulatory framework include developments within a
floodplain, increases to flood elevations, and changes to runoff inside the floodplain.
Airport development projects that involve construction of new impervious surfaces (e.g.,
pavement, buildings) in previously undeveloped areas are typically the types of projects most
affected by storm water quantity and floodplain regulations. Projects where one type of imper-
vious surface is replaced by another typically are not affected significantly.
Project planning and design considerations typically associated with storm water quantity and
floodplain regulation compliance include the following:
· Does the project extend into the 100-year floodplain?
· Will the project's unavoidable location result in additional flooding or endanger human life?
· What are regulatory requirements governing flow rates and volumes from new developments?
· Is there an existing storm water runoff and transport model to characterize discharges?
· Will any storm water be diverted to a new discharge location and new watershed?
· Will storm water detention be required to meet regulatory requirements, how much space will
it require, and where will it be located?
· Will storm water detention cause issues with wildlife attractants?
· Will storm water piping and pumping be required to convey storm water to detention struc-
tures, treatment facilities, or new discharge locations?
The process for assessing core regulatory requirements, determining the measures needed for
compliance, and reducing the effects of managing storm water quantity and floodplain issues on
the development project are presented in Fact Sheet 3 in Appendix B. A summary of the guid-
ance for reducing those project impacts follows.
Guidance for Reducing Project Impacts from Managing Issues
Associated with Storm Water Quantity and Floodplains
Water Resource Inventory Create an inventory for storm water data that
includes maps of airport areas with flooding issues
and capacity limitations. Understand the source of
the floodplain boundaries obtained from federal
agencies and include mapping of floodplain
boundaries in the inventory. The boundaries in
Flood Insurance Rate Map (FIRM) documents may
not be accurate on smaller project scales.
OCR for page 19
Handbook Overview 19
Modeling, Calculations, Coordinate with regulators to determine approved
and Analyses modeling programs, calculation protocols, and
level of detail that may be acceptable. Identify
the appropriate level of detail to collect in sup-
port of modeling and analyses and provide a
reasonable estimate of storm water discharges
(e.g., select a minimum pipe size or drainage
basin size to be modeled).
Conceptual Planning Consider development of a storm water master
plan or integrating storm water master planning
into airport master planning. Master plans may
be useful for considering the storm water needs
for long-term or phased development, in addi-
tion to widespread development.
Control Siting Consider potential floodplain impacts associated
with long-term development as part of storm
water master planning process. Identify and
characterize potential sites for controls in the
Conceptual Planning Phase. Avoid impacts inside
the floodplain, where possible.
Design Implementation Build infiltration and temporary storage into devel-
opment project design where possible to reduce
extent of necessary end-of-pipe controls. Avoid
project-by-project designs of controls that do not
consider effects to overall airport storm water
drainage. Consider the need for modifications to
controls to minimize attraction of hazardous
wildlife.
Construction of Controls Coordinate design and construction of controls
with design and construction of the develop-
ment project to avoid development project
delays from unfinished work.
Scheduling and Sequencing Reduce management and consultant costs with
well-planned and coordinated schedules for
development project and storm water quantity
assessments.
Stakeholder Coordination Coordinate with local agencies, property owners,
and regulators to assist with identifying core reg-
ulatory requirements, interests, and data on local
flooding issues.
