This document summarizes an AIA-registered presentation about the design of a new library building located near Galveston Bay in Texas. The presentation discusses the sensitive coastal ecosystems in the area, including coastal prairies and marshes. It then describes how the library project incorporated low-impact development and resilient design strategies to protect the local environment and withstand hurricanes, including constructed wetlands, bioswales, underground detention/retention, and native/adaptive plant selection. Metrics are provided on how the design reduces runoff and filters stormwater.
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Stormwater Strategies
1. “English + Associates, Architects” is a Registered Provider with The
American Institute of Architects Continuing Education Systems (AIA/CES).
Credit(s) earned on completion of this program will be reported to
AIA/CES for AIA members. Certificates of Completion for both AIA
members and non-AIA members are available upon request.
This program is registered with AIA/CES for continuing professional
education. As such, it does not include content that may be deemed
or construed to be an approval or endorsement by the AIA of any
material of construction or any method or manner of
handling, using, distributing, or dealing in any material or product.
Questions related to specific materials, methods, and services will
be addressed at the conclusion of this presentation.
3. Course Description
The presentation centers around a case study of a new library building
recently construction approximately 1500 feet (less than 1/3 mile)
from Galveston Bay, in a sensitive ecosystem area also subject to storm
surges associated with periodic Hurricanes. The presentation includes
a review of the varied ecosystems present along the nearby Texas Gulf
Coast, focusing on responsible design in those areas already containing
significant development, and therefore unlikely candidates for large-
scale ecosystem preservation. The presentation will review the initial
site ecosystem assessment, development of LID and resilient design
strategies in the early design phases, and a more detailed description
of the systems ultimately incorporated in the site and building
design. These include re-constructed wetlands, bioswales,
underground detention and retention filtration methods, and native
and adaptive plant selection, as well as building envelope resilient
elements. Metrics associated with run-off rate reduction and storm
water filtration will also be provided.
4. Learning Objectives
1. Attendees will be able to understand the various ecosystems present
on the Texas Gulf Coast, and the importance of these systems in
protecting the health of the local natural environment.
2. Attendees will be exposed to various design strategies that mimic or
respond to coastal ecosystems in order to create resilient sites and
buildings.
3. Attendees will be able to identify potential plant selections for both
LID and salt water inundation environments.
4. Attendees will be able to identify the basic construction elements of
swales, bio-swales, wetlands, underground detention/retention, and
filtration systems.
At the end of this program, participants will be able to:
7. What is a Coastal Prairie
• Tall grass and shrubs
instead of trees.
• Hard clay layer
under the topsoil.
• Abundant amount of
rainfall. After
enough rainfall the
coastal prairie will
turn in to a coastal
marsh.
• Warm, moist, tropic
al air masses.
Definition of Wetland:
“Those areas that are inundated or saturated by surface
or groundwater at a frequency and duration sufficient to
support, and that under normal circumstances do
support, a prevalence of vegetation typically adapted for
life in saturated soil conditions. Wetlands generally
include swamps, marshes, bogs, and similar areas.”
8. Plant & Animal Species
Gayfeather Black-eyed Susan Little Bluestem Indiangrass
Ibis Red Tailed Hawk DragonflyButterfly
9. Ecological Services
Food
Plant and
animal species
Textiles and dyes
Medicine
Migration
Destination
Filtration of local and federal waters
Buffer from storm
surges
Plants supply oxygen
10. Dangers to Coastal Prairies
Pre-settlement there
were 9 million acres of
coastal prairies with
6.5 million of them in
Texas. Today less than
1% survive giving Texas
only 65,000 acres left.
Overgrazing
Extinction
There are less than
100 Attwater Greater
Prairie Chickens left
in the wild and is only
found in coastal
prairies.
Invasion of Exotic Plants
The Macartney Rose and Chinese
Tallow Tree are two of the most
problematic invaders.
People/Development
Encroachment
11. Restoration and Preservation of Coastal
Prairies
1. Preparation by
herbicide, solarization, or
tillage
2. Planting by
haying, seeding, so
dding, or
transplanting
3. Management by
mowing, irrigation, gr
azing, and fire
22. Plant Material for Bioswales
Blue Flag Iris
Wax mallow
Butterfly Iris Dwarf Katie Ruellia
Deep-rooted, native, salt water resistant plants are important factors to consider when picking
the plant material for a bioswale in a coastal prairie.
Cordgrass Gulf Coast Muhly
23. Design the Site with LID
•Total site area-218,150sf (or approx. 5 acres)
Building footprint-21,125sf
Developed footprint-55,900sf
Open space-141,125sf
•The site post developed runoff rate is less than the Pre-developed Run off rate
for the 2-year 24hr event.
•The site is designed as a series of overflows to slow the run off rate
dramatically from the pre-developed rate.
•The site as designed is capable of storing 10,300cf/storm event (or 77,049
gallons) within the combination of raintank, bioswales, and rain
garden and the amount of detention is 25,720 cf.
•Amount of water stored onsite and used for irrigation during the July design
case – 77,123gals captured during the month allowing for a 109%
reduction in potable water use for the month of July.
•Over 80% of the suspended solids are removed from over 90% of the storm
runoff
•Plant type was designed to be native drought tolerant plants. The plants also
were to be able to withstand the salt environment and handle
sustained wet conditions during the storm events.
24. Materials
•Building envelope designed for high wind loads
•Roof is rated for 190mph storm
•Building structure is rated for 120mph
•Coiling storm doors are rated for 140mph
•Curtainwall system is rated for 130mph
•Limited glazing not protected by shutters
•Non shuttered glazing is large missile impact
laminated double insulated semi reflective Low-E
glazing
•Minimal use of wood and other nondurable materials
•Minimized cantilevers, fins, and overhangs
26. What Our Client Asked For
• Code Minimum
• Withstand forces similar to Hurricane Ike without
damage
• Meet current needs of library plus be able to expand
with technology
• Warm and inviting to community
What They Didn’t Ask For
• Highly sensitive to local environment
• LEED [Did ask for further along in the process]
• Take advantage of natural systems beyond local
regulatory requirements for the site design
