HomeMy Public PortalAbout130_020_2nd Reading Ord 17-2013 footings MAYOR • , CITY MANAGER
Jason Buelterman 4 Diane Schleicher
•
CITY COUNCIL CLERK OF COUNCIL
Wanda Doyle, Mayor Pro Tern
: Janet LeViner
Barry Brown r'•'
Jan Fox CITY ATTORNEY
Bill Garbett t 'rr I Edward M.Hughes
Tom Groover
Paul Wolff
CITY OF TYBEE ISLAND
City Council Agenda Item Request
Agenda Item Requests and supporting documentation must be submitted to the Clerk of Council by
4:00PM on the Thursday prior to the next scheduled Council meeting. If this form is received after the
deadline,the item will be listed on the next scheduled agenda.
Council Meeting Date for Request: May 23, 2013
Item: Public Hearing
Explanation: Text Amendment—Section 9-050 Technical Codes Adopted—Second Reading
Budget Line Item Number(if applicable): N/A
Paper Work: -V Attached*
Audio/Video Presentation**
* Electronic submissions are requested but not required. Please email to
j leviner @cityoftybee.org,
** Audio/video presentations must be submitted to the IT department at City Hall
by 4:00PM on the Thursday prior to the scheduled meeting.
Submitted by: Dianne Otto
Phone/Email: (912)472-5031 /dotto @cityoftybee.org
Comments:
Date given to Clerk of Council: May 15, 2013
* * *
P.O.Box 2749—403 Butler Avenue, Tybee Island, Georgia 31328-2749 *Certified*
(866) 786-4573—FAX(866)786-5737 1 City of
1 st Ethics .1
www.cityoftybee.org
ORDINANCE NO. 17-2013
AN ORDINANCE TO AMEND THE CODE OF ORDINANCES
FOR THE CITY OF TYBEE ISLAND, GEORGIA
ESTABLISHING SECTION 9-050(D)RELATING TO FOOTINGS
WHEREAS, the duly elected governing authority for the City of Tybee Island, Georgia, is
authorized under Article 9, Section 2, Paragraph 3 of the Constitution of the State of Georgia to adopt
reasonable ordinances to protect and improve the public health, safety, and welfare of the citizens of
Tybee Island, Georgia, and
WHEREAS, the duly elected governing authority for the City of Tybee Island, Georgia, is the
Mayor and Council thereof,and
WHEREAS, the governing authority desires to adopt ordinances under its police, zoning, and
home rule powers,and
WHEREAS, the City of Tybee Island desires to establish Section 9-050(D) regarding the Code
requirements for footings;
NOW, THEREFORE, it is hereby ordained by the governing authority of the City of Tybee
Island:
SECTION 1
That Section 9-050(D)is hereby created and shall read as follows:
Sec. 9-050. Technical codes adopted.
(D) Adopted in addition to the technical codes of section 9-050(A) is a local requirement
that all pier footings shall be a minimum of 36-inches wide by 36-inches wide by 36-inches deep
with concrete being a minimum of 20-inches thick. The bottom of the concrete is to be a minimum
of 36-inches below natural grade. All stemwall footings and monolithic slab footings shall be a
minimum of 20-inches wide by 24-inches thick. The bottom of the concrete is to be a minimum of
24-inches below natural grade. All footings shall have reinforcing steel as required.
SECTION 2
The sections, paragraphs, sentences, clauses and phrases of this ordinance are severable
and, if any phrase, clause, sentence, paragraph, or section of this ordinance shall be declared
illegal or invalid by the valid judgment or decree of any court of competent jurisdiction, such
illegality shall not affect any of the remaining phrases, clauses, sentences, paragraphs and
sections of this ordinance.
SECTION 3
All ordinances and parts of ordinances in conflict herewith are expressly repealed.
SECTION 4
It is the intention of the governing body, and it is hereby ordained, that the provisions of
this ordinance shall become effective and be made a part of the Code of Ordinances, City of
Tybee Island, Georgia, and the sections of this ordinance may be renumbered to accomplish such
intention.
SECTION 5
This ordinance shall be effective upon its adoption by the Mayor and Council pursuant to
the ordinances of the City.
ADOPTED THIS DAY OF , 2013.
MAYOR
ATTEST:
CLERK OF COUNCIL
FIRST READING:
SECOND READING:
ENACTED:
Tybee/Ordinances/2013/17-2013—Sec 9-050(D)footings 04.30.13
C e.rev Feld,637 coo,
1 1rc., W MEMORANDUM
0 4,, 1777 ,er
F - ' P
DATE: April 2, 2007
TO: All Code Inspectors
FROM: Clifford A. Bascombe
SUBJECT: Foundations at Tybee
For your information we will enforce the following for foundations at Tybee:
A. For interior piers the foundation will be 3 feet by 3 feet,with concrete being 20 inches thick and
the bottom of the concrete must be 36 inches below grade.
B. Footings for stern wall footing will be 20 inches wide by 20 inches thick with the bottom of the
concrete 24 inches below grade.
C. Monolithic slabs will be 20 inches wide by 24 inches thick minimum with the bottom of the
concrete 24 inches below grade.
Erosion, Scour, and 4r
Foundation Design FEMA
FNDSE http://www.fema.gov
HURRICANE IKE RECOVERY ADVISORY
Purpose: To discuss how any lowering of the ground surface can affect the ability of a building foundation to
resist design loads, and to provide additional guidance for coastal foundation design.
Key Issues
• Coastal buildings are often subject to flood loads Erosion refers to a general lowering of the
and conditions that do not affect inland buildings. ground surface over a wide area.
These include waves, high velocity storm surge
flow,floodborne debris, and erosion and scour. This Scour refers to a localized loss of soil, often
Recovery Advisory will focus on erosion and scour. around a foundation element.
See FEMA 499, Home Builder's Guide to Coastal
Construction (2005), Fact Sheets 11 through 15 at:
http://www.fema.gov/library/viewRecord.do?id=1570, and FEMA 55, Coastal Construction Manual (2000)
at: http://www.fema.gov/library/viewRecord.do?id=1671 for discussion of other foundation issues.
• Foundations must transfer all loads imposed on the building into the ground. If the foundation is not strong
enough or deep enough to do this,the building will be destroyed. If the foundation embedment into the
ground is not sufficient to account for erosion and scour that may occur over the life of the building,the
building is vulnerable to collapse under design flood and wind conditions.
• Predicting the incidence, location, and magnitude of coastal erosion and scour is difficult, and present-day
building codes and standards do not prescribe clear-cut solutions for designers. Therefore, designers should
be conservative with their foundation designs. This means foundations may need to be stronger, deeper, and
higher than what has historically been used. Lessons learned from Hurricane Ike and other recent coastal
storm events should be incorporated into foundation designs.
Erosion and Scour Basics
Erosion is defined by the International Building Code® (ICC, 2006) as the "wearing away of the ground surface
as a result of the movement of wind, water or ice." Section 7.5 of FEMA's Coastal Construction Manual
describes erosion as "the wearing or washing away of coastal lands." Since the exact configuration of the soil
loss is important for foundation design purposes, a more specific definition is used in this Recovery Advisory
(see text box and Figure 1).
Original Original
Ground Ground
`w 1/Erosion
Erosion Scour and Scour
Figure 1.Distinguishing between coastal erosion and scour.A building maybe subject to either or both,depending on the building location,
soil characteristics,and flood conditions.
Erosion,Scour,and Foundation Design January 2009 Page 1 of 8
Erosion can occur across a wide range of timeframes 4 - f : ° - -
- it can be gradual, occurring over a long period of time ,. '"' -•
(many years); more rapid, occurring over a relatively short „ t
period of time (weeks or months); or episodic, occurring '_ ,, "--. " _ni a 4
during a single coastal storm event over a short period of p- --1z----
time (hours or days). Figure 2 shows the result of erosion ag
occurring over a long timeframe- buildings that were ;___.-At.--.-- � '"` R ib' `,
formerly on upland property, but now stand on the active • ,�. A- Er ' . . -,.. r : W -1 's` r,
beach. Figure 3 shows episodic erosion that occurred -
during Hurricane Ike. In both cases,the recession of the -"" "'- ---' •- ^•---
shoreline resulted in a horizontal translation of the beach
profile and a lowering of the ground elevation under and
near the affected buildings. The closer a building is to
the shoreline,the more likely erosion will occur and the
greater the erosion depth will be. Figure 2.Long-term erosion has caused the shoreline to
retreat and has left homes standing on the beach(Surfside
Scour occurs when floodwater passes around Beach,Tx).July 2007 Texas General Land Office photo.
obstructions in the water column. As the water
flows around an object, it must change direction and iii,o -
accelerate. Soil can be loosened and suspended by this IT -=-- _
process or by waves striking the object, and be carried
away. Pilings, pile caps, columns, walls,footings, slabs, i
and other objects found under a coastal building can lead • k I
to localized scour. Scour effects increase with increasing . 1 . ';
flow velocity and turbulence, and with increasing soil 11
erodibility. t T
H
Scour effects are generally localized, ranging from small, �+ r �� - p M I M
shallow conical depressions in the sand around individual
piles (Figure 4)to larger and deeper depressions around _
individual piles (Figure 5),to a building-sized shallow - - ' _
depression around a group of piles (Figure 6),to a large r
and deep depression around a building foundation Figure 3.Storm-Induced erosion beneath an elevated coastal
(Figure 7). Scour depressions like that shown in Figure building(Galveston Island,Tx,Hurricane Ike).
7 were observed frequently following Hurricane Ike,
and many of these reportedly were 6 to 10' deep and F E.�
required hundreds of cubic yards of soil to fill. The a
presence of large, non-frangible concrete slabs and deep �' a
grade beams under the buildings may be a contributing r• :`
factor to the large local scour depressions observed.
In some cases, buildings may settle due to inadequate `i A
pile embedment, coupled with some combination of
erosion, scour, and soil liquefaction that leads to loss of y x r.,
bearing. This type of failure was observed by the Huricane s' � + -- ' ```
Ike FEMA Mitigation Assessment Team (MAT) at Surfside
Beach,TX (Figure 8) and Holly Beach, LA. f T , ;r 1
1 u ti ..2. Figure 4.Local scour around foundation plies(Pensacola
Beach,FL,Hurricane Ivan).
} Figure 5.Local scour around foundation piles(Holly Beach,
. LA,Hurricane Ike).
Erosion,Scour,and Foundation Design January 2009 Page 2 of 8
aI
141111111111111-.- 1111
ap...0;:'‘,--,..:_. _ ___ — — 7;-...- - c - ' ----
T4 - .
: !t ' as ! i
I
Figure 6.Local scour around a 3rd row house's pile foundation Figure 7.Extreme local scour around a Gulf-front pile
(Bolivar Peninsula,TX,Hurricane Ike). foundation(Bolivar Peninsula,TX,Hurricane Ike).
- 1
�i
41141: 1 -,. -
. ,� � ---. ��� � . �,�f � ! I Ill � { �1��� � ° 7.
-
dd e1 �-• 111W•1
• :
Figure 8.Differential settlement of buildings thought to be Figure 9.Linear scour and erosion patterns aligning with
a result of inadequate foundation embedment coupled with canals and roads(Bolivar Peninsula,TX,Hurricane Ike).
erosion,scour,and/or soil liquefaction(Surfside Beach,TX,
Hurricane Ike).
There is one other erosion and scour scenario to consider in foundation design —the loss of soil around
or under a building as a result of storm surge flow being channeled or directed across a building site. This
process usually takes place where storm surge flow is constrained between large buildings or gaps in shore
protection, or when return flow to the sea follows paths of least resistance, such as along canals and roads
(Figure 9).
Erosion and Scour - Impacts on Foundations
Erosion and scour have several adverse impacts on coastal foundations:
• Erosion and scour reduce the embedment of the foundation into the soil, causing shallow foundations to
collapse and making buildings on deep foundations more susceptible to settlement, lateral movement, or
overturning from lateral loads.
• Erosion and scour increase the unbraced length of pile foundations, increase the bending moment to which
they are subjected, and can overstress piles.
• Erosion over a large area between a foundation and a flood source exposes the foundation to increased
lateral flood loads (i.e., greater stillwater depths, possible higher wave heights, and higher flow velocities).
• Local scour around individual piles or a building foundation will not generally expose foundations to greater
flood loads, but linear scour across a building site may do so.
Erosion,Scour,and Foundation Design January 2009 Page 3 of 8
Resisting higher bending moments brought about by erosion and scour may necessitate a larger pile cross-
section or decreased pile spacing(i.e., more piles) or,in some cases, use of a different pile material (e.g.,
concrete or steel instead of wood). Resisting increased lateral flood loads brought about by erosion (and
possibly by linear scour)would necessitate a similar approach. However, designers must remember that
increasing the number of piles or increasing the pile diameter will, in turn,also increase lateral flood loads
on the foundation.
Resisting increased unbraced lengths brought about by erosion and scour will require additional
embedment of the foundation into the ground.
To illustrate these points, calculations were made to examine the effects of erosion and scour on foundation
design for a simple case—a 32' x 32',two-story house (10' story height), situated away from the shoreline
and elevated 8' above grade on 25 square timber piles (spaced 8' apart), on medium dense sand. The house
was subjected to a design wind event with a 130-mph (3-second gust) wind speed and a 4' stillwater depth
above the uneroded grade, with storm surge and broken waves passing under the elevated building. Lateral
wind and flood loads were calculated in accordance with ASCE/SEI 7-05 Minimum Design Loads for Buildings
and Other Structures (model codes and related prescriptive standards, such as the International Building
Code (IBC),the International Residential Code® (IRC®), and ICC-600 Standard for Residential Construction in
High Wind Areas,are based on ASCE 7 loads). For this illustration,the piles were analyzed under lateral wind
and flood loads only; dead, live and wind uplift loads were neglected. If these neglected loads are included in
the analysis, deeper pile embedment and possibly larger piles may be needed.
Three different timber pile sizes (8" square, 10" square, and 12" square) were evaluated using pre-storm
embedment depths of 10', 15', and 20', and five different erosion and scour conditions (Erosion = 0' or 1';
Scour ranges from 2.0 times the pile diameter to 4.0 times the pile diameter). The results of the analysis are
shown in Table 1. A shaded cell indicates the combination of pile size, pre-storm embedment, and erosion/
scour does not provide the bending resistance and/or embedment required to resist lateral loads. The
reason(s) for a foundation failure is indicated in each shaded cell, using "P" for failure due to bending and
overstress within the pile and "E" for an embedment failure from the pile/soil interaction. An unshaded cell
with "OK" indicates bending and foundation embedment criteria are both satisfied by the particular pile size/
pile embedment/erosion-scour combination.
Table 1.Example foundation adequacy calculations for a two-story house supported on square timber piles and situated away from
the shoreline,storm surge and broken waves passing under the building,130-mph wind zone,soil=medium dense sand.Shaded cells
Indicate the foundation fails to meet bending(P)and/or embedment(E)requirements.
Pile Embedment Erosion and Scour Conditions Pile Diameter, a
Before Erosion and Scour 8 inch 10 inch 12 inch
Erosion =0,Scour= 0 P, E E OK
Erosion = 1 foot,Scour= 2.0 a P, E E E
10 feet Erosion = 1 foot,Scour= 2.5 a P, E E E
Erosion = 1 foot,Scour=3.0 a P, E E E
Erosion = 1 foot,Scour= 4.0 a P,E P, E E
Erosion = 0,Scour= 0 P OK OK
Erosion = 1 foot,Scour= 2.0 a P OK OK
15 feet Erosion = 1 foot,Scour=2.5 a P OK OK
Erosion = 1 foot,Scour=3.0 a P ^4 OK OK
Erosion = 1 foot,Scour= 4.0 a P, E s P, E E
Erosion = 0,Scour= 0 P OK OK
Erosion = 1 foot,Scour= 2.0 a P OK OK
20 feet Erosion = 1 foot,Scour= 2.5 a P OK OK
Erosion = 1 foot,Scour= 3.0 a P OK OK
I Erosion = 1 foot,Scour=4.0 a P P OK
Erosion,Scour,and Foundation Design January 2009 Page 4 of 8
Review of the table shows several key points:
• Increasing pile embedment will not offset foundation
inadequacy (bending failure) resulting from too small
a pile cross-section or too weak a pile material.
WARNING
• Increasing pile cross-section (or material strength) will
not compensate for inadequate pile embedment The results in Table 1 should not be used In
lieu of building-and site-specific engineering
• Given the building and foundation configuration used analyses and foundation design. The table
in the example,the 8" square pile is not strong is for Illustrative purposes only and Is based
enough to resist the lateral loads resulting from the upon certain assumptions and simplifications,
130-mph design wind speed under any of the erosion and for the combinations of building
and scour conditions evaluated, even if there is no characteristics,soil conditions,and wind and
erosion or scour. Homes supported by 8" square flood conditions described above. Registered
timber piles,with embedment depths of 10' or less, design professionals should be consulted for
will likely fail in large numbers when subjected to foundations designs.
design or near-design loads and conditions. Homes
supported by deeper 8" piles may still be lost during
a design event due to pile (bending) failures
• The 10" square pile is strong enough to resist bending under all but the most severe erosion and scour
conditions analyzed.
• The 12" pile is the only pile size evaluated that satisfies bending requirements under all erosion and scour
conditions analyzed. The 12" pile works with 10' of embedment under the no erosion and scour condition.
However, introducing as little as 1' of erosion, and scour equal to twice the pile diameter, was enough to
render the foundation too shallow.
• 15' of pile embedment is adequate for both 10" and 12" piles subject to 1' of erosion and scour up
to three times the pile diameter. However, when the scour is increased to four times the pile diameter
(frequently observed following Hurricane Ike), 15' of embedment is inadequate for both piles. In general
terms, approximately 11' of embedment is required in this example house to resist the loads and conditions
after erosion and scour are imposed.
• The 12" pile with 20' of embedment was the only foundation that worked under all erosion and scour
conditions analyzed. This pile design may be justified for the sample house analyzed when expected erosion
and scour conditions are unknown or uncertain.
NFIP and Building Code Requirements
One of the requirements of Section 60.3(a)(3) of the NFIP regulations that applies to all flood hazard zones
(V, VE,V1-30, A, AE, A1-30,AO,AH, etc.) within the Special Flood Hazard Area (SFHA) is:
"If a proposed building site is in a flood-prone area, all new construction and substantial improvements
shall be designed (or modified) and adequately anchored to prevent flotation, collapse, or lateral
movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of
buoyancy."
A requirement in Section 60.3(e)(4) states that all new construction and substantial improvements in V
zones must be elevated on pilings and columns so that:
"(i) the bottom of the lowest horizontal structural member of the lowest floor(excluding the pilings or
columns) is elevated to or above the base flood level; and
(ii)the pile or column foundation and structure attached thereto is anchored to resist flotation, collapse
and lateral movement due to the effects of wind and water loads acting simultaneously on all building
components.
Water loading values used shall be those associated with the base flood. Wind loading values used shall
be those required by applicable State or local building standards. A registered professional engineer or
architect shall develop or review the structural design, specifications and plans for the construction, and
shall certify that the design and methods of construction to be used are in accordance with accepted
standards of practice for meeting the provisions of paragraphs (e)(4)(i) and (ii) of this section."
Erosion,Scour,and Foundation Design January 2009 Page 5 of 8
The International Residential Code (2006) has similar requirements:
"R324.1.1 [Flood Resistant Construction] Structural systems. All structural systems of all buildings and
structures shall be designed, connected and anchored to resist flotation, collapse or permanent lateral
movement due to structural loads and stresses from flooding equal to the design flood elevation.
R324.3.3 [Coastal high-hazard areas] Foundations. All buildings and structures erected in coastal high-
hazard areas shall be supported on pilings or columns and shall be adequately anchored to such pilings
or columns. Pilings shall have adequate soil penetration to resist the combined wave and wind loads
(lateral and uplift). Water loading values used shall be those associated with the design flood. Wind
loading values used shall be those required by this code. Pile embedment shall include consideration of
decreased resistance capacity caused by scour of soil strata surrounding the piling. Pile systems design
and installation shall be certified in accordance with Section R324.3.6. Mat, raft or other foundations that
support columns shall not be permitted where soils investigations that are required in accordance with
Section R4O1.4 indicate that soil material under the mat, raft or other foundation is subject to scour or
erosion from wave-velocity flow conditions.
Buildings and structures, and all parts thereof, shall be constructed to support safely all loads, including
dead loads, live loads, roof loads,flood loads, snow loads,wind loads and seismic loads as prescribed in
this code. The construction of buildings and structures shall result in a system that provides a complete
load path capable of transferring all loads from their point of origin through the load-resisting elements of
the foundation."
Thus, designers are responsible for ensuring that a foundation for a building in any flood hazard area must
be adequate to support a building under applicable design loads and load combinations. Designers must
consider the effects of erosion and scour when foundations are designed. Designers must certify the
foundations.
There may also be other (State or local) foundation design and certification requirements.
Erosion and Scour Design Guidance
Given that the design requirements listed above are performance requirements, designers must translate
those into practice. This can be difficult with respect to estimating erosion and scour conditions at a particular
site, since definitive guidance for estimating coastal erosion and scour is not present in building codes and
standards.
FEMA's Coastal Construction Manual (FEMA, 2000) provides some information and guidance, but even
this should be considered preliminary and subject to improvement as we learn more from post-storm
investigations. The pertinent CCM sections and guidance are summarized below:
CCM Section 7.5: this section summarizes the causes of erosion, its impacts on coastal lands and
buildings, and how it is measured. Section 7.5.2.5 discusses local scour. One key point is a procedure
outlined in the note on page 7-28 and illustrated in CCM Figure 7-66—three steps that a designer should
use to estimate future ground elevations and flood conditions at a site:
Step 1: determine the most landward shoreline location expected during the life of the building
Step 2: define the lowest expected ground
elevation during the life of the building Designers in Texas and Louisiana can obtain
Step 3: define the highest expected BFE during erosion data and other related information from
the life of the building various state agencies (see References).
CCM Section 7.8.1.4 discusses FEMA's current
procedures for estimating storm-induced erosion.
CCM Section 7.9.2 discusses how designers can update an obsolete flood hazard description for a site
by accounting for long-term (Step 1 above) and storm-induced erosion (Step 2 above). CCM Figure 7-
67 (Figure 10) provides an example, illustrating the use of published long-term erosion information and
simple storm erosion calculations to estimate future ground elevations at a building site.
CCM Section 11.6.11 discusses local scour and presents a simple method for calculating erosion around
a single pile. The method predicts the depth of a scour depression below the eroded ground elevation
Erosion,Scour,and Foundation Design January 2009 Page 6 of 8
is equal to 2.0 times the pile diameter, unless
non-erodible soil lies beneath the ground surface 25 150 feet(9 feet/year x50years)
(Figure 11).
erosion(Given:
average
io
Designers should use the CCM scour depth
relationship (Smax = 2.0 a) with caution.
15
Observations after Hurricane Ike showed scour o _ /� 100-Year Stillwater Level
exceeded twice the pile diameter at many locations. X10
This could have been due to deeper scour depths g
around entire pile foundations (Figures 6 and 7), 5 —
or to the presence of concrete slabs and deep i — Today
—
grade beams that channeled flow between the 0 50-Year
bottom of the slab and the soil, or to other factors. --- "°" °'"'
Given the uncertainty over the exact cause of local -5
scour during Hurricane Ike, foundation designs for 0 100 200 300 400 500 600 700 600
reconstruction along the Gulf shoreline should be Distance(feet)
very conservative, and an assumed scour depth
of 6 to 8' would not be unreasonable. Designers Figure 10.CCM Figure 7-67 Illustrating a simple procedure to
should investigate local soils and Hurricane Ike- account for long-term erosion and storm erosion.
induced scour at nearby locations before selecting
a scour depth. Post-hurricane aerial photographs, Flood Elevation a
such as those obtained after Hurricane Ike by NOAH Eroded Ground
Surface
and USGS (see References) will provide a good Pile
source of data for designers. --�
The CCM mentions linear scour channels occurring Direction of Flow
between large buildings or in-line with roads,
d —� With Terminating Stratum
canals, and drainage features (see CCM Section ,,
8.3.2), but does not provide design guidance for ,
estimating linear scour depths. As w as the case ;:.:? °\::`:;.. .=r.:::.:... :: ::......:.�.,1...:�:.:::.....=:.:..:.:.;..:.=•°`:.-:'`.::_..:•.:.`•:::••...:.°:?•:'::'..�:..:.;.;,
with local scour, designers should utilize post
hurricane data when they estimate linear scour '`': Sm ':::; "> :°:c•: ':.:: ::;::;: ;::.•:;.:::NonrErodanie son or Bedrock::::
likelihood and depth. c withoutTerminetin =''`
Stratum;
Existing Homes:Are the Pile Foundations Figure 11.CCM Figure 11-12 Illustrating scour estimate
Adequate? around a single pile-Hurricane Ike showed this method may
underestimate local scour.
The owner of an existing home may wonder whether
the pile foundation is adequate to withstand erosion and scour during a design event. The builder or building
official may have permit records, building plans, or foundation design information for the house, or may be
able to provide information about typical design requirements, construction practices, and probable pile
embedment depths for houses of the same age. A licensed engineer can perform an inspection of the
foundation, provide information about non-destructive testing methods to determine pile embedment depth,
review available foundation data, and analyze the foundation.
References
ASCE. 2005. Minimum Design Loads for Buildings and Other Structures. ASCE/SEI 7-05.
FEMA. 2000. Coastal Construction Manual, 3rd ed. FEMA 55.
FEMA. 2005. Home Builder's Guide to Coastal Construction. FEMA 499. See http://www.fema.gov/library/
viewRecord.do?id=1570
ICC 2006. International Building Code.
ICC 2006. International Residential Code with 2007 Supplement.
ICC 2008. Standard for Residential Construction in High Wind Areas. ICC 600.
Louisiana Department of Natural Resources. 2008. Coastal Restoration and Management data and reports.
See http://dnr.louisiana.gov/crm/
Erosion,Scour,and Foundation Design January 2009 Page 7 of 8
NOAA. 2008. Post-Ike aerial photographs. See http://ngs.woc.noaa.gov/ike/index.html
Texas Bureau of Economic Geology. 2008. Coastal Studies Program data and reports. See http://www.beg.
utexas.edu/coastal/coasta101.htm
USGS. 2008. Post-Ike aerial photographs and data. See http://coastal.er.usgs.gov/hurricanes/ike/
Erosion,Scour,and Foundation Design January 2009 Page 8 of 8