Waterfront + Floodplain Experience by VIA design architects, pc

Waterfront + Floodplain Experience 2015

floodproof design research new construction floodproof design research floodproof design matrix VIA design has researched and analyzed six approaches to floodproof design for review and evaluation during the design phase of new construction projects. They are: 1. Permanent - fixed construction on piles, elevated permanently above the site’s flood elevation. This method is approved by FEMA. 2. Contingent construction, with the floor below the maximum flood elevation and protected against flood damage with a variety of measures. This method may be permitted in Virginia in accordance with executive memorandum 2-97. Four alternatives may be considered: a. fixed flood proof-construction below the flood elevation, with flood gates/shields b. amphibious - the structure floats during floods c. “jack-up” - the structure is elevated mechanically prior to flooding d. portable - the structure is removed from the site to a safe location prior to flooding 3. Emergency - no special construction, the building is protected with sandbags during flooding. This approach is not permitted for new buildings. The following pages contain the matrix which was designed by VIA design architects to introduce the six floodproof design approach types and lists their advantages and disadvantages, with additional advantages and disadvantages listed in the matrix in “red”. floodproof design analysis matrices VIA design has also developed several floodproof design analysis matrices that serve to help the design team and client to analyze and establish the best approach for a project based on cost and design factors. The following pages contain a sample of three of the matrices developed: 1. The cost matrix compares first-glance cost in each of six categories as compared to conventional construction 2. The design attributes matrix rates each system on how well it would be able to satisfy the project goals 3. The cost factors matrix identifies the factors which might contribute to a higher cost in each area existing building floodproof design research floodproofing study + standards VIA has conducted numerous floodproofing studies for various clients and is knowledgeable and experience using FEMA, NFIP, and USACE floodproofing regulations. The following pages contain common floodproofing practices for existing buildings. alternative concepts for consideration In addition to the commonly recommended floodproofing practices, VIA design has studied and analyzed alternative concepts for floodproofing that serve to enhance the architecture of an existing structure as well as provide functional floodproofing. While not fully developed or engineered for the special needs of each project, these show VIA’s ability to think creatively and bring innovative ideas to the table. The following pages contain two examples of these alternative concepts.

floodproof PROJECT OVERVIEW design research: NEW CONSTRUCTION FLOOD PROOF DESIGN MATRIX

· Permittable · Dependable · Proven / low-risk · No intervention required · Gain site area below the building for storage / parking · Low maintenance · Transparency through the structure viewed from the street

· Inaccessible · Functional connection to the site is lost · Loading / unloading of trucks becomes diﬃcult · Context - an elevated structure would be out of place in Wachapreague

· Floor loading a non-issue · Equalization of flood water forces if allowed to flood through · Opportunity for lower finished floor · Aesthetically more in character with the town · Workability and daily operations are improved · High level of predictability for overall building performance · Flexible-Choice of implementing the moving parts (e.g. floodgates)

· Approval/permitting may be difficult · Electric switches cannont be any higher than 48” above the floor (ADA) so they may not be completely above the flood elevation depending on finished floor elevations chosen for building · Moveable parts require maintenance, training, and storage

“CONTINGENT” - Fixed - Amphibious - Jack-Up - Portable

“FIXED” - ﬂood proof walls + shields

· The area below the building must be protected · Uniform ﬂoor loading becomes as issue grade · Favors dividing the total square footage needed into several smaller buildings · Does not require power · Unlimited openings in the building skin

· Community concerns due to the unusual nature of the building - “Will it break lose in a storm and end up on

· Aesthetically more in character with the town · Workability and daily operations are improved · High level of predictability for overall building performance · Flexible-Choice of implementing the moving parts (e.g. ﬂoodgates)

the flood elevation depending on finished floor elevations chosen for building · Moveable parts require maintenance, training, and storage

floodproof design research: NEW CONSTRUCTION FLOOD PROOF DESIGN MATRIX

(continued)

· Community concerns due to the unusual nature of the building - “Will it break lose in a storm and end up on top of the house?” · Unlimited openings in the building skin are possible · Provides the opportunity for innova-

· Permittable · Dependable · Proven / low-risk · No intervention required · Gain site area below the building for storage / parking ·· Low maintenance · Transparency through the structure fromcan thebe street · viewed Finish ﬂoor close to grade

· Inaccessible · Functional connection to the site is lost · Loading / unloading of trucks becomes diﬃcult · Context - an elevated structure would be out ofpower place in Wachapreague · Requires

below · Steady ﬂoor during a storm · Minimal structure for waves to beat against · Minimal structure for waves to beat against

· Design cost

· Low maintenance · Low tech

· Requires an alternate oﬀ-site

· Systems must be maintained · Complex components

“CONTINGENT” - Fixed - Amphibious - Jack-Up - Portable

“FIXED” - ﬂood proof walls + shields

· Finish ﬂoor can be close to grade

· Large amounts of equipment and man power required to relocate the buildings

which can save money - building segments could also be craned onto a large barge to be taken

· Finish ﬂoor can be close to grade more easily ﬁt into the Wachapreague vernacular

· Man power required before and during storms to protect the building · High risk of damage to the building · Materials become limited to corrosion/ moisture proof choices · Systems will always be at risk · Not desired by VIMS

· Community concerns due to the unusual nature of the building - “Will it break lose in a storm and end up on

floodproof PROJECT OVERVIEW design research: NEW CONSTRUCTION floodproof design analysis matrices

COST MATRIX (1-10, Low-High)

Pe rm an Fix ent ed F Am lood Pro ph ibi of ou Jac k-U s p Po rta ble

In order to help analyze and determine the best floodproofing approach for a waterfront project, VIA design created a set of cost and design attribute matrices in order to compare and contrast the different construction approaches and weigh the benefits of cost and design at an early stage of the project.

Site

Foundation

Super Structure

Materials/Finishes

Systems

Special Requirements

Totals

s ble

Aesthetics

Accessibility Regulatory

Accessibility Day-to-Day

Maintenance

Survivability

Recovery

Permitting

Simplicity

Dependability

Bi-Product: Increased Users

rta

Jac

k-U

ibi

Flo

Fix

Adaptability

rm Pe

ent

Pro

路 the design attributes matrix rates each system on how well it would be able to satisfy the project goals

DESIGN ATTRIBUTES MATRIX (1-10, Worst-Best)

Totals

路 the cost matrix compares first-glance cost in each of six categories as compared to conventional construction

floodproof design research: NEW CONSTRUCTION floodproof design analysis matrices 路 the cost factors matrix identifies the factors which might contribute to a higher cost in each area

ble

rta

k-U

Jac

ibi

mp h

Fix

loo d

ent

Special Requirements

Systems

Materials/Finishes

Super Structure

Foundation

COST FACTORS MATRIX

Pe rm

Pro

floodproof design research: existing buildings floodproofing study + standards recommended methods for existing buildings: The purpose of dry floodproofing a building is to make it watertight to floods of limited duration (a few hours) and depth (typically less than 3 feet). Dry floodproofing reduces the potential for flood damage by reducing the probability that the building interior will be inundated. It can be an appropriate alternative for flood mitigation when relocating or elevating buildings is not cost-effective or technically feasible.

LOWER PORTION OF WINDOW PERMANENTLY CLOSED WITH MASONRY

VULNERABLE EQUIPMENT SUSPENDED OR RAISED ABOVE FLOOD LEVEL

SUMP PUMP

The minimum performance requirement for dry floodproofing measures is a space that is protected by walls that are substantially impermeable and resistant to flood loads. A substantially impermeable wall should limit water accumulation to a maximum accumulation of 4 inches in a 24-hour period with a sump pump to control seepage (USACE 1995). However, the minimum performance requirement can be exceeded with proper planning, design, and materials. Incorporating flood damage-resistant materials into the dry floodproofing design up to the height of the dry floodproofing measure is recommended. Additionally, building systems such as walls and foundations may need to be strengthened to withstand direct flood forces and the loads imposed by floodproofing measures (e.g., shields, watertight doors), which are used to temporarily seal openings. An effective dry floodproofing retrofit requires the following: • • • • • • • • •

WATERPROOF COATING ON WALLS

REMOVABLE FLOOD SHIELD ACROSS SERVICE BAY PROPERLY ANCHORED UNDERGROUND FUEL TANK BACKFLOW VALVE ON SANITARY SEWER LINE FOUNDATION

UNDERPINNED TO Detailed site evaluation RESIST FLOTATION Detailed building evaluation Careful evaluation of all of the dry floodproofing measures, including a consideration of residual risk Design by a qualified registered design professional Verification/testing that the constructed systems provide the desired floodproofing effectiveness Floodproofing Certificate for Non-Residential Structures for the dry floodproofing design A plan for deploying any active dry floodproofing measures that require human intervention Sufficient warning time to deploy active dry floodproofing measures and vacate the building Operations and maintenance plan

floodproof design research: existing buildings floodproofing study + standards recommended methods for existing buildings: Sealants and shields are methods that can be used to protect a structure from low-level flooding. Minifloodwalls (low level) can be used as an alternative to shields for protection of windows, window wells, or basement doors. These systems are easily installed and can be inexpensive in relation to other measures such as elevation or relocation. However, by sealing (closing) a structure against flood inundation, the owner must realize that, in most cases, the typical building will not be capable of resisting the loads generated by more than a few feet of water. The level of flooding the building can resist should be determined by a competent design professional. There will be a point beyond which the sealants and shields will do more harm than good and the owner must allow the building to flood to prevent structural failure from unequalized forces. The USACE National Flood Proofing Committee has investigated the effect of various depths of water on masonry walls, discussed in their report titled Floodproofing Test (USACE, 1988). The results of their work show that, as a general rule, a maximum of 3 feet of water should be allowed on a non-reinforced concrete block wall that has not previously been designed and constructed to withstand flood loads. Therefore, application of sealants and shields should involve a determination of the structural soundness of a building, the walls, and the floor slab, as well as their corresponding ability to resist flood and flood-related loads. For additional information on dry floodproofing, refer to FEMAâ&#x20AC;&#x2122;s NFIP Technical Bulletin 3-93, Non-Residential Floodproofingâ&#x20AC;&#x201D; Requirements and Certification for Buildings Located in Special Flood Hazard Areas in Accordance with the National Flood Insurance Program (FEMA, 1993).

DRY FLOODPROOFING

Figure 5D-2. A way to seal an existing brick-faced wall is to add an additional layer of brick with a seal in between. Please note that weep holes and wick drains work both ways to allow for moisture passage from high to low pressure. Weepholes and flashing should be located above the DFE, and the veneer below the DFE should be fully grouted.

Sealants include compounds that are applied directly to the surface of the structure to seal exterior walls and floors (see Figure 5D-2), or a wrap that is anchored to the exterior wall or foundation at or below the ground and attached to the wall above grade during flooding (see Figure 5D-3). The owner may need to strengthen the existing building to aid in resisting the very large flood-induced loads. Because of the large hydrostatic

floodproof design research: existing buildings floodproofing study + standards recommended resources for floodproofing non-residential buildings: Flood hazard mitigation can be achieved in several ways and is often different for buildings that are used for non-residential purposes such as business or industry, as compared to residential buildings such as homes and apartments. To that end, in 1986, the Federal Emergency Management Agency (FEMA) published FEMA 102, Floodproofing for Non-Residential Structures (FEMA 1986). The publication provided guidance to local officials, building owners, designers, contractors and other individuals or organizations interested in the design and implementation of floodproofing retrofits in non-residential structures. The guidance in FEMA 102 covers a broad range of floodproofing techniques that can be used in new and existing nonresidential buildings to reduce or eliminate the potential for damage from flooding. FEMA 102 is currently one of only a few documents in the FEMA Library that provides design professionals and community officials with guidance on floodproofing non-residential buildings. However, since its publication in 1986, floodproofing techniques and technology have evolved such that updated guidance on the subject is needed. This document, FEMA P-936, Floodproofing Non-Residential Buildings, provides current guidance on floodproofing retrofits for nonresidential buildings. It is similar to FEMA 102 but has a slightly different objective, which is described as follows: The primary objective of this publication is to provide guidance on floodproofing existing non-residential buildings in riverine areas and coastal areas that are not subject to wave action. Floodproofing will be most successful in areas subject to relatively shallow flood depths.

Floodproofing Non-Residential Buildings FEMA P-936 / July 2013

floodproof design research: existing buildings alternative concepts for consideration - option # 1 - flood wall option one: ‘flood wall’ concept The ‘Flood Wall’ concept pursues a different approach, by choosing to floodproof the ‘site’ in lieu of applying floodproofing directly to the building walls. Typically flood walls would be placed a greater distance from the structure or structures being protected, however in this case, these ‘flood walls’ will be within 2’-5’ of the exterior walls and require some specific engineering in order to maximize flood protection and minimize the impact to the existing structure and site components. Floodwalls, which are typically constructed of reinforced concrete or masonry, provide a barrier against inundation, protect structures from hydrostatic and hydrodynamic loads, and may deflect flood-borne debris and ice away from the building. Cantilever floodwalls are the most common type of floodwall because they are economical to design and construct. They use cantilever action to retain the mass behind the wall. Cantilever floodwalls are usually constructed of reinforced concrete or concrete block with steel reinforcing bars embedded in the concrete core of the wall (see Figure below). Stability is achieved partially from the weight of the soil on the heel portion of the base and from the weight of the wall itself balanced by the lateral forces and overturning moments (see Figure 4-4). The footing is often constructed with a “key” to increase sliding resistance (see Figure 4-3). Because a cantilever floodwall often also serves as a cantilever retaining wall, the floodwall must be designed to resist the load combinations in ASCE 7 or the loads in other accepted engineering standards. The design should take into account buoyancy effects that reduce the submerged weight of the floodwall and the reduced bearing capacity of the soils that support the wall. Backfill may be placed along the side of the wall exposed to flooding to keep water away from the wall during flooding conditions. Similar to the gravity floodwall, as the flood elevation increases and the required materials and cost of the cantilevered floodwall increase, the more cost-effective the alternative types of floodwalls may become.

Below: Examples of cantilevered flood walls

Above: Floodwall in action

floodproof design research: existing buildings alternative concepts for consideration - option # 2 - sheet piling option two: ‘sheet piling’ concept The ‘Sheet Piling’ concept takes the flood proofing technologies and materials used in levees, marinas, and other flood proof site work and applies these to a building. Using a continuous sheet pile wall(or alternative wall construction) around the exterior of the building from all the way below the foundation to the height of the Design Flood Elevation (wether it be 8.6’ or 10.6’), would solve several key issues of floodproofing with one method of intervention. These sheet piles could be installed to penetrate a specific distance below grade in order to create a dam against water infiltration AND continue above grade to meet the desired DFE. Any openings below the DFE would then receive opening protectives that would be designed to be integrated in the sheet piling wall and installed upon the arrival of a pending flood event. This wall would also provide the Owner with the desired wave action and debris impact protection. By applying this concept to the entire perimeter of the building, the Owner would have the opportunity to improve the overall aesthetic of his building in a uniform manner that addresses the need for floodproofing. This concept approach would need further research, structural and architectural engineering, as well as a cost study in order to prove its structural and economic viability but VIA believes that there is great potential for this concept.

Left: Example of applying exterior wall component (wood shades) to existing building for aesthetic + functionality improvement.

Below: Sample photograph of composite sheet piling available.

Right: Sheet piling retaining wall