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HomeMy WebLinkAbout2006 07 10 Regular 302 Jesup's Landing COMMISSION AGENDA ITEM 302 CONSENT INFORMATIONAL PUBLIC HEARING REGULAR X July 10, 2006 Meeting MGR ~EPT /y Authorization REQUEST: Public Works Department requesting the City Commission review and consider a proposed modification to the Jesup's Landing final engineering, specifically to the foundation design at four townhome buildings PURPOSE: The purpose of this agenda item is to request the City Commission's review and consideration for a proposed modification to the Jesup's Landing final engineering, specifically to the foundation design at four townhome buildings. APPLICABLE REGULATIONS: Section 166.021, Florida Statutes. Chapter 9, Land Development. Town Center District Code. Binding Development Agreement. CONSIDERA TIONS: . Jesup's Landing is a planned 185-unit townhome site located on 17.15 acres in the Town Center on the south side of Orange Avenue. The project is currently under construction. . The final engineering plans for Jesup's Landing were originally approved with conditions by the City Commission at the June 27,2005 Commission meeting. Several minor modifications were approved by the Commission at the October 10, 2005 meeting. . The geotechnical evaluation for the original site design, performed by Universal Engineering Sciences, indicated the presence of buried organic muck material within the eastern portion ofthe site. Based on this evaluation, Universal designed a surcharging plan to pre-consolidate the deeper muck deposits at six (6) building footprints. The approved surcharging plan consists of installing 12-foot high surcharge mounds at the six 071006_ COMM _Regular _302 jesups Landing Geotechnical Engineering Modification Regular Agenda Item 302 July 10, 2006 Page 2 footprints for a minimum of six (6) months. Under this plan, the surcharge mounds would be monitored and removed after confirmation that the compressible soils have consolidated or settled to at least 90 percent under the surcharge load. The surcharging plan as originally designed was approved by the Commission as a part of the Final Engineering at the June 27,2005 meeting. Please refer to Exhibit 1 for a drawing of the surcharging plan. . Levitt & Sons recently had Universal perform additional geotechnical exploration to further evaluate the extent of the muck and to provide additional recommendations to support the affected buildings. Due to the depth and thickness of the buried muck and the potential for artesian pressures, removal of the muck or using pile foundations are not viable options. Universal provided three options for the building foundations for the four buildings located over the deep buried muck: 1. Surcharging with structural slab design (as described above) 2. Use ofgeofoam in conjunction with structural slab design (see below) 3. Helical pier system Levitt & Sons has proposed to use geofoam in conjunction with structural slab design, as described in detail below. PROPOSED SURCHARGING AL TERNA TIVE - GEOFOAM: . Levitt and Universal have proposed an alternative to surcharging by using "geofoam" in conjunction with the structural slab design. Geofoam is lightweight, thermally-fused, expanded polystyrene (EPS) material that weighs only 1.0 to 2.0 pounds per cubic foot, which is approximately 1 % of the density of soil. . Universal's proposed plan generally consists of installing geofoam at depths between 3 and 9 feet below the floor slabs at four buildings. The lightweight geofoam displaces the heavier existing soils beneath the floor slabs. The net result is that when the buildings are constructed, the deep compressible muck deposits should not experience any additional structural loading, since the reduction in weight from the geofoam offsets the additional weight of the buildings. Please refer to Exhibit 2 for a drawing of the geofoam plan. . Based on the results of Universal's additional geotechnical investigation and analysis, only four of the six buildings originally designated for surcharging are still recommended for surcharging or an alternative building foundation, such as geofoam. . Exhibit 3 is a letter dated June 13, 2006 from Universal providing their recommendations and installation guidelines for the geofoam option. Exhibit 4 is an article from STRUCTURE magazine that provides some background information about geofoam and its functional applications. 071006_COMM_Regular_302_Jesups Landing Geotechnical Engineering Modification Regular Agenda Item 302 July 10, 2006 Page 3 FINDINGS: . Universal Engineering Sciences, a reputable Florida-based geotechnical engineering firm, has prepared a complete design for the proposed geofoam based on a thorough geotechnical evaluation. . Geofoam is used extensively as lightweight fill in various engineering applications, such as bridges, highway embankments, and building foundations. . The building structural engineer has approved the use of geofoam in the foundations as described in Universal's report. . Geofoam is not a standard construction material on townhome building foundations in Central Florida, and it has not been utilized on any City projects that Staff knows of STAFF RECOMMENDATION: Staff recommends the following conditions be required if geofoam is utilized: . Mandatory notification of all potential buyers of townhome units supported by geofoam. . Levitt's structural warranty for the affected townhome units shall be increased from 10 to 20 years ATTACHMENTS: 1. Exhibit 1 - Surcharging Plan 2. Exhibit 2 - Geofoam Plan 3. Exhibit 3 - Letter from Universal Engineering Sciences dated June 10, 2006 4. Exhibit 4 - Article "Lighten Your Load" from STRUCTURE magazine, March 2004 COMMISSION ACTION: 071006_COMM_Regular_302_Jesups Landing Geotechnical Engineering Modification UNIVERSAL ENGINEERING SCIENCES PAGE NO: B-4 ADDITIONAL GEOTECHNICAL EXPLORATION JESUPS LANDING TOWNHOMES WINTER SPRINGS, SEMINOLE COUNTY, FLORIDA EXHIBIT 2 TOWNHOME RESIDENCES CLEAN SAND BACKFILL, COMPACT TO MIN. 95% OF THE MODIFIED PROCTOR MAXIMUM DRY DENSITY (ASTM D 1557) CLEAN SAND BACKFILL, COMPACT TO MIN. 92% OF THE MODIFIED PROCTOR MAXIMUM DRY DENSITY (ASTM D 1557) PLACE AT LEAST 4-FEET OF TEMPORARY FILL IF DEWATERING IS STOPPED FOR A LONG DURATION PRIOR TO POURING CONCRETE REINFORCED WAFFlE OR POST-TENSION SlAB, TYP. TENSAR BX-1200 OR HUEJKAR FORNIT 30 BIAXIAL GEOGRID MlRAFI160N FILTER FABRIC, TIP. B-5 UNIVERSAL ENGINEERING SCIENCES Consultants in: Geotechnical Engineering. Environmental Sciences Construction Materials Testing. Threshold Inspection Private Provider Inspection Exhibit 3 June 13, 2006 OFFICES IN: . Clermont . Daytona Beach . DeBary . Fort Myers . Gainesville . Hollywood . Jacksonville . Ocala . Orlando . Palm Coast . Rockledge . Sarasota . SI. Augustine . Tampa . West Palm Beach Levitt & Sons, Inc. 4037 Avalon Park East Boulevard Orlando, Florida 32828 Attention: Mr. David Schmitt Reference: Geofoam Foundation Support Option Jesup's Landing Townhomes Winter Springs, Seminole County, Florida UES Project No. 01-0012843-014-02 UES Report No. 485306 Dear Mr. Schmitt: It is our understanding that Levitt & Sons has decided to select the Geofoam option for supporting a total of four town home buildings based on our recommendations outlined in our previous report (No. 459108). Due to the depth and thickness of buried organic soils and the potential for artesian pressures, demucking or removal of the organic soils as well as pile foundation is not a viable option. While surcharging is an option, there is considerable uncertainty in the duration of surcharge due to variable thickness of the muck. In light of our recent meeting with officials from City of Winter Springs, the following paragraph describe and clarifies the geofoam option for support of the four town home buildings. LIGHT WEIGHT FILL USING GEOFOAM (COMPENSATING FILL) Geofoam falls in the category of light weight fill materials, which are typically used to reduce stresses on soft compressible soils such as organic peat (muck) or very soft compressible clays. Geofoam is composed of light weight, thermally-fused, expanded polystyrene (EPS) beads and weighs only 1.0 to 2.0 pounds per cubic feet, approximately 1 % of the density of soil that it replaces. Geofoams are generally inert and when installed properly do not degrade over time under normal soil and groundwater conditions. Construction is relatively 0 fast and less labor intensive, which in particularly beneficial with compressed project time lines. Light weight fill material such as Elasticell and geofoams have been used widely over the past 30 years as a compensating fill and to reduce foundation loads over compressible soils mostly in the DOT projects, bridge abutments, large embankment over soft soils, retaining walls etc.. Its use in residential building foundation applications, although less frequent, has been successful as well. Page 1 of 4 Pages - 3532 Maggie Blvd. · Orlando, FI 32811 · (407) 423-0504 · Fax (407) 423-3106 Geofoam Foundation Support Option Jesup's Landing Townhomes Winter Springs, Seminole County, Florida UES Project No. 01-0012843-014-02 UES Report No. 485306 For this project, ee recommend that geofoams be installed at depths between 3 feet and 9 feet below the bottom elevation of the proposed floor slab. For this applications, the geofoams are intended to act as a compensating fill, where the combined weight of the building, fill material and the geofoam will be less than the weight of the 6-foot of soils that will be excavated between 3 and 9 feet. Therefore, no additional net weight is added on to the organic soils and the current state of equilibrium is maintained as far as the organic muck deposits are concerned. A minimum buffer of 3 feet of good quality fill is recommended to provide sufficient weight and anchor the geofoam block against buoyant hydrostatic pressures as well as to install utility lines and plumbing. Details about the fill material Geofoam area and constructional details about Geofoam are presented in Appendix C. Calculations supporting the geofoam option are also presented in Appendix C. RECOMMENDED INSTAllATION GUIDELINES FOR GEOFOAM OPTION The following should be considered general guidelines for installation of the geofoam blocks and site preparation for construction of the building. Other installation specifications outlined by the manufacturer must also be followed as necessary. · Perform test pits to evaluate the depth to the groundwater table · Perform remedial dewatering using either well points or rim ditch with sump pumps along the perimeter of the building footprint. The groundwater table should be maintained at least 2 feet below the bottom of the excavation for the geofoam. In the event dewatering is halted for a long duration (more than 2 weeks), place at least 4 feet of temporary fill above the geo-foam to prevent uplift. . Perform excavation to a depth of about 7 to 8 feet below existing grade corresponding to 9 feet below the lowest building floor slab bottom elevation, and extending at least 5 feet laterally beyond the building footprint limit. The slopes of the excavation must conform to OSHA standards and be maintained stable. · Install a layer of biaxial geogrid (Tensar BX 1200, Hueskar Fornit 30 or equivalent) prior to placing the geofoam blocks. The layer of biaxial geogrid should be installed over the entire excavated footprint. A second layer of geogrid is also recommended on top of the geofoam. · Compact the bottom subgrade soils to achieve at least 92 percent of the Modified proctor maximum dry density to a depth of 2 feet. If necessary place a layer of 6 inches of crushed concrete to ensure a uniform stable subgrade. Page 2 of 4 Pages ~ /// / // Geofoam Foundation Support Option Jesup's Landing Townhomes Winter Springs, Seminole County, Florida UES Project No. 01-0012843-014-02 UES Report No. 485306 . Place the geofoam blocks in a staggered brick fashion as indicated in Appendix C from the bottom-up to at least 3-feet below the slab bottom elevation. . We recommend EPS Geofoam EPS29 or equivalent beneath the building footprint. It is acceptable to use the geofoam billets 3' x 4' x 8' for this project as long as the blocks extend at least 3 feet beyond the structural slab perimeter edge. . The 3'x4'x8' geofoam billets or blocks should be installed in two layers with a BX 1200 geogrid (or Hueskar Fornit 30) geogrid at the bottom and top of the Geofoam blocks. . The geofoam blocks will be held in place laterally with gripper plates to reduce lateral slippage during construction. Additionally, vertical post (such as 4 foot long, #5rebars or wooden stakes at 4-foot centers) hammered into the ground, along the perimeter of geofoam blocks may be installed to prevent lateral movement during installation . A filter fabric (Mirafi 160N or equivalent) should be provided immediately above the geofoam block to prevent downward soil migration. This layer should be between the geogrid and the geofoam block. . A minimum of 3 feet of compacted fill buffer will be provided between the bottom of the floor slab and the top of the geofoam blocks. The fill material between the slab and top of the geofoam must be placed in thin lifts and carefully compacted to at least 95 percent Modified Proctor maximum dry density using light equipment (plate compactor). . The backfill on either side of the geofoam blocks must also be placed concurrently in thin lifts and each lift must be compacted with light equipment (plate compactor) to at least a 92 percent Modified maximum dry density. Adequate care must be taken to ensure that the geofoam blocks are not damaged during this process. . The affected buildings must be supported on a well reinforced structural waffle slab foundation system with sufficient top and bottom steel that reduces the adverse effects of differential movement. . The uppermost layer of geogrid (Tensar BX 1200, Hueskar Fornit 30 or equivalent)should extend laterally at least 5 feet beyond the geofoam block footprint limits to provide resistence to any inadvertent uplift pressures. . The excavation of the building footprints, compaction of the subgrade soils, installation of the geofoam blocks and the backfill operations must be conducted under the full time observation-of a UES engineer or his representative. Page 3 of 4 Pages / Geofoam Foundation Support Option Jesup's Landing Townhomes Winter Springs, Seminole County, Florida UES Project No. 01-0012843-014-02 UES Report No. 485306 . Finally, please note that for added degree of insurance and schedule permitting, the client may chose to placed additional fill (surcharge) above the finished floor elevation for a duration of 2 months after installation of the geofoam blocks and prior to construction of the building. We hope this letter report addresses your concerns. We appreciate the opportunity to have worked with you on this project and look forward to a continued association. Please do not hesitate to contact us if you have any questions, or if we may further assist you as your plans proceed. SSRlRKD:as Client (6) Enclosures: Appendix A.,.1 : Appendix B-1: Appendix B-2: Appendix B-3: Appendix C-1 : Appendix C-2: Appendix C-3: Appendix C-4: Appendix C-5 Appendix C-6 Respectfully submitted, UNIVERSAL ENGINEERING SCIENCES, INC. cert~cale Of,~u~~riza. 1;0" No. 549 j~ Shrian8r S. RaQ, MS. P.E. Vice Pr 'dent-Engineering Services .... -- ~ erick. M.S., P.E. ----.- Senior Vice-President Profession En ineer No. 37711 Date: /. ' , Site Location Map Site Location Plan Boring Logs Soil Classification Chart Lithologic Cross-Section (designated as Section A-A', B-B' and C-C'). Isometric View of Boring Profiles Geofoam Plan Typical GeoFoam Installation Cross-Section Compensating Fill Calculations using Geofoam Surcharge Plan Page 4 of 4 Pages Ii'~. ',':- t Graphic 2: EPS-geofoam blocks were used in a cramped urban site for a pile-supported hotel in Honolulu, HI fcredit: Pacific: Allied Products, Ltd.]. . Use as backfill or fill behind basement and retaining walls - This drastically reduces the lateral 'earth' pressures acting on the walls as well as the vertical stresses on the adjacent ground (an important consideration for soft-ground sites when settlements are a design issue); . As backfill and fill over the roof slabs of below-ground structures (parking garages, etc.) or elevated exterior slabs - This significantly reduces the loads for which these slabs must be designed; . As backfill or fill under shallow foundations (footings, mats, slabs-on- grade) supporting lightly loaded buildings and even small bridges - On sites where the underlying soils are soft and compressible, it is possible to design a compensated or 'floating' foundation for a structure by replacing soil with EPS-geofoam blocks and constructing the foundation directly on or above the geofoam layer. Engineers continue to find new applications for geofoams as lighrvveight fill. In recent years, rhe use of EPS blocks has migrated inside eXlstll1g structures and been used to fill basements for various purposes and create 'stadium' seating for movie theaters. Compressible-I nclusion Functional Applications One of the newer functional applicarions ofEPS geofoam is compressible inclusion. This is the economical use of only a relatively thin (of the order of 6 inches (150 mm)) layer of crushable geofoam material between a structure and the adjacent ground. Conceptually, compressible-inclusion applications can be visualized as the way in which a foam egg carton cushions and protects eggs. There are two primary ways in which the use of geofoam compressible inclusions has proven useful and cost effective in practice: · Beneath structural slabs underlain by potentially expansive soils and rock - Although cardboard 'void formers' have been used in such applications, the use of EPS-geofoam products has become the preferred alternative in recent years because EPS is unaffected by wet ground or weather and will not decompose after construction (which can create a methane- gas explosion hazard as was experienced on at least one project in the U.K.); Gmphic 3: Below-ground parking structure il1 Chicago, IL being backfilled with EPS-geoioam blacks 011 its roof slab /Credit: AF1VI]. Upd.lJt~ rx~11 Newly updated for ACI 318.02, penWall \13..0 is a powerful, finite element. software proouctivlly tool designed to help you accurately design and analyze reinforced concrete walls. The completely redesigned interface enables you to edsily model complex waHs that can include stiffeners and openings. pcaWallls so easy to learn and simple to use that you'll be able to stari saving time and money almos! irnrnediately. And when you use pcaWall, you're also taking advantage of the Portland Cement Association's more than 85 years of experience, and technical support in concrete design and construction. $0 you know you'll be able 10 trust every resull, every time. Visit to download your evnluation copy of the new pcaWa!l '13.0. Network Licenses now available. Please call 847.972.9042 for more klfomwtion. ...................1 pcaStructure Point Concrete Software Solutions STRUCTURE magaz.ine . March 2004 Graphic: 4: EPS-geofoam blocks both spread-fiJoting foundation Iwd retaining wall Jill for a low-rise commercial buiUing in CbiCllgo, lL /credit, PofyjollJn Pa('kel~<J. Graphic 6: Placing an EPS-geofoam compressible inclusion (void former) on a building project in Winnipeg, Manitoba, Canada {credit: PFF Corporation Plasti- fab Division} Graphic 5: Filling with blocks of EPS geofomn inside an existing building basement in Chicago, IL. [credit: Polyfoam Packers]. Graphic. 7: Use of a multifunctional geofoam compressible inclusion for a deep building basement in Kansas City, MO [credit: Geo Tech Systems Corporation.] STRUCTURE magazine · March 2004 Graphic 8: Close-up of tbe geofoam product providing the functions of compressible inclusion, groundwater drainage, and thermal insulation in Kansas City [credit: GeoTech Systems Corporation]. . Behind basement and retaining walls - This is a lower-cost alternative to using EPS blocks as a lightweight fill as described above ,and is useful on projects where only a modest reduction in lateral earth pressures is desired or cost effective. In such applications the geofoam product is usually designed to be multifunctional, and provide drainage and thermal insulation in addition to serving as a compressible inclusion. Getting Started with Geofoams Additional information about geofoams can be found at the Manhattan College Center for Geotechnology (CGT') website at www.engineering.manhattan. edu/civillCGT.html. One of the goals of the CGT is to foster greater interaction between structural and georechnical engineers in practice. 10 that end, the CGT maintains a special webpage to keep structural engineers apprised of new developments in georechnical engineering. This page can be accessed directly at www.engineering.manhattan. edul civil/CGT IT2structural.html. Please pay us a visit and lighten up!.