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HomeMy WebLinkAboutSoil Report Allterra 12.15.20203866 PROSPECT AVENUE • SUITE 9 - WEST PALM BEACH, FLORIDA 33404 • (561) 881-1939 14 December 2020 Phoenix Custom Homes 1760 Jog Road, Suite 120 West Palm Beach, FL 33411 Subject: Report of Geotechnical Services - 3-Level Custom Home 4848 Watersong Way, St. Lucie County, Florida Allterra Engineering & Testing respectfully submits this report of geotechnical services for the subject project. Allterra's services have been performed to meet certain requirements of chapter 18 of the 2017 Florida Building Code, its subsequent revisions, and local amendments. This report is Allterra's instrument -of -service provided for sole reliance and use by Phoenix Custom Homes. Third parties may read this report for information purposes. Project and Scope Reference Documents. Digital copies of certain progress -set drawings dated 11-12-20 by Team Architecture were provided for Allterra's reference in performing its services. Protect Information. The project is a 3-level custom home proposed for construction upon the subject property. The property is bounded on the west by Watersong Way, on the east by the Atlantic Ocean, and on the north and south by other residential properties. The project is designed for supported upon a foundation of grade beams and piles. According to elevations presented on drawing A2.1 surface -grade elevation is +8.0 feet NAVD and bottom of 2nd-level beam is +17.33 feet. Scope and Constraints. Allterra was tasked with performing soil -test borings to characterize subsurface conditions and providing recommendations for foundation design (pile length, diameter, and capacity). Specific information on design storm parameters has not been provided at this time. These parameters are provided by the project coastal engineer and typically include information such as breaking wave -crest elevations, eroded -grad elevation, wave impact force and elevation of force resultant, debris impact force and elevation of force resultant, etc. For purposes of this report, Allterra assumed: head -of -pile at 9 feet above existing surface grade and fixed against rotation, and eroded grade at 6 feet below existing surface grade. If these assumptions are erroneous, the conclusions and recommendations of this report may warrant change. Field Work Allterra mobilized personnel and equipment to the project site on 19 December 2020 to perform two soil -test borings as represented on the Boring Location Plan of this report. Penetration testing was performed in the soil -test borings by driving a 2-inch diameter steel sampler with blows of a 140- pound hammer free -falling 30 inches. Copies of the boring logs are attached to this report for the reader's reference. Geotechnical Services — 3-Level Custom Home 1 4848 Watersong Way, St. Lucie County, FL 14 December 2020 20-470 BORING LOCATION PLAN SEAGRAPE \ \ O y �\ \ \ \\ \ a \\\ FIND NAIL do DISK �y0 OCCUPIED 4F7E = 7.0' g\ a \ \ LS / 4971 \ �CP �� e PALM EE�3\ q 6.0' N FND 5/ ' It \ B-1 LB r�28� \ N 11119712(\_�� ^ E 896209.55 \ \ \ 41 \ PLA i \ C'�'Y� " �^q dd B-2 �d 0 6.0' 0 LOT 44 VACANT :r� ,,p2 65'g� \ LAB D54288 RC Z \ ' \ pad N 1111973.20 E 896209.5555 \ 6 / � / LOT 45 / Findings Subsurface Profile. Allterra's borings encountered variable subsurface conditions at each boring location. The conceptual subsurface profile (based on B-2) can be described as: • Topsoil sampled as ray, fine sand with occasional roots from surface grade to approximately 6 inches below grade, underlain by • Stratum 1 a - firm, brown and tan, fine sand with trace of shell to approximately 3 feet below grade, underlain by • Stratum 1 b — very -firm to firm, dark -gray, medium -to -fine sand with occasion trace of shell to approximately 8 feet below grade, underlain by • Stratum 2 — firm, dark -brown, peat to approximately 13 feet below grade, underlain by • Stratum 3 -- dense, gray, medium -to -fine sand with trace of shell to approximately 35 feet below grade, underlain by • Stratum 4 — very -firm, gray, fine sand to 50 feet below grade. Strata 1 a, 1 b, 2 and 3 were encountered in B-1 before refusal at 17 feet below grade. Refusal to Allterra's drilling method may occur when bedrock, cap rock, subsurface boulders, subsurface corals, or other buried impenetrable material is encountered. Groundwater. Groundwater was encountered at depths of approximately 12 feet below surface grade at the time of Allterra's borings. The depth to groundwater may vary at other times due to changes in hydrologic conditions. Conclusions Pile Capacity. Considering the conceptual subsurface profile and assumption of eroded grade, Allterra estimated the following capacities for 14-inch and 16-inch-diameter auger -cast piles installed to approximately 25 feet below surface grade (approximately 20 feet below eroded grade). Geotechnical Services — 3-Level Custom Home 2 4848 Watersong Way, St. Lucie County, FL 14 December 2020 20-470 IeDaetirC;, Gx�eCv.Ef?>Lp _ CH�zQNTA� :Ift�ess�ae 14 inches 144 Kips 60 Kips 30 Kips 85 Kips 16 inches 174 Kips 70 Kips 36 Kips 114 Kips Notes: CAxinL = ultimate compressive load capacity. CVERTIcAL = allowable compressive load capacity. CHORIZONTAL = allowable horizontal at -eroded -grade shear -load capacity (%2-inch displacement). Uplift Resistance = (weight of pile + skin friction)/1.5. Kips = 1000 pounds. Pile Evaluation. The pile modeling was based on a conceptual subsurface profile and certain assumptions about the design storm event. The client shall engage a Florida -licensed professional engineer experienced in coastal engineering to review the information and assumptions presented in this report against his expert evaluation. Without the coastal engineer's agreement, additional evaluation may be required. Recommendations — Building -Pad Preparation The building pad is defined as the footprint of construction plus 5 feet in all accessible directions. Allterra recommends: 1. Strip topsoil and vegetation (including roots) from building pad and properly waste. 2. Thoroughly wet the exposed surface and allow it to drain to optimum moisture. 3. Mechanically compact exposed surface to at -least 95 percent of maximum -dry -density as determined by the Modified -Proctor compaction test (ASTM D-1557 / AASHTO T-180). 4. Engage Allterra to perform probe -rod and field -density tests to verify compaction standards are achieved. 5. Place fill, where needed, to achieve construction -ready grades in thin lifts and compact (at or near optimum moisture) to at -least 95 percent of maximum -dry -density as determined by the Modified -Proctor compaction test (ASTM D-1557 / AASHTO T-180). Lift thickness will depend upon methods and equipment employed to achieve the target densities. 6. Engage Allterra to perform probe -rod and field -density tests on each 2-foot rise in fill height to verify compaction standards are achieved. 7. Once the building pad is prepared, the contractor shall maintain its condition to prevent erosion or other degradation through the placement of subsequent work. Recommendation — Auger -Cast Piles Pile Materials. Piles shall be formed with minimum 4000 PSI grout placed under pressure as the auger is progressively withdrawn from the borehole. Piles shall be reinforced with five full -depth number-5 steel bars and number-3 ties spaced not more than 16 inches on -center. The structural engineer shall determine the number and distribution of piles considering structural loads and geometry. Piles shall be drilled 8 feet into rock or refusal (less than 1 foot/minute advance). Pile Layout. The number and distribution of piles shall be determined by the structural engineer considering project loads and geometry. Piles shall be spaced at -least 3 diameters center -to -center to avoid group effect on stress distribution in the bearing stratum. Pile -Installation Monitoring. Engage Allterra to monitor installation of piles. For auger -cast piles, monitoring shall include: 1. Check pile layout for conformance to design foundation plan. Geotechnical Services — 3-Level Custom Home 3 4848 Watersong Way, St. Lucie County, FL 14 December 2020 20-470 2. Observe field trial and calculate gout -pump factor. 3. Observe drilling of pile to verify target depths are achieved. 4. Observe grouting of pile bore to verify acceptable grout return. 5. Sample grout for compressive -strength testing. 6. Observe installation of reinforcing steel to verify full -depth penetration. 7. Test grout specimens to verify design compressive strength is achieved. 8. Calculate grout factors and summarize installation data for each pile. 9. Prepare report of work acceptance signed and sealed by Professional Engineer. Qualification Allterra has based its conclusions and recommendations upon certain client -provided information and interpretation of data obtained at discrete points within the limits of exploration. It is possible that conditions may vary between boring locations or beyond the limits of the boring array. Project designs may also change. If additional information about the project or site is discovered that does not appear to conform to the conditions presented in this report, Allterra reserves the right to review the new information and modify its conclusions and/or recommendations where warranted. Closing Thank you for engaging Allterra as your geotechnical consultant. Please call the undersigned if you have questions about this report or need other services. Yours truly, Allterra Engineering & Testing Cer is to gf Authorization 9139 t en ell R d ers, E Principal Engineer FL Lic. No. 55960 Attachments Geotechnical Services — 3-Level Custom Home 4 4848 Watersong Way, St. Lucie County, FL 14 December 2020 20-470 3866 PROSPECT AVENUE • SUITE 9 • WEST PALM BEACH, FLORIDA 33404 • (561) 881-1939 PROJECT Watersong P U D Plat No 1 -LOT #43 - 4848 WATERSONG WAY -PARCEL ID 2532-500-0057-000-9_- St. Lucie LOCATION B-1 (Approximate) BORING NO. 1 County, FI DDnpncPn T1A/(1-ST0RV ra IGTCIM RFgInFNCF DEPTH DESCRIPTION OF MATERIAL Sample No Blows Per Foot DEPTH 1 0"-6" Grey Fine Sand, trace of roots (topsoil) 6"-3' Brown and Tan Fine Sand, trace of shell 3'-4' Dark Grey Medium -to -Fine Sand 4'-5' Dark Grey Fine Sand, slight trace of organics 5'-8' Dark Grey Medium -to -Fine Sand, trace of shell (fragmented) 8'-13.5' Peat 13.6-15' Grey Fine Sand, some rock, trace of shell (fragmented) 17- Impenetrable (rock) 6-10 1 2 10-13 2 3 12-12 3 4 13-12 4 5 12-1 5 6 12-122 6 7 12-10 7 8 10-6 8 9 5-5 9 10 5-5 10 11 3-4 11 12 3-4 12 13 4-7 13 14 7-14 14 15 15-18 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31 32 32 33 33 34 34 35 35 36 36 37 37 38 38 39 39 40 40 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 50 CLIENT Phoenix Custom Homes J O B NO. 20-470 DRILLER TM/MS/TKM WATER TABLE 12' DATE 12/9/20 TEST DATA In general accordance with ASTM D-1586 These Soil Boring Tests are Representative of and Apply to the Exact Location and Depth of the Boring. AUTHORIZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL. 3866 PROSPECT AVENUE SUITE 9 • WEST PALM BEACH, FLORIDA 33404 • (561) 881-1939 PROJECT Watersong P.U.D. Plat No 1 -LOT #43 - 4848 WATERSONG WAY -PARCEL ID 2532-500-0057-000-9 -St. Lucie LOCATION B-2 (Approximate) BORING NO. 2 County, FI PROPOSED TWO-STORY CUSTOM RESIDENCE CLIENT Phoenix Custom Homes J O B NO. 20-470 DRILLER TM/MS/TKM WATER TABLE 12' DATE 12/9/20 TEST DATA In general accordance with ASTM D-1586 These Soil Boring Tests are Representative of and Apply to the Exact Location and Depth of the Boring. AUTHORIZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL.