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1739 GEOTECH jan 9 2012a,,--..._s RICHARD SKINNER & ASSOCIATES, ARCHITECTS 2245 St. Johns Avenue Jacksonville, Florida 32204 Attn: Ms. Maiju Stansel Re: Report of Geotechn ical Exploration & Engineering Evaluation Proposed Garage Addition -Clements Residence 1739 Beach Avenue -Atlantic Beach, Florida AGES Job No. J15240, Report No. 001 Dear Mr. Stansel: January 9, 2012 AGES of JAX, INC. (AGES) has completed a geotechnical exploration and engineering evaluation of the subsurface conditions beneath the proposed garage building addition construction areas of the referenced project. Our geotechnica l ex ploration was performed in general accordance with our Proposal No. 11 JP5620 dated December 20, 201 1. Our services were formally authorized by Ms. Maiju Stansel of Ri chard Skinner & Associates, Architects on December 21, 2011. This report briefly describes our understanding of the planned construction, describes the field testing performed and presents our recommendations for foundation design and site preparation. 1.0 PROJECT INFORMATION General project information has been provided by Ms. Maiju Stansel of Richard Skinner & Associates, Architects during recent Email co rre spondence dated December 20, 2011 which contained a Site Plan (Sheet No. AO.l) dated December 19, 2011 , prepared by th e cl ient showing the existing residential structure features, site location , th e proposed building addition development and proposed boring locations. Based upon the information provided, we understand that a new two story garage addition and some ex isting residential structure renovations, most notably a retaining wa ll, are planned for the existing residential development located at 1739 Beach Avenue in Atlantic Beach, Florida. The propose d improvements will likely include: * * A 2-story masonry block and /orwood framed garage addition with the under roof living footprint being added approximately 1,100 to 1,200 square feet; A peri meter retaining wa ll on the east side of the proposed garage addition. The proposed addition will be used as a garage on the ground floor and a bedroom on the seco nd floor. Detailed structural loading information was not provided, however we have estimated ma ximum individual column loads on the order of 25 to 50 kips, maximum wa ll loads on the order of 3 to 4 kif and live slab on grade loads of 125 pounds per sq uare foot. The proposed building finish floor and existing site topography data indicates that the proposed structure will probably be constructed at or near existing site grades. AGES of JAX, Inc. POBox 24008, Jacksonville FI 32241-4008 9556 Historic Kings Road South, Suite 201. Jacksonville, Florida 32257-2010 (904) 886-0766 . (904) 880-5190 (FAX) FIELD EXPLORATION PROCEDURES Penetration Boring The penetration boring was made in general accordance with ASTM D 1586-67, "Penetration Test and Split-Barrel Sampling of Soils". The boring was advanced to the water table by augering and, after encounteri ng the groundwater table, further advanced by a "wash-and-chop" drilling technique using a circulating bentonite fluid for borehole flushing and stability. At two-foot intervals within the upper 1 0 feet and at five-foot intervals thereafter, the drilling tools were re moved from the borehole and a split-barrel sampler in serted to the borehole bottom and driven 18 inches into the material using a 140-pound SPT hammer falling, on the average, 30 inches per hammer blow. The number of hammer blows for the final 12 inches of penetration is termed the "p enetration resistance, blow count, or N-value". Thi s value is an index to several in-place geotechnical properties of the material tested, such as relative density and Young's Modulus. After driving the sampler 18 inches (or less, if in hard rock or rock-like material) at each test interval, the sampler was retrieved from the borehole and a representative sample of the material with in the split- barrel was placed in a glass jar and sealed. After completing the drilling operations, the samples for the borin~ were transported to our laboratory where they were examined by our engineer in order to verify the driller s field classifications. The samples will be kept in our laboratory for a period of two months after submittal of formal written report, unless otherwise directed by the client. Auger BoringslDynamic Cone Penetrometer Borings The auger borings were performed manually using a post-hole auger and/or mechanical rig auger. The auger borings were drilled in general accordance with ASTM 0 1452-80 ("Soil Investigation and Sampling by Auger Borings"). Representative samples of the soils brought to the ground surface by the angering process were placed in glass jars, sealed , and transported to our laboratory where they were examinea by a geotechnical engineer to verify the driller's field classification. At one foot depth interva l, th e dynamic cone penetrometer was placed into the borehole and driven 2" to seat the cone. The rod was then driven two consecutive 1.75" increments and the number of blows per increment were recorded. These average of the two blow/counts is correlated to standard penetration resistances. DYNAMIC CONE PENETROMETER RECORDS 1729 Beach Avenue Atlantic Beach, Florida AGES Job No. J15240, Report No. 001 Date Performed' 01/03/12 Performed By' D Anderson DCP RESISTANCE • ~ BLOWS PER: Estimated Auger •• Soil Description DCP Test SPT N- Boring Depth DEPTH 151 2nd VALUE Number (Feet) (Feet) 1.75" 1.75" (BlF) 0.0 -6.0 VERY LOOSE to LOOSE Brown 0.0 1 1 1 Fine SAND 1.0 1 1 1 AP1 2.0 2 1 1 3.0 3 4 3 4.0 2 3 2 5.0 3 4 3 A.B.T. GWL = Not Encountered 6.0 5 5 5 NT = Not Tested BGS = Below Ground Surface GWL = Groundwater Level J8231 dcp1.wpd TEST BORING RECORD JOB NO -;;J",15::.:2:...:4-=-0 __ _ BORING NO B1 Project 1729 Beach Avenue Sheet 1 ---:o'f ----''-'-:;1~~~~- Boring Location Southwest Corner of Garage-12' West of South of Southwest Corner Boring Begun 01/03/12 Ground Elevation NA Datum NA Boring Completed 01 /03/12 Groundwater Depth 9.0' Time: Drilling Date: 01/03/12 Driller D. Anders-'o"'n""''''-.!.''-~~- ELEV. DEPTH (FT) lFTI f--u f--- f--- f---- ---- ---- - 5 ----- f--- f----- ---- - -10 --- ----------- -- -- -15 --- ---- --- ---- -- -- -20 --- -- -- -- -- ---- -- -- -25 -- ---- -- ------ --- - -30 -- - -- J1 5240b1.qpw Engineer _T,-,R-"W",-~~~~~_ MATERIAL DESCRIPTION SAMPLE ~OW NO. BLOWS PER 6-IN. INTERVAL COUNT 1 2 3 4 3 7 LOOSE to VERY LOOSE Grey Fine SAND 2 2 1 2 2 3 3 2 2 2 3 4 4 3 3 4 3 7 LOOSE Grey Slightly Silty Fine SAND 5 2 1 2 3 3 VERY LOOSE Grey Brown Slightly Silty Fine SAND VERY FIRM Light Brown Slightly Silty Fine SAND 6 13 14 11 25 7 10 17 21 38 DENSE Grey Brown Fine SAND 8 12 20 27 47 <>onn9 I ermmatea BORING & SAMPLING, ASTM D1586/CORE DRILLING. ASTM D213 BLOW COUNT IS THE NUMBER OF BLOWS OF A 140 LB. HAMMER FALLING 30 IN. REQUIRED TO DRIVE 1.4 IN. 1.0. SAMPLER 1 FT. I CORRELATION OF N-VALUE WITH RELATIVE DENSITY & CONSISTENCY SANDS AND GRAVEL I I SILTS AND CLAYS NO_ OF BLOWS,N' RELATIVE NO. OF BLOWS, W CONSISTENCY DENSITY 0-2 VERY SOFT 0 -4 VERY LOOSE '·4 SOFT 5 ·10 l OOSE 5-' FIRM 11 ·20 FIRM 9 -15 STIFF 21 -30 VERY FIRM 16 -30 VERY STIFF 31 -50 DENSE 31 -50 HARD OVER 50 VERY DENSE OVER 50 VERY HARD PARTICLE SIZE IDENTIFICATION (UNIFIED SOIL CLASSIFICATIDN SYSTEM) I CATEGORY I DIMENSIONS ; 12 ;"oho< Cobbles 3 to 12 inches Gravel Coarse -0.75 to 3 inches in diameter Sand Coarse -2.0 mm to 4.76 rnm diameter Medium -0.42 mm to 2.0 mm diameter Silt and Clay l ess than 0.074 mm (Invisible to the naked eye) MODIFIERS I These modifiers provide Qurestimate of the amount of minor constituents (sand silt or clay size particles) in the soil sample. PERCENTAGE OF MINOR MODIFIERS CONSTITUENT 5% to 12% Slightly Silty, Slightly Clayey, Slightly Sandy 12% to 30% Silty, Clayey, Sandy 30% to 50% Very Silty, Very Clayey, Very Sandy These modifiers provide our estimate of the amount of other components in the soil sample. APPROXIMATE CONTENT OF OTHER APPROXIMATE CONTENT OF COMPONENTS (SHELL, GRAVEL, MODIFIERS ORGANIC COMPONENTS ETC.) 0% to 5% TRACE 1% to 2% 5% to 12% FEW 2% to 4% 12% to 30% SOME 4% to 8% 30% to 50% MANY >8% wpdac\Form\sod I o z '" « u . ". -N- ~ II PART Of GOVT LOT 4 5fcnou 51 LEGEND: I I I I I I CtM:<Z"', I I I I I I I I -0-Penetration Test Boring Location (approximate) -+-Dynamic Cone Penetrometer Location (approximate) REFERENCE: Drawing Provided by Richard Skinner, and Associates. Undated. in the field use paced and taped measurements of existing site feature and available survey control. Boring locations as shown on this plan are approximate. I.ll! "~""L«.< • '""''''''''''.c.~~ ~ ... .:.! ·'.1':("r·.<~ "'''''CII~<!'''' ".,!,~,.:~. 'L\"'~"' .... f'''''"~ "H!~" ""''''o"o:~ _ .... ," .. " llf-----------'----------Jocksonville. Florida - DRAWN : TSM FIELD EXPLORATION PLAN Beach Atlantic 1729 Ave nue Beach, Florida DATE: 01/09/12 CHECKED: TRW JOB NO: J15240 SCALE: 1"=20' o z ~ u -N-~ . --- I , ,. " -' 1!I(ilall MOllnd I .0.-' .. "! II II ',' ' Ii N:mtucket A\'6 " , I' II 'I'r "- -, , NOR7H BEACH · I , .', " I It' I I,: I ,I , , I' [ , ~' I I!' -JI I ~cbiLn ;1 . .I -, I \ I -,1 ~I --i=--: " 1 , I' __ @ I REFERENCE: Mopquest.com ';".' ,,' 1-----1"?"' _ , Wonderwood ,"0 -I I " I '-' , , -- " a. \ \ / -: "II I, t '. " " ~ j, " " , ,,' -= ~ ~:: I' I ' ,J, I " I r " I " , ", , , 'I " , /, " , , - --~ ,-ill~ \ Manhattan Beach ,1,0 o I \r. I",' 1If---------'--------Jocksonville, Florida SITE LOCATION MAP 1729 Beach Avenu e Atlant ic Beach, Fl orida DRAWN: TSM DATE: 01 /09/1 2 CHECKED : TRW JOB NO: J15240 SCALE: NTS ATTACHMENTS Site Location Map Field Exploration Plan Key to Soil Classification Test Boring Record Dynamic Cone Penetrometer Boring Record Field Exploration Procedures SHALLOW FOUNDATION DESIGN & SITE PREPARATION RECOMMENDATIONS (Cont) may be sufficient to achieve the desired surface compaction of the very loose to loose surficial soils. This compactive effort should help improve the overall uniformity and bearing conditions of the near-surface soils. Using a roller meeting the requirements recommended above, any structural fill required to raise the site to the ptanned finish grades may then be placed in loose lifts not exceeding 12 inches in thickness, and then compacted to densities similar to those recommended above. Structural fill is defined as a non-plastic, inorganic, granular soli containing less than 10 percent material passing the No. 200 mesh sieve (i.e. relatively clean sand). The upper seven(?) feet of sandy soils which were encountered at our penetration test boring location are SUitable for use as "free draining" sand backfill and are to be used behind the retaining wall. The backfill materials for the retaining wall should also meet the requirements of structural fill as mentioned above and be free of large stones, construction debris and organic material. i work construction, work upon these areas should ~~~I~~~~]~~~;~~~~ -Should the near-surface soils and/or structural fill material experience removed and backfilled with "dry" structural fill soils, content on to percent, which are then compacted; or (2) the excess within the disturbed soils allowed to diSSipate before re-compacting. Furthermore) the gr~~~rlg~:~~~J~!~:~ShOUld be checked and controlled as necessary to help insure proper drawdown or any h conditions that may be causing the "pumping" conditions during compaction or co-r1stiCuction activity upon these soils. Foundation Areas -After site and fill compaction is complete, the foundations may be excavated to their planned bearing levels. The exposed bearing level soils should exhibit densities equivalent to 95 percent of the Modified Proctor maximum dry density. For confined foundation areas, any additionally required compaction of the bearing level soils can probably be best achieved using lightweight, vibratory sledsl rollers, or lampersi having a lotal weighl of alleast 100 pounds. Loose lifts of backfilled soil in Ihe founDation excavations, If reqUired, should be placed in thicknesses not exceeding six inches prior to densification with the lightweight compaction equipment. Should "pumping" occur In the exposed bearing level salls of the foundations, treatment of the disturbed soils should be performed as recommendea previously. However, when pumping high waler from lemporary construction slumps to lower high groundwater conditions in the foundation areas, the sumps should be located outside the foundation excavations. Pumping from slumps located within Ihe foundation areas, if allowed, could loosen or disturb Ihe foundation bearing level soils and Ihus Increase Iheir settlemenl potential. Qualltv Control -Prior to initiating compaction operations, we recommend that representative samples olfhe proposed structural fill maleriat and exposed in-place fine sandy soits be collected and tested to determine their compaction and classification characteristics. The maximum dry density, optimum moisture content, gradation, and plasticity characteristics should be determined. These tests are needed for compaction quality control of the structural fill and existing solis, and to determine If Ihe proposed fill materials are acceptable. A representative number of field In-place density tests should also be performed In the compacted existing soils and in each one foot lift of structural fill/backfill, to evaluate whether the required degree of compaction has been obtained. At each test level, we recommend that at least one density fest be performed for every 3,000 square feef 01 bUilding area. In-place density tests should also be performed at representative locations In the bearing level solis of the foollngs. We Iherefore recommend Ihal alleast one density lesl be performed for every 100 square feel of spread footing bearing area, and for every 100 lineal feel of continuous fooling bearing surface. SHALLOW FOUNDATION DESIGN & SITE PREPARATION RECOMMENDATIONS Proposed Residential Structure Add ition -1739 Beach Avenue Atlantic Beach, Florida AGES Job No. J15240, Report No. 001 Should the location of the proposed building be changed or should any condition be encountered during construction which differs from the data documented herein, please contact us immediately so that we may visit the site, observe the differing conditions, and evaluate these findings with regard to the recommendations provided subsequently. Based upon the project information aVailable at this time, we believe that the following recommendations may be used for foundation design; provided site preparation/earthworkand foundation construction is performed in general accordance with our subsequent recommendations. I. FOUNDATION DESIGN RECOMMENDATIONS Foundation Type -We consider conventional shallow bearing footings applicable for this project. An alternate foundation system consisting of a monolithic concrete slab on-grade with thickened sections beneath the load bearing walls and columns is also considered applicable and acceptable for use at this site. Bearing Pressure & Depth -The maximum allowable soil bearing pressure for use in shallow foundation design should not exceed 2,000 psf. The foundations should be designed based upon the maximum load which could be imposed by all load ing conditions. The exterior footmgs should bear at a depth of at least 12 inches below Ihe exterior final grades and the interior footings should bear at least 12 inches below the interior fl oor slab. This minimum bearing depth should provide tne necessary confinement for the soils at the foundation bearing levels. Foundation Size -The minimum widths recommended for isolated sp read-type footings and continuous wall footings are 24 and 18 inches, respective ly. Even though the maximum allowaBle soil bearing pressure may not be achieved, these minimum width recommendations should still control the size of the foundations. Bearing Material -The footings should bear in either the existing surficial fine sandy soils, which will require proper compaction, or in compacted structural fill. The bearing level soils, after compaction, should exhibit densities equivalent to 95 percent of the Modified Proctor maximum dry density (ASTM D 1557). The footing bearing level soils should also be inspected and tested by an engmeering technician from our office, acting under the direction and supervision of the geotechnical engineer, in order to evaluate the density and acceptability of the footing bearing material prior to steel placement and footing construction. II. SITE PREPARATION RECOMMENDATIONS Groundwater Control -During our geotechnical exploration, the groundwater level was encountered at a depth of 9.0 feet below existing site grades. Therefore, encroachment upon the groundwater levels during site work and footing construction is probably unlikely, especially in the area of the retaining wall construction. If encountered, the groundwater should be controlled at all times at a depth of at least two feet below the construction level. Groundwater draw-downs can probably be best achi eved using perimeter drainage ditches which are graded: (1) to a positive gravity outfall away from the site, or (2) to sumps where the collected groundwater and surface water runoff can be controlled by pumping. Structure Demolition and Pavement Removal -Initial site preparation should include the demolition of any eXisting buildings, driveway slabs, foundations and conflicting underground utilities. Any existing foundations encountered should be completely removed, if possible, or cut off to a depth of at least four feet below the existing ground surface. Underground utility conduits, pipes, etc, (if encountered) should be either filled with grout or removed. All excavations reqUiring utility or foundation removal should be backfill ed using clean structural fill placed in six-inch thick lifts and compacted to densities equivalent to 95 percent of the Modified Proctor ma ximum dry density. . The next step of site preparation will be removal of any pavements, topsoils or surface organics from the construction areas. The surface stripping should be performed within and to a distance of at least five feet beyond the perimeter of the planned building construction areas and from within and to a distance of at least three feet beyond the perimeter of the proposed new pavement areas. We expect that average stripping depths on the order of six inches or less will be required for this site. The perimeter areas should be graded to help direct surface water runoff away from the planned construction areas. Site & Fill Compaction -After completion of initial site preparation, the upper two feet of exposed near-surface solis beneath th e building construction area should be compacted to densities equivalent to 95 percent of the Modified Proctor maximum dry density (ASTM D 1557). To compact the exposed soils, we recommend using a static drum roller which has a static at-drum weight on the order of one to two to ns and a drum diameter on the order of two to three feet. A walk behind double drum roller or plate compactor RICHARD SKINNER & ASSOCIATES, ARCHITECTS Jacksonville, Florida January 9,2011 Page 4 modifications that may be required to verify that our recommendations have been properly interpreted and implemented. Our report has been written in a guideline recommendation format and is not appropriate for use as (or inclusion into) th e specifica tions without being reworded in a specification type format. Although preferably this report should not be made part of the contract documents, it should be made available to prospective contractors for information purposes. We appreciate the opportunity to be of service as the geotechnical consultant during th is phase of your project. Should you have any questions concerning this report or if we may be of any further service to you, please feel free to contact us. TRW/trw/J15240.wpd Attachments Dist ribution: Addressee (3) RICHARD SKINNER & ASSOCIATES, ARCHITECTS Jacksonville, Florida January 9, 2011 Page 3 The auger/dynamic cone penetrometer boring (AP1), performed on th e east side of the existing garage, encountered very loose to loose brown fine sands to the maximum boring depth of 6 feet. Penetration resistance values were on the order of 1 to 5 blows per foot. The groundwater leve[ was encountered at the penetration test boring(B 1) location and recorded, at the time of drilling, at depths of approximately 9.0 feet be[owexisting site grades. This level is significantly [ower th an typical season average levels. The groundwater level should be expected to fluctuate due to seasonal climatic variations, surface water runoff patterns across the site, construction activity and the subsequent development as planned, and other interrelated factors. Since groundwater variations are anticipated, design drawings and specifications should accommodate such possibilities, and construclion planning should be based on the assumption that variations wil l occur. 4.0 CONCLUSIONS Our geotechnical engineering evaluation of the site and subsurface conditions with respect to the planned construction and imposed structural loading conditions, and our recommendations for foundation design/construction and site preparation, are based upon: (1) our site observations; (2) the field test data obtained during this geotechnical exploration of the site; and (3) our understanding of the project information and structural loading conditions as presented in this report. The field test data has been compared with similar soils at other sites w here structures of similar mag nitude are satisfactorily supported by shallow foundations. Based upon our findings and our understanding of the proposed construction w hich includes the understanding that the proposed project site is west of the Coastal Construction Setback Line, it is our opinion thatthe site and subsurface conditions are adaptable for shallow foundation support ofthe proposed residential structure addition. We recommend that the initial site work consist of clearing any conflicting vegetation from within the planned building foot print and completing any required demolition. Subsequent to initial site preparation, the surface soils should be compacted with a static drum roller or plate tamp to improve density and uniformity of the upper one to two feet of loose soil. The upper two feet of soil should be compacted to densities equiva[entto 95% of the Modified Proctor Maximum Dry density (ASTM 01 557). Subsequent to site compaction, any required structural fill may be placed in one foot lifts and compacted to the above specified density. Shallow-bearing footings, designed with a maximum allowab[e soil bearing pressure of 2,000 psf, may then be constructed to support the residential structure. The foundations should bear at [east 12 inches below the exteri or finished grades in order to provide the necessary confinement for the foundation bearin g level soil s. Based upon mag nitudes of the anticipated fill associated with th e project, and the assumed structural loading information, we estimate that total settlements of the new structure could be on the order of 1-inch or less. We expect compression settlements of the subsurface soils to occur fairly rapidly during the construction process. Following site work construction techniques in general accordance with our subsequent recommendations, we anticipate that differential settlements of the building should be within tolerable magnitudes. 5.0 CLOSURE More detailed recommendations for foundation design and site work construction are provided on the following pages, and shou ld be reviewed for specifics. We do recommend, however, that our firm be retained to make a general review of the final plans and specifications. [f necessary, we will suggest any RICHARD SKINNER & ASSOCIATES, ARCHITECTS Jacksonville, Florida 2.0 GEOTECHNICAL EXPLORATION January 9, 2011 Page 2 To explore the subsurface conditions within th e planned building construction addition area, our personnel performed one(1) 25 -foot deep penetration test boring (B1) and one(1) 6-foot auger/dynamic cone penetrometer boring. The borings were performed on January 3, 2012. The boring locations were established by our personnel using paced and taped measurements from the existing site features and survey control. The boring locations, as shown on the Field Exploration Plan, should be considered approxi mate. The ground surface elevations at the boring locations we re not provided. The attached Test Boring and Dynamic Cone Penetrometer Boring Records present the descriptions of the subsurface soils encountered, the groundwater levels encountered and the penetration resistance values recorded when drilling and sampling the test borings. The stratification lines and depth designations on the boring records represent the approximate boundary between the various soils encountered, as determined in the field by our drillers; and the transition from one strata to the next should be considered approximate. A brief discussion of the drilling, sampling, and field testing techniques used during the geotechnical exploration is provided in the attached Field Exploration Procedures section. Representative soil samples obtained during our field exploration were returned to our laboratory. The samples were examined by a geotechnical enginee r and were visually classified in general accordance with ASTM D 2488 (Unified Soil Classification System). 3.0 FINDINGS AGES representatives visited the site on January 3,2012 to investigate existing site conditions. The subject site is located at 1739 Beach Avenue and is bounded on the east by the Atlantic Ocean and on the north. south and west by existing residential development. [t should be noted that the proposed residential stru cture building addition is located west of the Coastal Construction Setback Line. The site is directly adjacent to and encompasses the existing garage portion of the residential development. The site is somewhat relatively level in topography in th e existing garage area but slopes upward on the east end of the site. Surface soils consisted of brown and grey fine sands. No standing water was observed at the site at the time of our visit. The subsurface conditions outlined below highlight the major subsurface stratifications encountered during this geotechnical exploration at the site. More detailed descriptions of the subsurface materials encountered during thi s exploration are provided on the attached boring records. When reviewing the boring records and subsurface profile and the subsurface conditions ou tlined below, it should be understood that the subsurface conditions will vary across the proposed construction area and between the boring locations. Boring B1, performed at the southwest corn er of the existing garage, encountered an approximate 12-foot thick surficial stratum of loose to very loose grey and grey brown fine sand s and s[ightly silty fine sands. The standard penetration resistance values within this surficial stratum ranged from 3 to 7 blows/foot. The surficial sa nds were und erlain by very firm light brown s[ightly silty fine sands to a depth of 17 feet. The standard penetration resistance va lue within this stratu m was 25 blows/foot. This stratum was underlain by dense grey brown fin e sands which extended to the maximum boring termination depth of25 feet. The standard penetration resistance values within this stratum ranged from 38 to 47 blows/foot.