REPORT OF TOWER OAKS PRESERVE PARKWAY ROCKVILLE,MARYLAND EYA

Transcription

1 REPORT OF PRELIMINARY SUBSURFACE EXPLORATION AND GEOTECHNICAL ANALYSIS TOWER OAKS PRESERVE PARKWAY ROCKVILLE,MARYLAND ECS PROJECT NO.: FOR EYA NOVEMBER 26, 214

2 November 26, 214 Mr. Jason Sereno EYA 48 Hampden Lane, Suite Bethesda, Maryland 2814 ECS Job No.: Reference: Report of Preliminary Subsurface Exploration and Geotechnical Analysis, Tower Oaks, Preserve Parkway, Rockville, Maryland Dear Mr. Sereno: As authorized by acceptance of our proposal GP dated October, 214, ECS Mid- Atlantic, LLC (ECS) has completed a preliminary subsurface exploration and geotechnical engineering analysis for the proposed development. We understand that planned future use of the project site will consist of 2 townhomes, single family residences, and 1 condominium units across the currently wooded 41 acre parcel. New stormwater management facilities may also be required. Associated paved parking and roadways will also be constructed. No information regarding site grading or structural loading is available at this time. Our report, including the results of our preliminary subsurface exploration program, and geotechnical engineering analysis is enclosed with this letter, along with a Boring Location Diagram. We appreciate this opportunity to be of service to you on this project. If you have any questions regarding the information and recommendations contained in the accompanying report, or if we may be of further assistance to you in any way during planning or construction of this project, please do not hesitate to contact us. Respectfully, ECS MID-ATLANTIC, LLC Gregory A. Ratkowski Senior Project Manager Jeffrey A. McGregor, P.E. Principal Engineer Enclosures: (1) Report I:\Department Geotechnical\GEOTECHNICAL\PROJECTS\66's\1-664 Tower Oaks\1-664 Tower Oaks Report.doc

3 REPORT OF PRELIMINARY SUBSURFACE EXPLORATION AND GEOTECHNICAL ANALYSIS PROJECT Tower Oaks Preserve Parkway Rockville, Maryland CLIENT Mr. Jason Sereno EYA 48 Hampden Lane, Suite Bethesda, Maryland 2814 PROJECT DATE November 26, 214

4 TOWER OAKS TABLE OF CONTENTS PROJECT OVERVIEW Project Location and Proposed Construction Scope of Work Purposes of Exploration EXPLORATION PROCEDURES Subsurface Exploration Procedures EXPLORATION RESULTS Current Site Conditions Regional Geology Soil Conditions Groundwater Observations PRELIMINARY GEOTECHNICAL ANALYSIS AND RECOMMENDATIONS Preliminary Foundation Recommendations Preliminary Floor Slab Design Below Grade and Retaining Walls Earthwork Operations Fill, Floor, and Pavement Subgrades Fill Placement Construction Considerations Closing APPENDIX PAGE

5 Tower Oaks ECS Project No November 26, 214 Page 1 PROJECT OVERVIEW Project Location and Proposed Construction The project site is located along the east side of Preserve Parkway in Rockville, Maryland. The site is currently wooded. A Site Location Diagram, included in the Appendix, shows the project location. We understand that final development plans have not yet been made available for this site, however based on our review of the provided conceptual plans, the planned future use of the project site will consist of 2 townhomes, single family residences, and 1 condominium units across the currently wooded 41 acre parcel. New stormwater management facilities may also be required. Associated paved parking and roadways will also be constructed. No information regarding site grading or structural loading is available at this time, however we have assumed that maximum column loads will be approximately 1 to 2 kips for the purpose of our analysis. Scope of Work The conclusions and recommendations contained in this preliminary report are based on our field subsurface explorations, and review of available geologic data. Our subsurface exploration program included a total of six (6) soil borings extended to depths between approximately 6. feet to 2 feet below the existing ground surface. We have also visited the site to conduct a site reconnaissance of current conditions. The boring locations were selected and located in the field by ECS personnel. The Boring Location Diagram in the Appendix indicates the approximate physical location of the borings performed at the site. No topographic site plans were available to us to estimate existing site grades. Purposes of Exploration The purpose of the exploration was to explore the soil and groundwater conditions at the site and to develop preliminary engineering recommendations to guide the design and construction of the proposed school. We accomplished these purposes by: 1. drilling borings to explore the subsurface soil and groundwater conditions, 2. performing visual classification testing, and. analyzing the field results to develop appropriate preliminary engineering recommendations.

6 Tower Oaks ECS Project No November 26, 214 Page 2 Subsurface Exploration Procedures EXPLORATION PROCEDURES The soil borings were performed with a track mounted auger drilling rig (CME-), which utilized continuous flight, hollow stem augers to advance the boreholes. Drilling fluid was not used in this process. Representative soil samples were obtained by means of the split-spoon sampling procedure in accordance with ASTM Specification D-186. In this procedure, a 2-inch O.D., split-spoon sampler is driven into the soil a distance of inches by a 14-pound hammer falling inches. The number of blows required to drive the sampler through the last 12-inch interval is termed the Standard Penetration Test (SPT) value, or N value, and is indicated for each sample on the boring logs. This value can be used as a qualitative indication of the in-place relative density of noncohesive soils. In a less reliable way, it also indicates the consistency of cohesive soils. This indication is qualitative, since many factors can significantly affect the standard penetration resistance value and prevent a direct correlation between drill crews, drill rigs, drilling procedures, and hammer-rod-sampler assemblies. A field log of the soils encountered in the borings was maintained by the drill crew. After recovery, each sample was removed from the sampler and visually classified. Representative portions of each sample were then sealed and brought to our laboratory for further visual examination and laboratory testing. An experienced soil engineer classified each soil sample on the basis of texture and plasticity in accordance with the Unified Soil Classification System. The group symbols for each soil type are indicated in parentheses following the soil descriptions on the boring logs. A brief explanation of the Unified System is included with this report. The soil engineer grouped the various soil types into the major zones noted on the boring logs. The stratification lines designating the interfaces between earth materials on the boring logs and profiles are approximate; in situ the transitions may be gradual. Current Site Conditions EXPLORATION RESULTS The project site is located along the east side of Preserve Parkway in Rockville, Maryland and is currently wooded. Commercial buildings and associated parking areas are located to the north and northwest of the project site. To the east and southeast of the site is the Woodmont Country Club and golf course. Wooded land is located on the south side of the site with additional commercial buildings and associated parking located further south. To the west of the site is Preserve Parkway and wooded land. Existing site grades are not known; however, our site visit indicates the site contains rolling hills.

7 Tower Oaks ECS Project No November 26, 214 Page Regional Geology According to the Physiographic Map of Maryland (28), the site is located within the Hampstead Upland District of the Piedmont Plateau Province. The Piedmont Plateau Province is an area underlain by ancient igneous and metamorphic rock. The virgin soils encountered in this area are the residual product of in-place chemical weathering of the parent rock presently underlying the site. The typical residual soil profile consists of silty to clayey soils near the surface where soil weathering is more advanced, underlain by more sandy silts and silty sands that generally become harder and denser with depth to the top of parent bedrock. The boundary between soil and rock, termed weathered or decomposed rock, is not sharply defined. This transitional zone can contain boulders of more resistant rock as well as highly weathered materials. The Hampstead Upland District is described as rolling to hilly uplands interrupted by steepwalled gorges. Differential weathering of adjacent, contrasting lithologies produces distinctive ridges, hills, barrens, and valleys. Streams may have short segments of narrow, steep-sided valleys. According to the Geologic Map of the Frederick x 6 Quadrangle, Maryland, Virginia, and West Virginia (27), the project site is located near the Plummers Island Fault which separates the Sykesville Formation (to the west) and the Phyllonite of the Mather Gorge Formation (to the east). The Sykesville Formation is Lower Cambrian in age and is described as variegated, Gray Metamorphosed sedimentary mélange consisting of a quartzofeldspathic granofels matrix containing quartz and feldspar grains, and fragments and bodies of metamorphosed sedimentary, volcanic, and intrusive rocks. The Phyllonite of the Lower Cambrian and or Neoproterozoic Mather Gorge Formation is described as highly folded, greenish-gray, chlorite-sericite phyllonite containing white vein quartz. Soil Conditions Subsurface conditions within the proposed site were evaluated with six (6) soil test borings (SB- 1 to SB-6) drilled to a maximum depth of 2 feet below the existing ground surface. The approximate boring locations are presented on the enclosed Boring Location Diagram. Approximately two (2) to six (6) inches of topsoil was encountered at all boring locations. Topsoil depths may be deeper in other areas of the site not currently explored, especially in the more heavily wooded areas of the site. Natural soils were encountered below the existing ground cover and consisted of Sandy SILT (ML), Clayey SILT (ML/CL), SILT (ML), and LEAN to FAT CLAY (CL/CH). The natural cohesionless (ML and ML/CL) soils contained trace amounts of clay, sand and gravel. Based on Standard Penetration Test (SPT) results, the density of the natural cohesionless soils ranged from loose to dense but were predominately medium dense. The natural cohesive (CL and CL/CH) soils contained trace amounts of sand. Based on Standard Penetration Test (SPT) results, the consistency of the natural cohesive soils ranged from medium stiff to stiff. The color of these soils was brown to reddish brown and the moisture contents of these materials were characterized as moist.

8 Tower Oaks ECS Project No November 26, 214 Page 4 Decomposed rock materials were encountered at four of the borings at depths of ranging from feet to 17 feet below existing grades. These materials exhibit rock like qualities and depending on various parameters may be extremely difficult to excavate, and portions of the decomposed rock will require rock excavation methods for removal. The chart below shows the depth where decomposed rock material was encountered and the extent of each of the borings. Boring Location Depth to Decomposed Rock Material Depth to End of Boring (EOB) or Auger Refusal (AR) B-1 ' 6.' AR B-2 17' 2' EOB B- - 2' EOB B-4 8' 1.' AR B- 12' 17' AR B-6* - 2' EOB More detailed descriptions of the soils encountered are presented on the Boring Logs in the Appendix. Groundwater Observations Groundwater was not encountered during drilling operations. Observations for groundwater were made during sampling and upon completion of the drilling operations at each boring location. In auger drilling operations, water is not introduced into the boreholes, and the groundwater position can often be determined by observing water flowing into or out of the boreholes. Furthermore, visual observation of the soil samples retrieved during the auger drilling exploration can often be used in evaluating the groundwater conditions. Variations in the location of the long-term water table may occur as a result of changes in precipitation, evaporation, surface water runoff, and other factors not immediately apparent at the time of this exploration. Free water may also be encountered at the interface of existing fill and natural soils or at the interface of natural soils and weathered rock or bedrock. PRELIMINARY GEOTECHNICAL ANALYSIS AND RECOMMENDATIONS The preliminary recommendations presented in this report are based on the limited project information provided to us, the results of the soil test borings, and our engineering analysis. Considering the results of our field exploration, and based on our experience with similar projects, it is our opinion that the site can be made suitable for construction of the proposed residential development. Based on our assumed structural loading, it is anticipated that traditional shallow spread footings may be feasible. The natural soils are considered to be suitable for the support of slabs on grade, provided that the subgrade soils have been properly prepared, as described in this report, and approved by the Geotechnical Engineer or their authorized representative. Existing fill materials will not be suitable for support of footings. Preliminary Foundation Recommendations Based on the test borings and a lowest finished floor level at or near existing grades, the soils anticipated at nominal foundation subgrade levels are expected to consist of natural medium dense natural silty or clayey soils. Some new compacted fill is also anticipated once site grading

9 Tower Oaks ECS Project No November 26, 214 Page operations are finalized. Based on the results of the subsurface exploration, recommendations outlined in the Earthwork Operations section, and our engineering analysis, the proposed structures can be supported on spread footing foundations when founded on suitable natural materials. Footings should not be designed to bear on existing fill or materials which do not meet the criteria outlined below. If unsuitable bearing materials are encountered at footing subgrade levels, footings should be lowered to bear on suitable soils at greater depths. The geotechnical analysis of the soil indicates that footings supported on the natural medium dense silty materials may be designed for a bearing pressure of, to, psf. Materials capable of supporting a, to, psf bearing pressure can be identified on our boring logs as those materials exhibiting a minimum SPT N-value of 7 to 1 bpf. Higher bearing pressures may be possible depending on actual lowest bearing elevations and site grading. Settlement of individual footings, designed in accordance with the recommendations outlined above, is expected to be within tolerable limits. Within the proposed construction, total settlements on the order of one inch are anticipated, with differential settlement on the order of about half the total settlement. The net allowable soil bearing pressure refers to that pressure which may be transmitted to the foundation bearing soils in excess of the final minimum surrounding overburden pressure. Preliminary Floor Slab Design According to the test borings and assuming that the new structures will be at or near existing grades, the soils anticipated below the floor slabs should consist of natural silty or clayey soils. These soils are expected to be suitable for support of the floor slabs. Some undercutting and replacement of loose surficial material soils may also be necessary in some areas. The floor slab subgrade should be prepared in accordance with our recommendations outlined in the section entitled "Earthwork Operations", which includes stripping and fill placement. We recommend that a capillary cutoff layer be provided under the floor slabs to prevent the rise of moisture through the floor slab. The capillary layer should consist of a minimum of 4 inches of dense graded gravel, or open graded stone. CR-6 or AASHTO No. 7 stone should be suitable for this purpose. A 6 mil polyethylene barrier should be placed on top of the stone to provide additional moisture protection and prevent concrete intrusion into the stone. Placement of this barrier should occur immediately before the placement of floor slab concrete in order to minimize damage to the layer. However, special attention should be given to the surface curing of the slab in order to minimize uneven drying of the slab and associated cracking. Below Grade and Retaining Walls Any below grade walls should be designed to withstand lateral earth pressures and surcharge loads. For preliminary purposes, we recommend that below grade walls be designed for a linearly increasing lateral earth pressure of 6 psf per vertical foot of wall. Any retaining walls which are free to rotate at the top and mobilize more of the sheer strength of the soil, should utilize an active lateral earth pressure of 4 psf per foot of wall height, when the back grades are horizontal. These pressures assume that granular materials classifying ML or more granular will be used for backfill behind walls and that drainage behind the walls will be provided as previously discussed. These pressures should not be used for sheeting and shoring design.

10 Tower Oaks ECS Project No November 26, 214 Page 6 Earthwork Operations There are mainly two elements associated with the successful completion of the earthwork operations for this site. First, subgrades receiving fill must be properly prepared and observed, and second, the monitoring of newly placed fill, with respect to lift thickness and compaction of each lift. The following paragraphs detail our recommendations regarding earthwork operations. Fill, Floor, and Pavement Subgrades The existing ground surface in the proposed fill, floor, and pavement areas should be stripped of all building debris, pavement, vegetation, rootmat, root balls, stumps, topsoil, and any soft or unsuitable material. The stripping within the proposed roadway areas should be extended at least 1 feet, where possible, beyond the planned limits. After stripping to the desired grade and performing all necessary excavation and prior to fill and/or gravel placement, the exposed soils should be carefully examined to identify any localized loose, yielding or otherwise unsuitable materials by an experienced Geotechnical Engineer or their authorized representative. After examining the exposed soils, loose and yielding areas should be identified by proofrolling with an approved piece of equipment, such as a loaded dump truck, having an axle weight of at least 1 tons. Any soft or unsuitable materials encountered during this proofrolling should be removed and replaced with an approved engineered fill compacted to the criteria given below in the section entitled Fill Placement. The preparation of fill and pavement subgrades should be observed by an experienced geotechnical engineer, or their representative, to verify that all unsuitable materials have been removed, and that the subgrade is suitable for support of the proposed construction and/or fills. In some areas, excessively soft and/or wet soils may be encountered at fill subgrades, especially in the winter or early spring months. All soft areas shall be excavated and removed. We recommend establishing a budget for additional undercuts of soft surfical soils during subgrade preparation. Fill Placement Upon achieving competent subgrade materials, the exposed soils should be filled, where appropriate, to planned building or pavement subgrade levels with an approved controlled, compacted engineered fill. Engineered fill for support of buildings and pavements should consist of soils classified ML, SM, SC, or more granular per ASTM D-2487 and have a liquid limit less than 4 and plasticity index less than 2. Unacceptable fill materials include topsoil, organic materials (OH, OL) and high plasticity silts and clays (MH, CH). All such materials removed during grading operations should be either stockpiled for later use in landscape fills, or placed in approved disposal areas either on-site or off-site. All other soil materials not excluded above are acceptable for reuse as fill, provided that the moisture content is within acceptable levels to obtain compaction. An examination of the soils recovered during our current exploration and our previous experience in the area indicates that a majority of the on site natural silty soils may be suitable for reuse as controlled, compacted fill, with moisture adjustment during fill placement. Existing fill materials will be suitable for reuse provided they are free of deleterious material and meet the criteria provided above.

11 Tower Oaks ECS Project No November 26, 214 Page 7 Some potentially highly plastic clays (CH) were encountered within the borings. These soils are NOT expected to be suitable for reuse as structural fill. It should be noted that prior to the utilization of any off-site borrow materials, the Geotechnical Engineer should be provided with representative samples in order to determine the material s suitability for use as a controlled compacted fill and to develop moisture-density relationships. In order to expedite the earthwork operations, off-site borrow materials should be comprised of a select granular material which will provide suitable support, and be easily compacted and well drained. All structural fill should be placed in loose lifts, which do not exceed 8 inches in thickness, and should be compacted to at least 9 percent of the maximum dry density, as determined by the Standard Proctor Compaction Test (ASTM D-698). Fill soils placed in the top inches below pavements should be compacted to at least 1% of the maximum dry density, as determined by ASTM D-698. Generally, the moisture content of the fill materials should be maintained within 2 percent of the optimum moisture content for the fill material, as determined by ASTM D-698. However, if soils can be compacted outside of this moisture content range to the required compaction without excessive movement, as determined by the geotechnical engineer, the fill could be considered suitable. Fill placed in non-structural areas (e.g. grassed areas) should be compacted to at least 9 percent of the maximum dry density according to ASTM D- 698, in order to avoid significant subsidence. Construction Considerations Precautionary measures should be taken to ensure that preparation of the subgrades is accomplished by the recommended procedures. These precautions are necessary, as the materials observed in our borings are disturbance sensitive, and will become weakened if water is allowed to pond on them. Therefore, we recommend that all excavations be properly dewatered, if necessary, using conventional sump pit and pumping operations. The site should be graded such that surface water runoff is directed away from the excavations. The surficial soils contain fines which are considered moderately erodible. The Contractor should provide and maintain good site drainage during earthwork operations to help maintain the integrity of the surface soils. The surface of the site should be kept properly graded in order to enhance drainage of the surface water away from the proposed construction areas during the earthwork phase. Other practices would involve sealing the exposed soils daily with a smooth drum roller to reduce the potential for infiltration of surface water in the exposed soils. All erosion and sedimentation shall be controlled in accordance with sound engineering practice and current County requirements.

12 Tower Oaks ECS Project No November 26, 214 Page 8 Closing This preliminary report has been prepared to aid in the evaluation of this site and to assist the design team with the design of the proposed residential development. No final site plans exist at this time, and once such plans are available, a final geotechnical study with additional borings should be completed. This report is limited to the locations described. As this report is preliminary in nature, we recommend that additional subsurface exploration be performed as well as a final geotechnical analysis once final site grades and building loads are determined. We have appreciated the opportunity to be of service to you and hope to continue our involvement on the project during the final design and construction phases. ECS-Mid-Atlantic, LLC (ECS) is capable of providing all construction materials testing services for the project, and we would appreciate the opportunity to offer our services.

13 APPENDIX Site Location Diagram Lateral Earth Pressure Diagram Unified Soil Classification Diagram Reference Notes for Boring Logs Boring Logs (SB-1 to SB-6) Boring Location Diagram

14

15

16 UNIFIED SOIL CLAIFICATION SYSTEM (ASTM D 2487) Coarse-grained soils (More than half of material is larger than No. 2 Sieve size) Major Divisions Gravels (More than half of coarse fraction is larger than No. 4 sieve size) Sands (More than half of coarse fraction is smaller than No. 4 sieve size) Clean gravels (Little or no fines) Gravels with fines (Appreciable amount of fines) Clean sands (Little or no fines) Sands with fines (Appreciable amount of fines) Group Symbols GM a SM a GW GP GC SW SP SC d u d u Typical Names Well-graded gravels, gravelsand mixtures, little or no fines Poorly graded gravels, gravel-sand mixtures, little or no fines Silty gravels, gravel-sand mixtures Clayey gravels, gravel-sandclay mixtures Well-graded sands, gravelly sands, little or no fines Poorly graded sands, gravelly sands, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Determine percentages of sand and gravel from grain-size curve. Depending on percentage of fines (fraction smaller than No. 2 sieve size), coarse-grained soils are classified as follows: Less than percent GW, GP, SW, SP More than 12 percent GM, GC, SM, SC to 12 percent Borderline cases requiring dual symbols b Laboratory Classification Criteria C u = D 6 /D 1 greater than 4 C c = (D ) 2 /(D 1 xd 6 ) between 1 and Not meeting all gradation requirements for GW Atterberg limits below A line or P.I. less than 4 Atterberg limits below A line or P.I. less than 7 C u = D 6 /D 1 greater than 6 C c = (D ) 2 /(D 1 xd 6 ) between 1 and Above A line with P.I. between 4 and 7 are borderline cases requiring use of dual symbols Not meeting all gradation requirements for SW Atterberg limits above A line or P.I. less than 4 Atterberg limits above A line with P.I. greater than 7 Limits plotting in CL-ML zone with P.I. between 4 and 7 are borderline cases requiring use of dual symbols Fine-grained soils (More than half material is smaller than No. 2 Sieve) Silts and clays (Liquid limit less than ) Silts and clays (Liquid limit greater than ) Highly Organic soils ML CL OL MH CH OH Pt Inorganic silts and very fine sands, rock flour, silty or clayey fine sands, or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts Inorganic clays of high plasticity, fat clays Organic clays of medium to high plasticity, organic silts Peat and other highly organic soils Plasticity Index Plasticity Chart "A" line CH CL MH and OH CL-ML ML and OL Liquid Limit a Division of GM and SM groups into subdivisions of d and u are for roads and airfields only. Subdivision is based on Atterberg limits; suffix d used when L.L. is 28 or less and the P.I. is 6 or less; the suffix u used when L.L. is greater than 28. b Borderline classifications, used for soils possessing characteristics of two groups, are designated by combinations of group symbols. For example: GW-GC,well-graded gravel-sand mixture with clay binder. (From Table Winterkorn and Fang, 197)

17 REFERENCE NOTES FOR BORING LOGS I. Drilling Sampling Symbols Split Spoon Sampler ST Shelby Tube Sampler RC Rock Core, NX, BX, AX PM Pressuremeter DC Dutch Cone Penetrometer RD Rock Bit Drilling BS Bulk Sample of Cuttings PA Power Auger (no sample) HSA Hollow Stem Auger WS Wash sample REC Rock Sample Recovery % RQD Rock Quality Designation % II. Correlation of Penetration Resistances to Soil Properties Standard Penetration (blows/ft) refers to the blows per foot of a 14 lb. hammer falling inches on a 2-inch OD split-spoon sampler, as specified in ASTM D 186. The blow count is commonly referred to as the N-value. A. Non-Cohesive Soils (Silt, Sand, Gravel and Combinations) Density Relative Properties Under 4 blows/ft Very Loose Adjective Form 12% to 49% to 1 blows/ft Loose With % to 12% 11 to blows/ft Medium Dense 1 to blows/ft Dense Over 1 blows/ft Very Dense Particle Size Identification Boulders 8 inches or larger Cobbles to 8 inches Gravel Coarse 1 to inches Medium ½ to 1 inch Fine ¼ to ½ inch Sand Coarse 2. mm to ¼ inch (dia. of lead pencil) Medium.42 to 2. mm (dia. of broom straw) Fine.74 to.42 mm (dia. of human hair) Silt and Clay. to.74 mm (particles cannot be seen) B. Cohesive Soils (Clay, Silt, and Combinations) Blows/ft Consistency Unconfined Comp. Strength Q p (tsf) Degree of Plasticity Plasticity Index Under 2 Very Soft Under.2 None to slight 4 to 4 Soft Slight 7 to 8 Medium Stiff.-.99 Medium to 1 Stiff High to Very High Over to Very Stiff to Hard Over 1 Very Hard Over 8. III. Water Level Measurement Symbols WL Water Level BCR Before Casing Removal DCI Dry Cave-In WS While Sampling ACR After Casing Removal WCI Wet Cave-In WD While Drilling Est. Groundwater Level Est. Seasonal High GWT The water levels are those levels actually measured in the borehole at the times indicated by the symbol. The measurements are relatively reliable when augering, without adding fluids, in a granular soil. In clay and plastic silts, the accurate determination of water levels may require several days for the water level to stabilize. In such cases, additional methods of measurement are generally applied.

18 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB-1 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 S-2 SAMPLE TYPE SAMPLE DIST. (IN) 9 RECOVERY (IN) 8 8 DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [2"] (ML) SANDY SILT, Trace Clay, Orange, Moist, Loose (ML) DECOMPOSED ROCK SAMPLED AS SANDY SILT WITH GRAVEL, Grayish Brown, Moist, Very Dense ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" / 8 CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT / S- S AUGER 6.' /2 / /2 / THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/14/14 WL(BCR) WL(ACR) BORING COMPLETED 11/14/14 CAVE IN WL RIG CME FOREMAN Dale Price DRILLING METHOD HSA

19 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB-2 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 SAMPLE TYPE SAMPLE DIST. (IN) RECOVERY (IN) 14 DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [4"] (CL/CH) LEAN TO FAT CLAY, Trace Sand, Reddish Brown, Moist, Stiff ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" 7 12 CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT S-2 (ML/CL) CLAYEY SILT, Trace Sand, Reddish Brown, Moist, Loose S- (ML) SILT, Trace Sand, Trace Clay, Orangish Brown, Moist, Medium Dense S-4 12 (ML) SANDY SILT, Brown, Moist, Medium Dense S S-6 14 (ML) DECOMPOSED ROCK SAMPLED AS SANDY SILT WITH GRAVEL, Grayish Brown, Moist, Very Dense END OF 2.' THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/14/14 WL(BCR) WL(ACR) BORING COMPLETED 11/14/14 CAVE IN 14.8' WL RIG ATV FOREMAN Dale Price DRILLING METHOD HSA

20 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB- 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 SAMPLE TYPE SAMPLE DIST. (IN) RECOVERY (IN) 14 DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [6"] (ML/CL) CLAYEY SILT, Trace Sand, Brown, Moist, Medium Dense ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT S S- (ML) SANDY SILT, Brown, Moist, Medium Dense to Loose S S- 8 (ML) SANDY SILT, Trace Gravel, Light Brown, Moist, Medium Dense S-6 END OF 2.' THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/14/14 WL(BCR) WL(ACR) BORING COMPLETED 11/14/14 CAVE IN 1.1' WL RIG ATV FOREMAN Dale Price DRILLING METHOD HSA

21 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB-4 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 SAMPLE TYPE SAMPLE DIST. (IN) RECOVERY (IN) DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [4"] (ML) SILT WITH SAND, Trace Clay, Brown, Moist, Medium Dense ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" 7 12 CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT S-2 (ML) SANDY SILT, Trace Gravel, Brown, Moist, Medium Dense to Dense S S-4 6 (ML) DECOMPOSED ROCK SAMPLED AS SANDY SILT WITH GRAVEL, Grayish Brown, Moist, Very Dense S- AUGER 1.' / / THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/14/14 WL(BCR) WL(ACR) BORING COMPLETED 11/14/14 CAVE IN 9.7' WL RIG ATV FOREMAN Dale Price DRILLING METHOD HSA

22 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB- 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 SAMPLE TYPE SAMPLE DIST. (IN) RECOVERY (IN) 14 DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [4"] (CL/CH) LEAN TO FAT CLAY, Trace Sand, Reddish Brown, Moist, Stiff ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT S-2 (CL) LEAN CLAY, Trace Sand, Reddish Brown, Moist, Stiff 7 12 S- (ML/CL) CLAYEY SILT, Trace Sand, Reddish Brown, Moist, Medium Dense S S- 2 2 (ML) DECOMPOSED ROCK SAMPLED AS SANDY SILT WITH GRAVEL, Grayish Brown, Moist, Very Dense /2 /2 S-6 AUGER 17.' / / 2 2 THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/14/14 WL(BCR) WL(ACR) BORING COMPLETED 11/14/14 CAVE IN 12.2' WL RIG ATV FOREMAN Dale Price DRILLING METHOD HSA

23 CLIENT JOB # BORING # SHEET EYA PROJECT NAME 664 ARCHITECT-ENGINEER SB-6 1 OF 1 Tower Oaks - Preliminary SITE LOCATION Preserve Parkway, Rockville, Montgomery County NORTHING EASTING STATION DEPTH (FT) SAMPLE NO. S-1 SAMPLE TYPE SAMPLE DIST. (IN) RECOVERY (IN) 16 DESCRIPTION OF MATERIAL BOTTOM OF CASING SURFACE ELEVATION Topsoil Depth [6"] (CL/CH) LEAN TO FAT CLAY, Trace Sand, Reddish Brown, Moist, Medium Stiff ENGLISH UNITS LO OF CIRCULATION WATER LEVELS ELEVATION (FT) BLOWS/6" CALIBRATED PENETROMETER TONS/FT ROCK QUALITY DESIGNATION & RECOVERY RQD% REC.% 2% 4% 6% 8% 1% PLASTIC LIMIT % WATER CONTENT % LIQUID LIMIT % STANDARD PENETRATION BLOWS/FT S-2 16 (CL) LEAN CLAY, Trace Sand, Reddish Brown, Moist, Stiff S- (ML) SANDY SILT, Brown, Moist, Medium Dense S S- (ML) SANDY SILT, Trace Gravel, Light Brown, Moist, Medium Dense S-6 END OF 2.' THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES. IN-SITU THE TRANSITION MAY BE GRADUAL. WL WS WD BORING STARTED 11/1/14 WL(BCR) WL(ACR) BORING COMPLETED 11/1/14 CAVE IN 14.9' WL RIG ATV FOREMAN Dale Price DRILLING METHOD HSA

24