the following report describes the project characteristics
TRANSCRIPT
July 7, 2018
Mr. Bassam Amin, P.E.
715 Princess Anne Street
City of Fredericksburg Public Works
Fredericksburg, Virginia 22401
Re: Report of Subsurface Exploration and Geotechnical Engineering Analysis
Pedestrian Trail Bridge - Sunshine Park
Fredericksburg, Virginia
Project No. 6707
Mr. Arnin:
Dominion Engineering Associates, Inc. (DEA) is pleased to present this report of subsurface
exploration and geotechnical engineering analysis for tlie above referenced project located at
Sunshine Park in the City of Fredeiicksburg, Virginia. This project was perforined in accordance
witli Dominion Engineering Associates' proposal No. 3332-P dated June 26, 2018.
The following report describes the project characteristics, results of the subsurface exploration,data obtained from the exploration and laboratory services, and our geotechnical evaluations and
recommendations. Soil samples obtained from the study are stored in our Fredericksburg Soils
Laboratory and will be discarded after 60 days unless you request otherwise.
We have enjoyed being of service to the City of Fredeiicksburg during the design phase of this
project. If you should have any questions regarding the information and recoinrnendations
contained in this report, or if we can be of fiirther assistance, please do ngt-li6siUate,tq contact us.
Kevin L. Parris
President
Russell S. Harris Jr., P.E.
Principal Engineer
Attachn'ients: Soil Classification Chart/Reference Notes for Boring Logs
Boring Logs
Boring Location Diagram
S'GEOTECH REPORTS 20l8.6707.iPedesti'ian Biidge
8511 Indian Hills Court, Suite 202 a Fredericksburg, Virginia 22407 * Phone: (540) 710-9339 Fax: (540) 7 10-7449107-A Hanover Avenue * Ashland, Virginia 23005 * (804) 798-8474
Pedestrian Trail Bridge Fredericksburg, Virginia Project No. 6707 Page 1
Dominion Engineering Associates, Inc. (DEA) is pleased to present this report of subsurface exploration and geotechnical engineering analysis for the proposed Pedestrian Trail Bridge in Sunshine Park in Fredericksburg, Virginia. This report presents the findings of our subsurface exploration, evaluations, and recommendations regarding geotechnical-related design and construction considerations for the site. Purpose The purpose of our work was to explore the subsurface conditions in the area of each of the proposed trail bridge abutment foundations. More specifically, a subsurface exploration consisting of a two (2) hand auger borings for the bridge span of 40 ft were performed to acquire information that would allow us to make recommendations for design of bridge abutment foundations. For report purposes, we have assumed that only nominal cut and fill will be required to reach design foundation bearing grades. Our findings of the exploration and recommendations are provided within this report. Drilling Procedures DEA’s fieldwork included a visual site reconnaissance and hand auguring two (2) soil borings at the site. The borings were drilled to depths on the order of five (5) feet below existing grades. The soil borings were performed in the general area of the proposed abutment footings as interpolated from the provided Site Plan prepared by The Kniseley Group. A Boring Location Diagram, depicting the approximate boring locations, is attached to this report. DEA personnel field located borings in the field using pacing and taping techniques referencing existing monuments and the civil engineer's site plans. The civil engineer's plans depict existing and proposed grades and were used to estimate the existing grades at our boring locations, and are documented on the boring logs. Hand auger borings were proposed to be extended to depths of five (5) feet below existing grades. During the boring process in-situ soils bearing capacity was evaluated using a Dynamic Cone Penetrometer (DCP) at each foot within borings. Recommendations herein are based upon the subsurface conditions and the soils encountered at the locations tested. Representative portions of each soil type encountered were collected and brought to DEA’s soil laboratory for further visual observation/classification and laboratory analysis. Hand auger boring logs were prepared based on the notes taken by the field personnel and visual classification and ASTM testing methods within the laboratory of DEA, with final logs including soil classifications. Logs of the hand- auger borings are attached to this report.
Pedestrian Trail Bridge Fredericksburg, Virginia Project No. 6707 Page 2
Proposed Construction Based on the provided information, we understand that improvements at the site will consist of a 10 ft wide by 40 ft long Pedestrian Bridge that will span a small swale. The bridge will be constructed of cold-formed welded square and rectangular tubing with wood decking. The bridge will be supported by abutment footings on either side. Bridge loads provided are 90 psf live load on the full deck area or one 10,000 lb vehicle load. Foundation Recommendations The subsurface conditions encountered in our borings indicate that the onsite soil is suitable to provide support for conventional shallow footings provided ground improvements consisting of removal of soft/loose soils and organics are performed appropriately. DCP test results, per ASTM STP 399, indicate soils have a medium dense and medium stiff consistency using the average blows per increment. Footings supported on natural soils or Engineered Fill over firm natural soils may be designed for a net allowable bearing pressure of 1,500 pounds per square foot (psf). 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. Based on footings designed and constructed herein utilizing a net allowable bearing pressure of 1,500 psf, the total long-term settlements are estimated to be less than one inch with differential settlements between abutments or along equal lengths of abutment foundations walls estimated to be less than half the total settlements. In order to increase the factor of safety against bearing failure, we recommend that footings have minimum width dimensions of 24 inches. Footings should be placed at a minimum depth of 24 inches below finished exterior grades to satisfy bearing capacity and frost depth considerations or deeper if necessary to satisfy scour depths. Scour analysis is not included in our scope of service for this project. The footing embedment depth should provide a horizontal distance from the bottom of the footing to the adjacent slope face of 5 ft. The DEA Geotechnical Engineer or his designated representative should observe the foundation subgrade to verify that conditions exposed at the base of foundation excavations are suitable for the design bearing pressures. It should be noted organic material was encountered in hand auger HA-2 that is considered unsuitable for support of the abutment foundations and will need to be undercut. Hand augers and/or test pits may also be performed within the footing excavation, along with Dynamic Cone Penetrometer (DCP) tests to aid in the evaluation of soil conditions at or below design footing subgrade elevations.
Pedestrian Trail Bridge Fredericksburg, Virginia Project No. 6707 Page 3
Where unsuitable materials such as soft/loose soils are encountered at the base of a foundation excavation, it will be necessary to lower the base of the footing through the unsuitable materials or to undercut the unsuitable soils and restore undercut to design bearing grades with flowable fill, lean concrete, or additional footing concrete as recommended by the geotechnical engineer and described previously. If undercuts are performed due to soft/loose materials and replaced to the bearing elevation with engineered fill instead of concrete, the undercuts should be over-excavated 1 ft wider for each 1 foot of undercut below the design bearing elevation. Exposure to the environment may weaken the soils at the footing bearing levels if the foundation excavations remain open for too long a time. Therefore, foundation concrete should be placed during the same day that excavations are made. If the bearing soils are softened by surface water intrusion or exposure, the softened soils must be removed from the foundation excavations prior to placement of concrete. Re-evaluation of bearing soils should be made by the Geotechnical Engineer when these soils have been subject to softening. Foundations should also be backfilled as soon as possible to reduce water infiltration at/near foundations during construction. Water should not be allowed to pond or collect adjacent to the foundations. Control of surface water and dewatering should be the responsibility of the contractor. Engineered Fill All Engineered Fill should be placed in accordance with this section. Engineered Fill should be placed in horizontal, maximum 8-inch loose lifts and compacted to a minimum of 95% of the maximum dry density as determined in accordance with ASTM Specification D698 (Standard Proctor). The moisture content at the time of placement should be within three percent (3%) of the optimum moisture content, as determined by the appropriate Standard Proctor results. All fill placed on existing slopes shall be benched so that compaction is perpendicular to the ground surface. Benches should extend a minimum of 3 ft horizontal into the existing slope with a new bench constructed not more than 3 ft vertical. Each lift of Engineered Fill should be observed during placement by a representative of the geotechnical engineer for compliance with lift thickness, fill type, and percent compaction. Additionally, a sufficient number of soil density tests should be taken to test the degree of compaction with respect to compaction requirements. We recommend a minimum of at least 2 tests be performed for each lift of fill placed for every 2,500 square feet area. The following fill types are recommended for use on this project:
On-site soils are considered suitable for use as Engineered Fill if they do not contain organic material or debris. CH/MH soil material should not be used as Engineered Fill unless approved by the Geotechnical Engineer.
Pedestrian Trail Bridge Fredericksburg, Virginia Project No. 6707 Page 4
Off-site borrow fill should be limited to granular soil material classified as Sand (SM, SC, SP, SW or better) or VDOT 21A and free of organics and debris. The soils should have less than 35 percent fines (material passing No. 200 sieve) with a liquid limit less than 40 and plastic limit less than 15. CH/MH material should not be used as Engineered Fill unless approved by the Geotechnical Engineer.
General Comments This geotechnical engineering report has been prepared for the City of Fredericksburg to aid in the evaluation of the above referenced site in the City of Fredericksburg, Virginia and to assist the architect, structural engineer and/or civil engineer in the design of this project. The report has been prepared in accordance with generally acceptable geotechnical engineering practices and no other warranties, either expressed or implied, are made. The scope is limited to the specific project and locations described herein and our description of the project represents our understanding of the significant aspects relative to soil and foundation characteristics. Slope stability, and scour analysis were not included in our scope of service for this project. In the event that any changes in the nature or location of the proposed construction or loading outlined in this report are planned, we should be informed so that the changes can be reviewed and the conclusions of this report modified or approved in writing by the geotechnical engineer. It is recommended that all construction operations dealing with earthwork and foundations be reviewed by an experienced geotechnical engineer to provide information as to whether the design requirements are fulfilled in the actual construction. We also welcome the opportunity to provide field construction services for you during construction. The analysis and recommendations submitted in this report are based upon the data obtained from the soil borings and tests performed at the locations as indicated on the Boring Location Diagram and other information referenced in this report. This report does not reflect any variations that may occur between the borings. In the performance of the subsurface exploration, specific information is obtained at specific locations at specific times. However, variations in soil conditions exist on most sites between boring locations and also such situations as groundwater levels vary from time to time. The nature and extent of variations may not become evident until the course of construction. If site conditions vary from those identified during the explorations, the recommendations contained in this report may require revision.
Reference Notes for Boring Logs/Test Pits
I. Drilling and Sampling Symbols:
SS – Split Spoon Sampler RB – Rock Bit Drilling
ST- Shelby Tube Sampler BS – Bulk Sample of Cuttings
RC – Rock Core: NQ, NX, BX, AX PA – Power Auger (no sample)
PM - Pressuremeter HAS – Hollow Stem Auger
DC – Dutch Cone Penetrometer WS – Wash Sample
Standard Penetration (Blows/Ft) refers to the blows per foot of a 140 lb. hammer falling 30 inches on a 2-
inch O.D. split spoon sampler, as specified in ASTM D-1586. The blow count is commonly referred to
as the N-value.
II. Correlation of Penetration Resistances to Soil Properties:
Density of Coarse-Grained Soils Consistency of Fine-Grained Soils
III. Unified Soil Classification Symbols: Reference ASTM D2488
IV Water Level Measurement Symbols:
The water levels are those water levels actually measured at the time of the exploration after cave-in has
occurred (removing auger bits from borehole) in the borehole/test pit exploration indicated by the
symbol. The measurements are relatively reliable when augering, without adding fluids, in granular
soils, but fine grained soils may require several days, or even longer, for the water levels to stabilize.
The position of the ground water table or perched water condition is anticipated to fluctuate depending
on variability in the amount of precipitation, surface runoff, evaporation, and similar factors. To obtain
accurate water level readings, a water observation well would need to be installed to measure the ground
water levels over a period of time, typically this is beyond the scope of services provided by a
geotechnical exploration.
SPT-N
Descriptive
Term
SPT-N
Description of
Consistency
Unconfined
Compressive
Strength, Qp, psf
0 - 4 Very loose < 2 Very soft Less than 250
5 - 10 Loose 2 – 4 Soft 250-500
11 - 30 Medium dense 5 – 8 Medium stiff 500-1000
31 - 50 Dense 9 – 15 Stiff 1000-2000
51 and over Very dense 16 – 30 Very Stiff 2000-4000
31 and greater Hard 4000+
GP Poorly Graded Gravel SC Clayey Sand
GW Well-Graded Gravel ML Low Plasticity Silt
GM Silty Gravel MH High Plasticity Silt
GC Clayey Gravel CL Low Plasticity Clay
SP Poorly Graded Sand CH High Plasticity Clay
SW Well-Graded Sand OL Low Plasticity Organic Soil
SM Silty Sand OH High Plasticity Organic Soil
WL Water Level BCR Before Casing Removal
WS While Sampling ACR After Casing Removal
WD While Drilling WCI Wet Cave In
DCI Dry Cave In
SM
SM
SM
SC
2.4
3.8
4.5
5.0
Loose, Brown Silty Fine to Medium SAND (SM), trace mica and fine gravel, moist
DCP results at 2 feet: 5-4-5
Brown Silty Fine to Coarse SAND (SM), trace mica and fine gravel to medium gravel, moist
Loose to Medium dense, Dark Brown Silty Fine to Coarse SAND (SM), trace mica, very moist
DCP results at 4 feet: 5-5-6Brown Clayey Fine to Coarse SAND (SC), trace mica, wet
Bottom of hole at 5.0 feet.
NOTES
GROUND ELEVATION
LOGGED BY Matthew Kline
DRILLING METHOD Hand Auger AT TIME OF DRILLING Dry
AT END OF DRILLING Dry
AFTER DRILLING Dry
HOLE SIZE 3.25"
DRILLING CONTRACTOR Dominion Engineering Associates GROUND WATER LEVELS:
CHECKED BY Kevin Parris
DATE STARTED 6/27/18 COMPLETED 6/27/18
DE
PT
H(f
t)
0.0
2.5
5.0
SA
MP
LE T
YP
EN
UM
BE
R
PAGE 1 OF 1BORING NUMBER HA-1
CLIENT City of Fredericksburg
PROJECT NUMBER 6707
PROJECT NAME Pedestrian Trail Bridge
PROJECT LOCATION Fredericksburg, Virginia
GE
NE
RA
L B
H /
TP
/ W
ELL
670
7 F
RE
DE
RIC
KS
BU
RG
PE
DE
ST
RIA
N B
RID
GE
.GP
J G
INT
US
LA
B.G
DT
7/9
/18
Dominion Engineering Associates8511 Indian Hill CtFredericksburg VA 22407Telephone: 540-710-9339Fax: 540-710-7449
U.S
.C.S
.
GR
AP
HIC
LOG
MATERIAL DESCRIPTION
SM
Fill
SM
1.4
2.7
5.0
Dark Brown Silty Fine to Coarse SAND (SM), trace organic material, mica and fine gravel, moist
Dark Brown Orgainc Material [Root Fragments and Wood Fragments]
Loose to medium dense, Dark Brown Silty Fine to Medium SAND (SM), trace root fragments, mica and fine to mediumgravel, moist
DCP results at 4 feet: 5-6-8
Bottom of hole at 5.0 feet.
NOTES
GROUND ELEVATION
LOGGED BY Matthew Kline
DRILLING METHOD Hand Auger AT TIME OF DRILLING Dry
AT END OF DRILLING Dry
AFTER DRILLING Dry
HOLE SIZE 3.25"
DRILLING CONTRACTOR Dominion Engineering Associates GROUND WATER LEVELS:
CHECKED BY Kevin Parris
DATE STARTED 6/27/18 COMPLETED 6/27/18
DE
PT
H(f
t)
0.0
2.5
5.0
SA
MP
LE T
YP
EN
UM
BE
R
PAGE 1 OF 1BORING NUMBER HA-2
CLIENT City of Fredericksburg
PROJECT NUMBER 6707
PROJECT NAME Pedestrian Trail Bridge
PROJECT LOCATION Fredericksburg, Virginia
GE
NE
RA
L B
H /
TP
/ W
ELL
670
7 F
RE
DE
RIC
KS
BU
RG
PE
DE
ST
RIA
N B
RID
GE
.GP
J G
INT
US
LA
B.G
DT
7/9
/18
Dominion Engineering Associates8511 Indian Hill CtFredericksburg VA 22407Telephone: 540-710-9339Fax: 540-710-7449
U.S
.C.S
.
GR
AP
HIC
LOG
MATERIAL DESCRIPTION
Not to Scale
Source:
Kniseley Group Inc.
Grading Plan
Boring Location Diagram
Pedestrian Trail Bridge Sunshine Park
Fredericksburg, VA
DEA Project No. 6707
July 5, 2018
HA-1
HA-2