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ECS MID-A: LANTIC, LLC Geotechnical- Const uction Materials - Environmental· Facilities
Deeember 13, 2006
Mr. Duane Gleason� Kaz Brothers, LLC� 2139 Bille Knob Terrace Silver Spring, Maryland 20906
ECS Job No. 12915
Reference:� Report of Subs Tface Exploration and Geotechnical Engineering ..l\nalysis, West Church Road, oudoun County, Virginia
Dear Mr. Gleason:
As authorized by your acceptan e of our Proposal No. 26125-GP, dated October 26, 2006, ReS Mid-Atlanlte, LLC (ECS) has ecently completed the subsurface exploration and geotechnical engineering analysis for the ab ve refereneed projeet in Loudoun County, Virginia. A report, including the results of our s bsurface exploration, boring logs, laboratory test information, engineering recommendations, and a Boring Location Diagram, are enclosed with this letter. The recommendations presente in this report are intended for use by your office and hy other design professionals involved with the design and implementation of this project described herein.
As we understand, the site is c rrently undeveloped and is relatively clear of existing vegetation. Below the existing topsoil enc untered on site, the borings encountered fill materials as well as natural soils which included 10 plasticity residual clays and silt, largely underlain by sands and weathered rock material. Lao er soil zones were encountered within the natural soil profile in several of the borings. This v nation is characteristic of these soils and is largely due to local weathering variations, as well s a variation in moisture content and residual mineral bonding. General1y. the density of the so Is increased with depth, and tcnded to also become more granular and exhibit characteristics oft underlying parent bedrock.
High plasticity and potentiall expansive soils are known to exist in these geologies. These materials have severe restricti ns with regard to their use as engineered fill and will require undercutting a minimum of 2 et in pavement areas and under building slabs. In addition, and as required by Loudoun Count we recommend that in the footing areas, these materials be lowered to bear at a minimum depth of 4 feet below the final exterior grades or to the bottom of the expansive soil layer, which ver is less.
14026 Thunderbolt Place, Suire 100, Chan illy, VA 201.51 • (703) 471-8400 • FAX (703) 834-5527 • www.ecslimited.com� Aberdeen. MD· Baitimore. MD· Cha~tilJy. VA· Charlottesville, VA* , Frederick, MD· Frederkhburg, VA . Manassas, VA . Ocean City, MD-�
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Kaz Brothers ECSJobNo.129IS November 30, 2006 Page 2
At the time of our exploration, undwater was eneountered within five of the twelve borings reeently drilled on-site. Ground ater in these locations was encountered at depths ranging from approximately 3.5 ± feet to 13.5 feet below the existing ground surface. Groundwater levels at the site should be expected to v based on seasons, or with ehanges in weather and/or loeal drainage patterns.
In summary, the subject site is considered suitable for the proposed development, which will include retail facilities, as well as a fast food restaurant and bank facility, parking areas and associated utility infrastructure. Foundations for the proposed struetures may be suppolted on shallow spread footing founda 'ons founded on suitable natural soils, or on engineered fill oYerlying suitable natural soils. Footings founded on finn natural soils with an SPT N-value of at least 10 blows per foot (bpf) or engineered fill may be designed using a net allowable soil bearing pressure of 3,000 poun per square foot (psi). If higher bearing pressures are required, extension of the footings into th very stiffar dense natural soils or weathered siltstone roek may increase the soil bearing pressu to 6,000 psf. Natural soils with 8PT N-values on the order of 18 bpf or greater are considere suitable for support of the 6,000 psf design bearing pressure. For the most part, the local req irements for frost penetration will govern the depth at which the footings are designed to bear. owever, in areas where the highly plastie soils are encountered, special handling of these soils a dJar undercutting will be neeessary to reduce the risk of damage caused by shrinking and swellin ofthcse soils.
The enclosed report provides further recommendations on foundation design pressures and settlement estimates, placement and eompaction of fill materials, retaining wall construction. and other factors that wiUlikely in uence construction at the site. We have enjoyed the opportunity to be of service to Kaz Brother, LLC on this project. If you have any questions concerning the information or recommendatio s included in this report or we may be of further assistance in the planning andlor execution of si development, please do not hesitate to contact us.
ECS Mill-ATLANTIC, LLC.
Risa F. Scott, E.LT A. Shellon, P. E. Assistant Projeet Engineer cipal Engineer
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Subsurface Exploration and Geotechnical Engineering Analysis
West Church Road Loudoun County, Virginia
Kaz Brothers, LLC 2139 Blue Knob Terrace
Silver Spring, Maryland 20906
PROJECT # 12915
DATE December 13, 2006
TABLE OF CONTENTS�
PAGE PROJECT OVERVIEW
Introduction 1� Proposed Construction 1� Scope of Work 1� Purposes of Exploration 2�
Subsurface Exploration Procedures 3� Laboratory Testing Program 3�
Site Conditions 4� Regional Geology 4� Soil Conditions 5� Groundwater Observations 5�
ANALYSIS AND RECOMMENDATIONS
Subgrade Preparation and Earthwork Operations 7� Fill Placement 7� Siltstone Considerations 8� Rock Excavation and Blasting Operations 9� Building Foundations II� Floor Slab Design 12� Exterior Pavements 13� Utility Installation 15� Temporary and Permanent Slopes 16� Seismie Design Considerations 16� Construetion Considerations 16� Closing 17�
This report presents the results of our subsurface exploration and engineering recommendations for the proposed West Church Road retail center, which is located on West Church Road, east of the intersection of West Church Road and Cascades Parkway. The site lies between two existing stroctures with the stOTIDwater management pond bordering the west of the site, a newly constructed residential community to the north and a veterinary clinic to the east. The approximate location of the site is indicated on the Vicinity Map located on the Boring Location Diagram. which is included in the Appendix of this report.
Based on the site plan that you provided to us, as well conversations with you, we understand that retail and office facilities, a fast food restaurant and bank will be constructed, as well as at- grade asphalt parking areas and associated utility infrastructure, Based on the plan provided to us, approximately 26,400 square feet of commercial development will be constructed for this project. We anticipate that all facilities will likely be of wood frame construction. Based on the proposed finished floor elevation for the faeilities, as well as the relatively flat-lying nature ofthe subject site, we anticipate minimal cut-and-fill operations will be required to reach final design grades.
The description of the proposed projeet is based on the infonnation provided to us by your office and plans provided to us by the site civil engineer, If any of this infonnation is inaccurate, either due to our misunderstanding or either design changes that may oecur later. we recommend that we be contacted in order to provide or alternate reeommendations that may be warranted.
Scope of Work
The conclusions and reeommendations are based on a total oftwelve borings (B-1 through B-12) that were reeently completed in November, 2006. The boring locations were staked in the field by representatives of ECS utilizing Global Positioning System (GPS) equipment, which is capable of establishing horizontal locations with sub-meter accuracy. The ground surfaee elevations noted on the attached boring logs were interpolated from the site plan provided by Bowman Consulting, which gives elevation contours at 2.0 feet intervals. The soil borings were extended to depths on the order of 2.7± feet to 18.8± feet below the existing ground surfaee. to auger refusal depths in either stockpiled materials or weathered rock.
Following driHing operations, laboratory tests were performed on selected soil samples to identify the soils. and to assist in the determination of the properties of the site soils. The results of the subsurface exploration along with Boring Location Diagram are included within the Appendix of this report.
ECS Job No. 12915� -2-
Purposes of Exploration
The purposes of this exploration were to explore the soH and groundwater conditions (if present) at the site and to develop engineering recommendations to guide design and construction of the project. We accomplished these purposes by:
I.� driJIing borings to explore the subsurface soil and groundwater condition