Geotechnical_Report.pdf

Prepared for

Johnson, Mirmiran & Thompson, Inc.

May 24, 2023 (Revised)

Geotechnical Investigation Report

WSSC Beaufort Place Watermain Replacement

WSSC Contract BTBR7260A21

Montgomery County, Maryland

Chantilly, VA

Hampton, VA

Washington, DC

Gaithersburg, MD

7917 Cessna Avenue, Unit L, Gaithersburg, MD 20879 ● www.dmyec.com ● Phone: 301.768.4168 ● Fax: 301.768.4169

GEOTECHNICAL ● CONSTRUCTION ENGINEERING INSPECTION ● SPECIAL INSPECTIONS ● DRILLING ● MATERIALS TESTING ● ENVIRONMENTAL

May 24, 2023 (Revised)

Mr. Steven Pickel, P.E.

Johnson, Mirmiran & Thompson, Inc.

40 Wight Avenue

Hunt Valley, MD 21030

Reference: Geotechnical and Pavement Investigation Report

WSSC Beaufort Place Watermain Replacement

WSSC Contract No. BTBR7260A21

DMY Project No. 03.05572.01

Dear Mr. Pickel, DMY Engineering Consultants Inc. (DMY) is pleased to submit this Geotechnical and Pavement

Investigation Report for the above-referenced project. This report presents a review of the information provided to us, our field exploration and laboratory testing programs, the field and laboratory test results, our interpretation of the subsurface conditions encountered, and our geotechnical recommendations. The study was authorized by you on January 6, 2023, and was conducted generally in accordance with our proposal dated November 17, 2022.

We will store the boring samples for a period of 90 days from the date of this letter. At the end of the holding period, the samples will be discarded unless you request otherwise.

We appreciate the opportunity to be of service to you on this project and would be happy to discuss our findings with you. We look forward to serving as your geotechnical engineer on the remainder of this project and future projects.

Respectfully, DMY ENGINEERING CONSULTANTS INC.

Aiyoub Abbaspour, P.E. Xin Chen, Ph.D., P.E., MBA.

Project Geotechnical Engineer Vice President

WSSC Beaufort Place Watermain Replacement, Montgomery County, Maryland

TABLE OF CONTENTS

1.0 PROJECT OVERVIEW

1.1. PROJECT INFORMATION AND SITE CONDITIONS

1.2. SCOPE OF SERVICES

2.0 FIELD EXPLORATION AND LABORATORY TESTING

2.1. FIELD EXPLORATION

2.2. LABORATORY TESTING

3.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS

3.1. SITE GEOLOGY

3.2. SOIL SURVEY MAP

3.3. SUBSURFACE CONDITIONS

4.0 GEOTECHNICAL EVALUATION AND RECOMMENDATIONS

4.1. GENERAL RECOMMENDATIONS

4.2. SUMMARY OF ESTIMATED SOIL PROPERTIES

4.3. WATERMAIN

4.4. THRUST BLOCK

4.5. UNSUITABLE SOILS

4.6. EXCAVATION CONSIDERATIONS

4.7. BACKFILL PLACEMENT AND COMPACTION CONSIDERATIONS

4.8. DEWATERING CONSIDERATIONS

4.9. MONITORING AND QUALITY ASSURANCE

5.0 LIMITATIONS

APPENDIX A FIGURES

APPENDIX B FIELD OPERATIONS AND RESULTS

APPENDIX C LABORATORY TESTING

1.0 PROJECT OVERVIEW

1.1. PROJECT INFORMATION AND SITE CONDITIONS

The proposed project is located in Silver Spring within Montgomery County, Maryland, and includes

Aylesbury St., Aylesbury Ct., Durant St., Durant Ct., Beaufort Pl., Hopefield Rd., Cradock St., Kings

House Rd., Montford Rd., Montford Ct., and Edgeware St. The proposed project is to replace the existing watermain with the proposed 4-inch, 8-inch, 10-inch and 20-inch diameter Ductile Iron Pipe (DIP) watermains. The Site Location Map (Figure 1 of Appendix A) shows the approximate location of the project. The length of the proposed water main is approximately 13,305.6 linear feet. The proposed watermain will be installed with the open-excavation method and the proposed depth of the watermain is anticipated to be about 4 to 8 ft below the existing ground. Occasionally, watermain will be installed in depths higher than 8 ft to bypass the existing utility lines (stormwater, sewer, or watermain). It is our understanding the thrust blocks will also be installed at watermain reconnection locations. The description of the proposed project given herein is based on the information provided to us by the client. If any of the assumptions or project information is inaccurate, DMY should be informed so that we may revise our geotechnical recommendations, if necessary.

1.2. SCOPE OF SERVICES

The purposes of this study were to obtain the subsurface soil and groundwater information for the proposed project. In accordance with our proposal dated November 17, 2022, our scope of services included the following:

• Review the project information provided to us.

• Perform Standard Penetration Testing (SPT) borings at eighteen (18) locations.

• Collect pavement cores at six (6) locations.

• Conduct laboratory tests on select soil samples.

• Prepare field results including boring logs and pavement core photo logs.

• Prepare this geotechnical and pavement investigation report.

2.0 FIELD EXPLORATION AND LABORATORY TESTING

2.1. FIELD EXPLORATION

Our field exploration consisted of drilling eighteen (18) Standard Penetration Test (SPT) borings (SB-01 through SB-18) and obtaining six (6) pavement cores (PC-01 through PC-06). Except for borings SB-01, SB-08, and SB-14, all other SPT borings were terminated at 15 feet below the existing ground surface.

The SPT borings SB-01, SB-08, and SB-14 were terminated at 4.6, 10.1, and 10.2 feet below the existing ground level, respectively, due to auger refusal. The field exploration was conducted in accordance with

WSSC’s approved Geotechnical and Pavement Investigation Plan dated May 1, 2022. The SPT borings and pavement core locations were selected and approved by JMT and WSSC, and staked out in the field by a DMY field engineer based on the plans provided and existing site conditions (e.g., access, utilities, etc.).

The SPT borings were drilled using truck-mounted CME-45 drill rigs (3.25-inch hollow-stem auger with split spoon sampler) per ASTM D1586. Groundwater levels were measured at each boring location during drilling and upon drilling completion. Upon completion of the field exploration, all SPT borings were backfilled with auger cuttings. For borings drilled in the paved area, the boreholes were patched with

Aquaphalt (cold asphalt mixture). The Boring Location Plan, field exploration procedures, boring logs, and pavement core photo logs are included in Appendices A and B. Following field operations, the soil samples were transported to our laboratory for further review and testing. The samples will be stored in our laboratory for a period of 90 days from the submittal date of this report. After this period, the samples will be discarded unless we are instructed otherwise.

2.2. LABORATORY TESTING

Representative soil samples were selected and tested in the laboratory to verify field identification and to determine pertinent engineering properties. The laboratory testing results are included in Appendix C of this report. The laboratory testing program included the following:

• Natural Moisture Content (ASTM D2216) 25 Tests

• Grain Size Analysis (ASTM D6913) 25 Tests

• Atterberg Limits (ASTM D4318) 25 Tests

• Modified Proctor (ASTM D1557) 10 Tests

3.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS

3.1. SITE GEOLOGY

According to the Physiographic Map of Maryland (2008)1, the project sites are located in the Hampstead

Upland District of the Harford Plateaus and Gorges Region within the Upland Section of Piedmont

Physiographic Province. Based on the USGS National Geologic Map Database2 of Montgomery County, the geological structure of the site consists of Lower Cambrian and/or Neoproterozoic era Coarse-grained quartz schists (Loch Raven Schist) and fine- to medium-grained mafic schists (Piney Run, Pleasant

Grove, and Prettyboy Formations). Schist is a foliated, slivery gray rock consisting of interlocking plates of mica or chlorite and minor amounts of common rock-forming minerals. It is commonly interbedded with schistose gneiss (a type of rock containing quartz and feldspar) and impure quartzite in beds ranging from a few inches to tens of feet.

1 MGS Physiographic Map of Maryland (http://www.mgs.md.gov/geology/physiographic_map.html) 2 USGS National Geologic Map Database (https://ngmdb.usgs.gov/Prodesc/proddesc_45814.htm) http://www.mgs.md.gov/geology/physiographic_map.html https://ngmdb.usgs.gov/Prodesc/proddesc_45814.htm

3.2. SOIL SURVEY MAP

According to the Natural Resources Conservation Service Web Soil Survey (NRCS)3 of Montgomery

County (included in Appendix A), the surficial soils in the project area dominantly consist of Gaila and

Glenelg silt loam units (1C, 2B, and 2C) which include silty loam, clay loam, sandy clay loam, sandy loam, loamy sand, and Channery fine sandy loam.

Minor soil units in the site include the following:

o 5A - Glenville silt loam consisting of silt loam, Channery silt loam, and loam.

o 6A - Baile silt loam consisting of silt loam, silty clay loam, and loam.

3.3. SUBSURFACE CONDITIONS

The subsurface conditions encountered at the locations explored are shown in the boring logs in

Appendix B. The records represent our interpretation of the subsurface conditions in accordance with generally accepted geotechnical engineering practice. The lines designating the interfaces between various strata on the boring logs are approximate, as the actual transitions between soil strata are often gradual. In the absence of foreign substances, it is difficult to distinguish between natural soils and fill materials. Although individual test borings are representative of the subsurface conditions at the boring locations on the dates shown, they are not necessarily indicative of the subsurface conditions at other locations or at other times. Below is a summary of subsurface conditions encountered during our field exploration:

Surficial Materials

Asphalt pavement was encountered in all of the borings and pavement cores to be placed over natural or fill material. The pavement thicknesses encountered were summarized in Table 1. It should be noted that pavement core debonding was observed at pavement core location PC-05 as indicated in the

Pavement Core Photo Log (Appendix B). Graded Aggregate Base (GAB) underlying asphalt pavement with a thickness of approximately 6 inches was only observed in pavement core location PC-01.

Stratum I, Existing Fill (FILL & POSSIBLE FILL)

Immediately beneath the surficial materials, existing fill materials were encountered extending to depths of 0 to 7.5 feet below the existing site grades. The existing fill materials were identified/classified as firm to stiff Sandy ELASTIC SILT (MH), soft to firm Sandy SILT (ML), loose CLAYEY SAND (SC), and loose to medium-dense SILTY SAND (SM). At this time, we have considered that the existing fill on site is uncontrolled fill.

3 USDA Natural Resources Conservation Service (https://websoilsurvey.sc.egov.usda.gov/App/ WebSoilSurvey.aspx) https://websoilsurvey.sc.egov.usda.gov/App/%20WebSoilSurvey.aspx https://websoilsurvey.sc.egov.usda.gov/App/%20WebSoilSurvey.aspx

Table 1. Pavement Thickness Summary

Soil Boring or

Pavement Core ID Street Name

AC1

Thickness

(inches)

PCC2

Thickness

(inches)

GAB3

Thickness

(inches)

PC-01 Aylesbury St. 4.5 - 6.0

PC-02 Beaufort Pl. 6.25 - -

PC-03 Durant St. 5.5 - -

PC-04 Hopefield Rd. 6.0 - -

PC-05 Cradock St. 4.5 - -

PC-06 Kings House Rd. 8.0

SB-01 Aylesbury St. 8 - -

SB-02 Aylesbury St. 7 - -

SB-03 Aylesbury St. 7 - -

SB-04 Aylesbury St. 7 - -

SB-05 Durant St. 6 - -

SB-06 Durant St. 6 - -

SB-07 Beaufort Pl. 6 - -

SB-08 Hopefield Rd. 7 - -

SB-09 Hopefield Rd. 7 - -

SB-10 Montford Rd. 7 - -

SB-11 Cradock St. 6

SB-12 Cradock St. 8 - -

SB-13 Kings House Rd. 8 - -

SB-14 Kings House Rd. 8 - -

SB-15 Edgeware St. 6 - -

SB-16 Kings House Rd. 8 - -

SB-17 Kings House Rd. 6 - -

SB-18 Durant Ct. 6 - -

Notes: 1. AC – Asphalt Concrete

2. PCC – Portland Cement Concrete

3. GAB – Graded Aggregate Base

Stratum II, Residual Soils (RESIDUAL)

Underlying the existing surficial and fill materials, residual soils were encountered at this location that extended to depths of 6.5 to 9.0 feet below the existing site grades at boring locations SB-08 and SB-14, respectively, and to the boring termination depth at other locations. The encountered soil types in this stratum include very soft to very hard Sandy ELASTIC SILT (MH) and loose to very dense SILTY SAND

(SM).

Stratum III, Decomposed Rock (DECOMPOSED ROCK)

Beneath the residual stratum, decomposed rock was encountered at boring locations SB-08 and SB-14 that extended to the boring termination depths at 10.1 and 10.2 feet below the existing site grade, respectively. Decomposed Rock, also called Intermediate Geo-Materials (IGM), is an intermediate material between soil and rock derived from the weathering of the in-place natural rock. The material is classified as very dense SILTY SAND (SM).

Groundwater

Groundwater was encountered at boring locations SB-09, SB-13, SB-14, and SB-15 at depths of 9 to 11 feet below the existing surface level during the drilling and upon completion of drilling. Groundwater was not encountered at other boring locations during and/or upon completion of drilling. Cave-in depths were measured at boring locations upon completion of the drilling and noted on the boring logs. The cave-in depths may be a possible indication of the groundwater table. Due to public safety concerns, we backfilled the borehole immediately after drilling. As a result, we did not obtain 24-hour groundwater readings. It should be noted that due to backfilling of borings upon completion, groundwater may not have had time to enter the borings or reach its hydrostatic level. Groundwater may still be present at the locations and/or depths not indicated from the borings since 24-hour groundwater readings were not obtained. It should also be noted that fluctuations in groundwater level and perched water may occur due to in-situ soil types, seasonal variations, rainfall, surface runoff, evaporation, construction activity, and other site-specific factors that do not present at the time of drilling.

4.0 GEOTECHNICAL EVALUATION AND RECOMMENDATIONS

4.1. GENERAL RECOMMENDATIONS

The construction should be performed in accordance with WSSC Standard Specifications and

Montgomery County Specifications for Utility Construction Permit – Construction Specifications. Debris, stumps, vegetation, root systems, topsoil, and organic materials should be removed from the construction area. Any existing structures within the areas to be developed should be either protected or removed prior to the initiation of new construction depending on the structure types which shall be determined by the Owner. We suggest that all available information regarding the existing utilities at the site be reviewed before construction. Removal should include all existing pavements, underground pipes, utilities, and underground structures that might interfere with the new construction. If abandoned underground utilities are to be removed prior to the initiation of construction, provisions should be made in the construction specifications.

4.2. SUMMARY OF ESTIMATED SOIL PROPERTIES

It is our understanding that the proposed depth of the watermain and thrust blocks will be, in general, about 4.0 to 8.0 feet below existing grades but occasionally, the watermain depth increases to bypass the existing utility lines. Mainly, the depth of the watermain at Hopefield Rd near boring location SB-09 and Cradock St near boring location SB-12 is about 10 to 11 ft. Table 2 shows a summary of estimated soil properties from the results of SPT and laboratory tests. The soil properties were estimated based on our experience and published references including FHWA-IF-02-034 Geotechnical Engineering Circular

No. 5 Evaluation of Soil and Rock Properties. It should be noted that although individual test borings are representative of the subsurface conditions at the boring locations on the dates shown, they are not necessarily indicative of the subsurface conditions at other locations or at other times.

Table 2. Summary of Estimated Soil Properties

Location Soil

Stratum

USCS

Classification

Range of N-

Value

(blows per foot)

Range of

Effective Unit

Weight (pcf)

Range of

Friction

Angle, Φ

(deg.)

Friction Angle b/n Soil and

DIP, δ (deg.)

SB-01

(4’ to 7.5’) Fill SM 3 to 7 95 to 105 27 to 30

SB-02

(4’ to 8’) Residual SM 10 to 12 110 to 115 28 to 32

SB-03

(4’ to 8’) Residual SM 6 to 7 100 to 105 28 to 30

SB-04

(4’ to 8’) Residual SM/MH 12 to 17 110 to 115 30 to 32

SB-05

(4’ to 8’) Residual SM 5 to 7 100 to 105 28 to 30

SB-06

(4’ to 8’) Residual SM 6 to 8 100 to 105 28 to 30

SB-07

(4’ to 8’) Residual SM 7 to 9 105 to 110 28 to 30

SB-08

(4’ to 8’) Residual SM 14 to 17 110 to 115 30 to 32

SB-09

(4’ to 10’) Residual SM 9 to 19 105 to 120 30 to 34

SB-10

(4’ to 8’) Residual SM 7 to 9 105 to 110 28 to 30

SB-11

(4’ to 8’) Residual SM 8 to 9 105 to 110 28 to 30

SB-12

(4’ to 11’) Fill/Residual SM 7 to 14 105 to 115 28 to 32

SB-13

(4’ to 8’) Residual SM 1 to 2 95 to 100 25 to 28

SB-14

(4’ to 8’) Residual SM 6 to 24 100 to 120 28 to 34

SB-15

(4’ to 8’) Residual MH 12 to 16 110 to 115 30 to 32

SB-16

(4’ to 8’) Residual SM 21 to 42 120 to 130 32 to 38

SB-17

(4’ to 8’) Fill/Residual SM 6 to 7 100 to 105 28 to 30

SB-18

(4’ to 8’) Residual SM 8 to 21 105 to 120 28 to 32

Note: * DIP - Ductile Iron Pipe

4.3. WATERMAIN

It is anticipated that most of the materials along the proposed watermain alignment will provide adequate support for the pipe; however, some very loose or soft materials were encountered during our field investigation which should be considered unsuitable materials. The excavation subgrade area should be prepared prior to the installation of the water main and checked for suitability by means of proof-rolling or dynamic cone penetration (DCP) test. Proof rolling of subgrade should be performed with 1 or 2 passes with a static roller or include a DCP test to check the subgrade. It is recommended to place a layer of 1.5 to 2 feet of No. 57 stone over geotextile filter fabric when loose or soft material is encountered. Any soft, loose, or unsuitable material should be removed to a firm bottom, to the extent directed by the

Geotechnical Engineer, then inspected and probed to verify the suitability prior to replacement with

Borrow Aggregate as per WSSC Standard Specifications Section 02315 – Earthwork for Pipeline

Construction.

4.4. THRUST BLOCK

We understand that concrete thrust blocks will be constructed at each site. The design of thrust blocks shall be performed in accordance with WSSC Pipeline Design Manual Part Three, Section 27 – Thrust

Restraint Design for Buried Piping. Based on the results of the subsurface exploration, we recommend an allowable vertical soil bearing capacity of 1,500 pounds per square foot (psf) be used for the thrust block design. Resistance to lateral forces can be assumed to be provided by friction at the base of thrust blocks and by passive earth pressure. For level ground conditions, a passive earth pressure of 220 psf per foot of depth may be used for the sides of the concrete thrust block placed against the compacted backfill soils to compute allowable thrust block resistance. A passive earth pressure of 100 psf per foot of depth may be used for soils below groundwater level if encountered. The maximum value of the passive earth pressure should be limited to 1,000 psf for compacted backfill. Due to the low overburden stress of the soil at shallow depth, the upper 2.5 feet of passive resistance should be neglected and should be taken as frost depth unless the soil is confined by pavement or slab. A coefficient of friction of

0.30 may be used between the concrete thrust block and the supporting undisturbed natural soil. A coefficient of friction of 0.50 may be used between the concrete thrust block and the compacted gravel backfill materials. The excavation subgrade area should be inspected and verified for bearing capacity with a Dynamic Cone Penetrometer (DCP) or similar methods by a Professional Engineer licensed in the

State of Maryland or field staff supervised by a Professional Engineer licensed in the State of Maryland.

Any soft, loose, or unsuitable material should be removed to a firm bottom, to the extent directed by the

Geotechnical Engineer.

4.5. UNSUITABLE SOILS

Unsuitable soils including highly plastic soils (e.g., ELASTIC SILT) were encountered during our subsurface exploration as shown in the attached boring logs (Appendix B). Highly plastic soils can exhibit significant shrinkage and/or swelling due to changes in moisture content and should not be used as structural fill if encountered during construction. If highly plastic soils are encountered near or above the foundation bearing level, backfilling with gravels and sands such as GW, GP, SW, and SP is not recommended as this would create a reservoir condition that could saturate the highly plastic soils.

4.6. EXCAVATION CONSIDERATIONS

We understand that the construction of the proposed water mains may use open excavation with backfill.

The anticipated depths of the proposed water mains will be about 4.0 to 8.0 feet below the existing ground but occasionally, the watermain depth increases to 10± feet below the existing ground in order to bypass the existing utility lines. Based on our field exploration, very hard materials (SPT N values greater than

60 blows per foot) were encountered at two locations (borings SB-08 and SB-14) at depths of 6.5 to 10.2 feet below existing grades. Materials with blow counts in excess of 60 blows per foot may have rock-like qualities and should be anticipated to be difficult to excavate or require rock excavation methods for removal and may be encountered at other locations between borings. We recommend that the contractor should anticipate and provide appropriate measures for potential hard materials or objects (e.g. rock, etc.).

The excavations should be sloped per OSHA requirements. For excavations deeper than 4 feet or in areas where sloping is not possible due to site constraints or any other reason(s), temporary support of excavation should be required and performed in accordance with WSSC Specification Section 02315

Part 3. Lateral earth pressures and hydrostatic pressures for the design of the excavation support systems should be based on soil and groundwater conditions and should include loading due to construction traffic, roadway traffic, and adjacent structures. Stockpiles should NOT be kept near the excavation area to avoid surcharging.

The Contractor should submit working drawings and calculations for the design of the temporary excavation support systems signed and sealed by the Contractor’s Professional Engineer licensed to practice in the State of Maryland. The working drawings and calculations should be submitted to the

Engineer for review. The Contractor should be entirely responsible for the design and adequacy of the temporary excavation support systems.

Residual soils with relatively high fine contents were encountered within the proposed pipe invert elevation. Residual soils are derived from weathering and decomposition of the underlying bedrock.

Residual soils are typically prone to disturbance with significant strength degradation if exposed to prolonged moisture conditions and construction traffic. Also due to the potential mica content, such soils are difficult to place and compact if reused as backfill materials. We recommend that the Contractor provide appropriate drainage measures including water controls during excavation and stockpiling of on-site soils to minimize disturbance and strength loss.

4.7. BACKFILL PLACEMENT AND COMPACTION CONSIDERATIONS

General Trench Backfill materials should be suitable materials classified as GW, GP, SW, SP, GM, GC, GW-GC, SP-SM, SM, SC, SW, ML, or CL. High plasticity fine-grained soils classified as MH or CH and organic soils classified as OL, OH, and PT should be classified as unsuitable and should be removed from the site. GW, GP, SW, and SP should not be placed over highly plastic clays. GW-GC, GM, GC, SP-SM, SM, SC, SW, ML, or CL with at least 35% fines may be used as suitable backfill material over highly plastic clays. Based on the subsurface conditions observed in our exploration, the majority of the onsite natural soils except Fill materials may be re-used as General Trench Backfill. The backfill and compaction for meter vault construction should be performed in accordance with WSSC Standard

Specifications Section 02315 – Earthwork for Pipeline Construction and Montgomery County

Specifications for Utility Construction Permit – Construction Specifications.

4.8. DEWATERING CONSIDERATIONS

Groundwater was encountered at boring locations SB-09, SB-13, SB-14, and SB-15 at depths of 9 to 11 feet below the existing surface level during our subsurface exploration. The observed groundwater levels are below the anticipated depth of the proposed watermain. However, groundwater may still be present at the locations and/or depths not indicated from the borings since 24-hour groundwater readings were not obtained due to public safety concerns. It should be noted that fluctuations in the groundwater level and perched water conditions can occur seasonally due to variations in precipitation, surface runoff, construction activity, and other site-specific factors. The contractor should be prepared to deal with groundwater during construction. The sites should be sufficiently dewatered to construct the proposed meter vault. The actual extent of the dewatering system will need to be determined at the time the excavation is performed.

Due to the relatively high fines content for soils encountered, on-site soils may be susceptible to disturbance and softening when exposed to moisture and construction equipment. Construction areas should be kept free of water and in a relatively dry condition to minimize disturbance of the exposed subgrade soil. Positive drainage and dewatering measures should be used to control surficial water and groundwater to adequate depths below the subgrade levels. Run-off from adjacent areas should be diverted away from the excavation to prevent ponding of water in the excavation.

4.9. MONITORING AND QUALITY ASSURANCE

The construction shall be performed, inspected, and tested per WSSC Specification Section 02315. We recommend a full-time inspector under the supervision of a geotechnical engineer should be on-site during the construction. Deviations, either from specifications or good construction practices, should be brought to the attention of the concerned authority, along with appropriate recommendations. Before field operations begin, a representative sample of each proposed backfill material should be collected and tested to determine its Atterberg Limits, gradation, maximum dry density, optimum moisture content, and natural moisture content. The test results will be used to evaluate the suitability of each proposed backfill for quality control purposes during fill placement.

5.0 LIMITATIONS

The recommendations provided are based in part on project information provided to us and are only applicable to the specific project and site discussed in this report. If the project information section in this report contains incorrect information or if additional information is available, DMY should be contacted to review our recommendations. We can then modify our recommendations for the proposed project.

Regardless of the thoroughness of a subsurface investigation, there is always a possibility that subsurface conditions may vary from those documented during a subsurface exploration at specific locations. In addition, the construction process itself may alter subsurface conditions. Therefore, experienced geotechnical personnel should be engaged to observe and document the construction procedures used and the conditions encountered. Unanticipated conditions and inadequate procedures should be reported to the design team along with timely recommendations. We recommend that DMY be retained to provide this service based upon our familiarity with the project, the subsurface conditions, and the intent of the recommendations.

We have prepared this report for use by the design professionals for design purposes in accordance with generally accepted geotechnical engineering practices. No other warranty, expressed or implied, is made as to the professional advice included in this report.

APPENDIX A FIGURES

United States Department of Agriculture

A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants

Custom Soil Resource Report for

Montgomery County, Maryland

Natural Resources Conservation Service

March 13, 2023

Preface Soil surveys contain information that affects land use planning in survey areas.

They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers.

Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment.

Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions.

The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations.

Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?

cid=nrcs142p2_053951).

Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations.

The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey.

Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ https://offices.sc.egov.usda.gov/locator/app?agency=nrcs http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

Contents Preface How Soil Surveys Are Made Soil Map

Soil Map Legend Map Unit Legend Map Unit Descriptions

Montgomery County, Maryland 1C—Gaila silt loam, 8 to 15 percent slopes 2B—Glenelg silt loam, 3 to 8 percent slopes 2C—Glenelg silt loam, 8 to 15 percent slopes 5A—Glenville silt loam, somewhat poorly drained, 0 to 3 percent slopes...16 6A—Baile silt loam, 0 to 3 percent slopes

References Glossary

How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity.

Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA.

The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape.

Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries.

Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units).

Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research.

The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas.

Soil scientists make many field observations in the process of producing a soil map.

The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded.

These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape.

Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties.

While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management.

Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil.

Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date.

After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and

Custom Soil Resource Report identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately.

Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit.

Soil Map

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39° 6' 44'' N

8'

6' ' W

39° 6' 44'' N

7'

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39° 6' 11'' N

8'

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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 300 600 1200 1800

Feet 0 100 200 400 600

Meters Map Scale: 1:7,040 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI) Area of Interest (AOI)

Soils Soil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point Features Blowout

Borrow Pit

Clay Spot

Closed Depression

Gravel Pit

Gravelly Spot

Landfill

Lava Flow

Marsh or swamp

Mine or Quarry

Miscellaneous Water

Perennial Water

Rock Outcrop

Saline Spot

Sandy Spot

Severely Eroded Spot

Sinkhole

Slide or Slip

Sodic Spot

Spoil Area

Stony Spot

Very Stony Spot

Wet Spot

Other

Special Line Features

Water Features Streams and Canals

Transportation Rails

Interstate Highways

US Routes

Major Roads

Local Roads

Background Aerial Photography

The soil surveys that comprise your AOI were mapped at 1:15,800.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation Service Web Soil Survey URL:

Coordinate System: Web Mercator (EPSG:3857)

Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: Montgomery County, Maryland Survey Area Data: Version 18, Sep 14, 2022

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: May 20, 2021—Jun 18, 2021

The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

1C Gaila silt loam, 8 to 15 percent slopes

20.3 14.9%

2B Glenelg silt loam, 3 to 8 percent slopes

103.7 76.0%

2C Glenelg silt loam, 8 to 15 percent slopes

2.0 1.5%

5A Glenville silt loam, somewhat poorly drained, 0 to 3 percent slopes

10.0 7.3%

6A Baile silt loam, 0 to 3 percent slopes

0.5 0.3%

Totals for Area of Interest 136.4 100.0%

Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit.

A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class.

Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils.

Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape.

The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas.

An identifying symbol precedes the map unit name in the map unit descriptions.

Each description includes general facts about the unit and gives important soil properties and qualities.

Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement.

Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.

Some map units are made up of two or more major soils or miscellaneous areas.

These map units are complexes, associations, or undifferentiated groups.

A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps.

The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.

An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.

An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.

Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example.

1C—Gaila silt loam, 8 to 15 percent slopes

Map Unit Setting National map unit symbol: kx7n Elevation: 100 to 2,000 feet Mean annual precipitation: 35 to 50 inches Mean annual air temperature: 45 to 57 degrees F Frost-free period: 120 to 255 days Farmland classification: Farmland of statewide importance

Map Unit Composition Gaila and similar soils: 95 percent Minor components: 5 percent Estimates are based on observations, descriptions, and transects of the mapunit.

Description of Gaila

Typical profile H1 - 0 to 8 inches: silt loam H2 - 8 to 17 inches: sandy clay loam H3 - 17 to 20 inches: sandy loam H4 - 20 to 76 inches: loamy sand

Properties and qualities Slope: 8 to 15 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high

(0.57 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water supply, 0 to 60 inches: Moderate (about 7.4 inches)

Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Ecological site: F148XY024PA - Moist, Piedmont - felsic, Upland, Mixed Oak -

Hardwood - Conifer Forest Hydric soil rating: No

Minor Components

Baile Percent of map unit: 5 percent Landform: Flats Hydric soil rating: Yes

2B—Glenelg silt loam, 3 to 8 percent slopes

Map Unit Setting National map unit symbol: 2v7gr Elevation: 30 to 1,200 feet Mean annual precipitation: 40 to 55 inches Mean annual air temperature: 48 to 57 degrees F Frost-free period: 150 to…