GEOTECHNICAL INVESTIGATION PROPOSED WATERMAIN REPLACEMENT ... · PDF filerecently completed at the above noted project site. ... underlain by a till deposit. ... for reuse subject

GEOTECHNICAL INVESTIGATION PROPOSED WATERMAIN REPLACEMENT ON MARY STREET AND CHARLES STREET TOWN OF BLUE MOUNTAINS, ONTARIO for GREENLAND CONSULTING ENGINEERS PETO MacCALLUM LTD. 19 CHURCHILL DRIVE BARRIE, ONTARIO L4N 8Z5 PHONE: (705) 734-3900 FAX: (705) 734-9911 EMAIL: [email protected] Distribution: PML Ref.: 16BF018 2 cc: Greenland Consulting Engineers (+email) Report: 1 1 cc: PML Barrie May 2016

May 26, 2016 PML Ref.: 16BF018 Report: 1 Mr. Brad Parker Greenland Consulting Engineers 120 Hume Street Collingwood, Ontario L9Y 1V5 Dear Mr. Parker Geotechnical Investigation Proposed Watermain Replacement on Mary Street and Charles Street Town of Blue Mountains, Ontario

Peto MacCallum Ltd. (PML) is pleased to present the results of the geotechnical investigation

recently completed at the above noted project site. Authorization for the work described in this

report was provided by Mr. J. Hartman, in the signed Engineering Service Agreement dated

April 4, 2016, and in the Engineering Services Agreement Change Order No. 1, dated

April 29, 2016, to be returned.

The Town of Blue Mountains is proposing to replace about 450 m of watermain and service

laterals along Mary Street and Charles Street in Clarksburg. The new watermain will comprise

150 mm diameter PVC pipe and will be installed with an invert of approximately 2.0 m below

existing road grade. A small creek crosses Mary Street and the watermain invert will drop to

4.5 to 5.0 m below road grade, about 2.0 m below the creek. The portion of the watermain below

the creek will be installed with trenchless methods, so the creek is not disturbed. Once the

underground works have been completed, the roadway will be restored over the watermain

trench.

The purpose of this investigation was to explore the subsurface soil and ground water conditions

along the alignment, and based on this information, provide comments and geotechnical

engineering recommendations for utility installation and pavement design.

Geoenvironmental assessment of the site was not within the terms of reference, and no work has

been carried out in this regard.

19 Churchill Drive, Barrie, Ontario L4N 8Z5 Tel: (705) 734-3900 Fax: (705) 734-9911

E-mail: [email protected] BARRIE, HAMILTON, KITCHENER, TORONTO

Proposed Watermain Replacement on Mary Street and Charles Street, Town of Blue Mountains, Ontario PML Ref.: 16BF018, Report: 1 May 26, 2016, Page 2

The comments and recommendations provided in this report are based on the site conditions at

the time of the investigation, and are applicable only to the proposed works as described in the

report. Any changes in plans, will require review by PML to assess the applicability of the report,

and may require modified recommendations, additional analysis and/or investigation.

INVESTIGATION PROCEDURES

The initial investigation program was to have PML attend the site to witness and log test pits,

during a test dig conducted by the Town of the Blue Mountains, in an attempt to find the existing

watermain. This occurred on April 20, 2016. During the test dig, only one test pit (Test Pit 1) was

excavated (to 1.8 m depth), however the watermain was not found.

Subsequently, the existing watermain was located by the Town with a vacuum truck (PML was

not on-site). Boreholes were requested and it was also revealed to PML that a portion of the new

watermain would need to be installed beneath the creek on Mary Street by trenchless methods.

The field work for the boreholes was carried out on May 11, 2016 and consisted of three

boreholes. Borehole 1 was advanced to 6.4 m depth near the creek on Mary Street and

Boreholes 2 and 3 were advanced to 4.3 m in other areas of the watermain alignment.

Test pit and borehole locations are shown on Drawing 1.

The test pit was advanced by a rubber track backhoe under the direction of the

Town of Blue Mountains staff. The boreholes were advanced using continuous flight solid stem

augers, powered by a truck mounted CME-75 drill rig, equipped with an automatic hammer,

supplied and operated by a specialist drilling contractor, working under the full-time supervision of

a member of our engineering staff.

The pavement component thicknesses encountered in the boreholes were measured and

samples of the granular material collected. Representative samples of the underlying subgrade

soils were recovered at frequent depth intervals for identification purposes using a conventional

split spoon sampler. Standard penetration tests were carried out simultaneously with the


sampling operations to assess the strength characteristics of the subsoil. Ground water

conditions were closely monitored during the course of the field work.

The location of the test pit was established in the field by the Client. The location of each

borehole was established in the field by PML, cognizant of underground utility locates.

Surface elevations of the test pit and boreholes were established relative to a Temporary Bench

Mark (TBM), as shown on Drawing 1, and described as follows:

TBM: Top of Iron Bar at Southeast Corner of Mary Street and Charles Street Intersection Elevation 199.23 (metric, geodetic)

Traffic control was provided by PML in accordance with the Ontario Traffic Manual, Book 7. Test

pits were backfilled with excavated soils. All boreholes were backfilled and capped with cold mix

asphalt.

All recovered samples were returned to our laboratory for moisture content determination and

detailed examination to confirm field classification. Grain size analyses were carried out on four

samples of existing subgrade materials. Associated Atterberg limits testing was carried out on

one of these samples. The results are presented on Figures 1 to 4, attached.

SUMMARIZED SUBSURFACE CONDITIONS

Reference is made to the appended Log of Test Pit sheet for details of the subsurface conditions

observed in the open test pit. Reference is made to the appended Log of Borehole sheets for

details of the subsurface conditions, including soil classifications, pavement thicknesses, inferred

stratigraphy, Standard Penetration N values, ground water observations and the results of

laboratory water content determinations.

The test pit and boreholes revealed pavement or topsoil underlain by fill, over a major silt unit,

locally, underlain by a till deposit. A description of the distribution of the subsurface conditions is

presented below.


Topsoil

At the surface of Test Pit 1, a 400 mm layer of silt topsoil was encountered.

Pavement

The table below summarizes the pavement structure encountered in the boreholes:

BOREHOLE SURFACE

TREATMENT (mm)

GRANULAR BASE (mm)

GRANULAR SUBBASE

(mm)

TOTAL THICKNESS

(mm) Mary Street

1 20 110 200 330 2 20 100 110 230

Charles Street 3 20 150 180 350

Fill

Below the pavement structure or topsoil, fill was encountered in the test pit and in all boreholes to

depths of 1.5 to 2.4 m (elevation 196.7 to 197.9). The fill comprised sandy silt to sand, some silt

to sand and gravel. Three samples of the material from the boreholes were submitted for grain

size analysis and the results are presented on Figures 1 to 3, attached. The fill was moist to wet.

Moisture contents ranged from 5 to 22%.

Silt

A native silt unit was encountered below the fill in in all boreholes and in the test pit. The layer

extended to the 1.8 m depth of excavation in Test Pit 1, and carried to the 4.3 m depth of drilling

in Boreholes 2 and 3. In Borehole 1, the unit was penetrated at 5.5 m (elevation 193.3). The unit

contained trace sand and trace clay. A sample of the silt was submitted for a grain size analysis

and the results are presented on Figure 4, attached. Atterberg limits testing showed the material

was non-plastic. The unit was typically compact, locally loose or dense, with

Standard Penetration N Values (N values – blows per 300 mm of penetration of the split spoon

sampler) of 7 to 32. Moisture contents were 18 to 25%, with the material being very moist to wet.


Till

A till deposit was found below the silt in Borehole 1, extending to the 6.4 m depth of investigation.

The till comprised silty sand, with trace gravel. Cobbles and boulders were noted. The till was

very dense with moisture contents of about 9% (moist).

Ground Water

In Test Pit 1, minor seepage was noted at 1.2 m depth (elevation 198.2), however there was no

sidewall sloughing and the infiltration rate was quite slow.

Upon completion of augering, water was observed in all the boreholes at 0.8 to 1.4 m depth

(elevation 198.0 to 198.4).

Based on the above, in conjunction with the moisture content profile, it is believed that the ground

water is perched within the fill above the silt layer, with the silt layer also being wet. The creek

base at about elevation 196.0 (about 3.0 m below the road grade) and the water was about

100 mm deep at the time of our field work.

Ground water levels will fluctuate seasonally and in response to variations in precipitation.

GEOTECHNICAL ENGINEERING CONSIDERATIONS

General

The Town of Blue Mountains is proposing to replace about 450 m of watermain and service

laterals along Mary Street and Charles Street in Clarksburg. The new watermain will comprise

150 mm diameter PVC pipe and will be installed with an invert of approximately 2.0 m below

existing road grade. A small creek crosses Mary Street and the watermain invert will drop to

4.5 to 5.0 m below road grade, about 2.0 m below the creek. The portion of the watermain below

the creek will be installed with trenchless methods, so the creek is not disturbed. Once the

underground works have been completed, the roadway will be restored over the watermain

trench.


The test pit and boreholes revealed topsoil or pavement, over fill and a major silt unit, locally

underlain by a till deposit. Ground water was encountered at 0.8 to 1.4 m depth (about elevation

198.0 to 198.4) in the test pit and the boreholes.

Site Servicing

The proposed watermain will have an invert of 2.0 m below the road grade, locally deeper under

the creek (4.5 to 5.0 m) where trenchless methods are proposed for installation.

Trench Excavation and Ground Water Control

Trench excavation and ground water control for the watermain is discussed in

Excavation and Ground Water Control later in the report.

Pipe Bedding

Based on the boreholes, the subgrade at invert levels (about 2.0 m depth throughout the

alignment) is expected to comprise a thin fill layer over native silt. Where fill or other deleterious

materials are encountered at invert level, such fill should be sub-excavated and replaced with

increased bedding thickness, subject to geotechnical field review.

Standard granular bedding, in accordance with OPSS compacted to 95% Standard Proctor

maximum dry density should be satisfactory. For flexible pipes, bedding and cover material

should comprise OPSS Granular A. For rigid pipes, the bedding material should comprise

OPSS Granular A and cover material may comprise select native soil free of oversized material.

Trench Backfill

Trench backfill should be compacted to 95% Standard Proctor maximum dry density in 200 mm

thick lifts. Backfill for at least the upper 1 m of trench should be close to optimum moisture

content to prevent subgrade instability issues.

In general, excavated materials from above the ground water table are expected to be acceptable

for reuse subject to exclusion of deleterious content/organics, and geotechnical review and


approval during construction. Material from below the ground water table will have to be dried out

or mixed with drier soil to render the material suitable.

Earthworks operations should be inspected by PML to approve materials, placement and

compaction efforts and ensure the specified degree of compaction is achieved throughout.

Trenchless Watermain Installation

It is understood that the watermain will be installed beneath the existing creek crossing on

Mary Street with an invert at 4.5 to 5.0 m depth (about elevation 194.0) some 2.0 m below the

creek bed. In this regard, Horizontal Directional Drilling (HDD) is recommended, subject to the

commentary below.

Based on Borehole 1 on Mary Street, the operation will encounter compact to loose silt and be

below the creek and groundwater levels. It is noted that a very dense till deposit was contacted

below the silt and may be contacted during the operation. Cobbles and boulders were

encountered in the till and will represent possible obstacles to the trenchless operations.

It is assumed that HDD operations will be carried out from the surface and no sending-receiving

pits are required.

HDD installations should be carried out in accordance with OPSS 450,

Construction Specifications for Pipeline and Utility Installation in Soil by Horizontal Directional

Drilling.

A monitoring program to measure the vertical ground movements is recommended.

Consideration should be given to a monitoring program that follows the plan outlined in MTO’s

Guidelines for Foundation Engineering – Tunnelling Specialty for Encroachment Permit

Application, including a series of monitoring points, daily measurements, and review level and

alert levels of movement where a specific plan of action is in place for these levels of movement.


Excavation and Ground Water Control

Considering bedding thickness and potential fill removal, excavation for the watermain will extend

to about 2.5 m below the present road levels. In this regard, excavation will be carried out

through the existing pavement, fill, and into the underlying silt. Excavation within these materials

should be straightforward, and may be carried out using conventional equipment.

All construction work must be carried out in accordance with the requirements of the

Occupational Health and Safety Act (OHSA). The site soils are considered as Type 3 soil

requiring side walls to be constructed at no steeper than one horizontal to one vertical (1H:1V)

from the base of the excavation.

Ground water was observed below 0.8 to 1.4 m depth in all boreholes; however it was noted that

the ground water seepage volume in the open test pit was manageable. In this regard,

conventional sump pumping should suffice to control ground water seepage and surface water

run-off in most excavations.

Water taking in Ontario is governed by the Ontario Water Resources Act (OWRA) and the

Water Takings and Transfer Regulation O. Reg. 387/04. Section 34 of the OWRA requires

anyone taking more than 50,000 L/d to obtain a Permit to Take Water (PTTW) from the

Ministry of the Environment and Climate Change (MOECC). This requirement applies to all

withdrawals, whether for consumption, temporary construction dewatering, or permanent drainage

improvements. In April of this year the MOECC made some changes to the PTTW requirements.

Projects such as this, where creek diversion is required and/or if it assessed that less than

400,000 L/d of ground water will be taken, the Owner can apply for a permit online via the

Environmental Activity and Sector Registry (EASR) system. It is understood that under the EASR

a permit/permission to proceed, might be granted in less time than the typical three months for a

Category 3 PTTW.

Based on our current understanding of these recent changes, this project might qualify for the

new EASR system registry. Once design details are finalized the project should be reviewed to

confirm the MOECC requirements for a PTTW.


Pavement Design and Construction

The pavement along Mary Street and Charles Street will be restored over the watermain trench

once the installation is complete. It is understood that the intent is to utilize a similar or slightly

thicker pavement structure than the existing pavement to minimize frost related distress:

MATERIAL THICKNESS (mm)

Surface Treatment 20

Granular A Base Course 150

Granular B Type I Subbase Course 200

Total Thickness 370

Following rough grading, subgrade preparation should include proofrolling the exposed subgrade

to minimum 95% Standard Proctor maximum dry density. Any unstable zones identified during

this process should be sub-excavated and replaced with compacted material to establish uniform

subgrade support conditions, subject to geotechnical field review.

It is understood the surface treatment (tar and chip) will be installed after the watermain

construction is complete, with a slurry seal to be provided over the entire roadway surface in

2017.

Imported material for the granular base and subbase should conform to OPSS gradation

specification for Granular A and Granular B, and should be compacted to 100% Standard Proctor

maximum dry density.


Geotechnical Review and Construction Inspection and Testing

It is recommended that the project design drawings be submitted to PML for geotechnical review

for compatibility with site subsurface conditions and the recommendations contained in this report.

Earthworks operations should be carried out with review by PML to approve subgrade

preparation, backfill materials, placement and compaction procedures and check the specified

degree of compaction is achieved throughout fill materials.

The comments and recommendations provided in the report are based on the information

revealed in the boreholes. Conditions away from and between boreholes may vary, particularly in

view of service trenches and previous earthworks activities at the site, which may necessitate

modifications to the recommendations contained in the report.

LIST OF ABBREVIATIONS

PENETRATION RESISTANCE

Standard Penetration Resistance N: - The number of blows required to advance a standard split spoon sampler 0.3 m into the subsoil. Driven by means of a 63.5 kg hammer falling freely a distance of 0.76 m. Dynamic Penetration Resistance: - The number of blows required to advance a 51 mm, 60 degree cone, fitted to the end of drill rods, 0.3 m into the subsoil. The driving energy being 475 J per blow.

DESCRIPTION OF SOIL

The consistency of cohesive soils and the relative density or denseness of cohesionless soils are described in the following terms:

CONSISTENCY N (blows/0.3 m) c (kPa) DENSENESS N (blows/0.3 m)

Very Soft 0 - 2 0 - 12 Very Loose 0 - 4 Soft 2 - 4 12 - 25 Loose 4 - 10 Firm 4 - 8 25 - 50 Compact 10 - 30 Stiff 8 - 15 50 - 100 Dense 30 - 50 Very Stiff 15 - 30 100 - 200 Very Dense > 50 Hard > 30 > 200 WTPL Wetter Than Plastic Limit APL About Plastic Limit DTPL Drier Than Plastic Limit

TYPE OF SAMPLE

SS Split Spoon TW Thinwall Open WS Washed Sample TP Thinwall Piston SB Scraper Bucket Sample OS Oesterberg Sample AS Auger Sample FS Foil Sample CS Chunk Sample RC Rock Core ST Slotted Tube Sample

PH Sample Advanced Hydraulically PM Sample Advanced Manually

SOIL TESTS

Qu Unconfined Compression LV Laboratory Vane Q Undrained Triaxial FV Field Vane Qcu Consolidated Undrained Triaxial C Consolidation Qd Drained Triaxial

PML-GEO-508A Rev. 2004-01

Documents

GEOTECHNICAL INVESTIGATION PROPOSED WATERMAIN REPLACEMENT ... · PDF filerecently completed at the above noted project site. ... underlain by a till deposit. ... for reuse subject