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Article 25 - MA03104 Old Shepard St Dam Canton Design Report - Signed
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REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
AKA SHEPARD STREET DAM
CANTON, MASSACHUSETTS
State Dam ID#: 6-11-50-2
NID ID#: MA03104
Owner: Town of Canton
Owner Type: Municipal
SA Project No. 052-15-022, January 12, 2018
Prepared for:
TOWN OF CANTON, MASSACHUSETTS
801 Washington Street
Canton, Massachusetts
(781) 821-5063
Prepared by:
Stephens Associates Consulting Engineers, LLC
DN: cn=Robert S.
Stephens, Principal
Engineer, o=Stephens
Associates Consulting
Engineers, LLC,
email=RSStephens@S
tephensEngineers.com
, c=US
Date: 2018.01.14
17:37:54 -05'00'
Nathaniel A. Olson, Ph.D, P.E. James E. Turner, P.E. Robert S. Stephens, P.E.
Project Engineer Project Manager Principal EngineerSource page 2
SUMMARY
This Report summarizes design of repairs to Old Shepard Street Dam (Dam, Project, or Site) by Stephens
Associates Consulting Engineers, LLC (SA) for the Town of Canton, Massachusetts (Town, Client, Owner, you,
your, etc.). The purpose of this Report is to describe the basis for design of repairs to the Dam in support of a
Massachusetts Department of Conservation and Recreation, Office of Dam Safety (MA DCR ODS) Chapter 253
Permit Application (Permit Application).
Old Shepard Street Dam impounds Silk Mill Pond, aka Third Pond, aka Third Mill Pond, aka Messinger Pond,
in Canton, Massachusetts, and the crest carries Old Shepard Street along the northern portion of the pond, over
Massapoag Brook. The Dam releases through the spillway into Massapoag Brook. The impoundment has a
second release; a diversion channel near the pond inlet that bypasses the Dam and continues under Messinger
Street, ultimately leading to Bolivar Pond,. The Dam is classified as Small size, Significant hazard. The Dam’s
current use is for recreation, however, it was previously used for mill power in the 1800s. A portion of the Dam
was destroyed in a 1955 flood, and the current spillway and bridge were constructed about 1956. Significant
deficiencies and concerns include:
• Concrete deterioration on the Spillway abutments and piers;
• Inadequate hydraulic capacity to pass the Spillway Design Flood (SDF, the 100-year flood) with stoplogs
in-place, resulting in Dam overtopping;
• The embankment is not designed for overtopping;
• Tree and brush clearing is needed; and
• Stoplogs are leaking and deteriorated.
The concrete deterioration is categorized as a structural deficiency by ODS, resulting in “Poor Condition” rating
by prescribed evaluation criteria, and requiring repair. Additionally, Dam overtopping in the SDF increases risk
of failure due to erosion. The Project will repair the Dam. Goals of the repairs include:
• Improve the Dam’s condition to better than “Poor” under ODS prescriptive criteria;
• Reduce risk of Dam failure and associated upstream and downstream impacts;
• Address deficiencies and requirements of the Regulations (302 CMR 10);
• Maintain typical historical pool elevations; and
• Manage initial repair and longer-term maintenance cash outlay (total cost to the Town).
The Project generally includes the repairs/improvements described below and illustrated by the attached
Drawings, to meet the goals listed above:
• Replace spillway concrete piers, left abutment, and portion of right abutment;
• Provide overtopping erosion resistance by rip-rap, downstream revetment, re-paving crest, and downstream
stone masonry wall repairs;
• Remove trees and brush;
• Repair upstream rip-rap;
• Replace/repair fences and other metal components, replace stoplogs, etc.
SA performed two subsurface explorations (borings), cored concrete at the spillway piers and abutments,
performed a dewatered visual inspection of the spillway, performed geotechnical and concrete laboratory testing,
and evaluated spillway concrete. Results are summarized as follows:
SA No. 052-15-022 1/12/2018 Page i of iiSource page 3
• Subsurface conditions generally consisted of 12 ft. of dense to very loose fill overlying dense to very dense
silty sand and gravel, with occasional boulders.
• Visual inspection of dewatered spillway indicated significant deterioration of the left abutment over its full
height, but deterioration of piers and right abutment was generally noted to be above the water line.
• Concrete laboratory testing the existing piers and right abutment indicated degradation primarily due to
moderate alkali silica reaction (ASR).
• In our opinion, concrete deterioration at the left abutment likely resulted from cyclic freezing and thawing,
and from use of inferior quality concrete compared to that used for the piers and right abutment. In our
opinion, the cracking and efflorescence of the piers and right abutment likely resulted from a combination
of factors, but predominately ASR and possibly cyclic freezing and thawing because degradation is
significantly worse above the water line.
• SA structural evaluation of piers indicated reinforcing of the existing piers to be inadequate to resist current
design ice and water loads.
• SA concluded to replace the left abutment and piers above the base slab and to replace the top of the right
abutment about El. 111.5 (about 2 ft. below normal pool).
SA evaluated hydrology and hydraulics (H&H) and designed repairs to resist erosion from overtopping.
According to the Regulations, the spillway design flood (SDF) for existing Small Size, Significant Hazard Dams
is the flood resulting from the 100-year storm (Q100 or 100-year flood). The H&H results indicated that the Dam
overtops by about 0.8 ft. in the 100-year flood with stoplogs in place. Removing stoplogs in anticipation of
flooding may lower the impoundment elevation during the 100-year flood and avoid overtopping the Dam,
however, flow through the Dam would increase (more water would be diverted to the Dam instead of the
diversion channel), increasing downstream flooding along Massapoag Brook. The Town therefore typically
maintains the stoplogs in place during normal flows and floods.
During conceptual design of repairs, SA considered potential, limited (in scale) modifications to the Dam to
attempt to mitigate overtopping in the 100-year flood and potentially reduce downstream flooding on Massapoag
Brook. We conceptualized that the Town could maintain the existing hydraulic configuration and provide
erosion resistance to overtopping, but found no other, limited/minor (in scale) physical modifications that would
alleviate overtopping in the 100-year flood. The Town concluded to design and construct overtopping erosion
resistance instead of potential, significant hydraulic modifications that could alleviate overtopping, but might
also adversely impact properties around the impoundment and/or downstream. SA designed repairs to resist
erosion from overtopping, including repaving the crest (Old Shepard Street), constructing a concrete cap on the
downstream stone masonry wall with stone revetment at the downstream wall base, and adding rip-rap in a low
area on the left downstream side of the embankment.
SA evaluated stability of the spillway, embankment upstream slope and downstream stone masonry wall using
force-equilibrium (i.e. overturning and sliding) or slope stability methods, as appropriate, under the load cases
stipulated by Regulations. Results indicated that the existing spillway, embankment upstream slope and
embankment downstream stone masonry retaining wall meet the factors of safety stipulated by the Regulations.
SA has prepared Design Drawings and Specifications for the Dam repairs, submitted separately but attached by
reference as Appendix D. An Operations and Maintenance Manual is attached in Appendix C. SA is applying
for permits including MassDEP Notice of Intent, US Army Corps of Engineers Self-Verification Permit, and a
Town of Canton Application for Soil Erosion and Sediment Control Plan Certification and Land Disturbance
Permit.
The full text of this Report should be read and understood. This Report is subject to the limitations presented
herein, including Figures, Tables and Appendices.
SA No. 052-15-022 1/12/2018 Page ii of iiSource page 4
REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
CANTON, MASSACHUSETTS
1. INTRODUCTION........................................................................................................................... 1
1.1 Purpose and Scope of Services ............................................................................................................. 1
1.2 Site Location and Description .............................................................................................................. 2
1.3 Project Understanding and Background ............................................................................................... 3
1.4 Project Goals and Description .............................................................................................................. 4
2. SUBSURFACE INFORMATION AND SPILLWAY CONCRETE EVALUATION ............. 4
2.1 Available Geologic Data....................................................................................................................... 4
2.2 Previous Subsurface Information ......................................................................................................... 5
2.3 Subsurface Explorations ....................................................................................................................... 5
2.4 Subsurface Conditions .......................................................................................................................... 5
2.5 Groundwater Observations ................................................................................................................... 6
2.6 Geotechnical Laboratory Testing and Permeability ............................................................................. 6
2.7 Spillway Concrete Testing and Evaluation........................................................................................... 7
3. HYDROLOGY AND HYDRAULICS .......................................................................................... 8
3.1 Summary and Conclusion ..................................................................................................................... 8
3.2 Summary of Previous Hydrologic Evaluation ...................................................................................... 9
3.3 Summary of Previous Hydraulic Evaluation ........................................................................................ 9
4. SEEPAGE AND STABILITY, AND STRUCTURAL DESIGN .............................................. 11
4.1 Model Geometry ................................................................................................................................. 11
4.1.1 Embankment Model Cross-Section .......................................................................................... 11
4.1.2 Spillway Model ......................................................................................................................... 11
4.1.3 Ice Loads ................................................................................................................................... 11
4.2 Seepage Evaluation............................................................................................................................. 12
4.3 Stability Evaluation ............................................................................................................................ 12
4.4 Structural Design ................................................................................................................................ 12
5. IMPLEMENTATION OF REPAIRS AND IMPROVEMENTS ............................................. 13
5.1 Project Schedule, Water Diversion and Observation.......................................................................... 13
5.2 Borrow Materials and Reuse of On-Site Materials............................................................................. 13
5.3 Operation and Maintenance (O&M) Manual...................................................................................... 13
5.4 Emergency Action Plan (EAP) ........................................................................................................... 13
5.5 Permitting ........................................................................................................................................... 14
6. EXCAVATIONS, LIMITATIONS AND REFERENCES ........................................................ 14
6.1 Excavations......................................................................................................................................... 14
6.1.1 Excavations and Slopes ............................................................................................................ 14
6.1.2 Important Note on Soil Variability ........................................................................................... 15
6.1.3 Temporary Shoring ................................................................................................................... 15
6.2 Limitations .......................................................................................................................................... 15
6.3 References and Previous Reports ....................................................................................................... 16
SA No. 052-15-022 1/12/2018 Page TOC-1Source page 5
REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
CANTON, MASSACHUSETTS
Attachments:
Figure 1 – Site Location Map
Figure 2 – Site Aerial Photograph
Figure 3 – Excerpt of MassGIS Parcel Map
Figure 4 – Representative Photographs
Figure 5 – Exploration Location Sketch
Figure 6 – Model Embankment Section
Figure 7 – Drainage Area
Table 1 – Impoundment and Groundwater Observations
Table 2 – Summary of Geotechnical Laboratory Test Results
Appendix A – 1956 Plans, Exploration Logs, Geotechnical Laboratory Test Results and Concrete Laboratory
Test Results
Appendix B – Seepage and Stability Evaluation
Appendix C – Operation and Maintenance (O&M) Manual
Appendix D – Design Drawings and Technical Specifications (Submitted separately, attached by reference)
SA No. 052-15-022 1/12/2018 Page TOC-2Source page 6
1. INTRODUCTION
This Report summarizes design of repairs to Old Shepard Street Dam (Dam, Project, or Site) by Stephens
Associates Consulting Engineers, LLC (SA) for the Town of Canton, Massachusetts (Town, Client, Owner, you,
your, etc.). The purpose of this Report is to describe the basis for design of repairs to the Dam. The design of
repairs and this Report are being submitted to the Massachusetts Department of Conservation and Recreation,
Office of Dam Safety (DCR ODS) for Chapter 253 Dam Safety Permit Application.
This Report is subject to the limitations presented herein, including Figures, Tables and Appendices. SA
performed these services for Town in general accordance with our Agreement dated October 1, 2015, authorized
October 2, 2015.
The Project is described below. Section 2 summarizes subsurface conditions and evaluation of the existing
spillway concrete. Section 3 summarizes previous hydrology and hydraulics information and Section 4 describes
stability evaluation, as well as considerations of surficial erosion under Dam overtopping flows. Section 5
summarizes additional information required for the Chapter 253 Permit Application and Section 6 presents
excavation information, limitations of this Report not stated elsewhere, and references.
1.1 Purpose and Scope of Services
The purposes of SA’s services were to design repairs to Old Shepard Street Dam and prepare and submit permit
applications on behalf of the Town. Our scope of services included the following:
• Preliminary evaluation of hydraulic alternatives;
• Dewatered visual inspection;
• Base plan preparation;
• Wetland delineation;
• Spillway concrete coring, laboratory testing, and evaluation;
• Subsurface explorations and geotechnical laboratory testing;
• Seepage and stability evaluation;
• 30-, 60-, 90- and 100-percent design;
• Construction contract and specifications;
• Construction cost estimate;
• Final Design Report, including Operation and Maintenance Plan
• Permitting, including MA DCR ODS Chapter 253 Dam Safety Permit, MassDEP Wetlands Permit, USACE
Self-Verification Permit; Canton Land Disturbance Permit
Except as expressly stated herein, SA’s scope of services did not include an environmental assessment or
evaluation of any kind, including but not limited to assessments or evaluations for the presence or absence of
wetlands or hazardous or toxic materials or organisms (e.g., fungi, flora, fauna, microorganisms, etc.) in the soil,
surface water, groundwater, or air, on or below or around this Site. Any observations of odors, colors, or unusual
or suspicious items or conditions made by SA are incidental to our services, and any statements regarding such
observations are for the Client and strictly for the information.
SA No. 052-15-022 1/12/2018 Page 1 of 17Source page 7
1.2 Site Location and Description Dam engineering and construction convention refer to right and left facing downstream as used herein. Elevations, unless otherwise stipulated, refer to NAVD 1929 Old Shepard Street Dam is located on Old Shepard Street, on the order of 700 ft. northeast of its intersection with Washington Street in Canton, MA. Figure 1 – Site Location Map, Figure 2 – Site Aerial Photograph, and Figure 3 –Excerpt of MassGIS Parcel Map show the Dam location. Figure 4 shows representative photographs. The Dam forms the northern border of Silk Mill Pond (aka Third Pond, Third Mill Pond, and Messinger Pond) and the crest carries Old Shepard Street over Massapoag Brook. The Dam releases through the spillway into Massapoag Brook. The impoundment has a second release consisting of a diversion channel near the inlet on the south side of the Pond that continues under Messinger Street, ultimately leading to Bolivar Pond. The Dam consists of an earth and retained-earth embankment with a concrete spillway located near the middle of the embankment. The ends of the embankment daylight into the natural ground surface at either end such that the beginning of the embankment is not easily distinguished from natural ground. Thus, the Dam height varies from zero at either end to about 11 ft. at the Spillway. SA estimated the Dam length as about 450 ft. based on our estimate of where the embankment elevation meets a similar elevation of adjacent ground. Old Shepard Street forms the Dam crest, following the embankment and crossing a single-span bridge just downstream of, and integral to, the Spillway. The Dam crest consists of bituminous pavement of Old Shepard Street with a concrete strip about 4 ft. wide extending along the top edge of the rip-rap that forms the upstream dam face. The upstream face consists of a rip-rap-covered embankment, sloping into the impoundment. The 1956 Plans indicated that there is an upstream retaining wall between the rip-rap and the embankment. Based on discussion with Town personnel, we understand the retaining wall was stone masonry and was covered by the dumped rip- rap. The downstream face consists of concrete retaining walls extending about 14 and 29 ft. right and left, respectively, (looking downstream) from the spillway/bridge opening. A dry-stone masonry retaining wall extends about 123 ft. right of the concrete wall right of the spillway/bridge. A shallow embankment and residential driveways are located left of the concrete wall left of the spillway/bridge. The Spillway consists of a three-opening concrete structure with abutments integral to the downstream bridge abutments. Two concrete piers create three openings about 6.6 ft. wide each, which hold stop logs. The 1956 Plans (F.G. Keyes 1956) show that the bridge and spillway are reinforced concrete with a sheet pile cutoff extending beneath the upstream side of the spillway from the bottom of footings (El. 101 ft.) to El. 91 ft. We note that the 1956 Plans are labeled “Issued for Construction,” and therefore may not be indicative of as-built conditions. Although Massapoag Brook (“Brook”) enters Silk Mill Pond and flows through the Spillway, during normal flows, a significant volume of the Brook bypasses Silk Mill Pond in a diversion channel separated from the Pond’s south end by an earth embankment (berm), and flows through a culvert under Messinger Street near the Pond’s southeast corner (refer to Figure 2). Additionally, a boulder-lined section of the berm, about 1-2 ft. lower than the surrounding berm, allows flow from the Pond back to the diversion channel, essentially increasing flow to the diversion channel when the impoundment is above normal pool. The earth berm, including boulder lined section, forms an auxiliary outlet for the Pond (hereinafter referred to as “auxiliary outlet”). During periods of high water, the Pond elevation likely exceeds the berm elevation and the diversion channel and Pond would be one water body upstream of both the Dam and the Messenger Street Culvert. In this situation, the culvert under Messinger Street would become an auxiliary outlet. SA No. 052-15-022 1/12/2018 Page 2 of 17
Source page 8
The Dam’s current use is for recreation, but with development downstream it also is purported to provide some
flood control, particularly in smaller (i.e. higher frequency) floods. Local residents told SA that the Pond is
frequently used for ice skating. Based on our review of historical documentation, mills at the Site were active
from about 1797 to 1903, and a portion of the dam was destroyed in a 1955 flood. The current spillway and
bridge were constructed in 1956, as shown on the 1956 Plans and date stamp in the bridge concrete. Our
previous reports, letters, and inspections cited below describe the Site, history of the Dam, background and
existing conditions in further detail.
The following elevations are summarized for reference in comparison to information described elsewhere in this
Report. Elevations refer to NGVD 1929.
• Existing embankment crest: Varies, about 116.0 ft. at bridge, low point El. 115.7 ft. left of bridge,
gradually increases to about El. 118 ft. at left end of embankment;
• Existing top of spillway: El. 116.8 ft. (top of spillway piers and abutments);
• Existing top of stoplogs: Varies El. 113.1 to 113.7 ft.;
• Channel at toe of spillway: El. 105.1 ft.
1.3 Project Understanding and Background
As described in our Agreement, our understanding of the Project, as presented herein, is based on relevant
information cited in our previous services for the Dam, and on the following:
• SA’s Phase I Inspection and Evaluation Reports dated July 20, 2007 and September 14, 2012 (2007 and
2012 Phase I Reports, respectively);
• SA’s Emergency Action Plan (EAP) for the Dam, dated June 20, 2012;
• Previous plans of spillway and bridge titled, “The Proposed 1955 Flood Bridge, Canton, Sheppard St. at
Third Mill Pond, Bridge No. C-2-20, Issued for Construction” prepared by Fenton G Keyes Associates for
the Massachusetts Department of Public Works, dated February 18, 1956, 3 sheets (1956 Plans), obtained
by SA from MassDOT on January 28, 2016 and attached in Appendix A;
• Our telephone discussions, meetings, and email correspondence with Mr. Michael Trotta, Town DPW
Superintendent, and Mr. James Donovan, PE, Town Engineer, between October 2015 and present;
Old Shepard Street Dam is classified by DCR ODS as Small Size, Significant Hazard under 302 CMR 10
(Regulations, February 10, 2017). It is in Poor Condition, as described in our 2012 Phase I Report. Significant
deficiencies and concerns include:
• Concrete deterioration on the Spillway abutments and piers;
• Inadequate hydraulic capacity to pass the Spillway Design Flood (SDF, the 100-year flood) with stoplogs
in-place, resulting in Dam overtopping and inundation of Old Shepard Street;
• Significant tree and brush clearing is needed; and
• Stoplogs are leaking and deteriorated.
The concrete deterioration is categorized as a structural deficiency by ODS, resulting in “Poor Condition” rating
by prescribed evaluation criteria, and requiring repair. Additionally, Dam overtopping in the SDF increases risk
of failure due to erosion because the Dam was not designed for overtopping.
SA No. 052-15-022 1/12/2018 Page 3 of 17Source page 9
As part of 30 percent design, SA conceptualized alternatives to address the inadequate hydraulic capacity and
overtopping, and consulted with the Town. The Town decided to repair the embankment crest, and design it to
resist erosion during overtopping in the SDF. Refer to Section 3 for additional details.
1.4 Project Goals and Description
The Project will repair the Dam. Goals of the repairs include:
• Improve the Dam’s condition to better than “Poor” under ODS prescriptive criteria;
• Reduce risk of Dam failure and associated upstream and downstream impacts;
• Address deficiencies and requirements of the Regulations (302 CMR 10);
• Maintain typical historical pool elevations; and
• Manage initial repair and longer-term maintenance cash outlay (total cost to the Town).
The Project generally includes the repairs/improvements described below and illustrated by the attached
Drawings, to meet the goals listed above:
• Replace spillway concrete piers, left abutment, and portion of right abutment;
• Provide overtopping erosion resistance by rip-rap, downstream revetment, re-paving crest, and downstream
stone masonry wall repairs;
• Remove trees and brush;
• Repair upstream rip-rap;
• Replace/repair fences and other metal components, replace stoplogs, etc.
2. SUBSURFACE INFORMATION AND SPILLWAY CONCRETE EVALUATION
2.1 Available Geologic Data
SA reviewed readily-available geologic information in our files and on line (e.g. from USGS, NRCS). In the
Site vicinity, the information generally indicates various soils of discontinuous extent overlying glacially
deposited soils, and overlying bedrock consisting of Dedham Granodiorite. Details are as follows.
The Surficial Geologic Map (Chute 1966b) shows soils in the Dam vicinity as “ground moraine,” described as,
“Chiefly till. Occurs as blanket over most of quadrangle. Thin where bedrock outcrops are abundant, thick where
bedrock outcrops are scarce. Probably underlies other surficial deposits in many places.”
In the vicinity of the Dam spillway and the embankment right of the spillway, and downstream along Massapoag
Brook, the NRCS Web Soil Survey (NRCS 2016) indicates Scarboro and Birdsall soils. Scarboro soils are
described as typically consisting of 9 in. thick “mucky fine sandy loam” overlying 51-in. thick “stratified loamy
fine sand to gravelly coarse sand”, derived from “loose sandy glaciofluvial deposits.” It describes Birdsall soils
as typically consisting of 16-in. thick “very fine sandy loam” overlying 44-in. thick “silt loam,” derived from
soft, coarse-silty glaciolacustrine deposits. Left of the spillway, the Web Soil Survey indicates Canton-Urban
Land Complex. Urban land is described as excavated and filled land, and Canton soils are described as typically
consisting of 18 in. “fine sandy loam” overlying 42 in. “gravelly loamy sand,” derived from “friable coarse-
loamy eolian deposits over loose sandy and gravelly ablation till.”
SA No. 052-15-022 1/12/2018 Page 4 of 17Source page 10
Bedrock geologic information (Chute 1966a) indicates Site bedrock consists of Dedham Granodiorite, described
as “Coarse-grained light-gray granite and quartz monzonite containing microperthite, oligoclase, quartz, and a
small amount of chloritized biotite.” Depth to bedrock is not indicated.
2.2 Previous Subsurface Information
The 1956 Plans show two borings, drilled in 1955 near the left spillway/bridge abutment prior to the 1956 bridge
construction. Logs of these borings indicate loose sand, silt and gravel from the ground surface to about El. 103
to 104 ft., overlying “compact” sand, silt and gravel to the exploration bottoms of about El. 96 and 101 ft. The
logs indicate “blows per foot on 1ʺ spoon produced by 30ʺ fall of 140# hammer,” as 9 and 11 for the looser/upper
soil, and 43 and 49 for the denser/lower soil. Logs of the borings are shown on the 1956 Plans attached in
Appendix A, and the boring locations are shown on Figure 5.
2.3 Subsurface Explorations
SA engaged Northern Drill Service, Inc. (Driller) of Northborough, Massachusetts to perform two subsurface
explorations (borings) on February 17, 2016 at the embankment right of the spillway. The purpose of the borings
was to evaluate subsurface conditions of the Dam for our use in analysis and design, and to obtain samples for
geotechnical laboratory testing. SA marked the explorations locations in the field, and notified DigSafe System,
Inc. and the Town of Canton water and sewer departments for utility clearance prior to drilling. SA observed
and logged the explorations in the field.
The Driller advanced borings SA-1-OW and SA-2-OW to depths of about 36 and 16 ft. below ground surface
(bgs), respectively (about El. 80 and 100 ft., respectively), using cased wash boring techniques. The Drillers
performed Standard Penetration Tests (SPT) and obtained split spoon samples continuously in the top 16 ft., and
at about 5-ft intervals or less at greater depths, in general accordance with ASTM D-1586. Upon completion,
the Drillers installed observation wells in the borings.
2.4 Subsurface Conditions
The generalized subsurface descriptions presented below and on Figure 6 are interpretations intended to
highlight the major subsurface strata based on available data. Detailed descriptions of subsurface conditions are
presented in the logs of the individual explorations. Interested parties should review the exploration logs for
specific information at individual exploration locations. The strata shown on the logs approximate conditions
only at the actual boring locations at the time of drilling. Variations may occur and should be expected between
boring locations and over time. The strata delineations represent interpretations of the approximate boundaries
between subsurface materials. The actual transition may be gradual. Logs of SA’s explorations are presented
in Appendix A and Figure 5 shows the exploration locations.
Our generalized description of subsurface conditions is as follows:
Fill – The Driller generally encountered about 2 in. of asphalt pavement at the ground surface overlying
Fill extending to about 12 ft. bgs (about El. 104 ft.). The Fill generally consisted of brown sand and
gravel, little to some silt. One sample in boring SA-1-OW encountered silty sand and gravel with trace
organics at about 10 ft. bgs (about El. 106 ft.). SPT N-values in the Fill ranged from 12 to 33 blows per
foot (bpf) in the top ±half of the Fill, indicating medium dense to dense consistency, and 1 to 9 bpf in
the bottom ±half of the Fill, indicating very loose to loose consistency.
SA No. 052-15-022 1/12/2018 Page 5 of 17Source page 11
Silty Sand and Gravel – Underlying the Fill, the Driller encountered gray sand and gravel, trace to little
silt, extending to the bottom of the borings. SPT N-values were generally 40 bpf or greater indicating
dense to very dense consistency. One sample encountered refusal,1 and the Driller also noted occasional
boulders in this stratum.
The subsurface conditions encountered in SA’s borings are generally consistent with the conditions shown on
the boring logs on the 1956 Plans, and with the surficial geologic information described above.
2.5 Groundwater Observations
Table 1 summarizes SA’s observations of water elevations in Silk Mill Pond and the observation wells. Water
levels in the observation wells generally varied between El. 108 and 109 ft. while Pond elevation was about
113.3 to 113.5.
2.6 Geotechnical Laboratory Testing and Permeability
SA performed four particle size (sieve and hydrometer) analyses on samples obtained in borings SA-1-OW and
SA-2-OW. The purposes of the laboratory tests were to assist in soil classification and in evaluating soil
permeability for stability and seepage analyses. Appendix A contains the laboratory test results. Table 2
summarizes the results and the estimated soil hydraulic conductivity.
We estimated vertical hydraulic conductivity (permeability) of embankment and foundation soils using particle
size data of samples obtained in the borings with the Kozeny-Carman Formula (Carrier 2003, Aubertin et al.
2005, Chapuis and Aubertin 2003). Based on correlation with particle size analyses, we estimate vertical
hydraulic conductivity of the soils tested to range from about 5x10-4 to 2x10-3 cm/s. Soils tested included Fill
and Silty Sand and Gravel. According to EPRI EL-6800 (EPRI 1990), these values are consistent with the
approximate range of values for sand and “silty/dirty sands”, and are considered “low” to “medium”
permeability. We assumed horizontal permeability was the same (i.e., permeability was assumed isotropic).
We note that the permeability estimates correlated with, and based on, particle size data are not measured.
Aubertin, et al. (2005) indicate that measured values of hydraulic conductivity usually range from 1/3 to 3 times
the value estimated by the Kozeny-Carman Formula. SA estimated permeability only of soils recovered from
the split-spoon sampler. The samples were therefore disturbed, represented a composite sample over the depth
of the split spoon, and did not include large gravel, cobbles or boulders that could not be sampled. Permeability
of in-situ soils and soils containing larger materials can vary significantly from homogeneous soils containing
purely smaller particles. The references note that nearly all laboratory measurements used to validate the
Kozeny-Carman Formula were based on vertical hydraulic conductivity. The limitations of permeabilities
estimated through correlation with grain size distributions, as described herein, should be understood when
interpreting the values reported herein. In our seepage modeling described below, SA varied permeability of
materials, where appropriate, in consideration of these limitations.
1
Sampler refusal is defined as 10 blows for 0 inches, 50 blows for 6 inches or less, or 100 blows for 18 inches or less of
sampler penetration.
SA No. 052-15-022 1/12/2018 Page 6 of 17Source page 12
2.7 Spillway Concrete Testing and Evaluation
SA evaluated the existing spillway concrete by visual observation, exploration (concrete coring), laboratory
testing, and structural analysis of the piers and abutments, as described below. Based on the results of our
evaluation, we determined that the left spillway abutment and both piers needed to be replaced in their entirety,
and that the right spillway abutment needed to be replaced above El. 111.5 ft.
SA visually inspected the Spillway on December 9, 2016 following dewatering of the impoundment by the
Town. Figure 4 shows photographs compiled from the dewatered visual inspection and other Site visits. We
noted the following:
• The concrete of the left abutment appears to have been previously repaired as the surficial concrete differs
from the concrete observed at the piers and right abutment. The left abutment concrete was significantly
deteriorated, cracked and spalled over most of the visible surface; and
• The two piers and right abutment showed moderate cracking and efflorescence above the water line, but
were generally in good condition below the water line on both the upstream and downstream sides.
SA engaged ProCut of MA (ProCut) to obtain four, 6-in. diameter concrete cores, one from the top of each pier
and abutment, on December 9, 2016. Figure 5 shows the core locations. SA engaged Simpson Gumpertz &
Heger to perform laboratory testing of the concrete cores. Testing included petrography of core SA-C3, obtained
from the right pier, and unconfined compressive strength of core SA-C4 obtained from the right abutment. The
purpose of the laboratory testing was to further evaluate concrete properties and condition of the piers and right
abutment. Appendix A contains the test results. The concrete laboratory noted the following results from the
pier and right abutment cores:
• Degradation from alkali silica reaction (ASR), causing interconnecting fractures throughout the concrete
core, rated as a “3” on a scale of 0 to 6, indicating moderate cracking/moderate evidence of deleterious ASR;
• Surficial degradation such as leaching extending up to 1/16 in. into the concrete and carbonation extending
up to 3/16 in. into the concrete, and up to 1/2 in. along fractures perpendicular to the surface;
• Compressive strength of 4,680 psi;
• Estimated air content of 7 to 8 percent;
• Estimated water/cement ratio of 0.35 to 0.45;
The laboratory results for concrete compressive strength, air content, and water/cement ratio are generally
consistent with typical, modern design standards.
In our opinion, concrete deterioration at the left abutment likely resulted from cyclic freezing and thawing, and
from use of inferior quality concrete compared to that used for the piers and right abutment. In our opinion, the
cracking and efflorescence of the piers and right abutment likely resulted from a combination of factors, but
predominately ASR and possibly cyclic freezing and thawing because degradation is significantly worse above
the water line. As discussed by USBR (1997), cyclic freezing and thawing often occurs where concrete is nearly
fully saturated and has southern exposure, which results in frequent thawing when exposed to the sun and
freezing at night. The tops and upstream side of the abutments and piers have southern exposure.
SA evaluated the structural capacity of the existing piers and abutments under water pressure at normal pool
plus ice load of 4.7 k/ft. (described in Section 4) using standard LRFD methods. The result indicated that the
concrete and reinforcing steel design of the existing piers, as shown on the 1956 Plans, does not provide
sufficient moment capacity to resist the design load, however, the existing abutment design provides sufficient
shear and moment resistance.
SA No. 052-15-022 1/12/2018 Page 7 of 17Source page 13
Based on the results of visual inspection, concrete laboratory testing, and structural evaluation, SA selected the
following approach to repair the spillway:
• Replace entirety of left spillway abutment upstream of the bridge based on degradation identified visually;
• Replace entirety of both piers based on results of structural evaluation;
• Replace top of right abutment above El. 111.5 (about 2 ft. below normal pool) based on visual observations
and results of laboratory testing;
• Repair surface of concrete to remain of the base slab, spillway right abutment, and bridge abutments as
needed.
3. HYDROLOGY AND HYDRAULICS
3.1 Summary and Conclusion
According to Massachusetts Dam Safety Regulations, the spillway design flood (SDF) for existing
Small Size, Significant Hazard Dams is the flood resulting from the 100-year storm (Q100 or 100-year flood).
SA previously evaluated hydrology and hydraulics (H&H) for the Dam, which are summarized in the following
sections and our previous reports (SA 2011, SA 2012a, SA 2012b). The H&H characteristics of the
Dam/impoundment are complex because Massapoag Brook upstream of the impoundment bifurcates, with some
flow entering Silk Mill Pond (the impoundment) and the remaining flow continuing in a diversion channel that
bypasses the Pond and continues through a culvert under Messinger Street, as described in Section 1.2 and shown
on Figure 2. Furthermore, an auxiliary outlet to the impoundment discharges back to the diversion channel. The
hydraulic behavior of the diversion channel, impoundment, auxiliary outlet, diversion dike/berm, Messinger
Street culvert and primary spillway varies with flow rate, Pond elevation, and height/presence of stoplogs, among
other factors. The H&H information is further elaborated in the following sections.
The H&H results indicated that the Dam overtops by about 0.8 ft. in the 100-year flood with stoplogs in place.
Removing stoplogs in anticipation of flooding may lower the impoundment elevation during the 100-year flood
and avoid overtopping the Dam, however, flow through the Dam would increase (more water would be diverted
to the Dam instead of the diversion channel), increasing downstream flooding along Massapoag Brook. The
Town therefore typically maintains the stoplogs in place during floods.
During conceptual design of repairs, SA considered potential, limited (in scale) modifications to the Dam to
attempt to mitigate overtopping in the 100-year flood and potentially reduce downstream flooding on Massapoag
Brook. We conceptualized that the Town could maintain the existing hydraulic configuration and provide
erosion resistance to overtopping, but found no other limited/minor (in scale) physical modifications that would
alleviate overtopping in the 100-year flood because significantly more flow would need to be diverted to Beaver
Meadow Brook, which would require significant modifications to the Dam and/or diversion berm/channel and
evaluation of downstream impacts. Nonetheless, such significant modifications might include raising the Dam
(e.g. by a concrete dike/parapet wall, etc.) or modifying the diversion berm/channel (increase height and/or
width) and replacing the culvert beneath Messinger Street. Such significant modifications would be to divert
more flow to Beaver Meadow Brook, but could result in impacts to properties abutting the impoundment and
downstream on Beaver Meadow Brook, Bolivar Pond, and at Bolivar Pond Dam. The Town concluded to
SA No. 052-15-022 1/12/2018 Page 8 of 17Source page 14
substantially maintain existing hydraulics, and to design and construct overtopping erosion resistance instead of
significant hydraulic modifications because:
• The depth of overtopping in the design flood is small - less than 1 ft.;
• The significant modifications would require much additional evaluation of impacts, and therefore, the
practicability of significant modifications was uncertain;
• The cost for evaluation, design and construction of significant modifications would significantly exceed the
Town’s budget for repairs; and
• The goal of repairs is to address requirements of MA DCR ODS to improve Dam condition to better than
Poor, which can be achieved economically by enhancing erosion resistance during overtopping.
SA therefore designed the Dam repairs to resist erosion during overtopping, generally including:
• Repaving Old Shepard Street, the Dam crest;
• Constructing a concrete cap on the downstream stone masonry wall, continuous with the asphalt pavement,
and providing filtered drainage below the pavement and through the cap;
• Extending asphalt pavement to the downstream retaining wall and downstream rip-rap, as applicable;
• Constructing stone revetment at the base of the downstream stone masonry wall and placing rip-rap in a low
area on the left downstream side of the dam. SA designed the rip-rap and revetment to resist erosion due to
overtopping flows, velocities and flow depths that we estimated in the SDF, and to be of sufficient weight
to resist vandalism.
The attached design drawings illustrate these erosion resistance measures. Additional details of our previous
H&H evaluations pertinent to the design of overtopping erosion resistance are summarized below.
3.2 Summary of Previous Hydrologic Evaluation
SA previously estimated the 100-year flood at Shepard Pond Dam, just upstream of Old Shepard Street Dam, as
1,040 cfs peak flow (SA 2011), based on a 100-year 24-hour precipitation of 9.1 inches and modeling the
drainage area of 10.9 square miles using the SCS TR-20 method as programmed in HydroCAD v8.0 computer
software. Figure 7 shows the estimated drainage area. Since the difference in drainage area between Shepard
Pond and Old Shepard Street Dam is less than 0.1 square miles, we estimated the 100-year flood in Massapoag
Brook upstream of the bifurcation to the diversion channel and Silk Mill Pond is substantially similar to the
1,040 cfs at Shepard Pond Dam. SA’s previous reports (SA 2011, SA 2012a, SA 2012b) provide additional
details.
3.3 Summary of Previous Hydraulic Evaluation
SA previously modeled hydraulics of the system using USACE HEC-RAS computer software as part of our
previous breach analysis (SA 2012b). We estimated flows and elevations for cases with stoplogs in place (as
the Dam is typically operated) and stoplogs removed. In summary, when stoplogs are maintained in place (as it
is typically operated), we estimate that the diversion channel and Pond would become one water body during
the 100-year flood, discharging through the culvert at Messinger Street and through the Dam, and we estimate
the impoundment would overtop the Dam and Old Shepard Street by about 0.8 ft. To be clear, this is the way
the hydraulic system is currently operated, and changing the system was judged to be costly and inconclusive.
Additional hydraulic results are shown in Table 3.1 below.
SA No. 052-15-022 1/12/2018 Page 9 of 17Source page 15
Table 3.1 – Estimated Hydraulic Information
Impoundment Elevation, Q100 116.5 ft.
Flow over Spillway/Embankment, Q100 610 cfs
Flow Through Auxiliary Outlet (Diversion Channel/Messinger
430 cfs
Street Culvert), Q100
Depth of Overtopping, Dam Embankment (Old Shepard Street),
0.8 ft.
Q100
Spillway Capacity at Maximum Impoundment Elevation =
230 cfs
115.7 (low point of embankment crest)
Flow Through Messinger Street Culvert at Impoundment
350 cfs
Elevation = 115.7
Floodwater that overtops the Dam crest would generally flow across Old Shepard Street, over the downstream
stone masonry wall, and return to Massapoag Brook downstream of the spillway. Some overtopping flow would
also likely enter a low wetland near the left downstream side of the Dam, and follow that wetland further
downstream before re-entering Massapoag Brook (SA 2012b). Such overtopping flows could potentially erode
the stone masonry portion of the downstream wall, causing instability of the wall, or erode the embankment
where flows lead to the wetland, and, under prolonged flood, could cause breach of the embankment-portion of
the Dam.
SA’s previous reports (SA 2012a,b) provide additional details of hydraulic evaluation, including cases with
stoplogs removed. As indicated above, removal of stoplogs likely increases flooding of Massapoag Brook
downstream of the Spillway, and the Town therefore typically maintains the stoplogs in place during floods.
The effects of Old Shepard Street Dam and the diversion channel on mitigating flooding downstream of the Dam
are unclear, however, it appears the Dam and diversion channel may provide some flood mitigation, particularly
in floods less than the 100-year flood, as reported in the Canton Flood Insurance Study (FEMA 1987). As noted
in previous reports (SA 2012a), SA found no documentation of intended design or operation for mitigating
flooding. The area around Massapoag Brook downstream of Old Shepard Street Dam is more developed with
smaller flood plains than the area downstream of the diversion channel, and, according to the Town, is more
susceptible to flood damage.
SA No. 052-15-022 1/12/2018 Page 10 of 17Source page 16
4. SEEPAGE AND STABILITY, AND STRUCTURAL DESIGN
SA evaluated seepage through the Dam embankment and foundation; and stability of the Spillway, embankment
upstream slope, and downstream retaining wall in support of the DCR ODS Chapter 253 Dam Safety Permit
Application. SA found no records of previous stability nor seepage evaluation. Details of our evaluation are
summarized in the following sections. Appendix B provides evaluation details and output.
4.1 Model Geometry
4.1.1 Embankment Model Cross-Section
SA modeled a cross-section through the embankment right of the Spillway. Figure 5 shows the location
and Figure 6 shows the model cross-section. The model cross-section is SA’s interpretation of embankment
geometry based on our observations and elevation measurements, subsurface conditions encountered in the
borings, file review, and discussion with Town personnel. In general, SA found no detailed design, construction
or other written records describing the configuration of the embankment or its retaining walls. SA interpreted
the model embankment geometry and properties as follows:
• The 1956 Plans, a historical photograph, and reports from Town DPW personnel indicate a stone
masonry wall, possibly mortared, previously formed the embankment upstream face. Town DPW
personnel stated that the Town dumped rip-rap from the road into the pond to buttress the stone masonry
wall, thereby forming the upstream slope that is currently visible. We therefore assumed that an
upstream stone masonry wall is present beneath the rip-rap; its geometry is the same as the downstream
stone masonry wall; and that the rip-rap likely settled into, and intermixed with, pond sediment;
• The width of the downstream stone masonry wall is uncertain. We interpret the wall to be four feet wide
at the base, 3 ft. wide at the top based on our Site observations and probing of voids between stones;
• We assumed that the bottom elevation of the upstream and downstream stone masonry walls and
upstream rip-rap to be at the bottom elevation of fill interpreted from the borings;
• We estimated soil permeability and properties based on the results of the subsurface explorations and
geotechnical laboratory testing. We varied model permeability to calibrate model phreatic surface with
water levels measured in the observation wells.
4.1.2 Spillway Model
SA modeled the spillway based on the 1956 Plans, in conjunction with our observations, elevation
measurements, and subsurface conditions encountered in the borings. The 1956 Plans show steel sheet piles
below the upstream face of the spillway wing-wall footings extending to design bottom elevation 91 ft.
4.1.3 Ice Loads
For our use in analyses and design, SA estimated ice loads of 4.7 kips/ft. based on ice contact pressure
of 5 ksf recommended in FERC (2016) and ice thickness estimated using the method of USACE (2004) and
meteorological data from Blue Hill Observatory in Canton, MA (NCDC 2012).
SA No. 052-15-022 1/12/2018 Page 11 of 17Source page 17
4.2 Seepage Evaluation
SA modeled seepage through the embankment and foundation using the groundwater flow components of Plaxis
v8.6 finite element software to estimate the embankment phreatic surface, seepage gradients, and soil total
stresses compared to water pressures resulting from seepage (i.e. a safety factor) at the downstream embankment
toe. the model results indicate that safety factors near the downstream embankment toe meet or exceed design
standards for normal pool and 100-year flood. Appendix B contains the details of our analysis and representative
model results.
SA did not evaluate seepage safety factors for the spillway because the 1956 Plans show steel sheet piles beneath
the spillway, presumably to resist seepage. We noted incidentally that, since the 1956 Plans show the sheet piles
extending to El. 91 ft., the seepage path beneath the spillway and sheet piles would be deeper (i.e. longer) than
at the embankment, and therefore the seepage factors of safety at the spillway are likely higher (more
conservative) than those estimated from the embankment seepage model.
4.3 Stability Evaluation
SA evaluated stability of the spillway and embankment downstream stone masonry retaining wall by gravity
(aka force-equilibrium) methods. We evaluated stability of the embankment upstream rip-rap slope as described
below. Results of analyses for each component and load case indicated factors of safety exceeding those
stipulated by the Regulations. Appendix B provides details of the evaluations and tabulates the results. A brief
summary of the load cases evaluated includes:
• SA evaluated the spillway and embankment downstream stone masonry wall for sliding and overturning
using the load cases cited by Regulations 10.14(9)(j) (i.e. Case I Usual, Case II Unusual, and Case III
Extreme, where applicable to each structure). As the embankment carries Old Shepard Street, SA also
applied a traffic surcharge load (for non-earthquake load cases) based on AASHTO (2012). The results
indicated sliding safety factors exceeding those stipulated by Regulations 10.14(9)(k) for gravity dams of
intermediate size, and bearing stresses within ranges SA judged to be allowable.
• SA evaluated the embankment upstream slope stability using the applicable load cases and required safety
factors cited by Regulations 10.14(9)(c) (i.e. end of construction, sudden drawdown from maximum pool
and/or spillway crest, steady seepage with maximum storage pool, and earthquake). We also applied a traffic
surcharge load to the crest for non-earthquake cases as described above. Results indicated factors of safety
exceeding those stipulated by the Regulations.
4.4 Structural Design
SA evaluated the spillway concrete as described in Section. 2.7 above and concluded to replace the left abutment,
piers, and top of right abutment with new reinforced concrete. New rebar from the replacement structural
components will be epoxied into, and derive resistance from, the existing concrete base slab and/or portion of
right abutment to remain. SA designed the replacement structural components according to USACE EM 1110-
2-2104 (2003), ACI 350 (2001), and/or ACI 318 (2011), as applicable. SA designed for ice loads cited above
with water pressure at normal pool, and checked designs for water pressures in the 100-year flood and other
structural loads.
SA No. 052-15-022 1/12/2018 Page 12 of 17Source page 18
5. IMPLEMENTATION OF REPAIRS AND IMPROVEMENTS 5.1 Project Schedule, Water Diversion and Observation We anticipate construction duration on the order of three months, commencing on or after July 1, 2018. The Contractor will be responsible for the schedule, subject to local, state and federal regulations and requirements of permits issued for the Project. The Contractor will also be responsible for means and methods of water diversion, as described in the Design Documents. Before commencing dewatering or land-disturbing activities, the Contractor is required to submit a Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan (CPPP ESCP), a Water Control Plan, and a Flood Contingency Play. We anticipate that dewatering of the impoundment to about El. 111 to 109 ft. will be needed, combined with localized cofferdams at the inlet to Silk Mill Pond and at the Dam. SA and the Town will evaluate an impoundment refilling schedule at construction approaches completion. We anticipate the refilling schedule will depend on the time of year, precipitation, ambient flows, etc. The Town intends to engage SA to observe construction of the repairs. SA is planning for full-time observation of the dam repairs, submittal review, and laboratory and field testing of concrete and fill. 5.2 Borrow Materials and Reuse of On-Site Materials The Contractor will be responsible for identifying sources of materials and obtaining those materials. Reclaimed road paving materials might be suitable for reuse as Dense Graded Crushed Stone, provided that they meet the requirements specified in the Design Documents. Further, we anticipate that existing stones to be removed from the top of the downstream stone masonry wall can also likely be re-used on-Site as rip-rap and/or revetment. We anticipate that neither quantity nor quality of Site soils will likely meet the requirements for other materials (e.g. Slope Paving, Stone for Pipe Ends, etc.), and such materials will need to be imported to the Site. 5.3 Operation and Maintenance (O&M) Manual An Operations and Maintenance (O&M) Manual is attached in Appendix C. 5.4 Emergency Action Plan (EAP) SA prepared an Emergency Action Plan (EAP) dated June 20, 2012 for the existing Dam. In our opinion, the repairs will not significantly change the Dam configuration and operation, and the existing EAP will be applicable. The existing EAP is filed with the Town. SA No. 052-15-022 1/12/2018 Page 13 of 17
Source page 19
5.5 Permitting
SA is preparing permits on behalf of the Town as follows:
Permit Status
MA DEP WPA Form 3 – Notice of Intent Submission expected January 2018
Town of Canton Application for Soil Erosion and Submission expected January 2018
Sediment Control Plan Certification and Land
Disturbance Permit
USACE Self-Verification Notification Form Submission expected prior to construction as it is a
notification under the State General Permit and
does not require USACE approval
6. EXCAVATIONS, LIMITATIONS AND REFERENCES
6.1 Excavations
Stephens Associates Consulting Engineers, LLC (SA) is providing this information solely as a service to our
Client. Under no circumstances should the information provided below be interpreted to mean that SA or the
Owner is assuming responsibility for construction site safety or the contractor's activities; such responsibility is
not being implied and should not be inferred.
The Owner and the Contractor should make themselves aware of and become familiar with applicable local,
state, and federal safety regulations, including the current Occupational Safety and Health Administration
Excavation and Trench Standards. In Federal Register, Volume 54, No. 209 (October 1989), the United States
Department of Labor, Occupational Safety and Health Administration (OSHA) amended its "Construction
Standards for Excavations, 29 CFR, Part 1926, Subpart P". This document was issued to reduce the risk of death
or injury from collapse of trenches and excavations. Construction site safety generally is the sole responsibility
of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction
operations.
6.1.1 Excavations and Slopes
The Contractor is solely responsible for designing and constructing stable, temporary excavations and
should shore, slope, or bench the sides of the excavations as required to maintain stability of the excavation sides
and bottom. Slope height, slope inclination, or excavation depths (including utility trench excavations) should
in no case exceed those specified in local, state, or federal safety regulations (e.g., OSHA Health and Safety
Standards for Excavations, 29 CFR Part 1926, or successor regulations, etc.). The Contractor should be aware
that such regulations are strictly enforced and, if they are not followed, the Owner, Contractor, and/or earthwork
and utility subcontractors could endanger worker and public health, safety and property, and be liable for
substantial penalties.
The Contractor's responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed
in the excavations as part of the Contractor's safety procedures. The exposed slope face should be protected
against the elements. If any excavation, including a utility trench, is extended to a depth of more than twenty
SA No. 052-15-022 1/12/2018 Page 14 of 17Source page 20
(20) feet, it will be necessary to have the side slopes designed by a professional engineer registered in the state
where construction is occurring. As a safety measure, all vehicles and soil piles should be kept a minimum
lateral distance from the crest of the slope equal to no less than 1.5 times the slope height.
6.1.2 Important Note on Soil Variability
The soils to be excavated may vary significantly across the Site. Subsurface explorations performed as part of
this Report indicate that near-surface soils are generally classified as Sand and Gravel based on ASTM D2488
– the Visual-Manual Procedure. This is considered Type C soil when applying the OSHA regulations. OSHA
mandates that slope inclinations not exceed 1.5 : 1, horizontal : vertical, for Type C soils for excavations of 20
feet or less. Our preliminary soil classification is based solely on our subsurface explorations. The Contractor
should verify that these soil conditions exist throughout the proposed area of excavation. The Contractor's
responsible person, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations in
accordance with OSHA requirements as part of the Contractor's safety procedures.
6.1.3 Temporary Shoring
As an alternative to temporary slopes, vertical excavations can be temporarily shored. The Contractor
or the Contractor's specialty subcontractor would be responsible for the design of the temporary shoring in
accordance with applicable regulatory requirements. By regulation, excavations exceeding 20 feet in height
require design by a registered Professional Engineer.
6.2 Limitations
Stephens Associates Consulting Engineers (SA) has prepared this Report based on the information available to
us at this time, including design information furnished through the Client, the Owner and their representatives
for the proposed Project. If any of the noted information is incorrect or has changed (e.g., assumptions, revisions
to the design; subsurface conditions encountered during excavation for construction are different from those
noted in this Report, etc.), SA should be notified and retained to review the corrections and changes and amend
this Report. If SA is not retained for these purposes, we cannot be responsible for the impact of those conditions
on the performance of the Project.
The subsurface descriptions contained in this Report are generalized to highlight the major soil strata as
interpreted from readily available data. The soil/rock strata and groundwater surface are interpretations from
widely spaced data and represent the approximate boundaries between subsurface materials. The actual
transition between strata may be gradual. Explorations (e.g., boring logs) should be reviewed for specific
information at respective locations. The data shown on the logs prepared by SA represent the conditions only
at the actual exploration locations at the time the explorations were undertaken. Further, variations in subsurface
conditions may occur and should be expected between exploration locations and over time. Seasonal fluctuation
of groundwater depths should be anticipated, as well as fluctuations with nearby surface water. We recommend
that the contractor measure the actual groundwater levels at the time of construction and evaluate groundwater
impact on the construction procedure, and the impact of the construction on groundwater levels.
This Report has been prepared by SA for the exclusive use of the Town of Canton and for the specific application
to the subject Project, as conceived at this time. The Report is for design only, and by itself is not sufficient to
prepare an accurate cost estimate or construction “bid.” Subject to the limitations inherent in the agreed scope
of work as to the degree of care, amount of time and expenses to be incurred, and subject to any other limitations
contained in the Agreement for SA’s services, SA has performed its services with the degree of care and skill
SA No. 052-15-022 1/12/2018 Page 15 of 17Source page 21
ordinarily exercised by other professional engineers under similar circumstances at the time the services were performed. No warranties are implied or expressed. 6.3 References and Previous Reports Commonwealth of Massachusetts Department of Conservation and Recreation, Office of Dam Safety (2017), 302 CMR 10.00 Dam Safety, Commonwealth of Massachusetts Department of Conservation and Recreation, Office of Dam Safety, February 10, 2017 (Regulations). Federal Energy Regulatory Commission (FERC) (2016) "Engineering Guidelines for the Evaluation of Hydropower Projects," Chapter III - Gravity Dams, March 4, 2016. Natural Resources Conservation Service (NRCS) (2016), Web Soil Survey, http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx, accessed by SA on February 5, 2016. The Commonwealth of Massachusetts (2015), Standard Specifications for Highways and Bridges, incl. Supplemental Specifications, MassDOT, July 1, 2015. Fell, R., MacGregor, P., Stapledon, D., and Bell, G., Foster, M. (2014) “Geotechnical Engineering of Dams, 2nd Edition” CRC Press. American Association of State Highway and Transportation Officials (AASHTO) (2012) “LRFD Bridge Design Specifications, Customary US Units,” Washington, D.C. Stephens Associates Consulting Engineers, LLC (2012a) Old Shepard Street Dam aka Shepard Street Dam, Phase I Inspection/Evaluation Report, Canton, Massachusetts," September 14, 2012 (2012 Phase I Report). Stephens Associates Consulting Engineers, LLC (2012b) Old Shepard Street Dam aka Shepard Street Dam, Emergency Action Plan, Canton, Massachusetts," June 20, 2012 (EAP). Stephens Associates Consulting Engineers, LLC (SA) (2011), “Shepard Pond Dam aka Washington Street Dam, Phase II Evaluation Report,” February 28, 2011. (Shepard Pond Dam Phase II Report) American Concrete Institute (ACI) (2011), “Building Code Requirements for Structural Concrete, ACI 318-11 and Commentary,” August, 2011. Stephens Associates Consulting Engineers, LLC (2007) Old Shepard Street Dam aka Shepard Street Dam, Phase I Inspection/Evaluation Report, Canton, Massachusetts," July 20, 2007 (2007 Phase I Report). USACE (2006) "Engineering and Design: Ice Engineering." USACE Engineering Manual (EM) 1110-2-1612, Change 3, September 30, 2006. Aubertin et al. (2005), Discussion of "Goodbye, Hazen; Hello, Kozeny-Carman," Journal of Geotechnical and Geoenvironmental Engineering, Vol. 131, No. 8, August 2005, American Society of Civil Engineers. US Army Corps of Engineers (USACE) (2004), "Method to Estimate River Ice Thickness Based on Meteorological Data," USACE Engineer Research and Development Center (ERDC)/ Cold Regions Research and Engineering Laboratory (CRREL) Technical Note 04-3, Hanover, New Hampshire, June. SA No. 052-15-022 1/12/2018 Page 16 of 17
Source page 22
Carrier III, W.D. (2003), "Goodbye, Hazen; Hello, Kozeny-Carman," Journal of Geotechnical and Geoenvironmental Engineering, Vol. 129, No. 11, November 2003, American Society of Civil Engineers. Chapuis, R.P., and Aubertin, M. (2003) "Evaluation of the Kozeny-Carman's Equation to Predict the Hydraulic Conductivity of a Soil," Canadian Geotechnical Journal, 40(3), 616-628. USACE (2003) “Strength Design for reinforced-Concrete Hydraulic Structures,” EM 1110-2-2104, Change 1, June 30, 1992, Change 1, August 20, 2003; American Concrete Institute (ACI) (2001), “Code Requirements for Environmental Engineering Concrete Structures, ACI 350-01 and Commentary ACI 350R-01,” December 22, 2001. USACE (1995) "Engineering and Design: Gravity Dam Design," EM 1110-2-2200, June 30, 1995. USACE (1993) “Seepage Analysis and Control for Dams,” EM 1110-2-1901, Change 1, April 30, 1993. EPRI EL-6800 (1990), Manual on Estimating Soil Properties for Foundation Design, Electric Power Research Institute, prepared by Cornell University, Ithaca, NY. Federal Emergency Management Agency (FEMA) (1987) Flood Insurance Study, Town of Canton, Massachusetts, June 4, 1987. Chute, N.E., (1966a), Plate 1: Bedrock Geologic Map and Sections of the Norwood Quadrangle, Massachusetts, Geology of the Northwood quadrangle, Norfolk and Suffolk Counties, Massachusetts: U.S. Geological Survey, Bulletin 1163-B, scale 1:24000. Chute, N.E., (1966b), Plate 2: Surficial Geologic Map of the Norwood Quadrangle, Massachusetts, Geology of the Northwood quadrangle, Norfolk and Suffolk Counties, Massachusetts: U.S. Geological Survey, Bulletin 1163-B, scale 1:24000. Fenton G Keyes Associates (1956) “The Proposed 1955 Flood Bridge, Canton, Sheppard St. at Third Mill Pond, Bridge No. C-2-20, Issued for Construction” prepared for the Massachusetts Department of Public Works, dated February 18, 1956, 3 sheets, obtained by SA from MassDOT on January 28, 2016 (1956 Plans); SA No. 052-15-022 1/12/2018 Page 17 of 17
Source page 23
REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
CANTON, MASSACHUSETTS
FIGURES
SA No. 052-15-022 1/12/2018 Page F-1 of 13Source page 24
Project: Number: 052-15-022 Sheet 1 of 1
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: J. Turner Date: January 12, 2018 _ Subject: FIGURE 1 - Site Location Map
Checked By: NAO Date: January 12, 2018
03/25/04 Exeter River 42,15163° N, 71.14138° W NAD27
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Map created with TOPO!® ©2001 National Geographic (www.nationalgeographic. com/topo)
Longitude 71.14751 degrees west
Latitude 42.14655 degrees north
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Copyright © 2018 Stephens Associates Consulting Engineers LLC Stephens Associates
Revisions: Consulting Engineers
By: Date: panel ate
By: Date: Inisemelre” Hydrology & Hydraulics
SACE 00-1 (v. 1) 1/00 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115
[Original embedded text, retained for comparison]
Project: Number: 052-15-022 Sheet 1 of 1
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: J. Turner Date: January 12, 2018 Subject: FIGURE 1 - Site Location Map
Checked By: NAO Date: January 12, 2018
Approximate Site
Location
Image obtained from MassGIS, accessed September 3, 2015.
http://maps.massgis.state.ma.us/map_ol/oliver.php
Longitude 71.14751 degrees west
Latitude 42.14655 degrees north
NAD 1983, MassGIS Oliver Web-based Mapping Application
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
SACE 00-1 (v. 1) 1/00 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 25
Project: Number: 052-15-022 Sheet 1 of 1
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: J. Turner Date: January 12, 2018 Subject: FIGURE 2 - Site Aerial Photograph
Checked By: NAO Date: January 12, 2018
Massapoag Brook
Spillway
Silk Mill Pond
Old Shepard St.
Auxiliary Outlet (outflow
Earthen Diversion Dike to Diversion Channel)
Flow Splits between Pond
and Diversion Channel
Beaver
Diversion Channel Meadow
Brook
Massapoag Brook Messinger St.
Graphic Scale
± 200 ft
Image from MassGIS as presented by Google Earth, which indicates photograph taken in April 2008
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
SACE 00-1 (v. 1) 1/00 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 26
Project: Number: 052-15-022 Sheet 1 of 1
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: N. Olson Date: January 12, 2018 Subject: FIGURE 3 - Excerpt of MassGIS Parcel Map
Checked By: J. Turner Date: January 12, 2018
Image from MassGIS Canton, MA MuniMapper, http://maps.massgis.state.ma.us/map_ol/canton.php, accessed by
SA on November 17, 2017. This map is only a representation of property boundaryies, not an authoritative source.
A legally authoritative map of property boundaries can only be produced by a professional land surveyor.
Lot Property Owner
24-70-0 Town of Canton
24-71-0 Town of Canton
24-72-0 Town of Canton
24-156-0 Town of Canton
24-157-0 Town of Canton
24-74-0 Kevin R Platt and Catherine J Platt
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
SACE 00-1 (v. 1) 1/00 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 27
Project: Number: 052-15-022 Sheet 1 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo No. 1 Description:
Embankment crest (Old Shepard Street) left of spillway
Photo Date: 12/9/2015
Photo No. 2 Description: Embankment crest (Old Shepard Street) at spillway, looking toward right end of
Photo Date: 12/9/2015 embankment
Copyright © 2018 Stephens Associates Consulting Engineers LLC
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By: Date:
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12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 28
Project: Number: 052-15-022 Sheet 2 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo No. 3 Description:
Embankment upstream slope left of spillway
Photo Date: 12/9/2015
Photo No. 4 Description:
Embankment upstream slope right of spillway
Photo Date: 12/9/2015
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 29
Project: Number: 052-15-022 Sheet 3 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo No. 5 Description:
Embankment downstream slope left of spillway
Photo Date: 12/9/2015
Photo No. 6 Description:
Embankment downstream stone masonry retaining wall right of spillway
Photo Date: 12/9/2015
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 30
Project: Number: 052-15-022 Sheet 4 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo No. 7 Description:
Embankment downstream slope about 200 ft. left of spillway, from left
Photo Date: 12/9/2015
Photo No. 8 Description:
Embankment downstream slope about 200 ft. left of spillway, from right
Photo Date: 12/9/2015
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 31
Project: Number: 052-15-022 Sheet 5 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo No. 9 Description:
Upstream face of spillway (white discoloration is from core drilling)
Photo Date: 12/9/2015
Photo No. 10 Description:
Upstream slope right of spillway
Photo Date: 2/17/2016
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 32
Project: Number: 052-15-022 Sheet 6 of 6
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Figure 4 - Representative Photographs
Checked By: JET Date: January 12, 2018
Photo Number: 11 Right spillway abutment and piers, from left Photo Number: 12 Left spillway abutment and piers, from right spillway
Description: spillway abutment Description: abutment
Photo Date: 12/9/2015 Photo Date: 12/9/2015
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
12345667859AB58C58D66 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 33
Graphic Scale
0 5 10 ft.
Original Drawing Size = 22 x 34 in.
OWNER
TOWN OF CANTON, MA
CLIENT
TOWN OF CANTON, MA
By: NAO Date: 1/12/2018
Checked By: JET Date: 1/12/2018
Checked By: RSS Date: 1/12/2018
Checked By: Date:
Revisions:
1. By: Date:
Checked By: Date:
2. By: Date:
Checked By: Date:
3. By: Date:
Checked By: Date:
90 PERCENT DRAWINGS
NOT FOR CONSTRUCTION
Structural
Geotechnical
SA-1-OW Hydrology & Hydraulics
www.stephensengineers.com
Phone (603)772-1417; Fax (603)772-1418
,
Phone (978)988-2115; Fax (978)988-2117
AD-1
Project: Sheet 1 of 114
Number: 052-15-022
Name: Old Shepard Street Dam
SA-C1 Repairs, Canton, MA
Subject: Figure 5 - Exploration
Location Sketch
The drawings, regardless of format (paper, electronic or other media) are
Stephens Associates Consulting Engineers, LLC (SA) has prepared this
drawing specifically for its client for application to the named Project as
conceived at this time. Any modification or reuse of the drawings, or elements
of them, without the express written consent of SA is strictly prohibited. Your
software may not properly translate all information transmitted. SA shall not
be responsible for any translation errors nor for reuse or misuse by SA's
Client, nor for any use, reuse or misuse by third parties.Source page 34
Graphic Scale
0 5 10 ft.
Original Drawing Size = 22 x 34 in.
OWNER
TOWN OF CANTON, MA
CLIENT
TOWN OF CANTON, MA
By: NAO Date: 1/12/2018
Checked By: JET Date: 1/12/2018
Checked By: RSS Date: 1/12/2018
Checked By: Date:
Revisions:
1. By: Date:
Checked By: Date:
2. By: Date:
Checked By: Date:
3. By: Date:
Checked By: Date:
90 PERCENT DRAWINGS
NOT FOR CONSTRUCTION
Structural
Geotechnical
Hydrology & Hydraulics
www.stephensengineers.com
Phone (603)772-1417; Fax (603)772-1418
Phone (978)988-2115; Fax (978)988-2117
Project: Sheet 1 of 114
Number: 052-15-022
Name: Old Shepard Street Dam
Repairs, Canton, MA
Subject: Figure 6 - Model
Embankment Section
The drawings, regardless of format (paper, electronic or other media) are
Stephens Associates Consulting Engineers, LLC (SA) has prepared this
drawing specifically for its client for application to the named Project as
conceived at this time. Any modification or reuse of the drawings, or elements
of them, without the express written consent of SA is strictly prohibited. Your
software may not properly translate all information transmitted. SA shall not
be responsible for any translation errors nor for reuse or misuse by SA's
Client, nor for any use, reuse or misuse by third parties.Source page 35
Propet: Num ber: 052-15-022 Sheet: Lof1
Name: OW Shepard StreetD am Repairs
0 rginalW ork: Canton,M assachusetts
By: NAO Date: _1242016 ND No.MAQ3104, S tate No.6-11-50-2
Checked By: __JET Os ~ Date: _1242016 Subpet: Figure 7 -D rainage Area
SILK MILL
= POND
: y DRAINAGE
7 UPPER
“ff? MASSAPOAG
NOTES: . “Sc
1. BASE MAP COPYRIGHT ©1998 TOPO!, INC. GRAPHIC SCALE
2. DESIGNATIONS OF SUBDRAINAGE AREAS USED IN HYDROLOGIC AND 1 MILE
HYDRAULIC MODELING DESCRIBED IN SA’S PHASE Il REPORT FOR
SHEPARD POND DAM, DATED FEBRUARY 28, 2011.
Copyright © 2016 Stephens Associates Consulting Engineers, LLC Stephens Associates
Consulting Engineers
isi Insightful, Cost-Saving Structural
Revispns: Solutions for Buildings Geotechnical
By: Date: and Infrastructure iy drology & Hydraulics
www stephenseng heers.com
60 Northrup Dr., Brentwood, NH 03833; Phone (603)772-1417; Fax (603)772-1418
668 Main Street, Ste. 250, Wilmington, MA 01887; Phone (978)988-2115; Fax (978)988-2117
By: Date:
[Original embedded text, retained for comparison]
Project: Number: 052-15-022 Sheet: 1 of 1
Name: Old Shepard Street Dam Repairs
Original Work: Canton, Massachusetts
By: NAO Date: 12/6/2016 NID No. MA03104, State No. 6-11-50-2
Checked By: JET Date: 12/6/2016 Subject: Figure 7 - Drainage Area
Structural
Revisions: Geotechnical
By: Date: Hydrology & Hydraulics
www.stephensengineers.com
By: Date:Source page 36
REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
CANTON, MASSACHUSETTS
TABLES
SA No. 052-15-022 1/12/2018 Page T-1 of 3Source page 37
Project: Number: 052-15-022 Sheet 1 of 1
Name: Old Shepard Street Dam Repairs, MA03104
Original Work: Canton, Massachusetts
By: NAO Date: January 12, 2018 Subject: Table 1 - Impoundment and Groundwater Observations
Checked By: JET Date: January 12, 2018
Water Elevations1 (ft)
Date Time
Pond2 SA-1-OW 3 SA-2-OW 3
2/17/2016 5:00 PM 113.5 108.5 110.6
2/29/2016 12:00 PM 113.44 108.3 109.2
3/10/2016 11:00 AM 113.3 108.0 109.0
11/15/2017 10:00 AM 112.55 108.0 109.0
NOTES:
1. Elevations relative to NGVD 1929.
2. Silk Mill Pond level estimated relative to top of concrete at right spillway
abutment.
3. Observation wells SA-1-OW and SA-2-OW installed February 17, 2016.
4. Pond water level estimated by correlation with flow measured at USGS Gage
01105500 "East Branch Neponset River at Canton, MA" and rating curve for Old
Shepard Street Dam spillway.
5. Town began lowering pond starting about 16 hours before measurement.
Copyright © 2018 Stephens Associates Consulting Engineers LLC
Revisions:
By: Date:
By: Date:
SACE 00-1 (v. 1) 1/00 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 38
Table 2 - Summary of Geotechnical Laboratory Test Results and Estimated Hydraulic Conductivity
Old Shepard Street Dam Repairs, MA03104, Canton, Massachusetts
6,7,8
Estimated Vertical Hydraulic Conductivity (k) from Particle
Sample Data Particle Size Data
Size Data
Probable upper
Probable lower
1 2 3 4 5 6
bound of
Boring Sample Sample Generalized Percent Percent Percent bound of measured 6
Estimated k (cm/s) measured k = 3
No. No. Depth (ft.) Stratum Gravel Sand Fines k = 1/3 of estimated
times estimated k
k (cm/s)
(cm/s)
SA-1-OW SS-3 4 - 6 ft Fill 21 62 17 2E-04 5E-04 1E-03
SA-1-OW SS-5A 8.5 - 8.7 ft. Fill 14 67 19 4E-04 1E-03 4E-03
SA-1-OW SS-7 12 - 14 ft. Silty Sand & Gravel 38 50 12 5E-04 2E-03 5E-03
SA-2-OW SS-4 6 - 8 ft. Fill 10 70 20 2E-04 5E-04 2E-03
NOTES:
1. Sample depth values are depths over which split spoon samples were obtained. A representative sample for laboratory testing was taken from each split spoon.
Refer to individual laboratory data sheets and boring logs for further sample information.
2. Generalized stratum corresponds to strata described in SA's Repairs Design Report.
3. Gravel is defined as particles 0.187" (No. 4 seive) to 3" in diameter. Percent gravel is the percent of material by weight within this range of particles sizes.
4. Sand is defined as particles 0.187" (No. 4 sieve) to 0.003" (No. 200 sieve) in diameter. Percent sand is the percent of material by weight within this range of particles
sizes.
5. Fines are defined as particles smaller than 0.003" (No. 200 sieve) in diameter. Percent fines is the percent of material by weight smaller than this particle size.
6. Note that permeability was not measured. The Kozeny-Carman formula estimates hydraulic conductivity of saturated/submerged soils based primarily on grain-size
distribution and void ratio. The references note that values estimated with the Kozeny-Carman formula are usually within the range of 1/3 to 3 times measured values.
Permeability of soils above ground water table not estimated by correlation with grain size distribution because partially saturated permeability will likely differ from
saturated permeability estimated by Kozeny-Carman formula.
7. The references note that nearly all laboratory measurements used to validate the Kozeny-Carman Formula were based on vertical hydraulic conductivity. Horizontal
permeability could differ.
8. Refer to SA's Design Report for discussion of hydraulic conductivity estimate limitations.
052-15-022 Sheet T-3 of 3 1/12/2018 www.stephensengineers.com 668 Main Street, Wilmington, MA 01887 (978) 988-2115Source page 39
REPAIR DESIGN REPORT
OLD SHEPARD STREET DAM
CANTON, MASSACHUSETTS
APPENDIX A
1956 PLANS,
SUBSURFACE EXPLORATION LOGS
GEOTECHNICAL LABORATORY TEST RESULTS AND
CONCRETE LABORATORY TEST RESULTS
SA No. 052-15-022 1/12/2018 Page A-1 of 28Source page 40
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