EPA-600/2-7Wi-02k
March 1978
Environmental Protection Technology Series
EVALUATION OF TRENCHLESS SEWER
CONSTRUCTION AT SOUTH BETHANY BEACH
DELAWARE
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-600/2-78-022
March 1978
EVALUATION OF TRENCHLESS SEWER
CONSTRUCTION AT SOUTH BETHANY BEACH, DELAWARE
BY
Lee J. Beetschen
William C. Henry
Edward H. Richardson Associates, Inc.
P. 0. Box 675
Newark, Delaware 19711
Grant No. S-800690
Project Officer
Hugh Masters
Storm and Combined Sewer Section (Edison, N.J.)
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
This study was conducted in cooperation with
Sussex County Council
Georgetown, Delaware 19947
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Re-
search Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its compo-
nents require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies and to minimize the adverse
economic, social, health, and aesthetic effects of pollution. This pub-
lication is one of the products of that research; a most vital communica-
tions link between the researcher and the user community.
The work described herein was undertaken to evaluate trenchless sewer
construction. Based on an evaluation of the results of the study, using
polyvinyl chloride pipe, this method proved to be less costly, safer and
more rapid than conventional sewer construction.
Francis T. Mayor
Director
Municipal Environmental Research
Laboratory
iii
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PREFACE
The 1976 Needs Survey projected that over 90,000 miles of new sewage
collection pipe, at a cost of approximately $17,000,000,000, would be re-
quired nationally by 1990. In developing these costs, it was assumed that
conventional construction methods would be used to place the sewer pipe.
Obviously, even a minor improvement in these methods could result in a sig-
nificant savings in the overall Construction Grants program and, thus,
ultimately to the individual tax payer.
The research undertaken for this project was directed at evaluating
a new construction method which showed promise of providing such cost bene-
fits as well as being a safer and more environmentally sound means of in-
stalling sewer pipe. At South Bethany Beach, Delaware, a trenchless method
of sewer construction was compared against conventional methods under
similar site conditions. The cost data developed during the course of the
project indicated significant savings through the use of the trenchless
method. In the most conservative form of cost comparison, the trenchless
method was 16 percent less expensive than the conventional.
iv
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ABSTRACT
The purpose of this project was to determine whether the trenchless
method of sewer construction had inherent cost, safety and other advantages
over-conventional methods of sewer construction. Under similar site condi-
tions, the trenchless method was more cost effective than conventional means
based on the actual unit bid price (50%), on complete sewer installation
including manholes, wyes and laterals (16%) and on labor savings (23%).
Eight inch polyvinyl chloride pipe with rubber gasketed joints was used in
the conventional area, whereas eight inch polyvinyl chloride solvent welded
pipe was used for the trenchless method.
The trenchless method does not appear to be suited for urban areas
where significant subsurface utilities exist, nor where rock or boulders
exist in high density. However, the system is uniquely adapted to high
water table areas, and its flexibility of application under varying soil
conditions is wide ranging. The potential for infiltration is significantly
less and, with proper field control, the trenchless method results in less
deflection and horizontal and vertical misalignment. With open trenching
reduced to a minimum, the method is safer than the conventional technique,
particularly where deeper cuts are required. From an environmental stand-
point, the trenchless method provides less disruption to traffic, and re-
presents an improvement in sediment runoff control and noise reduction.
This report was submitted, in fulfillment of EPA Grant No. S-800690,
by the Sussex County Council under the sponsorship of the Environmental
Protection Agency. Work was completed as of December 12, 1977.
v
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CONTENTS
Page
Foreword iii
Preface iv
Abstract v
Figures vii
Tables ix
Exhibits x
Acknowledgements xi
Section
1. Introduction 1
2. Conclusions 2
3. Recommendations 5
4. Description of Site 6
5. The Badger System 13
6. Description of Construction 21
7. Project Evaluation 50
vi
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FIGURES
Number Page
1 General Location Map 7
2 Project Location 8
3 Trenchless and Conventional Construction 10
Areas
4 Badger Minor Dimensions 14
5 The Badger Linkage 15
6 Trenchless Sewer Installation Methods 16
7 Trenchless Sewer Layout 19
8 Badger Minor with Winch Attached 25
9 Outboard Laser Receiver for Horizontal 26
Alignment
10 Badger Foreman and Operator Setting 26
Grade and Horizontal Alignment
11 Pipe Extending into Marsh Prior to 28
Pull
12 Insertion of Pipe into Expander 28
13 Pipe connected Prior to Lowering into 29
Lead Trench
14 Pipe and Plow in Lead Trench (Plan View) 29
15 Pipe and Plow in Lead Trench 30
16 Bucket with Rollers for Vertical 30
Stabilization of Pipe
17 Bucket with Rollers in Place 31
18 Plow Sequence in Progress 31
19 Backing into Manhole Provides Stress 32
Relief and Final Connection
vii
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Figures (Continued)
Number Page
20 Excavation at end of Pull 32
21 Lead Trench Dimensions, Depth Versus 42
Ratio of Depth to Length
22 Method Used to Overcome Easement Problem 47
23 Delta Invert Elevation, Conventional Pipe, 59
Project Average (As-Built)
24 Delta Invert Elevation, Trenchless Pipe, 61
Project Average (As-Built)
25 Effect on Final Invert Elevation of Con- 62
ventional Connection of Trenchless Pipe
to Manhole
26 Delta Invert Elevation, Trenchless Pipe 63
Project Average (Computed)
27 Delta Invert Elevation, Trenchless Pipe, 64
By Month (Computed)
28 Parachute Insertion 66
29 A'ir Blower Hose Insertion 67
30 Placement of Laser Equipment 68
31 Target in Place 68
32 Siting the Target 69
33 Relationship between Vertical Non-compliance 71
and Lateral Density
34 Relationship between Horizontal Non-com- 72
pliance and Lateral Density
35 Groundwater Quality Monitoring Well Locations 74
viii
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TABLES
Number Page
1 Length of Sewer Installed n
2 Rate Data - Project Averages 38
3 Rate Data - Monthly Averages 40
4 Pipe Manufacturer's Lead Trench 41
Dimension Recommendations
5 Pull Lengths 44
6 Summary of Footage Lost to Trenchless 45
Method
7 Contract Prices for Conventional Portion 51
of the South Bethany Demonstration Project
8 Contract Prices for Innovative Portion 52
of the South Bethany Demonstration Project
9 Payment Items for Composite Conventional 55
Gravity Collection System
10 Payment Items for Composite Trenchless 56
Gravity Collection System
11 Groundwater Quality Data - Well No. 1 75
12 Groundwater Quality Data - Well No. 2 75
13 Groundwater Quality Data - Well No. 3 76
14 Groundwater Quality Data - Well No. 4 76
15 Groundwater Quality Data - Well No. 5 77
16 Groundwater Quality Data - Well No. 6 77
17 Groundwater Quality Data - Well No. 7 78
18 Groundwater Quality Data - Well No. 8 78
19 Groundwater Quality Data - Well No. 9 79
20 Groundwater Quality Data - Well No. 10 79
ix
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EXHIBITS
Number Page
1 Field Observation Report ,37
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ACKNOWLEDGEMENTS
The South Bethany Demonstration Project was one segment of a major
construction project to provide sewage collection and transmission in the
Town of South Bethany Beach, Delaware. The firm of E.H. Richardson Asso-
ciates, Inc. provided engineering services on the research and development
phase whereas L. H. Doane Associates, Inc. developed the construction draw-
ings for all the work. The latter firm was also responsible for field in-
spection during construction and was assisted in this activity by inspectors
assigned by the Sussex County Engineer. The cooperation of all private and
public entities was required in order to insure the successful completion
of the project. Therefore, we gratefully acknowledge the assistance pro-
vided by the following persons:
Sussex County Engineer's Office:
William C. Henry - Past County Engineer
William W. Pleasants - Present Acting County Engineer
Dennis L. Moore - Chief of Construction
Willard T. Russell - Inspector
Department of Natural Resources and Environmental Control:
John C. Bryson - Past Secretary
Sussex County Council:
All Council members who served between 1972 and 1977
Edward H. Richardson Associates, Inc.:
Dudley L. Willis - First Project Manager
D. Russell Tatman - Second Project Manager
D. Preston Lee - Third Project Manager
Lee J. Beetschen - Fourth Project Manager
Logan V. Miller - Laboratory Director
Clifford L. Bakhsh - Survey Party Chief
Mayor and Council of Bethany Beach:
All members who served between 1970 and 1977 with particular
gratitude for assistance from:
Dr. Vernon H. Dibeler
Col. Herman P. Goebel
Martin T. Weigand
xi
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L. H. Doane Associates, Inc.:
Nick Lingo - Inspector
Elia Corporation:
Joseph D'Andrea - Owner
Kenneth Seymour - Badger Engineer
Monica Seymour - Badger Operator
Paul N. Howard Company:
Jack Childress - First Project Superintendent
H. T. Thigpen - Second Project Superintendent
Charles Holland - Third Project Superintendent
U. S. Environmental Protection Agency
William A. Rosenkrantz - Director, Waste Management Division
Francis J. Condon - Program Manager
Richard Field - Chief, Storm & Combined Sewer Section
The project was conceived by Mr. Dudley L. Willis, Vice President of
Edward H. Richardson Associates, Inc. who was the first Project Manager
and provided general guidance and high level review through its duration.
Mr. D. Preston Lee, Edward H. Richardson Associates, Inc., was the Project
Manager during the design phase. Mr. Lee J. Beetschen, was the Project
Manager during the construction phase and was responsible for preparation
of this report. Mr. William C. Henry assisted in the preparation.
Special acknowledgement is made to Mr. Hugh Masters, EPA Project
Director for his patience, guidance and overall assistance on this project.
xii
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SECTION 1
INTRODUCTION
GENERAL
Continuing increases in material and labor costs associated with
gravity sewer construction have created an interest in the development
of new construction techniques to temper the impact of the rising costs
on the ultimate user. Except for equipment improvements, contractors
have been using basically the same methods for gravity sewer construction
for decades. The open trenching method with stone bedding, dewatering
and sheeting, as required, has been the standard. The costs associated
with these latter three items can be significant where unsuitable site
conditions are encountered. Furthermore, the potential for injury or
death increases dramatically when deeper excavations are required.
Equipment to install gravity sewers without open trenching was
developed in England in the late 1960's. Continued improvements by the
manufacturer, Badger Systems Plough, Ltd. led to the evolution of the
Badger Minor method which consisted of plowing in solvent welded polyvinyl
chloride (PVC) pipe on a grade established using a laser controlled unit.
Other equipment manufacturers have developed similar systems capable of
placing pipe by the plow-in method. The term "trenchless method" is gen-
erally applied to all such methods.
OBJECTIVE
The general objective of this project was to compare conventional
and trenchless methods under similar site conditions during an actual
gravity sewer construction project. Emphasis was placed on development
of cost information and the quantification and tabulation of methods
used and the rates associated with each construction technique. A com-
plete post construction survey was conducted in order to determine the
quality of the constructed sewers in terms of horizontal and vertical
alignment, infiltration and internal pipe conditions.
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SECTION 2
CONCLUSIONS
1. The trenchless sewer method was determined to be more cost effective
than conventional means as indicated by cost information developed
using three (3) methods:
a. On the basis of actual bid price, the installed costs for 8"
(20.3 cm) polyvinyl chloride (PVC) gravity sewer mains for con-
ventional and trenchless areas were $15 and $9 per lineal foot
($49.21/m and $29.33/m), respectively.
b. On the basis of computed costs for complete PVC sewer installa-
tion including wyes, manholes and laterals, the costs per lineal
foot for conventional and trenchless systems were $23.15 and
$19.39 ($75.90/m and $63.57/m) respectively.
c. On the basis of computed costs for labor only, the differential
was $.84/lineal foot ($2.76/m) in favor of the trenchless method.
2. Comparisons between both techniques with regard to compliance with
invert elevations at the manhole were developed in two ways:
a. In the conventional area, 31% of the "as-built" invert elevations
were within the specified tolerance of .04 feet (1.22 cm). In
the trenchless area, 40% of the invert elevations were within
this specified tolerance.
b. In many cases the trenchless pipe was not pulled to the manhole.
The resulting gap, in the main, which in some cases was as much
as 40 feet (12.2 m), was completed with pipe installed using con-
ventional methods. By computing the projected invert elevation
at the same grade, 75% of these computed invert elevations were
within the vertical tolerance.
3. In most cases, trenchless pipe was rife-barrel straight prior to
the installation of laterals. Due to the construction crew's un-
familiarity with mains installed with this system, the completed
main, i.e. after lateral installation, had poor alignment in both
the horizontal and vertical planes. Using a laser beam, and taking
measurements in 50 feet (15.24 m) increments between manholes, the
following data were derived:
a. Ninety three percent of measurements taken in a test section
in the conventional area were within the vertical tolerance
of .04 feet (1.22 cm). Sixty percent of the measurements were
within the specified horizontal requirement of 0.17 feet
(5.2 cm).
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b. In the trenchless area 78% of the measurements were within
the vertical tolerance, whereas only 50% of the horizontal
measurements were acceptable.
4. Infiltration Tests - Sewer systems in both areas utilized rubber
gasketed precast manholes and water tight manhole inserts. They
differed in that solvent welded joints were used in the trenchless
area and conventional bell and spigot joints with rubber gaskets
were installed in the conventional area. The trenchless mains were
completely dry. In the conventional area, measured flows ranged
between 16 and 44 gallons per inch of pipe diameter per mile of
pipe as taken over a 24-hour period.
5. Closed Circuit Internal Television Inspection - On the basis of
internal inspection, the trenchless and conventional systems were
found to be in excellent condition. Only one off-set joint was
found in the trenchless area, none in the conventional.
6. The presence of subsurface storm conduits, electrical television
and telephone conduits did not significantly hamper construction
activity in the trenchless area.
7. Based on observations made during construction, the trenchless
method has several significant advantages over the use of convention-
al methods:
a. In high water table areas, the need for dewatering is sig-
nificantly less.
b. If adequately planned, the trenchless method results in less
disruption to traffic.
c. Potential for infiltration is significantly less.
d. With proper field control, the trenchless method results in
less deflection and horizontal and vertical misalignment.
e. The system can be used for installing numerous subsurface utili-
ties including gas, water, electric, telephone and cable tele-
vision service. If permitted by local building codes, several
of these utilities could be installed simultaneously as a clus-
ter.
f. The trenchless method represents an improvement in certain envir-
onmental areas, particularly in sediment runoff and noise reduc-
tion.
g. The trenchless method is adaptable to almost all subsurface
soil conditions. The flexibility of application is wide ranging.
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h. The trenchless method is safer than conventional, particularly
where deep trenching is required.
8. The trenchless method has certain disadvantages as compared to the
conventional method most of which can be minimized by proper design
and construction techniques:
a. The method is not suited to the following areas:
1. Urban areas where significant subsurface utilities exist.
2. Where rock or boulders exist in high density.
3. Roadways with rigid paving unless preceded by saw cutting
and removal of sufficient paving to allow placement of the
plow and expander.
b. Extreme care is required on the part of the engineer in the
development of topographical information. The extent of topo-
graphical data required may be greater than for conventional.
The construction rights-of-way must incorporate those proper-
ties where the welded pipe will be positioned prior to pull.
c. Care must be taken in defining the location of subsurface
utilities on the construction drawings.
d. Sewer pipe could not be placed to depths greater than 7 feet
(2.1 m) using the equipment evaluated for this project unless
the upper portion was trenched to a width great enough to
accommodate the Badger. However, other systems are available
which can plow to greater depths without open trenching.
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SECTION 3
RECOMMENDATIONS
This investigation has demonstrated that the trenchless method of
sewer construction is practical and cost effective when compared to con-
ventional means. In addition, the method has inherent environmental and
safety benefits superior to conventional construction. The need for
further research on the method is not required. It is recommended that
those contractors electing to use the trenchless method for sewer construc-
tion be accepted on an equal basis by the U. S. Environmental Protection
Agency in the Construction Grants Program.
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SECTION 4
DESCRIPTION OF SITE
GENERAL
The location of the project was in the Mid-Atlantic region of
the United States, specifically, the coastal area of Sussex County which
is the southernmost of the three counties which comprise the State of
Delaware, see Figure 1. The construction was part of a contract to provide
wastewater collection and transmission facilities for the South Bethany
Sanitary Sewer District.
The South Bethany District, see Figure 2, includes the Town of
South Bethany and the developments of Bay View, Middlesex Beach and Sea
Colony. These are resort oriented communities with less than ten percent
permanent population. Being a resort area, dwellings and businesses are
active from Memorial Day through Labor Day.
Except for the winter of 1976, the winters in this area are generally
mild. The period during which there is frost on the ground is usually
limited to January and February and parts of December and March. Despite
the unusually cold winter during the project period, only nine instances
of daily workday temperatures less than 40° F (4.4° C) were recorded in
the field during the active innovative construction period. The depth of
frost on the ground is normally less than twelve inches (30.5 cm).
The topography of the project area is generally flat ranging
between 2.5 feet (.76 m) to 11.0 feet (3.35 m) above mean sea level.
The ground elevation where the pipelines were installed was mostly
between 3.0 feet (.91 m) and 5.0 feet (1.52 m) above mean sea level.
Most of the project area is described as "Fill Land" in the "Soil Survey
of Sussex County, Delaware" prepared by the United States Department of
Agriculture Soil Conservation Service and issued in May 1974. Based on
field logs maintained during construction, the substrata one foot below
grade consisted of fractional lenses of sand and organic material. This
area previously was marshland through which canals were dredged. The excess
dredge material was used to raise the elevation of the land between and
adjacent to the canals to create additional resort land, suitable for de-
velopment, with boating access to each lot.
Each peninsula created between the dredged canals is generally 230
feet (70.1 m) to 250 feet (76.2 m) in width and the water table closely
follows the tidal changes because of the generally sandy nature of the soils
within the range of the groundwater table. The groundwater level was most
commonly between 2.5 feet (.76 m) and 5.0 feet (1.52 m) below ground level
in most of the project area but was found to be deeper in some areas where
the ground elevation approached 11.0 feet (.91 m) above mean sea level.
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PENNSYLVANIA
MARYLAND
NEW
JERSEY
NEW
! CASTLE
COUNTY
BALTIMORE
DELAWARE
SOUTH BETHANY
Figure 1. General Location Map
7
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LITTLE ASSAWOMAN BAY
MIDDLESEX
BEACH: •'
SOUTH ;
BETHANY
v "8". ••••':•
BAY VIEW
PARK V
Figure 2. Project Location
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This water table data is based on measurements taken throughout the pro-
ject period.
The quality of the surface waters of the canals in the project area
had deteriorated with development to the point where the shellfish activity
was discontinued by State order. Until 1968, there were no regulations
covering on-site wastewater disposal systems and most buildings were equip-
ped with septic tanks many of which were undersized. In addition, many
of these had inadequate leaching facilities which permitted septic tank
effluent to move rapidly to the canals.
Groundwater quality sampling was conducted before, during and
after construction in an attempt to determine the impact on quality of
both conventional and trenchless sewer installation methods. The results
of this study are given in Section 7.
Most of the roads within the project area were constructed of two to
three layers of tar and chips, while a few were loose stone and dirt.
There were no central water or gas pipelines to be avoided but there were a
few storm water culverts and electric services. The most commonly encount-
ered underground utility was telephone service, especially small lines
crossing roads to serve houses. The project area presented generally less
underground interferences from existing utilities than the average, signifi-
cantly developed residential community.
SPECIFIC PROJECT INFORMATION
The project involved the construction of a total sanitary sewage
collection system for the South Bethany Sanitary District. Both conven-
tional and trenchless techniques were utilized to allow a comparative
analysis of these methods under similar site conditions.
Referring to Figure 3, the trenchless method was used in the South
Bethany and Bay View Park areas on the bay side of U.S. Route 1. Conven-
tional methods were used on the ocean side of U.S. Route 1 in South Bethany
and in the landward side of Middlesex Beach.
The overall project involved the construction of approximately
90,000 lineal feet (27,432 m) of gravity collectors, nine lift stations
and three pump stations. The gravity sewers were installed either in the
center of the road or on the shoulder. A tabulation of sewer lengths in-
stalled for each pipe diameter and pipe material is shown in Table 1. A
portion, approximately 5,000 feet (1,524 m), of the polyvinyl chloride pipe
and all of the reinforced concrete and asbestos cement pipe in the innova-
tive area were installed conventionally.
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MIDDLESEX
BEACH
TRENCHLESS
•••': 'LITTUS ASSAWOMAN BAY
Figure 3. Trenchless and Conventional Construction Areas
10
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Table I
Length of Sewer Installed
CONVENTIONAL
Pipe Diameter
8 Inch (20.3 cm)
10 Inch (25.4 cm)
12 Inch (30.5 cm)
15 Inch (38.1 cm)
Total
INNOVATIVE AREA
Pipe Diameter
8 Inch (20.3 cm)
8 Inch (20.3 cm)
8 Inch (20.3 cm)
Total
Pipe Material
Polyvinyl
Chloride
Bell & Spigot
Polyvinyl
Chloride
Bell & Spigot
Polyvinyl
Chloride
Bell & Spigot
Polyvinyl
Chloride
Bell & Spigot
Pipe Length
(Feet)
37,367
659
3,641
7,648
49,315
Pipe Length
Pipe Material (Feet)
Polyvinyl
Chloride
Solvent Weld
Reinforced
Concrete
Bell & Spigot
Asbestos
Cement Pipe
31,720
6,220
2,509
40,449
Pipe Length
(Meters)
11,389
201
1,110
2,331
15,031
Pipe Length
(Meters)
9,668
1,896
765
12,329
The presence of manmade lagoons and natural water ways imposed
a significant limitation on the design of the gravity collection system,
particularly in the trenchless area. Changes in direction of flow are
normally limited by designers of collection systems, but at this location
11
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could not be avoided, thereby resulting in a significant number of short
mains. More than 96 percent of the trenchless pulls were less than or
equal to 400 lineal feet (122 m).
The trenchless equipment used on this particular project had a
depth limitation of 7 feet (2.13 m) below grade. The average depth of
installation in the trenchless area was 4.0 feet (1.22 m) below grade
and the maximum installation depth was 6.5 feet (1.98 m).
12
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SECTION 5
THE BADGER SYSTEM
HISTORY OF THE BADGER
The innovative part of this construction contract was approached
with the position that the project should take advantage of any innova-
tive construction equipment having the potential of installing sanitary
sewers with sufficient accuracy at less cost and environmental distur-
bance than with conventional means. Although other types and brands of
equipment were pointed out in the Special Provisions of the contract
specifications, the lowest responsible bidder proposed the use of the
Badger Minor. Discussion in this report is, therefore, limited to the
Badger machinery since comparable information on the other types and brands
of equipment was not developed. However, based on a review of information
gathered during the initial phase of the project, there appears to be other
equipment capable of giving similar performance.
The first Badger Minor was built by the Badger Systems Plough Ltd.
of York, England and placed in operation in 1965. The Badger Minor Plow
machine was built on a British manufactured International Model BTD20
crawler tractor fitted with a 135 H.P. Rolls Royce diesel engine. Refer-
ring to Figure 4, the tractor is about 18 feet (5.49 m) long and the over-
all length of the unit with the plow attachment is 30 feet (9.14 m). The
working weight of the total Badger Minor plow machine is about 25 tons
(22.7 metric tons). The tracks are 32 inches (81.3 cm) wide resulting in
a ground pressure of 12.2 psi (.857 Kg/cm ). The overall width of the
complete unit is 10'2" (3.10 m) and overall height is 10'6" (3.20 m).
The component parts of the Badger Plow linkage are identified in
Figure 5. According to the manufacturer, the principles and design of
the linkage insure that the forces on the tractor result in the ground
pressure beneath the tracks remaining nearly uniform in operation under
a wide range of conditions. This reduces any tendency for the plow tractor
to nose down or up, thereby enabling the tracks to develop maximum pull
while minimizing surface disturbances.
The Badger Minor was used for installation of agricultural drainage
and irrigation piping 6 inches (15.2 cm) or less in diameter generally in-
stalled from 3 to 4 feet (.91 - 1.22 m) below grade. This work was done
first by the "pull in" method and later by the "feed down" method using
flexible pipe. The "feed down" equipment was also made to accommodate
single and multiple simultaneous installations of electric cables, tele-
phone ducts, gas and other utility conduits. See Figure 6 for illustration
of the two aforementioned installation methods.
The "feed down" method utilizes the Badger blade with a chute
attached to the rear. Flexible-plastic pipes or cables are then fed
down through the chute as the plow machine moves forward. Small dia-
13
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10
"CM
_i
"o
PLAN
ELEVATION
Figure 4. Badger Minor Dimensions
14
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BLADE ARM
ROLLER
SUPPORT
PARALLELOGRAM
LINKAGE
HYDRAULICS
HOUSING
PIPE
EXPANDER
Figure 5. The Badger Linkage
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PULL IN METHOD
BADGER MINOR
FEED DOWN METHOD
BADGER MINOR
PULL IN METHOD
SITEHUSTLER
BADGER MAJOR
Figure 6. Trenchless Sewer Installation Methods
16
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meter flexible pipe and cable are usually uncoiled from a reel mounted
on the Badger tractor. Drainage pipe with less flexibility is pre-
assembled in long lengths ahead of and parallel to the Badger and fed
down through the chute. To improve drainage characteristics, gravel may
be installed simultaneously through a hopper attached behind the pipe
chute.
In order to pull in larger pipes at a deeper depth, the first Badger
Major was built and placed in operation in 1966. Although it is built on
the same BID 20 tractor, as can be seen from Figure 6, the Major is a much
larger machine overall and designed to obtain all of its draw bar pull and
steering through cables attached to the Sitehustler which serves as an
mobile winch machine. The Badger Major has a depth capability of 10 feet
(3.05 m) as opposed to approximately 7 feet (2.13 m) for the original
Badger Minor. Several who were involved in this project witnessed, in Eng-
land, a 328 foot (100 m) length of 22 inch (56 cm) diameter PVC interceptor
sewer pipe installed at a depth of 9 feet (2.74 m) below grade with a
Badger Major.
Because of the high cost of the Badger Major Equipment, about
$350,000 (fc 150,000) in 1974, the Badger Minor linkage has been increased
in depth capability and strength and used with a winch equipped tractor to
install pipes up to 12 inch (30.5 cm) diameter and to depths of 7.5 feet
(2.29 m). This new machine is called the Badger Mark II which is avail-
able today to readily attach to Caterpillar, International, Allis-Chalmers
and other brands of crawler tractors of suitable weight and power in their
standard manufactured form.
When the soil conditions, depth of installation, length of pull and/or
pipe diameter require drawbar pull approaching the limit of the plow trac-
tor, the manufacturer advises that pulling assistance should be added from
another tractor. This assistance may be derived by a towing tractor or a
stationery unit with a suitable winch and cable attached to the plow trac-
tor.
The manufacturer of the Badger equipment has suggested a number of
techniques to make longer pulls and achieve greater depths without dis-
turbing the accuracy of the installation. One technique utilized in this
project was pre-ripping the ground close to or at the desired installation
elevation without the pipe attached. This method reduced the amount of
drawbar pull required during pipe installation and also provided a means
of checking for unknown buried obstacles such as large logs or rocks.
Where sticky subsoil is encountered, pumping water down through
the plow blade to the expander serves to lubricate the pipe and ease
its installation. In addition, where space and surface conditions per-
mit, the ground level can be lowered with bulldozers or pans to in-
stall pipes deeper than 7.5 feet (2.29 m) .
17
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The maintenance of horizontal and vertical alignment has also
undergone several evolutionary steps. Grade control was first accomplished
by a technician sighting a target on the plow through a level set at the
design slope of the pipe utilizing a radio linkage connected to operate
the hydraulic grading valve on the plow machine. This method of control
was later changed to an electrical cable link and the technician, sighting
a target on the plow through a level, controlled the elevation of the pipe
being installed by a hand held box with switches which could move the
hydraulic cylinders on the plow machine.
The currently recommended and most refined grade and steering con-
trol is accomplished with a laser beam rotating in a plane set at the
design slope of the pipe which is being installed. Another laser beam
oscillates in a vertical plane parallel to the alignment of the pipe. The
arrangement of the Badger machinery and laser equipment is illustrated in
Figure 7.
The Badger Minor was first used in Delaware for sanitary sewer
installation for placing 8 inch (20.3 cm) diameter polyethlene pipe in a
private development in the Town of Bethany Beach, very close to and
slightly north of the project site. This effort involved about eight
pulls and amounted to approximately 1200 feet (365 m) of pipe installed.
Vertical control was achieved by a technician who, sighting a target on
the plow through a level set at the design slope of the pipe operated the
machine's solenoid control valves via an electrical cable. Numerous unex-
pected underground obstacles were encountered, the positions of which had
not been accurately documented. These obstacles, consisting of water
pipes and electric cables, were either removed or grades were adjusted to
accomodate them.
The next project involved the installation of more than 5000 feet
(1525 m) of 8 inch (20.3 mm) diameter sanitary sewer in a private mobile
home park. The utilities installed were solvent weld joint PVC sewers
and smaller diameter water lines. This installation used the same grade
control system for the sewers as in the aforementioned project. Some
pulls were made in a cleared path through a wooded area and preripping
was done to clear any heavy roots which might disturb the uniformity of
invert elevation.
Before the contract for 60,000 feet (18,288 m) for Bethany was adver-
tised, it was decided to let a contract for a small segment of the work
to familiarize potential bidders with the Badger system. This pilot con-
tract involved about seven pulls of various lengths of 8 inch (20.3 cm)
diameter PVC pipe between 200 and 300 feet (61 - 91 m) in length with
solvent weld joints. This contract was the first local project with the
Badger Minor utilizing a laser beam for vertical control. The laser de-
tector was used to trigger indicator lights which signalled the Badger
operator to actuate the plow's hydraulic vertical control manually.
18
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Grade
Rotating Laser Beam
(Vertical Control)
Slope of Sewer•
Elevation
• Laser
Oscillating Laser Beam in Vertical Plane
(Horizontal Control)•
7
01 ' "HU-S*
/ • £r~ir
JLJJLL
TTTT1
EL
jy — ^ a
i~ Pipe Lead \ Badger f
Trench-^ Minor -J
Plan
M n i
1 1 MI r
-Ul
rrn
^— Deadman
Figure 7. Trenchless System Layout
-------
Since the bids received for the Bethany sewer project contained
prices for innovative construction that were higher than conventional
prices, the innovative work was transferred to the South Bethany sewer
project. Advertisments for bids for the Bethany sewers in newspapers of
major nearby cities also attracted bidders who did not witness the pre-
viously mentioned pilot contract. Therefore, an adequately advertised
single demonstration pull was made of about 300 feet (91 m), simply to
familiarize prospective bidders with the Badger technique. No changes
were made in the equipment or alignment control.
The most significant advance in the vertical and horizontal control
equipment for the Badger was introduced when the contruction began in
the South Bethany Sewer District. At this point, the laser receiver was
directly wired to control the solenoid valves of the grading ram to
automatically control the pipe invert elevation. The laser beam, rotating
in a plane set to the design slope of the pipe, was initially geared to
rotate at five revolutions per second. Each time the laser beam hit the
sector of the receiver above or below the ongrade sector, it would
trigger a pulse flow of hydraulic fluid to the grading ram.
Since this arrangement did not produce a suitably rapid correction
in pipe invert elevation in relation to the Badger plow travel speed,
the laser beam rotation was increased to ten revolutions per second.
This modification apparently solved the problem because no further in-
creases were made in the rotation speed of the laser beam used for
vertical control.
This increased use of laser control was extended to improve horizon-
tal alignment at the beginning of the South Bethany sewer construction.
A second laser beam was added which was oscillating in a vertical plane
offset from and parallel to the design alignment of the pipe. The two
laser receivers, one fore and the other aft, were attached in a horizontal
attitude at different heights with the "online" sectors of the receivers
set the same distance from the center line of installation on the same
side of the Badger machine. These laser receivers triggered indicator
lights which the Badger operator used as a guide in steering the machine.
The reason for setting the forward horizontal control receiver higher
than the aft receiver was to prevent the aft receiver from interfering
with the beam transmitting signals to the forward receiver. The other
significant refinement needed for the laser control system involved its
stability. Heavy equipment or vehicles moving near the tripod on which
the laser transmitter was mounted disturbed its sensitive calibration.
Moderately strong winds were also a problem as well as thermal expansion
from the sun which moved the paving under the tripod. This problem was
solved by the addition of an automatic leveling attachment to the laser
transmitter.
20
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SECTION 6
DESCRIPTION OF CONSTRUCTION
GENERAL
The trenchless method of sewer construction and, in particular
the Badger system used for this project, involves many techniques
which vary significantly from those used when sewers are installed
conventionally. With the trenchless technique, site preparation,
and dewatering are reduced to a minimum. The nature and size of
project construction crews also differ significantly.
This chapter will provide a definition of personnel requirements,
set forth the differences in the two construction techniques, describe
improvements made to the Badger system during construction, provide a
summary of technical data derived from records maintained by onsite
inspectors and, finally, develop a tabulation of suggestions which may
be incorporated by other designers interested in preparing plans and
specifications for projects using the trenchless technique.
COMPARATIVE CONSTRUCTION TECHNIQUES (General)
Construction Crew Definition
The descriptions provided herein represent average crews used by
the general and subcontractors on this particular project. They may
vary significantly from one regional location to another depending upon
contractor preferences, labor market variations, etc. Furthermore, the
general contractor on this project employed three conventional pipe
installation crews simultaneously, which provided him with the flexi-
bility of sharing certain skilled labor crafts between the three crews.
The conventional crew was made up of a foreman, three heavy equipment
operators, one pipe layer, three laborers, one engineer and one engineer's
helper. The functions of individual personnel were as follows:
Foreman - Supervise Installation
Equipment Operators
Backhoe Operator (1) - Trenching
Front End Loader (1) - Site preparation and backfill
Dump Truck Operators (1)- Hauling select fill and gravel
and disposing of unsuitable
materials.
Pipe Layer - Inspection for suitability of grade,
and making joint connections.
21
-------
Laborers
Tailman (1) - For ramming home pipe.
Others (2) - For carrying pipe, lubricating joints
and tamping backfill.
Engineer - To establish grade and alignment with
laser equipment.
Engineer's Helper - To assist engineer.
The Badger crew consisted of a foreman, two equipment operators and
two laborers. The responsibilities of each individual were as follows:
Foreman - Supervise construction, set up laser
to establish grade and provide gener-
al instructions to trenchless sewer
equipment operator.
Equipment Operators
Trenchless (1) - Operate Badger equipment
Backhoe/Front - Dig lead trench, excavate for
End Loader (1) disconnection, backfill.
Laborers (2) - To solvent weld pipe, string out, etc.
In both the conventional and trenchless areas, the same number of per-
sonnel were utilized for crews performing in the following construction
activities:
Stakeout
Manhole Construction
Lateral Construction
Paving
Construction Elements
Stakeout—In both the conventional and the trenchless areas, stakeout
was limited to establishing horizontal and vertical alignment at each
future manhole location.
Site Preparation—The bulk of conventional and innovative sewer
construction took place either in nonpaved shoulders or in areas where
the paving was limited to surface treatment with asphalt and stone. In
the conventional areas where surface treatment existed, site preparation
consisted of removing this material with a front end loader and stock-
piling it for future disposal. In the trenchless area, no site prepara-
tion was required.
22
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Dewatering—As was noted in Section 4, a persistent high water
table was encountered at all times during the construction period.
Watertable depths varied between 0.5 feet and 2.5 feet (0.15 to 0.76 m)
from grade. In the conventional area a system of wells was jetted into
the water bearing strata on one side of the proposed sewer trench and
connected with a header pipe and pump. Dewatering in the trenchless area
was limited to the use of a submersible pump on two occasions for lead
trenches.
Open Trenching—Because of the shallow nature of the sewers de-
signed for the South Bethany Demonstration Project, a backhoe was suit-
able for open trenching, for mains and laterals with or without sheet-
ing, in the conventional area. Excavated material was stock piled on
one side of the trench. In the trenchless area, open trenching was re-
quired for the lead trench, for disconnecting the pipe after the pull
and for saddle wye and lateral installation.
Foundation—In the conventional area, 0.5 feet (0.15 m) of Class I
bedding material was to be provided for all PVC sewer. Class I was de-
fined in the specifications as 1/4" to 3/4" (0.64 to 1.90 cm) angular grad-
ed stone, coral, slag, cinders, crushed stone or crushed shells. About
midway through the project, this requirement was deleted except where un-
stable conditions such as mud or water were encountered. In the trenchless
area, Class I bedding was provided on a limited basis to stablize end of
pipes when there were significant delays between pipe pull and manhole
installation. In addition, bedding was sometimes used to stabilize the
main sewer during open trenching for saddle installation and when con-
ventional methods were used to complete the connection of Badger pipe
to a manhole.
Pipe Installation—In general, in the conventional area, pipe was
installed as outlined below. The work elements are presented in the
order in which they took place.
1. Set up a laser for vertical and horizontal alignment.
2. Transfer of pipe to trench.
3. Clean bell and spigot.
4. Lubricate gasket.
5. Line up pipe and ram home.
6. Check alignment.
7. Tamped backfill in lifts.
8. Manhole installation.
9. Open trench for lateral connection to wye.
10. Backfill.
11. Paving.
In the trenchless area, the following steps were required for
the installation of a complete sewer system. A more detailed descrip-
23
-------
tion is provided later in the section.
1. Identify and stakeout utilities.
2. Lay out pipe.
3. Clean and solvent weld joints.
4. Drill hole in pipe.
5. Set up laser.
6. Excavate lead trench.
7. Position pull equipment and deadman if necessary.
8. Preplow.
9. String out pipe, within the construction easement, behind
the trenchless installation equipment.
10. Connect pipe to expander.
11. Pull pipe.
12. Check elevations.
13. Excavate and disconnect the pipe.
14. Place gravel under disconnected pipe end.
15. Open cut for manholes and install.
16. Open cut for laterals.
17. Cut hole for saddle.
18. Apply solvent cement, allow for curing and install saddle.
19. Install lateral.
20. Repair utilities.
21. Paving.
The utility repair took place in a sequence which was dependent upon the
urgency of facilitating the repair.
THE BADGER SYSTEM (Specifics)
The Badger foreman and the operator of the trenchless equipment
are specially trained individuals who must be intimately familiar
with the trenchless technique. The backhoe operator and the two laborers,
which make up the balance of the crew, need no additional skills beyond
those required for conventional construction.
The two laborers act as a unit almost independent of the other three
individuals of the crew. Their main responsibility is to insure that
sufficient solvent welded pipe is available to the trenchless crew for
each pull. Their work, which takes place simultaneously with that of the
Badger crew, involves no unique skills and, therefore, requires no further
discussion.
Figure 7 (page 19) provides a plan view of the Badger system which
supports the following narrative.
While the labor crew is solvent welding and stringing out sufficient
pipe to meet daily requirements, the Badger unit is brought into approxi-
mate alignment. If the foreman anticipates traction problems, a deadman
24
-------
is located approximately thirty feet (9.14 m) beyond the end of the pull
to allow room for the Badger once the pull is completed, see Figure 8.
Figure 8. Badger Minor with winch attached.
The foreman then sets up the laser approximately 6.5 feet (1.98 m)
off the centerline of the proposed sewer line, which is the approximate
distance between the center of pipe and the outboard receivers on the
Badger Minor. The laser receiver is shown on Figure 9. The Badger oper-
ator assists the foreman in adjusting the laser to the appropriate slope
and establishing invert elevations. Using a stadia rod, laser receiver
and transceiver at the far end of the pull, the operator communicates with
the foreman who remains at the laser and makes the required corrections
until the desired slope is achieved, see Figure 10.
When using the trenchless method, care must be taken to avoid undue
stresses in the pipe as it is being pulled into the ground. To minimize
these stresses, a lead trench was constructed, the length of which was
to increase in direct proportion to the depth of cut. The width of such
trench is dependent upon the diameter of the pipe and the equipment used
to offset the uplifting tendency of the pulled pipe.
The plow, without the pipe being connected, was routinely pulled
along the sewer route prior to an actual pull sequence. The Badger
equipment operator normally required at least one preplow subsequent to
-------
Figure 9. Outboard Laser receiver for horizontal
alignment.
Figure 10. Badger foreman and operator setting
grade and horizontal alignment.
26
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the actual installation of pipe for the following stated reasons:
1. To remove any subsurface obstacles in the path of the plow.
2. To equalize ground pressure and reduce drag on the pipe.
3. To insure maintenance of horizontal and vertical alignment
during the pull.
More than one preplow was required depending upon the depth of the
plow and the hardness of the ground being plowed. The number of pre-
plows required is totally dependent upon operator judgment. Before
or during the preplow, the pipe is laid out behind the point of inser-
tion. Figure 11 shows a length of pipe extending into a marsh, over a
manhole and then into the lead trench.
.-sj' "*'"
Once?the preplows are completed, a coupling is connected to the
predrilled pipe and it is dragged forward for insertion in the expander,
see Figure 12. Connection is accomplished simply by placing a pin through
the expander, and the hole in the coupling and inserting a removable clip
in the end of the pin. The operator selects the expander size based on
the ground conditions encountered. In cohesive soils, one uses an expan-
der with a diameter closer to the size of the pipe being pulled to prevent
floating of the pipe in the hole created by the expander. A final check
of laser equipment is performed by the foreman prior to his authorizing the
pull.
The plow blade, with pipe connected, is lowered into the trench
whereupon the backhoe operator lowers the bucket onto the pipe. Refer
to Figures 13, 14, 15, 16 and 17 for a pictoral sequence of these opera-
tions. The bucket has rollers connected to the base so as not to damage
the pipe while still preventing uplifting.
After the pipe has been pulled through the trench, Figure 18, and the
expander reaches the point at which the next manhole will be located, the
pipe is backed into the lead trench manhole, see Figure 19. The success
of the pull is determined by checking the invert elevation of the pipe
using a point on the linkage which is at a predetermined distance from
the invert. If thevelevation is within the specified tolerance, the
foreman authorizes excavation of the pipe to allow disconnection of the
pipe from the Badger expander, see Figure 20. Prior to backfilling, stone
is placed under the pipe to provide suitable bedding to insure that the
elevation will be maintained until the manhole installation crew arrives.
If the tolerance is not met, and field conditions allow, the foreman
can instruct the operator to pull the sewer out. In cohesive soils, care
must be taken to reach a decision promptly, otherwise the soil friction
resulting from stabilization of the expanded pipe tunnel may preclude re-
moval. If this occurs, the operator may disconnect and plow through the
off-grade pipe.
Saddle wyes are installed at a later date by open cutting at the
approximate lateral location, dewatering if required, cutting a hole in
27
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Figure 11. Pipe extending into marsh prior to pull,
Figure 12. Insertion of pipe into expander.
3
-------
Figure 13. Pipe connected prior to lowering
into lead trench.
1
.*»<•». *
Figure 14. Pipe and plow in lead trench (Plan View)
l
-------
*/•
.;--/•••:
' '' £fF~ ' .It-
Figure 15. Pipe and plow in lead trench.
Figure 16. Bucket with rollers for vertical
stabilization of pipe.
-------
Bucket with rollers in place.
n
Figure 18. Plow sequence in progress.
31
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Figure 19. Backing into manhole provides stress
relief and final connection.
Figure 20. Excavation at end of pull.
-------
the pipe, cleaning and drying the pipe, applying the solvent, strap-
ping on the saddle and allowing for the appropriate curing time before
backfill. In the majority of lateral installations, dewatering was not
required. The remaining construction activities, such as installation
of laterals and repaving, required techniques which duplicated those
of conventional construction.
TECHNIQUE IMPROVEMENTS
There were many problems encountered during the development stage,
which preceeded actual construction, and also during the construction
phase. Sufficient doubts were raised about the new system so that the
contract specifications included a performance clause as follows:
A. "The purpose of a performance contract is to determine if
the contractor with the lowest bid electing to use the
innovative method of sewer construction can demonstrate that
he is capable of complying with the requirements of these
specifications. The demonstration shall consist of actual
sewer construction using the innovative method."
B. "The performance contract shall utilize the innovative method
exclusively. A minimum of 1500 lineal feet of eight inch (8")
sewer main, manholes, 6" connections, complete with all re-
storation and testing shall be constructed within the project
limits at a location chosen by the contractor and approved by
the engineer."
C. "If, at the completion of this performance contract, the con-
tractor has not satisfactorily accomplished installation of
sewers by the innovative method as determined by the specifi-
cations and interpreted by the engineer, the remaining part
of the contract shall be completed by the conventional method
of sewer installation."
There were significant deviations between the design and actual
invert elevations on most of the sewer lines installed under the per-
formance contract. However, the installation by the contractor was
deemed adequate for the following reasons;
A. All lines were lamped and at least three quarters of the
barrel was observed in each line.
B. No infiltration was observed in any of the lines.
C. The hydraulic capacity of all sections was adequate for the
anticipated flow in each line.
D. With the exception of 342 lineal feet (104 m), the full pipe
velocities were always in excess of two feet per second
(.69 m/sec) as determined using an "n" value of 0.011.
33
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A summary of problems encountered during the entire project and
solutions derived is presented below-
Problem
Stresses in the pipe caused an uplifting of the pipe for approximately
twenty feet past the lead trench in the direction of the pull.
Solution
The first attempt to solve the problem was by increasing the
length of the lead trench in order to reduce the downward slope as
the pipe entered the expander tunnel. Although partially success-
ful, dewatering was used in the next attempt as it was felt that
the buoyancy factor which remained after stress relieving of the
pipe may have been significant enough to cause the uplifting.
This modification proved unsatisfactory. The problem was finally
resolved by installing rollers on a backhoe bucket and applying a
uniform pressure to the pipe as it was pulled. This method was
used for the rest of the project and was instrumental in the
successful operation of the innovative method.
Problem
The laser beam was unable to maintain grade when temperature changes
caused creep in the surface on which the tripod was mounted.
Solution
The laser was modified by installing an automatic leveling
device.
Problem
The laser became unstable in high winds and the operator was unable
to control vertical and horizontal alignment.
Solution
The subcontractor attempted to erect a temporary windshield, but
this device did not prevent instability. The laser manufacturer
suggested that a new clutch assembly would resolve the problem.
Such a system was installed. No problems were encountered thereafter.
Problem
Ends of pipe did not meet invert elevations when manholes were plac-
ed.
34
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Solution
Stone bedding was placed underneath the pipe to stabilize the
foundation and manhole crews were instructed to begin constructing
manholes promptly after the completion of a pull.
Problem
During the development stage, one of the sewer pipes cracked when
an attempt was made to cut a hole so a saddle could be welded to the pipe.
Solution
The tensile forces built up in the pipe were relieved by moving
the Badger unit backwards thereby relieving the tension.
Problem
When the contractor moved in and opened a trench to allow for saddle
and lateral installation, the unsupported pipe tended to move both verti-
cally and horizontally.
Solution
After undercutting the pipe, a stone bed was provided. This
system was only moderately successfully and the reader is referred
to the "Design and Construction Management Notes" portion of this
Section for suggested improvements to this procedure.
Problem
In clay seams, the pipe tended to float apparently because the cohesive
soil remained open for a substantial period after the pull had been com-
pleted.
Solution
The operator selected a smaller diameter expander to reduce the
size of the pull hole.
Problem
One of the sewers was plowed in off grade in an area where manmade
lagoons precluded pulling the sewer out.
Solution
The Badger operator plowed through the pipe and, after having
made two passes, plowed in a new pipe to replace the one destroyed.
35
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Problem
In areas where utilities, perpendicular to the path of the Badger,
could not be cut by the Badger for safety reasons the cost of open trench-
ing past the utility and then installing sewer by conventional means was
deemed to be excessive.
Solution
The contractor open trenched between the manhole and the
utility and the open trench was used as a lead trench for the
Badger.
PROJECT RECORDS AND DATA
During the performance phase of construction, record keeping by
field inspectors was generally limited to maintaining standard inspec-
tion forms and providing narrative descriptions of problems encountered
and solutions developed. This phase of the work covered approximately
two calendar months beginning in January 1976 and ending March 1, 1976.
During this period approximately 15% of the total lineal footage ultimate-
ly installed by the trenchless method was constructed. The months of
March, April and May were periods of active construction after the trench-
less technique had been refined.
To provide for an accurate data base during this latter construction
phase, a field observation inspection form was developed, see Exhibit 1.
The basic format was developed in draft form and the attached exhibit
represents the final form resulting from recommendations by the field in-
spector. Approximately 85% of project construction is covered by infor-
mation developed in accordance with this form. Records were kept in four
key categories: General; Prepull; Pull; and Post Pull.
Rates For Various Work Tasks
As noted in the field observation form, a great deal of the informa-
tion related to time studies. This information was developed not only
to determine average rates for the entire project, but also to see if
there was a marked improvement in certain work task categories as the
project continued. The latter was expected in view of the fact that, as
a demonstration project, a certain period of time at the outset would be
required to develop the technique.
Project Averages—
Eighty pulls were required to install approximately 23,000 lineal
feet (7010 meters) of 8" (20.3 cm) solvent welded PVC gravity sewer pipe.
Referring to Table 2, the average pull was approximately 285 lineal feet
36
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.Pullf_£_ *A<
Utilities Outi Type
Pag* 2
Sta. *
SooUi Bathany Deaonatratlon
FULD OBSERV1TIOH3
antai
* -^--
Other i Activity
Oat*
T
weather
Air Taap. «-.
Per0onnel_
Bq.uipnent_
Manhour*
I. Qeneral
Street
Equipment Hours
Obstacles Ra.noTed (Deseriptlon and Sketch) Attachment lea Moi-^
Full froa'l
Length! Design_
*•
IT Actual
III. Full
Poll tins f mine. Deadoan used? Tes \f Ho_
Pull uneventful? Tea Ho_t/If no explain In General-1
W. Post Pull
Backup? Tes "^Ko Distance plan laved I ins.
Distance end of pipe saved (Lead Trench) I in*.
Soil between pipe end and sever plug? Tea Mo \*^
Slopes, Elevations
Invert Pay, (ft) Slope (ft/ft)
Design End Pull Design Actual
Paraomwli tXKan and Konloa _Z-_L«bor«ra /Operator! 0 Other
IqulpMnti J^t'uU Badger J^nobor Badger _MJo»b. Loader
II. Pr»-PuU
Pipe Preparatloat f araonnal 2-f Hanbo are Length U
eetup and Kati**liThl *^g Invert! Peraoonel^^tf' Mejhoura /• O
Method! Once Laser la level, elevation readings are taken on the 20'
offset hubs with a specially equipped elevation rod. Using
those readings and information from cut sheets the height of
the Badger grade receiver la oonputed and than the receiver
is adjusted accordingly* See General Contents for change
in procedure. "~~
Dry Runt t of pull* without pipe »^
Lead Trenchi Dewatared? lea VMo Hater Level 0- go^ft.
Solli Type Depth Type Depth
Hathod naad to restore utility •arrlc»«i_
3.
Dimensional
Elevation
Plan
Exhibit 1. Field Observation Report
-------
TABLE 2
00
#of Pulls
Total
Weekly Average
Daily Average
Pull Day Avg.
Average per pull
Hourly Avg.
80.0
7.3
1.46
1.74
1.0
0.18
Laser Setup
Hours
63.25
5.75
1.15
1.38
0.78
0.14
Rate Data
Project Averages
Total Preparation
Hours
153.04
13.91
2.78
3.33
1.90
0.35
Pull Time
Minutes
595.0
54.1
10.82
12.93
7.41
1.35
Pipe Installed
Feet Meters
22,942.0
2,085.6
417.1
498.7
285.7
52.1
6,992.7
635.7
127.1
152.0
87.1
15.9
*Excluding solvent welding and stringout.
-------
(87 meters) and required less than 7 1/2 minutes actual installation time.
The total preparation time, 1.9 hours, excludes the time required for sol-
vent welding and stringing out the pipe which was to be pulled. The daily
averages are based on a five day work week and differ from pull day aver-
ages in that the latter reflects only those days on which actual trenchless
installation occurred.
The general information in Table 3 provides an overall picture of
work task averages during the peak production period but does not ade-
quately reflect rate trends as the Badger crew became more familiar with
site conditions and adjusted their construction techniques accordingly.
Referring to Table 3, monthly averages for the same work tasks and project
rates were developed in order to determine whether or not efficiencies
actually did increase. The time required to set up laser equipment was
reduced from .98 hours in March to .69 hours in May. The total preparation
time, exclusive of solvent welding and stringout, also showed a significant
improvement, being reduced from 2.22 hours at the outset to 1.54 hours dur-
ing the last month of construction activity. The average pull time also
decreased, but this was responsive more to the fact that the average length
of pull decreased from 314 to 288 lineal feet (95.7 to 87.8 m). The rate
of installation in lineal feet per minute, i.e. the forward speed of the
Badger, remained approximately constant at 39 feet per minute (11.9 m/min).
Perhaps one of the most significant factors in reducing total preparation
time was the fact that the subcontractor attempted to plan his work so as
to utilize the same laser position and same excavations for two pulls.
The average lineal feet installed per day, based on a five day week,
increased from 384 lineal feet per day to 480 lineal feet per day (117.0
to 146.3 m per day). Pull day improvements were also seen with an in-
crease from 460 lineal feet per day, on days on which the Badger was oper-
ational, to 524 lineal feet per pull day at the end of the project (140.2
to 159.7 m per day). This is particularly significant in view of the re-
duction of length for each pull as construction progressed.
Solvent Welding and String Out—
During the course of the project it became evident that, with the
limited number of inspectors available, it was virtually impossible to
oversee all construction activities related to the Badger method. Time
records and production rates for the two laborers assigned to welding and
laying out the solvent weld pipe were kept for a four week period. Sol-
vent welding rates varied between 204 lineal feet (62 m) per hour to 620
lineal feet (189 m) per hour with the average being 361 lineal feet (110
m) per hour. The string out times ranged between 325 lineal feet (99 m)
per hour and 1200 lineal feet (366 m) per hour with the average being 650
lineal feet (198 m) per hour. No pattern or trend was discernable in
either case. However, it should be noted that the lower layout rates in
most instances were caused by natural and manmade obstacles which hinder-
ed the crew from placing the pipe.
39
-------
TABLE 3
# of Pulls
March
Total 22
Daily Avg. 1.2
Pull Day Avg. 1.5
Avg/Pull 1.0
April
Total 38
Daily Avg. 1.7
Pull Day Avg. 1.9
Avg./Pull 1.0
May
Total 20
Daily Avg. 1.7
Pull Day Avg. 1.8
Avg./Pull 1.0
Laser Setup
Hours
21.09
1.17
1.41
.98
28.41
1.29
1.42
.75
13.75
1.15
1.25
.69
Rate Data
Monthly Averages
Total Preparation
Hours
48.94
2.72
3.26
2.22
73.35
3.33
3.66
1.93
30.75
2.56
2.80
1.54
Pull Time
Minutes
188
10.44
12.53
8.54
147
12.25
13.36
7.35
Pipe Installed
Feet Meters
6,907
384
460
314
5,766
480
524
288
2,105.3
117.0
140.2
95.7
260
11.82
13.0
6.84
10,269
467
513
280
3,130.0
142.3
156.4
85.3
1,757.5
146.3
159.7
87.8
-------
Prepull Averages—
As noted previously, operator judgment determined the need for more
than one preplow to prepare the subsoil for pipe installation. Based on
inspection reports, the average number of preplows per pull required was
1.3 with the maximum being 4. No preplow was conducted in less than one
percent of the cases.
Lead Trench Dimensions—
Due to concern over the possibility of pipe fracture during the
prepull, the pipe manufacturer was required to provide optimum length
to depth dimensions for the lead trench prior to the initiation of
construction. These dimensions are shown in Table 4. Accurate records
TABLE 4
Pipe Manufacturer's Lead
Trench Dimension Recommendations
Depth of Cover Trench Length
Feet Meters Feet Meters
12.6 3.84
17.7 5.40
21.7 6.62
25.0 7.63
27.9 8.51
30.4 9.27
32.8 10.00
34.9 10.64
36.9 11.25
38.8 11.83
of actual field dimensions were maintained and the data is depicted in
Figure 21. It is apparent from the lack of consolidation of the data
that no trend developed under actual field conditions. In many cases,
lead trench dimensions were minimized in order to reduce repaving costs.
However, in no instance was a pipe fracture developed due to bending.
41
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
.305
.610
.915
1.220
1.525
1.830
2.135
2.440
2.745
3.050
-------
0)
4J
-------
Pull Lengths
The actual construction rates were significantly affected by the
short pull lengths associated with tlhe South Bethany site. Referring to
Table 5, note that 96% of the pulls were 400 feet (122 m) or less with
greater than 50% being 300.feet (?1.5 m) or less. By reviewing the previous
information, it is obvious that longer pulls increased time requirements
in only two significant work categories, i.e. solvent welding and string
out. One can conclude, therefore, that had there been more pulls in the
500 to 600 feet (152;'5 to 183 m) range, the rate of production would have
been significantly improved.
-"?'
..,,, fr j;. ,.i?
Factors Relating1'to tehe Substitution of Conventional for Trenchless Method
Twelve hundred and seventy three feet (388 m) of gravity sewer pipe
which was scheduled to' bd installed by the trenchless method was ultimate-
ly installed conventionally. Table 6 provides a tabulation of reduced in-
stallation amounts in four categories:
1. Physical Obstacles.
2. Pipe Length too Short
3. Solvent fteld Break.
4. Manhole Position Moved.
Approximately 67% of reduction was in the category related to
physical obstacles. The bulk of these obstacles, such as houses, gardens,
bulk heads, waterways were apparent without excavation and reduction in
this category could be minimized in future design projects.
Only 4% of the loss was related to the welded pipe length being
shorter than required.
The next major category constituted 17% of the loss and was related
to manholes being repositioned during construction.
It is significant to note that only 12% of the loss was related to
the failure of the solvent welded joint and that this percentage relates
to only two weld failures. Upon inspection, it was confirmed that these
failures were caused by poor workmanship.
DESIGN AND CONSTRUCTION MANAGEMENT NOTES
The following reference material is specific to gravity sewer
installation by the trenchless technique but may be applicable to the
installation of other utilities such as water mains, sewage force mains
and utility conduits.
Contract Documents
: • .'• -•' ' i •- -.. '•'<•
The key to maximizing the benefits of the trenchless technique
43
-------
TABLE 5
Range
Feet
(Meters)
0
(0
100 -
(30.5 -
200 -
(61.0 -
300 -
(91.5 -
400 -
(122.0 -
500 -
(152.5 -
Length of
Feet
100
200
300
400
500
600
100
30.5)
200
61.0)
300
91.5)
400
122.0)
500
152.5
600
183.0)
Pull
(Meters)
( 30.5)
( 61.0)
( 91.5)
(122.0)
(152.5)
(183.0)
Pull Lengths
Number of Average Length
Pulls Feet
(Meters)
3 93
(28.3)
8 176
(53.6)
29 263
(80.2)
36 338
(103.0)
2 450
(137.2)
1 N/A
Number of
Pulls less
than or equal to*
3
11
40
76
78
79
Minimum Length
Feet
(Meters)
80
(24.4)
143
(43.6)
207
(63.1)
310
(94.5)
404
(123.1)
N/A
Percentage
than or
Maximum Length
Feet
(Meters)
100
(30.5)
200
(61.0)
300
(91.5)
385
(117.3)
495
(150.9)
528
(160.9)
of Pulls Less
equal to
4
14
51
96
99
100
*0ne pull not completed.
-------
TABLE 6
Summary of Footage Lost to Trenchless Method
PHYSICAL OBSTACLES
Length Lost
Feet
10
10
3
32
5
40
55
65
45
20
25
25
25
20
20
20
6
4
5
5
5
45
60
36
40
6
Remarks
M.H. close to bulkhead
M.H. close to bulkhead
M.H. close to canal
Unable to winch on Route 14
M.H. close to bulkhead
Unable to winch on Route 14
ii ii ii n ti it
M.H. close to house
House in way of winch
M.H. close to house
it ii ii ii
M.H. close to gardens
Ground too rough to finish
M.H. close to bulkhead
M.H. close to gardens
Phone cable in way
Subtotal
Length Lost
Feet
12
4
22
38
40
22
14
76
27
40
15
21
18
19
21
24
16
849
PIPE LENGTH TOO SHORT
Pipe jointed short 5
Pipe jointed short 10
Pipe jointed short 6
Pipe jointed short 5
Pipe jointed short 1
Subtotal 52
SOLVENT WELD BREAK
Pipe joint pulled out 105
Subtotal 150
MANHOLE POSITION MOVED
M.H. position moved
M.H. position moved
M.H. position moved
Remarks
M.H. close to house
M.H. close to bulkhead
Ground too rough
900 pair cable in way
n n n ii n
Ground too rough
M.H. close to canal
900 pair cable in way
Ground too rough
M.H. close to canal
loved
loved
loved
ing M.H.
Subtotal
TOTAL
10
12
12
20
26
222
1,273
Pulled to
Pulled to
Pulled to
Pulled to
Pulled to
( 67.7 m)
(388.0 m)
M.H. close to woods
(258.8 m)
Pipe jointed short
Pipe jointed short
Pipe jointed short
Pipe jointed short
Pipe jointed short
(15.8 m)
Pipe joint pulled out
(45.7 m)
existing M.H.
existing M.H.
existing M.H.
existing M.H.
existing M.H.
45
-------
is to take particular care in establishing vertical and horizontal
alignment with relation to surface and subsurface objects to avoid
hindering the production rate or, in extreme cases, requiring the
substitution of conventional techniques. The information provided
herein will be useful to the designer contemplating the use of the
technique for the first time.
If using photogrammetric layouts, approximate locations of sur-
face objects should be field verifiedkand» in cases where^either con-
struction easements for pipe layout is required or where;the Badger system
may induce mobility problems, dimensions should be verified in the field
with reasonable accuracy. If space is critical, the trenchless technique
is normally adaptable to twenty feet (6.1 m) for construction easement
(centered on the sewer) and ten feet (3.05 m) for pipe layout easement.
Existing subsurface utilities and other structures should be
noted in the drawings in detail where possible. Knowledge of their '
location may, in some cases, allow the designer to parallel these utili-
ties and avoid substitution of the more costly conventional method where
a utility crossing could have been avoided.
Where the flexibility exists, the designer should maximize the
length of pull preceeding a change in direction so as to decrearse the
preparation time per lineal feet of sewer installed. As noted pre-
viously, significant savings can be accrued by minimizing the number
of manhours consumed in positioning the laser, opening the lead trench,
etc. „ . . .. _ . - .
The designer may avoid costly delays and a. possible request for
extra payment by checking potential lead' trench positions with relation
to construction easement problems. As an example, referring to Figure
22, Alternate A, it is apparent that the individual on whose property the
lead trench mightjbe placed may voice significant objection toward the' '
removal of shrubs identified- in the topography. If this construction
easement cannot be obtained, as shown in Aite^nate B, the contractor
may have to center 'the lead trench"where he can pull half a length in
each direction. The specification should identify this as anral'ternate
technique available to the contractor which, if employed, will be done
at no additional expense to the Owner. ! '
In a grass roots project where a number of utilities are to be in-
stalled using the frenchless technique, under the same contract, the
designer should position manholes in such a manner as to allow the
lead trench for the Badger -pull, to serve for more than one utility. ;
Under the subsection Technique Improvements, a number of problems
and corrective actions were identified. On the basis of the experience
derived during this project, it would appear that specifications for the
trenchless technique require cautionary instructions which are unique to
46
-------
Lead
Trench
Shrubs
Manhole
Direction of Pull
ALTERNATE A
Manhole
Shrubs"
Lead Trench
Direction
of 2nd. Pull
Direction
of 1st. Pull
ALTERNATE B
Figure 22 Method used to overcome easement problem
47
-------
the method. The inclusion of these instructions, in a wording accept-
able to the particular designer, will provide the necessary latitude
to the resident project representative for protecting the owner.
Prior to reviewing those portions of the specifications which
are particularly useful to the resident project representative, there
are two items of a design nature which will be discussed. The PVC pipe
specified for trenchless installation for this particular project was
ASTM D-3033 SDR 41 whereas the gravity sewer pipe was ASTM D-3034 SDR 35.
The solvent weld pipe for the trenchless method had a minimum wall thick-
ness of 0.199 inches (.505 cm) whereas for the conventional sewer the
minimum wall thickness was 0.240 inches (.609 cm). The thicker material
was unavailable with solvent weld joints at the time the contract documents
were advertised. However, based on field observations, it was felt that
a thicker wall pipe would reduce vertical and horizontal displacement pro-
blems created during lateral installation.
The manhole pipe seals used on this project were particularly adapt-
able to the stress relief system which will be discussed later in this
subsection. The precast manholes utilized integrally cast A-LOK gaskets
per ASTM Rubber Gasket Specification C-443.
The following construction guidelines are, for convenience, listed in
the order in which they would be used during construction:
1. Do not allow solvent welding of joints when temperatures
are less than 40 degrees farenheit. Adhere to the pipe
manufacturer's recommendations when pulling welded material
during cold weather.
2. Once the pipe has been pulled, require the Badger operator
to back the equipment in the reverse direction for a minimum
of two inches to reduce pipe tensile stress. This back-
up procedure, of course, is to be performed while the pipe
is still connected to the expander and must be done promptly,
particularly in cohesive soils. Require the contractor to
check the elevation at the Badger end of the pipe after each
pull prior to backfilling the excavation.
3. Require the contractor to provide suitable support for the
sewer at each end of the pipe to maintain invert control
prior to manhole installation. A stone bedding to the
spring line or a brace would be suitable. The method
should not be specified, but should be subject to the
engineer's approval prior to use.
4. When opening the trench to make saddle and lateral connections,
the contractor should be required to stabilize the exposed
sewer pipe. Once again, although the method need not be
48
-------
specified, it should be subject to the engineer's approval
prior to actual saddle installation. Two methods which
appear to be practical are the placement of stone bedding
to the spring line after undercutting the pipe or; the place-
ment of a wood or rebar brace which can be left in place
after lateral installation.
In grass roots projects, the construction of buildings,
culverts, etc. should be closely coordinated with the
installation of the utility being installed by the trenchless
method.
49
-------
SECTION 7
PROJECT EVALUATION
EVALUATION GOALS
The principal purposes of this project were to first develop and
then evaluate cost, performance and effectiveness data with relation to
both the conventional and trenchless technique under similar site condi-
tions. Cost comparison methods used were as follows:
Contract Prices
Calculated Composite Sewer Systems
Man-day Rate
In addition, certain environmental factors were to be considered with pri-
mary emphasis placed on the possible impact on groundwater quality. Other
environmental factors considered in this report resulted from observations
of the trenchless technique and were actually considered in retrospect.
Therefore, quantitative data on environmental factors, with the exception
of groundwater quality, was not developed.
COST COMPARISON
Contract Prices
Tables 7 and 8 present actual contract price data (i.e. low bid unit
prices) for selected elements of the contract for both the conventional and
^
innovative portions of the work. Unit costs are shown only for those
items which are normally considered to be directly related to each of the
systems.
The unit costs for eight inch (20.3 cm) PVC gravity sewer main for
conventional and trenchless areas were $15 and $9 per lineal foot ($49.21/m
and $29.53/m), respectively. Unit prices for wyes, manholes, repaving,
stone bedding, etc. were equal for both techniques. The bid elements for
the innovative area, however, included certain elements unique to the Bad-
ger System; repair to underground utility services and storm drains; and, a
significant bid item of $62,000 for mobilization, demobilization. In addi-
tion, a unit price was provided for sewer installation with conventional
techniques where linkage between Badger pipe and a manhole was required for
reasons previously discussed.
These contract prices may not truly reflect the actual cost of con-
struction but do provide the base prices with "which one can anticipate
the possible cost differential between the use of either system. Two
other methods of cost comparison developed to provide both consultant
and contractor with alternate techniques to assess potential cost savings
for a particular situation are presented in the ensuing portions of this
section.
50
-------
TABLE 7
CONTRACT PRICES FOR CONVENTIONAL PORTION OF
THE SOUTH BETHANY DEMONSTRATION PROJECT
Description of Item
For furnishing and placing, complete
in place, except road resurfacing,
Sanitary Sewer Gravity Mains per
Plans and Specs. 8" PVC
For furnishing and placing complete
in place except road resurfacing
Sanitary Sewer Gravity Mains without
stone 8" PVC
For furnishing and placing complete
in place Wye Branch. 8" x 6" PVC
For furnishing and placing standard
manhole per plans and specs.
Manhole under 4 feet
Manhole under 6 feet
Manhole under 8 feet
For furnishing grade F select borrow
complete in place as required.
For furnishing and placing contingent
stone bedding.
For furnishing and placing tar and
chip Bituminous surface treatment
For furnishing and placing Bituminous
Hot Mix surface per plans and specs.
Unit Cost
$ 15.00/LF
($49.21/m)
$ 14.85/LF
($48.72/m)
$ 60.00 Ea.
Quantity
29,691 LF
(9,050 m)
7,676 LF
(2,340 m)
494
Total Cost
$445,365.00
113.988.60
29,640.00
$ 500.00 Ea.
$ 510.00 Ea.
$600.00 Ea.
$ 1.50/Cu.Yd.
($1.96/Cu.M)
$ 8.00/Cu.Yd.
($10.46/Cu.M)
$ 1.50/Sq.Yd.
($1.79/Sq.M)
$ 7.00/Sq.Yd.
35
27
27
14,909 Cu.Yd.
(11,405 Cu.M)
418 Cu.Yd.
(320 Cu.M)
20,730 Sq.Yd.
(17,330 Sq.M)
5,452 Sq.Yd.
17,500.00
13,770.00
16,200.00
22,363.50
3,344.00
31,095.00
38,164.00
($8.37/Sq.M)
(4,558 Sq.M)
-------
TABLE 8
CONTRACT PRICES FOR INNOVATIVE PORTION OF
THE SOUTH BETHANY DEMONSTRATION PROJECT
Description of Item
For furnishing and placing complete
in place, except road resurfacing,
Sanitary Sewer Gravity Mains per
Plans and Specs. 8" PVC
8" PVC (Badger)
For furnishing and placing complete
in place except road resurfacing,
{£ sanitary sewer gravity mains without
stone 8" PVC
For furnishing and placing complete
in place, except road resurfacing
6" Sanitary Sewer Laterals to property
lines per plans and specs.
For furnishing and placing complete
in place Wye Branches 8" x 6" PVC
For furnishing and placing Standard
Manhole Plans and Specs.
Manhole under 4 feet
Manhole under 6 feet
Manhole under 8 feet
Unit Cost
$ 15.00/LF
($49.21/m)
$ 9.00/LF
($29.53/m)
$ 14.85/LF
($48.72/m)
$ 5.00/LF
($16.40/m)
$ 60.00/Ea.
$500.00/Ea.
$510.00/Ea.
$600.00/Ea.
Quantity
2,287 LF
(697/m)
26,764 LF
(8,158 m)
2,669.5 LG
(814.2 m)
26,265 LF
(8,006 m)
822
78
42
11
Total Cost
$ 34,305.00
204,876.00
39,642.08
131,325.00
49,320.00
39,000.00
21,420.00
6,600.00
-------
Ui
OJ
Description of Item
For furnishing and placing contingent
stone bedding
For contingent excavation as required
For furnishing and placing contingent
crusher run base course completed in
place as required.
For furnishing and placing tar and
chip Bituminous surface treatment
for plans and specs.
For furnishing and placing Bituminous
Hot Mix surface per plans and specs.
Underground cable TV house services
Underground telephone house connections.
Underground telephone cable other than
house connection
Repair storm drains damaged by Badger
equipment
Mobilization
Demobilization
Table 8 (Continued)
Unit Cost
$ 8.00/Cu.Yd.
($10.46/Cu.m)
$ 2.00/Cu.Yd.
($2.61/Cu.m)
$ 20.00/Cu.Yd.
($26.14/Cu.m)
$ 1.50/Sq.Yd.
($1.79/Sq.m)
$ 7.00/Sq.Yd.
($8.37/Sq.m)
Quantity
502.5 Cu.Yd.
(384.4 Cu.m)
429.5 Cu.Yd.
(328.6 Cu.m)
133 Cu.Yd.
(102 Cu.m)
39,627 Sq.Yd.
(33,128 Sq.m)
174.7 Sq.Yd.
(146.0 Sq.m)
Total Cost
$ 4,020.00
859.00
2,660.00
59,440.50
1,222.90
$125.00/Ea.
$ 70.00/Ea.
$150.00/Ea.
$152.00/Ea.
$60,000.00/Ea.
$ 2,000.00/Ea.
2
14
1
13
L.S.
L.S.
250.00
980.00
150.00
1,976.00
60,000.00
2,000.00
-------
Calculated Composite Sewer System Comparison
Utilizing actual contract unit costs and knowledge of construction
techniques used in the field, the elements of a completed sewer section
were combined in order to establish comparative costs per lineal foot
of sewer placed. Certain assumptions were necessary to develop this
analysis:
1. It was assumed that the hypothetical collection systems
had the same number of wyes, equivalent number of manholes at
similar depths, equal lateral lengths and that the repaving
requirements for each system were the same.
2. The number of electric, television and telephone service
disconnect and connections required for the trenchless system
was the same as that encountered in the field.
3. The number of storm drains requiring restoration was the
same as that encountered in the field.
4. The documented select borrow quantities for the conventional
area were all attributed to the installation of gravity sewers.
The composite conventional gravity sewer system for this analysis
consisted of the quantities shown in Table 9. For the complete instal-
lation of 37,367 lineal feet (11,389 m) of eight inch (20.3 cm) polyvinyl
chloride gravity sewer, attendant wyes, laterals, manholes and repaving,
the total project cost was $864,891 or $23.15/lineal foot ($75.90/m).
Referring to Table 10, the composite trenchless gravity system con-
sisted of 31,720 lineal feet (9,668 m) of eight inch (20.3 cm) PVC gravity
sewer at a total project cost of $615,158 or $19.39/lineal foot ($63.57/m).
On the basis of this last analysis, the apparent cost differential
of $6.00/lineal foot ($19.76/m) between conventional and trenchless
gravity sewer has been narrowed to $3.76/lineal foot ($12.33/m). However,
consideration should be given to the assumptions made in using this method
of analysis for a particular site. In addition, it should be noted that
approximately 10% of the total construction cost for the trenchless area
was for mobilization, demobilization. For a small project this significant
fixed cost could entirely eliminate the differential, whereas, in a major
construction project the cost for mobilization, demobilization may be in-
significant. In addition, this element of contract work will be the most
difficult for a designer to estimate. Therefore, in order to properly
assess the potential of a trenchless program for a particular project, the
designer should be aware that this lump sum cost will vary significantly
depending upon the proximity of trenchless equipment to the job site at
the time the contract is awarded.
54
-------
TABLE 9
PAYMENT ITEMS FOR COMPOSITE CONVENTIONAL GRAVITY COLLECTION SYSTEM
Description of Item
8" (20.3 cm) PVC Gravity Mains,
complete in place, except road
resurfacing.
8" (20.3 cm) PVC Gravity Mains
complete in place, except road
resurfacing, without stone
bedding.
For furnishing and placing, com-
plete in place, wye branch 8" x 6"
(20.3 cm x 15.2 cm) PVC.
For furnishing and placing, com-
plete in place, except road re-
surfacing 6" (15.2 cm) sanitary
sewer laterals to property lines.
For furnishing and placing
standard manholes
For furnishing grade F select
borrow, complete in place, as
required.
For furnishing and placing
contingent stone bedding.
For furnishing and placing
tar and chip bituminous surface
treatment.
Quantity
29,691 LF
(9,050 m)
7,676 LF
(2,340 m)
748 Each
14,940 LF
(4,554 m)
125 Each
14,909 Cu.Yd.
(11,405 Cu.m)
418 Cu.Yd.
(320 Cu.m)
39,627 Sq.Yd.
(33,128 Sq.m)
55
-------
TABLE 10
PAYMENT ITEMS FOR COMPOSITE TRENCHLESS
Description of Item
8" (20.3 cm) PVC Gravity Mains,
complete in place, except road
resurfacing (conventional)
8" (20.3 cm) PVC Gravity Mains,
complete in place, except road
resurfacing without stone bedding
(conventional)
8" (20.3 cm) PVC Gravity Main,
complete in place, except road
resurfacing (trenchless)
For furnishing and placing com-
plete in place wye branches 8" x 6"
(20.3 cm x 15.2 cm)
For furnishing and placing, com-
plete in place, except for road re-
surfacing 6" (15.2 cm) sanitary sewer
laterals to property line
For furnishing and placing standard
manholes
For furnishing grade F select borrow
complete in place as required
For furnishing and placing contingent
stone bedding
For furnishing and placing tar
and chip bituminous surface treatment
Mobilization & Demobilization
Underground cable and TV Service Repair
Underground Electrical service repair
Underground telephone connection repair
Underground telephone cable other
than house connection
Storm drain repair
GRAVITY COLLECTION SYSTEM
Quantity
2,287 LF
(697 m)
2,669.5 LF
(814 m)
26,764 LF
(8,158 m)
634 Each
12,690 LF
(3,868 m)
106 Each
7,784 Cu.Yd.
(5,955 Cu.m)
502.5 Cu.Yd.
(384 Cu.m)
39,627 Sq.Yd.
(33,128 Sq.m)
Lump Sum
2 Each
21 Each
14 Each
1 Each
13 Each
56
-------
It was recognized that inflation factors, labor rates and other
elements which impact on construction costs would tend to limit the period
during which the bid price information would be of value. In an effort to
extend the useful life of the project outputs, and to afford both consul-
tants and contractors another means of assessing the potential of the
trenchless technique for a specific project, field data was assembled to
develop man-day rates for both the conventional and trenchless sewer
systems.
Man-Day Rate Comparison
As mentioned in Section 6, under Comparative Construction Techni-
ques, the conventional crew was made up of a foreman, three heavy equipment
operators, one pipe layer, three laborers, one engineer and one engineer's
helper. The Badger crew consisted of a foreman, two equipment operators
and two laborers.
Man-day rates for conventional installations were developed for the
installation of gravity mains and laterals in the conventional area.
The rates for main installation include excavation, placement and back-
filling of 63,006 lineal feet (19,204 m) of eight, ten, twelve and fifteen
inch PVC pipe (20.3, 25.4, 30.5 and 38.1 cm respectively), eight inch
(20.3 cm) concrete and eight inch (20.3 cm) Asbestos Cement Pipe. Also
included was the placement of 639 wyes and 191 manholes. Although the
engineer and assistant have been identified as part of the conventional
area construction crew, under actual field conditions they rotated between
three active crews and, therefore, they were assigned, for the purpose of
this analysis, one third man-day each.
The construction involved in the installation of sanitary laterals
in the conventional area consisted of excavating, placing and backfilling
of 11,483 lineal feet (3,500 m) of six inch (15.2 cm) PVC pipe. The
lateral crew consisted of one foreman, one pipe layer, two equipment
operators and two laborers.
It required 2,833 man-days to install approximately 63,000 lineal
feet (19,202 m) of conventional sewer which is equivalent to 0.0450 man-
days per lineal foot (0.147 man-days/m).
Because of the high water table prevalent in the area, continuous
dewatering was required to install sewers in the conventional area. Two
dewatering crews consisting of five persons each were active at the site
for approximately three months. Discounting personnel assigned to night
duty for pump observation, an additional 600 man days can be assigned to
the conventional manpower tabulation or 0.010 man-days/lineal feet (0.031
man-days/m). Thus, the total labor for conventional sewer installation
is 0.0550 man-days/lineal foot (0.180 man-days/m).
57
-------
In the innovative area, the man-day equivalents for the gravity main
consisted of the time required for set up, plowing and disconnecting during
the installation of 26,764 lineal feet (8,158 m) of trenchless pipe.
One of the unique characteristics of the trenchless system is that
wyes are not installed coincident with the installation of a main. The
man-day requirements for lateral connections, therefore, include the ex-
cavation, placement and backfilling of 822 saddle wyes as well as 14,771
lineal feet (4,502 m) of six inch (15.2 cm) laterals.
In the Badger area, manholes were also placed after main installation.
The construction of manholes included excavation, placement and backfilling
of 139 manholes and includes the installation of conventional connections
between the manhole and the end of trenchless pipe.
One thousand one hundred forty one man-days were required to install
26,764 lineal feet (8158 m) of trenchless sewer which is equivalent to
0.0426 man-days per lineal feet (0.140 man-days/m).
There is an obvious labor incentive in using the trenchless technique.
Assuming an hourly average rate, including fringe benefits, of $8.50/hour,
the man-day analysis yields a labor savings of $0.84/lineal foot
($2.76/meter) compared to $3.76/lineal foot ($12.33/m) using the composite
sewer technique and $6.00/lineal foot ($19-67/m) based on the bid price.
Therefore, one would anticipate a cost savings by using the trenchless
method regardless of the estimating technique used.
EVALUATION OF COMPLETED SYSTEM
Comparative Invert Elevations
During the project period, careful records were kept of invert
elevations in both the trenchless and conventional areas. The specified
vertical tolerance as measured at the manhole was i 1/2 inch (+ 1.27 cm)
For field control purposes, this tolerance was converted to 0.04 feet
(1.22 cm).
In the conventional area, as indicated in Figure 23, 31% of the
"as-built" invert elevations were within the specified tolerance where-
as 47% were within .06 feet (1.83 cm). The data set for this analysis in-
cluded 158 measured invert elevations. To allow for equity in comparison
with the Badger system, all points in excess of 0.30 feet (9.14 cm) differ-
ential were discarded.
A number of factors contributed to this poor performance. Ship-
ment of manholes was delayed during the early portion of conventional
construction and a number of sewers were installed with gaps left between
lines for subsequent manhole placement. In addition, the high water
58
-------
100
90
80
70 -
60
50 -
40
30
20 -
10 -
Notes
Specification
Tolerance
0.01 0.02 0.03 0.04 0.05 0.06 0.07
B
A. Percentage of points whose deviation from design invert elevation
is less than or equal to B.
B. Difference between "As-Built" invert elevation of conventionally
installed pipe and design invert elevation.
Figure 23 Delta Invert Elevating Conventional Pipe, Project
Average (As-Built).
59
-------
table combined with poor subsoil conditions lead to settlement of manholes
in certain areas. The contractor, in an effort to offset this problem,
purposely placed manholes at a higher invert elevation than specified.
It was intended that natural settlement would bring the invert within the
1/2 inch (1.27 cm) tolerance.
In the Badger area, two sets of invert elevation data were obtained.
In addition to normal "as-built" elevations, the invert elevations of the
Badger installed pipe were measured and recorded immediately after the pull,
i.e. prior to manhole placement. Referring to Figure 24, note that 40% of
the trenchless area invert elevations were within the 0.04 feet (1.22 cm)
tolerance and 50% fell within 0.06 feet (1.83 cm) differential based on
"as-built" information. One hundred thirteen data points were used to com-
pile this graph, but, in this case, differentials in excess of 0.30 feet
(9.14 cm) were not discarded. Obviously, on the basis of "as-built" infor-
mation, the Badger system was only nominally better than the conventionally
installed sewers.
However, there was one factor which lead to a number of signifi-
cantly high differentials in the trenchless area. Referring to Figure 25,
manhole placement and conventional connection of the Badger pipe to the
manhole often lead to a deviation which was far in excess of that which
would have occurred had the conventionally installed pipe and manhole been
installed by extending the conventional sewer on the same slope to which
the Badger pipe had been laid. Therefore, the data was reassessed by com-
puting the invert elevation in the trenchless areas by simply extending the
line at installed grade to its point of intersection with the manhole.
Referring to Figure 26, the project averages on the basis of the
methodology defined above show a significant improvement. Greater than
75% of the computed invert elevations were within the .04 feet (1.22 cm)
tolerance. Furthermore, 88% would have been within .06 feet (1.83 cm)
differential had the installations occurred in the manner prescribed. As
related in Section 6, the efficiency of the Badger crew increased as the
project progressed. Referring to Figure 27, a similar improvement was seen
in the ability of the crew to meet the specified tolerance, once again
based on a computed manhole elevation. By the end of the project, 100%
of the pipe installed during the last month was within .06 feet (1.83 cm)
of the design invert elevation. Eighty one percent (81%) was within
the prescribed tolerance. At the beginning of the project in the month
of March, only 88% of the points were within .06 feet (1.83 cm) and 73%
were within the specified limits.
In summary, the care taken in the placement of connecting pipe and
in setting the manhole foundation can have a major influence on the
quality of the job as measured by vertical alignment. Of the 113 data
points used in evaluation of the trenchless invert, 65% were felt to
have been adversely affected by either manhole placement or the install-
ation of the connecting sewer by conventional means.
60
-------
100 I
90 -
80 -
70 -
60 -
50 -
40 •
30
20 •
10 -
Notes
V
Specification
Tolerance
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
B
A. Percentage of points whose deviation from design invert
elevation is less than or equal to B.
«
B. Difference between "As-Built" invert elevation of trenchless
installed pipe and design invert elevation.
Figure 24 Delta Invert Elevation, Trenchless Pipe, Project
Average (As Built)
61
-------
STATION
NJ
0+00
0+22
0+81
INVERT
ELEVATION
As Built+0.89
Badger+0.84
Design+0.79
3+04
INVERT
ELEVATION
Badger+1.63
Design+1.63
As Built+1.53
Figure 25 Effect on Final Invert Elevation of Conventional
Connection of Trenchless^Pipe to Manhole.
-------
100
90-
80-
70
60-
50-
40-
30
20 -
10 -
Notes
Specification
Tolerance
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
B
A. Percentage of points whose deviation from design invert
elevation is less than or equal to B.
B. Difference between "Computed" invert elevation of Badger
installed pipe and design invert elevation.
Figure 26 Delta Invert Elevation, Trenchless Pipe Project Average
(Computed).
63
-------
100 i
90 -
80 •
70 -
60 -
50 -
40 -
30
20
10 -
Specification
Tolerance
0.01 0.02 0.03 0.04 0.05 0.06
B
0.07
Note A: Percentage of points whose deviation from design invert
elevation is less than or equal to B.
B: Difference between computed invert elevation of Badger
installed pipe and design invert elevation.
Figure 27 Delta Invert Elevation, Trenchless Pipe, By Month
(Computed)
64
-------
Incremental Horizontal/Vertical Alignment
In terms of horizontal and vertical alignment requirements the basic
specifications for the project required:
1. Consistently laying a sewer to grade with a vertical
tolerance of + .04 feet (1.22 cm).
2. Consistently laying a sewer to line within a horizontal
tolerance of ± 0.17 feet (5.2 cm).
In standard construction contracts, the resident project representative
establishes compliance with vertical alignment by measuring invert eleva-
tions at the manhole and performs a mirror (lamp) test on all sewers for
alignment and grade. The measured invert test is fairly sophisticated
when compared with the mirror test, which requires only that the alignment
be sufficiently true and straight to allow for the passage of reflected
sunlight in order for the line to be accepted.
Although both of the above techniques were used to establish
conformance with the design documents, a more rigorous testing procedure
was developed to afford the opportunity of a more critical comparison bet-
ween the trenchless and conventional techniques for these two elements of
construction control.
Actual deviations in the vertical and horizontal plane were measured
in fifty feet (15.24 m) increments along the sewer using a laser oriented
system developed specifically for this project. A description of the
methodology used is followed by an analysis of the data developed. Figures
28 through 32 are photographs taken of the technical crew during the laser
alignment tests and support the following narrative. Having removed the
manhole casting, the sewer is first lamped using standard techniques to
determine whether or not the alignment is sufficiently true to allow pass-
age of the laser beam. In those cases where misalignment was severe, it
was so noted in a field book and the crew moved on to the next sewer length.
When an acceptable sewer is found, a nylon leadline is attached to
a parachute and then the parachute is inserted into the sewer pipe, see
Figure 28. The parachute serves to pull the leadline through the sewer
to the upstream manhole. The leadline, of course, is used to pull the
laser target through the sewer itself.
The parachute technique was found to be the optimum method after
many other transport techniques were discarded either for being imprac-
tical or too time consuming. The parachute was made of tent canvas and
was prevented from collapsing by the insertion of a plastic ring at the
wide end. This ring had a diameter of 1/2 inch (1.22 cm) smaller than the
internal diameter of the pipe. The chute itself was approximately 9 inches
(22.9 cm) long.
65
-------
Figure 28. Parachute Insertion
Once the parachute has been inserted with the leadline attached, a
6 inch diameter flexible hose is inserted into the pipe (Figure 29). This
hose is attached to a gas powered low pressured blower which provides the
motive force for the parachute. With the parachute successfully retrieved
at the upstream manhole, the laser target is attached to the leadline and a
trailing line is also tied to the target to allow the technicians to re-
trieve the target in the event it becomes lodged in the pipe.
The target itself was specially designed for the project when it
was discovered that commercial units had two principal deficiencies:
1. The rigid plastic material provided by most manufactureres did
not have the inherent flexibility required to move the target
past impediments within the pipe.
2. Most standard targets are transparent to allow the light beam
to carry through the garget and, as will be discussed later,
this created a problem on the project.
66
-------
Figure 29. Air Blower Hose Insertion
The target was mounted on two wooden skids curved on the ends similar
to runners on a sled. The system was designed such that the center line
of the target was always in the center line of the pipe regardless of the
spatial position of the skids.
Once the target was in place, the technicians set up the laser in
the manhole opposite the end at which the target was located. The laser
used was a Beam Aligner as manufactured by Laser Alignment of Grand
Rapids, Michigan. Referring to Figure 30, the laser output end of the
beam aligner was centered in the manhole and fixed. Using a series of
locks and screws, the technician at the laser end of the system maneuvered
the light beam position on the target, as instructed by a technician
assigned to the target station. If a misalignment prevented transmission
of the light beam to the target with the laser light centered at the laser
end of the system, the unit was off set and the deviation recorded so that
field data collected could be modified to reflect the deviation. The
centered target, prior to movement for measurement, is shown in Figure 31.
6
-------
Figure 30. Placement of Laser Equipment
Figure 31. Target in Place
-------
A chain was laid between manholes to serve as a method of recording
stations as measured by the length of leadline pulled from the manhole as
the target was moved forward. The technician on the target end of the
sewer system used a forty-eight power monocular to determine the relative
dimensions between the center of target and the location of the laser light
on the target, see Figure 32. The standard target used at the outset of
Figure 32. Siting the Target
the project allowed the laser light beam to pass through the target creating
a blinding red light in the monocular, thereby preventing measurement of
the misalignment. The target developed for the project was transluscent.
The laser beam created a soft red glow at the point of contact with this
transluscent material and the distance between the two points was easily
discerned.
Measurements were taken at 50 feet (15.24 m) increments along the
sewer line and the speed with which measurements were taken was greatly
facilitated when the technician developed a technique of placing the
monocular on a foam rubber pad on the bench. This precluded any signifi-
cant movement of the monocular which had previously made it difficult to
find and then focus on the target.
69
-------
Data Analysis—
As previously mentioned, the specification required compliance with a
vertical tolerance of i .04 feet (1.22 cm) and, in the horizontal plane, a
tolerance of t 0.17 feet (5.2 cm). It should be noted that this specifi-
cation applied only to the trenchless system, there being no tolerance re-
quirements in the specifications for the conventional area. However, for
comparitive purposes, the trenchless tolerances were used to develop the
figures incorporated in the text. These measurements reflect deviations
at 50 feet (15.24 m) increments from manhole to manhole. For this analysis,
the center line of the pipes projecting into the manholes at either end of
the sighting line were considered to be at 0.00 datum both horizontally
and vertically.
In the conventional area, 93% of the 42 data points conformed to
the vertical tolerance whereas 60% were within the specified horizontal
requirement. Of the 60,000 lineal feet (18,288 m) installed by the conven-
tional method, only 2,000 feet (610 m) were subjected to the laser align-
ment test in order to provide a representative base for comparison with the
trenchless sewer.
The trenchless sewer had 78% of the 155 data points within the verti-
cal requirement. Compliance with the horizontal requirement was worse.
Fifty percent of the data points were acceptable.
The resident project representative noted that there was a signi-
ficant impact on sewer alignment created by the installation techniques
used for installing saddle wyes and laterals. Sewer mains which had been
lamped and found to be "rifle barrel" true prior to lateral installation,
were subsequently lamped, and in some instances found, to allow little or
no light transmission. In an effort to provide field verification for this
supposition, an attempt was made to inspect virgin pipe with the laser
system prior to lateral installation. Unfortunately, due to the long lead
time required to develop the technique no substanative field verification
was accomplished. The bases for the resident project engineer's remarks
were previously discussed in Section 6 under the Technique Improvement sub-
section. Basically, the sewer main was found to be unstable when open
cutting occured for saddle and lateral installation. Lines not stabilized
apparently had a tendency to move in both planes during backfill.
To corroborate the assumption in retrospect, the data were analyzed
to determine whether there was a relationship between the number of
laterals installed and the number of deviations sited. Referring to
Figures 33 and 34, it is obvious that attempts to establish this correlation
failed.
As in previous instances of data assessment, the data were reviewed
to determine whether or not there was an improvement in technique which
led to greater conformance with the specifications as the project progress-
ed. The data points were random in nature and reflected neither an improve-
70
-------
100
90 -
80 -
70 .
co
4-1
a
g 60
S-i
a
0}
CB
0)
«w 50 -
0)
o
a
40 -
o
a
30 -
20 -
10 -
0
10
20
30
40
50
60
Average Distance Between Laterals, Lineal Feet (Meters)
Figure 33 Relationship between vertical non-compliance and
lateral density.
71
-------
1004
90-
80<
w 70-
% 60-
CD
o) 50-
CJ
8 40-
c
o
c 30
o
N
•H
t-l
20-
10-
10 20 30 40 50 60
Average Distance Between Laterals, Lineal Feet (Meters)
Figure 34 Relationship between horizontal non-compliance
and lateral density.
72
-------
ment nor degradation in construction quality with time.
Infiltration/Inflow Analysis
The Badger technique, using solvent welded pipe and rubber gaskets
in precast manholes, resulted in an extremely tight sewer. The Sussex
County Engineer's office will not allow an infiltration rate in excess
of 50 gallons per inch of pipe diameter per mile of pipe for twenty
four hours. In the trenchless area, the sewers were found to be water
tight as measured by the standard infiltration test. No water was ob-
served. In the conventional area, the measured flowmeter for two sub-
drainage areas ranged between 16 and 44 gallons per inch of pipe diameter
per mile of pipe for twenty four hours. In all cases this rigid infil-
tration requirement was met. Water tight manhole inserts, as manufac-
tured by Methods Engineering Corporation, contributed significantly to the
overall dryness of each of the systems.
Closed Circuit Internal Television Inspection
Twenty thousand lineal feet (6096 m) of trenchless sewer was inspect-
ed using internal television inspection tehcniques to support the infil-
tration analysis findings and to provide an historical record of the
internal condition of the system prior to placing it into operation. With
the exception of dips in the line which were also found during the laser
alignment phase, only one problem was identified. An offset joint was
observed midway between two manholes in the Bayview Park area but was not
observed to be leaking at the time the camera passed.
ENVIRONMENTAL ASPECTS
Groundwater Quality
The only factor of environmental concern for which the project speci-
fically required the development of quantitative data was the potential for
the trenchless technique to limit degradation of groundwater quality. Back-
ground information was obtained at ten sampling points located throughout
the trenchless area, see Figure 35, for thirty three (33) parameters in-
cluding heavy metals. In some instances, wells were not installed in time
to obtain more than one background sample. However, background data are
available for all sampling points.
After construction was initiated, four additional samples were taken
before it became obvious that no particular pattern was developing and the
program was concluded. The analyses are presented here in Tables 11
through 20.
73
-------
. « .'.-•• * •
* '_ •
MIDDLESEX
BEACH
SOUTH
BETHANY
. .., ' u '•• • • .'
. • • • • o- •• ..-. .
BAY VIEW
PARK; V
LITTLE ASSAWOMAN BAY
* * 4 ' "
Figure 35 Groundwater Quality Monitoring Well Locations
74
-------
Ui
Parameters
TABLE 11
Grbundwater Quality Data*
Hell No. 1
Pre Construction
#1 n
TABLE 12
BODj
COD
Alkalinity as CaCOj
Acidity as CaCOj
Specific Conductance, umhbs/1
Temperature °C
Detergent, MBAS
Oil & Grease
Total Collform,If/100 ml
Fecal Coliform.0/100 ml
Total Kjeldahl Nitrogen as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite ^Nitrate as N
Total Phosphate as P
Chloride
Hardness, as CaCO-j
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settieable Solids, ml/1
Total Suspended Solids
Non-Volatile Sus. Solids
Volatile Suspended Solids
Total Solids
Non-Volatile Total Solids
Volatile Total Solids
5.0
32
3
13
280
9.0
* <0.1
1
0.11
<0. 10
0.11
<0.04
0.14
<0.17
520
46
0.13
1.1
<0.05
<0--05
<0.05
0.26
<0.5
<0.01
10
1010
950
60
1210
1100
110
During Construction
#3
5.7
20
48
1020
18
0.1
<10
<10
0.19
0.19
<0.10
<0.04
0.15
<0.2
260
131
0.28
0.88
<0.05
0.12
<0.05
1.1
<0.5
0.05
19
3100
2850
250
3600
3250
350 .'
#4 #5 #6
<2.4 <2.4 14
>800 300
>800 <10 <10
0.11 0.21 0.10
120 ... 80 , -19
1290 1670 12
'"**'"*•
Parameters
BOD,
COD
Alkalinity as CaCO3
Acidity as CaCO.
Specific Cond., pmhoB/1
Temperature,. °C
. Detergent, MBAS
Oil S Grease
Total ColifonM/lOOnil
Fecal Conform,f/10Qtnl
Total KJeldahl-N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite -fNltrate as N
Total Phosphate as P
Chloride
Hardness, as CaCO-j ,
Manganese
Iron •
Lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settieable Solids, ml/1
Total Suspended Solids
Non-Volatile SS *
Volatile SS :
Total Solids
Non-Volatile T. Solids
Volatile Total Solids
Groundwater Quail
Well No. 2
Pre Construction
11
<2.4
<5
7
16
250
7.0
<0.10
3
<0.10
<0.10
<0.10
<0.04
<0.04
<0il7
62
20
<0.05
0.24
<0.05
<0.05
«0.05
0.08
0.8
<0.01
<0.2
19
15
4
140
130
10
#2
<2.4
12
5
49
300
8.0
<0.1
<1
10
<0.10
<0.10
<0.10
<0.04
0.20
<0.17
500
30
<0.05
0.3
<0.05
<0.05
<0.05
<0.10
<0.5
<0.01
0.5
40
20
20
160
140
20
During Construction
#3 *4
<2.4 3.8
12
69
27
280
18
0.12
C5 II
<2.4
10
0.10
<0.04
<0.04
<0.2
40
110
0.36
2.0
<0.05
<0.05
<0.05
<0.10
<0.5
<0.01
9
7
2
190
130
60
3.04 <0.04
76
80
460
•Units are ng/1 except as noted
-------
TABLE 13
TABLE 14
ON
Groundwater Quality Data
Well No. 3
Fre Construction
Parameters
BODj
COD
Alkalinity as CaCOj
Acidity as CaCO-j
Specific Cond., umhos/1
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Collform, 0/100ral
Fecal Collform, #/100ml
Total Kjeldahl N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite -HUtrate as N
Total Phosphate as P
Chloride
Hardness, as CaCO,
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Non-Volatile T. Solids
Volatile Total Solids
01
2.7
24
33
26
590
6.5
<0.10
<1
0.27
<0.10
0.27
<0.04
<0.04
<0.17
140
66
0.12
5.4
<0.05
<0.05
<0.05
<0.10
1.3
<0.01
0.5
190
180
10
640
570
70
112
2.7
32
27
34
500
9.0
<0.1
<1
10
<10
0.20
<0.10
0.20
<0.04
<0.04
<0.17
620
40
<0.05
4.5
<0.05
<0.05
<0.05
<0.10
1.9
<0.01
0.3
100
90
10
610
580
30
During Construction
#3 #4
<2.4 <2.4
24
18
61
2200
17
0.3
<10 <10
<10 <10
0.37
0.38
<0.04 <0.04
<0.04
<0.2
710 200
260
0.08
18
<0.05
<0.05
<0.05
0.19
<0.5
<0.01
3.5
30 70
20
10
1270
1060
210
#5 #6
<2.4 2.4
30 <1
60 <10
<0.04 <0.05
520 320
140 30
Parameters
BOD,
COD
Alkalinity as CaCO,
Acidity as CaC03
Specific Cond..unhos/1
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Colifonn,#/100ml
Fecal Coliform,0/100ml
Total Kjeldahl N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite +Nitrate as N
Total Phosphate as F
Chloride
Hardness, as CaCO-j
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Groundwater Quality Data
Well No. 4
Pre Construction
#1 t2 03
<2.4
64
90
28
9400
8.0
0.14
1.11
<0.10
1.11
<0.04
<0.04
<0.17
4000
1100
0.26
2.2
<0.05
<0.05
<0.05
0.14
<0.5
<0.01
0.3
60
50
10
5540
During Construction
#4 #5 #6
<2.4
<2.4 9.6
43
51
35
1100
18
0.12
1.25
Non-Volatile T. Solids 4960
Volatile Total Solids 580
1,
<0,
<0.
<0,
4300
1220
0.
2,
0,
<0.
<0.
<0,
<0.
<0.
0.
100
100
0
6800
5800
1000
04 <0.04 <0.04 <0.05
04
2
2700 4500 2020
19
6
10
05
05
10
5
01
2
60
40
30
-------
TABLE 15
Parameters
BOD-
COD
Alkalinity as CaCO,
Acidity as CaCO3
Specific Cond.,umhos/l 3500
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Coliform,0/100ml
Fecal Coliform,*/100ml
Total Kjeldahl N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite +Nitrate as N
Total Phosphate as P
Chloride
Hardness, as CaCOj
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury,,jig/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Non-Volatile T. Solids
Volatile Total Solids
Groundwater Quail
Well No. 5
Pre Construction
01
9.6
92
350
19
3500
8.0
0.17
4.1
0.3
3.8
<0.04
<0.04
<0.17
1150
380
0.18
0.28
<0.05
<0.05
<0.05
<0.05
4.3
<0.01
L <0.1
80
80
0
1950
1760
190
112
3.6
92
290
37
5300
2.0
0.1
190
4.3
<0.10
4.3
<0.04
<0.04
<0.17
900
550
0.14
3.2
<0.05
<0.05
<0.05
<0.10
3.4
<0.01
<0.1
30
30
0
3050
3800
250
TABLE 16
During Construction
#3 #4
3.6 3.5*
78
710
69
9000
17
0.16
10
<10 <10
6.25
0.25
6.0
<0.04 <0.04
<0.04
0.3
3200 2700
1010
0.26
4.8
0.08
<0.05
<0.05
<0.10
3.6
0.01
<0. 1
50 80
40
10
5360
4730
630
#5 #6
2.4 62
<10 200
<0.04 0.
2800 310
30 312
Parameters
BOD5
COD
Alkalinity as CaC03
Acidity as CaCO,
Specific Cond.,Mmhos/l 5400
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Coliform,#/100ml
Fecal Coliform,#/100ml
Total Kjeldahl N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
0.16 Nitrite Nitrogen as N
Nitrite +Nitrate as N
Total Phosphate as P
Chloride
Hardness, as CaCOj
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, pg/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Non-Volatile T. Solids
Volatile Total Solids
Groundwater Quail
Well No. 6
Pre Construction
#1
<2.4*
110
200
58
5400
6.0
<0.10
3.50
0.75
2.75
<0.04
<0.04
<0.17
1750
720
1.5
2.6
<0.05
<0.05
<0.05
0.20
<0.5
<0.01
. <0.1
20
18
2
3070
2780
290
#2
4.5
120
530
35
4000
9.0
0.66
200
12.5
0.10
12.5
<0.04
<0.04
<0.17
860
470
0.45
7.5
<0.05
<0.05
<0.05
<0.10
0.8
<0.01
<0.1
40
40
0
2240
2040
200
During Construction
#4 #5 #6
10
15
<10 <10 80
<0.04 <0.04 <0.05
3300 4000 350
140
80 310
-------
TABLE 17
TABLE 18
00
Grounduater. Quality Data
Well No. 7
#3
Parameters
BODc
COD
Alkalinity as CaCO^
Acidity as CaCOj
Specific Cond. , umhos/1
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Collform, #/100ml
Fecal Coliforiu,«/100ml
Total KJeldahl N. as N
Organic Nitrogen aa N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite -t-Nltrate as N
Total Phosphate as P
Chloride
Hardness, as CaCOj
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Non-Volatile T. Solids
Volatile Total Solids
Pre Construction
#1 «
<2.4*
16
21
19
150
4.0
0.10
<1
0.40
<0.10
0.40
<0.04
0.24
<0.17
27
38
<0.05
0.86
<0.05
<0.05
<0.05
0.08
1.6
<0.01
<0.1
18
12
6
110
60
50
Groundwater Quality Data
Well Mo. 8
During Construction
04 #5 #6
<2.4
2.6* 8.4
170
66
26
625
17
0.26
3.16
1.56
1.6
<0.04
<0.04
<0.2
200
99
0.12
3.5
<0.05
<0.05
<0.05
<0.10
<2.4
0.01
<0.1
30
20
10
580
380
200
<10 >8000 <10
0.15 0.31 0.08
850 400 210
16
20
Parameters
BOD,
COD
Alkalinity aa CaCO,
Acidity as CaCOj
Spec. Cond.,umhos/l
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Collform,#/100ml
Fecal Collform,t/100ml
Total KJeldahl N.
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite +Nltrate as N
Total Phosphate as P
Chloride
•Hardness, as CaCO*
Manganese
Iron
lead
Copper
Chromium
Zinc
Mercury, ug/1
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Non-Volatile T. !
Volatile Total Solids
Pre Construction
tl
3.1*
84
310
60
10,400
9.0
0.10
il
il
N 3.10
1 0.16
1 2.94
r
-------
v£>
TABLE 19
Croundwater Quality Data
Parameters
BOD;
COD
Alkalinity aa CaCOj
Acidity as CaC03
Specific Cond. gmhos/1
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Coll form,«/lOOml
1'ecal Collform,ff/100ml
Total Kjuliliihl N. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite +Nitrate as N
Total Phosphate aa P .
Chloride
Hardness, as
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ugl
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Volatile Tota' Solids
Well No. 9
Pre Construction
«1 112
3.5
32
64
57
520
11.0
<0.1
1
10
<10
0.16
<0.10
0.16
<0.04
<0.04
<0.i7
440
150
0.9
12.5
<0.05
<0.05
'<0.05
0.18
3.9
<0.01
0.7
160
130
30
470
60
During Construction
«3 14 15 #6
28
<2.4 2.9
<10 <10 70
<0.04 <0.04 <0.05
740 1900 45
90
80 220
TABLE 20
Groundwater Quality Data
Well No. 10
Parameters
BOD.
COD
Alkalinity as CaCO,
Acidity as CaCOj
Specific Cond. |inhos/l
Temperature, °C
Detergent, MBAS
Oil & Grease
Total Collform,Jf/lOOral
Fecal CoUform.J/lOOml
Total Kjuldahl M. as N
Organic Nitrogen as N
Ammonia Nitrogen as N
Nitrite Nitrogen as N
Nitrite +Nitrate as N
Total Phosphate as P
Chloride
Hardness, as CaCOj
Manganese
Iron
Lead
Copper
Chromium
Zinc
Mercury, ugl
Cadmium
Settleable Solids, ml/1
Total Suspended Solids
Non-Volatile SS
Volatile SS
Total Solids
Volatile Total Solids
Volatile TS
Pre Construction
*1 02
7.6
84
58
28
640
11.0
<0. 1
<10
<10
2.20
<0.10
2.20
<0.04
<0.04
<0.17
1000
170
0.2
4.0
<0.05
<0.05
<0.05
<0.10
1.1
<0.01
13.0
1350
1250
100
1900
1720
180
During Construction
#3 14 15 06
2.9 24 3.1 20
55
57
36
1900
17
0.18
10 <10 * <1
<10 <10 150 <10
2.0
<0.1
2.44
<0.04 <0.04 <0.04 <0.05
<0.04
<0.2
560 2300 580 190
336
6.31
2.7
0.06
<0.05
<0.05
<0.10
0.7
<0.01
<0.1
30 900 880 2110
30
0
1230
990
240
-------
Other Environmental Aspects
The trenchless technique appears to have certain qualitative benefits
in the areas of noise, sediment runoff, energy consumption and safety.
The conventional method requires the use of heavy equipment to
open trench and the noise from this equipment is constant, almost from the
time trenching begins until backfill is completed. With the Badger method,
however, motor noise is limited to those limited periods when open trench-
ing occurs for lead trench cutting, a brief pull period by the Badger, and
open trenching for pipe connection and lateral installation.
With regard to sediment runoff, the only period during which there is
significant exposed raw earth is during lateral installation. This, of
course, was not a factor on this particular project due to the flat
terrain and the prevailing dry weather which occurred during construc-
tion.
It is unfortunate that no quantitative information was developed on
the fuel consumption associated with both conventional and Badger techni-
ques. Energy was not a prime concern at the time when the demonstration
application was filed. However, the run time of heavy equipment is obvious-
ly less using the trenchless technique for substantially the same reasons
prescribed to the noise level associated with each system.
No significant accidents occurred in either the conventional or
innovative areas during the construction period.
80
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
EPA-600/2-78-022
3. RECIPIENT'S ACCESSION-NO.
Evaluation of Trenchless Sewer Construction
at Bethany Beach, Delaware
5. REPORT DATE
February 1978 (issuing date)
6. PERFORMING ORGANIZATION CODE
Lee J. Beetschen
Hi 1H am H.
8. PERFORMING ORGANIZATION REPORT NO,
12760
ERFORMING ORGANIZATION NAME AND ADDRESS
Edward H. Richardson Associates, Inc.
P. 0. Box 675 Through contract with
Newark, Delaware 19711 Sussex County Council,
. Georgetown, Delaware.
10. PROGRAM ELEMENT NO.
1BC611
11. CONTRACT/GRANT NO.
S-800690
SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
15. SUPPLEMENTARY NOTES ~~~~~ _____
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD
P.O. Hugh Masters 201/321-6678
FTS 340-6678
The purpose of this project was to determine whether the trenchless method of
sewer construction had inherent cost, safety and other advantages over conventional
methods of sewer construction. Under similar site conditions, the trenchless method
was more cost effective than conventional means based on the actual unit bid price
(50%), on complete sewer installation including manholes, wyes and laterals (16%) and
on labor savings (23%). Eight inch polyvinyl chloride pipe with rubber gasketed
joints was used in the conventional area, whereas eight inch polyvinyl chloride sol-
vent welded pipe was used for the trenchless method.
The trenchless method does not appear to be suited for urban areas where signi-
ficant subsurface utilities exist, nor where rock or boulders exist in high density.
However, the system is uniquely adapted to high water table areas, and its flexi-
bility of application under varying soil conditions is wide ranging. The potential
for infiltration is significantly less and, with proper field control, the trenchless
method results in less deflection and horizontal and vertical misalignment. With
open trenching reduced to a minimum, the method is safer than the conventional tech-
nique, particularly where deeper cuts are required. From an environmental stand-
point, the trenchless method provides less disruption to traffic, and represents an
improvement in sediment runoff control and noise reduction.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Sewers, construction costs, construction
materials, construction equipment, urban
planning.
Trenchless sewer method,
innovative sewer con-
struction.
13B
3. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 <9-73)
81
ft U. S. GOVERNMENT PRINTING OFFICE : 1978 260-S80/11
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