20141077 Ver 2_Trenching for Utlities Spec_20200213

Description of Blasting
Blasting is necessary to fracture the subsurface rock so that it can be excavated by mechanical means
when the pipe laying construction equipment digs the pipe trench. It is confined to the pipe alignment,
and blasts are sized and spaced to provide the necessary fracturing while maintaining the fracturing
within the work area limits. Generally, a drill rig works ahead of the trench excavation equipment (pipe
laying crew), and drills pilot holes until the surface of the rock is located. Then, the rig will drill holes to
the depth required through the rock to set the dynamite in the proper location. Typically, the pilot hole
drilling is completed for a certain length ahead of the pipe laying crew to map out the rock profile. The
drilling and blasting crew returns to drill and set the dynamite. The pre-blast effort can take days or
weeks depending on how far ahead of the pipe laying the contractor wants to drill before blasting.
Blasting is typically performedin an isolated section where blast mats can be laid on top of the ground
surface above the blasting area. Setup for blasting may take several days, and a series of blasts in one
location will be performed in one day. The blast locations are dictated by the actual subsurface
conditions discovered during pre-drilling of the pipe alignment.

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SECTION 02315

TRENCHING FOR UTILITIES
PART 1 GENERAL
1.01 SCOPE
A. Provide labor, equipment, and material to perform required excavating, backfilling,
and compacting for utilities and related structures as specified herein and indicated
on the Drawings. Work shall include, but not be limited to, the following:
1. Survey staking as required for construction.
2. Protection of existing improvements.
3. Location of existing utilities.
4. Use of explosives.
5. Dewatering.
6. Excavating, backfilling, and compacting for utilities.
7. Installation of warning / identification tape and tracer wire.
8. Borrow material.
9. Disposal of surplus material.
10. Demolition and removal of existing structures.
11. Soil Testing.
1.02 RELATED SECTIONS
A. The following Sections have work that is directly related to this Section. This does
not relieve the Contractor of his responsibility of proper coordination of all the work:
1. Section 02230 Clearing and Grubbing
2. Section 02370 Erosion Control
3. Section 02510 Water Distribution System
4. Section 02530 Sanitary Sewer System
5. Section 02920 Lawns and Grasses
B. The City of Raleigh Public Utilities Handbook, as it relates to this Section, shall be
used in conjunction with this specification. All aspects of the project construction
shall conform to this handbook unless specifically noted otherwise herein. It is the
Contractors responsibility to obtain this document from the City’s Public Utilities
Department. It can be obtained by phone at 919-996-3245 or on the internet at
http://www.raleighnc.gov/ under Departments and Public Utilities.
C. In the event of a discrepancy between this specification and the Handbook, the
Contractor shall use the more stringent of the two documents. Notify the Owner and
Engineer immediately of the discrepancy.
1.03 REFERENCED STANDARDS
A. The latest revision, at the time of bidding, of the publications listed below form a part
of this specification to the extent referenced. The publications are referred to in the
text by basic designation only.
1. N.C. Department of Transportation - Standard Specifications for Roads and
Structures (NCDOT).
2. American Society of Testing Materials (ASTM)
a. D698 Moisture-Density Relations of Soils and Soil-Aggregate Mixtures
Using 5.5-lb (2.49 Kg) Rammer and 12-inch Drop (Standard
Proctor).

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b. D1556 Density of Soil in Place by the Sand-Cone Method.
c. D1586 Penetration Test and Spilt-Barrel Sampling of Soils.
d. D2049 Test for Relative Density of Cohesionless Soils.
e. D2216 Laboratory Determination of Water (Moisture) Content of Soil,
Rock, and Soil-Aggregate Mixtures.
f. D2487 Classification of Soils for Engineering Purposes.
g. D3839 Standard Guide for Underground Installation of “Fiberglass”
(Glass-Fiber Reinforced Thermosetting-Resin) Pipe and Fittings.
3. American Water Works Association (AWWA)
a. Fiberglass Pipe Design Manual of Water Supply Practices M45
b. PVC Pipe Design and Installation Manual for Water Supply Practices M23
c. Ductile Iron Pipe and Fittings Manual for Water Supply Practices M41
4. Uni-Bell PVC Pipe Association
a. B-5-89 Recommended Practice for the Installation of Polyvinyl Chloride
(PVC) Sewer Pipe.
5. Ductile Iron Pipe Research Association (DIPRA)
a. 8-08/5M Design of Ductile Iron Pipe
1.04 DEFINITIONS
A. Backfill: A specified material used in filling the excavated trench and placed at a
specified degree of compaction.
1. Materials: Materials listed herein include processed materials plus the soil
classifications listed under the Unified Soil Classification System, (USCS)
(Method D2487 and Practice D2488). The soil materials are grouped into five
broad categories according to their suitability for this application.
a. Class I: Angular, 6 to 40-mm (1/4 to 1-1/2-in), graded stone, including a
number of fill materials that have regional significance such as coral, slag,
cinders, crushed stone, and crushed shell.
b. Class II: Coarse sands and gravels with maximum particle size of 40 mm
(1-1/2 in.), including various graded sands and gravels containing small
percentages of fines, generally granular and noncohesive, either wet or
dry. Soil Types GW, GP, SW, and SP are included in this class.
c. Class III: Fine sand and clayey gravels, including fine sands, sand-clay
mixtures, and gravel-clay mixtures. Soil Types GM, GC, SM, and SC are
included in this class.
d. Class IV: Silt, silty clays, and clays, including inorganic clays and silts of
medium to high plasticity and liquid limits. Soil Types MH, ML, CH and CL
are included in this class. These materials shall not be used for bedding,
haunching, or initial backfill.
e. Class V: This class includes the organic soils OL, OH, and PT as well as
soils containing frozen earth, debris, rock larger than 40 mm (1 1/2 in.) in
diameter, and other foreign materials. These materials shall not be used for
bedding, haunching, or initial backfill.
2. Backfill Zones: Each backfill zone shall extend the full width of the trench
bottom.
a. Foundation: Extending down from the bottom of bedding zone as defined
below.
b. Pipe Embedment
1) Bedding: Extending from 4 inches below the pipe bottom to the pipe
bottom for 30-inch diameter and smaller and 6 inches below the pipe
bottom for pipes larger than 30 inches in diameter.

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2) Haunching: Extending from the bedding (bottom of the pipe) to the
pipe spring line.
3) Initial Backfill: Extending from the haunching (pipe spring line) to 1 foot
above the top of the pipe.
c. Final Backfill: Extending from the initial backfill to the finish ground
elevation.
B. Laying Conditions:
1. Type 1: Flat bottom trench with loose backfill.
2. Type 2: Flat bottom trench with backfill lightly consolidated to centerline of pipe.
3. Type 3: Pipe bedded in 4 inches minimum of loose soil and backfill lightly
consolidated to top of pipe.
4. Type 4: Pipe bedded on Class I material to 1/8 pipe diameter (4 inch minimum)
Backfill compacted to top of pipe a minimum of 80 percent of standard proctor.
5. Type 5: Pipe bedded in compacted Class I material to pipe centerline with 4-
inch minimum under pipe. Backfill to top of pipe with Class I, II, or III and
compact to 90 percent of standard proctor.
C. Compaction: Process of mechanically stabilizing a material by increasing its density
at a controlled moisture condition. "Degree of compaction" shall be expressed as a
percentage of the maximum dry density obtained by the test procedure presented in
ASTM D698 (Standard Proctor).
D. Excavation: The removal of soil or rock to obtain a specified depth or elevation.
E. Lift: Layer of soil placed on top of a previously prepared or placed soil.
F. Rock: Solid, homogeneous material which cannot be removed without the
systematic drilling and blasting exceeding 1 cubic yard in volume. Material having a
standard penetration rate less than 1-inch of penetration over 50 blows across
continuous materials is defined as "rock." Rock is further defined as materials and
obstructions encountered that cannot be practically excavated with a large track
mounted backhoe, such as a CAT-325 or larger, equipped with a 42-inch rock
bucket and new rock teeth. Practical excavation is defined as the ability to remove
at least 10 cubic yards during one (1) hour of continuous digging. Removal of "hard
material" will not be considered rock excavation because of intermittent drilling and
blasting that is performed merely to increase production
G. Pipe Springline: A line running horizontally through the center of the pipe.
H. Topsoil: Natural, friable soil, representative of productive soils in the vicinity of the
site. Topsoil shall be free from roots, stones larger than 1 inch, objectionable weed
seeds, toxic substances, and materials that hinder grading, planting, and
maintenance operations.
1.05 SUBMITTALS
A. Submit the following in accordance with Section 01330, Submittal Procedures:
1. Catalog Data: Submit manufacturer's standard drawings or catalog cuts for the
following. Clearly indicate equipment to be furnished for the Project including
options to be provided.
a. Warning / Identification tape.
b. Geofabric for trench stone wrap.
c. Tracer wire and appurtenances.
2. Test Reports: Submit for the following:
a. Moisture-density relations of soils.

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b. Field moisture content.
c. Soil classification.
d. In-place field density.
e. Geotechnical engineer's daily field reports.
f. Third-party test reports for pre-construction condition assessments, crack
monitoring and vibration monitoring per Section 02300, Earthwork.
PART 2 PRODUCTS
2.01 STONE
A. Class I material shall be #67 or #78M stone in accordance with NCDOT
specifications Section 1005, General Requirements for Aggregate.
2.02 WARNING AND IDENTIFICATION TAPE
A. Tape shall be a minimum 3-inch wide polyethylene plastic tape manufactured
specifically for identification of buried utilities with means of enabling detection by a
metal detector to a minimum depth of 3 feet. Tape shall be color coded and
continuously imprinted with warning and identification markings in bold black letters
to read "CAUTION - BURIED (utility) LINE BELOW." Color and printing shall be
permanent, unaffected by moisture or soil and shall be as follows:
Utility Color Marking
1. Water Blue Caution – Buried Water Line Below
2. Sewer Green Caution – Buried Pressure Sewer Line
Below
B. Tape shall be by Blackburn Manufacturing, Joseph G. Pollard Co., or Reef
Industries Inc or approved equal.
C. Warning tape shall only be installed for pressure mains constructed of PVC
materials.
2.03 TRACER WIRE AND INDICATION POSTS
A. All non-ferrous pressure mains shall be provided tracing wire and test ports in such
a manner as to be able to properly trace all mains without loss or deterioration of
signal or without the transmitted signal migrating off the trace wire.
B. Tracer wire shall be #12 gauge solid (bare) copper and continuous to the greatest
extent possible. The tracer wire shall be securely bonded together at all wire joints
with an approved industrial crimp connector to provide electrical continuity. It shall
be accessible at all tracer wire test ports.
C. Test ports with marker posts shall be located at bends and no further than 500 feet
apart. The test port shall consist of a standard valve box (as specified in Section
02530), shall be H-20 traffic load rated flush with grade in non-paved areas and
flush with final asphalt or concrete pavement elevation and shall be located over the
downstream or outgoing main. The valve box shall be equipped with a lid stamped
“TS” and painted green for sewer mains, blue for water mains, and Pantone 522C
for reuse mains. At each test port, a loop of wire shall be brought up and looped
inside the box. The loop of wire inside the box shall be a minimum of three feet.

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2.04 TRACER WIRE FOR NONMETALLIC WATER SERVICE PIPE
A. Where nonmetallic water service pipe is allowed, all new nonmetallic water service
pipes shall be provided tracing wire in such a manner as to be able to properly trace
all mains and service laterals without loss or deterioration of signal or without the
transmitted signal migrating off the trace wire.
B. Tracing shall be #12 gauge solid (bare) copper and continuous to the greatest
extent possible. The tracer wire shall be securely bonded together at all wire joints
with an approved industrial crimp connector to provide electrical continuity.
C. The meter box at or near the right of way and or easement shall serve as the test
port with the tracing wire brought up into the meter box with the service lateral and
looped in the meter box. The loop wire inside the meter box shall be a minimum of
three feet.
D. For new nonmetallic water service laterals where no tracer is installed on the main,
provide an anode (1 pound minimum) for the tracing wire termination at the point of
the new tap on the main.
E. For nonmetallic service lateral installations less than 8 feet, the tracing wire shall be
attached to the pipe. For nonmetallic service lateral installations deeper than 8 feet,
the tracing wire shall be installed at a depth of 7 to 8 feet. For nonmetallic service
laterals that are installed in encasement pipe, the tracing wire shall be routed
through the encasement pipe.
F. For nonmetallic service lateral that installed by directional drilling, the tracer wire
shall be attached to and pulled through with the service pipe.
G. The wire shall be protected from damage during the execution of the work. No
breaks or cuts in the tracer wire shall be permitted. Spliced connections shall only
be allowed between the main liner tracer wire (if applicable) and the lateral tracer
wire. Industrial crimps shall be used to provide electrical continuity and the crimps
shall be similar metal to eliminate galvanic corrosion.
H. Contractor shall perform a continuity test on all tracer wire in the presence of the
Owner or Owner's representative. If the tracer wire is found to be not continuous
after testing, Contractor shall repair or replace the failed segment of wire at his own
expense.
I. Copper clad steel tracer wire (#12) as manufactured by Copperhead Industries, or
approved equal is an approved alternative to #12 bare solid copper tracer wire.
2.05 TRACER WIRE FOR GRAVITY SEWERS AND LATERALS AND MANHOLE
MARKERS
A. In accordance with General Statute 87-121(g), gravity sewers and laterals installed
after October 1, 2014 shall be electronically locatable.
B. All new gravity sewer main and sanitary sewer lateral shall be provided tracing wire
in such a manner as to be able to properly trace all mains without loss or
deterioration of signal or without the transmitted signal migrating off the trace wire.
C. Tracing shall be #12 gauge solid (bare) copper and continuous to the greatest
extent possible. Copper clad steel tracer wire (#12) as manufactured by
Copperhead Industries, or approved equal is an approved alternative to #12 bare
solid copper tracer wire. The tracer wire shall be securely bonded together at all

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wire joints with an approved industrial crimp connector to provide electrical
continuity. It shall be accessible at all tracer wire test ports.
D. For gravity mains, test ports shall be provided at frequency of 500 feet or at every
manhole, whichever is the shorter of the distance. The test port shall consist of a
standard valve box (as specified in Section 02530), shall be H-20 traffic load rated
flush with grade in non-paved areas with concrete collar as shown on Detail W -17,
and flush with final asphalt or concrete pavement elevation and shall be located
over the downstream or outgoing main. The valve box shall be equipped with a lid
stamped “TS” and painted green. At each test port, a loop of wire shall be brought
up and looped inside the box. The loop of wire inside the box shall be a minimum of
three feet. All tracing wire for branch mains and laterals that terminate into the
manhole shall be routed around the circumference of the manhole and spliced to the
main tracing line.
E. For sanitary sewer laterals, the cleanout at the right of way and or easement shall
serve as the test port with the tracing wire brought up outside the cleanout assembly
and wrapped around the assembly stack twice at a depth of approximately 12-
inches below grade. Extend a loop of the wire to the top of cleanout.
F. For new sanitary sewer laterals where no tracer is installed on the main, provide an
anode (1 pound minimum) for the tracing wire termination at the point of the new tap
on the existing main.
G. For gravity main and or lateral installations less than 8 feet, the tracing wire shall be
attached to the pipe. Tracer wire shall be laid flat and securely affixed to the pipe at
10 foot intervals. Where lateral taps are made by service saddles, the tracer wire
shall not be allowed to be placed between the saddle and main. For gravity main
and or lateral installation deeper than 8 feet, the tracing wire shall be installed at a
depth of 7 to 8 feet. The wire shall be protected from damage during the execution
of the work. No breaks or cuts in the tracer wire shall be permitted.
H. Spliced connections shall only be allowed between the main line tracer wire and
branch main and lateral tracer wire. Industrial crimps shall be used to provide
electrical continuity and the crimps shall be similar metal to eliminate galvanic
corrosion.
I. Contractor shall perform a continuity test on all tracer wire in the presence of the
Owner or Owner's representative. If the tracer wire is found to be not continuous
after testing, Contractor shall repair or replace the failed segment of wire at their
own expense.
J. Where existing branch mains are reconnected to a main line that is replaced or
realigned, tracing wire is not required for the section of branch main that is
reconnected unless it is replaced from manhole to manhole. All main lines that are
replaced or realigned shall be provided tracing wire.
K. For gravity sewer mains and laterals that are installed in encasement pipe, the
tracing wire shall be routed through the encasement pipe.
L. Manhole markers shall be placed adjacent to manholes at the discretion of Owner or
Owner’s representative.

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PART 3 EXECUTION
3.01 PROJECT SAFETY
A. Contractor is responsible for Project safety.
B. Perform work in conformance with applicable State and Federal safety regulations
including, but not limited, to the following:
1. North Carolina Safety and Health Standards for the Construction Industry
(29CFR 1926 Subpart P and U).
2. NC OSHA Industry Guide No. 14, Excavations.
3. NC OSHA Industry Guide No. 20, Crane Safety.
C. Provide barriers, warning lights, and other protective devices at excavations as
necessary for safety of workers and the public.
D. Provide sloping of bank, shoring, sheeting, or other means of maintaining the
stability of the trench in accordance with the requirements of the Associated
Contractor's Manual of Accident Prevention OSHA, Part 1926.P.
E. In trench depths of 22 feet or greater, provide certification sealed by Structural
Engineer certifying that trench box, sheeting and shoring meets OSHA
requirements.
3.02 VIDEO AND PHOTOGRAPHIC INSPECTIONS
A. Provide pre and post construction video inspections of the project area in
accordance with Section 01320, Video and Photographic Documentation.
B. Submittal shall be in accordance with Section 01330, Submittal Procedures.
3.03 PROTECTION OF UNDERGROUND FACILITIES
A. Refer to paragraph 4.04 of the General Conditions and SC-4.04.A.2 of the
Supplementary Conditions concerning the protection of Underground Facilities.
B. Prior to beginning any excavation work or boring, the Contractor shall, through field
investigations, determine any conflicts or interferences between existing utilities and
new utilities to be constructed under this project. This determination shall be based
on the actual locations, elevations, slopes, etc., of existing utilities as determined in
the field investigations, and locations, elevation, slope, etc. of new utilities as shown
on the Drawings. If an interference exists, the Contractor shall bring it to the
attention of the Engineer as soon as possible. If the Engineer agrees that an
interference exists that was not apparent from the Contract Documents, or could not
have been identified during a site visit during bidding, he shall modify the design as
required. Additional costs to the Contractor for this change shall be processed
through a Change Order as detailed elsewhere in these Contract Documents. An
interference shall be defined for these purposes as a conflict with an existing utility
or structure that prevents the proposed utility from being installed where shown or
specified after existing utilities and structures are adequately supported by the
Contractor. In the event the Contractor fails to complete adequate field evaluations
to identify conflicts, or bring a potential conflict or interference to the attention of the
Engineer prior to beginning excavation work, any actual conflict or interference
which does arise during the Project and could have been avoided with diligent utility
location efforts shall be corrected by the Contractor, as directed by the Engineer, at
no additional expense to the Owner.

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C. A change in conditions may be considered due to the location of the existing
facilities as allowed in the General Conditions. This does not include the cost for
repair of damaged facilities not properly located in advance of construction.
D. Separation distances shall be in accordance with utilities requirements.
3.04 CONSTRUCTION STAKING
A. Provide construction staking as indicated in paragraph 4.05 of the General
Conditions. Engineer will only provide electronic design files for Contractor’s
surveyor and key reference points and benchmarks as shown on the Drawings.
B. Contractor shall report to Engineer whenever a reference point or property
monument is lost or destroyed or requires relocation because of necessary changes
in grades or locations. Contractor shall be responsible for the accurate replacement
or relocation of such reference points or property monuments by a registered
professional surveyor in the State of North Carolina.
3.05 LOCATION OF INSTALLED UTILITIES
A. Contractor shall be responsible for locating contract installed utilities as requested
by third parties proposing to dig in the contract area until the date that the entire
contract is recommended for final payment by Engineer to Owner.
3.06 WATER CONTROL
A. Prevent surface water from entering the trench.
B. When trench bottom is below the existing ground water table, install a dewatering
system to maintain water table a minimum of two (2) feet below trench bottom.
Provide personnel experienced in dewatering work at the job site.
C. Maintain dewatering until backfilling has proceeded above the existing ground water
level.
D. Dispose of water from dewatering operations in accordance with the North Carolina
Sedimentation Pollution Control Act.
E. In no case shall trench water or groundwater be pumped into or allowed to enter the
sanitary sewer system.
3.07 USE OF EXPLOSIVES
A. Blasting is allowable for the removal of rock, as defined herein, unless specifically
prohibited by the Owner, Engineer or a Utility Owner with an existing utility within the
proximity of the proposed blast site. The Contractor shall review the drawings for
specific areas where blasting is prohibited.
B. Obtain required permits for blasting (e.g., from City of Raleigh Fire Marshall’s Office)
prior to blasting, 24 hours minimum.
C. Store, handle, and use explosives in accordance with all applicable local, state, and
federal regulations, and in accordance with the provisions of the "Manual of
Accident Prevention and Construction" of the Associated General Contractors of
America, Inc. Federal regulations include, but are not limited to, Title 27, Chapter
11, Part 555 of the Code of Federal Regulations (CFR) and OSHA Standards – Part
1926, Subpart U. Explosives need to be stored in a manner to prevent damage
from moisture.

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D. Provide seismographic monitoring during progress of blasting operations. A
minimum of four seismographs shall be used at each individual structure (such as a
single-family dwelling or similar size business) unless the structure is larger (such as
a building complex, bridge, etc.) in which case additional seismographs shall be
installed based upon the blasting specialist’s recommendations. Seismographs
shall be equipped with remote monitors that are capable of transmitting readings
directly to the Contractor, Owner, and “third party” testing firm immediately following
the recordings. Seismographs shall also be equipped with visual and audible
alarms at each installation.
E. Take all necessary precautions to protect life and property, including the use of
approved blasting mats where there exists the danger of throwing rock or
overburden. Keep the explosive materials that are on the job site in specially
constructed boxes provided with locks. Failure to comply with this specification shall
be grounds for suspension of blasting operations until full compliance is made. No
blasting using electronic blast caps shall be allowed unless a galvanometer is
employed to check cap circuits. Non-electronic blasting caps shall be utilized in
accordance with all manufacturer’s instructions and safety requirements. Where
blasting takes place within 500 feet of a utility, structure, or property which could be
damaged by vibration, concussion or falling rock, keep a blasting log containing the
following information for each and every shot. This log shall be kept in an orderly
manner and made available to the Engineer and Owner upon request.
1. Date of shot
2. Time of shot
3. Crew supervisor
4. Number and depth of holes
5. Approximate depth of overburden
6. Amount and type of explosive used in each hole
7. Type of caps used (instant or delay)
8. The weather
9. Seismograph instrument and readings
F. Use explosives in such a way to minimize vibration to existing utilities and
structures.
G. Provide only experienced personnel for blasting in accordance with accepted
practices. The personnel responsible for conducting the blasting including
transporting of explosives, storage and maintenance of explosives, drilling,
installation of explosives and charge equipment, and detonation shall meet the
minimum qualifications listed below. The contractor will be required to submit
documentation to confirm the personnel assigned to the work meet these
requirements as specified in Section 01450 – Quality Control.
1. Personnel must have at least five years of experience with use of explosives for
underground rock blasting.
2. The person in charge of the blasting operation should have:
a. At least three years of experience as the blasting superintendent.
b. Performed a supervisory role for blasting operations on at least ten similar
type projects (water and/or sewer utility line construction).
3. Provide a list of OSHA violations (related to blasting) and associate fines issued
on projects that the proposed superintendent was involved with.
4. Provide a list of at least five references for projects with blasting completed in
the five years.

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H. Contractor is responsible for safety of life and damage to property resulting from the
use of explosives. The Owner and Engineer shall be made aware of all blasting
activities prior to their occurrence.
I. Provide services of a testing firm experienced in monitoring vibrations resulting from
blasting operations as specified in Section 01450, Quality Control.
J. In addition to the above testing/monitoring requirements required, Contractor shall
provide the services of a “third party” geotechnical testing firm experienced in
monitoring vibrations resulting from blasting operation as specified in Section 01450,
Quality Control. The firm selected shall be evaluated by the Engineer and Owner
for approval as the official “third party”.
K. Third Party testing/monitoring as related to blasting operations shall include the
following:
1. Pre-Construction Condition Assessment
a. Prior to beginning construction, the third party testing firm shall perform a
pre-construction condition assessment to document the conditions of
buildings and other sensitive structures within 200 feet of the proposed
blasting area. The assessment shall be performed on all adjacent
properties and any other properties as directed by the Engineer or Owner.
The assessment should include video and photographic documentation of
all exteriors including building foundations, and installation of crack
monitors on cracks that might occur or expand due to construction
vibrations. Provide all documentation described above to the Owner and
Engineer prior to construction.
2. Crack Monitoring During Construction:
a. During construction, the third party testing firm shall perform periodic
readings of the crack monitors installed prior to construction. Provide
readings to the Engineer and Owner within 48 hours of taking the reading.
If crack readings monitoring confirm that vibrations are not contributing to
crack width, crack monitors may be read once per week. More frequent
readings may be required by Owner or Engineer if construction activities
could result in greater earthborne vibrations. Testing firm shall notify the
Engineer and Owner immediately if monitoring indicates that construction
operations have contributed to crack widening. The testing firm shall
prepare a detailed plan for repaired the structure and the Contractor shall
repair the structure at no cost to the Owner. Contractor shall submit a plan
for review that proposes alternate construction methods to address the
vibration problems and minimize further damage.
3. Vibration Monitoring During Construction:
a. The third party testing firm shall monitor vibrations at no less than four
locations along the perimeter of the project and in accordance with
paragraph 3.07D above during all blasting activities. The locations shall be
based on the location of construction activities and their relative position to
offsite structures. Prior to construction, a plan showing the proposed
monitoring locations shall be submitted to the Engineer and Owner for
approval. Adjustments may be made to the locations upon approval. The
sensitivity range of the seismograph shall be selected such that the
recording is initiated below the maximum allowable particle velocity as
recommended by the U.S. Bureau of Mines with a twenty percent reduction
factor applied. Refer to Exhibit 1 at the end of this section for a chart
developed by the U.S. Bureau of Mines with the modified vibration

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requirements for the project and extends above the highest expected
intensity. Specific activities of the vibration source (i.e., blasting) shall be
indexed in time to allow correlation with the arrivals on the vibration.
b. The contractor shall notify the Engineer and Owner immediately if monitors
indicate that the vibrations are above the criteria established. Activities
causing the vibrations shall be suspended until a revised construction plan
has been developed by the testing firm to alleviate the problem. The
problem shall be resolved by the Contractor at no additional cost to the
Owner.
c. The vibration monitors shall consist of digital seismographs that display the
particle velocities and associated frequencies plotted against the criteria
established for this project. Each seismograph shall contain geophones
with response capability in three mutually perpendicular axes or
components; one vertical and two horizontal (radial and transverse). The
frequency response of the geophones shall be linear from at least 4 Hz to
more than 200 Hz. The sensitivity shall range from less than 0.02 in/sec to
more than 5.0 in/sec. The BlastMate III by Instantel is one type of
seismograph that is suitable for this project.
d. Vibration monitors shall be field calibrated by the testing firm before each
recording period. The transducer shall be positioned with the longitudinal
axis toward the vibration source. Transducers must be adequately coupled
with the ground. Operation and calibration of all equipment shall be per
manufacturer’s recommendations. Vibration records shall be collected in
waveform plot or strip chart plot. The peak vector sum of the particle
velocity in longitudinal, transverse, and vertical planes shall be shown
along with the respective dominant or principle frequencies. The highest
recorded particle velocity (i.e., the vector sum of the three orthogonal
directions), when indexed to a particle vibration event, shall be reported as
the peak particle velocity. The recorded peak particle velocity shall be
compared to criteria appropriate for the subject of concern.
e. The Engineer and Owner shall be notified immediately of any complaint
received by the Contractor. The Contractor shall immediately review those
construction activities inducing the vibration and prepare a report
documenting all relevant data such as the time and date of the complaint, a
description of the construction activities, data from the monitoring
instruments for the subject time/date, complaint information (including
photographs, if possible) of the alleged damage. The Contractor shall
submit for review a detailed plan for repair and revised construction plan to
address the vibration problems to minimize further damage and complaints.
The Contractor shall perform necessary repairs at no additional cost to the
Owner.
f. The testing firm shall provide monthly reports containing the results of the
crack monitors and vibration monitors during those activities that generate
earthborne vibrations, including but not limited blasting operations. The
reports shall document that the firm is provided the work described herein.
L. The Contractor shall be responsible for notifying property owners that own
any portion of property within a 1,000-foot radius of the proposed blast
location. Notifications shall be made by use of door hangers with wording to
be coordinated with the Engineer and Owner. Initial notifications shall be in-
place once construction activities are within 1,500 linear feet of the proposed
blast location measured along the proposed pipe center line. Notifications

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should also be made to local jurisdictions such as NCDOT, City/Town, etc. In
no case shall initial notifications be made later than five days prior to blasting.
Follow-up notifications in the same format shall be made between 24 and 48
hours of the intended start of the blasting for property owners with any
portion of property within the 1000-foot radius.
M. Submit monitoring reports in accordance with Section 01450, Quality Control.
N. Allowance established in Section 01270, Unit Prices, shall be utilized to pay for
costs of the third party monitoring.
O. The Owner reserves the right to require the removal of rock by other means if
blasting operations result in possible hazardous conditions.
P. The Contractor shall provide as contingency, on-site, by-pass pumping capability
when blasting within 100 feet of existing sanitary sewer infrastructure or where
required otherwise as noted on the Drawings or specified in other sections of the
project manual.
3.08 EXCAVATING
A. Excavation shall be by open cut, unless otherwise indicated on the Drawings or
specified herein. Other than where specifically indicated on the Drawings, short
sections of trench may be tunneled or direct bored with the approval of the
Engineer.
B. Stockpile excavated material in such a manner that it will not obstruct the flow of
runoff, streams, endanger Work, impair the use or appearance of existing facilities,
or be detrimental to the completed Work.
C. Contractor shall segregate excavated material so as to maintain material suitable for
backfill separate from material that is unsuitable.
D. Trench dimensions at the pipe embedment and foundation zone, shall be as
detailed on the drawings.
E. Shape trench bedding to provide uniform bearing for the full pipe length. Bottom
shall be free of protrusions that could cause point loading on pipe. Provide bell holes
as required for properly making pipe joint.
F. Do not over excavate. Excavation below grade without approval of Engineer shall be
backfilled with Class I material at no additional cost.
G. Undercut soils that become unsatisfactory by construction activity or by being left
exposed to the weather shall be replaced with Class I backfill material at no
additional cost.
H. Remove shoring, bracing, and sheeting, unless otherwise noted, as the trench is
backfilled. Engineer shall have the authority to require that the sheeting be left in
place. Once the trench box has been removed to the top of the pipe (or initial
backfill zone), the stone shall be replenished to have the required stone over the
pipe for the entire width of the excavation. This includes area displaced by the
trench boxes and any voids outside the box.
I. Excavation of trench shall not advance more than 100 feet ahead of the installation.
In no case should the excavation extend beyond that which can be backfilled by the
end of the workday.

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J. Correct unstable soil conditions encountered at trench foundation by the following
method:
1. Excavate below grade as approved by Engineer and backfill with Class I
material or approved substitute material at unit price bid as indicated in Section
01270, Unit Prices.
K. Rock and Hard Material
1. Excavate rock and hard material to a minimum depth of 6 inches below the
pipe. Excavation shall be backfilled with Class I material.
2. Mechanical removal of rock (i.e., no blasting) may be necessary along portions
of the project, as noted on the Drawings or as required by the applicable
regulatory agencies, where blasting could result in complications with
surrounding infrastructure. This method of rock excavation will be used only
when approved by the Owner, as the blasting method shall be the typical
method.
L. Pressure Lines:
1. Provide a minimum 3 feet of cover, unless indicated otherwise on the Drawings.
2. Excavate trenches to provide vertical curve chords that will not exceed the pipe
manufacturer’s recommended joint deflection.
3. Provide concrete thrust blocks having a compressive strength of 3,000 psi at 28
days at change in horizontal and vertical direction and reduction in the pipe
size, unless other restraint systems are indicated otherwise on the Drawings.
Cut trench sides vertical and square to receive concrete. Provide bearing area
against trench wall as indicated on the Drawings.
M. Gravity Lines:
1. Excavate trench to the alignment and grade indicated on the Drawings.
N. Utility Structures: Provide a minimum of 9 inches below subgrade and backfill with
Class I compacted to 95 percent maximum density. If the soil conditions are found
to be unsuitable for structural stability of the structure, Engineer may require
additional depth of Class I material. The additional Class I material will be paid for
under the appropriate bid item as indicated in the Bid Form.
3.09 BACKFILLING
A. Weather Limitations: Proceed with backfill operations based on the following
weather conditions:
1. Temperature must be above freezing and rising.
2. In windy, hot, or arid conditions with a high rate of evaporation add moisture to
the material to maintain the optimum moisture content.
3. Do not proceed in rain or on saturated subgrade.
4. Do not place material on surfaces that are muddy, frozen, or contain frost.
B. General
1. Maintain backfill operation within 100 feet from pipe laying operation.
2. Backfill trench to existing ground surface with select excavated material at the
specified compaction.
3. If excavated material is unsuitable to obtain specified compaction, provide
suitable off-site borrow material for backfill as approved by Engineer.
4. Re-excavate trenches improperly compacted. Backfill and compact as
specified.
5. Provide appropriate tamping equipment, and water to obtain proper moisture
content, to achieve specified compaction of backfill.

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6. Conduct operation of heavy equipment above pipe installation in such a manner
as to prevent damage to pipe.
7. Install warning / identification tape over utilities. Bury tape one foot below
finished grade above the utility.
8. Install tracer wire for non-metallic pressure pipe. Bury tracer wire one foot
below finished grade over the pipe. Wire shall be looped into valve boxes and
indication posts to allow access for direct contact location.
C. Backfill in pipe embedment zone (bedding, haunching, and initial backfill).
1. General:
a. Backfill with material as specified below. Material shall be free from objects
larger than 2 inches.
b. Where rock and hard material has been excavated below pipe bottom,
backfill and compact bedding with Class I material. Class II or III material
may be used for bedding with Engineer's approval unless specified
otherwise below.
c. Place backfill material to assure placement of material under pipe
haunches.
d. Take care during placement and compacting of material to avoid
movement of pipe.
2. Place backfill in bedding and haunching zones in 6 inch maximum lifts in traffic
areas and 12 inch maximum lifts in non-traffic areas and compact to 90 percent
density. Provide backfill material in pipe embedment zone as specified below.
a. Pressure Lines (Flexible and Rigid Pipe)
1) Excavation in Class I, Class II, Class III, and stable Class IV soils
suitable for bedding, the bedding surface shall provide a firm
foundation of uniform density. Backfill with select excavated material.
2) Excavation in Class V, unstable Class IV soils, running water, and
other unstable soil conditions, excavate a minimum of 6 inches below
pipe bottom and provide Class I material for bedding and haunch zone.
Backfill with Class I, II, or III material in initial backfill.
b. Gravity Sewer Lines, Rigid Pipe (ductile iron with liner and reinforced
concrete pipe)
1) Depth of cover 0 to 15 ft (Type 4 laying condition with modifications):
i) Provide Class I material for bedding and 1/8 pipe diameter (min. 4
inches) up from bottom of pipe. Backfill with Class I, II, or III
material in remainder of haunching zone and initial backfill. Refer
to details on Drawings for additional requirements.
2) Depth of cover 16 ft to 40 ft (Type 5 laying condition):
i) Provide Class I material for bedding and through embedment
zone to centerline of pipe. Backfill remainder of embedment zone
with Class I, II, or III material. Refer to details on Drawings for
additional requirements.
c. Gravity Sewer Lines, Flexible (Fiberglass Reinforced Pipe – FRP and PVC)
1) Depth of cover 0 to 40 ft:
i) Provide Class I material for bedding and through embedment
zone to 6” above the top of pipe. The maximum stone size shall
be 1.5” or to 1 times the pipe wall thickness, whichever is smaller.
Backfill remaining 6” of initial backfill with Class I, II or III material.
ii) Where indicated on Drawings or required by soil conditions, as
determined by the geotechnical engineer during construction, the

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Contractor shall include geofabric lining around embedment zone
as detailed on the Drawings.
D. Final Backfill
1. Backfill with materials free of stones and debris larger than 6 inches in
dimension. Place backfill in lifts not exceeding the thickness and compacted to
the minimum density specified below.
2. Lifts and density:
a. Undeveloped areas (i.e., forests, fields, and, croplands): Trench may be
filled with bulldozer blade provided material fall will not damage pipe.
Mound soil over the trench area sufficiently to settle level over time. Degree
of compaction shall be 85 percent.
b. Lawns: Backfill in 12-inch lifts and compact to 90 percent. Top 12 inches
shall be free of material with a dimension over 2 inches.
c. Roads (including Rights-of-way), drives, parking areas (including areas
within 20 feet), and adjacent to existing utilities: Backfill in 6 inch lifts
compact to 95 percent. Compact the final 8 inches below finished
subgrades beneath pavements/sidewalks to at least 100% of the soil’s
Standard Proctor maximum dry density within 2% of optimum moisture.
d. Within 20 feet of foundations: Backfill in 6-inch lifts compacted to 95
percent.
E. Utility Structures: Bring backfill to grade in even lifts on all sides. Lift depths and
compaction densities shall be as specified according to area of installation for pipe
above. Backfill against cast-in-place concrete structure only after concrete has
attained the specified 28-day compressive strength.
3.10 ANTI-SEEP COLLARS
A. Anti-seep Collars: Provide anti-seep collars to prevent groundwater flow along pipe
in wetlands as indicated on the Drawings. Collars shall extend past trench walls
and bear against undisturbed soils. Dimension of collars shall be as indicated on the
Drawings. Do not place stone in area of anti-seep collars.
B. Concrete Collar: Provide Class B concrete with minimum cement content of 5 sacks
per cubic yard (5.5 sacks for angular course aggregate); 6.8 gallons of water per
sack water-cement ratio; 2-4 inch slump range; and 28-day strength of 2,500 psi.
C. Clay Collar: Provide clay of medium to high plasticity with a soil classification of CL
or CH and a permeability of 10-5 cm / second. Place clay in 6-inch lifts and compact
by use of a mechanical hydraulic tamper to 95 percent.
3.11 SOIL TESTING
A. Provide services of a soil-testing firm as specified in Section 01450, Quality Control
and Section 02201, Special Construction Requirements.
B. Testing laboratory soil specialist shall be at the project site, upon request of the
Owner, to perform inspection and in-place density testing as specified in Section
02300 Earthwork.
C. Density tests shall be made in accordance with ASTM D-698, Standard Proctor
Method.
D. Submit test reports and soil specialist daily logs in accordance with Section 01450,
Quality Control.

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E. Allowances established in Section 01270, Unit Prices, shall be utilized to pay for
costs of the initial tests.
F. For each test that fails the compaction requirements, the testing firm, at the direction
of the Engineer, shall make two additional tests. Contractor shall pay for cost of
additional tests due to failure of compaction/density test.
G. Based on test results, make corrections, adjustments, and modifications of methods,
materials, and moisture content for proper trench compaction.
H. Refer to Section 02201, Special Construction Requirements for requirements
dealing with contaminated soils and groundwater from trench excavations.
3.12 PAVEMENT REMOVAL AND PATCHING
A. Repair damaged pavement structure.
B. Cut existing pavement for utility installation in straight lines generally parallel to the
utility. Properly dispose of removed pavement structure.
C. Extend pavement patch 1 foot beyond each side of trench on firm subgrade. Slope
new surface to drain.
D. Asphalt Pavements: Replace asphalt pavement with a pavement structure equal to
existing but no less than as detailed on the Drawings or as indicated in the
Encroachment Agreement, whichever is more stringent.
E. Concrete Pavements: Replace concrete pavement with pavement structure equal to
existing but no less than as detailed as Drawings. Concrete shall be minimum
3,000 psi. When existing concrete joint is within 5 feet of trench remove existing
concrete to joint. Provide expansion joint at edge of existing concrete. Surface
treatment shall match existing. For overlays, as indicated on Drawings, set new
driveway elevation at overlay depth and transition to existing driveway elevation.
F. Curbs, Gutters, and Sidewalks: Replace curbs and gutters, and sidewalks removed
or damaged with similar sections to match the existing. Remove to nearest existing
joint.
G. Approval of Other Authorities: Pavements under the jurisdiction of the NC Division of
Highways shall be subject to the approval of a representative of that Division.
H. For overlays, coordinate final limits with Owner, Engineer, and NC Division of
Highways. Perform in accordance with NCDOT Encroachment Agreement.
I. For overlays, as indicated on Drawings, raise existing and new manholes and valve
boxes to finished pavement grade. Excavate around top of existing manhole and
valve box as necessary. Remove existing top ring, and install new grade ring(s) as
necessary. Install existing cover. Raise existing valve box. Provide concrete collar
around manhole ring and valve box per details on the Plans.
J. See Section 02700, Pavement and Appurtenances for additional requirements.
3.13 GRADING AND CLEAN-UP:
A. Provide for testing and clean up as soon as practicable, so these operations do not
lag far behind the pipe installation. Perform preliminary clean up and grading as
soon as backfill is complete.

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B. Provide positive drainage of finished grade and drain away from structures. Finished
grade shall be reasonably smooth, compacted, free from irregular surface changes
and comparable to the adjacent existing ground surface.
C. Seed disturbed areas in accordance with Section 02920, Lawns and Grasses.
D. Upon completion of backfilling, remove and properly dispose of excess material and
waste. Surplus materials shall be disposed in an Owner-approved facility. A list of
approved facilities is available from City of Raleigh Public Utilities Department. The
Contractor may submit an alternate facility for Owner approval, prior to utilization, in
accordance with the Contract Documents.
END OF SECTION