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STANDARD SPECIFICATIONS

SECTION 02315

EARTHWORK FOR PIPELINE CONSTRUCTION

PART 1 GENERAL

1.1 DESCRIPTION

A. Section includes requirements for excavation, backfill, grading, and related items for pipeline construction.

1.2 DEFINITIONS

A. Trench Zones.

1. Pipe Embedment Zone: Area surrounding pipe in trench, consisting of Bedding Zone, Haunching Zone, and Initial Backfill Zone defined herein.

a. Bedding Zone: Area from pipe bottom to firm subgrade, extending full width of trench and providing support for pipe shown in Standard Details.

b. Haunching Zone: Area from pipe bottom up to as far as spring line and extending full width of trench shown in Standard Details.

c. Initial Backfill Zone: Area from top of Haunching Zone up to as far as 1 foot above top of pipe and extending to full width of trench shown in Standard Details or specified herein.

2. Final Backfill Zone: Area from top of Pipe Embedment Zone to finished grade, extending full width of trench shown in Standard Details.

3. Additional Excavation: Excavation below trench bottom to remove unsuitable material such as rock, cobble, soft or organic soil, when Engineer determines that material is unsuitable to support pipe. Additional excavation shall be performed until acceptable material is reached or a depth of one (1) foot, whichever is less.

B. Backfill Material.

1. Trench Backfill: Native or Borrow Material placed in trench excavation and meeting specifications herein.

2. Borrow Material: Suitable material used for Trench Backfill provided from locations outside limits of trench excavation and meeting specification requirements herein.

3. Bank run gravel: Aggregate material consisting of gravel and sand size particles taken directly from natural deposits, screened and meeting specification requirements herein.

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4. Crushed stone: Aggregate materials, including crusher run aggregate and graded aggregate base, produced by mining a suitable rock deposit, breaking the removed rock down to the desired size using mechanical crushers and meeting specification requirements herein.

5. Structural Fill: Compacted Trench Backfill meeting specification requirements herein, to minimize future settlement and provide support or bearing for structures to be constructed upon or within fill.

C. Pipe.

1. Rigid Pipe: Reinforced Concrete Pipe (RCP), Cast Iron Soil Pipe, Cast Iron Pipe, Prestressed Concrete Cylinder Pipe (PCCP), Asbestos Cement Pipe, Vitrified Clay Pipe, and Concrete Sewer Pipe.

a. Pipes relying primarily on inherent strength to support external vertical load.

2. Flexible Pipe: Ductile Iron Pipe (DIP), Polyvinyl Chloride (PVC) Pipe, and Type K Copper Pipe, Steel Pipe, and High-Density Polyethylene (HDPE) Pipe.

a. Pipe deriving its supporting strength primarily from passive pressures induced as pipe flexes outward against material in Pipe Embedment Zone.

D. Controlled Blasting: Method used to fracture and excavate rock to required limits for trench while minimizing overbreak and fracturing.

E. Paved Areas: Over which paving exists, or is to be placed under this Contract, or areas designated on Drawings to receive future paving: See Section 02950.

F. Wetland Areas: Non-tidal Wetlands and Non-tidal Wetlands Buffer Zones.

G. Percent compaction: Ratio, in percent, of as-compacted field dry density to laboratory maximum dry density as determined per ASTM D 698 (AASHTO T 99) or ASTM D 1557 (AASHTO T 180) as specified.

H. Optimum Moisture content: Gravimetric water content determined in accordance with ASTM Standards at which a specified maximum dry density can be achieved for a specified percent compaction.

I. Lift: Loose and uncompacted layer of material placed before compaction

J. Peak particle velocity: Maximum of 3 velocity components of a vibration measured at any point in 3 mutually perpendicular directions by Engineer approved seismograph, capable of producing permanent record and capable of internal dynamic calibration.

1.3 QUALITY ASSURANCE

(Service Connection Contracts (AC, LC and SC) only)

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A. Inspection and Testing.

1. Placing trench backfill and earthwork is subject to continuous inspection.

a. The Engineer may perform field density tests of compaction of each layer of fill following ASTM D1556, ASTM D6938, or ASTM D2937

2. Contractor shall allow time for Engineer to perform tests after completion of each layer of fill in designated area.

3. Contractor shall provide safe access and equipment to cut out smooth-surfaced spot locations designated by Engineer for testing.

4. Engineer may perform gradation and other tests on trench backfill.

(All other contracts) B. Inspection and Testing.

1. Quality Control (QC) Personnel Qualification: All field and laboratory tests shall be performed under the direct supervision of a Maryland Registered Professional Engineer with a minimum of five (5) years of experience in construction inspection of geotechnical projects. QC soil technicians performing field tests shall maintain at least one of the following certifications:

a. Washington Area Council of Engineering Laboratories (WACEL):

certification for foundation technician

b. Mid- Atlantic Region Technician Certification Program (MARTCP) by

Maryland State Highway Administration (SHA): certification for soils & aggregate compaction technician

c. Any data collected or material produced as a result of compaction testing or reporting must be made available to the Commission. If a photograph is required by the Commission to validate the data, the contractor or 3rd party Geotechnical Engineer/Firm must allow the photograph to be taken.

2. Field Density Compaction Tests: Perform tests following ASTM D1556, ASTM

D6938, or ASTM D2937 at minimum rate of 1 test location for every 100 feet of fill for each lift along main trench and at every lateral trench (WHC, SHC, etc.), structure and valve box in Type I areas. If less than 100 feet of pipe is placed in a day, conduct at least 1 test per lift. Testing shall be performed on each lift in the pipe embedment zone and the final backfill zone starting from six (6) inches above the bottom of excavation to the finished grade as shown on WSSC Standard Details.

Any additional excavation shall be backfilled with suitable materials and compacted. The testing mandate shall apply to each crew working on a project if there are multiple crews working at different locations.

a. When field-testing indicates differences in soil types, reference and/or verify test results using one-step field proctors or laboratory proctors following

ASTM D698 (AASHTO T99).

1) For work on State, County or other roads with jurisdictional requirements: When field-testing indicates differences in soil types, reference and/or verify test results using one-step field proctors or

02315-4 2026 laboratory proctors following ASTM D698 (AASHTO T99) for the compaction of the pipe embedment zone (haunch and initial backfill zones). If more restrictive, use the jurisdictional requirements for the final backfill zone. For backfilling in the pipe embedment zone, follow the WSSC requirements specified herein.

b. When backfill material is known to contain bound hydrogen, a field moisture content test per ASTM D2216-10 or ASTM D4944-04, shall be performed and moisture corrections shall be made in accordance with “Virginia Department of Transportation Soils and Aggregate Compaction Field Certification Study Guide (2019)”.

c. Perform field density compaction test as new mains, laterals and structures are installed.

d. Re-excavate and recompact failed test areas, at 25-foot intervals, the entire trench depth and entire 100 feet length until retests meet above referenced standards. Rework shall be performed under the supervision of the Engineer.

A failed test area is defined as any area where settlement occurs above the WSSC settlement limitations specified herein or if the Contractor fails to submit proper compaction reports demonstrating full compliance with this specification.

e. Certified compaction test reports must be submitted to the WSSC contract manager within five (5) business days of the work being performed.

3. Placing Trench Backfill and earthwork is subject to continuous inspection by

WSSC.

d. Allow time for Engineer to perform spot tests after completion of each layer of fill in designated area.

e. Provide safe access and equipment to cut out smooth-surfaced spot locations designated by Engineer for testing.

f. WSSC may perform gradation and other tests on Trench Backfill.

C. Finished Grade Settlement Limitations.

1. Guarantee backfilled trench excavation areas designated on Drawings will not pond or settle in excess of following limitations. The settlement limitations apply to both temporary and permanent patches.

Designation Settlement Limitations Locations Type I 0.05 foot Paved areas and public rights of way Type II with positive drainage Unimproved areas Type III 0.10 foot Nonpaved improved areas Type IV 0.00 foot Wetlands or wetlands buffer

2. Remove and replace Trench Backfill which settles in excess of above limitations with suitable material at no cost to the Commission. Rework shall be performed per section 1.3.B.2.d.

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3. Remove and replace piping, structures, paving, landscaping, and other site improvements damaged by settlement or repair following Contract Documents, at no cost to the Commission.

1.4 SUBMITTALS

A. Submit following Section 01330.

1. Working drawings and data to show blasting design and monitoring

a. Submit request and obtain written permission from Engineer before using explosives.

b. Submit details of blast design including burden thickness and direction of relief, hole diameter, hole spacing and depth, stemming material and length of stemming, delay pattern, blasting agent specifications, blasting mat locations and blast design calculations

2. Working drawings showing sheeting and shoring, and method of dewatering, for structure excavations deeper than 8 feet and larger than 400 square feet.

3. Samples of Borrow Material, except for Borrow Aggregate.

a. Size: Minimum of 30 pounds in sturdy cloth or plastic bags.

b. In addition to sample identification required in Section 01330, clearly label each sample showing type and material designation, intended use, name and address of supplier, and location where material is mined or manufactured.

B. Delivery of Borrow Material.

1. Submit prior notification of source, designation, quantity, and intended use for all Borrow Material.

2. Submit delivery tickets with each load of Borrow Material.

a. Name and location of supplier.

b. Type and amount of material delivered, including ASTM’s and the

Commission’s material designations.

c. Proctor Report per ASTM D1557/AASHTO T180 for MSHA highways or per

ASTMD698 for all other areas.

C. Submit following Section 01450.

1. Certificate of Compliance: When recycled concrete is used, submit letter from governing jurisdiction or WSSC approving its use.

2. Certified Test Reports: Borrow Aggregate and Recycled Concrete.

a. In addition to requirements of Section 01450, include information showing type and material designation, intended use, name and address of supplier, and location where material is mined or manufactured.

b. Proctor Report per ASTM D1557/AASHTO T180 for MSHA highways or per ASTM D698 for all other areas.

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D. For Flowable Fill see Section 03300.

E. Submit Soil’s Compaction Reports including for Type III areas (except Service

Connection Contracts (AC, LC and SC) as follows:

1. Certified by Professional Engineer registered in State of Maryland.

2. Borrow material – Soil classification results per ASTM D2487 including gradation per ASTM D6913 /D7928 as applicable and Atterberg limit tests per ASTM D4318

2. Field Density Compaction Test Results. Include all corrections used on field compaction tests conducted per ASTM6938

3. Contract Number.

4. Soils Technician’s Name and Employer, including WACEL or MARTCP certification number.

5. Test Number.

6. Date of Test.

7. Location of Test (sewer and/or water station, lot number and street name).

8. Retest results of previous tests (and number).

9. Depth of Test.

10. Dry Density.

11. Moisture Content, including moisture content correction worksheet, if required for bound hydrogen (see “Virginia Department of Transportation Soils and Aggregate Compaction Field Certification Study Guide (2019)” - Form TL-124).

12. Maximum Density/Optimum Moisture Curve Relationship Chart following ASTM D698. This document shall be included in each test report.

13. Test Results.

14. One Step Proctor Determination (when taken). This document shall be attached to field report submittal.

15. Additional Comments.

16. Submit test results to the Engineer within 2 days of test and 3 business days prior to testing mains and service connections and/or performing tie ins.

PART 2 PRODUCTS

2.1 MATERIALS

A. Detectable Warning Tape Furnished by the Commission.

1. Description.

a. Size: Six-inch width, minimum 5 mils thickness.

b. Printing: Two lines, minimum 3/4-inch-high lettering on each line, repeated continuously along length of tape at intervals no greater than 3 feet.

1) Water: CAUTION - WATER LINE BURIED BELOW

CALL WSSC 301-206-4002

2) Sewer: CAUTION - SEWER LINE BURIED BELOW

CALL WSSC 301-206-4002

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3) Cathodic Protection: CAUTION – CATHODIC PROTECTION

CALL WSSC 301-206-4002

c. Colors.

1) Tape:

a) Blue for water.

b) Green for sewer.

c) Yellow for cathodic protection.

2) Lettering: Black.

2. Approved Manufacturers:

a. Empire Level Mfg. Corp., Magnatec

b. Pro-Line Safety Products (A Division Of Pro-Pak Ind., Inc.); Product Nos.

103141251wssc (blue), 103143191wssc (green), and 103128013wssc (yellow)

c. Reef Industries, Terra Tape Sentry Line Detectable

B. Non-Detectable Warning Tape Furnished by the Commission.

1. Description.

b. Size: Six-inch width, minimum 4 mils thickness.

c. Printing:

1) Option 1: Two lines, minimum 1-inch-high lettering on each line, repeated continuously along length of tape at intervals no greater than 2 feet.

a) Restrained joint pipe: CAUTION – RESTRAINED JOINT PIPE

b) CALL WSSC 301-206-4002

c) The international “no-dig symbol” shall follow each cycle of text

2) Option 2: Three lines, minimum 1-inch-high lettering on each line, repeated continuously along length of tape at intervals no greater than 2 feet.

a) Restrained joint pipe: CAUTION RESTRAINED JOINT PIPE

b) CALL WSSC 301-206-4002

c) The international “no-dig symbol” shall follow each cycle of text

d) Colors.

3) Tape:

a) APWA Red for restrained joint pipe.

4) Lettering: Black.

2. Approved Manufacturers:

a. Blackburn Manufacturing Co. Inc., Non- detectable Underground Utility Warning Tape

b. Empire Level Utility Products Division, Shieldtec Underground Warning Tape

c. In Stock Now! Inc., Non-Detectable Warning Tape, Product No. Nd6rdci

d. Mutual Industries, Non-Detectable Underground Marking Tape, Product No.

17783

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e. Pro-Line Safety Products (a division of pro-pak ind., inc.), Standard 4 mil Non-detectable, Product No. 104346283wssc.

f. Reef Industries, Inc., Terratape Standard Non-detectable

g. Safety Sign Company, Warnoline Underground Utility Warning Tape

C. Trench Backfill.

1. General Trench Backfill Requirements.

Outside Wetland Areas: Free of organic or frozen material, waste metal products, construction debris, unsightly debris, toxic material, environmentally contaminated soils, materials removed as rock excavation or other deleterious materials and at moisture content permitting compaction to density specified.

1) Clean coarse-grained soils classified per ASTM2487 as GW, GP, SW, SP

2) Coarse grained soils with fines, Sandy or Gravelly fine-grained soils classified per ASTM2487 as GM, GC, GW-GC, SP-SM, SM and SC

3) In organic fine-grained soils with less than 30% retained on No. 200 sieve classified per ASTM2487 as ML and CL

b. Within Wetlands Areas: Previously excavated native material which can include organic matter, but free of frozen material, waste metal products, unsightly debris, toxic material, or other deleterious materials used only for final backfill zone

c. Fine grained soils with organics classified per ASTM D2487 as MH, CH, OL, OH or Pt shall not be used in the pipe embedment zone.

d. Material Excavated from Trench meeting the requirements stated herein: Use when approved by the Engineer; otherwise excavate, haul, and place Borrow Material.

2. General Borrow Material Requirements.

a. Outside Wetland Areas: Meet General Trench Backfill Requirements for

Outside Wetland Areas, stated herein.

b. Within Wetland Areas: Soil material meeting requirements of ASTM D2487 or 2488, material classification types of SM, SC, ML, or CL but be free of frozen material, waste metal products, unsightly debris, toxic material, or other deleterious materials used only for final backfill zone.

c. Acceptance of Borrow Material from any location outside limits of trench excavation, shall not be construed as approval of entire Borrow Material site, but only insofar as material continues to meet specified requirements, herein.

3. Borrow Aggregate.

a. Standard Sizes of Aggregate: ASTM C33, coarse aggregate.

b. Dry Concrete Sand: ASTM C33, fine aggregate.

c. Graded aggregate base (GAB), Crusher Run aggregate (CR-6), or bank run gravel.

1) Aggregate Test Requirements:

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a) Maximum Sodium Sulfate Soundness (ASTM C88):12 percent.

b) Maximum Los Angeles Abrasion (ASTM C131): 50 percent.

c) Maximum Flat and Elongated (ASTM D4791) for crushed stone only:

15 percent.

2) Gradations: Conform to Table of Borrow Aggregate Gradations.

Borrow Aggregate Gradations

(Based on Table “901-A”, July 2024 Maryland State Highway Administration (MDSHA) Standard Specifications for Construction and Materials)

4. Flowable Fill: Section 03300.

5. Recycled Concrete: Free of waste metal products, unsightly debris, toxic material or other deleterious materials and meeting Gradation and Aggregate Test Requirements for Borrow Aggregate, as stated herein.

6. Bentonite: 100 percent high-swelling granular sodium Bentonite, with maximum moisture content of 12 percent.

a. Approved Manufacturers:

1) American Colloid Company.

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2) Wyo-ben Inc.

3) Bentonite Performance Minerals LLC.

7. The contractor shall at no additional cost to the Commission, have a qualified testing laboratory specified herein, to provide tests per ASTM D1557/AASHTO T180 for MSHA highways or per ASTM D698 for all other areas. The Contractor shall provide proctor tests for each type of material or change of material regardless of whether the material is excavated or borrowed.

8. Structural Fill: Meet material requirements of Trench Backfill and compaction requirements stated herein.

9. Backfill Requirements for Different Types of Pipes.

a. Additional Excavation Area Below Pipe Embedment Zone for Outside and

Within Wetland Areas:

1) Compacted general trench backfill meeting requirements

2) Borrow Aggregate meeting requirements of ASTM C33, coarse aggregate size number 57

3) Use geotextile to separate pipe embedment zone material and aggregate in additional excavation area when migration of fines is a concern.

b. Pipe Embedment Zone: Requirements for Outside and Within Wetland Areas

Specified below for each pipe material:

1) Recycled concrete shall not be used in pipe embedment zone.

2) Type K copper pipe and standard asphaltic coated, external coating system or polyethylene encased DIP 24 inch and smaller, following Standard Detail M/8.1a:

a) Specified in General Trench Backfill Requirements for Outside

Wetland Areas.

b) Containing no rock or gravel larger than 1-1/2 inches in greatest dimension.

c) Liquid limit: Not to exceed 30.

d) Plasticity index: Not to exceed 6.

e) Dry density: Not less than 105 pounds for each cubic foot as determined by ASTM D698.

3) Standard Asphaltic Coated, external coating system or Polyethylene

Encased DIP, Larger than 24 inch:

a) Pipe embedment zone: Following Standard Detail M/8.1b:

(1) Borrow Aggregate:

(a) Bank run gravel or

(b) Graded aggregate base as specified herein, containing no rock or gravel larger than 1-1/2 inches in greatest dimension.

4) PVC Gravity Sewer Pipe, following Standard Detail M/8.1c:

a) Borrow Aggregate ASTM C33, coarse aggregate size number 67 as specified herein.

5) RCP, following Standard Detail M/8.0:

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a) Borrow Aggregate for Bedding Zone and Haunching Zone.

(1) Circular RCP: ASTM C33, coarse aggregate size number 4 and containing no rock or gravel larger than 1-1/2 inches in greatest dimension or coarse aggregate size number 57.

b) Initial Backfill Zone: Specified in General Trench Backfill Requirements for Outside Wetland Areas.

(1) Containing no rock or gravel larger than 1-1/2 inches.

(2) Liquid limit: Not to exceed 30.

(3) Plasticity index: Not to exceed 6.

(4) Maximum dry density: Not less than 105 pounds for each cubic foot as determined by ASTM D698.

6) PVC and HDPE Pipe for Pressure Sewer System: Standard Detail PS/1.0.

a) Borrow Aggregate ASTM C33, coarse aggregate size number 8 as specified herein.

7) PVC AWWA C900/C905 Pipe: Standard Detail.

a) Pipe with 10 feet or less cover:

(1) Specified in General Trench Backfill Requirements for Outside Wetland Areas.

(a) Containing no rock or gravel larger than 3/4 inch in greatest dimension.

(b) Liquid limit: Not to exceed 30.

(c) Plasticity index: Not to exceed 6.

(d) Maximum dry density: Not less than 105 pounds for each cubic foot as determined by ASTM D698.

(2) Bedding Zone: May use Borrow Aggregate meeting ASTM C33, coarse aggregate size number 67.

b) Pipe with greater than 10 feet cover:

(1) Borrow Aggregate ASTM C33, coarse aggregate size number 67 specified herein.

c. Final Backfill Zone Materials Outside Wetland Areas:

1) Specified in General Trench Backfill Requirements.

2) Containing no rock or gravel larger than 3 inches from top of Pipe

Embedment Zone to 2 feet above.

3) From 2 feet above Pipe Embedment Zone to finished grade, no rocks larger than 8 inches in greatest dimension, unless contained in sufficient matrix of soil to avoid point to point contact, except:

a) Service Connection Contracts (AC, LC, and SC), Type I areas, under existing paving:

(1) State and county arterial roads and shoulders: Crushed stone.

(2) Other roads: Same as for all other Contracts specified below.

Or,

a) All other Contracts, Type I areas, under existing paving, top 30 inches below pavement base course, unless indicated otherwise in

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Trench Detail for Paved Areas located under ATTACHMENTS included in the contract documents: Borrow Aggregate, Graded Aggregate Base. Flowable fill and recycled concrete may be used instead of Borrow Aggregate, as specified below:

(1) Flowable fill, unless otherwise shown on Drawings, from top of

Pipe Embedment Zone to below pavement base course, if approved by roadway governing jurisdictions.

(2) Recycled concrete for PVC pipes only, as specified below.

(a) Allow at least 12-inch separation between top of PVC pipe and recycled concrete.

(b) Do not use recycled concrete if PVC pipe crosses or is within

10 feet or 5 pipe outside diameters horizontally, whichever is greater, to existing non-PVC pipe.

(3) Recycled concrete shall not be used for other types of pipe.

b) Type I areas, under future paving and within 5 feet of structure, and Type III areas: Top 12 inches below proposed pavement base course or finished grade containing no rocks or gravel larger than 3 inches.

d. Final Backfill Zone Materials within Wetland Areas: Specified in General Trench Backfill Requirements, herein.

e. If #57 stone is used, it shall be wrapped with Class SE geotextile per MDSHA specifications.

D. Backfill Requirements for Structures.

1. Granular Bedding for Precast or Cast-in-place Structures:

a. Granular Bedding Borrow Aggregate: ASTM C33, coarse aggregate size number 3.

b. Borrow Aggregate for Additional Excavation Area below Granular Bedding:

ASTM C33, coarse aggregate size number 3 .

2. Granular Bedding for On-Grade Slabs: Borrow Aggregate meeting ASTM C33, coarse aggregate size number 3.

3. Backfill for Precast or Cast-in-place Structures: Trench Backfill in Final Backfill

Zone, unless otherwise shown on Drawings.

a. Flowable fill may be used instead of Trench Backfill material for circular shape precast and cast-in-place concrete manholes.

E. Trench Erosion Checks.

1. Wood: Follow Standard Details.

F. Sheeting, Shoring, and Bracing Materials.

1. Timber, steel, or combination thereof, designed as required to retain earth around structure, prevent cave-in and settlements, and to fulfill MOSH safety requirements.

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a. Timber: Structural grade with minimum working stress of 1,100 psi.

b. Steel Sheet Piling: ASTM A328, continuous interlocking type.

c. Struts, Bracing, and other Accessories Required for Sheet Piling System:

ASTM A36.

PART 3 EXECUTION

3.1 EXCAVATION

A. General: Excavate to lines and grades indicated on Drawings.

1. On-grade Slabs and Pavements: Sufficient to allow for fills, base, and waterproofing materials.

2. Planting Areas: Sufficient to allow for topsoil.

3. Formed Concrete: Sufficient to allow for convenient construction and removal of forms, and for application of waterproofing and curing materials.

B. Test Pit Excavation: Perform with caution and to prevent damage to facility.

1. Special Requirements: Section 02510, Section 02530, and Section 02533.

C. Material Storage and Disposal of Unsuitable Material.

1. Separate and protect excavated material which is suitable Trench Backfill from contamination by unsuitable excavated material or by other sources.

2. Stockpile suitable materials in location approved by Engineer to avoid contamination and prevent erosion.

3. See Section 01110 for off-site disposal of excess excavated material and unsuitable material.

4. See Section 02230 for site clearing and storage of existing topsoil.

D. Unauthorized Excavation: Where excavations are made below indicated elevations under slabs, footings, pipes, structures, or outside maximum trench pay widths, restore to proper elevations with materials specified herein at Engineer’s direction, at no cost to the Commission.

E. Trench Excavation.

1. Excavate trenches to width and depth following Standard Details, Drawings, or specified herein.

a. Sides of trenches within Pipe Embedment Zones: Practically plumb.

2. Trench widths within Pipe Embedment Zone for Rigid Pipe shown on Standard Details are maximum widths. Trench excavation in paved roads

a. Keep heavy equipment as far away as possible from the edges of trenches to minimize trench wall sloughing.

b. Clearly mark cut boundaries perpendicular or parallel to roadway and traffic.

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c. Full depth bound pavement materials should be cut using saw cut, mechanical hammer or other appropriate methods that minimizes damage to adjacent pavement sections.

d. Use of a backhoe bucket to directly break pavement is not allowed.

e. Do not rock mechanical hammer while cutting pavement.

3. Remove rock, when encountered, to minimum depth of 6 inches below pipe barrel and pipe bell and structures.

a. Excavate trench bottom to conform to shape and dimensions of proposed pipe or structure.

b. Excavate bell holes in trench bottom to permit proper assembling of joints.

c. Support pipe or structure uniformly and continuously, upon specified material.

4. Where material not meeting requirements of Trench Backfill and deemed unsuitable by the Engineer is encountered either contiguous to or within proposed limits of excavation, the Engineer may direct additional excavation and removal of unsuitable material.

a. Depth and extent of additional excavation at Engineer’s determination.

b. Do not use saturated excavated material from trenches as a backfill.

5. Perform excavation in immediate vicinity of adjacent and crossing facilities by means that will not damage facility.

a. Excavate within 1 foot of existing pipelines or conduits by hand.

b. Repair or replace damage caused to existing facilities, pipelines, or conduits at no cost to the Commission.

6. Unless otherwise authorized by the Engineer, proceed with trench excavation no more than 40 feet in advance of placing of Trench Backfill.

a. The Engineer may require backfilling and subsequent re-excavation on trenches left open in advance of pipe installation, at no expense to the Commission.

b. Protect or enclose trenches left open overnight, or during periods when Contractor's personnel are not present and mark to prevent danger to public or others.

7. Excavate sides of trenches in improved public areas and adjacent to other utilities or structures practically plumb.

a. When crossing under existing pipes or conduits, plumb sides of trench from 1 foot above top of existing pipes or conduits to bottom of trench.

b. With Engineer’s permission, sides of trenches in other areas may be sloped from 1 foot above top of pipe to finished grade, at no additional cost to the Commission.

8. Trench Sheeting, Shoring, and Bracing: Place so as not to interfere with construction work and be entirely independent of footings and structures.

a. Method, design and adequacy of sheeting, shoring and bracing: Meet requirements of MOSH.

1) Repair damage related or caused by excavation at no cost to the

Commission.

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2) Sheeting, shoring, and bracing: Before placement, use means acceptable to the Engineer for its removal as backfill progresses.

b. Sheet and shore as required to assure safe working conditions, maintain required excavation dimensions for proper construction, and to prevent accidents, cave-ins, and damage to adjacent structures, facilities, and surfaces.

1) In excavations over 4 feet in depth, where Commission personnel are required to enter, sheeting and shoring shall meet requirements of MOSH for Type "C" soil conditions.

c. Remove sheeting, shoring, bracing and wood forms concurrently with backfilling operations, except in Pipe Embedment Zone and where sheeting is used as 1 side of form for concrete.

1) Accomplish removal in manner that precludes settlement of backfill, cave-in of excavation sides, and prevents damage to adjacent surfaces.

2) Promptly fill voids left or caused by removal.

3) Compact contiguous areas concurrent with removal of trench sheeting.

d. Follow Standard Details where sheeting is used for trench width between interior faces of sheeting.

e. Sheeting may be left in place, if following are met:

1) Positive verification that no voids exist between sheeting and trench wall.

2) Upper wales and horizontal braces are removed, or excavation is backfilled with sand.

3) Existing voids are filled following Trench Backfill requirements.

a) Sheeting left in place: Cut off minimum of 1-1/2 feet below finished grade or at Engineer’s direction.

9. Trench Boxes or Mules: Use of trench boxes: Permitted in areas where excavation sidewalls are suitable and where sheeting, shoring, and bracing are not required to maintain excavation dimensions.

a. Structural box design: To withstand pressures imposed thereon.

1) Trench boxes and steel plates and their use: Meet requirements of MOSH.

b. Location:

1) Do not extend trench box below top of Pipe Embedment Zone during or after placement of Pipe Embedment Zone material.

2) Remove steel plates used below trench box in Pipe Embedment Zone simultaneously with placement of Pipe Embedment Zone material and before its compaction.

c. Box size:

1) Height: Sufficient to assure safe working conditions.

2) Length: To accommodate size and lengths of pipe being installed.

3) Width: For trench opening not more than maximum permitted in Standard

Details.

F. Rock Excavation.

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1. Investigate to determine if rock is present, whether or not it is indicated within Contract Documents.

a. Presence or absence of rock will not entitle Contractor to additional compensation.

2. When blasting, control fly rock and material to prevent injury or damage to persons or properties.

a. Use blasting mats in areas where overburden has been removed before blasting, or as required to control fly rock.

b. Equipment used for drilling holes shall have positive means of dust control and meet OSHA and other applicable regulations and agencies requirements in asbestos-bearing rock area.

3. Blasting unless otherwise directed by the Engineer:

a. No closer than 10 feet to existing water, gas, sewer, or conduit utilities unless such facilities have been completely exposed, located, and then backfilled before blasting.

b. No closer than 2 feet from located existing utilities, 10 inch or smaller diameter.

c. No closer than 5 feet from utilities larger than 10-inch diameter.

4. Use controlled blasting techniques.

a. Modify blasting round as necessary to achieve best obtainable results and to keep air blast over pressure, vibrations, and noise within limits herein specified.

1) Exercise care in drilling and blasting operations to minimize over break and blast damage of adjacent unexcavated ground.

2) Produce satisfactory excavated surface by determining proper relationships of burden, spacing, depth of charge, amount and type of explosive, hole size and delay pattern, and other necessary considerations to achieve required results.

5. Vibration and Air Blast Control.

a. Control operations to ensure:

1) Peak particle velocity (PPV) will not exceed 2 inches per second measured adjacent to any structure in vicinity of blasting operations or following limits for concrete:

Inches per Second Age of Concrete

0.25 12 - 24 hours

0.5 24 - 48 hours

1.0 48 hours - 5 days

2.0 5 plus days

2) PPV limits above may further be reduced or no blasting may be imposed at the discretion of WSSC upon review of blasting submittals and condition of structures.

3) Impact or impulsive noise from blasting operations will not exceed 140 db peak sound pressure level measured at nearest structure or property line.

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b. Furnish seismograph instruments, qualified personnel to operate instruments, interpret results for all blasting operations, and submit copy of results to the Engineer.

c. Record air blast over pressure with peak impact recording instrument having linear frequency response and submit copy of results to the Engineer.

6. Repair or replace facilities damaged by blasting operations at no cost to the Commission.

7. Replace rock which is not broken to meet backfill requirements with suitable Trench Backfill, as specified herein.

G. Dewatering and Drainage.

1. Investigate to determine if water is present, whether or not it is indicated within Contract Documents.

a. Presence or absence of water will not entitle Contractor to additional compensation.

2. If water is encountered in excavation, install, and maintain dewatering system of sufficient capacity to remove it during excavation, pipe placement, and backfill.

a. For structures:

1) Until concrete footings have been poured and cured,

2) Walls or other portions of structure are erected to grade,

3) Or until excavation has been backfilled.

b. Do not allow sediment-laden water to flow into watercourses, drainageways, or over land without first filtering it through approved desilting device. See Section 01570.

3. Choose methods of dewatering excavations including, but not limited to, sump pumps, wellpoints, deep wells, drainage blankets, and tight sheeting.

a. Continuously inspect dewatering system to ensure it is functioning properly.

b. Ensure system does not disturb or degrade final subgrade for new pipe or structure and does not cause damage or settlement to adjacent surfaces or structures.

c. Modify system as required, and repair or restore damage or disturbance caused by system at no cost to the Commission.

d. Install necessary temporary surface drainage and keep it operating to Engineer’s satisfaction, until permanent drainage or finish grading has been completed.

e. Do not allow damming or ponding of water in gutters or storm drains.

4. Remove dewatering devices upon completion of work at Engineer’s direction.

3.2 BACKFILL OPERATIONS

A. Placing Trench Backfill.

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1. Backfill trench excavations with soils material excavated there from, provided this material meets requirements of Trench Backfill as specified herein and at Engineer’s approval.

2. Do not place, spread, or compact frozen or thawing material or place specified materials upon frozen or thawing ground or during unfavorable weather conditions.

a. When work is interrupted by rain, do not resume backfill operations until field tests indicate moisture content and density of materials are within specified limits.

b. Rework and recompact after thawing compacted layers which have been frozen before next layer is placed.

c. Interruptions in backfill operations due to weather: At no cost to the Commission.

3. Mix each lift before compaction to ensure uniform distribution of water content and distribute rocks of permissible sizes through material.

4. Place Trench Backfill and utilize compaction equipment that will not damage structures, pipe, and appurtenances.

a. Place and compact Trench Backfill around pipe and structures evenly to preclude unbalanced pressure.

b. Compaction with large rollers or heavy equipment will not be permitted within

5 feet of structures.

c. Repair damage done during backfill operations or replace at Engineer’s direction, at no cost to the Commission.

5. Place Trench Backfill in uniform lifts of 8 inches maximum in uncompacted thickness, unless otherwise specified herein.

a. Spread each layer uniformly and evenly.

b. Perform compaction using compacting rollers, pneumatic or vibratory compactors, or other equipment and methods with Engineer’s approval.

6. When Borrow Material is utilized, place in uniform lifts of 8 inches maximum in uncompacted thickness, or at Engineer’s direction.

a. All compaction work shall be performed using suitable equipment such as sheep foot roller or pneumatic and/or vibratory plate type compaction equipment. Cohesive fine grained backfills are best compacted with pressure, impact or kneading equipment. cohesionless backfills are best compacted with vibration equipment.

b. Use of backhoe buckets is not permitted for gravel compaction.

7. Backfill Structural Fill in uniform lifts of 8 inches maximum in uncompacted thickness and compact to not less than 95 percent of maximum dry density, following ASTM D698, at moisture content within 2 percent optimum for material.

8. Density tests shall be performed for both pipe embedment zone and the final backfill zone. The final backfill zone shall be from 1 ft above the pipe to the finish grade.

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9. Meet following conditions when flowable fill is used instead of Trench Backfill material when specified herein for Type I areas under existing paved areas and for circular precast or cast-in-place concrete manholes.

a. Prevent floatation during placement of flowable fill.

b. Install 12 inches minimum of Trench Backfill material around valves, valve boxes, and fire hydrants.

c. Place flowable fill at maximum of 10-foot lifts.

1) Cure flowable fill at least 4 hours before placing additional lift of flowable fill.

2) Cure final lift at least 24 hours before placing additional compacted Trench Backfill material or paving.

d. For circular precast or cast-in-place concrete manholes, when specified herein, place flowable fill equally around entire manhole from 1 foot above uppermost pipe entering manhole.

1) Backfill trench with flowable fill from top of Pipe Embedment Zone to below pavement base course.

2) Outside Type I areas backfill minimum 12 inches Trench Backfill material above flowable fill.

B. Placing Trench Backfill for Pipes.

1. Do not backfill around pipe, connections, or fittings until Engineer completes measurements and locations.

2. In new subdivision work where water and sewer service connections are to be placed in same trench at different times, backfill and compact above sewer service connection as specified up to proposed finished grade.

a. When installing water service connection, re-excavate as required, install water pipe, backfill, and compact as specified.

3. Detectable Warning Tape

a. Use blue detectable warning tape for water mainline and water service connections.

b. When water and sewer are installed in same trench use only blue detectable tape.

c. Use green detectable warning tape for gravity sewer mainline, gravity sewer service connections, and pressure sewer piping for both grinder pump systems and force mains.

1) Detectable warning tape will not be required when both manholes in gravity sewer mainline reach are within limits of existing or proposed paved areas.

2) Use yellow detectable warning tape for externally coated ductile iron pipelines and test station lead wires.

3) Place tape directly over centerline of pipe the full length of trench, 18 to 30 inches below finished surface and with minimal number of splices.

4) Overlap tape minimum 6 inches at splices and intersections.

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4. On steep slopes, place trench erosion checks following Standard Details, at locations shown on Drawings or at Engineer’s direction.

5. When pipelines cross under existing utilities, use flowable fill.

6. When connecting to existing pipelines, backfill under and around excavated and undermined existing pipes with Trench Backfill compacted as structural fill:

a. Backfill existing Rigid Pipe to pipe spring line with Borrow Aggregate ASTM

C33, coarse aggregate size number 67, or same Borrow Aggregate as used at connecting or adjacent pipe.

b. Backfill existing Flexible Pipe to 1 foot above top of pipe.

1) DIP 24 inch and smaller and Type K Copper Pipe: Trench Backfill.

2) DIP larger than 24 inches: Borrow Aggregate.

a) Bank run gravel

b) Or graded aggregate base

3) PVC Gravity Sewer Pipe:

a) Borrow aggregate, ASTM C33.

b) Coarse aggregate, size number 67 or size number 8.

4) PVC AWWA C900/905 PVC Pipe.

a) Pipe with 10 feet or less cover:

(1) Trench Backfill containing no rock or gravel larger than 3/4 inch.

(2) Or Borrow Aggregate meeting ASTM C33, coarse aggregate size number 67 for Bedding Zone.

b) Pipe with greater than 10 feet cover:

(1) Borrow Aggregate meeting ASTM C33, coarse aggregate size number 67 for Bedding Zone.

7. Place and compact specified Trench Backfill in following Zones to width and depth following Standard Details and Drawings, unless otherwise specified.

a. Additional excavation area below Pipe Embedment Zone: Place as Trench

Backfill and compact as Structural Fill.

b. Bedding zone: Standard details M/8.0, M/8.1b, M/8.1C

1) Place bedding material in the bottom of the trench in loosely placed uncompacted lifts no greater than 6 inches and compacted to density of no less than 95% per ASTM D698 by the 3rd party testing firm.

2) Shape the bedding material to evenly support pipe at the proper line and grade, with full contact at the bottom of the pipe.

c. Pipe Embedment Zone (haunch and initial backfill zones): Place and compact Trench Backfill as Structural Fill.

1) DIP, 24 inch and smaller and PVC AWWA C900/905: If additional excavation below trench bottom is required to remove unsuitable material, install minimum 6 inches of compacted Trench Backfill between pipe and additional excavation material.

2) PVC Pipe: Compact using manual tampers.

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3) All sizes of DIP with external coating system or polyethylene encasement:

Place Trench Backfill around pipe without damaging pipe coating and polyethylene encasement.

a) Do not drop Trench Backfill directly on pipe; use deflecting boards or other temporary protection.

b) Do not permit workers to walk on or place tools on pipe.

c) Sewer pipe connections to manholes or structures: Bentonite when required, following Section 02530, Standard Details or Drawings.

d) Pipe Embedment Zone within Wetland Areas: Extend from trench bottom to 6 inches above pipe, full width of trench.

e) Pipe to have concrete encasement: Place around pipe within Pipe

Embedment Zone, to limits shown on Standard Details.

d. Final Backfill Zone: Place Trench Backfill and compact following these designation types. Trench Backfill not meeting requirements herein: Re-compact at no cost to Commission.

1) Service Connection Contracts (AC, LC, and SC) in Type 1 areas under existing paving:

a) State and county arterial roads and shoulders.

(1) Place crushed stone in horizontal layers not to exceed 6 inches in depth.

(2) Uniformly tamp each layer and compact by means of mechanical or vibratory compacting device.

b) Other roads: Same as for “All other Contracts” specified below.

Or,

2) All other Contracts in Type I areas under existing paving:

a) Compact to not less than following percents of maximum dry densities at moisture content within 2 percent of optimum for material, as determined by listed ASTM method.

(1) MSHA highways: 92 percent except for top foot below pavement subgrade, and 97 percent for top 1-foot following ASTM D1557 for the Modified Proctor.

(2) All other paved areas: 95 percent except for top foot, which will be 100 percent following ASTM D698.

3) In Type I areas under future paved areas and within public rights of way:

Compact to not less than 95 percent of maximum dry density following ASTM D698 at moisture content within range where density can be obtained based on moisture density curves taken on existing soil.

4) In Type II: Compact in layers to form thoroughly dense refill free of voids and to preclude settlement within limits specified herein.

5) In Type III areas: Place in 12-inch maximum lifts and compact to not less than 90 percent of maximum dry density, following ASTM D698, at moisture content within range where density can be obtained.

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6) In Type III areas: For trenches under 48 square feet in unpaved areas if excavated materials are used as backfill material, the backfill shall be compacted and visually inspected. For trenches over 48 square feet, excavated materials shall be determined by the 3rd party geotechnical engineer for suitability as trench back fill material. The trench shall be backfilled and tested by the 3rd party geotechnical firm.

7) In Type IV areas: Place in 12-inch lifts.

C. Placing Trench Backfill for Structures.

1. Place and compact specified backfill material to width and depth following

Standard Details, Drawings, and specified herein.

a. Additional excavation area, below Granular Bedding: Place and compact

Trench Backfill as Structural Fill.

b. Granular Bedding, under structure: Place and compact specified herein.

c. Place and compact Trench Backfill as Structural Fill to top of structure or to finished grade, following Drawings or Standard Details.

D. Finished Grade.

1. Grade areas disturbed during Work to existing grade before disturbance, unless otherwise noted on Drawings, Standard Details, or with Engineer’s approval.

2. Slope surface to drain, to provide positive drainage in Type I, II, and III areas.

3.3 RESTORATION

A. Restore and restabilize surface features and facilities damaged or destroyed during construction at least to condition existing before construction, following Section 01770, and other applicable Specification Sections.

PART 4 MEASUREMENT AND PAYMENT

4.1 EXCAVATION AND BACKFILL FOR TRENCHES AND STRUCTURES

A. Excavation listed will not be measured separately for payment, but cost will be included in unit prices bid for particular item.

1. Pipelines and structures and backfill with approved Trench Backfill material excavated from trench, including required Pipe Embedment Zone material for pipes and Granular Bedding for structures.

2. Original existing pavement excavation and disposal, 30-inch cap, and temporary pavement.

B. No payment will be made for excavation and backfill for pipelines and structures in excess of limits described herein.

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4.2 BORROW MATERIAL ABOVE PIPE EMBEDMENT ZONE

A. Measurement: By compacted volume in cubic yards actually placed for type required when listed in Bid Schedule.

1. Borrow Material will be computed using depth to top of pipe of embedment zone and width as shown on Standard Details and Drawings and specified herein.

2. No allowance will be made for any material deposited beyond these limits.

B. Payment: At unit price for each cubic yard listed in Bid Schedule.

1. When required in Special Provisions, and no item is listed in Bid Schedule, no measurement for payment will be made and cost thereof will be considered incidental.

2. When required under Engineer’s direction, at fixed contingent price listed in Bid Schedule.

3. Payment includes disposal off-site of unsuitable material.

4.3 PIPE EMBEDMENT ZONE FOR PIPES

A. Pipe Embedment Zone material for pipes will not be measured for payment, but cost shall be included in unit price for each linear foot in Bid Schedule.

4.4 GRANULAR BEDDING FOR STRUCTURES

A. Granular Bedding for structures will not be measured for payment, but cost shall be included in Bid Schedule lump sum item for structures.

4.5 ADDITIONAL EXCAVATION

A. Measurement: Excavation of unsuitable material and replacement with Borrow Material below Pipe Embedment Zone or below Granular bedding or structures, at Engineer’s direction, measured by cubic yard actually replaced.

B. Payment: At fixed contingent unit price for each cubic yard listed in Bid Schedule.

1. Payment includes excavation and disposal off-site of unsuitable material, and provision of Borrow Material.

4.6 TEST PITS

A. Measurement: Test pits in numbers, at locations, and to limits directed by Engineer measured by cubic yard of excavated material removed.

1. Those portions of test pits not backfilled but utilized as trench excavation, and test pits required by Contract Documents, are not measured for payment as test pits, but their cost are included in unit prices bid.

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B. Payment: At fixed contingent unit prices for each cubic yard listed in Bid Schedule.

1. Payment includes labor, equipment, and material required to excavate, maintain, and backfill test pits following requirements specified herein.

**WSSC **