35 20 23.pdf

Emsworth L/D - Back Channel Left Abutment Stabilization and Scour Protection

SECTION TABLE OF CONTENTS

DIVISION 35 - WATERWAY AND MARINE CONSTRUCTION

SECTION 35 20 23

DREDGING

PART 1 GENERAL

1.1 SUMMARY

1.2 SUBMITTALS

1.3 MATERIAL TO BE REMOVED

1.3.1 General

1.3.2 Existing Derrick Stone

1.3.3 Existing Graded Stone

1.4 UNKNOWN OBSTRUCTIONS

1.5 QUANTITY OF MATERIAL

1.6 OVERDEPTH DREDGING

1.7 SIDE SLOPES

1.8 PERMIT

1.8.1 Testing

1.8.2 Existing Water Intakes

1.9 ENVIRONMENTAL PROTECTION REQUIREMENTS

1.10 SUBSURFACE DATA

1.11 BASIS FOR BIDS

PART 2 PRODUCTS (Not Applicable)

PART 3 EXECUTION

3.1 INSPECTION

3.2 CONDUCT OF DREDGING WORK

3.2.1 Limits of Work

3.2.2 Order of Work

3.2.3 Lights

3.2.4 Ranges, Gages, and Lines

3.2.5 Plant

3.2.6 Removal of Obstructions

3.2.7 Disposal of Excavated Material

3.2.7.1 Method of Disposal

3.2.8 Navigation Warnings

3.2.9 Method of Communication

3.2.10 Salvaged Material

3.2.11 Safety of Structures

3.2.11.1 Potential for Tool Drops

3.2.12 Plant Removal

3.3 FINAL EXAMINATION AND ACCEPTANCE

3.4 INSPECTION REPORTS

3.5 CONTRACTOR QUALITY CONTROL

-- End of Section Table of Contents --

SECTION 35 20 23 Page 1 W911WN-10-B-0006 Revised by Amendment 0002

SECTION 35 20 23

DREDGING

PART 1 GENERAL

1.1 SUMMARY

This work shall consist of the removal of dredged material, derrick stone, graded stone, and any other miscellaneous materials to facilitate barge access and construction of the abutment combination wall, including metal sheet pile, wall termination column, and socketed pipe pile installation, and grout bag scour protection. The existing materials to be removed contain hard material, which is defined as material requiring the use of special equipment for economical removal and includes riprap installed as part of the previous scour protection system.

1.2 SUBMITTALS

Government approval is required for submittals with a "G" designation;

submittals not having a "G" designation are for information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government. The following shall be submitted in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-01 Preconstruction Submittals

Dredging Plan; G|RE

Prior to conducting dredging, submit drawings for areas to be dredged. Drawings should reflect the most recent soundings, the location of existing features to be protected, and the location of constructed features.

Protection Plan; G|RE

Prior to dredging, submit a plan for protection of surrounding structures, equipment, and vessels.

SD-02 Shop Drawings

Soundings or Sweepings; G|RE

Submit drawings of surveys prior to and during progress of work by soundings or sweepings for all areas to be dredged. Furnish the Dredging Plan and include location of stone and dredged material encountered.

SD-11 Closeout Submittals

Inspection Reports

The results of dredging surveys conducted by the Contractor shall be provided to the Contracting Officer for purposes of verifying that the dredged areas meet the requirements of the specifications and the cross-sections shown on the drawings.

SECTION 35 20 23 Page 2

1.3 MATERIAL TO BE REMOVED

1.3.1 General

The material to be dredged includes a variety of riverbed alluvium (consisting of silt, sand, gravel, sediment, and cobbles); former apron protection materials (consisting of derrick stone and graded stone); and other overburden materials of varied character. All material will need to be removed individually and segregated by type and character.

Dredging shall be performed to an allowable tolerance of plus 0 feet and minus 2 feet from the lines and grades shown on the drawings.

1.3.2 Existing Derrick Stone

The existing 5 foot derrick stone stone layer, constructed as part of the 1986 scour protection project, and located downstream of the dam apron, shall be removed and disposed as described in this section, or staged and reused as described in Section 35 31 19 STONE SLOPE AND SCOUR PROTECTION.

Where reused, this material is referred to as "reused derrick stone" on the drawings. Stone used in this layer was specified to be not less than 4.5 feet and not more than 6.0 feet in size. Size was defined as the smallest distance between opposing faces, measured through the approximate center of gravity of an individual stone. Stone was also required to be generally blocky shaped. The existing derrick stone layer is estimated by the Government to be partially displaced from its original position due to high velocity flow events.

1.3.3 Existing Graded Stone

The existing 3 foot graded stone layer, constructed as part of the 1986 scour protection project and located downstream of the dam apron, shall be removed and disposed as described in this section, or staged and reused as described in Section 35 31 19 STONE SLOPE AND SCOUR PROTECTION. Where reused, this material is referred to as to as "reused graded stone layer" on the drawings. The existing 3 foot graded stone layer possesses the following gradation:

REUSED GRADED STONE LAYER

STONE SIZE PERCENT BY WEIGHT SMALLER

(IN.) THAN STONE SIZE

24 95%-100% 12 25%-50% 4 0%-5%

The existing 3 foot graded stone layer is estimated by the Government to be partially displaced from its original position due to high velocity flow events.

The existing graded stone shall be removed, staged, segregated, and reinstalled as follows:

a. Graded stone material smaller than 12 inches shall be placed on the riverward side of the abutment combination wall, or other areas approved by the Contracting Officer, after completion of wall installation.

SECTION 35 20 23 Page 3

b. Graded stone material larger than 12 inches, but smaller than 30 inches, may be placed as riprap backfill on the riverward side of the abutment combination wall, or other areas approved by the Contracting Officer, after completion of wall installation.

c. Graded stone material larger than 30 inches may be placed on the riverward side of the abutment combination wall, or other areas approved by the Contracting Officer, after completion of wall installation.

1.3.6 Hard Material

Remove hard material using specialized procedures appropriate for the material. Blasting will not be permitted. Conduct operations in strict accordance with applicable regulations, detailed plan of underwater removal, protection plan, and as otherwise required to achieve the lines and grades required, subject to the approval of the Contracting Officer.

1.4 UNKNOWN OBSTRUCTIONS

If actual material differs from that described in paragraph "Material to be Removed" above, the Contractor shall stop all dredging work immediately and contact the Contracting Officer. At this point, an investigation will be made and modifications to the Dredging Plan may be required. If necessary, an adjustment in contract price, time for completion, or both will be made in accordance with Contract Clause "DIFFERING SITE CONDITIONS". The use of explosives for removal of unknown obstructions is prohibited. The Contractor may require employment of additional equipment for economical removal of unknown obstructions.

1.5 QUANTITY OF MATERIAL

If known, the total estimated amount of material to be removed from within the specified limits, including side slopes, but excluding overdepths, is shown on the Bid Schedule. This estimated quantity is for bidding purposes and for application of the Contract Clause "VARIATION IN ESTIMATED QUANTITY" includes overdepth, derrick stone, and graded stone. The Contractor shall perform sweepings or soundings of the area, witnessed by the Contracting Officer, before and after dredging operations to determine the total quantity of material dredged.

Two of the materials to be removed adjacent to the abutment wall, derrick stone and graded stone, shall be staged by the Contractor. Reinstallation of these materials shall be as specified herein and as described in Section

35 31 19 STONE SLOPE AND SCOUR PROTECTION.

The quantities listed in the Bid Schedule are estimates only. The Contractor shall complete the work specified, whether the quantities involved are greater or less than those estimated.

1.6 OVERDEPTH DREDGING

To cover unavoidable inaccuracies of material removal processes, material actually removed to a depth of 1-foot below the depth specified for dredging and 2-feet below the depth specified for hard material, and within the stipulated limits, will be measured and paid for at full contract price.

SECTION 35 20 23 Page 4

1.7 SIDE SLOPES

Dredging on side slopes shall follow, as closely as practicable, the lines indicated or specified. An allowance will be made for dredging beyond the lines indicated or specified for side slopes. The allowance will be determined by projecting a line upwards, paralleling the project design side slopes, from the intersection of the overdepth dredging limit (at a point located vertically below the limit of dredging at the top of slope).

The amount of material excavated from side slopes will be determined by either cross-sections, computer, or both using soundings, sweepings, and templates.

1.8 PERMIT

The Contractor shall comply with conditions and requirements of the Corps of Engineers Permits and other State or Federal permits. The Contracting Officer will secure the permit for dredging and disposal of material as indicated. Excavated materials shall be disposed of at a properly permitted, commercially available facility, or at the option of the Contractor, to the Phillis Island and Georgetown Island disposal sites as shown on the drawings. The specification for island disposal (if required) is located in Section 35 31 19.15 GEORGETOWN AND PHILLIS ISLAND BANK PROTECTION AND DREDGE MATERIALS DISPOSAL. Any disposal materials that cannot be accommodated by the islands shall be taken to a properly permitted, commercially available disposal site.

1.8.1 Testing

As a condition of the Section 401 water quality certification for disposal at Phillis Island and Georgetown Island, the material shall be tested at a rate of one test per 1,000 cubic yards for Total Petroleum Hydrocarbons (TPH) or Diesel Range Organics (DROs) and Total Arsenic, and a rate of one test per 5,000 cubic yards for reactive sulfide. The TPH or DROs are an indicator parameter. If the test results are over 200 mg/kg, then the material shall also be tested for Polynuclear Aromatic Hydrocarbons (PAHs). If the reactive sulfide results are greater than 100 mg/kg, then the testing frequency shall be increased to one test per 1,000 cubic yards. Concentrations of reactive sulfide at 400 mg/kg or greater is cause for concern. If the material appears contaminated more testing may be warranted. All sampling and testing shall be properly documented, and all analyses performed by a laboratory accredited or registered for accreditation under the Pennsylvania Environmental Laboratory Accreditation Act. Test results shall be submitted to the Contracting Officer prior to placing the material to which the tests pertain.

1.8.2 Existing Water Intakes

There are publicly and privately owned water intakes downstream of the project area which may be affected by dredging operations. The Government will issue a Public Notice concerning the work of this contract; however, the Contractor shall be responsible for notifying the owners of the water intakes in writing in advance of his dredging activities.

1.9 ENVIRONMENTAL PROTECTION REQUIREMENTS

Provide and maintain during the life of the contract, environmental protective measures. Also, provide environmental protective measures required to correct conditions, such as oil spills or debris, that occur during the dredging operations. Comply with Federal, State, and local

SECTION 35 20 23 Page 5 regulations pertaining to water, air, and noise pollution.

1.10 SUBSURFACE DATA

Subsurface soil boring logs are shown on the drawings. The subsurface data represent subsurface information available. However, variations may exist in the subsurface between boring locations. It is essential that the Contractor and all of his specialty subcontractors familiarize themselves with this information and satisfy themselves that they have adequate subsurface information to allow an informed bid of the project requirements or state otherwise in their proposal.

1.11 BASIS FOR BIDS

Base bids on the quantity of dredging indicated. Should the total quantity of dredging vary from that specified as the basis for bidding, the contract price will be adjusted in accordance with Contract Clause "CHANGES". This may include shoaling or redepositing of sediments from high flow events, emergency operations in response to a high flow event, or other occurrences that would subject the dredged area to shoaling and redepositing of sediments for a prolonged period of time. The dredging conditions specified and indicated describe conditions which are known. However, the Contractor is responsible for other conditions encountered which are not unusual when compared to the conditions recognized in the dredging business as usual in dredging activities such as those required under this contract.

PART 2 PRODUCTS (Not Applicable)

PART 3 EXECUTION

3.1 INSPECTION

The Government will keep a record of work performed and will require that gages, ranges, and other markers are usable for the intended purpose. The Contractor shall furnish, at the request of the Contracting Officer, boats, boatmen, laborers, and materials necessary for inspecting, supervising, and surveying the work. When required, the Contractor shall provide transportation for the Contracting Officer and inspectors to and from the disposal area and between the dredging plant and adjacent points on shore.

The Contractor shall be required to furnish such facilities for the surveys prescribed in paragraph "Final Examination And Acceptance".

3.2 CONDUCT OF DREDGING WORK

3.2.1 Limits of Work

The work shall be limited to a maximum length of 250 feet from the existing downstream apron. No limit of excavation depth is specified.

3.2.2 Order of Work

The Contracting Officer will direct the Contractor on the order of work.

The Government reserves the right to change the order of work at any time.

3.2.3 Lights

Each night, between sunset and sunrise and during periods of restricted visibility, provide lights for floating plants, pipelines, ranges, and markers. Also, provide lights for buoys that could endanger or obstruct

SECTION 35 20 23 Page 6 navigation. When night work is in progress, maintain lights from sunset to sunrise for the observation of dredging operations. Lighting shall conform to United States Coast Guard requirements for visibility and color.

3.2.4 Ranges, Gages, and Lines

Furnish, set, and maintain ranges, buoys, and markers needed to define the work and to facilitate inspection. Establish and maintain gages in locations observable from each part of the work so that the depth may be determined. Suspend dredging when the gages or ranges cannot be seen or followed. The Contracting Officer will furnish, upon request by the Contractor, survey lines, points, and elevations necessary for the setting of ranges, gages, and buoys.

3.2.5 Plant

Maintain the plant, coamings, barges, and associated equipment to meet the requirements of the work. Remove dredged material placed due to leaks and breaks.

3.2.6 Removal of Obstructions

It is anticipated that much of the river material in the vicinity of the abutment combination wall driving line consists of derrick stone, riprap, random fill and alluvium, and miscellaneous debris (pieces of steel, concrete rubble, wood, etc.), which accumulated over time and/or was placed during previous rehabilitation efforts. Those materials posing a potential obstruction to the driving, drilling, or proper installation (e.g., to meet necessary tolerances) of the abutment combination wall components shall be incrementally removed and be concurrently replaced to the planned subgrade level of the combination wall cap/slab. The replacement fill shall consist of obstruction-free, remnant excavated granular material and/or imported aggregate base course material.

Incrementally pre-excavate to remove obstructions to elevation 688.0 (or deeper if necessary and approved by the Contracting Officer) along the abutment combination wall alignment and concurrently backfill to restore grades to the planned subgrade level of the combination wall cap/slab. The pre-excavation and obstruction removal may progress down to elevation 688.0 (base of existing abutment wall) before the following restrictions on deeper excavation shall apply. Pre-excavation below elevation 688.0 shall commence at the apron and progress incrementally with concurrent backfilling in a downstream direction, unless alternative procedures are proposed in writing by the Contractor and are approved by the Contracting Officer. The pre-excavation shall target a localized area and be limited to a maximum excavation width of 15 feet measured perpendicular to the dam (parallel to river flow), after which the excavation shall be immediately backfilled with obstruction-free material to at least elevation 688.0 before progressing with pre-excavation, obstruction removal, and backfilling in the next adjacent area. The pre-excavations shall not extend lower than elevation 683.0.

If and when a deeper obstruction (extending below elevation 683.0) hinders the drilling or driving of any casing, piles, or sheet piling to the specified penetration, the obstruction shall be penetrated with a chisel beam or other approved tool. Under no circumstances shall the Contractor attempt to penetrate an obstruction with abutment combination wall elements. The obstructed combination wall element(s) shall be removed if necessary to permit chiseling of the obstruction. The Contractor shall

SECTION 35 20 23 Page 7 have such appropriate equipment present at the site that is necessary to extract or penetrate any obstruction encountered. If an obstruction is encountered during the driving operation, driving of the casing shall be stopped and the Contracting Officer shall be notified promptly. No attempt shall be made to penetrate any obstruction until the Contracting Officer has been informed and has given approval to proceed. If the Contractor attempts to penetrate the obstruction, the Contracting Officer shall verify that the chisel beam is adequately founded on the obstruction prior to attempting to penetrate the obstruction. The obstruction shall be chiseled sufficiently so that the obstructed element may be installed without damage. If the Contractor demonstrates that penetration of the obstruction is impractical, the Contractor shall either discontinue the driving of the particular element or make changes in the design alignment of the element, as directed by the Contracting Officer. Any change in design alignment shall insure the adequacy, continuity, and stability of the structure.

3.2.7 Disposal of Excavated Material

The Contractor shall safely transport and dispose of dredged materials at the locations designated in this contract, unless select materials are to be reused within the Contractors Work Limits, in accordance with Section 35 31 19 STONE SLOPE AND SCOUR PROTECTION. The deposition of dredged materials in unauthorized places is forbidden. Comply with rules and regulations of local port and harbor governing authorities. Dredged material shall be removed and transported to a properly permitted, commercially available facility provided by the Contractor, or at the option of the Contractor, to the Phillis Island and Georgetown Island disposal sites indicated on the drawings. The Phillis Island and Georgetown Island disposal sites are located at river mile markers 35.0 and

37.7 respectively. This is approximately 30 miles downstream of the Emsworth Locks and Dams in the New Cumberland Pool of the Ohio River. Any disposal materials that cannot be accommodated by the islands, including material that does not pass the testing specified in paragraph "Testing", shall be taken to a properly permitted, commercially available disposal site. If the Contractor chooses to dispose of dredged materials at the islands, the Contractor shall perform bathymetry before and after placement of all materials specified herein and as directed by the Contracting Officer.

3.2.7.1 Method of Disposal

Deposit dredged material by barge. The Contractor shall be responsible for monitoring the location of his barges used for transporting dredge material. He shall submit a plan that shall include, at a minimum, the barge name, the number of trips proposed, the number of barges in the tow, the size of the tug transporting the tow, an approximate date and time of arrival and departure from the Emsworth Locks and Dams and from the tow's final destination (to be determined by the Contractor during bid preparation) and the proposed route, including navigation through Ohio River locks. The Contractor shall notify the Contracting Officer when barges are returned to the dredge area.

3.2.8 Navigation Warnings

Furnish and maintain navigation warning signs as required by the Contracting Officer.

SECTION 35 20 23 Page 8

3.2.9 Method of Communication

Provide a system of communication between the dredge crew and the crew at the disposal area. A portable two-way radio is acceptable.

3.2.10 Salvaged Material

Anchors, chains, firearms, and other articles of value, which are brought to the surface during dredging operations, shall remain or become the property of the Government and shall be deposited on shore at a convenient location near the site of the work, as directed.

3.2.11 Safety of Structures

The prosecution of work shall ensure the stability of piers, abutment wall, bulkheads, and other structures lying on or adjacent to the site of the work, insofar as structures may be jeopardized by dredging operations. The Contractor shall repair damage resulting from dredging operations, insofar as such damage may be caused by variation in locations, depth of dredging, or both from that indicated or permitted under the contract.

3.2.11.1 Potential for Tool Drops

The Contractor shall provide divers to inspect the riverbed for potential areas in which a tool drop, a void formed in the alluvium by bridging structures, such as derrick stone, physical obstructions, etc., may be present. After dredging operations and before reinstallation of derrick stone and graded stone, divers will inspect and review the proposed subgrade to visually identify potential nonstructural areas. Should the divers determine the potential for a tool drop, the Contractor shall excavate to the nonstructural area and backfill the tool drop with aggregate base course material specified in Section 32 11 23 AGGREGATE BASE COURSE as directed by the Contracting Officer.

3.2.12 Plant Removal

Upon completion of the work, promptly remove plant, including ranges, buoys, piles, and other markers or obstructions.

3.3 FINAL EXAMINATION AND ACCEPTANCE

Immediately before commencing any other work requiring dredging operations to be completed, the dredged areas shall be thoroughly examined by the Contractor, under the direction of the Contracting Officer, by sounding, sweeping, or both. The Contracting Officer shall be notified by the Contractor when soundings or sweepings are to be made and the Contracting Officer will be permitted to accompany the sounding or sweeping party and to inspect the data and methods used in preparing the final estimate. When areas are found to be in a satisfactory condition, the work therein will be accepted as complete.

If shoaling or redepositing of sediments from river flows or other means occurs in any section previously accepted, such material shall be removed by the Contractor before commencing any work dependent on completion of dredging operations.

The Contractor shall furnish the results of all dredging surveys to the Contracting Officer in accordance with paragraph "Inspection Reports". If any points identified on the survey sections do not meet the specified

SECTION 35 20 23 Page 9 contract template, the Contractor shall be required to remove additional material, and the area shall be resurveyed. All survey information shall be submitted to, and the areas accepted by, the Contracting Officer before commencing any other construction operations in the area which are dependent on the completion of the dredging operations. Final estimates will be subject to deductions or correction of deductions previously made because of excessive overdepth, dredging outside of authorized areas, or disposal of material in an unauthorized manner.

3.4 INSPECTION REPORTS

The results of all surveys for dredging, conducted by the Contractor, shall be delivered to the Contracting Officer. These requirements do not relieve the Contractor of the obligation to report failures immediately. Such reports of failures and the action taken shall be confirmed in writing.

The Contractor shall perform surveys (soundings or sweepings) of the dredging operations and shall report the general progress of all dredging operations to the Contracting Officer no later than 24 hours following the completion of the survey.

3.5 CONTRACTOR QUALITY CONTROL

The Contractor shall establish and maintain a quality control system for all dredging operations. The Contractor's quality control is that system by which a Contractor regulates, tests, inspects his procedures, equipment, and personnel so that his operations will comply with the requirements specified herein. The Contractor shall perform all surveys and report all findings and any problems to the Contracting Officer.

-- End of Section --

SECTION 35 20 23 Page 10

3.2.12 Plant Removal