01 57 24 TEMPORARY TURBIDITY CONTROLS.pdf

FY21 Duluth-Superior Maintenance Dredging FY21MDDULSUPHARB

CERTIFIED FINAL - READY TO ADVERTISE

SECTION TABLE OF CONTENTS

DIVISION 01 - GENERAL REQUIREMENTS

SECTION 01 57 24

TEMPORARY TURBIDITY CONTROLS

04/08

PART 1 GENERAL

1.1 SUMMARY

1.2 SUBMITTALS

1.3 TURBIDITY CONTROL PLAN

PART 2 PRODUCTS

PART 3 EXECUTION

3.1 BEST MANAGEMENT PRACTICES FOR MINNESOTA POINT PLACEMENT AREA

3.1.1 Best Management Practices for Hydraulic Placement

3.1.1.1 Daily Visual Inspection

3.1.1.2 Minimize Pumping Time

3.1.1.3 Pipeline, Scow, and Barge Seals

3.1.1.4 Apron/Spill Controls

3.1.1.5 Material Transfer Station

3.1.1.6 Production Rate BMP

3.1.1.7 Onshore Placement BMP

3.1.1.8 Construction Slope BMP

3.1.1.9 Hydraulic Discharge Configuration BMP

3.1.1.10 Placement Configuration Restrictions

3.1.2 Best Management Practices for Mechanical Placement

3.1.2.1 Mechanical Placement

3.1.2.2 Daily Visual Inspection

3.1.2.3 Pipeline, Scow, and Barge Seals

3.2 BEST MANAGEMENT PRACTICES FOR REQUIRED AND OPTIONAL CLEAN-UP

3.2.1 Debris Removal Methods

3.2.2 Daily Visual Inspection

3.2.3 Minimize In-water Work

3.2.4 Onshore Placement BMP

3.2.5 Bottom Placement BMP

3.3 FIELD QUALITY CONTROL

3.4 INSPECTIONS

3.4.1 General

3.4.2 Inspections Details

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SECTION 01 57 24

TEMPORARY TURBIDITY CONTROLS

04/08

PART 1 GENERAL

1.1 SUMMARY

The work consists of implementing best management practices to prevent excessive suspended solids within the water body as specified in this section and in conformance witht he requirements of Section 01 57 19

TEMPORARY ENVIRONMENTAL CONTROLS.

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. Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES:

SD-01 Preconstruction Submittals

Turbidity Control Plan

Submit in writing the Contractor's Turbidity Control Plan within the (10) calendar days after Notice to Proceed. See paragraph titled "TURBIDITY CONTROL PLAN".

SD-02 Shop Drawings

Placement Configuration Design

Submit drawings of proposed placement configurations. Drawings shall include at a minimum: size, gauge, and material type of piping and baffle plate dimensions and material type. See paragraph titled "Placement Configuration Restrictions".

Material Transfer Station Design

Submit drawings of proposed transfer station and configuration.

Drawings shall include at a minimum: location of transfer site, dimensions and material type of transfer apparatus, and proposed apron/guard for spill control. It shall be the responsibility of the contractor to develop the design of the material transfer station, including maintenance, to handle the wide variety of materials and debris indicated in Section 35 20 23.

1.3 TURBIDITY CONTROL PLAN

The Contractor shall submit a Turbidity Control Plan for the review and acceptance by the Contracting Officer. Placement activities shall not begin unless an approved Turbidity Control Plan is in place. Acceptance is conditional and is predicated upon satisfactory performance during construction. The Government reserves the right to require the Contractor to make changes in the Turbidity Control Plan or operations if the

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Contracting Officer determines that turbidity control requirements are not being met.

The plan shall detail the actions which the Contractor shall take to comply with the specific requirements of this contract. The plan, at a minimun, shall include the following:

a. Description of how the Best Management Practices specified within this specification section will be employed by the Contractor.

b. Description of Contractor's internal checks to ensure Best Managment Practices are properly employed and meeting turbidity control requirements.

c. Description of Contractor's proposed corrective actions if Best Management Practices not properly employed or meeting turbidity control requirements.

PART 2 PRODUCTS

PART 3 EXECUTION

3.1 BEST MANAGEMENT PRACTICES FOR MINNESOTA POINT PLACEMENT AREA

The controls and measures required of the Contractor for placement anywhere on Minnesota Point are described below.

3.1.1 Best Management Practices for Hydraulic Placement

3.1.1.1 Daily Visual Inspection

The Contractor shall visually monitor and observe turbidity levels. The Contractor shall make any repairs as needed to ensure the BMP's are correctly deployed and functioning. If elevated turbidity levels are observed beyond the Construction Zone as indicated on the plans, the Contractor shall immediately notify the COR and cease operations until the turbidity resides.

3.1.1.2 Minimize Pumping Time

The Contractor shall only operate the pump transporting dredged material from the offload site to the placement site when actively placing material.

During idle times when the contractor is waiting for dredge material to arrive at the offload site, the pump will not be left running at full capacity.

3.1.1.3 Pipeline, Scow, and Barge Seals

All nautical vessels, pipelines and land based transport and conveyance systems shall be operated, loaded and unloaded in such manner as to prevent overflow, spills, leaks, waste, or other loss of dredged materials between point of pick-up and point of deposition within the disposal area. Hauling vessels shall have sufficient sidewall height and integrity to prevent drainage over or through the sides and bottom during hauling.

All scows and hoppers used for transporting the dredged material shall be kept in good condition with coamings in repair. Doors of dump vessels shall be maintained in good repair and sealed in a proper manner to prevent the loss of dredged material. Decks of vessels shall be cleaned of dredged

SECTION 01 57 24 Page 3 material before leaving the dredging area. Pipelines in hydraulic dredging systems shall be kept in good condition, free of leaks.

3.1.1.4 Apron/Spill Controls

The Contractor will use an apron/guard to prevent material spillage into the water while being transferred from the scow to the pump.

3.1.1.5 Material Transfer Station

If the Contractor elects to use a material transfer station for placement operations, It shall be the responsibility of the contractor to develop the design of the material transfer station, including maintenance, to handle the wide variety of materials and debris indicated in Section 35 20 23.

The material transfer station shall include, at the minimum, the following best management practices:

a. Apron/Spill Guards

b. The transfer station shall be fully enclosed. The enclosure shall remain inplace during placement operations and during material transfer. The enclosure shall prevent dredge material leakage.

3.1.1.6 Production Rate BMP

The production rate shall not surpass 2,500 cubic yards in a day. The minimum duration this material can be placed in is 12 hours.

3.1.1.7 Onshore Placement BMP

Dredged material shall not be discharged directly into the water. If water levels at the time of construction surpass the allowable placement limits, hydraulic placement into the water along the most landward limit of the placement area will be temporarily allowed until material builds out of the water to place the remainder of the material on the newly constructed exposed fill.

3.1.1.8 Construction Slope BMP

The slope of material below the existing water level shall not be less than the natural angle of repose that is formed from material entering the water, either by equipment or overland discharge.

3.1.1.9 Hydraulic Discharge Configuration BMP

The following hydraulic discharge configuration is approved for use along Minnesota Point and shall be employed by the contractor. A detail of the following discharge configurations is provide on drawing sheet CN501.

A. Configuration #2: Horizontal Discharge Pipe with Baffle Plate.

The baffle plate must be either perpendicular to the pipeline or angled in such a manner that directs material in an upward direction. The angle of the baffle plate shall not surpass 45 degrees from vertical.

3.1.1.10 Placement Configuration Restrictions

In order to the meet the 401 Water Quality certification, all discharge configurations are limited to a single 16" diameter discharge line and 16"

SECTION 01 57 24 Page 4 pump (as defined by the outlet diameter specified by manufacturer of the pump) or smaller. A discharge line and/or pump larger than 16" diameter is prohibitied. Discharge configurations shall consist of a single discharge point fed by a single pipe of 16" diameter or less from the pump outlet to the point of discharge. Splitting, wying, or otherwise seperating the flow at any point along the length of the discharge pipe is prohibited.

3.1.2 Best Management Practices for Mechanical Placement

3.1.2.1 Mechanical Placement

Dredged material, being placed mechanically with a clamshell bucket, shall not be released from the bucket until the bucket is lowered to the bottom of the lake.

3.1.2.2 Daily Visual Inspection

The Contractor shall visually monitor and observe turbidity levels. The Contractor shall make any repairs as needed to ensure the BMP's are correctly deployed and functioning. If elevated turbidity levels are observed beyond the Construction Zone as indicated on the plans, the Contractor shall immediately notify the COR and cease operations until the turbidity resides.

3.1.2.3 Pipeline, Scow, and Barge Seals

All nautical vessels, pipelines and land based transport and conveyance systems shall be operated, loaded and unloaded in such manner as to prevent overflow, spills, leaks, waste, or other loss of dredged materials between point of pick-up and point of deposition within the disposal area. Hauling vessels shall have sufficient sidewall height and integrity to prevent drainage over or through the sides and bottom during hauling.

All scows and hoppers used for transporting the dredged material shall be kept in good condition with coamings in repair. Doors of dump vessels shall be maintained in good repair and sealed in a proper manner to prevent the loss of dredged material. Decks of vessels shall be cleaned of dredged material before leaving the dredging area. Pipelines in hydraulic dredging systems shall be kept in good condition, free of leaks.

3.2 BEST MANAGEMENT PRACTICES FOR REQUIRED AND OPTIONAL CLEAN-UP

For required full depth clean-up and (if awarded) optional surface clean-up, the controls and measures required of the Contractor are described below.

3.2.1 Debris Removal Methods

To the greatest extent practicable, the Contractor shall minimize turbidity impacts to the water column by employing the least degrading prudent and feasible method(s) available for below surface water debris removal activities.

3.2.2 Daily Visual Inspection

The Contractor shall visually monitor and observe turbidity levels. The Contractor shall make any repairs as needed to ensure the BMP's are correctly deployed and functioning. If elevated turbidity levels are observed beyond the Construction Zone as indicated on the plans, the

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Contractor shall immediately notify the COR and cease operations until the turbidity resides.

3.2.3 Minimize In-water Work

When practicable, the Contractor shall conduct clean-up operations landward of the Ordinary High Water Mark (OHWM) 603.1 ft International Great Lakes Datum 1985 (IGLD85) to limit uncontrolled material spillage into the water.

The Contractor shall not stockpile, process, or transfer sediment in the water column for the purpose of filtering out or removing debris. All sediment below the water's surface that must be processed to remove debris must first be placed landward of the water's edge for this purpose.

3.2.4 Onshore Placement BMP

If hydraulic methods are employed, material shall not be discharged directly into the water. Material shall be placed landward of the OHWM

603.1 ft IGLD85 at the time of debris removal and reconstruction of the site and then graded into the water.

3.2.5 Bottom Placement BMP

If mechanical equipment is used to release clean material back into the lake, any such equipment utilizing a bucket must be lowered to the lake bed prior to releasing cleaned material.

3.3 FIELD QUALITY CONTROL

Maintain the discharge configuration, transfer station, and other protective measures in good and effective operating condition by performing routine inspections to determine condition and effectiveness.

3.4 INSPECTIONS

3.4.1 General

Conduct visual inspections twice per day during placement operations to asertain the effectiveness Best Management Practices.

3.4.2 Inspections Details

Inspections shall note the time, date, weather conditions, wave conditions, status of placement operations observed around the placement equipment.

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