5. Revised Construction Spec 421 - ECD for Marsh Creation - Amend 3 - Jan 2023.pdf

NRCS – July 2022 Amend #3 – Jan. 2023 LA- LaBranche MC PO-75 421-1

Construction Specification 421 — Earthen Containment Dike for Marsh Creation

1. Scope The work consists of the construction of earthen containment dikes (ECDs) for marsh creation required by the drawings and specifications and disposal of any unsuitable excavated materials.

2. Material All fill material shall be obtained from required excavations and designated earthen containment dike borrow areas (ECDBA) shown on the drawings or as specified in section 10.

The presence of rock, buried shell, exposed shell, or other material are possible, and cannot be excluded with any degree of certainty.

3. Excavation Excavation shall be from the ECDBA locations and dimensions indicated in the contract drawings, as specified in section 10, or as approved by the Contracting Officer’s Representative (COR). Excavations shall be completed and maintained in a safe and stable condition through the total construction phase.

4. Use of excavated material All suitable material from the ECD Borrow Area shall be used in the construction of the ECDs.

5. Disposal of waste materials Woody debris shall not be within the footprint of the ECD and may be disposed of in the marsh creation areas, unless otherwise specified in section 10 of this Specification. Any other unsuitable excavated materials are designated as waste and are to be disposed of in an environmentally acceptable manner that does not violate local rules and regulations. The method and location of disposal shall be approved by the COR.

6. Placement Due to limitations on equipment reach, the exterior slope of the ECD(s) are not required to be dressed. The final top width and interior slope shall be shaped such that it does not pond water deeper than 0.1 ft at any location, or as otherwise specified in section 10.

ECDs may need to be constructed in multiple lifts in order to reach the design template, unless otherwise specified in section 10 of this Specification.

7. Removal and Replacement of Defective Earthfill Earthfill not conforming to the requirements of the specifications shall be reworked to meet the requirements or removed and replaced with acceptable earthfill. The replacement earthfill shall conform to all requirements of this specification. Defective earthfill may be placed in the marsh creation area.

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8. Maintenance ECDs shall be maintained to the minimum required height shown in the plans or as specified in Section 10, in order to contain the marsh creation fill for the duration of the marsh creation fill operations within the corresponding marsh creation area.

9. Measurement and payment Measurement shall be as specified in Construction Specification 7 – Construction Surveys.

Payment shall be as specified in section 10.

10. Items of work and construction details

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10. Items of work and construction details Items of work and construction details to be performed in conformance with this specification and the construction details therefore are:

A. Bid Item 6 - Earthen Containment Dike

1) General

i. This item shall consist of all excavation for the construction of earthen containment dikes (ECDs) to meet the lines and grades specified in the construction drawings. Minor adjustments may be made in the field by the COR.

ii. The Contractor shall use professional judgement in determining the means and methods for ECD construction.

iii. The Contractor shall include the following in the Work Plan: explain the method of excavation, type of equipment to be used, equipment reach capability, and construction sequence and schedule.

iv. For MCA 3, at Station 12+50 to Station 16+00, the Contractor will be allowed to work on the outside for dressing and shaping the ECD to meet the lines and grades specified in the construction drawings.

v. The Contractor will be allowed to perform excavation for ECDs within the work limits as shown on the drawings from sunrise to sunset, 7 days per week.

vi. Reference the Special Provisions of the project specifications for requirements when working near or over pipelines and other utilities.

vii. The complete Geotechnical Investigation and Analysis Reports are available to the Contractor upon request to the COR.

viii. Section 7 - Removal and replacement of defective earthfill does not apply.

2) Surveys

i. See Construction Specification 7 – Construction Surveys for all surveys applicable to this item of work.

3) Berm

i. The Contractor shall maintain a 35 ft wide (minimum) berm between the ECD toe and top of Earthen Containment Dike Borrow Area (ECDBA) at all times, with no equipment within 15 ft of the ECD toe.

4) Earthen Containment Dike Borrow Area (ECDBA)

i. Material excavated for the purpose of constructing ECDs shall be from the

ECDBA depicted in the construction drawings.

ii. Maximum excavation depth for dike construction is -15.0 ft NAVD 88, with 2:1

(H:V) side slopes.

5) Lift

i. The geotechnical analysis, completed by GeoEngineers, recommends the containment dikes be constructed in two lifts at a minimum.

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ii. The location where geotextile fabric is placed within the containment dike shall built up to an elevation of +1.0.

iii. The target elevation for the second lift and/or any subsequent lifts shall be the final design elevations shown on the drawings.

iv. A minimum of 10 days must pass between the completion of the first lift and the start of the second lift for any location on the alignment.

6) Dimensions

i. The ECDs shall be constructed to the lines and grades shown in the project drawings.

ii. Final ECD top width shall be 5’ wide, constructed to +4.0 ft NAVD88, and have

3:1 (H:V) side slopes with the exception of MCA 3 between STA 12+50 and 15+80. That section shall have 4:1 (H:V) side slopes. If multiple lifts are used by the Contractor, no dimension requirements are specified for initial lifts.

7) Maintenance

i. Equipment crossing locations shall be identified in the Work Plan and approved in advance by the COR. The Contractor’s measures to protect the ECD and berm at equipment crossings shall be included. The Contractor is allowed to work 24/7 during dredging activities to maintain ECDs.

ii. ECDs shall be required to maintain at least 1 ft of freeboard above water/slurry surface level during all marsh creation fill operations. If 1 ft of freeboard is not maintained, the COR may require the Contractor to cease marsh creation fill operations until the ECD is compliant with this requirement. All down time due to lack of maintenance will be at the Contractor’s expense.

8) Tolerance and Acceptance

i. A vertical tolerance of -0.5 ft. is allowed for the ECD top elevation.

ii. The ECDs will be accepted based on ECD surveys, showing the ECDs are to lines and grades, have been submitted and approved by the COR.

9) Dewatering Structures

i. Dewatering structures shall be installed prior to commencement of the marsh creation fill operations.

ii. The Contractor shall be responsible for properly designing, sizing, quantifying, locating, and maintaining the dewatering structures needed to adequately convey the effluent runoff created by the hydraulic excavation operations. The Contractor shall implement measures to ensure significant amounts of sediment are not dispersed into the waterways. The Contractor shall specify the size, quantity, and location of the dewatering structures in the Work Plan.

iii. Dewatering locations will be restricted to the areas shown on the drawings.

Variations to these locations must be approved in writing by the COR and CO prior to installation.

iv. Dewatering structures shall be designed such that:

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a. The water surface within the MCAs do not exceed elevation +3.0 ft NAVD 88.

b. At least one foot of freeboard is maintained between the water surface and earthen containment dike crown.

c. There is adequate retention to allow sediments to settle out of suspension.

v. Structures shall be adjustable in height to accommodate the varying fill heights experienced during construction. At a minimum, structures should be capable of being lowered to the mean low water elevation (0.21 ft) expected during the time of construction and up to elevation +3.0 ft.

vi. Dewatering structures shall be inspected each day to ensure proper functioning, which includes maximizing solids retention and limiting the influx of water from outside the containment system. At all times structures shall be always kept free of debris.

10) Dewatering Structure and Removal

i. See Construction Specification 3 – Structure Removal for requirements.

11) Final Measurement and Payment

i. Acceptance and partial payment will be made for segments of ECD constructed at a minimum of 2,500 linear feet, except for the final segment of a given MCA.

ii. Partial payment shall be made at 75% of the bid price upon submission and approval by the COR of ECD progress surveys showing ECDs are to neat lines and grades.

iii. The remaining 25% of the bid price shall be paid at the completion of Bid Item 3, Marsh Creation Fill.

iv. Such payment constitutes full compensation for all labor, material, equipment, and for Subsidiary Items, Clearing, Pollution Control, Dewatering Structure Removal, and Quality Control; and all other items necessary and incidental to the performance of the work.