657 Wetland Restoration design_install_guide.pdf

USDA-NRCS - North Dakota FOTG - Section IV - Conservation Practices

DESIGN, INSTALLATION, CHECK OUT AND DOCUMENTATION GUIDE

Wetland Restoration - 657

Wetland Restoration shall be planned and installed in accordance with the NRCS standard, as detailed in Section IV – Conservation Practices subfolder of the North Dakota Field Office Technical Guide (FOTG). This document provides additional parameters, recommendations, references, and requirements for developing site-specific plans for this practice.

HYDROLOGY RESTORATION

Surface and subsurface drains not directly connected to a wetland may impact it, i.e., cause a lateral effect. Such situations are most likely to occur in sandy areas with a high water table.

To determine lateral effects, use county-specific data found in ND-FOTG Section II – Drainage Tile Lateral Effects – specific county spreadsheet and/or NRCS Engineering Handbook Chapter 19 - Hydrology Tools for Wetland Determination - Part 650.1905 Scope & Effect Equations.

Surface Hydrology Restoration

Hydrology shall be restored to the conditions that existed before alteration. Dynamic and static water levels and soil saturation shall be restored. Needed level of restoration will be determined by hydric soils investigation, and by investigation of outlet capacity and elevation. When full restoration is prohibited due to site limitations such as ponding water on neighboring property, road impacts, etc., restoration will be targeted to the maximum extent possible.

Surface drain or diversion features that serve as an outlet for upstream lands must comply with applicable State and local laws and regulations pertaining to flooding and surface and subsurface drainage.

Where surface drains were constructed to drain the wetland, the channel will be filled with earth or controlled with a water control structure to restore the wetland hydrologic conditions.

When it is desirable to control or manipulate the water level for operation and maintenance of the wetland at an elevation different than that caused by blocking the surface drain, a water control device meeting the standard 587 - Structure for Water Control in FOTG Section IV – Conservation Practices subfolder will be used.

Material other than sediment shall not be taken from the wetland, except as directed by an NRCS representative.

Fill material used for surface drain blocks/ditch plugs shall have a texture (i.e.,permeability) sufficiently fine to restore original hydrology. Fill shall be free of sod, roots, frozen soil, stones more than six inches in diameter, and other objectionable material.

Design, Installation, Check out and Documentation Guide - 657 October 2006

A. Surface Drain Removal

If the contributing drainage area is less than 20 acres and prolonged surface flows are not anticipated, the entire length of the surface drain may be returned to original topography using compacted earth fill with no overfill requirements for settlement. Fill material must be compacted to a density equal or greater than the adjacent material.

B. Surface Drain Blocks/Ditch Plugs

The surface drain may be blocked with earth fill without a flow control device when flow duration and rate will not cause erosion and head cutting of the block or plug.

The surface drain block or ditch plug will fill a minimum length of surface drain based on the hydraulic conductivity (permeability) of the most limiting layer in the exposed soil profile.

The minimum length of surface drain to be filled is 50 feet for soils with an average hydraulic conductivity of less than 0.6 inches per hour, 100 feet for 0.6 to 2.0 inches per hour, and 150 feet for greater than 2.0 inches per hour.

Plan and install ditch plugs in accordance with the third tab or worksheet titled “Plug Spec” in the ND Wetland Restoration Workbook located in FOTG Section I – Reference Subjects

– Wetlands subfoler or as follows:

The upstream and downstream side slopes of the surface drain block will be 3:1 or flatter. Fill will be compacted as needed to achieve the density of adjacent materials.

When the site has high flow rates or long duration flows from snowmelt or groundwater, the channel will be filled and stabilized with a structure that meets the criteria of 410 - Grade Stabilization Structure conservation practice in FOTG Section IV – Conservation Practices subfolder.

All surface drain blocks or ditch plugs will be crowned to allow for settlement and to prevent concentrated flow over the constructed fill. Minimum overfill will be one-half foot or ten percent of the maximum fill height, whichever is larger.

C. Embankments

An earth embankment may be constructed to create a pool storage volume equal to that which existed prior to conversion of the site.

Plan and install embankments in accordance with the sixth worksheet, titled “Emb Spec” in located in FOTG Section I – Reference Subjects – Wetlands subfoler or as follows:

Embankments with an effective height less than 6 feet will meet design criteria for Classification I dams in the North Dakota State Water Commission (SWC) North Dakota Dam Design Handbook. Conservation practice standard 378 - Pond criteria in FOTG Section IV – Conservation Practices subfolder will be used for all earth fills with an effective height equal to or greater than 6 feet. The effective height of the embankment is the difference in elevation, in feet, between the emergency spillway crest and the lowest point in the cross section taken along the centerline of the embankment.

A minimum of 5 percent overfill will be added to the height of earth embankments to allow for settlement.

Design, Installation, Check out and Documentation Guide - 657

D. Restoration of surface inflow

To the extent practicable, features that divert natural surface inflow away from the wetland shall be removed or mitigated in a manner approved by an NRCS representative on a case-by-case basis.

Subsurface Drain Removal

In areas where subsurface drains were used to remove surface water or soil saturation, the existing system will be modified to restore the wetland hydrologic conditions. Review of drainage records, interviews, and site investigations will be needed to determine the extent of the existing system. The effect of any modification to the existing subsurface drainage system on upstream landowners will be evaluated and the landowners will be notified of potential offsite impacts. This evaluation will include both surface and subsurface impacts.

Where the subsurface drain serves as an outlet for upstream properties, it will be necessary to meet applicable State and local laws and regulations pertaining to subsurface drainage and flooding. Upstream surface and subsurface drainage will not be impacted unless appropriate easements are obtained or mitigation measures are implemented.

The effects of the subsurface drainage system may be eliminated by removing a portion of the drain at the downstream edge of the wetland boundary, modifying the drain with a water control device, or installing non-perforated pipe through the wetland site and adjacent zone of potential lateral effect.

The minimum length of drain to be removed is 50 feet for soils with an average hydraulic conductivity of the soil profile less than 0.6 inches per hour, 100 feet for 0.6 to 2.0 inches per hour, and 150 feet for greater than 2.0 inches per hour. All envelope filter material or other flow-enhancing material will also be removed for this length. The trench will be filled and compacted to achieve a density equal to surrounding material.

A water control device will be placed on the inlet of an existing drain to limit inflow and prevent damage to the drain downstream of the site. If the drain serves other areas, inflow will be limited to the capacity originally apportioned to the drain.

The water control structure will be attached to a non-perforated conduit that extends at least the minimum length previously specified for length of drain to be removed. The connections of the water control structure and the non-perforated pipe will be watertight at the head created at the maximum pool level.

RESTORATION OF HYDRIC SOIL

Sediment and fill shall be removed as directed by an NRCS representative. An NRCS representative shall observe the operation on-site. Sediment shall be entirely removed, or to the extent possible based on normal hydrologic conditions.

RESTORATION OF HYDROPHYTIC VEGETATION

Natural regeneration of vegetative cover may be allowed on wetlands with an adequate seed bank of hydrophytic vegetation. However, “natural” regeneration on North Dakota wetlands typically results in a plant community dominated by invasive species. If an adequate seed bank does not exist, develop a planting plan according to one of the following FOTG Section IV standards; 644 - Wetland Wildlife Habitat Management; 550 - Range Seeding, 390 - Riparian Herbaceous Buffer, or 391 - Riparian Forest Buffer. Also refer to the NRCS Wetland Restoration, Enhancement, and Management Handbook located or linked in FOTG Section I – Reference Subjects – Wetlands subfolder. Species selection shall be limited to native species other than reed canarygrass, due to its aggressive monoculture tendency. Creeping foxtail shall not be planted.

LAWS

Structures with a water storage capacity (spillway elevation) exceeding 12½ acre-feet require FORM 108 Conditional Water Permit from the State Water Commission (SWC) prior to construction or modification activities.

All wetland restorations require completion of the form SFN51695 Application/Notification to Construct or Modify Dam, Dike, Ring Dike or Other Water Resource Facility from the SWC.

Structures with maximum water retaining capacity (top of structure) exceeding 12½ acre-feet will require prior approval from the SWC before commencement of construction or modification.

REQUIREMENTS FOR CONSTRUCTION ACTIVITIES AND FEATURES

The contractor and cooperator are responsible for notifying ND One Call to locate utilities at least 48 hours prior to any excavation, at 1-800-795-0555.

If a cultural resource is identified during construction, the contractor and cooperator shall cease earthwork and notify NRCS immediately at the local field office or by calling 701-530-2089.

Construction operations shall be carried out in such a manner that air and water pollution and erosion are minimized.

Construction activities shall be carried out so that the wetland area is disturbed as little as possible. Existing natural vegetated spillways will be maintained as much as practicable.

Before constructing any features, the foundation area shall be cleared of trees, logs, stumps, roots, brush, boulders, sod, and rubbish. If stripping is required it shall be to a minimum depth of six inches, stockpiled, and spread on areas of compacted earth fill. Foundation surfaces shall be sloped no steeper than 2:1 unless otherwise shown on the drawings. The foundation area shall be thoroughly scarified before placing fill material.

The surface of work areas shall be smooth and present a quality, workmanlike appearance.

The completed work shall conform to the lines, grades, and elevations shown on the drawings or staked in the field.

Pipes and appurtenances shall be suitably bedded and back-filled with materials meeting the requirements stated above. The side slopes of any trenches required for the installation shall be no steeper than 3 horizontal to 1 vertical. All backfill shall be placed in 6-inch layers or thinner and compacted to a density equivalent to or exceeding that of the surrounding fill by means of hand tamping or manually directed power tampers. Manual compaction shall continue to a height of 18 inches above the top of the pipe. Care shall be taken to ensure that compaction does not lift or move the pipe, resulting in a void next to the pipe.

OPERATION AND MAINTENANCE

Develop an Operation & Maintenance Plan for ditch plugs and embankments using the templates found in the ND Wetland Restoration Workbook. Specify the frequency of inspection required, e.g., at least once annually and after runoff events, fire, etc. that may damage or impair the practice.

Inspect water control structures at least once annually and after events that may cause damage or impair their function. Complete repairs effectively and promptly.

Manage vegetation in accordance with conservation practice 644 - Wetland Wildlife Habitat Management or other practices as appropriate;

314 - Brush Management

511 - Forage Harvest Management

595 - Pest Management

338 - Prescribed Burning

528 - Prescribed Grazing

472 - Use Exclusion

CHECK OUT AND DOCUMENTATION

Record the decision-maker’s goals for applying the practice.

Document vegetation planting plans as required for the facilitating practice, i.e., Range

Planting – 550, Riparian Herbaceous Cover – 390, or Riparian Forest Buffer – 391.

Prior to hydrology restoration, documentation of drainage scope & effect by an approved

NRCS representative is required. The data shall be recorded on Form ND-CPA-339 Scope & Effect Data.

Document earthwork hydrology restoration using the North Dakota Wetland Restoration Workbook found in FOTG Section I – Reference Subjects – Wetlands subfolder.

Document removal of subsurface drains with narrative notes that explain all actions taken. Record the locations and elevations of all remaining and removed features with GPS coordinates or a clearly labeled map.

Record depth of sedimentation and depth of sediment/soil actually removed at representative points designated by an NRCS representative with GPS coordinates and/or a clearly labeled map.

In assistance notes, record site-specific conditions, discussion with decision-maker, and any off-site factors relevant to the success or failure of the practice.

A functional assessment may be completed using the appropriate hydrogeomorphic (HGM) model prior to restoration to determine baseline conditions. Successive assessments can be completed to monitor and measure progress/effectiveness of the practice.

Design, Installation, Check out and Documentation Guide - 657

United States Department of Agriculture Natural Resources Conservation Service, North Dakota

STATEMENT OF WORK

Wetland Restoration (657)

Issued: October 2006 Contact: State Biologist at 701-530-2078

DESIGN

Deliverables:

1. Design documentation that will demonstrate the criteria in NRCS practice standard have been met and are compatible with other planned and applied practices:

a. Practice purpose(s) as identified in the conservation plan

b. List of required permits to be obtained by the client:

i. Form SFN1695, Application/Notification to Construct or Modify Dam, Dike, Ring Dike, or Other Water Resource Facility approved by the North Dakota State Water Commission

ii. Form 108, Conditional Water Permit from State Water Commission for wetlands exceeding 12.5 acre feet of storage

c. Impacts on adjacent properties and structures

d. Compliance with NRCS National and State utility safety policy (NEM Part 503-Safety, Subpart A -

Engineering Activities Affecting Utilities 503.00 through 503.06).List of facilitating practices.

e. Certification compliance with NRCS cultural resource policy

f. Practice standard criteria related computations and analyses to develop plans and specifications including but not limited to:

i. Hydric Soils Determination

ii. Hydrology/Hydraulics:

1. Scope and Effect Data Form ND-CPA-336

iii. Structural including hazard class as appropriate

iv. Vegetation:

1. Planning or Data Sheet of Grass and/or Legume Seeding - ND-CPA-9 or equivalent

2. Written plans and specifications including sketches and drawings shall be provided to the client that adequately describes the requirements to install the practice and obtain necessary permits.

3. Design Report and Inspection Plan as appropriate (NEM Part 511, Subpart B Documentation, 511.11 and Part

512, Subpart D Quality Assurance Activities, 512.30 through 512.32).

4. Operation and Maintenance Plan.

5. Certifications that the design meets practice standard criteria and comply with applicable laws and regulations

(NEM Subpart A, 505.03(b)(2)).

6. ND Wetland Restoration Workbook.

7. Design modifications during installation as required.

INSTALLATION

Deliverables:

1. Pre Installation conference with client and contractor.

2. Verification that client has obtained required permits.

3. Staking and layout according to plans and specifications including applicable layout notes:

a. ND Wetland Restoration Workbook

b. Data sheet of Grass and/or Legume Seeding - ND-CPA-9 or equivalent

4. Installation inspection (according to inspection plan as appropriate):

a. Actual materials used

b. Inspection records

5. Facilitate and implement required design modifications with client and original designer.

6. Advise client/NRCS on compliance issues with all Federal, State, tribal, and local laws, regulations and NRCS policies during installation.

7. Certification that the installation process and materials meets design and permit requirements.

United States Department of Agriculture Natural Resources Conservation Service, North Dakota

STATEMENT OF WORK

Wetland Restoration (657)

Issued: October 2006 Contact: State Biologist at 701-530-2078

CHECK OUT

Deliverables:

1. As-Built documentation:

a. Extent of practice units applied

b. Drawings

c. Final quantities

d. ND Wetland Restoration Workbook

e. Data sheet of Grass and/or Legume Seeding – ND-CPA-9 or equivalent

2. Certification that the installation meets NRCS standards and specifications and is in compliance with permits (NEM Subpart A, 505.03(c)(1)).

3. Record progress reporting according to NRCS policy.

REFERENCES

• NRCS Field Office Technical Guide (FOTG) Section IV – Conservation Practices – Wetland Restoration (657) – Standard.

• NRCS Field Office Technical Guide (FOTG) Section IV – Conservation Practices – Wetland Restoration (657) – Design, Installation, Check Out and Installation Guide

• NRCS Field Office Technical Guide (FOTG) Section IV – Conservation Practices – Pond (378)

• NRCS National Engineering Manual (NEM)

• NRCS Engineering Field Handbook (EFH), Part 210, Chapter 13, Wetland Restoration, Enhancement, or Creation

• NRCS Wetland Restoration, Enhancement, and Management Handbook

• NRCS National Environmental Compliance Handbook

• NRCS Cultural Resources Handbook

• NRCS National Biology Manual

• NRCS National Biology Handbook

• National Food Security Act Manual