Lower Mud Industry Days October 2025.pdf

LOWER MUD RIVER

MILTON, WV

FLOOD DAMAGE REDUCTION

PROJECT

Lower Mud River, FRM Industry Days Project Overview

21 October 2025

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AGENDA

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Generator

1. Introduction

2. Project Location

3. Plan Features

4. Overview of Proposed Plan

5. Design and Construction Assumptions

6. Questions

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PROJECT LOCATION

Milton, WV

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LOWER MUD RIVER FLOOD RISK MANAGEMENT

City of Milton

Simulated 1% Annual Chance of Exceedance (100-year Flood Event)

Majority of the City of Milton lies within the 100-year floodplain – limiting future economic growth and development

Flood of Record within Milton is estimated at a 3.7% annual chance of exceedance (27-year flood event)

Estimated damage to residential and commercial structures during the 1% annual chance of exceedance (100-year flood event) is over $68M ► Damage would occur to approximately 550 structures including 145 commercial structures

Additional consequences associated with flooding ► Life safety risk ► Damage to infrastructure including utilities, roadways, and bridges ► Vehicle damage ► Cost of emergency response and recovery ► Loss of economic productivity

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Recent Flooding – 2023 Event – Existing Condition

Existing Condition:

• Inundation boundary based on aerial photography and highwater marks.

This plan simulates the 2023 event existing condition using gridded rainfall data from the National Weather Service (NWS).

Inundation Boundary shown is > 0.5-ft in depth

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PLAN FEATURES

Plan Features (designed for 0.4% annual chance of exceedance (250-year return frequency) ) ► Approximately 6,800 LF earthen levee with full depth seepage barrier w/Managed Overtopping

Section ► Concrete Floodwall: approximately 1,500 LF with full depth sheet pile ► 2 Pump Stations with excavated ponding areas (Johns Branch and Newmans Branch) ► 5 Gravity Outfalls through the levee/floodwall including one at each pump station ► 1 Closure Structure (Stop Log Closure at Bill Blenko Drive) ► Relocation of Approximately 1,200 linear feet of the Mud River shortened to approximately 800 linear feet of new channel ► Relocation of City Raw Water Intake and Low Flow Weir ► Channel Geometry Benching along Mud River ► Environmental mitigation features ► Stone Slope Protection ► Utility Relocations

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PROPOSED PLAN WITH BORROW SITES

BORROW 5

BORROW 1

EAST & WEST

BORROW 3

PRESERVATION

SITE

PRESERVATION

SITE

BORROW 2

LAGOONS TO BE

DECOMMISSIONSED

LINE OF

PROTECTION

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HAUL ROUTES FOR BORROW/SPOIL SITES

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PROPOSED PLAN

* Not inclusive of all proposed real estate needs for project

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CHANNEL MODIFICATIONS

Channel Modification planned for the majority of the river along the length of the project to improve hydraulic efficiency to offset induced hydraulic impacts caused by project construction.

Terrace Benches planned approximately 1’ above normal flow in the river. Average width varies from 25’-35’

Slopes improved to 1 vertical to between 3 to 8 horizontal. 1:6 is the most common.

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LEVEE SECTION

Levee Features:

1. ~6,800 ft. in Length

2. 19 ft. in Height (Average)

3. Impervious Earth Fill Composition

4. Cutoff Wall/Seepage Barrier

a. ~Full length of levee

b. Variable Depth to Bedrock (approx. 7’ to 69’, average 42’)

5. Aggregate Crest Access Road

6. Aggregate Interior Toe Access Road

7. Sloping superiority added to levee top.

8. Managed Overtopping included

9. Filter Drainage (where applicable) 10.Stone Slope Protection

a. Select Sections of River Side

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CONCRETE FLOODWALL SECTION

Concrete Floodwall Features:

1. ~1,500 ft. in Length

a. Pile Foundation required full length of floodwall

2. 14 ft. Stem Height in most locations

3. 8’10” Stem Height in some areas

4. Sheetpile full depth cutoff

a. ~Full length of wall

b. Variable Depth to

Bedrock (approx.

7-70’)

a. Median 45 ft

b. Average 42 ft

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CLOSURE STRUCTURE

Stop Log Gate Closure Features:

1. Closure Width: 33’-3”

2. Closure Height: 6-5”

3. Two (2) Support Posts

4. Three (3) Stop Log Bays

5. Storage Building Adjacent to T- Wall

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PUMP STATION AND GATEWELLS

2 Pump Stations Each Pump Station has a gravity culvert, gatewell, and discharge lines over the levee Each Pump Station has 3 pumps sized to handle a 4% AEP (25-year) Interior Event

JOHNS BRANCH PUMP STATION NEWMANS BRANCH PUMP STATION

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GATEWELLS

5 total Gatewells for gravity flow. 2 are located adjacent to the pump stations All Gravity Culverts have an Active Closures (Sluice Gate) and Passive Closures (Flap Gate)

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LOW FLOW WEIR

Concrete Capped Sheetpile Weir approximately 142’ in length

Placed Directly downstream of the Relocated Channel Low Flow Weir will be modified to a T-Wall due to depth to bedrock

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LOW FLOW WEIR ROCK RAMP

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RAW WATER INTAKE

RAW WATER INTAKE

PLAN VIEW

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MITIGATION COMMITMENTS

Resource Categories Mitigation Commitments Vegetative and Terrestrial Resources Establishment and preservation of bottomland hardwood habitat to meet Habitat Evaluation Procedures Habitat Unit debits.

Establish: approximately 14 acres (additional existing habitat incorporated into restoration/mitigation areas; total = 17 acres)

Preserve: Approximately 24 acres

Average Annualized Habitat Units: ~ 2.15 AAHU

Wetlands Will be completed through compensatory mitigation – utilizing either the approved WV in-lieu fee program or mitigation banks. Functional assessment was used to determine impacts (WVWRAM).

The proposed wetland mitigation has been updated since the 2024 DPR/SEA based on continued coordination with resource agencies.

Originally, onsite mitigation was proposed through establishment and restoration of wetlands in the project area. However, based on more recent coordination the agencies have determined that the use of in-lieu fee program or mitigation banking would provide more confidence for success of mitigation wetlands.

Aquatic Resources Mud River relocation and stone buttress:

a. Mud River relocation and stone buttress:

i. approximately 13,000 LF of preservation/natural succession mitigation upstream and downstream of the main project area.

ii. Potential improvements for two carry down launches in the Milton area to provide an improved connection of the community to the Mud River muskie fishery.

b. Tributary streams: Compensatory mitigation through in-lieu fee program.

Threatened and Endangered Species Seasonal tree clearing restrictions to minimize potential impacts to listed bat species (approx. Nov 15 – March 15 clearing window)

Noise and Vibration Plans and specifications outline decibel level restrictions and monitoring commitments that the Contractor shall comply with. If noise levels exceed the thresholds, it would be the responsibility of the contractor to implement mitigation strategies such as physical noise barrier walls, noise reduction technology, or modifying construction times.

Recreation Providing ingress/egress access roads for the Pumpkin Park in the parking area where the current road would be impacted by construction, and for the little league’s northern most field at a minimum for the Pumpkin Festival.

Traffic and Transportation Mitigation for potential traffic impacts would be coordinated with WVDOH. The Contractor would have to follow requirements set forth by WVDOH for hauling on public roads and would have to utilize best management practices to ensure community safety.

Cultural Resources The programmatic agreements assure Section 106 would be followed through prior to potential impacts to Historic Resources.

Other Requirements/Commitments A Risk Communication and Evacuation Plan shall be coordinated and developed.

Best Management Practices for construction activities would be utilized.

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PROPOSED MITIGATION FEATURES

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GENERAL CONSTRUCTION:

• The project is in a downtown area that is flood prone. It is likely that the project will experience high water events one or more times during construction.

• Period of performance is assumed to be 4 years and 9 months.

• Borrow sites are dual purpose. These sites will be used for borrow materials for both impervious levee fill and random, but will also serve as spoil sites for soil not used for in construction or excess materials.

• Tree clearing seasonal restriction: Clearing is only permitted from Nov 15 – March 31.

• Construction noise thresholds at the receptors: 65 dbA continuous; 90 dbA impulsive.

• One growing season for seeding in excavated channel prior to opening flow.

ASSUMPTIONS AND DESIGN CONSIDERATIONS

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CONSTRUCTION SEQUENCING:

• Construction in the winter season is impacted by:

o Low temperatures and reduced sunlight can increase work needed to dry soils to optimum moisture.

o High water events are more common between November and April.

o Temperatures can be below freezing for extended periods.

• Various features will require curing time or settling prior to commencement of construction of specific features. For example, the overtopping section cannot be constructed until the levee has settled for a specified amount of time.

• Construction sequencing will require pump station foundations, cast-in-place box culverts, and gatewells to be constructed prior to commencement of levee construction in those areas.

• Construction sequencing is important for completion of project features. Stormwater management during construction is critical to sequencing and implementation of project features. Proposed drainage features will need to be completed prior to existing streams and culverts being impacted.

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FOUNDATION:

• The geologic stratigraphy of the site is variable, and consistent with alluvial processes. The thickness of overburden above rock ranges approximately from 7 - 70 feet with an average of 42 ft. The overburden generally consists of a surficial fine-grained clayey layer underlain by sandier soils.

These sandy soils consist of loose silty sand and poorly graded sand deposits with limited lenses of silts and clays. The sands typically reached medium dense conditions within 10 ft. of bedrock. A lower clay lens is intermittently present across the site.

• Near stations 102+00 to 114+00 and 147+00 to 150+00, fill material has been placed to support local infrastructure. The fill is variable in characteristics and is known to contain rubble/unsatisfactory material. It generally consists of a sandy clay matrix and is present at approximate thicknesses of 15 feet. This fill will be overexcavated to a depth of 10 ft prior to placement of the levee.

CUTOFF WALL:

• Draft Seepage Barrier Performance Criteria:

o Maximum Permeability: 1 e -6 cm/sec o Minimum barrier width: 3 ft o Depth: Top of rock o Sheetpile will be driven through the cutoff wall at the tie-ins with the structures.

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LOW FLOW WEIR:

• Depth to Bedrock is insufficient for developing a stable sheetpile cofferdam in the river for the construction of the low flow weir/raw water intake.

SLUICE AND FLAP GATES:

• The sluice gates and flap gates are all thimble mounted. It is assumed that the thimbles can be aquired in time to avoid delays in the construction of the structures.

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QUESTIONS?