1. EPA Region 7 Lead Remediation Byrnes Mill Dam and Park
Future Phases Presentation
Prepared by:
Joseph Asher Leff, PE (USACE)
Cody McLarty, PMP (USEPA)
Greg Bach (USEPA)
For the City of Byrnes Mill, Jefferson County, Missouri
26 April 2017

2. contents History Project Objectives Conceptual Plan Refined Plan
Lead Mining
Byrnes Mill Dam
Lead Impacted Sediment
Project Objectives
Conceptual Plan
Refined Plan
Schedule

3. Lead mining History
Historic lead and zinc mining occurred in Jefferson, Washington, St. Francois and Madison Counties from 1720 to 1972
Mining and milling of ore produced millions of tons of lead by-products (tailings) that washed into the Big River Watershed over time
Lead by-products have continued to migrate through the Big River
USEPA is working with USACE and others to reduce potential health risks associated with mining by-products in the Big River watershed by removing and preventing reintroduction of impacted sediment
Eroding Tailings Pile,
Tailings Pile near Park Hills,

4. History of Byrnes mill dam
Drawing by Kathy Koebel 1988
Photo, source unknown
Constructed in the Civil War Era, late-1800s
Mill operated until at least 1935
Photo from Jefferson County Library

5. Civil War Era mill Dam Construction
Foundations formed from timber cribbing filled with rough quarry stone.
Exterior constructed of stacked trapezoidal-cut stone.
Rockford Beach Dam ca. 1800s, Source Unknown
Typical Foundation Sketch, U.S. War Department :Plate 53-3

6. Byrnes mill dam – partial collapse
Byrnes Mill Dam experienced a partial collapse along the left-descending (West) bank prior to February 1968
Collapse reduced the hydraulic load from the river flows on the remnant portion
Little change is visible since the collapse
USGS Aerial Photo, dated February 23, 1968
USGS Aerial Photo from Google Earth, dated April 2, 1992

7. Lead Impacted Sediment in Byrnes Mill Park
Phase 1 removed and replaced 12” of park-floodplain topsoil
High concentrations of lead have also been found in the “whirlpool area” downstream of the remnant dam
The flow through the breached portion of the dam cause a gentle whirlpool effect
The current conditions allow lead-impacted sediment to settle within the whirlpool area during low- and moderate-river flows

8. Phase 2 Project objectives
Remove lead-impacted sediment collected below the remnant Byrnes Mill dam (“Whirlpool”)
Determine effectiveness of future removals
Ensure the remnant Byrnes Mill Dam doesn’t collapse further

9. Phase 2 Conceptual Plan – February 2017
Focused on Stabilizing the Dam
Assumed the dam condition to be as poor as Rockford Beach Dam
Raised concerns with changes to the dam’s appearance and affects to the river flow
Proposed using excavators to remove material from whirlpool
Required additional access, and a special area to prepare the removed material for transport
Raised concerns with altering the park views, removing trees, park closures, and the possible release of contaminated material during potential floods
The Board of Aldermen voiced these concerns during the February 15th presentation, and USACE and USEPA further refined the plan to address them

10. Refined Plan Divides the plan into two further phases:
Phase 2 focuses on remediation of Whirlpool area while limiting impacts to the park
Remediation done with dredge
Dewater material using mobile, low-impact methods
Monitor the dam condition to ensure it does not deteriorate further
Phase 2b – Dam Stabilization if needed (Contingency Plan)

11. Phase 2: Whirlpool remediation Proposed Lead-Impacted Sediment removal process
Uses compact hydraulic dredge to remove material
Dredged sediment and water pumped into Geotextile Dewatering Tubes to safely remove water without releasing sediment
Tubes filled with dried material removed to disposal site with minimal impact to park
Example Compact Dredge,
Geotextile Dewatering Tube,

12. Phase 2b: Dam stabilization Contingency Plan
Stabilization will not occur unless new evidence of collapse is discovered during monitoring
Stone will be lower than the top of current dam to reduce changes to visual appeal and hydraulic conditions

13. Schedule
Phase 1: Lower Floodplain Bench/Park Remediation – Completed October 2015
Phase 2: Whirlpool Remediation – Completed by December 2017
Phase 2b: Dam Stabilization – Only if needed to prevent collapse

14. Backup slides

15. USGS Surveys - January 2017
Terrestrial LiDAR and Multibeam Bathymetric surveys were completed in January and show the dual scour areas and remnant dam.
Color scheme shows elevation differences

16. USGS Surveys - January 2017

17. USGS Surveys - January 2017
A bench has formed downstream of the dam, likely by stone washed down from the dam structure.
Millhouse Foundations
Downstream Bench
Remnant Dam
Remnant Dam Scour Pool
Remnant Dam Foundation
River Thalweg Scour Pool

18. Phase 3: Dam stabilization Contingency Plan

19. Rockford beach dam stabilization project Completed June 2016

20. Rockford beach dam stabilization project
March 7, 2016
June 27, 2016

21. Rockford beach dam 2015
Dam extended fully across the Big River channel – full force of the river
Showed signs of continued collapse
Continued to degrade until stabilized

22. Dam Stabilization Crushed Stone Riprap Photo by Joseph Asher Leff
USACE, 9/2/2016

23. April 2016 New Gravel Ramp down Photo by Joseph Asher Leff
USACE, 4/25/2016

24. New Ramp Excavated Slope, with Grass Drainage Ditch New Gravel Ramp A
Photo by Joseph Asher Leff
USACE, 4/25/2016