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

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

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, http://www.rootsweb.ancestry.com/ Tailings Pile near Park Hills, http://www.nbcnews.com/

History of Byrnes mill dam Drawing by Kathy Koebel 1988 http://www.byrnesmill.org/the_mill.htm Photo, source unknown Constructed in the Civil War Era, late-1800s Mill operated until at least 1935 Photo from Jefferson County Library

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 1891-1895:Plate 53-3 http://www.crt.state.la.us/dataprojects/archaeology/virtualbooks/BAILEYS/dam.htm

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

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

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

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

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)

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, http://www.eureka-dredgers.com/ Geotextile Dewatering Tube, http://www.caribbeangeotextiles.com

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

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

Backup slides

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

USGS Surveys - January 2017

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

Phase 3: Dam stabilization Contingency Plan

Rockford beach dam stabilization project Completed June 2016

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

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

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

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

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