UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 7

ACTION MEMORANDUM

11201 Renner Boulevard Lenexa, Kansas 66219

JUN 2 9 20.I

SUBJECT: Request for a Time-Critical Removal Action to Stabilize the Rockford Beach Dam, Southwest Jefferson County Mining Site OU 4, Jefferson County, Missouri.

FROM:

THRU:

TO:

~ulDoherty ,/ v un-Scene Coordina r

~cott Hayes, Chief · ~ Emergency Response

Mary P. Peterson, Director Superfund Division

CERCLIS ID# Site ID# Category of Removal Nationally Significant/Precedent Setting:

I. PURPOSE

MON000705443 A7D2 Time Critical No

The purpose of this Action Memorandum is to request and document approval and funding for a time-critical removal action to stabilize the Rockford Beach dam on the Big River, near House Springs, Missouri, which is located within the Southwest Jefferson County Mining Superfund Site (the Site). The time-critical removal action will involve, among other things, the placement of additional rip rap along a failing section of the dam to prevent catastrophic failure of the dam. The failure of the dam would result in the release of lead-contaminated sediments farther downstream on the Big River that would threaten three federally listed mussel species and a diverse and populous native mussel community.

This time-critical removal action is necessary to mitigate the immediate threat to the environment posed by lead-contaminated river sediments. Lead is a "hazardous substance" as defined by Section 101(14) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), 42 U.S.C. § 9601(14), and is a designated hazardous substance per 40 C.F.R. § 302.4.

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There are no nationally significant or precedent-setting issues associated with .the Rockford Beach dam.

II. SITE CONDITIONS AND BACKGRO"iJiijdl.

A. Site Description

1. Removal site evaluation

The United States Environmental Protection Agency, Region 7, is currently overseeing an investigation of the Big River, which flows north from Iron County through St. Francois, Washington and Jefferson Counties, Missouri. .This.investigation is not complete,.but has shown that portions of the sediments and stream.banks of the Big River are contaminated with lead mine waste. The Big River watershed encompasses several Superfund sites, including the · Southwest Jefferson County Mining Superfund Site whicp focuses on an area located in the southwest quarter of Jefferson County, exduding the area surrounding the Herculaneum smelter. The Site includes residential properties where lead contaminated mine waste has coine to be located, contaminated groundwater, and river and floodplain sediments.

On January 16, 2015, the Missouri Department of Natural Resource!f{MDNR), Dam and Reservoir Safety Program, inspected the Rockford Beach dam. State inspectors reported substantial deterioration of the dam and described it to be in a state of partial failure. Sections of the original stone dam had washed away leaving voids beneath the surficial concrete shell. State inspectors reported significant loss of the dam occurring within the last few months. State inspectors reported that unless emergency stabilization actions were undertaken soon, total breach of the dam was inevitable, Because of the size of the structure, the dam is not subject to the permit requirements of Chapters 236.400 through 236.500 of the Revised Statutes of Missouri.

2. Physical location and characteristics

The Rockford Beach dam is located 1.5 miles northwest of House Springs, Missouri off of '· Missouri Highway EE in Jefferson County, Missouri at United States Geological Survey River Mile Marker 10.5. The coordinates are 38.421664; -90.5888586. The dam is the historical location of the Rockford Mill, built in the 1890s. During the mill's operation, a low head dam was built across the river to impound water to power the mill. The original dam was likely built using cedar log cribbing backfilled with rock. A concrete capping was added to the structure at a later date. While the current dam is deteriorating, it does provide a barrier to the downstream migration of lead-contaminated sediment.

3. Release or threatened release into the environment of a hazardous substance, or pollutant, or contaminant

The primary contaminant of concern is lead and lead compounds that settled and accumulated in the river sediments within the impoundment created by the dam. The MDNR has documented

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total lead concentrations in river sediments immediately upstream of the Rockford Beach dam at levels as high as 1,051 milligrams per kilogram (mg/kg).

Lead is a "hazardous substance" as defined by Section 101(14) of the CERCLA, and is designated as a hazardous substance at 40 C.F.R. § 302.4.

4. NPL status

The Rockford Beach dam is within operable unit 4 of the Southwest Jefferson County Mining Site which was proposed for inclusion on the National Priorities List (NPL) on April 9, 2009, and listed on September 23, 2009.

5. Maps, pictures, and other graphic representations

A site location map and a map showing sampling locations are attached as Figures 1 and 2.

B. Other Actions to Date

Other than the dam inspections previously mentioned, there are no other actions ongoing or planned, relative to the Rockford Beach dam stabilization issue.

C. State and Local Authorities' Roles

On January 16, 2015, the MDNR Dam and Reservoir Safety Program, performed a visit to the Rockford Beach dam. This inspection reported substantial deterioration of the dam and described it to be in a condition of partial failure. Recent flooding has removed significant sections of the original stone dam leaving voids beneath the surficial concrete cap. State inspectors reported significant loss of the dam occurring within the last few months. State inspectors reported emergency stabilization actions are necessary immediately to prevent the total breach of the dam. Because of the size of the structure, the dam is not subject to the permit requirements of Chapters 236.400 through 236.500 of the Revised Statutes of Missouri.

IV. THREATS TO PUBLIC HEALTH OR WELFARE OR THE ENVIRONMENT AND STATUTORY AND REGULATORY AUTHORITIES

A. Threats to Public Health or Welfare or the Environment

At any release, regardless of whether the site is included on the NPL, where the lead agency makes the determination, based on the factors set forth in Sect.ion 300.415(b)(2) of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), that there is a threat to public health or welfare or the environment, the lead agency may take any appropriate removal action to abate, prevent, minimize, stabilize, mitigate, or eliminate the release or threat of release. The factors in 40 C.F.R. § 300.415(b) (2) that apply to this action are:

300.415(b)(2)(i) - Actual or potential exposure to nearby human populations, animals, or the food chain from hazardous substances, or pollutants, or contaminants.

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The purpose of this removal action is to stabilize the dam to prevent failure, which would result in the release of lead-contaminated sediments that have accumulated behind the dam. This release would adversely impact a large and diverse freshwater mussel bed (including three federally listed species) located directly downstream. One of the primary factors affecting sensitive mussel species in the Big River is the presence of metal contamination in the sediment and the adjacent floodplain.

The United States Fish and Wildlife Service (USF&WS) has proposed a bulk sediment concentration of 224 mg/kg as a protective value for freshwater uninoid mussels. This value is based on data collected as part of an extensive study of the remaining mussel beds in the Big River1• The EPA concurs with the use of this value as a removal action level based on the information available to date.

300.415(b)(2)(iv) - High levels of hazardous substances or pollutants or contaminants in soils largely at or near the surface, that may migrate.

Sediment analysis from 14 samples collected by the MDNR on March 16 - 17, 2015, detected lead in river sediments at levels as high as 1,051 mg/kg, with a mean lead concentration of 540 mg/kg using x-ray fluorescence (XRF) instrument readings. Additional XRF readings downstream of the dam near a known mussel bed with federally-listed species indicated sediment lead concentrations of 59 mg/kg and 78 mg/kg. Actions to stabilize the Rockford Beach dam are necessary to protect these downstream mussel communities.

300.415(b)(2)(v) - Weather conditions that may cause hazardous substances or pollutants or contaminants to migrate or be released.

Inspectors from the the MDNR Dam and Reservoir Safety Program have stated that the dam has experienced substantial deterioration and is in a state of failure. The inspectors have speculated that the dam will experience a total breach if not stabilized. This failure will most likely occur during a high water event. If such a failure were to occur, a secondary flood wave from the breach could result mobilizing a significant amount of lead-contaminated sediment downstream affecting federally listed mussel species and their habitat.

300.415(b)(2)(vii) ·The availability of other appropriate federal or state mechanisms to respond to the release.

In a meeting with the EPA on February 13, 2015, the MDNR requested that EPA initiate an action to stabilize the Rockford Beach dam. The State has stated that it has no financial resources or mechanisms currently available to address the issue in a timely manner. Further, the State has concluded that the joint Natural Resource Damage trustee funds and resources could not be used to mitigate this threat.

1 Roberts, AD., D. Mosby, J. Weber, J. Besser, J. Hundley, S. McMurray, and S. Fairman. 2009. An Assessment of Freshwater Mussel (Bivalva Margaritiferidae and Unionidea) Population and Heavy Metal Sediment Contamination in the Big River, Missouri. A Report by the USFWS for Natural Resource Damage Assessment of the Big River (hereinafter the "Roberts Study").

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V. ENDANGERMENT DETERMINATION

The Big River has a diverse mussel community. During the Roberts Study a total of 2,198 living specimens representing 33 uninoid species were found within 19 study reaches in the Big River. Nine species of state conservation concern were found, including three federally listed species (Lampsilis abrupta, and Leptodea leptodon and the recently listed Cumberlandia monodonta). The majority of mussel diversity and abundance in the Big River occurs downstream of the Rockford Beach dam.

As benthic, filter-feeding organisms, freshwater mussels are directly exposed to contaminants in sediment, surface water, and pore water. Freshwater mussel communities in the Big River have been impacted by mining activities, as native freshwater mussels are essentially extirpated in the Big River near mining source areas2

• Moreover, the Roberts Study found significant negative correlations between mussel species richness/abundance and metal contamination in sediment in the Big River. Therefore, the potential impact of heavy metal migration to the lower Big River on mussel abundance and endangered mussel species is a significant concern.

The actual release of a hazardous substance, in the form of lead-contaminated sediments, from the Rockford Beach dam, if not addressed by implementing the response action selected in this Action Memorandum, presents an imminent and substantial endangerment to the environment due to the toxicity of lead to downstream endangered species mussel beds.

VI. PROPOSED ACTIONS AND ESTIMATED COST

A. Proposed Actions

1. Proposed action description

Several alternatives were considered to stabilize the remnants of the dam to reduce the risk of further movement of the structure and the release of contaminated sediments downstream. Options to remove and replace the existing structure or to remove contaminated sediment prior to stabilizing the dam were rejected as potentially inconsistent with the long-term remedial objectives which are in development by EPA for the Southwest Jefferson County Mining Superfund Site.

To minimize the disturbance of lead-contaminated sediments and avoid material handling issues, the proposed action will add bed materials to the existing dam structure to stabilize it in place. Construction is planned to be conducted from the downstream side.

Sheet pile walls would not be cost-effective due to the potentially shallow bedrock at the dam. This feature will prevent the necessary sheet pile embedment depth needed for structural stability.

2 Roberts Study; Buchanan, 1979.

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The stabilization alternative selected is a rock fill berm placed downstream of the dam. Properly sized and constructed, this alternative would stabilize the dam in its current location and condition. Since the fill placement is downstream of the failed dam, the disturbance of lead­contaminated sediments would be minimized. A majority of the rock fill berm would consist of a mixture of small cobbles and gravel. Several sections extending the length of the dam would conceptually be made of larger diameter boulders (3' to 6') to act as weirs on the face of the berm. A generalized plan and typical section for this alternative is presented in Figure 3 (attached).

2. Contribution to remedial performance

The fund-lead actions proposed in this Action Memorandum would not impede any future remedial plans or other response and are expected to be consistent with any long-term remedy in that they address the immediate environmental threat posed by lead-contaminated sediments presently contained by an unstable dam structure.

3. Action/cleanup level

The USF&WS has proposed a bulk sediment concentration of 224 mg/kg as a protective value for freshwater uninoid mussels. This value is based on data collected as part of an extensive study of the remaining mussel beds in the Big River3

• The EPA concurs with the use of this value as a removal action level based on the information available to date.

4. Applicable relevant and appropriate requirements (ARARs)

Section 300.415(j) of the NCP provides that fund-financed removal actions under Section 104 shall, to the extent practicable considering the exigencies of the situation, attain ARARs under federal environmental or state environmental facility siting laws.

The EPA has requested potential state ARARs for this Site. When received, these ARARs will be evaluated per the EPA guidance on consideration of ARARs during removal actions.

5. Project schedule

Following to approval of this Action Memo a meeting will be scheduled with EPA's Emergency and Rapid Response Services (ERRS) contractor, the state, USF&WS, and the U.S. Army Corps of Engineers to discuss design requirements and scheduling. A detailed project schedule will be developed following that meeting.

B. Estimated Costs

The proposed configuration for a rock fill berm using the existing river width and depth will require approximately 1,700 cubic yards of rock. The rock fill material placement cost is estimated to be $100 per cubic yard, thus a construction cost of $170,000. This estimate considers that workers will likely need to be HAZWOPER trained.

3 Roberts Study.

6

To refine the design of the selected alternative, it may be necessary to conduct additional design studies to complete final design plans and specifications. If additional engineering design studies, plans and specifications are required may add an additional 50% to construction costs ($85,000).

The costs associated with this removal action are summarized below:

Extramural Costs Removal Costs 20% Contingency Removal Ceiling

$310,000 $ 62,000 $372,000

EPA direct and indirect costs, although cost recoverable, do not count toward the Removal Ceiling for this removal action. Refer to the enforcement section for a breakout of these costs.

VII. ENFORCEMENT

See the attached Confidential Enforcement Addendum. For NCP consistency purposes, it is not a part of this Action Memorandum.

The total EPA costs for this removal action based on full cost-accounting practices are estimated to be $633,886.

EPA Extramural Costs EPA Intramural Costs EPA Indirect (50.21 % of all costs) Total Costs

$ 372,000 $ 50,000 $ 211.886 $ 633,886

Direct costs include direct extramural and direct intramural costs. Indirect costs are calculated based on an estimated indirect cost rate expressed as a percentage of site-specific direct costs, consistent with the full cost-accounting methodology effective October 2, 2000. These estimates do not include prejudgment interest, do not take into account other enforcement costs, including Department of Justice costs, and may be adjusted during the course of a removal action. The estimates are for illustrative purposes only and their use is not intended to create any rights for responsible parties. Neither the lack of a total cost estimate nor deviation of actual total costs from this estimate will affect the United States' right to cost recovery.

VIII. EXPECTED CHANGE IN THE SITUATION SHOULD ACTION BE DELAYED OR NOT TAKEN

Delayed action will allow the further deterioration and possible failure of the Rockford Beach dam. The dam failure will result in the downstream release of lead-contaminated sediment which will have an adverse, if not catastrophic, impact on downstream federally-listed mussel species and their habitats.

IX. OUTSTANDING POLICY ISSUES

None.

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X. RECOMMENDATION

This decision document represents the selected removal action for the contaminated river sediments at the Rockford Beach dam. The removal action was developed in accordance with CERCLA, as amended, and is not inconsistent with the NCP. This decision is based on the Administrative Record for the site.

Conditions at the site meet the criteria set forth in Section 300.415(b) of the NCP for a removal action, and I recommend your approval of this proposed removal action. The removal action ceiling will be $372,000. These funds come from the regional removal allowance.

Approved:

Attachments:

Figure 1 - Site Location Map Figure 2- 2014/2015 MDNR Sediment Sampling Results Figure 3 - Rock Fill Dam Details

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Figure 1

Site Location Map

Rockford Beach Dam

Jefferson County, MO

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MDNR Spring 2015 Samp~ing

• The average of 14 samples :s-cree ed in the field wit XRF

above the dam wos 540 ppm fead

• XRF values ;ndicated on map

G ;wel b;a (P ON Fea 20 4 >:R I: S.9 • The average of 7 of these sa pies submitted or r a oratory

analysis vas 631 ppm lead

M s~e l b!:d 'MDN R Feb 2104 . llf ' : 78

.it~ o-r : i556: 7-1~~ 1,o s1: 14-21'': 83 ... ; .21-28": 430

• All sa pies were collected above the dam in 2015. • For co pair ison p rposes N R provided X RF resu ts for 2

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Figure 2

2014/2015 MDNR Sediment Sampling Results

Rockford Beach Dam

Jefferson County, MO

Figure 3

Rock Fill Dam Details

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Figure 3

Rock Fill Dam Details