Dredging in an Active Artillery Impact Area Eagle River Flats, Alaska

Dredging in an Active Artillery Impact Area

Eagle River Flats, Alaska

MICHAEL R. WALSH, EDWIN J. CHAMBERLAIN, KAREN S. HENRY,

DONALD E. GARFIELD AND ED SORENSON

efficiently conducted. Environmental impact, al-

INTRODUCTION

though not negligible, can be minimized through

Ongoing investigations into the waterfowl die-

a careful dredging strategy and specific design

offs and the persistence of the causal agent, white

criteria.

phosphorus, in Eagle River Flats, an estuarine salt

This report describes the preparations for

marsh and military impact area, indicate that any

dredging carried out during the spring and sum-

remediation strategy will have to include consid-

mer of 1994, and the short dredging operations

eration of removal and controlled processing of

conducted in mid-October of that same year. A

contaminated sediments. Contaminated areas that

detailed description of the retention basin design

are constantly flooded, such as the deeper ponded

and performance is included. This project was a

areas, do not allow natural drying of the soil and

joint effort between the U.S. Army Cold Regions

subsequent sublimation of the residual white

Research and Engineering Laboratory (CRREL),

phosphorus (WP) particles. Some of these perma-

the U.S. Army Corps of Engineers, Alaska District

nently flooded areas are interconnected over large

(COE-AK), and the Environmental Division of the

areas and would be impractical to address through

U.S. Army, Alaska, Directorate of Public Works

pond draining. These areas, which are generally

(DPW).

vegetated and heavily used by affected dabbling

ducks and swans, have been found to be contami-

nated even after five years in which no WP rounds

FEASIBILITY STUDY

have been fired into the Flats. Although some ar-

eas of the Flats have shown evidence of natural

Before dredging could be considered as a

remediation due to drying cycles, the ponded ar-

remediation strategy, a feasibility study needed to

eas still pose a substantial risk to waterfowl.

be conducted to ensure that dredging was a vi-

The objective of this project is to investigate the

able option. This was conducted by Walsh and

feasibility of using a small, remote-controlled

Garfield. Dredging in Eagle River Flats is unique

dredge to remove sediments from contaminated

for one major reason: the potential presence of

ponded areas and treating the spoils in an open

large quantities of unexploded ordnance (UXOs).

retention basin. The treatment method will be

Other factors that will affect dredging include the

natural drying via atmospheric exposure conse-

seasonal high tides, elevating the spoils to the

quently resulting in the sublimation of the con-

holding pond on the explosive ordnance disposal

taminant, white phosphorus. Spoils are to be moni-

(EOD) pad, the presence of vegetation and drift-

tored prior to deposition in the retention basin,

wood, the long pumping distances, and, of course,

and studies initiated to determine the fate of the

the white phosphorus. The feasibility study was

contaminated sediments undergoing treatment in

conducted in two phases. The first was a review

the basin.

of available basic literature on dredging followed

Dredging was chosen as a method of reme-

by a more specific literature search. The second

diation because of the positive displacement of the

phase involved contacting and visiting manufac-

contaminated material and the ability to treat the

turers of small dredges to brief them on the unique

material in a controlled environment. Using a

situation at Eagle River Flats (ERF) and to discuss

small dredge, limited areas can be addressed and

the feasibility of the pilot project, as well as to so-

transport of the contaminated material (spoils) to

licit their ideas on how it could be done.

a retention basin for treatment can be quickly and

Due to the short amount of time available for