Table H3. Contaminated and Cap Material Volumes and Mound Dimensions

Table H3

Contaminated and Cap Material Volumes and Mound Dimensions

Tot Vol, m3

Apron Vol, M3

Footprint, m2,

Max thick, m

( yd 3)

(yd3)

Project

% Total

(acres)

(ft)

Contaminated

Port Elizabeth/

448,000

52,000

11.6

1,470,000

2.40

Newark

(586,000)

(68,000)

(363)

(8.0)

Generic No. 1

96,600

49,900

51.7

785,400

0.9

(Figure H1)

(126,300)

(65,300)

(194)

(3.0)

Generic No. 2

96,600

49,900

51.7

785,400

0.9

(Figure H2)

(126,300)

(65,300)

(194)

(3.0)

Cap

Port Elizabeth/

1,870,000

1,040,000

55.6

1,470,000

1.8

Newark (1 m cap

(2,445,900)

(1,360,300)

(363)

(5.91)

over entire project)

Generic No. 1

847,200

140,400

16.6

1,097,000

0.9

(Figure H1) (0.9 m

(1,108,100)

(183,600)

(271)

(2.95)

cap over entire

project)

Generic No. 2

347,800

15,100

4.3

885,800

0.9

(Figure H2) (0.9 m

(454,900)

(19,750)

(219)

(2.95)

cap over main

mound, 0.3 m cap

over apron)

extends a distance of 15 to 30 m beyond the expected edge of the contaminated

material.

For sites with significant currents (say 30-50 cm/sec and greater) some loss of

cap material will probably be experienced. The Seattle District has documented

that for small sites (100 to 150 m overall dimensions) this "volume lost," which

is a actually cap material that is moved beyond the edge of the contaminated

sediment, can be from 10 to 20 percent of the estimated volume required based

on a flat cap over the contaminated sediment footprint (Parry 1994).

For a fine-grained cap, the volume lost to consolidation will have to be taken

into account for the erosion layer. An estimate of the amount of consolidation

over time will be required and the additional thickness added to account for

potential erosion. Note that the reduced cap thickness from consolidation may

not be a problem from a chemical isolation standpoint due to advection of con-

taminants. The reduced cap thickness from consolidation is somewhat compen-

sated for by the reduced void ratio and permeability, creating more tortuous

paths for the contaminants to diffuse through.

H10

Appendix H Level-Bottom Capping Projects