We may think of each high tide as
a flush: a bolus of toxified water is released,
as from a toilet bowl, into the bay.
Our proposal is to interpose a salt
marsh, as a sort of septic tank
or living machine, between the
dump and the bay.
- We assume that each high tide
(over the level of the salt marsh)
introduces a bolus of sea water
into the dump (the capped volume of the landfill).
- Within the landfill, the bolus of
sea water mixes with a reservoir of
water in which chemicals of concern
(COCs) have dissolved.
- As soon as the tide recedes below the
level of the top of the salt marsh,
this bolus leaches out into the
- The leachate exits into the
root system of the cordgrass
the upper 6 inch layer of the salt marsh.
- The sediments of the salt marsh below
the root system are perpetually saturated
with water, are anoxic, and serve as a
barrier to leachout from the dump.
- Each high tide creates a single pulse
of leach through the upper (root) layer of
the salt marsh, of which
a significant fraction consists of the
rhizosphere of cordgrass.
Revised by Ralph Abraham 16 August 1998