[Code of Federal Regulations]

[Title 40, Volume 24]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR230.25]



[Page 266-267]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 230_SECTION 404(b)(1) GUIDELINES FOR SPECIFICATION OF DISPOSAL SITES 

FOR DREDGED OR FILL MATERIAL--Table of Contents

 

Subpart C_Potential Impacts on Physical and Chemical Characteristics of 

                          the Aquatic Ecosystem

 

Sec.  230.25  Salinity gradients.



    (a) Salinity gradients form where salt water from the ocean meets 

and mixes with fresh water from land.

    (b) Possible loss of environmental characteristics and values: 

Obstructions which divert or restrict flow of either fresh or salt water 

may change existing salinity gradients. For example, partial blocking of 

the entrance to an estuary or river mouth that significantly restricts 

the movement of the salt water into and out of that area can effectively 

lower the volume of salt water available for mixing within that estuary. 

The downstream migration of the salinity gradient can occur, displacing 

the maximum sedimentation zone and requiring salinity-dependent aquatic 

biota to adjust to the new conditions, move to new locations if 

possible, or perish. In the freshwater zone,



[[Page 267]]



discharge operations in the upstream regions can have equally adverse 

impacts. A significant reduction in the volume of fresh water moving 

into an estuary below that which is considered normal can affect the 

location and type of mixing thereby changing the characteristic salinity 

patterns. The resulting changed circulation pattern can cause the 

upstream migration of the salinity gradient displacing the maximim 

sedimentation zone. This migration may affect those organisms that are 

adapted to freshwater environments. It may also affect municipal water 

supplies.

    Note: Possible actions to minimize adverse impacts regarding site 

characteristics can be found in subpart H.