Integrated Training Area Management EA and Final FNSI

Third paragraph should read, "These types of stream bank stabilizationtechniques may be used..."Fourth paragraph, the sentence that reads, "Riprap protects soil fromerosion and is often used on steep slopes built with fill materials thatare subject to harsh weather or seepage." Riprap will not remain stableon slopes steeper than 1.5:1 and must be a gradation of size and shape.Sentence, "It is used where water is turbulent and fast flowing andwhere soils may erode under the design flow conditions." I have seenmany rip rap structures fail under these conditions - it is not a fixall and should not be represented as such! Rip rap structures speed upwater energy, harden the bank and bed surface and can have negativeeffects on downstream banks.The OHMP would like to consider all other options, before agreeing to arip rap structure.Page C2-80. The first sentence on this page should read, "...is usuallyapplied in an even layer along the stream bank." The second sentence ofthis paragraph is confusing - should it be in this section?General comment for this section - vegetation (e.g., live willowstaking, fascine bundles, brush mats and layering) above the rip rap isalways recommended and a preferred technique for these types ofprojects.(25) Page C2-81. B. Rock Armoring. Within the first paragraph, pleaseinclude language stating that these structures are always "keyed-in" atboth the upstream and downstream end of the structure and most often,placed on top of permeable geotextile fabric.Second paragraph, please add to the end of the first sentence, "...(CAT320) from the top of the bank." The next sentence should be deleted --all work should be conducted from the top of the bank and equipmentin-stream (working or crossing) should be minimized if allowed at all.Last paragraph, please change to read, "...and cutting a trench at thetoe of the bank below..."(26) Page C2-82. II. Geotextile. First sentence change the word "toe"to "trench" and delete the word "cut".(27) Page C-82. C. Barb Dikes or Thalweg Deflectors. Could we givethis structure one name and use it throughout? Most agencies recognizethis type of structure as a "rock barb."First paragraph - Please state somewhere in this paragraph that thesestructures must be designed by an experienced hydrologist/engineer.Second paragraph, the second sentence should read, "Silt fences may beinstalled during construction to prevent downstream siltation." Siltfencing is not the only, and not always the best, erosion control methodavailable. Please add to the end of the third sentence, "...and toensure correct placement."_____________________________________________________________________________________________Environmental AssessmentUnited States Army Alaska, Integrated Training Area Management ProgramManagement Plan E-12