Stony Clove Project Site Visit

Posted on: August 21st, 2014 by Leslie_Zucker

Here’s a more detailed descrip­tion with pho­tos of the Stony Clove Creek stream restora­tion project under con­struc­tion this sum­mer. The site is locat­ed at the con­flu­ence of Stony Clove Creek and Warn­er Creek and extends down­stream end­ing before the Sil­ver Hol­low Road bridge. A his­to­ry of devel­op­ment and stream ero­sion has led to fre­quent manip­u­la­tion of the site. By 2001, about 1,366 feet of stream banks at the site were active­ly erod­ing and 1,103 feet of banks were lined with rock revet­ment. Floods in 2010 fur­ther desta­bi­lized the stream bed and banks. If left unchecked, bank ero­sion will threat­en both Route 214 and Sil­ver Hol­low Road. The Stony Clove Creek Stream Man­age­ment Plan rec­om­mend­ed full restora­tion of the site. The project under con­struc­tion now imple­ments plan rec­om­men­da­tions, includ­ing instal­la­tion of large step/pool struc­tures to sta­bi­lize the stream bed and direct ero­sive forces away from the banks, and a flood­plain bench veg­e­tat­ed with trees and shrubs installed between the active chan­nel and erod­ing banks.

Stacked Rock Wall

Con­struc­tion of a stacked rock wall to pro­tect the left bank below Sil­ver Hol­low Road.

Glacial Till Streambank

The project should pre­vent and reduce ero­sion of glacial tills and fines that degrade water qual­i­ty and threat­en Route 214 (above).

Sheet Piling Grade Control

Because of the intense stream pow­er through this site, the step/pools installed for grade con­trol are con­struct­ed from met­al sheet pil­ing dri­ven into the ground with a large pneu­mat­ic ham­mer. Here the buried tops of sheet pil­ing can be seen in the stream bed at the feet of Project Man­ag­er Adam Doan, Ulster Coun­ty Soil and Water Con­ser­va­tion Dis­trict, and Site Super­vi­sor Ver­non Bevan, Milone & MacB­room, Inc.  The stream bed will be rebuilt above the sheet piling.

Water Diversion

The flows of Stony Clove Creek are divert­ed around the con­struc­tion site to pro­tect water qual­i­ty and meet per­mit require­ments. The 48″ plas­tic pipe is cov­ered with a con­crete blan­ket. The blan­ket and the cool water flow­ing inside pre­vent the pipes from expand­ing due to sum­mer heat and sun. The pipes can pass stream flow of at least 50 cubic feet per sec­ond (cfs). In this pho­to, the Stony Clove is flow­ing at 12–13 cfs.

Coffer Dam

A met­al cof­fer dam was installed to sta­bi­lize and divert flows around the project site. This dam is tem­po­rary and will be removed.

Project Site Construction

The site at the peak of con­struc­tion. Despite how it appears now, this site will be left in a nat­ur­al look­ing con­di­tion at project end. After the grade con­trol struc­tures are installed, the stream bed will be restored with nat­ur­al cob­ble and large rock boul­ders. Con­trac­tors have set aside native rocks that were left by glac­i­ers and round­ed by mil­len­nia of water flows for place­ment back into the stream. After that, the Stony Clove will do its part to move and sort mate­r­i­al at the site. Work will com­plete by end of September.

The project should result in mod­est fish habi­tat improve­ments. Instal­la­tion of step-pool struc­tures may increase fish pas­sage at low flows and increase the amount of shal­low mar­gins. Instal­la­tion of the bank­full bench with over­head veg­e­ta­tion should pro­vide more cov­er and shad­ing for fish pass­ing through the site. Projects are not con­struct­ed dur­ing trout spawn­ing sea­sons to pro­tect the fishery.