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1r <br />V <br />rv-:. <br />‘rFA'- <br />f;.;. <br />•■> <br />iv- <br />I’ . <br />■M <br />Hand-placed riprap should be roughly square or rectan­ <br />gular to facilitate placement by hand or derrick. Hand- <br />placed riprap is easily disrupted by minor settling. <br />Gabions (wire-enclosed riprap) consist of stone placed <br />in wire baskets or wire-covered mats. Gabions are usu­ <br />ally utilized when rock of suitable size is not avail­ <br />able. There are two disadvantages in using gabions - <br />their unnatural appearance and the potential failure of <br />the wire enclosure. The use of gabions is discouraged <br />because of maintenance problems. When they are ”«ces- <br />sary# howeverr gabions should be confined primarily to <br />stream banks. <br />CONSTRUCTION <br />Riprap shore protection shall be <br />mum finished slope of 3:1. No slope or f^^^er materials <br />shall be placed more than 5 feet waterward of the OHW <br />(see Figure A-1). A severely eroding bank may require <br />filling in with a greater depth of natural rock before a <br />stable slope may be achieved. Gently sloping banks are <br />more stable for riprap and result in fewer failures. The <br />extent of riprap into the water should be minimized since <br />flow and wave action can cause stability problems. <br />A transitional layer of gravel, small stone, fabric <br />shall be placed between the fine material of an embank <br />ment and the riprap shore protection materials. The pur­ <br />poses of the filter are to: <br />1.Prevent fine embankment material from being <br />pulled through the riprap materials. <br />2.Distribute the weight of the overlying riprap to <br />prevent settlement. <br />3.TO provide relief to hydrostatic pressures inside <br />the embankment. <br />not, a 6" filter blanket is recommended.rnsmmss-m <br />successfully with riprap. Brands* used successfully m- <br />II flthirfflfiiiainerritftisaii