500 LAUREL DR 2016-01-01 MF Import

Geotechnical Engineering Study Page 35 - 00-2267 Three Story Addition - 500 Laurel SUE:' '�vere� _ January 31, 2001 risk. As a minimum measure we recommend that the eaRhwork contractor erect _ a silt fence along the downgrade perimeters of the construction ?rea of the site, and one between the construction area and ihe crest of the westem bluff slope. � ThEse fences should be set sufFiciently far from the edge of any excavation to allow — for free passage for the workmen. � The silt fence should consist of a geotextile fabric produced for this purpose and suitable for erosion control, s�ch as a Mirafi Envirofence or an equivalant approved in writing by tha geoi;:chnical engineer. It should be supported on "Hog Wire" attached to steel or woc den stakes driven into the ,o,round at reiatively close center to center spacings. Approximately the bottom tv:elve (12) inches of the geotextile should be buried into the site subgrade to halp avoid the risk of sediment laden water flo�ving out beneath the fence. A iypical pi„torial depiction of this filter fence is piesented on Plate 3, attached. JVhere the site excavation process exposes the native soils they :vill be subject to all ef the erosive forces of the elements, such as wind, rain, freeze, thaw and dryin� (by the sun). As a result they should be expected to deteriorate rapidly if not adequately protected. To protect these surface on a temporary basis we recommend these exposed areas ";e covered with a tarpaulin or plastic sheeting. In the longer teRn we recommend that a!I such areas be revegetated as quickly after construction as possible. We recommend that you seek input from your landscape architect regarding the most approp:7ate seed mixture. V•/e also presume that the seed will be placed and protected with some form of mulch, presumably by "hydmseeding". Dependinc� on the time of year when such revegetation occurs it mi�ht aiso be helpful to use an erosion control blanket to help keep the seed and mulch in-place until the root mat has an opportunity to germinate and take hold. In this case we recommend !he use of a North American Green C-125 Emsion Control Blanket, or an equivalent approved in writing by the geotechnicai engineer. This blanket not only helps keep the seed and mulch in-place Cut also provides a protective thermal blanket over the seed and mulch mixture. According to the manufacturer, this blanket also reduces the water flow velocity by up io 77%, and reduces the s�il loss by up to about 98%. These values are dependant on the blanket being installed in strict adherence with the manufacture�s specifications. ry