Laserfiche WebLink
<br />aD?~,,"6 <br /> <br />TABLE IV-6 <br /> <br />F-<n'IMATED AvER.z\GE AmlIAI. IDl'F.NrIAL <br />ON-SITE AliI) l1FF'-SITE !nIT. TfiCt~ <br />1<<LF ~~ VAT.T.RY' <br /> <br />Estimated <br />On-Site Inrpacts <br /> <br />Units: Tons/Ac. <br />Estimated <br />Off-Site Impacts <br /> <br /> Potential <br /> Soil Topo- Soil with Delivery Intro- <br /> Rainfall Erodibility graphic Loss Reveg. Coeff. duced <br />Source Factor Factor Factor Sed i- <br /> (R) (K) (LS) (A) (A) (WI) (0) ment <br />(l) (2) (3) (4) (5) (6) (7) (8) <br /> <br />Up] and <br />(Sk:i Trails, <br />etc.) 53 <br />~ 53 <br /> <br />0.2 <br />0.2 <br /> <br />12.7 <br />15.1 <br /> <br />134.6 13.46 <br />160.1 16.01 <br /> <br />0.013 <br />0.10 <br /> <br />0.17 <br />1.60 <br /> <br />Tables IV-7 and IV-8 present a sediment yield analysis of the <br />study watersheds for each of the alternatives. These tables <br />include the urban runoff sediment frem private lands (Table <br />IV-5), and sediment increases associated with snowrnaking <br />water runoff (about one ton/year). The introduced component <br />accounts for the bulk: of the increased sediment yield in all <br />cases. The estimated 58 mg/l increase on BootjaCk: Creek is <br />near the allowable maximum. Accordingly, care should be <br />exercised, given the proposed level of developnent on the <br />watersheds, to hold introduced sediment at levels which <br />maintain stream channel integrity. <br /> <br />Developnent of the watersheds will not occur simultaneously. <br />Because seme 20 years will be required to complete the <br />project, time itself will mitigate much of the impact as far <br />as the West Fork: is concerned. <br /> <br />Considering phased deve1opnent, the effect of the introduced <br />sediment conp:>nent was assLmled to be diminished in subsequmt <br />years after initial disturbance as follows, <br /> <br />Year <br />After Initial <br />Disturbance <br />I <br />2 <br />3 <br />4 <br />5+ <br /> <br />Residual Impact Factor <br />For Introduced <br />Sediment Comoonent <br />1.00 <br />.85 <br />.77 <br />.55 <br />.25 <br /> <br />175 <br />