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� <br />i; <br />282 WEf•REfENTION/DEfENT10NPpNDS <br />SOLUTION: Since the pond has a control invert above the bottom (� <br />rather than dry) removal will occur both during runoff and quiescent ��d�, <br />tions. Average overflow rate is calculated using equation 8.15. <br />OR — Q <br />A, <br />(8.15) <br />0.086 in./h <br />— 1260 ft� x 0.50 x 5 acres x 43,560 fr'/acre x 1 ft/12 in, <br />— 0.62 ft/h <br />snd average voiume of rvnoff as <br />43,560 <br />VR @ PC(atea) <br />12 ) <br />—0.53x0.50x5x3630 <br />a 4810 k� <br />Assume that the variability of runoff is the same as the correspondin� <br />rainfall variability and rainfall excess is the same as rainfall volume: <br />C�,Q = 1.31 and C�R = 1.44 <br />where C�Q a coefficient of variability of runoff rate <br />C�R � coefficient of variability on rainfall excess (volume) <br />During RunofjCondirions: Using equation 8.10 gives <br />RM — 1 — e'a•:ioR> <br />and R� from Figure 8.5, or as shown in the following table (z =].0). <br />Avenae SetAina (u,) Percent of RN (%) Ri (%) <br />Velociry (ft/h) Time (Equation 8.10) (Figure 8.5) <br />0.03 20 5 5 <br />0.33 20 41 20 <br />1.5 20 91 77 <br />7.0 20 1pp 1pp <br />70 20 100 100 <br />Overall average removal = 60°!0 =�S e <br />Fp or percentage not removed = 40% <br />8.2 MODEUNG C <br />During Quiescent Conditions: (N <br />31�•d during the storm event, thus d <br />pond vo <br />runoff v< <br />VB < <br />VR�4 <br />an <br />Ea � • <br />� 22.28 <br />pvenQe Settling (u,) Percent o[ <br />Velaity(ft/h) Time <br />0.03 25 <br />0.33 25 <br />i.so u <br />�.o u <br />�o 0 <br />Overal► average romrnal � : <br />fQ or percentage not removed —� <br />Overall percent removal s <br />e: During quiesant conditions, <br />off conditions. This is because so� <br />quiescent settling or are remrnec <br />Fate ot Pollutants <br />ient and metal interactions w: <br />s have not been fully investigat� <br />able to describe the interaction, <br />apply to stormwater wet•deter <br />se rates from bottom sediments, <br />are constructed and submerged <br />�ents of wet-detention ponds in <br />�). The eaterior of the chaml <br />