Laserfiche WebLink
ticwunR for gyne small amoum of weep percoiaLion �rairuaii-r, i Lnrougn pervious areas of <br />the site as the onsite portion of the total annual recharge (call it RI). <br />b) For average year conditions (monthly time steps), estimate the amount (or percentage) of <br />building site runoff entering the basin that is expected to drain via percolation, as <br />opposed to being discharged to the regional storm drain system. If the basin is designed <br />for full retention/percolation of normal year rainfall -runoff, with off-site discharge only <br />during peak storms, it may be possible to consider all building site runoff as available for <br />percolation. <br />c) Estimate the direct rainfall volume (acre-feet) into the basin as part of the water available <br />for percolation. Since it appears the retention basin capacity is planned to be shared with <br />another development site (Buildings A&B), include only the portion of direct rainfall <br />approximating the percentage of the basin allocated for the project. <br />d) Combine the estimated monthly recharge volumes from (b) and (c), and subtract the <br />average amount of water lost to evapotranspiration (ET) from the surface of the retention <br />basin (monthly). For the a shared retention facility, adjust (i.e., reduce) the ET losses <br />consistent with the percentage of the basin allocated for the project. <br />e) The sum of (b) + (c) - (d) would give an estimate of the net monthly off-site retention <br />basin recharge volumes, and the annual total (call it R2). <br />f) The sum of Rr +72wou6d-give tie estunated annuaIram—fa-11 recharge, ?2, fol use— m tie <br />above mass balance equation. <br />A-2 <br />