222 W MARINE VIEW DR 2016-01-01 MF Import

Comparison of City of Evereu Standard Detention Vault to Corrugated Metal Pipe Vault December 2, 1994 File No. 24-92-009-007-01 Page 7 The base equation is as follows from page 144 of the ASCE "Wastewate� Treatment Plant Design" (copy attached): V < t.:� cs-�)a V� is known,and the equation is rewritten �`� < (S-1)d �`, < (S-1)d �.�- v� i.;2a <S-1 S> 1�1 Zd+1 Vc —�� — 46 6tt2 'O21 fi � S d for silt is .002-.OS mm (Storm Water Management Table 7.3) Using .002 mm: � : S > 13;d+1=�6��0�+1=1.13 Attached is a copy of pages from "Foundation Engineering" by Peck, Hanson and Thornburn. As shown in Table 13 of "Foundation Engineering", most soil constituents have a specific gravity (3) in excess of 2.0. Since this is in excess of 1.13, they would not scour off the bottom of the CMP vault. When the soil particles come together to form a soil, they form void spaces, and overall specific gravity is not the same as the averages of the individual constituents. Table 1.4 shows the density for typical soils. Since the specif'ic gravity of the soil subject to scour is 1.13, its density would be 1.13 x 62.41bs/cf (density of water) = 70.5 lbs/cf. As shown in Table 1.4, most soils in the'v natura] state have a clensity in excess of 70.5 lbs/cf and as such would not be subject scour at the bottom �f the CMP vault. In conclusion, the proposed CMP pipe system provides equivalent presettling basin perfonnance and, in this specific case, is an acceptable alternative to the Standard Everett Design. Prepazed by ;fi Rob^*t 0. Galteland, P.E. vlt�wf�sterling�equas. rog