SU0006977 SSNL - Laserfiche WebLink

Home Browse Search

r��where: Q=average dailyflow in.ft3/day A —area of disposal field in ft'. C=mounding equation constant L= length of disposal field in ft K horizontal,permeability of sail in ft/day - n =mounding equation exponent ; Sy, specific yield of receiving,soilin percent t =time since the beginning of wastewater:application in days Substituting known constants for the variables,we find the following: Q =5,925 gals/wk-7 days/wk=846 gpd-7.48 gals/ft' 1 13 ft'/day A =2,562 ft'(Pg. 15) C=Length to width ratio .z 3:3;therefore,C= 1:1348 L=91.5 ft K=Using average vertical permeability as most conservative= min/in: 1440 min/day= 15 min/in=8 May h=40:25 (See above) n=Length to width ratio X3.3,therefore;n 13716 Sy= .05% t =3,650 days(10 yrs) Z,,, =0.050 x 256 x 0.0031 x 0.006=0.001 ft It appears that the.maximum mound height that may occur under disposal area is an insignificant 0.001 feet. This may be attributable to the large length-to-width ratio. For wastewater treatment to occur, the distance effluent should travel under unsaturated conditions through the soil environment is generally regarded to be 5 feet, which will be maintained, as calculated on the previous Page.' Additionally, the-Cali ornia_Siate`Water Resources Control Board- Guidelines for the Design, . Installation and Operations of Mound Sewage Disposal Sysleins document states in Section 3 1.0 that in cases where peak wastewater flows for a commercial system exceed 1,500 gallons per day, an evaluation of hydraulic mounding below the disposal area shall be performed. Although the daily flows will be substantially lower than this, mound potential analysis remains viable. In the Finnemore and Hantzsche paper, they discuss three options to consider as potential methods of reducing the.mounding phenomenon. The first is increasing the-size of the disposal field, Based upon the average daily flow calculations found on Page 13, the disposal area is.greater than sufficient size to accommodate the projected effluent flow volumes after Phase II completion. The second method is elongating the shape of the area,cover ed by the disposal field. As noted on the design plans, the disposal area is elongated in a 3.5:1 length-to-width ratio. Thirdly, operating -the field intermittently should decrease the mounding effect. Since the effluent disposal will be under:gravity flow, this is not applicable. Chesney Consulting'