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vvistevdE-A ter System
<br /> the cinnnctor c\prusscd c(,neem lboill P,,lenti:lt l h aian,g of the sprat h(1lC'e in lhC LilSj)VLA] field 1;11 elclr,
<br /> Ther ad of pilinpirlL teats and limited 111specluons by the c,,Eiu.Ect,Er do not rule Out 11 Ill)('
<br /> tdica,I e ih.it plugging is nor idespread.
<br /> g
<br /> The loction of the cFqriLLlur.t1 bc�x fur Ole sec'mdar" dl"nLrqril s�-stcrri was visible, but Elie
<br /> I , -,t rhe
<br /> le
<br /> b,-
<br /> c'cl, I 1,�. and seepage pit-, vi-cry not ,lt)E-110U.1. There .very iu, kn,OVn lccels port, t,� the sc 1 tie pits, act ill,
<br /> M-11CL nils ril the seepage puG could not be dctertnine1
<br /> c a d i rC C2 R a IL e a '17V F Eta at 1 10 1
<br /> According to faictorl.management, the et-fluent flow rate has averaged qpproximareh- SOO gallons per day
<br /> (gpd), N;hiCh is Consistent with the design, specifications and the water balance by Nolte. The lwdrauLic
<br /> loading rate on the primar) (Infiltrators) dispersal field is well within the San (oaquirl County- .requirements,
<br /> with the primary dispersal field having been designed for 1,500 gpd average dad), flow by Chesney (2002).
<br /> The perinitted peak flow is 1,800 gpd. The design surface area in the Infiltrator chambers is 1,800 square
<br /> feet. Assuming the 800 gpd average flow is apphed only to the primary (Infiltrator) drainfield, the surface
<br /> application rate Nvould be 0.41 gallons per square foot per da) (gal/ft-/d). Using other authoritative
<br /> references (Table 13-9, Crites and Tchoballoglous, 1998), the' recommended application rates for the site
<br /> would be 0.45 gal/ft'-/d based on the double-ring infiltrometer test results and 0.6 gal/ft';d based on the
<br /> percolation test results. This would imply a hydraulic loading capacity of up to 1,090 based on the
<br /> I gpd bq
<br /> percolation test results. This is more than the current average flow but less than the design flow. Therefore,
<br /> the pririlary dispersal Field is adequately sized for the current average Cow based on both county standards
<br /> and values from other references. However, the effluent strength may be an overriding factor, as is discussed
<br /> below.
<br /> 3.2 BOD Loading Rates Evaluation
<br /> The etfluent strength has averaged roughly 1,000 mg/L BOD versus a projected value of 577 mg/L (Nolte,
<br /> 2003). If all of the effluent were to be applied to the p6mary dispersal field, the BOD loading rite would be
<br /> 160 pounds per acre per day Obs/ac/d). Even though the Infiltrator systems should have rclativcly good
<br /> oxygen availability, this rate is yen,high for an unmanaged system. A more appropriate rate would be
<br /> apprcuiirnaicly 40 lbs/ac/d. If the effluent strength is not reduced by additional treatment, the hydraulic
<br /> loading capacity should be reduced by a factor of four or more (Table 13-7, Crites and Tchobarloglous, 1998).
<br /> 3.3 Frolbable Causes of Infiltrator System Failur-e
<br /> The most probable cause of the failure of the Infiltrator system was I the conditions during construction. First,
<br /> construction during rainy or muddy conditions causes fine soil particles to float and then settle on tope the
<br /> Surface, creating what is known as a surface seal. The hydraulic conductivity, of the surface seal can bias little
<br /> as 10 percent or less of the hydraulic conductivity of well-structured, non-sealed soil- Second, the volume
<br /> and infiltrative surface areas of the Infiltrator chambers were apparently substantially reduced by settling. The
<br /> settling could have been aggravated by reported backEl compaction using a backhoe over tile Infiltrators.
<br /> The surface sealing and settling reduce both short term and long, term effluent dispersal capacities.
<br /> Phntoi;*zzphs of the Infiliratur st stem during construction are shown in Figures 1 and 2. These plim'sraplu;
<br /> shot- the muddy coridiu,,lls during installation that would h.rre caused soil surface scaling and tri;ide ray
<br /> IllfJJ_Lr2.t(,)fS susceptible to settling
<br /> The fact that the 'nfilLrattir system failed ��,itlrini dal=s after effluent as%,i o i indicates� fist directed t ridCes 1
<br /> t i
<br /> c"ILlenr strength war not the prim rry factor fat drainfitld failure. Failure iLIC to effluent UOU llln-c
<br /> recililred a dense blohqrJad inlu, ly-hiCh would have taken longer to duveh ip than a fed-dace. A s 11r1felil
<br /> 3
<br /> 1 F Rj:.
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