HomeMy WebLinkAboutOWTS Design Packet 06.12.2020Design Calculations
For
Schwaller Residence
On-site Wastewater Treatment System
TBD Old Ranch Road
Rifle, Colorado
June 12, 2020
CIVCO Engineering Inc
Civil Engineering Consultants
Vernal, Utah
1256 W. 400 S. Office: 435-789-5448
P.O. Box 1758 Fax: 435-789-4485
Vernal, UT 84078 www.civcoengineering.com
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CIVCO Engineering, Inc.
PO Box 1758, Vernal, UT, 84078
Ph: (435)789-5448
Fx: (435)789-4485
SCHWALLER RESIDENCE
TBD Old Ranch Road
Rifle, Colorado
Referenced Calculations
Description
OWTS SIZING Page 1
By: WK Date: 06/09/2020
Chk'd: vvk Date: 06/12/2020
Section contains calculations sizing the components of the On-site Wastewater Treatment
System.
Design Standards
Garfield County Resolution 2018-36 GCR
Site Investigation
Friday, May 8, 2020, a backhoe excavator was used to dig two 8 -foot deep profile holes near
the proposed location of the Schwaller on-site wastewater treatment system (OWTS) soil
treatment area. Soil encountered in both holes included 6" to 8" of top soil with vegetation
overlying fine tan silty soil with some clay.
Standing water was first measured at 4' below ground surface at the beginning of perkolation
testing. The level dropped to 5', and then raised to 2' below ground surface all within the
perkolation testing period.
Percolation test locations were also prepared and presoaked on Friday May 8, 2020.
Percolation test holes were 10" in diameter and 12" deep below the presumed infiltrative
surface at just below top soil. Percolation tests were perfomed on Saturday May 9, 2020.
The percolation test data is tabulated on Sheet 2 of this document.
According to Google Earth data, the property slopes north to south at approximately 2.8% in
the vicinity of the proposed OWTS.
OWTS SIZING (ROCK).mcdx
CIVCO Engineering, Inc.
PO Box 1758, Vernal, UT, 84078
Ph: (435)789-5448
Fx: (435)789-4485
SCHWALLER RESIDENCE
TBD Old Ranch Road
Rifle, Colorado
Number of Bedrooms Nbed•= 3
Perk Test Results:
OWTS SIZING Page 2
By: WK Date: 06/09/2020
Chk'd: vvk Date: 06/12/2020
Minutes
Elapsed
Test Hole 1
Test Hale 2
Test Hole 3
Water
Level Drop
(in.)
Perk Rate
(Min./In.)
Water
Level Drop
(in.)
Perk Rae
(Min,/ n.)
Water
Level Drop
(in.)
Perk Rate
(Min On.)
30.00
2.875
10.43
1.625
18.46
2.375
12.63
60.00
1.125
26.67
1.125
26.67
1.125
26.67
90.00
1.125
26.67
0.875
34.29
1
30.00
120.00
0.75
40.00
1
30.00
0.75
40.00
150.00
2.625
11.43
1.875
16.00
2.375
12.63
180.00
1.25
24.00
1.75
17.14
1
30.00
210.00
1
30.00
1
30.00
1
30.00
240.00
1
30.00
0.875
34.29
0.75
40.00
Hole Perk Rae: 30.00 34.29 40.00
Ave. Perk Rae: 34.76
SEPTIC TANK
Required Tank Volume
Vtank:=
if Nbed< 3
(I 000 • ga/�
= 1 000 gal
else
(1 000 •gal+ (Nbed- 3) • 250.gal)
[GCR TABLE 9-1]
First Compartment Volume V,St comp:= tank = 500 gal
2
SOIL TREATMENT AREA
Design Flow C1:=
OWTS SIZING (ROCK).mcdx
if Nbed < 2
300
gal
day
else if Nbed = 3
=450 gal
day
[GCR 43.9.6.4.a]
[GCR Table 6-1]
450 gal
day
else if Nbed> 3
450 gal + (Nbed- 3) 75
day
gal
day
CIVCO Engineering, Inc.
PO Box 1758, Vernal, UT, 84078
Ph: (435)789-5448
Fx: (435)789-4485
SCHWALLER RESIDENCE
TBD Old Ranch Road
Rifle, Colorado
Long-term Acceptance Rate (LTAR)
OWTS SIZING Page 3
By: WK Date: 06/09/2020
Chk'd: vvk Date: 06/12/2020
gal
Perk Rate t:= taye- 34.76 min Type 2A soil.... LTAR:= 0.5 day
-
ft2
[GCR Table 10-1]
in
Unfactored Soil Treatment Area STA.— Q — 900 ft2
LTAR
Soil Treatment Area (Factored for Bedded Rock)...
[GCR 43.10.C.4]
Application Method Size Adjustment Factor.... SAFAM:= 1 .2 (gravity)
[GCR Table 10-2]
Distrib. Media Size Adjustment Factor SAFoM:= 1 .0 (rock or tire chips)
[GCR Table 10-3]
Cumulative Size Adjustment Factor.... SAF:= SAFAM• SAFoM= 1 .2
Bedded Rock Soil Treatment Area STABR:= SAF• STA= 1080 ft2 [GCR 43.10.C.4]
Bed Width 55.— 1 2 ft [GCR 43.10.F.2]
Required Bed Length LTR:= STAeR 90 ft
Be
STA: Two 45' -long by 12' -wide gravel beds.
OWTS SIZING (ROCK).mcdx