HomeMy WebLinkAboutEngineer's OWTS Design Report57 Garden Circle, Garfield County Colorado October 27,2023
Onsite Wastewater Treatment System Report
57 GannEN CIRcLE
Lor 4 GnpAD GARDENS
GanrtELD CorrNrY, CO
October 30,2023
Prepared by
Daniel Stewart, P.E.
Roaring Fork Engineering
592 Highway 133
Carbondale, CO 8162
IOWTS Report
57 Garden Circle Garfield County, Colorado
Table of Contents
Table of Contents.......,..........
1.0 ExistingConditions...
1.1 General......
1.2 SoilConditions.......
2.0 OWTS Overview
2.1 Design Flow
2.2 Septic Tank Sizing
2.3 Soil Treatment Area Sizing-."'.
2.4 Setbacks
3.0 Maintenance
Appendix A: Design Flows and STA Sizing.'...
October 27,2023
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4
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1OWTS Report
57 Garden Circle Garfield County, Colorado October 27 ,2023
I.0 Existing Conditions
l.l General
The Project is located at 57 Garden Circle in the Gilead Gardens Subdivision in Garfield County,
Colorado. The site is an undeveloped lot and requires a building permit to build a 3-bedroom, single-
family home. The property is serviced by a public water system at the southern end of the property.
Existing electric and telephone services run in the access & utility easement in the cul-de-sac. A
telephone pedestal exists, and an electric transformer is on the western side of the site in the cul-de-sac.
The site generally slopes south to north at a 6:1 + grade. An existing irrigation ditch runs along the north
side of the property.
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1.2 Soil Conditions
Two profile pits were excavated on October 21,2023, and observed by Roaring Fork Engineering. The
pits generally consisted of about 4 to 6 inches of topsoil, and then from there down, clayey silty and
slightly moist soil to a depth of 8 feet. No free water was encountered during excavation. The two pits
were of the same composition. A photo of the typical profile is shown below.
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2OWTS Report
57 Garden Circle Garfield County, Colorado October 27,2023
Typical OWTS Profile Pit
Soil samples of the native material were taken from both soil profile pits, so gradation testing could be
performed. The soil passing the No. 10 sieve was tested according to the USDA NRCS Guide to Texture
by Feel. The results showed the soil was a siþ clay (Type 4) since it remained in a ball when squeezed
and formed more than a 2" ribbon while feeling slightly gritty. Given this soil type and an effluent
treatment Level of 1, Table 10-1 of regulation43 On-Site Wastewater Treatment System Regulations
indicates the LTAR (Long Term Acceptance Rate) shall be 0.2 gallons per day per square foot' No
secondary treatment is being proposed as all setbacks in Table 7-l are met with the proposed design.
2.0 O\MTS Overview
The septic system will be designed in accordance with the Colorado Department of Public Health and
Environment's (CDPHE) Regulation 43 andGarfield County regulations. A Colorado Department of
public Health and Environment (CDPIIE) permit is not required for a system of this size.
The wastewater design flows were calculated using section43.6 of Regulation 43 On-site Wastewater
Treatment System Regulations. The design flow used per person is 75 gallons per day. The assumed
number of persons per bed is two for design purposes. These daily flows were used along with Section
43.7 to determine the minimum distances between components of the OWTS and the proposed well and
pond.
Septic t¿nks will be used to bring the effluent to Treatment Level I (TLl). The minimum septic tank size
will be 1,000 gallons as required by Section 43.9-82-of the OWTS Regulations'
3OWTS Repoft
57 Garden Circle Garfield County, Colorado October 27,2023
The required soil treatment area (STA) was determined by section 43.10 of the on-site'wastewater
Treatment System Regulations.
2.1 Design Flow
The septic field will treat wastewater from the main residence. Pitkin County regulations require the
design flow to include two people per bed with each person generating 75 gallons per day'
- 3 beds x 2 people x 75 gallons per day :450 gallons per day
2.2 Septic Tank Sizing
For 3 beds, the minimum tank size according to the regulations is 1,000 gallons. one single compartment
tank will be used.
This septic tank will bring the effluent to Treatment Level 1 (TLl) before it is gravity fed to the soil
treatment area.
2.3 Soil Treatrnent Area Sizing
using the design flow of 450 gallons per day and the LTAR of 0.2 gallons per day per square foot, it was
determined that the minimum srA is 1,575 square feet for bed configurations. A 0.7 reduction factor has
also been applied as chamber beds shall be utilized'
132 euick 4 Infiltrators will be arranged in 6 rows. Each row will have 22 infiltrators each. The rows will
be spaced a minimum of four feetapart'
2.4 Setbacks
According to Table 7-1 of the owrs Regulations the soil treatment area must be a minimum of 10 feet
away from properfy lines and 50 feet from irrigation ditches. The STA has been positioned to meet these
setbacks. The septic tank and seweÏ lines also meet the required setbacks'
3.0 Maintenance
The owner will follow the operation and maintenance required in section 43.14 of the Pitkin County on-
site Wastewater Treatment System Regulations. Below is a maintenance schedule for the OWTS'
and
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Type of ComPonent lnspection/Maintenance Cleaned or PumPed
Tanks Every 2 Years Every 2 Years, or As
Needed
Absorption Areas Every 6 Months N.A.
OWTS RePort
57 Garden Circle Garfield County, Colorado October 27,2023
Appendix A: Design Flows and STA Sizing
always be "1" regardless of Treatment Level. Remember that HLT systems are always pressure-dosed, so no
LTAF
Treatmentthe ofLevel effluent.thetheonSo¡l andTypeSo¡lfor the TAR0,Type mayvaryExcept
the"o'Treatment forbul So¡lTARSoilfor1.-5 different Levels,TypetheTypesbychoosingadjustmay
reductions are for Manufactured or Chamber distr¡bution for HLT
DISCLAIMER: the OWTS Regulåtions mây l¡mit siz¡ng options based on types
methods, treatment levels, etc. Not all of the sizing opt¡ons shown in the calculated tables w¡ll appl\
These cãlculations must be ver¡fied by the design en8¡neerto every system.
of sys¡ems, effluent appl¡€at¡on
45{'
9m
o.2
I
Enter Des¡gn Flow (gpdl
M¡nimum Tank
Select LTAR
House size ¡n sq
Enter Number of Bedrooms {lncluding office(sl, ADU,
Flow Per
Enter Add¡t¡onal Flow ¡n
see D¡sttbut¡on Medìa Tøbs below lot des¡gn detoÍts
Select Effluent Àpplication
2o{ro
3
75
0
rS(xlTRENCH STA
2250BED STA
FoR HLT SYSTEM5 w /DIST. MEDIA
rdun to ÍABc¿rcrl HERE towGRAVET
22SOTRENCH STA
2700BED STA
m25TRENCH 5TA
?J3oBED STA
CLICKFOR TT1 W / MANUFACTURED DIST. MËDIA to go to / return to th¡s TAB
retufa to fABCLICKHEREwCHAMBER
157sTRENCH STA
1890BED STA
CHAMBER DISlR¡BUTION MEDIA WORKSHEET
toTAB 1 ând make
and anyof those parameters,
¡nfo.
are bâsed onmìnimum
tNsrRucnoNs:tables at let thôt vÞe
wastemteÍ TL and from thedrop down llst lnthe YElIow box belqw:
MINIMUM REQUIRED f{UMBEß OF U'{Ifs ARÊ SHOWN IN TABLES BELOW - FOR EQUAT EFFLUENT DISTRIBUTION THE NUMBER OF CHAMBERS IN EACH BED ROW ORTREI{CH MUST 8E
EquAL WHTCH MAy REqUtRÊ MORE CHAMEERS ÌHAN SHOWN 8ELOW. DISTRIBUIION LINES ARE REQUIRED WlTHlf{ fHE CHAMBERS'
Tronch System
area (ff)Wldth of Lôngth of
Syetom (lt) Systom (ft)
524
244
176
132
108
88
7ø
68
60
56
48
44
44
10
Length of
Syatsm + End
Caps (lt)
531
2ø7
179
135
111
79
71
63
59
47
47
43
Longth ot
Systom + E¡d
Cãp8 (ft)
53'l
267
179
135
1'l'l
91
79
71
63
5'l
47
47
43
39
39
35
35
31
31
31
27
27
27
Total
lnfflhtoß
Er€vel¡on Totâl AEa
of Syalom
É)
1584
2640
2992
3168
3348
3?44
3420
3536
3540
3696
3504
3520
3828
3760
132
66
44
33
22
19
17
15
14
12
11
1'l
l0
132
66
44
33
27
22
19
'17
15
14
12
't1
11
10
I
8
I
7
7
7
6
6
6
lnñltratoB
132
't32
.132
132
135
132
133
136
135
't 40
132
,t32
143
140
Total
132
132
132
132
135
132
139
135
't40
132
132
143
140
144
136
144
'133
140
147
132
138
144
3
10
17
24
38
45
52
59
66
73
80
a7
94
'1592
1592
1592
1592
1628
1592
1604
1640
1428
1688
1592
1592
1724
1688
Eod Systêm
Wdth of Longth of
SystÞm(ft) Systom(ñ)
3 524
6 2@l
9 176
't2 '132
'15 108
r8 88
21 76
24 68
27 60
30 56
33 48
36 44
39 44
42 40
45 36
4A 36
59 32
63 32
66 2A
70 28
73 2A
77 24
80 24
u24
Erøvat¡on
Area (fÉ)
1592
1600
1608
1616
1660
1632
1652
1696
1492
1760
1672
'1680
1A20
1792
1740
1B56
2024
2144
2000
2106
22'12
2012
2104
21gts
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2
3
4
5
6
7
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I
l0
1',l
12
13
14
t5
l6
17
l8
t9
20
21
22
23
21
1S75ÌRENCH SfA
tE90BED STA
Arc 18 (18" wídettench)l 225
Arc 24 (24" w¡detrench)| L1t
Arc361 llt
Atc36HCl ¡05
Arc 36 LP | 11.:l
R€SERVÊDI
RESERVEDI
RESERVÊDI
Quick 4 Plus Stqndord 131
t3lQu¡ck 4
4 Plus
RESERVED
RESÊRVED
RESERVED
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