HomeMy WebLinkAboutOWTS Report 04.19.2017Onsite Wastewater Treatment System Report
AspsN Varrsv Polo Crus
1641 1 Hrcuwav 82
CansoNDALE, CO
April19,2017
Prepared by
Roaring Fork Engineering
592 Highway 133
Carbondale,CO 81623
Onsite Wastewater Treatment System Report
AsppN Vallnv Poro CLus
164l I lhcuwav 82
CaneoNDALE, CO
THE PROPOSBO ONSTTB WASTEWATER TREATMENT SYSTEM (OWTS) FOR ASPEN VALLEY POLO
CLUB TN GenT.mIo CouNTy CoI-oRAoO HAS BEEN DESIGNED TO COMPLY WITH THE MOST
CURRENT (JuNr 2014) EDrrroN oF THE GARFTELD CouNrv OWTS UsE PERMTT Rr,cuLATroNS.
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Table of Contents
Table of Contents..........
1.0 ExistingConditions
1.1 General.............
1.2 Soil Conditions.
2.0 OWTSOverview......
2.1 North Septic Field.
2.1.2 Septic Tank Sizing....
2.1.3 Soil Treatment Area Sizing.
2.1 .4 Setbacks
2. 1.5 Distribution and Dosing........
2.l.6Head Loss.......
2.1.7 Pump Selection ...
3.0 Maintenance
Appendix A: Completed OWTS Permit and Construction Permit Application Checklist.
Appendix B: Geotechnical Report and Profile Pits..............
Appendix C: Design Flows and STA Sizing
Appendix D: Dosing Volumes.....
Appendix E: Pump Curves........
Appendix F: Product Information
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1.0 ExistÍng Conditions
1.1" General
The property address is 16411 Highway 82, Carbondale Colorado. The parcel number is239131100033.
The property is owned by Aspen Polo Partners LLP. The proposed development is located south of
Highway 82, north of the Roaring Fork River and about0.62 miles east of Catherine Store Rd. The
property is accessed off of the Highway 82 Frontage Rd. which connects to Catherine Store Rd. The legal
description of the property is Section: 31, Township: 7, Range: 87 atrack of land in lots 8,9 &,10 of sec
31 and lots 5 &13 in sec 32 in Garfield County, Colorado. The parcel is a total of 100.44 acres.
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The development is currently proposing two regular sized polo fields, five barns with ADUs, a clubhouse
and four small cabins. Three separate Onsite Vy'astewater Treatment Systems (OTWS) will be used to
treat the wastewater from the sources. This report pertains to one of those three systems from now on
referred to as the North Septic System.
7.2 Soil Conditions
In 2008, a Geotechnical report was produced by HP Geotech. This site was deemed to be in the western
Colorado evaporite region within the Carbondale collapse center. The report indicates that this creates a
long term settling or subsidence rate between 0.5 and 1.6 inches every 100 years, which should not have
significant impact on the development.
HP Geotech also delineated 7 different river terraces across the site stepping down to the Roaring Fork
River. All of the development for Zone I will take place on the upper tenace out of the wetlands. The
delineation of the terraces can be seen within the attached Geotech report.
The soil profile pits determined by field exploration conducted on January 10, 2008 shows 0.5 to 3 feet of
topsoil overlaying 2 feet ofsilty sand in Pit I and relatively dense, silty sandy gravel containing cobbles
and boulders in the remaining pits. This is said to be alluvial deposits. Logs of these exploratory pits and
their locations can be found within the Geotech Report. 12 pits where dug with an excavator with most
depths ranging between 8 and 10 feet deep. The report also states thatjudging from Colorado State
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Engineer's well records this river alluvium consists of rounded gravel-to boulder size rocks in a relatively
clean matrix extending to clepths of 40 to 50 feet.
Roaring Fork Engineering also excavatcd six profile pits on September 12,2017. Thc six holcs wcrc dug
within the proposed locations of the three septic tìelds. Two profile pits per tìeld. The excavations yielded
similar results as the geotechnical investigation by IIP Ceotech, with top soil overlaying alluvial glacial
silty sandy gravels and cobbles. Profile exhibits can be found in the appendix. This investigation
combined with the gradation test from the 2008 HP Geotech report indicates that the alluvial layer below
the top soil is Soil Type 1.
Free water was encountered on the north side of the property, which appears to be coming from the flood
irrigation of the hay field just north of the Highway. The ground water was 24 inches below grade at its
highest level during observation. This was only observed at the location of the proposed northern soil
treatment area. The North Septic System containing the northem soil treatment area will be a mounded
bed system to provided adequate clearance above the ground water. Groundwater was not found in the
other profile pits which were excavated down to depths of 8 feet.
2.0 O\ryTS Overview
The septic system will be designed in accordance with the Colorado Department of Public Health and
Environment's (CDPHE) Regulation 43 and Garfield County regulations. A Colorado Department of
Public Health and Environment (CDPHE) permit is not required for this size of system.
The waste water design flows were calculated using section 43.6 of the Garfield County On-site
Wastewater Treatment System Regulations. The design flow used per person is 75 gallons per day in
accordance with Section 43.6.The assumed number of persons per bedroom is two for design purposes.
Additional flows were taken into account for additional fixtures in the bams and clubhouse. These daily
flows where used along with Section 43.7 ta determine the minimt¡m clistances between components of
the OWTS and physical feature such as ponds and wells.
Septic tanks will be used to bring the effluent to Treatment Level I (TLl). The minimum septic tank size
was determined using section 43.9-Bl-aDesign Criteria and Components, Septic Tanks, Sizing
Requirements, Table 9-l within the Garfield County On-site Wastewater Treatment System Regulations.
The required soil treatment area (STA) was determined by section 43.10 of the Garfield County On-site
Wastewater Treatment System Regulations.
The dosing volume for each field is based on the industry standard dosing volume of seven times the
piping volume of the STA receiving the effluent.
The Orenco pump selection software was used to calculate the total dynamic head loss within the system
This information was then used to specify an adequate pump.
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2.1 North septic Field
2.1.1 Des^ign flow
The North Septic System treats the wastewater flom the Maintenance Barn and Horse Barns 3, 4, and 5.
The Maintenance Barn has two rtwelling units, with two bedrooms each, totaling four bedrooms. The
Horse Barns will have one dwelling unit with two bedrooms per barn. The total number of bedrooms for
this system will be ten (10).
- l0 Bedrooms x 2 people x 75 gallons per day : 1,500 gallons per day
The Maintenance Bam and Horse Barns will have extra bathrooms/lavatories for employees. The Horse
Barns were estimated to have five people using the bathroom three times a day. The Maintenance Bam
was estimated to have eight people using the bathroom three times a day. The water use per bathroom
visit is 2 gallons based on fixture flows. The additional bathrooms do not include showers, only toilets
and sinks.
- Maintenance Bam: 8 people x 3 uses x 2 gallons =48 gallons per day
- Horse Bam: 5 people x 3 uses x 2 gallons = 30 gallons per day
- 3 Horse Barns * 1 Maintenance Bam = 138 gallons per day
Total flows = 138 gallon per day + 1,500 gallons per day : 1,638 gallons per day I r_
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For ten bedrooms, the minimum tank size is2,750 gallons. One single chamber 2,000-gallon tank will be
connected to another 1,000-gallon two compartment tank. This septic tank will bring the effluent to
Treatment Level 1 (TLl) before it is pumped to the STA.
2.1.3 Soil'Ireatment Area Sizing
Due to the high ground water observed in the north field test pits, the STA for north system will be a
pressure dosed sand mound, in a bed contìguration, with low profile Quick 4 infiltrators. This area has
approximately
removed. Then
12 inches of top soil overlaying the natural Type 1 soil. This top soil layer will be
layer of sand, meeting ASTM 33, will be added. The infiltrators will sit on top of
the sand and be with a minimum of 10 inches of onsite material. The final layer will be topsoil.
With the implementation of the 2-foot layer of sand an LTAR of 1.0 shall be used.
Using the design flow of 1,638 gallons per day and the LTAR of 1.0 gallons per day per square foot, it
was determined that the minimum STA is 1,147 square feet. This area calculation takes into account the
reduction factors applied for the application of low profile Quick 4 infiltrator chambers (0.7
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uù lrlf4tQuick 4 Plus infìltrators will be used They will be configured in a bed formation of four
24.This does not exceed the maximum width of 12 feet
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According to GarfÌeld County regulations. The north STA must
well. The onsite well is942feet from the north STA. The STA must also not be within 100 feet of any
ponds. The nearest lined pond is 230 feet away.
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2.1.5 Di.stribution and Dosing
The north STA will be pressure dosed. The second chamber of the 1,O00-gallon tank will house the
Orenco pump and float tree. The pump will discharge into a pressurized two-inch PVC distribution pipe
leading to the Alternating Distribr¡tion Valve (ADV). The distribution line contains 21 gallons. This line
is sloped back toward the tank so the effluent will drain back into the pump basin when the pump shuts
off and the air release valve opens. This is done to prevent freezing and stagnant fluid sitting in the line.
The ADV is at the high point in the line and will alternate flow between the two zones which allows one
half of the field to rest while the other half is being dosed.
From the ADV the flow will pass though the 1.5-inch PVC manifold connected to the laterals. This
manifold has a volume of approximately three gallons. The laterals are also 1.5-inch diameter PVC that
are suspended within the chambers. Each lateral has 24 chambers and is 96 feet long. There are 2 laterals
per zone with a volume of approximaTely 20 gallons. This bring the total piping volume after the ADV to
approximately 23 gallons.
A dosing volume was determined by using the industry standard of seven times the lateral piping volumes
of one zone, plus any drain back. Each zone has two laterals with a volume of 20 gallons while the
distribution line has a volume of 21 gallons. Therefore, each zone should be dosed at approximately 163
gallons. The elevations of the floats in the dosing chamber have been set to meet this dosing volume. See
the appendix for dosing calculations and OWTS drawings.
2.1.6 Head Loss
The Orenco pump selection software was used to determine the total head loss for the system. Using the
distribution pipe material, size and length, orifìce size and spacing, bends, the ADV model, the max
elevation lift, the manifold and the lateral piping configurations, a system curve was created. From this,
the minimum pumping requirements were determined. A system curve is provided in the appendix.
2.1.7 Pttrnp Selection
The pu¡rp selected for the north systcm is thc Orenco PFEF-SO-B. Â pump curve, along with product
information, can be found within the appendix.
3.0 Maintenance
The Owner will follow the operation and maintenance required in Section 43.14 of the Garfield County
On-site Wastewater Treatment System regulations. This section can be found in the appendix. Below is a
maintenance schedule for each OWTS.
Cleanin F ue
Gleaned or PumpedInspection/MaintenanceType of Component
Every 2 Years, or As
Needed
Every 2 YearsSeptic Tanks
Every 6 Months N.A-Absorption Areas
Every 4
Years
Every 6 MonthsDosing or Pumping Chambers
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