HomeMy WebLinkAboutAs-Built OWTS Design 08.02.17August 2,2017
Dave & Judy Douglas
160 River Ridge Dr
Glenwood Springs, CO 81621
riverbum@sopris.net
RE AS-BUILT, On-site Wastewater Treatment System (OV/TS), Douglass Residence, 160 River Ridge
Dr, Lot 5 River Ridge Pud Lot: 5, Garfield County, CO
SE Job No. 15147.01, Parcel No: 2185-354-04-001.
Dear Dave & Judy:
pursuant to County requirements, this letter provides documentation that the new Onsite Wastewater
Treatment Systern(OWTS) recently installed at the above referenced site is in compliance with the
permitted design. Sopris Engineering inspected the excavations, soils, materials and the installation of the
system components aivarious times during construction, prior to final backfill and after all installations
*"r" ,o-ptàte¿. The system constructed on site was designed and built to serve the needs of the single
family residential structure located at 160 River Ridge Dr,. The installed residential system was designed
for a maximum 4-bedroom residence. Sopris Engineering performed several visits to inspect the as built
conditions of the constructed system. We have coordinated our efforts with the earthmoving contractor
that constructed the system. TLe as built conclitions and installation of the new OWTS components is in
compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil
design plans, cl-owTS andC2OWTS Details, datedT-17-2015, by Sopris Engineering. The design criteria and
systãmsizing information is summarized below. The As-built OWTS treatment bed has been constructed
in the locations shown on the attached As-Built Record Drawing pursuant to survey field work.
Desisn and As-tluilt Svstem Co t Installation and Sizins
The system was designed based on the design criteria approved for use of pressure dose sand filters (SF) systems.
The OWTS includes íhe installation of a 2,000 gallon 3-compartment septic tank with a total of 1500 gallon septic
capacity in the primary and secondary tank chambers. The third tank chamber serves as a dosing tank with a
simplex efflueft pump assembly installed with an orenco Bio tube vault. The efÍluent is equally pressure
distributed across the treatmentTabsorption SF field via individual custom perforated distribution pipes connected at
the head of each SF row distribution row. A Gravity sewer pipe with two-way cleanout has been installed from the
house to the tank.
Design Calculations OWTS
Installation of an OWTS with a minimum S-bedroom capacity'
From the newly effective State Regulation 43:
Minimum population based on 5 bedrooms: 8 persons.
First 3 bedrooms (2 persons/bedroom) Over 3 bedrooms (1 person per bedroom)
Gallons per day per person :75 gallpetson/day, No peaking factor
Max. Deìign flow (ed)gallons lday : (# of people) x (avg. flow)gallperson/day.
Design flow Qd: 8*75:600 gPd
502 Main Street Suite A3 a Carbondale, C0 81623 a (e70 704-031 1 a Fax (970 704-031 3
$oPRIs tttcmttnIllc o llG civil consultants
AS-BUILT, OWTS
Dave & Judy Douglas
160 River Ridge Dr
SE Job No. 15147.01
August 2,2017
Page2
Septic Tank Design: Use a 1500 gallon, three compartment septic tank with a bio-tube dosing assembly in the third
chamber. Total tank capacity is 2000 gallons.
Sub Surface Conditions and Testins
Subsurface soil investigations and USDA soil texture method tests were performed by Sopris Engineering. The soils
in the area of the proposed absorption f,reld were sampled and characterized by application of the USDA soil texture
method test. The soils were tested to determine the hydraulic loading rate and to confirm the appropriate absorptive
surface level suitable for an intermittent sand frlter treatment system in native soils. The soils below nil to 3 inches
of topsoil consist of medium dense gravelly loamy sand to sandy loam material to 0.3 to 6 feet below the surface'
The soil appears to be consistent across the site.
The native soils sampled from 2-3 feet below the surface are characterized as a soil type 1 consisting of loamy sand
to sandy loam texture with moderate granular structure. This soil has an effective loading rate for conventional soil
treatment of 0.0.8 Gal/S.F./day for a level 1 conventional treatment system. Due to limited area and to provide
optimal treatment an intermittent sand filter is recommended. No free water was encountered in excavations on
site. Groundwater levels are expected to be below 10 feet from the existing surface grades.
The soils are suitable for the installation of the sand fîlter treatment bed system that will be fully pressure dosed..
An additional soil evaluation will be performed during construction to verifo the soils in the proposed field
excavation.
Intermittent T'ilter Treatment Unit/Svstem Desisn
The treatment/absorption field is designed based on utilizing the effective Long Term Acceptance Rate (LTAR) for
an intermittent sand filter treatment system utilizing pressure dosed distribution laterals and gravelless chamber
units as spray shields.. The new treatment system will consist of a fully pressure dosed sand filter Treatment bed
System with a 36-inch layer of filter sand (ASTM-33, "Concrete sand").
Long Term Acceptance Rate (LTAR)
Considering the application of the new state regulation 43:
Receiving Wastewater Treatment Level l; loading rate for sand filter is (1.0 gal./S.F.iday) for the minimum 36"
depth of treatment media;
Loading factors; (Table l0-2, pressure dosed application bed: 1.0 )
A(sÐ: Qd.: A: Area;
LTAR LTAR: i.0 Gal/S.F./day for ASTM-33, "Concrete sand"
L.F. 1:1.0 pressure dosing
Qd: flow (gallday):600 gpd
A(sÐ:600 gpd x 1.0 :600 S.F.
1.0 Gal/S.F./day
A 32' by 19'bed was excavated to a minimum 3.5'depth below finish grade. The excavation was backfill with 36-
inches of ASTM-33, "Concrete sand"
The system has four installed distribution laterals consisting ofcustom perforated distribution laterals on top of
sand layer and covered with 36 Quick-4 chambers in 4 rows with 7 chamber units per row for use as pressure dose
AS-BUILT, OWTS
Dave & Judy Douglas
160 River Ridge Dr
SE Job No. 15147.01
August 2,2017
Page 3
spray shields, as delineated on the plan. The bed is dosed from the simplex high head distribution pump system
installed in the third compartment of the septic tank.
A Valley precast three chamber 1,500 gallon concrete septic was installed with an a 500 gallon dosing
chamber equipped with a simplex pump Biotube vault dosing assembly and associated piping and controls.
Ribbed PVC risers were installed over the access openings with lids at the surface. The tank is tested
watertight, installed level, bedded and backfilled with class 6 base material. Two way cleanouts are
installed on the sewage pipe off the exterior wall of the residence and accessory buildings.
The septic tank effluent is pressure dosed from the pump chamber to a manifold pipe at the head of each
distribution lateral rows via a 1.25" discharge pipe installed with a continuous slope to allow drain back to
the tank. The effluent is equally pressure dosed through 1.25-inch custom perforated distribution laterals
running the length of the treatment bed rows installed on top of the installed sand filter media. The pipe has
3llí-inchorifices drilled every 2.5 feeforiented upward to spray onto the infiltrator quick-4 chamber
orifice Ball valves are installed on the end of each distribution lateral centered below the 4-inch inspection
ports on each end chamber. A piezometer monitoring well pipe riser with threaded cap was installed near
the Southwest corner of the field.
OWS Oneration Maintenance
Ownership of the system and responsibility for maintenance and repair will remain with the property
Owner. The Owner is encouraged to retain the services of qualified personnel to inspect the O'WTS and to
perform all maintenance and repairs necessary to ensure that the system components are maintained in
good operating condition and suitable vegetative cover is established on the fields. The components of the
OWTS system should inspected within 30 days of being placed into operation and should been inspected
and maintained bi-annually. The tank, absorption field and other system components should be visually
inspected bi-annually for debris, damage,leaks, or other potential problems. In general, for a properly
utilized system, septic tanks should be pumped every 2 - 4 years. The effluent filter should be cleaned
every six months and atthe time of pumping. Absorption fields should be maintained with suitable
vegetative cover and kept free of root invasive plants. Positive surface drainage away from the absorption
field should be maintained.
If you have any question or need any additional information, please
Sincerely,
SOPzuS ENGINEERTNG, LLC
Paul E. Rutledge
Design Engineer