HomeMy WebLinkAboutAs-built Design Report 04.02.2019April 2, 2019
Gregg Mackey
Po Box 398,
Basalt, CO, 81621
"gmack pers" gmackey3@gmail.com
John and Robert Parrington
Tally Ho Construction
0145 County Road 225
Rifle, CO 81650
tallyhoconst@sopris.net
RE: AS -BUILT, Onsite Wastewater Treatment System (OWTS), Mackey Commercial Warehouse
Facility, 0050 C.R. 110, Garfield County, Colorado
SE Job No. 18197.01 Parcel #: 2393-074-00-012, Garfield County Permit # SEPT -11-18-5581
Dear Gentleman:
Pursuant to County requirements, this letter provides documentation that the new Onsite Wastewater Treatment
Systems (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 at
various times during construction, prior to final backfill and after all installations was completed. The system
constructed on site was designed and built to serve the needs of a commercial facility currently under
construction. The installed system was designed with a maximum treatment capacity of 100 gallons per day
based on usage with population of 5 employees and 5 person transients. Sopris Engineering performed site
visits to inspect and document the as -built conditions of the constructed system. Inspections were coordinated
with Tally Ho Construction. The as -built conditions and installation of the new OWTS components is in
compliance with Garfield County Regulations; the recommendations and specifications delineated on the civil
OWTS design plan, C1-OWTS Plan, dated 11-15-2018, by Sopris Engineering. The design criteria and system
sizing information is summarized below. An As -built OWTS record drawing is attached delineating the As -
built descriptions and location of the components.
Summary Design Criteria
The OWTS is designed with a maximum treatment capacity of 100 gallons per day based on the estimated daily
wastewater flow per population usage of up to 5 employees and 5 person transients in accordance with Table 6-2
values, Section 43.6, A.4. The OWTS will include the installation of a 1000 gallon 2 -compartment concrete septic
tank with concrete risers and lids installed at the surface. The tank was installed with an inlet sanitary tee and an
outlet effluent filter sanitary tee. A gravity schedule -40 or SDR -26 sewer pipe with a cleanout will be installed from
the warehouse facility structure to the tank. The soil treatment unit (STU) consists of a single leaching chamber
trench that provides 75 S.F. of total absorption area. The septic tank effluent is distributed by gravity via a 4"
distribution pipe connected to the head end cap chamber trench. Observation ports with caps are installed on each
end chamber unit. The design is in compliance with the current County regulations with design calculations based
on the soil type, texture and structure with an appropriate long term acceptance rate (LTAR).
502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704-0311 • Fax (970) 704-0313
SOPRIS ENGINEERING • LLC
civil consultants
Gregg Mackey, OWTS
050 C.R. 110
SE Job No. 18197.01
April 2, 2019
Existing and Proposed Site Conditions
The site is located on relatively flat dry steeped land areas with a slight slope downward toward the Southewest.
Vegetation consists of sagebrush, shrubs and grasses. The Site comprises approximately 3.9 acres. The site is
partially developed with several buildings and associated driveway on the two primary stepped land areas. The new
OWTS will serve the new 4900 S.F. warehouse building constructed in the south central portion of the site on the
lower benched area with the Field to be located east of the building in a flat area adjacent to and along the toe of
the Southwesterly slope. The existing ground surface in the proposed absorption field area has average 5%. Slope.
Domestic water is supplied by an existing community water system. The site has an existing gravel surfaced
driveway that traverses through the property from the primary access off C.R. 110.
The proposed site improvements included the construction of a 4900 S.F. commercial warehouse building structure
that has two l/ bath restrooms. The new OWTS was constructed as designed for limited commercial usage capacity
to serve potential lease holders and transient visitors.
Sub Surface Conditions and observation
Subsurface soil investigations and USDA soil texture method tests were performed by Sopris Engineering on
October 26, 2018. The soils below nil to 6 inches of mixed surface fill & topsoil consist of medium dense sandy silt
loam with moderate granular to slightly blocky structure with some cobbles and gravels.
Shallow and deep excavations were observed on site adjacent to the proposed building location. The native soils
sampled from 2-3 feet below the surface are characterized as a soil type 2 consisting of silt loam texture with
moderate granular structure. The percentage of cobbles and gravels below 24 inches was less than 15% in the silt
loam to the 7 foot depth explored. This soil has an effective loading rate for conventional soil treatment of 0.60
gal/S.F./day for a level 1 conventional treatment system. The equivalent percolation rate is assumed to be
approximately 16-25 minutes per inch. No free water was encountered in excavations on site. No excessive
boulders or cobbles were encountered during excavation. Observations of the soils, in the excavation during
construction, appeared to be consistent with the previous subsurface soil investigation.
Design Flow
The design flow is calculated as follows:
The design flow is calculated as follows for low usage commercial facility onsite wastewater treatment system
(OWTS)
From the Regulation 43 usage Table 6-2 :
Max. Design flow (Qd) = # of people x (avg.per capita flow)
Qd=daily worker office: 5 persons @ 15 gpd = 5 x 15 = 75 gpd
Qd=transient visitor: 5 persons @ 5 gpd = 5 x 5 = 25 gpd
Total Design flow Qd = 100 gpd
Treatment -Soil Treatment Unit/ Absorption System Design
The treatment/absorption field was designed based on utilizing the effective Long Term Acceptance Rate (LTAR)
for the native soils and the application of appropriate loading factors for a soil treatment unit system utilizing
gravity distribution to gravelless chamber trenches. The new treatment system and STU consist of gravity
distribution of septic tank effluent to a single chamber trench with treatment across the scarified native soil
absorptive surface.
Gregg Mackey, OWTS
050 C.R. 110
SE Job No. 18197.01
April 2, 2019
Long Term Acceptance Rate (LTAR)
Receiving Wastewater Treatment Level 1; loading rate for silt loam is (0.60 gal./S.F./day) for soil type 2.;
Loading factors; (Table 10-2, Gravity application trenches = 1.0) and
(Table 10-3, gravelless chambers = 0.7)
A(sf)= Qd.: A=Area;
LTAR = 0.60 Gal/S.F./day for silt loam, soil type 2
Qd = flow (gal/day) = 100 gpd
L.F.1 = 1.0 Gravity Distribution
L.F.2 = 0.7 Chambers
A(sf) = 100 gpd x 1.0 x 0.7 = 70 S.F.
0.60 Gal/S.F./day
Number of quick -4 chambers:
100 S.F = 6 chambers Use 6 Infiltrator Quick -4 with appropriate cnd caps.
12 S.F./Chamber
Installed 6 Quick -4 chambers in one trench 26' long by 3' wide with end caps and inspection ports on both ends as
delineated on the attached OWTS Record Drawing.
OWS Operation and 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 OWTS 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 3 - 5years. The effluent filter should be cleaned every six months and at the 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 call.
Sincerely,
SOPRIS ENGINEERING, LLC
p40/.."-/ es
Paul E. Rutledge
Design Engineer
Yancy Nichol, PE
Principal