HomeMy WebLinkAboutEngineer's Design PlanSeptember 21,2023
Freeup Storage LtC.
1440 Brickyard Road lJnit 4,
, Golden, CO, 80403
RE Design Report-Onsite Wastewater Treatment System (OWTS), Freeup Commercial Warehouse
Facility,357 South l6tr' Street, Silt, Garfield County, Colorado
SE Job No. 33072.01 Parcel Number: 2179-101-00-0t8
Dear Gentleman:
This letter report presents the applicable findings in regard to the design and construction of an Onsite Wastewater
Treatment System (OWTS) at the above referenced Site, in support of your OWTS permit application to Garfield
County. The design recommendations, specifications and construction details are dãlineated on the attached OWTS
permilconstruction plan that is overlaid on the survey site plan plat by the SurvCo, Inc. dated 0Bllgl2l.
The Sopris Engineering OWTS design is based on evaluation of existing physical site features, geotechnical soils
investigation and site conditions with respect to the proposed facility u*g", building layout and applicable regulatory
design criteria that is in accordance with Garfield County OWTS Regulatìons. The system on site is designed to
serve the needs of a commercial warehouse facility currently under construction by Spartan Construction
Management. The desigr criteria and system sizing information is summarized below.
Summarv Desisn Criteria
The OWTS is designed with a maximum treatment capacity of 75 gallons per day based on the estimated daily
wastewater flow per population usage of up to 2 employees and 6 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 will be inÀtalled 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) wìll consist of one leaching chamber trench
that provide 156 S.F. of total absorption area. The septic tank effluent will be distributed by gravity -v
ia a 4,,
distribution pipe connected to the head end cap chamber trench. Observation ports with caps will be installed on each
end chamber unit. The design is in compliance with the curent County regulaiions with design calculations based on
the soil type, texture and structure with an appropriate long term acceptance rate (LIAR).
Existins Site Location
The subject site is located at357 South l6tr' Street, on a parcel of land situated in the south % of the south % of the
northYz of the northeast Y+, and lots 7 and 2, section 10, township 6 south, range 92 west of the 6tl' p.M., lying
southerly of the D&RGW railroad riglrt of way line, northerly of U.S. Highway Interstate 70 right of way iine, and
westerly of Road No. 31 I .
Existins and Pronosed Site Conditions
The project site is located on generally level,
storage/parking. The existing structures at the
is surfaced with gravel and currently being used for RV
site are single-story, metal-clad structures. The type of foundation
stem for the exi structures is not known. Access drives between the structures are vel surfaced
502 Main Street Su ite A3 Carbondale, C0 81623 (970) 704-03 1 1 Fax (9/0) /04-031 3
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$oPRt$ tncnrrnutc o llG civil consultants
Freeup Storage Lrc, OWTS
357 S l6th Street
SE Job No. 33072.01
September 21,2023
The site slopes gently to the south with a relatively small drainage pond, approximately 3 feet deep, located near the
southern boundary within the footprint of proposed Building'K'. The Site comprises approximately 8.95 acres. The
new OWTS will serve the new 25200 S.F. warehouse building being constructed in the east central portion of the site
with the Field to be located north of the building in a flat area adjacent to the proposed structure. The existing ground
surface inthe proposed absorptionfield area has average 5o/o.Or less 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 S l6th Street.
The proposed site improvements include the construction of a 25200 S.F. commercial warehouse building structure
that will have one %bafh restroom. The new OWTS will be constructed designed for limited commercial usage
capacity to serve potential lease holders and transient visitors. The proposed site improvements will include
appropriate site grading around the structure, OWTS, and driveway improvements within the development area.
Sub Surface Conditions and observation
Subsurface soil investigations were performed by Yeh and Associates, Inc. on June 10,2022. The soils in the area of
the proposed absorption field were sampled and characterized by application of the Sieve Analysis Method and
Stress Testing. The soils were tested to determine the hydraulic loading rate and to confirm the appropriate
absorptive surface suitable for conventional absorption systems in native soils. A shallow and deep excavated pit
was observed in the western central portion of the site adjacent to the proposed field location. The soils below 4 to 6
inches of sand and gravel topsoil consist of soft, loose sandy clay loam. The percentage of cobbles and gravesl
below 24 inches was less than20%o in the sandy clay loam tothe 12-14 foot depth explored. The soil appears to be
consistent across the site.
The native soils sampled from 2-3 feet belowthe surface are characterized as a soil type 3 consistingof clay loam
texture with moderate granular structure. This soil has an effective loading rate for conventional soil treatment of
0.35 gallS.F .lday for a level 1 conventional treatment system. The equivalent percolation rate is assumed to be
approximately 41-60 minutes per inch. Increased quantities of gravel are encountered at shallow depths within l-foot
of the existing surface grade. No free water was encountered in the excavations on site. Groundwater levels are
expected to be well below 10 feet from the existing surface grades. The soils appear suitable for a conventional
shallow absorption field consisting of gravelless infiltration chamber units.
Desien Flow
The design flow is calculated as follows:
The design flow is calculated as follows for low usage commercial facility onsite wastewater treatment system
(owrs)
From the Regulation 43 usage Table 6-2:
Max. Design flow (Qd): # of people x (avg.per capita flow)
Qd:daily worker office: 2 persons @ 15 gpd: 2 x 15 : 30 gpd
Qd:transient visitor: 3 persons @ 6 Wd:6 x 5 :30 gpd
Average Peak Day Flow Qavg:60 gpd, Minimum Design FIow Qd :75 gpd
The septic tank capacity required for a minirnum 48 hour detention time is calculated as follows:
V :75 gal/day * 2:150 gallons (Per Regulation a minimum 1,000 gallon capacity, two compartment is required).
Use a 1,000 gallon 2-compartment concrete septic tank. The tank shall have inlet and outlet sanitary tees with an
effluent filter. The tank access shall be maintained with risers and lids installed at the finish surface grade.
Freeup Storage Lt,C, OWTS
357 S l6tr'Strcet
SE Job No. 33072.01
September 21,2023
Treatment-Soil Treatment Unit/ Absorption Svstem Desien
The treatment/absorption field is designed based on utilizing the effective [,ong 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 absorption field will consist of gravity
distribution of septic tank effluent to an indivitlual chamber [rerruh wil"h treatnrerrl auross the scarified rrative suil
absorptive surface.
[.ong Term Acceptance Rate (LTAR)
Wastewater Treatment tævel l; loading rate for sandy clay loam is (0.35 gal./S.F./day) for soil type 3;
lnading factors; (Table 10-2, Gravity application trenches = I .0) and
(Table 10-3, gravelless chambers : 0.7)
A(sÐ: Od .: A: Area;
LTAR LTAR:0.35 Gal/S.F.iday for clay loam
Qd : flow (gtllday): 75 gpd
L.F.l:1 .0 Gravity Distribution
L.F.2:0.1 Chambers
A(sÐ : 75 gpd x 1.0 x 0.7 : 150 S.F
0.35 Gal/S.F./day
Number of quick-4 chambers
150 S.F : 12.5 chambers, Use 13 Quick-4 Infiltrator chambers or equivalent bio-diffiisers
l2 S.F./Chamber
Use 13 Quick-4 Infiltrator chambers in one trench 54' long by 3' wide with two end caps as delineated on the plan.
The septic tank effluent will be gravity distributed to the head of the chamber row via a 4" distribution pipe from the
septic tank. Additional soil evaluation will be performed during construction to verify the soils in the excavation. The
SDR-26 or schedule 40 PVC sewer pipes will be installed with respect to existing grades. The gravity sewer pipes
routed to the septic tank or STU will be bedded and backfilled with Class-6 base material and encased in blue board
insulation if depths are less than 3 feet within any drive area.
Construction and Insnections
Prior to construction of the permitted system, the engineer should be contacted by the contractor and owner well in
advance to provide adequate time to discuss the system components with the contractor, answer questions, resolve
any conflict issues and schedule inspection site visits based on construction progress. A pre-OWTS construction
meeting is essentialand required priorto installation of the OWTS. All septic system components shallbe staked in
the field for approval by the Engineer prior to excavation.
During initial construction the engineer will evaluate the soils in the absorption treatment field excavations to confirm
soil conditions and make adjustments as needed. All septic system components and trench installations are to be
approved by the Engineer prior to backfilling. All installation will be inspected, surveyed, reported and delineated in
the Certification letter and Reoorcl drawing. The contractor need l"o photo tlouuutenl all OWTS corutructiolt phascs
and supply photos to thc Enginccr.
Freeup Storage LL,C, OVITS
357 S l6'h Str,eet
SE Job No. 33072.01
September 21,2023
County Regulations require that the Engineers of record perform site impections of the permitted system during
csnstruction and provide "As-Built" documentation of the installed system to the County after construction is
complete.
0\üS Ooeration ¡nd Mainten¡nce
Ownership of the system and responsibility for maintenance and repair will rernain with the property Owner. The
Owner is encouraged to retain the services of qualified penonnel 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 systen¡ septic tanks should be punped every 3 - 5 years
The effluent filter should be cleaned every six months and at the tirne of pumping. Absorption fields should be
rnaintained 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 informatio4 please call
Sirrcerely,
SOPRIS ENGINEERING, LI,c
Paul E. Rutledge
Design Engineer
Y
Principal
28377 :
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