HomeMy WebLinkAbout302 Peyton Dr - Special Inspections/Engineering - 02/13/2002February 13, 2002
Melody Homes
11031 Sheridan Blvd.
Westminster, Colorado 80020
Attn: Mr. Shawn Weiman
Re: Geotechnical Engineering Report
Ridgewood Hills 3`d Filing — Phase 4, Lot 199
302 Peyton Drive
Fort Collins, Colorado
Terracon Project No. 20005162
Irerracon
301 N. Howes • P.O. Box 503
Fort Collins, Colorado 80521-0503
(970) 484-0359 Fax: (970) 484-0454
B02'0 76 4 8
Terracon has completed a geotechnical engineering exploration for a proposed single family residence to
be located on the above referenced lot within the Ridgewood Hills 3`d Filing — Phase 4 residential
development project located in south Fort Collins, Colorado. The purpose of these services is to provide
geotechnical-engineering recommendations for design of foundations, slab on grade, and perimeter
drainage systems. Terracon performed a geotechnical engineering exploration for the 3`d Filing of
Ridgewood Hills in October of 1997, which encompassed the above -referenced lot. For further
information and additional geotechnical engineering recommendations please refer to our "Geotechnical
Engineering Report" for the Ridgewood Hills 3`d Filing Residential Development revised January 16,
2001, Project No. 20975149.
The additional site exploration, conducted on February 13, 2002, included one test boring drilled near the
center of the lot as requested. A swell -consolidation test was performed on a relatively undisturbed
sample obtained at a depth of 3-feet. The Log of Boring describing the soil, bedrock and groundwater
profile conditions along with the laboratory test results are attached with this letter. The materials tested
on the above mentioned lot, based on the swell -consolidation index, are classified as low swelling
according to the Colorado Association of Geotechnical Engineers (CAGE) criteria.
The subsurface soils encountered on this lot consisted of native sandy lean clay extending to the bedrock
below. Sandstone bedrock was encountered at an approximate depth of 2-feet below existing lot grade
and extended to the depth explored, approximately 14-1/2 feet.
It is our understanding the proposed residence will be constructed having a full depth basement.
Therefore, based on the properties of the soils and bedrock present on this lot, Terracon recommends the
proposed structure be supported by conventional type spread footings, (Type B). Conventional type slab
on grade construction procedures are feasible for the above -referenced lot.
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Geotechnical Engineering Report
Melody Homes — Ridgewood Hills 3`d Filing Phase 4
Fort Collins, Colorado
Terracon Project No. 20006162 802o7648
FOUNDATION RECOMMENDATIONS
Conventional Spread Footing Foundation Systems
The proposed residence should be supported by conventional -type spread footing foundations bearing
upon the undisturbed subsoils, recompacted native soils and/or engineered fill material. Footings should
be designed for a maximum bearing pressure of 2,500 psf. In addition, the footings should be sized to
maintain a minimum dead -load pressure of 750 psf. The design bearing pressure applies to dead loads
plus'/ of design live load conditions.
Basement Construction
Groundwater was not encountered on the lot to the maximum depths of exploration, 14-feet, during the
initial site exploration. Therefore full -depth basement construction is considered acceptable. To reduce
the potential for groundwater and/or surface water infiltration to enter the basement of the residence,
installation of a dewatering system is recommended. The drainage system should be constructed around
the exterior perimeter of the basement foundation, and sloped at a minimum 1/8 inch per foot to a
suitable outlet, such as a sump and pump system.
The drainage system should consist of a 4-inch diameter perforated pipe, embedded in free -draining
gravel, placed in a trench at least 12-inches in width. Gravel should extend a minimum of 3-inches
beneath the bottom of the pipe, and at least 1-foot above the bottom of the foundation wall. The gravel
should be covered with drainage fabric prior to placement of foundation backfill.
Backfill placed around the outside perimeter of the structure should be placed in uniform lifts; moisture
conditioned to optimum moisture content and mechanically compacted to 95% of Standard Proctor
Density ASTM 698, after the walls have been laterally braced.
Floor Slab Design and Construction
The variability of the existing soils at approximate slab subgrade elevation could result in differential
movement of floor slab -on -grade should the clay soils increase in moisture content. Based on the CAGE
criteria, the subsoils at the site have a slab performance risk category of 'low". Movement not likely to
exceed up to 2-inches or more is estimated if the subsoils below slabs become -wetted for zone of
approximately 10-feet below the basement. Slab -on -grade construction for the basement of this
residence should perform in accordance with the above criteria. The homeowner should be aware of the
risk of this slab movement and should take this into account prior to purchasing the residence. To reduce
potential slab movements, slabs should be constructed in accordance with the recommendations of the
Geotechnical Engineering Report.
F
Geotechnical Engineering Report
Melody Homes — Ridgewood Hills 3`d Filing Phase 4
Fort Collins, Colorado
Terracon Project No. 20005162
Surface Drainage
B 02 -0 76 4 8
30z Pa7 � A4.
Positive drainage should be provided during construction and maintained throughout the life of the
proposed residence. In areas where sidewalks or paving do not immediately adjoin the structure, we
recommend that protective slopes be provided with a minimum grade of approximately 10 percent for at
least 10-feet from perimeter walls. Backfill against foundations, exterior wails and in utility and sprinkler
line trenches should be well compacted and free of all construction debris to reduce the possibility of
moisture infiltration. Downspouts, roof drains or scuppers should discharge into splash blocks or
extensions when the ground surface beneath such features is not protected by exterior slabs or paving.
Sprinkler systems should not be installed within 5-feet of foundation walls.
Construction Observation
The following observations are recommended during construction:
• Foundation Excavation;
• Footing sizes and void form placement;
• Foundation Wall Steel/Reinforcement;
• Perimeter Drainage System; and
• Floor Slab for Basement and Garage
We appreciate the opportunity to be of service to you on this phase of your project. If you have any
questions, or if we may be of further service to you, please feel free to contact us.
Sincerely,
TERRACON
. Lambert, E.I.T.
nical Engineer
to: Addressee (6)
Manager
Enclosures (2): Log of Boring (1)
Swell -Consolidation Test Results (1)
3