HomeMy WebLinkAboutWATER'S EDGE @ RICHARD'S LAKE - PDP - 58-86J - SUBMITTAL DOCUMENTS - ROUND 1 - RECOMMENDATION/REPORTTABLE OF CONTENTS
Page No.
j Letter of Transmittal..........................................................................................................................i
iINTRODUCTION
.............................................................................................................................1
PROPOSEDCONSTRUCTION......................................................................................................
2
i
�.l
SITE EXPLORATION.............................................................................:....................................:..
2
_
Field Exploration....................................................................................................................
2
Laboratory Testing................................................................................................................
3
,n
SITECONDITIONS.................................:.:.....................................................................................
4
SUBSURFACECONDITIONS........................................................................................................
4
Geology........................................................................... ......................................................
SoilConditions
4
......................................................................................................................
5
Field and Laboratory Test Results........................................................................................
6
GroundwaterConditions.......................................................................................................
7
PRELIMINARY ENGINEERING ANALYSES AND RECOMMENDATIONS ................................
8
GeotechnicalConsiderations................................................................................................
8
IJ
Foundation Systems - Preliminary Recommendations for Spread Footings ........................
9
Foundation Systems - Preliminary Recommendations for Drilled Piers .............................
10
_
Basement Construction........................................................................................................
10
1
Floor Slab Design and Construction...................................................................................
11
Preliminary Pavement Design and Construction................................................................
12
Earthwork............................................................................................................................
12
GeneralConsiderations............................................................................................
12
SitePreparation.........................................................................................................
12
Fill Materials and Placement.....................................................................................
13
DetentionPonds .................................... :.:.................................................................
13
Additional Design and Construction Considerations..........................................................
14
UndergroundUtility Systems.....................................................................................
14
SurfaceDrainage......................................................................................................
14
GENERALCOMMENTS...............................................................................................................
15
APPENDIX A
Vicinity Map — Figure No. 1
Test Boring Location Diagram — Figure No. 2
Bedrock Contour Map — Figure No. 3
Soil Conservation Map — Figure No. 4
Logs of Borings — Nos. 1 through 12
APPENDIX B
Laboratory Test Results
APPENDIX C
General Notes
iii
Preliminary Geotechnical Engineering Report lrerracon
Skyland Meadows Developments, Ltd.
Water's Edge at Richard Lake - Approximately 81 Acres
Section 30, Township 8 North, Range 68 West
Fort Collins, Larimer County, Colorado
Project No. 20055201
Basement construction should be feasible provided the recommendations contained herein and
exterior perimeter drainage systems are installed around all lower level/basement areas. Slab -
on -grade construction is feasible provided the recommendations set forth in this report are
followed. Terracon recommends a minimum 4-foot separation below the bottom of the slabs to
the underlying siltstone/claystone bedrock where encountered in portions of the site. Other
preliminary design and construction recommendations, based upon geotechnical conditions, are
presented in the report. ,
This report is a preliminary investigation and is not intended for final design or construction.
Terracon recommends a final comprehensive investigation be performed after final grades,
buildings and infrastructure is more accurately determined. We appreciate being of service to you
in the geotechnical engineering phase of this project, and are prepared to assist you during the
final design phases as wed_
Sincerely, O�`:�•••••:: ��
TERRACON �,��-ORD I'. R/�, .•tea
2n
David A. Richer, f'••....••' ���� Christopher M. Gemperline
Geotechnical Engin t Manager Engineering Geologist
Copies to: Addressee (4)
Vignette Studios (3): Mr. Don Tiller
Preliminary Geotechnical Engineering Report 1rerracon
Skyland Meadows Developments, Ltd.
Water's Edge at Richard Lake - Approximately 81 Acres
Section 30, Township 8 North, Range 68 West
Fort Collins, Larimer County, Colorado
Project No. 20055201
anticipated foundation bearing depth have low to moderate load bearing capability and the
bedrock has moderate load bearing characteristics. Based on the preliminary geotechnical
engineering analyses, subsurface exploration and laboratory test results, Terracon recommends
the proposed single family and multi -family residential structures, depending upon actual loading
conditions and final grading contours, be supported by conventional type spread footings bearing
on the overburden soils, engineered fill material, or footings extended to the underlying low
expansive siltstone/sandstone bedrock ,in portions of the site. In areas where the foundation
systems are to be placed within 3-feet or into the siltstone/claystone bedrock formation, which
typically exhibits a higher swell potential than the siltstone/sandstone bedrock, use of a drilled
pier/caisson foundation will be required.
If the 3-foot separation between the bottom of the proposed foundation systems and the
underlying moderately expansive siltstone/claystone bedrock stratum cannot be achieved due to
design elevations, these structures should be supported by a grade beam and drilled
pier/caisson foundation system. Based on the surface elevations obtained at each preliminary
test boring and the estimated depth to weathered bedrock encountered in each boring, we have
included a conceptual bedrock contour map, Figure No. 3 illustrating the bedrock profile across
the site.
In areas where the low to moderately expansive bedrock was encountered at depths greater
than the anticipated depth of basement excavations, all footings should be placed on the native
overburden soils. Where the low to moderately expansive siltstone/sandstone bedrock
formation was at depths within the anticipated basement excavations, all footings for upper and
lower levels should be extended to the bedrock layer to minimize the potential for differential
movement between two strata. As an alternative, consideration should be given to an over -
excavation and replacement procedure of the bedrock material for least 2-feet below foundation
levels within the basement portions for these lots. For this alternative, the bedrock at the lower
level should be removed and replaced with the native overburden soils. The overburden soils
should be placed in uniform lifts, moisture conditioned to near optimum moisture content and
compacted to at least 95 percent of Standard Proctor Density (SPD) ASTM D698. Using this
approach all footings would then be placed on uniform soils, which would reduce the potential
for differential movement of two soil types.
If an over -excavation and replacement procedure is not desired, another alternative to consider
where bedrock is in close proximity to basement elevations would be to support the structures
on a grade beam and drilled pier/caisson foundation system. This provides another alternative
to reduce the potential for differential movement between two soil types.
November 22, 2005
Skyland Meadows Developments, Ltd.
7400 East Crestline Circle — Suite 230
Greenwood Village, Colorado 80111
Attn: Mr. Joe Hemmelgarn
Irerracon
Consulting Engineers & Scientists
Terracon Consultants, Inc.
301 North Howes
Fort Collins, Colorado 80521
Phone 970.484.0359
Fax 970,484.0454
www,terracon.com
Re: Preliminary Geotechnical and Geological Engineering Report
Proposed Residential Development —Approximately 81-Acres
South % of Section 30, Township 8 North, Range 68 West
North of Richards Lake P.U.D. —phase I and West of Larimer County Road 11
Fort Collins, Larimer County, Colorado
Terracon Project No. 20055201
Terracon completed a preliminary geotechnical engineering exploration for the proposed 81-acre
parcel located north of Brightwater Drive and the Phase I portion of Richards Lake P.U.D., west of
Larimer County Road 11 in north Fort Collins, Colorado in November of 2004. Skyland Meadows
Developments, Ltd. has requested Terracon to resubmit the report to accommodate their
conceptual design plans for Water's Edge at Richard Lake. The site is located in the South '/2 of
Section 30, Township 8 North, Range 68 West of the 6th Principal Meridian, Larimer County,
Colorado. This revised report has been prepared in accordance with the reliance agreement, and
Proposal No. 2004387 dated November 4, 2005.
The results of our preliminary engineering study, including the boring location diagram,
laboratory test results, test boring records, USDA-SCS map and interpretation, and the
preliminary geotechnical recommendations needed to aid in the preliminary planning and design
of foundations, pavements, and other earth connected phases of this project are attached.
The surface conditions throughout the majority of the site as depicted from Terracon's borings
drilled in November of 2004, generally consisted of an approximate 6-inch layer of silty topsoil.
Underlying the surface layer at each boring location generally consisted of sandy lean clay and
lean clay, which extended to the depths explored, to the coarse granular strata or to the bedrock
below. A layer of silty sand with gravel, varying from poorly graded to well graded was
encountered in Test Boring No. 11 at an approximate depth of 17-feet below site and extended
to the bedrock stratum below. Siltstone/sandstone and siltstone/claystone bedrock with
intermittent cemented sandstone lenses was encountered in each boring with the exception of
Boring No. 12, at approximate depths of 1 to 22-feet below existing site grades and extended to
the depths explored, approximately 25-feet. Groundwater was not encountered to maximum
depths of exploration during initial drilling activities or when checked several days after drilling.
The results of field exploration and laboratory testing completed for this preliminary study indicate
that the soils and bedrock at the site have low to moderate expansive potential. The soils at
Delivering Success for Clients and Employees Since 1965
More Than 70 Offices Nationwide
PRELIMINARY GEOTECHNICAL and GEOLOGICAL ENGINEERING REPORT
WATER'S EDGE AT RICHARDS LAKE
PROPOSED RESIDENTIAL DEVELOPMENT - APPROXIMATELY 81 - ACRES
NORTH OF RICHARD LAKE DEVELOPMENT, SOUTH OF SERRAMONTE HIGHLANDS
AND WEST OF LARIMER COUNTY ROAD 11
SOUTH'/2 OF SECTION 30, TOWNSHIP 8 NORTH, RANGE 68 WEST
FORT COLLINS, LARIMER COUNTY, COLORADO
TERRACON PROJECT NO. 20055201
NOVEMBER 23, 2005
Prepared for.
SKYLAND MEADOWS DEVELOPMENTS, LTD.
7400 EAST CRESTLINE CIRCLE — SUITE 230
GREENWOOD VILLAGE, COLORADO 80111
ATTN: MR. JOE HEMMELGARN
Prepared by.
Terracon
301 North Howes Street
Fort Collins, Colorado 80521
1rerracon