HomeMy WebLinkAboutRFP - P954 POLICE SERVICES FACILITY DESIGN & BUILD (7)City of Fort Collins
Administrative Services
Purchasing Division
CITY OF FORT COLLINS
ADDENDUM No. 5
SPECIFICATIONS AND CONTRACT DOCUMENTS
Description of Bid: P954 Police Services Facility — Design/Build
OPENING DATE: 3:00 P.M. (Our Clock) December 13, 2004
To all prospective bidders under the specifications and contract documents described
above, the following changes are hereby made.
ADD: CTL Thompson Soils Report November 19, 2004 (attached)
RECEIPT OF THIS ADDENDUM MUST BE ACKNOWLEDGED BY A WRITTEN
STATEMENT ENCLOSED WITH THE BID/QUOTE STATING THAT THIS ADDENDUM
HAS BEEN RECEIVED.
215 North Mason Street • 2nd Floor • P.O. Box 580 • Fort Collins, CO 80522-0580 • (970) 221-6775 • FAX (970) 221-6707
IF
Bedrock
Claystone bedrock was encountered in 5 of the 8 borings at depths ranging
from 29 to 33 feet below the existing ground surface (elevation 4911 to 4914). The
bedrock was hard to very hard, based on field penetration resistance tests.
Ground Water
During our July, 2000 investigation, ground water was encountered 12 to 13
feet below the ground surface. During this investigation and the study for the
widening of Timberline Road, ground water was measured at depths of 23 to 26 feet
below the ground surface. The borings from the 2000 investigation had been
destroyed and were not available to be checked at this time. We believe the ground
water may be lowering in response to the cessation of irrigation and due to
development of the adjacent parcels, where deep drain systems were installed.
Ground water levels on the site are expected to fluctuate with seasonal conditions
and precipitation. There may also be localized shallow ground water near the existing
irrigation ditch. Ground water is likely to develop and rise after landscape irrigation .
starts. Ground waterwill likely complicate installation of drilled piers (if selected). At
this time, we do not believe ground waterwill affect the performance of the proposed
building, unless an unusually deep basement is selected.
The green grass and cottonwood trees present in the east portion of the site
suggest there may be a source of water in this area. It is unlikely the ground water
mounds in this location, but more likely surface water collects in that area. Given the
agricultural history of the site, there may also be a drain tile that discharges
underground. Excavation of test pits in this area may provide some information.
Seismicity
Based upon the 1997 Uniform Building Code, the subsurface conditions
encountered in our borings suggest Soil Profile Type SD. If the 2000 or 2003
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 5
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
International Building Code is adopted, we believe the site will classify as Site Class
D. Seismic design criteria should be determined during a design level investigation.
ESTIMATED SWELUCOLLAPSE RISK
Overall, the preliminary data suggests the site soils and bedrock are
predominately low swelling or may exhibit collapse when wetted. Expansive or
collapse -prone soils may result in heave or settlement of foundations or floor slabs.
Based on the geology of the site and our experience, we anticipate collapse -prone or
low expansive soils will be encountered sporadically throughout the site.
SITE DEVELOPMENT
The primary geotechnical concerns we believe will influence development and
construction of this site are the presence of soils that could exhibit consolidation
upon wetting and expansive soils. No geotechnical constraints were identified which,
in our opinion, preclude development of the site. Proper engineering of site grading,
sub -surface drains, pavements, foundations, floors and flatwork construction will be
needed to mitigate the effects of collapse -prone and expansive soils.
Fill Placement
The ground surface in areas to be filled should be stripped of vegetation,
scarified, and moisture conditioned and compacted to at least 95 percent of standard
Proctor maximum dry density (ASTM D 698). We anticipate stripping will require cuts
of 4 to 6 inches. Strippings should be placed in fills outside the limits of pavements
and structures. Permanent cut and fill slopes should be no steeper than 3:1
(horizontal:vertical) and should be seeded or mulched to reduce erosion.
The properties of fill will affect the performance of foundations, slabs -on -
grade, utilities, and pavements. The on -site soils can be used as site -grading fill
provided deleterious, organic materials are substantially removed. Fill should be
placed in thin loose lifts, moisture -conditioned and densely compacted prior to
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 6
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
IF
placement of the next lift. Clay fill should be moistened to between optimum and 3
percent above optimum moisture content and sand fill should be moistened to within
2 percent of optimum moisture content. Fill should be compacted to at least 95
percent of standard Proctor maximum dry density (ASTM D 698). The placement and
compaction of site grading fill should be observed and tested by a representative of
our firm during construction. Guideline site grading specifications are presented in
Appendix B.
Utility Construction
We believe subsoils encountered in our borings can be excavated using
typical heavy-duty equipment. The overburden soils generally consist of clay and
sand underlain by claystone bedrock. We do not anticipate bedrock will be
encountered during utility installation. We believe the clay soils can be classified as
Type B soil and the sand as Type C based on the Occupational Safety and Health
Administration (OSHA) Standards governing excavations published in 29 CFR, Part
1926. Type B soils require maximum slope inclination of 1:1(horizontal:vertical), and
Type C soils require maximum slope inclination of 1.5:1. Ground water was generally
deep across the site. If ground water is encountered, temporary dewatering may be
required during utility construction. Dewatering can likely by accomplished by
sloping excavations to occasional sumps and removing the water by pumping.
Excavations below ground water will require flatter slopes or bracing. The contractor
should identify the soils encountered in excavations and refer to OSHA standards to
determine appropriate slopes. A professional engineer should design excavations
deeper than 20 feet.
Water and sewer lines are usually constructed beneath paved drives.
Compaction of trench backfill will have a significant effect on the life and
serviceability of pavements. Trench backfill should be native soils, placed and
compacted to the criteria in Fill Placement. The placement and compaction of fill and
backfill should be observed and tested by a representative of our firm during
construction. Suitability of trench backfill should be determined by our engineer prior
to use on or adjacent to the site.
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 7
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384.115
0
Pavement
We anticipate moderate plasticity clay and similar fill will underlie a majority of
the site after grading. We believe the clay and fill will provide fair to poor pavement
support characteristics. We estimate parking lots and access roads will be paved
with a section equivalent to 4 to 6 inches of asphalt concrete over 6 to 12 inches of
aggregate base course. Swell mitigation may be required if subgrade soils indicate
swells of greater than 2 percent after wetting under a 150 psf load. The swell
mitigation may require the use of 12 inches of fly ash stabilized subgrade. A
subgrade investigation and pavement design should be performed after
improvements have been sited.
BUILDING CONSTRUCTION
Foundations
The design of the project is conceptual at this time. Foundation load
conditions will be dependant upon the selected configuration. We believe either
shallow or deep foundations may be appropriate for the proposed structure. A design
level geotechnical investigation should be conducted after plans are more defined.
Shallow foundations could consist of footings or a reinforced mat. We
estimate allowable soil pressures on the order of 2,000 to 4,000 psf can be used for
preliminary designs. Sub -excavation may be required to depths of 3 to 5 feet below
shallow foundations, if collapse -prone soils are present. A foundation excavation
observation by us will be required if shallow foundations are selected.
For deep foundations, drilled piers bottomed in bedrock are the primary
choice. Driven piling is not recommended due to the presence of large cobble in the
sand above the bedrock. Allowable end pressures for pier foundations are
anticipated to be on the order of 30,000 to 50,000 psf with skin friction in the bedrock
penetration zone only of 3,000 to 5,000 psf. Pier installation may be complicated by
caving sand, ground water and the presence of cobbles. Temporary casing and
dewatering of piers should be anticipated.
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 8
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
IF
Below -Grade Construction
Ground water was encountered at the site. Our investigation indicates current
ground water levels are about 23 to 26 feet below the ground surface. We do not
anticipate these ground water levels will affect basement construction for the project,
unless an unusually deep basement is planned. Ground water levels will fluctuate
seasonally and ground water rise of 3 to 5 feet should be anticipated.
Surface water can penetrate relatively permeable loose backfill soils located
adjacent to foundations and collect at the bottom of relatively impermeable
excavations. Water in wall backfill can cause wet or moist foundation conditions or
excessive lateral pressure on foundation walls. Foundation drains will be necessary
around below -grade areas. If ground water is encountered near the proposed
basement level during the design -level investigation, an upgraded foundation drain
system may be required that includes underslab laterals, and a sump pit with
redundant pumps and alarm system.
Slabs -on -Grade and Basement Floor Construction
Based upon the preliminary data, we believe a slab -on -grade basement floor
could be used for the structure if the risk of movement is acceptable. At this time, we
estimate floor slab movements of about 1 inch due to heave or settlement is possible.
Sub -excavation below floor slabs may be necessary if swelling or collapse prone
soils are encountered. A structurally -supported floor system should be considered if
movement is unacceptable. The potential magnitude of slab movement should be
more thoroughly defined during the design level geotechnical investigation.
Concrete
Concrete in contact with soil can be subject to sulfate attack. Based on the
previous investigations and our experience in this area, we believe water-soluble
sulfate concentrations will be in the range that indicates Class 0 exposure to sulfate
attack, as defined by the criteria of the American Concrete Institute (ACI). For this
level of sulfate concentration, ACI indicates any type of cement can be used for
concrete that comes into contact with the subsoils. In our experience, superficial
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 9
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
damage may occur to the exposed surfaces of highly permeable concrete, even
though sulfate levels are relatively low. To control this risk and to resist freeze -thaw
deterioration, the water-to-cementitious material ratio should not exceed 0.50 for
concrete in contact with soils that are likely to stay moist due to surface drainage or
high water tables. Concrete should be air entrained.
Surface Drainane
Performance and stability of soils and bedrock are influenced, to a large
degree, by the moisture conditions existing within the materials. We recommend
overall drainage be planned to provide for rapid removal of runoff away from the
buildings. We recommend roof downspouts and surface drains convey runoff onto
positive sloping surfaces that will promote rapid removal of runoff in a controlled
manner. We generally recommend paved surfaces and flatwork have a minimum
slope of 2 percent to facilitate rapid water removal. Landscaped areas should have a
minimum slope of at least 5 percent.
RECOMMENDED FUTURE INVESTIGATIONS
Based on the results of this investigation and the proposed development, we
recommend the following investigations be performed:
1. Review of site grading plans by our firm;
2. Subgrade investigation and pavement design;
3. Design -level geotechnical investigation; and
4. Construction testing and observation for site development and building
construction.
LIMITATIONS
Our borings were widely spaced to provide a general picture of subsurface
conditions for site grading and preliminary planning of development. We believe this
investigation was conducted in a manner consistent with that level of care and skill
ordinarily used by geotechnical engineers practicing in this area at this time. No
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 10
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
warranty, express or implied, is made. If we can be of further service in discussing
the contents of this report or analyses of the influence of subsurface conditions on
the design of the proposed development, please call.
CTLI
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Adam D. TschidC'.L.-NA
1/ °Project Engineer•••'�1
Reviewed by:
Thomas A. Chapel, CPG, PE
Associate & Division Manager
ADT:TAC:adt
(5 copies sent)
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 11
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
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SUMMARY LOGS OF EXPLORATORY BORINGS
CITY OF FORT COLLINS
FORT COLLINS POLICE ADMINISTRATION FACILITY
PROJECT NO. FC03384-115
20112
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.NATIONS, LIMITATIONS AND CONCLUSIONS
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CITY OF FORT COLLINS
FORT COLLINS POLICE ADMINISTRATION FACILITY
PROJECT NO. FC03364-115
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APPENDIX A
LABORATORY TEST RESULTS
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
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PROJECT NO. FC03384-115
10 100
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MOISTURE CONTENT= 10.3 %
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PROJECT NO. FC03384-115
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Test Results FIGURE A - 2
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PROJECT NO. FC03384-115
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APPENDIX B
GUIDELINE SITE GRADING SPECIFICATIONS
POLICE ADMINISTRATION FACILITY
Fort Collins, Colorado
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
GUIDELINE SITE GRADING SPECIFICATIONS
POLICE ADMINISTRATION FACILITY
Fort Collins, Colorado
1. DESCRIPTION
This item shall consist of the excavation, transportation, placement and
compaction of materials from locations indicated on the plans, or staked by the
Engineer, as necessary to achieve preliminary street and overlot elevations.
These specifications shall also apply to compaction of excess cut materials that
may be placed outside of the subdivision and/or filing boundaries.
2. GENERAL
The Soils Engineer shall observe fill materials, method of placement,
moisture contents and percent compaction, and shall provide written opinions
of the completed fill.
3. CLEARING JOB SITE
The Contractor shall remove all trees, brush and rubbish before
excavation or fill placement begins. The Contractor shall dispose of the cleared
material to provide the Owner with a clean, neat appearing job site. Cleared
material shall not be placed in areas to receive fill or where the material will
support structures of any kind.
4. SCARIFYING AREA TO BE FILLED
All topsoil and vegetable mattershall be removed from the ground surface
upon which fill is to be placed. The surface shall then be plowed or scarified
until the surface is free from ruts, hummocks or other uneven features, which
would prevent uniform compaction by the equipment to be used.
5. COMPACTING AREA TO BE FILLED
After the foundation for the fill has been cleared and scarified, it shall be
disked or bladed until it is free from large clods to a depth of 8 to 12 inches,
brought to the proper moisture content (0 to 3 percent above optimum moisture
content) and compacted to not less than 95 percent of maximum dry density as
determined in accordance with ASTM D 698.
CITY OF FORT OPETIONS SERVICE
FORT COLLINS OL ILINS CE ADMINNIISTRATIO FACILITY DEPARTMENT Appendix B-1
CTL I T PROJECT NO. FC03384-1 I5
0
6. FILL MATERIALS
Fill soils shall be substantially free from vegetable matter or other
deleterious substances, and shall not contain rocks or lumps having a diameter
greater than six (6) inches. Fill materials shall be obtained from cut areas
shown on the plans or staked in the field by the Engineer.
On -site materials classifying as CL, CH, SC, SM, SW and SP are
acceptable. Concrete, asphalt, organic matter and other deleterious materials
or debris shall not be used as fill.
7. MOISTURE CONTENT
For fill material classifying as CH, CL or SC, the fill shall be moisture
treated to between 0 and 3 percent above optimum moisture content. Soils
classifying as SM, SW, SP, GP, GC and GM shall be moisture treated to within
+2 percent of optimum moisture content as determined from Proctor
compaction tests. Sufficient laboratory compaction tests shall be made to
determine the optimum moisture content for the various soils encountered in
borrow areas.
The Contractor may be required to add moisture to the excavation
materials in the borrow area if, in the opinion of the Soils Engineer, it is not
possible to obtain uniform moisture content by adding water on the fill surface.
The Contractor may be required to rake or disc the fill soils to provide uniform
moisture content through the soils.
The application of water to embankment materials shall be made with any
type of watering equipment approved by the Soils Engineer, which will give the
desired results. Water jets from the spreader shall not be directed at the
embankment with such force that fill materials are washed out.
Should too much water be added to any part of the fill, such that the
material is too wet to permit the desired compaction from being obtained,
rolling and all work on that section of the fill shall be delayed until the material
has been allowed to dry to the required moisture content. The Contractor will
be permitted to rework wet material in an approved manner to hasten its drying.
8. COMPACTION OF FILL AREAS
Selected fill material shall be placed and mixed in evenly spread layers.
After each fill layer has been placed, it shall be uniformly compacted to not less
than the specified percentage of maximum density. Fill shall be compacted to
at least 95 percent of the maximum density as determined in accordance with
ASTM D 698. At the option of the Soils Engineer, soils classifying as SW, GP,
GC, or GM may be compacted to 95 percent of maximum density as determined
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT FORT COLLINS POLICE ADMINISTRATION FACILITY Appendix Pendix B-2
CTL I T PROJECT NO. FC03384-115
IF
in accordance with ASTM D 1557 or 70 percent relative density for cohesionless
sand soils. Fill materials shall be placed such that the thickness of loose
materials does not exceed 10 inches and the compacted lift thickness does not
exceed 6 inches.
Compaction as specified above, shall be obtained by the use of
sheepsfoot rollers, multiple -wheel pneumatic -tired rollers, or other equipment
approved by the Engineer for soils classifying as CL, CH, or SC. Granular fill
shall be compacted using vibratory equipment or other equipment approved by
the Soils Engineer. Compaction shall be accomplished while the fill material is
at the specified moisture content. Compaction of each layer shall be
continuous over the entire area. Compaction equipment shall make sufficient
trips to ensure that the required density is obtained.
9. COMPACTION OF SLOPES
Fill slopes shall be compacted by means of sheepsfoot rollers or other
suitable equipment. Compaction operations shall be continued until slopes are
stable, but not too dense for planting, and there is not appreciable amount of
loose soils on the slopes. Compaction of slopes may be done progressively in
increments of three to five feet (3' to 51) in height or after the fill is brought to its
total height. Permanent fill slopes shall not exceed 3:1 (horizontal to vertical).
10. PLACEMENT OF FILL ON NATURAL SLOPES
Where natural slopes are steeper than 20 percent in grade and the
placement of fill is required, cut benches shall be provided at the rate of one
bench for each 5 feet in height (minimum of two benches). Benches shall be at
least 10 feet in width. The Engineer may require larger bench widths. Fill shall
be placed on completed benches as outlined within this specification.
11. DENSITY TESTS
Field density tests shall be made by the Soils Engineer at locations and
depths of his choosing. Where sheepsfoot rollers are used, the soil may be
disturbed to a depth of several inches. Density tests shall be taken in
compacted material below the disturbed surface. When density tests indicate
that the density or moisture content of any layer of fill or portion thereof is
below that required, the particular layer or portion shall be reworked until the
required density or moisture content has been achieved.
CITY OF FORT COLLINS FORT COLLINS POLICE ADMINISTRATION FACILITY ATIONS SERVICE ARTMEN7
Appendix B-3
CTL I T PROJECT NO. FC03394-115
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12. SEASONAL LIMITS
No fill material shall be placed, spread or rolled while it is frozen, thawing,
or during unfavorable weather conditions. When work is interrupted by heavy
precipitation, fill operations shall not be resumed until the Soils Engineer
indicates that the moisture content and density of previously placed materials
are as specified.
13. NOTICE REGARDING START OF GRADING
The Contractor shall submit notification to the Soils Engineer and Owner
advising them of the start of grading operations at least three (3) days in
advance of the starting date. Notification shall also be submitted at least 3 days
in advance of any resumption dates when grading operations have been
stopped for any reason other than adverse weather conditions.
14. REPORTING OF FIELD DENSITY TESTS
Density tests made by the Soils Engineer, as specified under "Density
Tests" above, shall be submitted progressively to the Owner. Dry density,
moisture content, and percentage compaction shall be reported for each test
taken.
15. DECLARATION REGARDING COMPLETED FILL
The Soils Engineer shall provide a written declaration stating that the site
was filled with acceptable materials, and was placed in general accordance with
the specifications.
CITY OF ORTCOLLINS CPOLLINS ICEADMINSIONS SERVICE TRATIO FACILITY DEPARTMENT Appendix B-4
CTL I T PROJECT NO. FC03384-115
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City of Fort Collins
ADDENDUM N
SPECIFICATIONS AND CONTRACT DOCUMENTS
Description of Bid: P954 Police Services Facility — Design/Build
OPENING DATE: 3:00 P.M. (Our Clock) December 13, 2004
To all prospective bidders under the specifications and contract documents described above,
the following changes are hereby made.
A. RESPONSES TO QUESTIONS
1. Please confirm that the District 1 program areas on page 8 of the Needs Assessment
are not included in the building with the exception of the community room and bicycle
storage.
The District 1 program area, including their community room and bicycle storage will
remain off -site.
2. If an uninterrupted power supply (UPS) system is required for the facility, does the
Design/Build Team need to include it in our GMP, or will the City provide it as part or
your equipment budget? If so, what size should be anticipated?
An UPS system is required and it is to be included in your GMP. The size is
something we will rely upon the Police Architect to guide the determination.
LEDGED
A WRITTEN
ENCLOSEDF DDENDUM
QUOTEBSTAT STATING `THAT THISYADDENDUM STATEMENT
THISHAS BEEN
RECEIVED.
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I N C O! P O p♦ 7 i C
PRELIMINARY
GEOTECHNICAL INVESTIGATION
FORT COLLINS POLICE
ADMINISTRATION FACILITY
TIMBERLINE ROAD
NORTH OF DRAKE ROAD
FORT COLLINS, COLORADO
Prepared for:
CITY OF FORT COLLINS
OPERATIONS SERVICE DEPT.
PO Box 580
117 North Mason
Fort Collins, Colorado 80522-0580
Attention: Mr. Ron Ketcher
Project NO. FC03384-115
November 19, 2004
375 E. Horsetooth Road I The Shores Office Park I Building 3, Suite 100 1 Ft. Collins, Colorado 80525
Telephone:970-206-9455 Fax:970-206-9441
TABLE OF CONTENTS
SCOPE
SUMMARY OF FINDINGS AND CONCLUSIONS
SITE CONDITIONS
PROPOSED DEVELOPMENT
PREVIOUS INVESTIGATIONS
SUBSURFACE CONDITIONS
Fill
Natural Clay
Natural Sand, Gravel and Cobble
Bedrock
Ground Water
Seismicity
ESTIMATED SWELLICOLLAPSE RISK
SITE DEVELOPMENT
Fill Placement
Utility Construction
Pavement
BUILDING CONSTRUCTION
Foundations
Below -Grade Construction
Slabs -on -Grade and Basement Floor Construction
Concrete
Surface Drainage
RECOMMENDED FUTURE INVESTIGATIONS
LIMITATIONS
FIGURE 1 - LOCATIONS OF EXPLORATORY BORINGS
FIGURES 2 AND 3 — SUMMARY LOGS OF EXPLORATORY BORINGS
APPENDIX A - LABORATORY TEST RESULTS
APPENDIX B - GUIDELINE SITE GRADING SPECIFICATIONS
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384.115
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SCOPE
This report presents the results of our Preliminary Geotechnical Investigation
for the proposed City of Fort Collins Police Administration Facility to be located to the
west of Timberline Road, approximately 1,000 feet north of Drake Road in Fort Collins,
Colorado (Figure 1). This investigation was conducted to evaluate the subsurface
conditions and to provide judgments on conditions that will likely impact
development and construction at the site. The report includes descriptions of
subsurface conditions found in exploratory borings and discussion of site
development as influenced by geotechnical considerations.
The discussions in this report are based on our understanding of the planned
development, subsurface conditions disclosed by previous investigations and
exploratory drilling, site observation, results of laboratory tests, engineering analysis
of field and laboratory data and our experience. The criteria presented in the report
are intended for planning purposes. Additional, site -specific investigations will be
required to design building foundations, floor systems and pavements.
SUMMARY OF FINDINGS AND CONCLUSIONS
1. The subsurface conditions across the site generally consisted of 15 to 22
feet of sandy clay over 7 to 14 feet or more of clean to silty sand with gravel
and cobbles underlain by claystone bedrock. Clay fill was encountered in
one boring (TH-102) to a depth of about 6 feet. Clay samples showed
consolidation or low swell. The sand is judged non -expansive.
2. Ground water was encountered at depths of 23 to 26 feet. Ground water
will likely complicate installation of drilled piers (if selected). At this time,
we do not believe ground waterwill affect the performance of the proposed
building, unless an unusually deep basement is selected.
3. Footings, a reinforced mat, or drilled pier foundations are considered
feasible for the proposed structure. The choice of foundations will depend
on the load condition and configuration of the structure. A design level
geotechnical investigation should be conducted after plans are more
defined.
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT 1 FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384-115
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4. Based upon the preliminary data, we believe a slab -on -grade basement
floor could be used for the structure if risk of movement is acceptable. A
structurally -supported floor system should be considered if movement is
unacceptable. The potential magnitude of slab movement should be more
thoroughly defined during the design level geotechnical investigation.
S. We anticipate the near surface clay soils will provide fair to poor pavement
support qualities. We estimate parking lots and access roads will be paved
with a section equivalent to 4 to 6 inches of asphalt concrete over 6 to 12
inches of aggregate base course. Swell mitigation may be required. A
subgrade investigation and pavement design should be performed after
improvements have been sited.
6. Control of surface drainage will be critical to the performance of
foundations, slabs -on -grade and pavements. Surface drainage should be
designed to provide rapid removal of surface runoff away from structures.
Water should not be allowed to pond on or adjacent to pavements.
SITE CONDITIONS
The site is located about 1,000 feet north of Drake Road on the west side of
Timberline Road in Fort Collins, Colorado (Figure 1). The site is agricultural land that
is currently fallow. The Sidehill Subdivision is underdevelopment to the east, across
Timberline Road; other surrounding parcels are undeveloped. An irrigation ditch with
concrete flumes crosses the north portion of the site from west to east. The ditch
was not in operation at the time of our investigation. South of the ditch, near the
center of the eastern edge of the site, several large cottonwood trees stand in an area
with lush green grass. The remainder of the site was vegetated with stumps of corn
stalks, weeds and native, drought tolerant grasses. Topographic relief across the site
is approximately 5 to 10 feet; the northeast portion of the site is the high point. The
site slopes very gently to the south.
PROPOSED DEVELOPMENT
Plans are conceptual at this time. We understand the Police Administration
Facility is envisioned as a two or three-story structure with a basement, enclosing
approximately 93,000 square feet of floor area. The building may include a community
room, crime lab, offices and detention cells. Paved parking for about 330 vehicles
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT
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FORT COLLINS POUCE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384.115
and access drives will be included. The location of the building on the site has not
been finalized and development and overlot grading plans were not available. We
anticipate cuts and fills of less than 5 feet.
PREVIOUS INVESTIGATIONS
CTL I Thompson, Inc. has conducted two previous investigations on this site
as part of larger projects. A Geologic and Preliminary Geotechnical Investigation was
performed for the Cumberland Parcel that included this site (Project No. FC-1447,
report dated July 28, 2000). Permission to use data from that report was provided by
the Cumberland Company. We are also conducting a Geotechnical Investigation for
the widening of Timberline Road (Project No. FC03289, report pending). Borings
drilled in the area of the Police Facility site from these previous and concurrent
investigations are included on Figure 3.
SUBSURFACE CONDITIONS
Subsurface conditions were investigated by drilling four borings (TH-101
through TH-104) at the locations shown on Fig.1. Borings were drilled to depths of
35 to 40 feet using a truck -mounted drill rig and 4-inch diameter, continuous flight
auger or 6-inch diameter, hollow -stem auger. Our field representative observed the
drilling operations, logged the soils and obtained samples for laboratory testing.
Summary logs of the soils found in the borings and results of field penetration
resistance tests are presented on Figures 2 and 3. Samples obtained during drilling
were returned to our laboratory where they were visually classified and samples
selected for testing. The results of laboratory testing are presented in Appendix A
and summarized on Table A -I.
The subsurface conditions across the site generally consisted of 15 to 22 feet
of sandy clay over 7 to 14 feet or more of clean to silty sand underlain by claystone
bedrock. Clay fill was encountered in one boring (TH-102) to a depth of about 6 feet.
The engineering characteristics of the subsoils and bedrock encountered are
described in the following paragraphs.
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENTS
FORT COLLINS POLICE ADMINISTRATION FACILITY
CTL I T PROJECT NO. FC03384.1IS
IF
Fill
Clay fill was found in test hole TH-102 to a depth of about 6 feet. The origin of
the fill is unknown, but it may be from agricultural development or other unknown
sources. Existing fill may be encountered in other portions of the site during design
level investigations or site grading. The presence of undocumented fill presents a
risk of settlement or heave to structures. We recommend existing fill be removed. Fill
soils can be used as new fill provided the material is substantially free of organics,
debris or other deleterious material.
Natural Clay
Natural sandy clay was encountered in the eight borings drilled on this site.
The depth of the clay ranged from about 15 to 22 feet. The upper several feet of clay
was observed to be slightly moist and brown in color, deeper clay samples were
moist to very moist and reddish brown. Field penetration resistance testing indicated
the clay was medium stiff to very stiff. Six samples of clay were tested for swell -
consolidation and indicated compression to low swell (-1.7 percent compression to
0.5 percent swell) after wetting under a 1,000-psf load. One sample from a previous
investigation (test hole TH-16 at a depth of 4 feet, Project No. FC-1447) indicated
collapse of 10.6 percent after wetting. Some of the recent samples were observed to
have low density or porous structure.
Natural Sand, Gravel and Cobble
Sand, with gravel and cobbles, was encountered in all eight test holes below
the clay. The sand was medium dense to very dense. We consider the sand to be
non -expansive. The size of the cobble was difficult to quantify but they were large
enough to cause drill refusal of the exploratory borings. Cobbles up to about 12
inches should be anticipated.
CITY OF FORT COLLINS OPERATIONS SERVICE DEPARTMENT
FORT COLLINS POLICE ADMINISTRATION FACILITY 4
CTL I T PROJECT NO. FC03384-115