HomeMy WebLinkAboutAFFINITY AT FORT COLLINS - PDP - PDP150010 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
June 10, 2015
Inland Group
1620 North Mamer Road, Building B
Spokane, Washington 99203
Attn: Mr. Mark Ossello (marko@inlandconstruction.com)
Re: Subsurface Exploration Report – Addendum No. 2
Proposed Affinity at Fort Collins Apartments
2600 East Harmony Road
Fort Collins, Colorado
EEC Project No. 1142094
Mr. Ossello:
Earth Engineering Consultants, LLC (EEC) conducted a subsurface exploration study for the
Affinity at Fort Collins Apartment Development project at the referenced site in December of
2014. For further information, please refer to our “Subsurface Exploration Report” dated
December 15, 2014, EEC Project No. 1142094. As requested, EEC personnel recently
completed a supplemental subsurface exploration associated with the on-site detention ponds as
presented on the enclosed site diagrams.
Enclosed, herewith, are the results of the supplemental subsurface exploration completed by EEC
personnel for the two (2) detention ponds situated along the northern an eastern boundaries of the
subject site. For this phase of the project three (3) additional borings, (converted to short term/2-
week duration piezometers), were located and drilled within the proposed detention ponds as
shown on the enclosed site diagram. This supplemental study was completed in general
accordance with our proposal dated May 19, 2015.
EXPLORATION AND TESTING PROCEDURES
The supplemental detention pond related test borings were located in the field by representatives
of EEC by pacing and/or estimating locations relative to identifiable site features. The
approximate boring locations are indicated on the attached boring location diagram. The ground
surface elevations were based on surveyed information relevant to a temporary benchmark
TBM), which consisted of the northwest bonnet bolt of the fire hydrant located within the cul-de-
sac roadway alignment as shown on the enclosed site diagram. An assumed elevation of 100.00
was applied to the TBM. The location of the borings and surveyed information should be
considered accurate only to the degree implied by the methods used to make the field
measurements.
Earth Engineering Consultants, LLC
EEC Project No. 1142094
June 10, 2015
Page 2
The borings were completed using a truck mounted, CME-55 drill rig equipped with a hydraulic
head employed in drilling and sampling operations. For this study, as shown on the enclosed site
diagram, three (3) test borings were extended to depths of approximately 20-1/2 to 25-feet below
site grades, (i.e., PZ-1 through PZ-3). Upon completion of the drilling operations the borings
were converted to short-term piezometers via hand/field slotted PVC casings installed in each
borehole. Groundwater measurements were recorded the day of drilling, the following day, (i.e.,
24 hours after drilling), then a supplemental time period on June 9, 2015. The PVC casings
were then removed after the final groundwater measurements were recorded as per the State of
Colorado – Division of Water Resources guidelines.
SUBSURFACE CONDITIONS
In summary, the soils encountered within the three (3) supplemental detention pond borings
completed on this site generally consisted of moderately plasticity lean clay with sand and/or
sandy lean clay subsoils, which extended to the depths explored. Groundwater was observed in
the completed test borings/short-term piezometers at approximate depths of 14-1/2 to 16-1/2 feet
below existing site grades.
As part of our supplemental geotechnical engineering assessment we prepared a groundwater
contour map, included in the Appendix of this report, based on the final groundwater level
readings obtained. The contour elevations were based on the approximate ground surface
elevations at each boring location, and the approximate depth at which water was encountered on
June 9, 2015. As shown on the Groundwater Contour Map, the hydrologic gradient/piezometric
surface flow of measureable amount of water is in the northeast direction. The groundwater
contour map presented herein on approximate 1-foot interval is for illustration purposes only;
variations may exist between boring locations across the site.
ANALYSIS AND RECOMMENDATIONS
We understand these areas are site are planned as detention ponds. Subsurface conditions within
the planned detention pond areas in general consisted of cohesive lean clay with sand and sandy
lean clay subsoils. Groundwater was encountered at approximate depths of 14-1/2 to 15-1/2 feet
below existing site grades.
Detention ponds are typically designed to collect surface water, pavement and roof runoff for the
project as a temporary “holding basin” over time and eventually discharge the water into the
PZ-1 PZ-2
PZ-3
[97.6] [96.3]
[97.5]
(82.1) (81.3)
(83.0)
81
82
83
TBM
Groundwater Contour Diagram
Affinity of Fort Collins
Fort Collins, Colorado
EEC Project #: 1142094 Date: May 2015
EARTH ENGINEERING CONSULTANTS, LLC
PZ-1 thru PZ-3: Approximate
Locations for 3 Groundwater
3LH]RPHWHUV'ULOOHG
Legend
Approximate Ground Surface
Elevation
[ ]
Approximate Groundwater
Elevation
( )
Estimated Groundwater
Contours
Direction of Groundwater
Flow
NW Bonnet Bolt of Fire
Hydrant in Cul-de-sac,
Assume Elevation - 100'
TBM
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits 3
_ _
4
_ _
SS 5 8 9000+ 11.3 37 21 86.5
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 15 9000+ 11.4
_ _
11
_ _
12
_ _
13
_ _
14
brown / tan _ _
SS 15 6 3000 20.5
_ _
16
_ _
17
_ _
18
_ _
19
SILTY CLAYEY SAND (SM/SC) _ _
brown SS 20 7 -- 22.6
loose _ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
AFFINITY OF FORT COLLINS
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits 3
_ _
4
_ _
SS 5 7 9000+ 10.8
_ _
6
_ _
7
_ _
8
_ _
9
with traces of gravel _ _
SS 10 5 9000+ 10.4 35 20 62.9
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 6 3500 20.8
_ _
16
_ _
17
_ _
18
_ _
19
LEAN CLAY (CL) _ _
with gravel / rock seams SS 20 50/7" -- 12.6
_ _
BOTTOM OF BORING DEPTH 20.5' 21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
AFFINITY OF FORT COLLINS
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION D N QU MC DD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
TOPSOIL & VEGETATION _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
very stiff to stiff _ _
with calcareous deposits 3
_ _
4
_ _
SS 5 10 7000 10.7
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 5 9000+ 11.1
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 6 3000 19.6
_ _
16
_ _
17
_ _
18
_ _
19
_ _
*classified as LEAN CLAY (CL) SS 20 15 8000 19.2 45 30 90
_ _
21
_ _
22
_ _
23
_ _
24
_ _
SS 25 22 -- 17.6
BOTTOM OF BORING DEPTH 25.5' _ _
Earth Engineering Consultants, LLC
AFFINITY OF FORT COLLINS
FORT COLLINS, COLORADO
PROJECT NO: 1142094 LOG OF BORING PZ-3 JUNE 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 6/1/2015 WHILE DRILLING 16.0'
APPROX. SURFACE ELEV 97.5 When Checked 6-8-15 14.6'
FINISH DATE 6/1/2015 24 HOUR 15.0'
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1142094 LOG OF BORING PZ-2 JUNE 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 6/1/2015 WHILE DRILLING 15.5'
APPROX. SURFACE ELEV 96.3 When Checked 6-8-15 15.0'
FINISH DATE 6/1/2015 24 HOUR 15.2'
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1142094 LOG OF BORING PZ-1 JUNE 2015
SHEET 1 OF 1 WATER DEPTH
START DATE 6/1/2015 WHILE DRILLING 15'
APPROX. SURFACE ELEV 97.6 When Checked 6-8-15 15.5'
FINISH DATE 6/1/2015 24 HOUR 15.6'
A-LIMITS SWELL