HomeMy WebLinkAboutNORTHFIELD FILING 1 EXPANDED - FDP190012 - SUBMITTAL DOCUMENTS - ROUND 1 - STORMWATER-RELATED DOCUMENTSJune 25, 2019
Jason T. Claeys, P.E.
Highland Development Services, Inc.
6341 Fairgrounds Avenue, Suite 100
Windsor, CO 80550
RE: Northfield Development, Fort Collins, Colorado – Groundwater Evaluation
Dear Mr. Claeys:
This letter presents our groundwater evaluation for the Northfield development in Fort Collins, Colorado.
This report is organized according to the list of information requirements specified in Section 5.6.2.A of the
Larimer County Urban Areas Street Standards (LCUASS).
Information Relied On
Earth Engineering Consultant (EEC) report titled: Preliminary subsurface exploration and
groundwater report, Schlagel property, North of East Vine Drive and west of North Lemay Avenue,
Fort Collins, Colorado. EEC Project No. 1172056, Prepared for Landmark Homes, Prepared by Earth
Engineering Consultants, LLC , 4396 Greenfield Drive Windsor, Colorado. Report dated August 16,
2017.
Follow-up water level measurements provided by EEC and Miller Groundwater personnel, and field
testing conducted by Miller Groundwater.
Geologic Map of the lower Cache La Poudre River Basin, North-Central Colorado, by Lloyd Hershey
and Paul Schneider, Jr., Dated 1972.
Public records providing geologic information and water levels in nearby wells available online from
the Colorado Division of Water Resources.
Professional experience in the immediate area.
(1) LCUASS #1 (Section 5.6.2.A). Site Location and description. Include locations of any irrigation ditches
and wetlands.
The site was also known as the Schlagel property and is located in Fort Collins, Colorado, west of North
Lemay Drive (aka Lindenmeier Road), north of East Vine Drive, and east of the Lake Canal (Figure 1). The
Lake Canal flows from southwest to northeast and borders the west side of the development. The canal
has a relatively wide and deep channel.
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In general terms, the subsurface at the site can be described as 2 to 5 ft of clayey sand or sandy clay
overlying a poorly graded (non-uniform) sand. The sand unit contains gravel and also notable amounts of
silt. Please see EEC report for further detail. A siltstone/claystone/sandstone bedrock was reached in five
of the nine EEC borings at a depth of about 18 to 20 ft below current grade. This bedrock is likely the
regional Pierre Shale bedrock and would be expected to have much lower permeability than the overlying
sand unit. Groundwater therefore flows in the sandy unit at the site and it is a relatively thin aquifer at this
location.
(2) LCUASS #2. Elevation of water table, direction of flow, flow rates, groundwater barriers, and
seasonal high water level.
2.1 Groundwater Monitoring and Seasonal Water Levels
Two monitoring wells and seven temporary piezometers were installed by EEC at the property in late July
2017. The locations are shown in Figure 1 of this report and in EEC’s installation report included here as
Attachment A. Groundwater levels were measured on several dates between July 2017 and June 2018
(Table 1). As shown in Figure 2, it appears that the summer levels measured in July 2017 and June 2018
and June 2019 are representative of seasonal high water levels. Of course other years could be different
from these years, but this data set covers three summers and shows strong consistency across those three
summers. These seasonal-high groundwater levels were found to range spatially from 3.5 to 7 ft below
current grade (Figures 2 and 3). At other times of year, the levels dropped to a range of 5.5 to 10 feet
below current grade (Figure 2).
Below the shallow clayey soils, the deeper sand unit at the site is where groundwater movement will occur.
The planned depth for the development’s underdrains is expected to place them in that sand. The
screened/slotted intervals of EEC’s monitoring wells and piezometers were also placed in this sand unit.
Miller Groundwater conducted slug tests on a few of the EEC wells and borings and one neighboring
monitoring well to estimate the likely permeability of this sand unit.
2.2 Elevation of Water Table and Direction of Groundwater Flow
Based on the seasonal water level plot (Figure 2), we have based our evaluation primarily on water levels
measured in Summer 2018. That data, combined with estimated current-grade elevations near the wells,
was used to construct the groundwater elevation contour plot (Figure 1). Groundwater appears to flow
from the northwest to the southeast . We suspect that is the prevailing regional gradient in the sandy
aquifer (part of the floodplain and alluvium of the Cache la Poudre River and Dry Creek) and that
groundwater ultimately flows sub-parallel along and toward the river.
The Lake Canal could have some influence on the groundwater direction, but the groundwater direction
appears to be the same outside of the canal season. Also, we are aware of groundwater level data
collected immediately to the northwest of the Lake Canal and that data set confirms the gradient and
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direction of groundwater up-gradient of the canal to be that shown in Figure 1. Furthermore, the canal’s
SW to NE orientation happens to align whatever influence it would have on the groundwater flow direction
with the apparent natural/regional direction.
2.3 Other LCUASS #2 Questions: Flow Rates and Groundwater Barriers
General Flow Rates. Estimates of the overall flow rates through the aquifer could be developed, if
requested, but we have not developed such an estimate since the relevance and context of that request is
not clear to us at this time.
Drain Inflow Rates. We have developed estimates for the inflow rate to the underdrains planned for the
site. As a first step, we performed slug testing on monitoring well MW-1, piezometers PZ-1, PZ-4, and PZ-5,
and on a monitoring well at a nearby property. Our test results for hydraulic conductivity (K) ranged from
4 to 40 ft/day. The model simulations presented in this report were based on K = 40 ft/day, which we
expect is the more reliable estimate. However, we also calibrated a second model using K = 4 ft/day and
checked several of our underdrain simulations with that lower K value. As expected from our experience,
we found that the inflow rates to the underdrains were of course lower with the lower K value, but that the
drain effectiveness (as measured by the drains lowering groundwater levels near them) was roughly similar
in the area of the drains and less effective only at a distance from the drains.
Using the aforementioned range in K values, our model’s projections for the underdrain inflow rate ranged
from about 5 gpm to 40 gpm under seasonally high summer water conditions. That range likely has an
uncertainty factor of at least 2x, higher or lower.
Groundwater Barriers. We are not aware of any groundwater barriers at the property. We do note that
clayey soils are found in the shallowest 5 ft at some wells, but this appears to be above the saturated zone.
We also note that the NECCO regional stormwater pipe/culvert is installed across the southern portion of
the property. We have not reviewed construction drawings from the NECCO, but it could conceivably affect
flow patterns in the shallowest part of the aquifer if that culvert is large and deep, and depending on what
kind of trench bedding and backfill was used for it.
Recommendation: We recommend that the excavation of the infiltration galleries and the underdrain
trenches be occasionally inspected to verify that the excavation has reached through the shallow clayey
soils and into the sand unit. The planned depth of those structures is expected to easily clear the shallow
clayey soils based on our current data, but it would be prudent to verify this in the as-built condition. Some
minor over-excavation, backfilled with gravel or coarse clean sand, would be recommended if it is not clear
that the drains and galleries penetrate the sand u nit by at least a one or two foot margin.
(3) LCUASS #3. Potential sources of groundwater. Include proximity to irrigation ditch systems.
Cache La Poudre River Alluvium. As mapped by Hurr and Schneider (1972), the property is located on flood
plain deposits of the Cache La Poudre River and Dry Creek. These deposits extend far up-gradient to the
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northwest and we are aware of some highly permeable portions of this aquifer about one mile to the
northwest. We expect groundwater flows into the property from the northwest through these relatively
permeable deposits.
We expect some portion of the seasonally higher water levels comes from seepage from the Lake Canal,
but it is unknown what portion. Presumably, due to its proximity, the Lake Canal could be a significant
driver of the difference between summer and winter water levels at the property, but it is also very
possible that seasonal water changes would be observed even without that canal considering that other
canals and reservoirs provide water to this sand unit at various distances to the northeast, north, and
northwest.
(4) LCUASS #4. Water Rights.
Miller Groundwater personnel are not experts in water rights. However, in our experience, these are the
issues we expect to be most relevant for groundwater at this development:
The subsurface drains planned for this particular property may be expected by the State Division of
Water Resources (DWR) to be permitted as “wells” (i.e., a dewatering system).
Dewatering of groundwater is permitted as long as the produced water is not used or consumed
(e.g., not used for irrigation and not significantly evaporated when exposed). In this case, we
understand the plan is to route the produced water completely underground and immediately into
the NECCO regional stormwater system that passes through the property. The NECCO system then
routes this water to the Cache La Poudre River (where the groundwater was eventually headed).
We expect that plan would be easily accepted and the permitted granted by DWR, but that is just
our opinion.
Owners of permitted wells located within 600 ft of the planned drains will be notified by DWR of
development’s request to permit the drain system. Those owners will have the opportunity to
object and request a hearing if they feel their well could be impacted.
In our reviews of the DWR database to date, we have found only one well permit shown to be located
potentially within 600 ft of the underdrains. The DWR database places that well in the Alta Vista
neighborhood to the south of the development. However, please note that we have often found those
locations to be approximated by DWR based simply on the center of the quarter-quarter section, and we
found no specific location information in the permit records. The well was permitted in 1961 and we found
no follow up information (such as change in owner or abandonment). In a cursory review of Larimer
County property records, we also found no current owner names in the Alta Vista neighborhood that have
the same name as the 1961 owner.
In any case, that 1961 well was permitted as a domestic well with a flow rate at only 10 gpm. With that low
flow rate, it is highly unlikely that the Northfield drain system would materially impact it. Finally, it is also
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my understanding that DWR performs the well search and the notification and that it isn’t your
responsibility. I provide this information to you simply to report what I have found.
(5) LCUASS #5. Other relevant subsurface information such as water ownership (water rights),
groundwater quality (contamination or other undesirable characteristics).
We are not aware of other relevant subsurface information for this property with respect to water rights or
water quality. That has not been part of our scope, but we are aware of no reason for it to be a concern.
(6) LCUASS #6. Potential future groundwater conditions.
Of course we cannot see the future, but we are not aware of major planned changes to the groundwater
conditions in the area of the property that would be negative. We are aware that a development has been
proposed for the property immediately across the Lake Canal to the northwest of the Northfield
development. We do not know the current status of that development. That development and the
Northfield’s own development could lead to the the typical changes in surface water runoff and irrigation
that come with development. However, increased surface water runoff or increased lawn irrigation is
expected to mainly affect shallow soils here and not the deeper sand aquifer at this site. If that proposed
development to the northwest were to install underdrains, it would presumably lower the water table
slightly at the Northfield development as well.
It is certainly possible that seasonal variations in the site’s groundwater levels would, in future years, be
either larger or smaller than was observed between Summer 2017 and Summer 2019, but we are not aware
of a reason to expect that these years were not typical or representative years. And, as noted before, the
seasonal rise was consistent across those three years.
One exception that comes to mind is if the condition of the Lake Canal’s bottom and sides were to change
in the future, or if its operations were to change. Such changes could lead to higher or lower summer rises
in the future than we have observed in the summers of 2017, 2018, and 2019. That could affect the portion
of the property along the canal.
Long-term monitoring of groundwater and canal conditions, and maintenance of the subsurface drain
system, is not within Miller Groundwater’s scope of work. We recommend, and must assume, that a
management entity will be given the duty and responsibility to maintain the subsurface drains planned for
the property and to monitor for any relevant changes in conditions either offsite or onsite.
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(7) LCUASS #7. Subsurface drainage recommendations, including its effects on all conditions, including
sensitive habitat.
Figure 3 is a map of estimated depth to water, from the current grade to the water table, based on the
model’s simulation of the water table conditions in Summer 2018. In other words, this is a current
conditions map.
Figure 4 is a map of estimated depth to water for the same Summer 2018 water conditions (no drains), but
from the new grade planned for the site. Note that this seemingly detailed map comes from subtracting a
relatively smooth and approximate water table map (Figure 1) from the detailed grading plan. While the
grading plan may have precision and accuracy, it should not be assumed that Figure 4 has this same level of
precision and accuracy since it is based in part on an estimated water table surface which was interpolated,
extrapolated, and simulated. Comparing Figure 4 to Figure 3 does provide, however, a useful illustration of
what is to be gained from the site grading plan by itself. This grading plan is the version provided by
Highland Services on June 24, 2019.
Figure 5 is map of projected depth to water after groundwater levels are lowered by the subsurface drains.
Comparing Figure 5 to Figure 4 illustrates the model-projected impact of the subsurface drains on depth to
water. The drain plan simulated in this model is based on the slightly revised version provided by Highland
Services on June 25, 2019. The approximate perforated drain locations are indicated in green on Figure 5.
Figure 6 is provided to illustrate the water table elevations and gradients as projected by the model with
the underdrains in place. Comparing Figure 6 to Figure 1 is another way to consider the effects of the
underdrains.
(8) LCUASS #8. Cone of Influence.
The cone of influence, also known as a cone of depression, refers to the change (drawdown) in
groundwater levels created by the drains. We used the groundwater model to simulate the water table
surface after it would be lowered by the drains (Figure 6), and we subtracted that surface from the water
table surface we simulated for Summer 2018 conditions (Figure 1). The results are shown in Figure 7.
Note: In our current model, we have assumed the canal seepage is at a fixed rate and would not increase
due to the effect of the drains. That can be a reasonable assumption depending on conditions between the
water table and the canal bottom. If, however, the canal leakage does increase due to the drains, then the
drawdown pattern we have shown northwest of the canal would be smaller than we have projected and
drawdown near the canal along its east side could also be smaller than projected (i.e., higher post-drain
water levels than projected near the canal).
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(9) LCUASS #9. Control Measures and Design.
Information for LCUASS Subsection 9 will be provided by Highland Services. Those items are not within our
scope of work.
(10) LCUASS #10. Professional Engineer’s Seal and Signature.
This report will be sealed only for LCUASS Items Number 1 through Number 8. Number 9 is the
responsibility of the civil design firm, Highland Services, Inc. Our seal indicates that this work was
performed with a standard of care and level of skill ordinarily exercised by a groundwater hydrologist and
engineer practicing under similar conditions.
Evaluation Method. We used a numerical groundwater flow model (MODFLOW-2000) as a tool in this
evaluation. As we have done here, we find that that surface and subsurface mapping combined with such a
model is an effective and efficient tool for organizing available data and evaluating primary questions in
subsurface drain layouts. Our mapping and the groundwater model’s construction remained relatively
simple, but provided a means to consider site geometric factors such as the sloping ground surface relative
to the sloping water table. The model enables us to test how the simulated water table surface could be
changed by various drain configurations. Such modeling is a very valuable tool, but the fact that a model
was used should not, by itself, suggest that there is certainty or precision in results.
Technical Limitations in Subsurface Evaluation and Design. Subsurface data is always limited in its spatial
coverage, and subsurface hydraulic testing produces only approximate results. Estimates and projections
about groundwater behavior therefore have inherent and unavoidable uncertainties. No one can provide
certainty. By using good, common, and accepted methods, we believe this work provide good and useful
guidance for expected site groundwater behavior, but actual performance may be different from projected
performance. Furthermore, the successful performance of drainage systems depends on additional factors
beyond the scope and control of Miller Groundwater Engineering and its personnel, such as drain and
trench materials, proper installation, and future maintenance. For all these reasons, the developer,
owners, and/or other site-management entities must ultimately assume the risks and responsibilities
associated with subsurface construction and subsurface drainage.
This evaluation is based on data available to Miller Groundwater Engineering at this time. The estimates
and opinions contained herein are reasonably well-founded and consistent with observed conditions at the
explored locations, but they may be revised if significant additional information becomes available.
SUMMARY
Two monitoring wells and seven temporary piezometers were installed across the Northfield property in
2017 (Figure 1). These were used to periodically measure groundwater levels. A seasonal high water level
appears to have been reached each of the three observed summers (Figure 2). We used Summer 2018
Figure 2. Depth to groundwater over time at Northfield monitoring points (in feet).
Date MW-1 MW-2 PZ-1 PZ-2 PZ-3 PZ-4 PZ-5 PZ-6 PZ-7
7/27/2017 3.8 5.3 4.7 4.6 5.1 5.0 6.0 6.8 7.2
9/19/2017 4.0 5.7 5.2 4.7 5.8 5.3 7.0 6.7 7.3
10/19/2017 4.0 5.6 5.0 4.6 5.9 5.1 7.1 6.6 7.3
2/12/2018 5.7 7.0 6.8 6.2 7.5 6.5 8.8 8.0 8.9
6/7/2018 3.7 5.2 4.4 4.6 4.4 5.3 5.1 7.2 7.0
2/15/2019 6.5 7.4 7.6 7.3 9.7
6/6/2019 3.8 5.5 4.5 4.4 5.3 6.9 7.5
0
1
2
3
4
5
6
7
8
9
10
6/1/2017 8/31/2017 11/30/2017 3/1/2018 6/1/2018 8/31/2018 11/30/2018 3/2/2019 6/1/2019 8/31/2019
Depth to Water (feet)
Date
MW-1
MW-2
PZ-1
PZ-2
PZ-3
PZ-4
PZ-5
PZ-6
PZ-7
6/25/2019 Miller Groundwater Engineering, LLC
JASON CLAEYS
JUNE 25, 2019
Attachment A
Preliminary Subsurface Exploration and Groundwater Report
provided by
Earth Engineering Consultants, Inc. (EEC)
PRELIMINARY SUBSURFACE EXPLORATION AND GROUNDWATER REPORT
SCHLAGEL PROPERTY
NORTH OF EAST VINE DRIVE AND WEST OF NORTH LEMAY AVENUE
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172056
Prepared for:
Landmark Homes
1170 West Ash Street Suite 100
Windsor, Colorado 80550
Attn: Mr. Jonathan Mosier (jmosier@mylandmarkhomes.net)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
4396 GREENFIELD DRIVE
WINDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
www.earth-engineering.com
August 16, 2017
Landmark Homes
1170 West Ash Street Suite 100
Windsor, Colorado 80550
Attn: Mr. Jonathan Mosier (jmosier@mylandmarkhomes.net)
Re: Preliminary Subsurface Exploration and Groundwater Report
Schlagel Property
North of East Vine Drive and West of North Lemay Avenue
Fort Collins, Colorado
EEC Project No. 1172056
Mr. Mosier:
Earth Engineering Consultants, LLC (EEC) personnel have completed the preliminary subsurface
exploration and the installation of the requested two (2) long-term groundwater monitoring wells
(MWs) and the seven (7) temporary piezometers (PZs) for the referenced project. The purpose of
our study was to provide preliminary geotechnical engineering recommendations as well as a
mechanism to measure and evaluate the groundwater fluctuations and characteristics across the
property. This subsurface exploration/groundwater study was completed in general accordance
with our electronic/e-mail agreement on May 15, 2017.
We understand that the approximately 55 acre Schlagel property will be developed for single-family
residential lots, including utility and interior roadway infrastructure. Foundation loads for the
proposed structures are anticipated to be light with continuous wall loads less than 2½ kips per
lineal foot and individual column loads less than 50 kips. Floor loads are expected to be less than
100 psf. Overall site development will also include construction of interior roadways designed in
general accordance with Larimer County Urban Area Standards (LCUASS) Pavement Design
Standards.
For this phase of the project we understand the installation of the requested two (2) MWs
(registered with the State of Colorado – Division of Water Resources) and seven (7) PZs, which will
assist the design team in evaluating the groundwater conditions on the property. The purpose of this
report is to describe the subsurface conditions encountered in the preliminary borings, analyze and
evaluate the test data and provide preliminary geotechnical recommendations concerning site
development.
Earth Engineering Consultants, LLC
EEC Project No. 1172056
Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property
Fort Collins, Colorado
August 16, 2017
Page 2
SITE EXPLORATION AND TESTING PROCEDURES
As part of this assessment, EEC personnel completed two (2) MWs and seven (7) PZs / soil borings
at the approximate locations as indicated on the site diagrams included with this report. The borings
were extended to depths of approximately 14 to 21-1/2 feet below existing site grades. Upon
completion of the drilling operations, the boreholes labeled herein as MW-1 and MW-2 were
converted to PVC cased monitoring wells while the boreholes labeled herein as PZ-1 through PZ-7
were converted to temporary hand/field slotted piezometers, for use to develop groundwater
characteristics. Results of the field and laboratory testing completed for this assessment are
included with this report.
The two (2) MW and seven (7) PZ locations were established in the field prior to drilling by EEC
personnel, with the assistance from Interwest Consulting Group, by use of a hand-held GPS unit and
by pacing from identifiable site features at locations accessible to our drilling equipment. The
boring locations are presented on the attached boring location diagram and the ground surface
elevations, as presented on the boring logs were provided by the project’s surveyor.
The soil borings were completed using a truck-mounted, CME 75 drill rig equipped with a
hydraulic head employed in drilling and sampling operations. The boreholes were advanced using
4-inch nominal ID hollow stem augers to maintain open boreholes for sampling and PVC
piezometer/pipe installation. Samples of the subsurface materials encountered were obtained using
the split barrel/Standard Penetration Test (SPT) and California barrel sampling procedures in
general accordance with ASTM Specifications D1586 and D3550, respectively.
In the split-barrel and California barrel sampling procedures, standard sampling spoons are driven
into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of
blows required to advance the split barrel sampler is recorded and is used to estimate the in-situ
relative density of cohesionless soils and, to a lesser degree of accuracy, the consistency of cohesive
soils and hardness of weathered bedrock. In the California barrel sampling procedure, relatively
intact samples are obtained in removable brass sampling sleeves. All samples obtained in the field
were sealed and returned to our laboratory for further examination, classification and testing.
After completing the drilling and sampling, and prior to removal of the hollow stem augers, PVC
casings were installed in the open boreholes through the hollow stem augers. The MWs were
constructed with 2-inch nominal diameter schedule 40 manufactured well screen and riser pipe. In
general, the MWs consisted of a 10-foot section of flush threaded slotted well screen to depths as
Earth Engineering Consultants, LLC
EEC Project No. 1172056
Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property
Fort Collins, Colorado
August 16, 2017
Page 3
indicated on the enclosed boring logs, with flush threaded solid riser pipe, as required, to extend the
MWs above ground surface elevations. The screened portion of the MWs were backfilled with
10/20 silica sand, with an approximate 2-foot bentonite plug/seal placed above the sand layer, and
then backfilled with a blend of the auger cuttings generated and bentonite to the existing ground
surface elevations. For the piezometers (PZs) a hand/field slotted 1-inch diameter PVC casing was
installed in each borehole. Cross-sectional schematics of the MW/PZ installations are indicated on
the attached boring logs.
The State of Colorado Division of Water Resources was notified of intent to construct monitoring
holes prior to beginning the field exploration. Copies of those notices with acknowledgement from
the State Engineer’s Office are available upon request. The well construction and test reports will
be provided to the Division of Water Resources including copies of the boring logs provided with
this report. If the monitoring wells (MWs) will remain in place longer than one year, it will be
necessary to notify the Division of Water Resources and complete registration of those wells.
Installation was completed by a licensed water well driller, (Drilling Engineers of Fort Collins), and
was completed in accordance with the water well construction rules from the Division of Water
Resources.
Laboratory testing completed on recovered samples included moisture content and visual
classification of the samples. Atterberg limits tests were completed on selected samples to evaluate
the soil’s plasticity. Washed sieve analyses were also completed on selected samples to evaluate
the grain size distribution of the subsurface materials encountered. The grain size distribution
samples were recovered in a standard split-barrel sampler so that any larger size materials in the
subsoils would be excluded from the test samples. Results of the outlined tests are indicated on the
attached boring logs and summary sheets.
As part of the testing program, all samples were examined in the laboratory by an engineer and
classified in accordance with the attached General Notes and the Unified Soil Classification System,
based on the soil’s texture and plasticity. The estimated group symbol for the Unified Soil
Classification System is indicated on the boring logs and a brief description of that classification
system is included with this report. Classification of the bedrock was based on visual and tactual
observation of disturbed samples and auger cuttings. Coring and/or petrographic analysis may
reveal other rock types.
Earth Engineering Consultants, LLC
EEC Project No. 1172056
Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property
Fort Collins, Colorado
August 16, 2017
Page 4
SITE AND SUBSURFACE CONDITIONS
Schlagel Property is located north of East Vine Drive and West of North Lemay Avenue in Fort
Collins, Colorado. The property is generally undeveloped with surficial topsoil and vegetation.
An EEC field engineer was on-site during drilling to direct the drilling activities and evaluate the
subsurface materials encountered. Field descriptions of the materials encountered were based on
visual and tactual observation of disturbed samples and auger cuttings. The boring logs included
with this report may contain modifications to the field logs based on results of laboratory testing
and engineering evaluation. Based on results of field and laboratory evaluation, subsurface
conditions can be generalized as follows.
Vegetation growth and topsoil was encountered at the surface of each boring. Underlying the
topsoil/vegetation layer was a zone of cohesive subsoils classified lean to fat clay with varying
amounts of sand and clayey sand to approximate depths of 2 to 5-1/2 feet. Underlying the cohesive
subsoils was a granular layer of poorly to well graded sand with silt and gravel extending to the
depths explored at approximately 14 to 21-1/2 feet or to underlying bedrock. Interbedded
sandstone/siltstone/claystone bedrock was encountered in several of the borings at depths ranging
from 17-1/2 to 20 feet below existing site grades. Bedrock was not encountered in boreholes
labeled PZ-2, PZ-3, PZ-5, and PZ-7 which extended to depths of approximately 14 to 19 feet below
site grades.
The near surface lean to fat clay with varying amounts of sand and sandy clay subsoils were
generally relatively moist and soft to very stiff or very loose to medium dense becoming more moist
and soft/compressible approaching groundwater. The essentially cohesive materials exhibited low
to moderate plasticity and generally low to moderate swell potential at current moisture and density
conditions. The underlying granular materials were generally medium dense to very dense with
depth and exhibited no swell potential. The sandstone/claystone/siltstone bedrock was moderately
hard to hard with increased depth and exhibited high swell potential at current moisture and density
conditions.
The stratification boundaries indicated on the boring logs represent the approximate locations of
changes in soil and bedrock types. In-situ, the transition of materials may be gradual and indistinct.
Earth Engineering Consultants, LLC
EEC Project No. 1172056
Preliminary Subsurface Exploration and Groundwater Report – Schlagel Property
Fort Collins, Colorado
August 16, 2017
Page 5
Groundwater Observations
Observations were made while drilling and after the completion of drilling to detect the presence
and level of free water. Subsequent groundwater measurements were also performed 24 hours after
drilling. Groundwater and/or the presence of a piezometric water surface, was generally observed
at depths ranging from approximately 3 to 7 feet below ground surface as indicated on the enclosed
boring logs. The measured depths to groundwater are recorded near the upper right hand corner of
each boring log included with this report. Groundwater measurements provided with this report are
indicative of groundwater levels at the locations and at the time the borings/groundwater
measurements were completed.
Perched and/or trapped water may be encountered in more permeable zones in the subgrade soils at
different times throughout the year. Perched water is commonly encountered in soils immediately
overlying less permeable clay zones or seams. Fluctuations in ground water levels and in the
location and amount of perched/trapped water may occur over time depending on variations in
hydrologic conditions, irrigation activities on this and surrounding properties and other conditions
not apparent at the time of this report.
As part of our geotechnical engineering assessment we prepared a groundwater contour map, based
on the water level reading measurements obtained 24 hours after drilling. The contour elevations
were based on the approximate ground surface elevations at each boring location and the
approximate depth at which water was encountered. As shown on the groundwater contour map,
the hydrologic gradient/piezometric surface flow is generally in the southeast direction. The
groundwater contour map presented herein is for illustration purposes only; variations may exist
between boring locations across the site.
ANALYSIS AND RECOMMENDATIONS
Swell/Consolidation Test Results
As a part of our laboratory testing, we conducted seven (7) swell/consolidation tests on samples of
the overburden cohesive subsoils. The swell index values for the samples analyzed generally
revealed low to moderate swell characteristics when inundated with water and pre-loaded at 500 psf
as well as exhibiting a slight tendency to hydro-compact and consolidate with increased loads.
Results of the laboratory swell tests are indicated below in Table I, on the attached boring logs, and
on the enclosed summary sheets.
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TABLE I - Swell Consolidation Test Results
Boring
No.
Depth,
ft.
Material Type
In-Situ Moisture
Content, %
Dry Density,
PCF
Inundation
Pressure, psf
Swell Index,
(+/-) %
MW-1 2 Clayey Sand (SC) 20.4 106.7 500 (-) 0.2
MW-2 2 Sandy Lean Clay (CL) 21.0 112.3 500 (-) 0.9
PZ-3 2 Clayey Sand (SC) 8.8 113.8 500 (+) 0.8
PZ-4 2 Sandy Lean Clay (CL) 19.5 99.1 500 (+) 2.1
PZ-5 2 Fat Clay with Sand (CH) 14.9 112.6 500 (+) 3.5
PZ-6 2 Clayey Sand (SC) 20.7 106.7 500 (-) 0.4
PZ-7 2 Lean Clay with Sand (CL) 20.6 110.7 500 (+) 0.3
The Colorado Association of Geotechnical Engineers (CAGE) uses the following information to
provide uniformity in terminology between geotechnical engineers to provide a relative correlation
risk performance to measured swell. “The representative percent swell values are not necessarily
measured values; rather, they are a judgment of the swell of the soil and/or bedrock profile likely to
influence slab performance.” Geotechnical engineers use this information to also evaluate the swell
potential risks for foundation performance based on the risk categories.
TABLE II: Recommended Representative Swell Potential Descriptions and Corresponding Slab Performance Risk
Categories
Slab Performance Risk Category Representative Percent Swell
(500 psf Surcharge)
Representative Percent Swell
(1000 psf Surcharge)
Low 0 to < 3 0 < 2
Moderate 3 to < 5 2 to < 4
High 5 to < 8 4 to < 6
Very High > 8 > 6
Based on the laboratory test results, the in-situ samples of overburden subsoils were generally in the
low to moderate risk range.
General Considerations
General guidelines are provided below for the site subgrade preparation. However, it should be
noted that compaction and moisture requirements vary between home builders and, consequently,
between geotechnical engineering companies. If the development lots will be marketed to a target
group of tract builders, fill placement criteria should be obtained from those builders and/or their
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engineers prior to beginning earthwork activities on the site. Representatives from those entities
should verify that the fill is being placed consistent with the home builders’ guide lines.
The near surface soils at the site were relatively moist and soft to very stiff at the time of drilling
and exhibited low to moderate potential to swell. If these soils were to become wetted subsequent
to construction of overlying improvements, heaving caused by those soils could result in significant
total and differential movement of site improvements. Therefore, to reduce the potential movement
of foundations, floor slabs and pavements, included herein are preliminary
considerations/recommendations for an over excavation and replacement concept, however to be
determined by the individual/lot-specific home builder.
Generally, an over excavation process involves removing a zone of expansive soils beneath site
improvements and replacing them with low to non-expansive engineered fill material or structural
fill. An over excavation and replacement process will not eliminate the possibility of foundation
and/or slab heave; but movements should be reduced and tend to be more uniform. Constructing
improvements on a site which exhibits potential for swelling is inherently at risk for post construction
heaving, causing distress of site improvements. The following recommendations provided within the
“Site Preparation Section” are to reduce the risk of post construction heaving; however, that risk
cannot be eliminated. If the owner does not accept that risk, we would be pleased to provide more
stringent recommendations.
If lower level construction or full-depth basements are being considered for the site, we would
suggest that the lower level subgrade(s) be placed a minimum of 4 feet above the maximum
anticipated rise in groundwater levels, or a combination exterior and interior perimeter drainage
system(s) be installed. Also, consideration could be given to 1) either designing and installing an
area underdrain system to lower the groundwater levels provided a gravity discharge point can be
established. If a gravity outlet/system cannot be designed another consideration would be to design
and install a mechanical sump pump system to discharge the collected groundwater within the
underdrain system, or 2) elevate/raise the site grades to establish the minimum required 4-foot
separation to the maximum anticipated rise in groundwater.
Site Preparation
All existing vegetation and topsoil should be removed from beneath site fills, roadways or building
subgrade areas. Stripping depths should be expected to vary, depending, in part, on past agricultural
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and/or site usage activities. Any soft native soils observed following over excavation should be
removed from improvement, backfill and fill areas. In addition, any soft/loose native soils or any
existing fill materials without documentation of controlled fill placement would generally require
removal from improvement and/or new fill areas. In areas where existing improvements are in-
place, those improvements and any associated fill soils should be completely removed prior to
placing overlying improvements or fill. Over excavation of expansive subgrade materials would
also likely be required in individual building areas; the specific extent of over excavation may vary
with different home builders. The extent and depth of material removal and replacement may also
be significantly impacted by site grading.
After stripping and completing all cuts, including the over excavation depths required by the lot-
specific home builders, and prior to placement of any fill, building improvements or pavements, the
exposed soils would likely be scarified to a minimum depth of 9 inches, adjusted in moisture
content and compacted to at least 95% of the material's maximum dry density as determined in
accordance with ASTM Specification D698, the standard Proctor procedure. The moisture content
of the scarified materials would be adjusted, potentially, to be within a range of 2% of standard
Proctor optimum moisture, at the time of compaction.
In general, fill materials required to develop the building areas or site pavement subgrades should
consist of approved, low-volume change materials which are free from organic matter and debris.
We believe the on-site lean clay with sand soils could be used as fill in these areas.
Approved low volume change fill soils would generally be placed in loose lifts not to exceed 9
inches thick, adjusted in moisture content and compacted to at least 95% of the material’s maximum
dry density as determined in accordance with the standard Proctor procedure. The moisture content
of predominately clay soils should be adjusted to be within the range of ± 2% of optimum moisture
content at the time of placement. Higher moisture contents may be required by individual home
builders. Care should be taken to develop relatively uniform fills and avoid placing “pockets” of
clean granular soils within predominately cohesive fill embankments.
Specific explorations should be completed for each building/individual residential lot to develop
recommendations specific to the proposed structure and owner/builder and for specific pavement
sections. A greater or lesser degree of compaction could be specified for specific individual
structures along with alternative moisture requirements. The preliminary recommendations
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provided in this report are, by necessity, general in nature and would be superseded by site specific
explorations/recommendations.
Care should be taken after preparation of the subgrades to avoid disturbing the subgrade materials.
Positive drainage should be developed away from structures and across and away from pavement
edges to avoid wetting of subgrade materials. Subgrade materials allowed to become wetted
subsequent to construction of the residences and/or pavements can result in unacceptable
performance of those improvements.
Foundation Systems – General Considerations
The cohesive subsoils will require particular attention in the design and construction to reduce the
amount of movement due to the in-situ soft/compressible characteristics. Groundwater was also
encountered at relatively shallow depths across the site which will require special attention in the
overall design and construction of the project. As previously mentioned consideration could be given to
the installation of an area underdrain system.
Spread footing foundation systems were evaluated for use on the site; however final subsurface
explorations should be performed after building footprints and elevations have been better defined and
actual design loads determined.
Preliminary Spread Footing Foundation Recommendations
We anticipate use of conventional footing foundations could be considered for lightly loaded
structures at this site. We expect footing foundations would be supported either on the native soils
or on newly placed and compacted fills. Soft zones were observed in the lean clay soils so that care
will be necessary to see that potential deeper foundations (i.e. basements) are not supported directly
on soft materials. Mitigation for soft subgrade soils should be expected over much of the site if
basements are considered. Additionally, a separation between the groundwater and the building
footings should be maintained.
In areas where the cohesive subsoils exhibited elevated moisture contents near and/or encroaching
the groundwater levels and/or where relatively low SPT N-Blows/ft. were recorded indicating “soft
soils” we would expect these soft zones would require particular attention/ground modification
procedures to develop increased support capacity characteristics. We expect enhancing/stiffening of
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the subgrade/bearing soils could be accomplished by incorporating into the soft/compressible
subsoils a layer of granular rock (i.e., 1-½ inches minus crushed concrete aggregate) into the top 12-
inches (+/-) of the subgrades as an initial means and method.
Depending on the proximity to groundwater and/or severity of the soft soils, consideration could be
given to a minimum 2-foot over excavation/backfill procedure beneath site structures in areas where
soft soils are expected. After completing a site-specific/lot-specific geotechnical exploration study,
a thorough “open-hole/foundation excavation” observation should be performed prior to foundation
formwork placement to determine the extent of any over excavation and replacement procedure.
Deeper over excavation depths may be necessary depending upon the observed subsoils at the time
of the foundation excavation observation. In general, the over excavation area would extend 8
inches laterally beyond the building perimeter for every 12 inches of over excavation depth. We
anticipate backfill materials would consist of an approved imported granular structural fill material
placed and compacted as outlined in the section “Site Preparation”.
For design of footing foundations bearing on approved native subsoils, (i.e., the native subsoils in
which soft/compressible conditions are not encountered), or on properly placed and compacted fill
materials as outlined above, maximum net allowable total load soil bearing pressures on the order of
1,500 to 2,500 psf could be considered depending upon the specific backfill material used. Footing
foundations should maintain separation above maximum anticipated rise in groundwater elevation
of at least 4 feet indicated earlier. The net bearing pressure refers to the pressure at foundation
bearing level in excess of the minimum surrounding overburden pressure. Total load would include
full dead and live loads.
Exterior foundations and foundations in unheated areas are typically located at least 30 inches
below adjacent exterior grade to provide frost protection. Formed continuous footings would have
minimum widths of 12 to 16 inches and isolated column foundations would have a minimum width
of 24 to 30 inches. Trenched foundations or grade beam foundations could probably be used in the
near surface soils. If used, trenched foundations would have a minimum width of 12 inches and
formed continuous foundations a minimum width of 8 inches.
Preliminary Floor Slab/Exterior Flatwork Subgrades
We recommend all existing vegetation/topsoil be removed from beneath the floor slab and exterior
flatwork areas as previously outlined. After stripping and completing all cuts and prior to
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placement of any flatwork concrete or fill, the exposed subgrades should be scarified, adjusted in
moisture content and compacted as outlined in the section “Site Preparation”. If the subgrades
become dry and desiccated prior to floor slab construction, it may be necessary to rework the
subgrades prior to floor slab placement.
Fill soils required to develop the floor slab subgrades should consist of approved, low-volume
change materials which are free from organic matter and debris. Those fill materials should be
placed as outlined in the section “Site Preparation”.
Preliminary Basement Design and Construction
Groundwater was encountered across the site within the preliminary soil borings at approximate
depths of 10 to 13 feet below existing site grades. If lower level construction for either garden-level
or full-depth basements is being considered for the site, we would suggest that the lower level
subgrade(s) be placed a minimum of 4-feet above maximum anticipated rise in groundwater levels,
or a combination exterior and interior perimeter drainage system(s) be installed.
Consideration could be given to 1) either designing and installing an area underdrain system to
lower the groundwater levels provided a gravity discharge point can be established. If a gravity
outlet/system cannot be designed another consideration would be to design and install a mechanical
sump pump system to discharge the collected groundwater within the underdrain system, or 2)
elevate/raise the site grades to establish the minimum required four (4) foot separation to the
maximum anticipated rise in groundwater. EEC is available to assist in the underdrain design if
requested.
The following information should also be considered, which as previously mentioned, would be to
install an interior and exterior perimeter drainage system for each individual residence. To reduce
the potential for groundwater to enter the lower level/basement area of the structure(s), installation
of a dewatering system is recommended. The dewatering system should, at a minimum, include an
underslab gravel drainage layer sloped to an interior perimeter drainage system. The following
provide preliminary design recommendations for interior and exterior perimeter drainage systems.
The underslab drainage system should consist of a properly sized perforated pipe, embedded in free-
draining gravel, placed in a trench at least 12 inches in width. The trench should be inset from the
interior edge of the nearest foundation a minimum of 12 inches. In addition, the trench should be
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located such that an imaginary line extending downward at a 45-degree angle from the foundation
does not intersect the nearest edge of the trench. Gravel should extend a minimum of 3 inches
beneath the bottom of the pipe. The underslab drainage system should be sloped at a minimum 1/8
inch per foot to a suitable outlet, such as a sump and pump system.
The underslab drainage layer should consist of a minimum 6-inch thickness of free-draining gravel
meeting the specifications of ASTM C33, Size No. 57 or 67 or equivalent. Cross-connecting
drainage pipes should be provided beneath the slab at minimum 15-foot intervals, and should
discharge to the perimeter drainage system.
Sizing of drainage pipe will be dependent upon groundwater flow into the dewatering system.
Groundwater flow rates will fluctuate with permeability of the soils to be dewatered and the depth
to which groundwater may rise in the future. Pump tests to determine groundwater flow rates are
recommended in order to properly design the system. For preliminary design purposes, the
drainage pipe, sump and pump system should be sized for a projected flow of 0.5 x 10-3 cubic feet
per second (cfs) per lineal foot of drainage pipe. Additional recommendations can be provided
upon request and should be presented in final subsurface exploration reports for each residential lot.
To reduce the potential for surface water infiltration from impacting foundation bearing soils and/or
entering any planned below grade portion of any residential structure, installation of an exterior
perimeter drainage system is recommended. This drainage system should be constructed around the
exterior perimeter of the lower level/below grade foundation system, and sloped at a minimum 1/8
inch per foot to a suitable outlet, such as a sump and pump system.
The exterior drainage system should consist of a properly sized 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 2 feet above the bottom of the foundation wall.
The system should be underlain with a polyethylene moisture barrier, sealed to the foundation
walls, and extended at least to the edge of the backfill zone. The gravel should be covered with
drainage fabric prior to placement of foundation backfill.
Lateral Earth Pressures
Elements of the residential structures constructed below grade may be subject to lateral earth
pressures. Passive lateral earth pressures may help resist the driving forces for retaining walls or
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other similar site structures. Active lateral earth pressures could be used for design of structures
where some movement of the structure is anticipated, such as retaining walls. The total deflection
of structures for design with active earth pressure is estimated to be on the order of one half of one
percent of the height of the down slope side of the structure. We recommend at-rest pressures be
used for design of structures where rotation of the walls is restrained, such as basement walls.
Passive pressures and friction between the footing and bearing soils could be used for design of
resistance to movement of retaining walls.
Typical coefficient values for backfill with anticipated types of soils for calculation of active, at rest
and passive earth pressures are provided in the table below. Equivalent fluid pressure is equal to the
coefficient times the appropriate soil unit weight. Those coefficient values are based on horizontal
backfill with backfill soils consisting of essentially on-site cohesive subsoils or approved imported
granular materials with friction angles of 25 and 35 degrees respectively. For the at-rest and active
earth pressures, slopes down and away from the structure would result in reduced driving forces
with slopes up and away from the structures resulting in greater forces on the walls. The passive
resistance would be reduced with slopes away from the wall. The top 30 inches of soil on the
passive resistance side of walls could be used as a surcharge load; however, should not be used as a
part of the passive resistance value. Frictional resistance is equal to the tangent of the friction angle
times the normal force.
Table III: Lateral Earth Pressure Coefficients
Soil Type On-Site Low Plasticity Cohesive
Subsoils
Imported Granular Structural Fill
Poorly Graded Sand (SM/SP)
Wet Unit Weight 115 135
Saturated Unit Weight 135 140
Friction Angle (ϕ) – (assumed) 25° 35°
Active Pressure Coefficient 0.40 0.27
At-rest Pressure Coefficient 0.58 0.43
Passive Pressure Coefficient 2.46 3.70
Surcharge loads or point loads placed in the backfill can also create additional loads on below grade
walls. Those situations should be designed on an individual basis. The outlined values do not
include factors of safety nor allowances for hydrostatic loads and are based on assumed friction
angles, which should be verified after potential material sources have been identified. Care should
be taken to develop appropriate drainage systems behind below grade walls to eliminate potential
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for hydrostatic loads developing on the walls. Those systems would likely include perimeter drain
systems extending to sump areas or free outfall where reverse flow cannot occur into the system.
Where necessary, appropriate hydrostatic load values should be used for design.
Preliminary Pavement Subgrades
All existing vegetation and/or topsoil and any soft or loose materials should be removed from
pavement areas. After stripping and completing all cuts and prior to placement of any fill or
pavements, we recommend the exposed soils be scarified to a minimum depth of 9 inches, adjusted
in moisture content and compacted to at least 95% of the material's maximum dry density as
determined in accordance with ASTM Specification D698, the standard Proctor procedure. The
moisture content of the scarified soils should be adjusted to be within the range of 2% of standard
Proctor optimum moisture.
Fill materials required to develop the pavement subgrades should consist of approved, low-volume
change materials, free from organic matter and debris. The near surface clayey sand and lean clay
with varying amounts of sand could be used for fill in these areas. We recommend those fill soils
be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted to
at least 95% of the material's standard Proctor maximum dry density.
After completion of the pavement subgrades, care should be taken to prevent disturbance of those
materials prior to placement of the overlying pavements. Soils which are disturbed by construction
activities should be reworked in-place or, if necessary, removed and replaced prior to placement of
overlying fill or pavements.
Depending on final site grading and/or weather conditions at the time of pavement construction,
stabilization of a portion of the site pavement subgrades may be required to develop a paving
platform. The site clayey soils could be subject to instability at higher moisture contents.
Stabilization could also be considered as part of the pavement design, although prior to finalizing
those sections, a stabilization mix design would be required.
Preliminary Site Pavements
Pavement sections are based on traffic volumes and subgrade strength characteristics. The lean clay
site soils have low remolded strength. An R-value of 10 would be appropriate for design of the
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pavements supported on the subgrade soils. Suggested preliminary pavement sections for the local
residential and minor collector roadways are provided below in Table IV. Thicker pavement
sections may be required for roadways classified as minor or major collectors. A final pavement
design thickness evaluation will be determined when a pavement design exploration is completed
(after subgrades are developed to ± 6 inches of design and wet utilities installed in the roadways).
The projected traffic may vary from the traffic assumed from the roadway classification based on a
site-specific traffic study.
TABLE IV – PRELIMINARY PAVEMENT SECTIONS
Local Residential
Roadways
Minor Collectors
Roadways
EDLA – assume local residential roadways
Reliability
Resilient Modulus
PSI Loss – (Initial 4.5, Terminal 2.0 and 2.3 respectively)
10
75%
3562
2.5
25
85%
3562
2.2
Design Structure Number 2.60 3.20
Composite Section without Fly Ash – Alternative A
Hot Mix Asphalt (HMA) Grading S (75) PG 58-28
Aggregate Base Course ABC – CDOT Class 5 or 6
Design Structure Number
4ʺ
8ʺ
(2.64)
5ʺ
9-1/2ʺ
(3.25)
Composite Section with Fly Ash – Alternative B
Hot Mix Asphalt (HMA) Grading S (75) PG 58-28
Aggregate Base Course ABC – CDOT Class 5 or 6
Fly Ash Treated Subgrade
Design Structure Number
4ʺ
6 ʺ
12″
(3.02)
4ʺ
8ʺ
12ʺ
(3.24)
PCC (Non-reinforced) – placed on an approved subgrade 6″ 7″
Asphalt surfacing should consist of grading S-75 or SX-75 hot bituminous pavement with PG 64-22
or PG 58-28 binder in accordance with LCUASS requirements. HMA should be compacted to
achieve 92 to 96% of the mix’s theoretical maximum specific gravity (Rice Value). Aggregate base
should be consistent with CDOT requirements for Class 5 or Class 6 aggregate base. A suggested
specification for stabilization of the subgrades with class C fly ash is included with this report.
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Underground Utility Systems
All piping should be adequately bedded for proper load distribution. It is suggested that clean, graded
gravel compacted to 70 percent of Relative Density ASTM D4253 be used as bedding. Where
utilities are excavated below groundwater, temporary dewatering will be required during excavation,
pipe placement and backfilling operations for proper construction. Utility trenches should be
excavated on safe and stable slopes in accordance with OSHA regulations as further discussed herein.
Backfill should consist of the on-site soils or approved imported materials. The pipe backfill should
be compacted to a minimum of 95 percent of Standard Proctor Density ASTM D698.
Water Soluble Sulfates – (SO4)
The water-soluble sulfate (SO4) testing of the on-site overburden and bedrock materials taken
during our subsurface exploration at varying depths are provided in Table V below. Based on the
reported sulfate content test results, this report includes a recommendation for the CLASS or TYPE
of cement for use for contact in association with the on-site subsoils and bedrock.
TABLE V - Water Soluble Sulfate Test Results
Sample Location Description Soluble Sulfate
Content (mg/kg)
Soluble Sulfate
Content (%)
PZ-1, S-1 at 2’ Well Graded Sand with Silt and Gravel (SW / SM) 2,660 0.27
PZ-3, S-2, at 4’ Sand / Gravel (SP / GP) 210 0.02
MW-2, S-5, at
19’
Sandstone / Siltstone / Claystone 770 0.08
Based on the results as presented in Table V above, ACI 318, Section 4.2 indicates the site
overburden soils generally have a low risk of sulfate attack on Portland cement concrete except for
the bedrock sample from PZ-1 at 2 feet below grade which indicated a high risk of sulfate attack.
Therefore Class 0 and/or Type I/II cement could be used, depending on location, for concrete on
and below site grade within the overburden soils and/or bedrock. In locations with high risk of
sulfate attack, Class 2 cement should be used. Foundation concrete should be designed in
accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. These results
are being compared to the following Table VI. Specific explorations should be completed for each
building/individual residential lot to develop recommendations specific to the proposed area,
structure and owner/builder.
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Table VI - Requirements to Protect Against Damage to Concrete by Sulfate Attack from External Sources of Sulfate
Severity of Sulfate
exposure
Water-soluble sulfate (SO4)
in dry soil, percent
Water-cement ratio,
maximum
Cementitious material
Requirements
Class 0 0.00 to 0.10% 0.45 Class 0
Class 1 0.11 to 0.20% 0.45 Class 1
Class 2 0.21 to 2.00% 0.45 Class 2
Class 3 2.01 of greater 0.45 Class 3
Other Considerations and Recommendations
Groundwater was observed at an approximate depth of 3 to 7 feet below present site grades.
Excavations extending to the wetter soils could create difficulties for backfilling of the utility/pipe
trenches with drying of the subgrade soils required to use those materials as backfill. In general, the
subgrade soils could be used as backfill soils although care will be necessary to maintain sufficient
moisture to reduce potential for post-construction movement.
Excavations into the on-site soils will encounter a variety of conditions. Excavations into the clays
can be expected to stand on relatively steep temporary slopes during construction; however, caving
soils may also be encountered especially in close proximity to the groundwater table. Groundwater
seepage should also be anticipated for utility excavations. Pumping from sumps may be utilized to
control water within the excavations. Well points may be required for significant groundwater
flow, or where excavations penetrate groundwater to a significant depth. The individual
contractor(s) should be made responsible for designing and constructing stable, temporary
excavations as required to maintain stability of both the excavation sides and bottom. All
excavations should be sloped or shored in the interest of safety following local and federal
regulations, including current OSHA excavation and trench safety standards.
Positive drainage should be developed away from the site structure(s) with a minimum slope of 1
inch per foot for the first 10 feet away from the building in landscaped areas. Flatter slopes could
be used in hardscape areas provided positive drainage is maintained. Potential settlement adjacent
to the structure should be considered when developing positive drainage.
GENERAL COMMENTS
The analysis and information presented in this report is based upon the data obtained from the soil
borings performed at the indicated locations as discussed in this report. This report does not reflect
any variations which may occur between boring or across the site. The nature and extent of such
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DRILLING AND EXPLORATION
DRILLING & SAMPLING SYMBOLS:
SS: Split Spoon ‐ 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample
ST: Thin‐Walled Tube ‐ 2" O.D., unless otherwise noted WS: Wash Sample
R: Ring Barrel Sampler ‐ 2.42" I.D., 3" O.D. unless otherwise noted
PA: Power Auger FT: Fish Tail Bit
HA: Hand Auger RB: Rock Bit
DB: Diamond Bit = 4", N, B BS: Bulk Sample
AS: Auger Sample PM: Pressure Meter
HS: Hollow Stem Auger WB: Wash Bore
Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2‐inch O.D. split spoon, except where noted.
WATER LEVEL MEASUREMENT SYMBOLS:
WL : Water Level WS : While Sampling
WCI: Wet Cave in WD : While Drilling
DCI: Dry Cave in BCR: Before Casing Removal
AB : After Boring ACR: After Casting Removal
Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated
levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not
possible with only short term observations.
DESCRIPTIVE SOIL CLASSIFICATION
Soil Classification is based on the Unified Soil Classification
system and the ASTM Designations D‐2488. Coarse Grained
Soils have move than 50% of their dry weight retained on a
#200 sieve; they are described as: boulders, cobbles, gravel or
sand. Fine Grained Soils have less than 50% of their dry weight
retained on a #200 sieve; they are described as : clays, if they
are plastic, and silts if they are slightly plastic or non‐plastic.
Major constituents may be added as modifiers and minor
constituents may be added according to the relative
proportions based on grain size. In addition to gradation,
coarse grained soils are defined on the basis of their relative in‐
place density and fine grained soils on the basis of their
consistency. Example: Lean clay with sand, trace gravel, stiff
(CL); silty sand, trace gravel, medium dense (SM).
CONSISTENCY OF FINE‐GRAINED SOILS
Unconfined Compressive
Strength, Qu, psf Consistency
< 500 Very Soft
500 ‐ 1,000 Soft
1,001 ‐ 2,000 Medium
2,001 ‐ 4,000 Stiff
4,001 ‐ 8,000 Very Stiff
8,001 ‐ 16,000 Very Hard
RELATIVE DENSITY OF COARSE‐GRAINED SOILS:
N‐Blows/ft Relative Density
0‐3 Very Loose
4‐9 Loose
10‐29 Medium Dense
30‐49 Dense
50‐80 Very Dense
80 + Extremely Dense
PHYSICAL PROPERTIES OF BEDROCK
DEGREE OF WEATHERING:
Slight Slight decomposition of parent material on
joints. May be color change.
Moderate Some decomposition and color change
throughout.
High Rock highly decomposed, may be extremely
broken.
Group
Symbol
Group Name
Cu≥4 and 1<Cc≤3
E
GW Well-graded gravel
F
Cu<4 and/or 1>Cc>3
E
GP Poorly-graded gravel
F
Fines classify as ML or MH GM Silty gravel
G,H
Fines Classify as CL or CH GC Clayey Gravel
F,G,H
Cu≥6 and 1<Cc≤3
E
SW Well-graded sand
I
Cu<6 and/or 1>Cc>3
E
SP Poorly-graded sand
I
Fines classify as ML or MH SM Silty sand
G,H,I
Fines classify as CL or CH SC Clayey sand
G,H,I
inorganic PI>7 and plots on or above "A" Line CL Lean clay
K,L,M
PI<4 or plots below "A" Line ML Silt
K,L,M
organic Liquid Limit - oven dried Organic clay
K,L,M,N
Liquid Limit - not dried Organic silt
K,L,M,O
inorganic PI plots on or above "A" Line CH Fat clay
K,L,M
PI plots below "A" Line MH Elastic Silt
K,L,M
organic Liquid Limit - oven dried Organic clay
K,L,M,P
Liquid Limit - not dried Organic silt
K,L,M,O
Highly organic soils PT Peat
(D30)2
D10 x D60
GW-GM well graded gravel with silt NPI≥4 and plots on or above "A" line.
GW-GC well-graded gravel with clay OPI≤4 or plots below "A" line.
GP-GM poorly-graded gravel with silt PPI plots on or above "A" line.
GP-GC poorly-graded gravel with clay QPI plots below "A" line.
SW-SM well-graded sand with silt
SW-SC well-graded sand with clay
SP-SM poorly graded sand with silt
SP-SC poorly graded sand with clay
Earth Engineering Consultants, LLC
IIf soil contains >15% gravel, add "with gravel" to
group name
JIf Atterberg limits plots shaded area, soil is a CL-
ML, Silty clay
Unified Soil Classification System
2 1
PZ-2
MW-1
PZ-1
PZ-5 PZ-6 MW-2
PZ-3 PZ-4
PZ-7
Figure 1: Boring Location Diagram
Schlagel Property
Fort Collins, Colorado
EEC Project #: 1172056 Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
MW-1 & MW-2:
Approximate Monitor
Well Locations
1
Legend
Site Photos
(Photos taken in approximate
location, in direction of arrow)
PZ-1 thru PZ-7:
Approximate
Piezometer Locations
PZ-2
MW-1
PZ-1
PZ-5 PZ-6 MW-2
PZ-3 PZ-4
PZ-7
(4956.1)
[4948.9]
(4957.3)
[4951.3]
(4956.1)
[4951.0]
(4953.5)
[4948.5]
(4954.2)
[4947.4]
(4951.8)
[4946.5]
(4953.2)
[4948.6]
(4954.6)
[4958.5]
(4956.5)
[4950.8]
4951
4950
4949
4948
4947
Figure 2: Groundwater Contour Map
Schlagel Property
Fort Collins, Colorado
EEC Project #: 1172056 Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
MW-1 & MW-2:
Approximate Monitor
Well Locations
Legend
PZ-1 thru PZ-7:
Approximate
Piezometer Locations
Approximate Ground
Surface Elevation
Approximate
Groundwater Elevation
(4950.8)
[4950.8]
Approximate
Groundwater Contours
Approximate
Groundwater
Directional Flow
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
EEC PROJECT NO. 1172056
JULY 2017
Earth Engineering Consultants, LLC
RIG TYPE: CME-55 WATER DEPTH
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC N/A
DNQUMCDD -200 SWELL
(feet) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
SANDY LEAN CLAY (CL) 1
brown _ _
very soft to medium stiff 2
_ _
CS 3 6 2000 21.0 106.6 33 18 65.3 <500 psf none
_ _
4
_ _
5 0 1500 17.9
_ _
6
SAND / GRAVEL (SP / GP) _ _
brown 7
very dense _ _
with cobbles 8
_ _
9
SS _ _ 50/2" -- 13.3
10
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 50/3.5" -- 21.5
_ _
16
_ _
17
_ _
18
SANDSTONE / SILTSTONE / CLAYSTONE _ _
gray 19
weathered, moderately hard to hard _ _
SS 20 50/7" 9000+ 21.7
BOTTOM OF BORING DEPTH 20' _ _
21
_ _
22
PIEZOMETER LEGEND _ _
23
2-Inch Diameter Flush Threaded- Schedule 40 PVC riser pipe _ _
Bentonite Seal 24
2-Inch Dia. Flush Threaded- Schedule 40 PVC Slotted pipe - 5' _ _
Silica Sand and/or Sand & Gravel Cave-In 25
_ _
Earth Engineering Consultants, LLC
24 HOUR 5.3'
SOIL DESCRIPTION
A-LIMITS
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
CLAYEY SAND (SC) 1
brown _ _
medium dense to dense 2
_ _
CS 3 35 -- 2.3 123.2
_ _
4
brown _ _
dense to very dense SS 550--4.8
with cobbles _ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 50/10.5" -- 7.5
_ _
11
_ _
12
_ _
13
_ _
14
_ _
15
_ _
16
_ _
17
_ _
18
SANDSTONE / SILTSTONE / CLAYSTONE _ _
brown / gray, moderately hard to hard 19 -- 1000 21.8
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SHEET 1 OF 1 WATER DEPTH
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
CLAYEY SAND (SC) _ _
brown, medium dense to dense 2
_ _
SAND / GRAVEL (SP / GP) CS 3 50/9" -- 4.5 112.1
brown _ _
dense to very dense 4
with cobbles _ _
SS 5 50/7" -- 5.0
_ _
6
_ _
7
_ _
8
_ _
9
_ _
SS 10 50/4" -- 7.6
_ _
11
_ _
12
_ _
13
_ _
14
_ _
15
_ _
16
_ _
17
_ _
18
_ _
19 -- 1000 11.8
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SCHLAGEL PROPERTY
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
CLAYEY SAND (SC) _ _
brown 2
medium dense _ _
with trace gravel and calcareous deposits CS 3 14 8000 9.2 92.6 33 18 38.8 1400 psf 0.8%
_ _
SAND / GRAVEL (SP / GP) 4
brown _ _
medium dense SS 519--4.2
with cobbles _ _
6
_ _
7
_ _
8
_ _
9 -- -- 4.9
_ _
10
_ _
11
_ _
12
_ _
13
_ _
14
BOTTOM OF BORING DEPTH 14' _ _
15
_ _
16
_ _
17
_ _
18
_ _
19
_ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SCHLAGEL PROPERTY
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
SANDY LEAN CLAY (CL) _ _
brown 2
loose _ _
with organics CS 3 7 5500 19.5 102.7 3500 psf 2.1%
_ _
4
_ _
SS 517--9.4
_ _
6
brown _ _
medium dense to dense 7
with cobbles _ _
8
_ _
9
_ _
SS 10 50 -- 14.4
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 50 1000 9.2
_ _
16
_ _
17
_ _
18
SANDSTONE / SILTSTONE / CLAYSTONE _ _
gray, moderately hard to hard 19 -- 1000 12.3
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SHEET 1 OF 1 WATER DEPTH
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
FAT CLAY with SAND (CH) _ _
brown 2
very stiff _ _
with calcareous deposits CS 3 27 9000+ 14.9 106.1 52 31 82.8 2500 psf 3.5%
with organics _ _
4
_ _
SILTY SAND (SM) SS 5 3 2000 20.2
brown _ _
very loose to medium dense 6
_ _
7
_ _
8
_ _
9
_ _
SS 10 21 -- 26.4
SAND / GRAVEL (SP / GP) _ _
brown 11
medium dense _ _
with cobbles 12
_ _
13
_ _
14
_ _
15
_ _
16
_ _
17
_ _
18
_ _
19
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SCHLAGEL PROPERTY
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
CLAYEY SAND (SC) _ _
brown 2
loose to medium dense _ _
CS 3 5 2500 20.7 101.3 <500 psf none
_ _
4
_ _
SS 5 18 -- 19.9
_ _
6
_ _
brown, medium dense to dense 7
_ _
8
_ _
9
_ _
SS 10 50/8" -- 11.1
_ _
11
_ _
12
_ _
13
_ _
14
_ _
SS 15 50/7" -- 11.9
_ _
16
_ _
17
SANDSTONE / SILTSTONE / CLAYSTONE _ _
gray 18
weathered, moderately hard to hard _ _
19 -- 1000 21.5
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SHEET 1 OF 1 WATER DEPTH
DATE:
RIG TYPE: CME55
FOREMAN: DG
AUGER TYPE: 4" CFA
SPT HAMMER: AUTOMATIC
SOIL DESCRIPTION DNQUMCDD -200
TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF
VEGETATION & TOPSOIL _ _
1
LEAN CLAY with SAND (CL) _ _
brown 2
medium stiff to stiff _ _
with organics CS 3 9 5000 20.6 104.6 42 26 75.8 1000 psf 0.3%
_ _
4
_ _
SS 5 9 7000 12.2
_ _
6
_ _
7
brown _ _
very dense 8
with cobbles _ _
9
_ _
SS 10 50/7" -- 4.9
_ _
11
_ _
12
_ _
13
_ _
14 -- -- 8.3
_ _
15
_ _
16
_ _
17
_ _
18
_ _
19
BOTTOM OF BORING DEPTH 19' _ _
20
_ _
21
_ _
22
_ _
23
_ _
24
_ _
25
_ _
Earth Engineering Consultants, LLC
SHEET 1 OF 1 WATER DEPTH
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 20.4% Dry Density: 106.7 pcf Ending Moisture: 19.4%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Monitoring Well 1, Sample 1, Depth 2'
Liquid Limit: 29 Plasticity Index: 14 % Passing #200: 48.9%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Clayey Sand (SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 21.0% Dry Density: 112.3 pcf Ending Moisture: 19.5%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Monitoring Well 2, Sample 1, Depth 2'
Liquid Limit: 33 Plasticity Index: 18 % Passing #200: 65.3%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 8.8% Dry Density: 113.8 pcf Ending Moisture: 16.8%
Swell Pressure: 1400 psf % Swell @ 500: 0.8%
Sample Location: Piezometer 3, Sample 1, Depth 2'
Liquid Limit: 33 Plasticity Index: 18 % Passing #200: 38.8%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Clayey Sand (SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 19.5% Dry Density: 99.1 pcf Ending Moisture: 21.3%
Swell Pressure: 3500 psf % Swell @ 500: 2.1%
Sample Location: Piezometer 4, Sample 1, Depth 2'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Sandy Lean Clay (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 14.9% Dry Density: 112.6 pcf Ending Moisture: 21.9%
Swell Pressure: 2500 psf % Swell @ 500: 3.5%
Sample Location: Piezometer 5, Sample 1, Depth 2'
Liquid Limit: 52 Plasticity Index: 31 % Passing #200: 82.8%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Fat Clay with Sand (CH)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 20.7% Dry Density: 106.7 pcf Ending Moisture: 20.1%
Swell Pressure: <500 psf % Swell @ 500: None
Sample Location: Piezometer 6, Sample 1, Depth 2'
Liquid Limit: - - Plasticity Index: - - % Passing #200: - -
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Clayey Sand (SC)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
Project:
Location:
Project #:
Date:
Schlagel Property
Fort Collins, Colorado
1172056
Aug-17
Beginning Moisture: 20.6% Dry Density: 110.7 pcf Ending Moisture: 19.1%
Swell Pressure: 1000 psf % Swell @ 500: 0.3%
Sample Location: Piezometer 7, Sample 1, Depth 2'
Liquid Limit: 42 Plasticity Index: 26 % Passing #200: 75.8%
SWELL / CONSOLIDATION TEST RESULTS
Material Description: Brown Lean Clay with Sand (CL)
-10.0
-8.0
-6.0
-4.0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
0.01 0.1 1 10
Percent Movement
Load (TSF)
Consolidatio Swell
Water Added
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Schlagel Properties
Location: Fort Collins, Colorado
Project No: 1172056
Sample ID: MW-1, S-2, 4'
Sample Desc.: Poorly Graded Sand with Silt and Gravel (SP - SM)
Date: August 2017
48
40
29
24
19
75
61
50
12
7.7
100
100
93
81
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
August 2017
25.00 4.51 2.34
Schlagel Properties
Fort Collins, Colorado
1172056
MW-1, S-2, 4'
Poorly Graded Sand with Silt and Gravel (SP - SM)
D100 D
60 D50
0.65 0.11
Fine
39.96 0.84
D30 D
10 Cu
CC
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Schlagel Properties
Location: Fort Collins, Colorado
Project No: 1172056
Sample ID: PZ-1, S-3, 9'
Sample Desc.: Well Graded Sand with Silt and Gravel (SW - SM)
Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
100
89
83
69
62
49
37
9
5.8
35
29
20
17
13
1.35 0.19
Fine
45.92 1.11
D30 D
10 Cu
CC
August 2017
37.50 8.64 5.11
Schlagel Properties
Fort Collins, Colorado
1172056
PZ-1, S-3, 9'
Well Graded Sand with Silt and Gravel (SW - SM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Schlagel Properties
Location: Fort Collins, Colorado
Project No: 1172056
Sample ID: PZ-4, S-4, 14'
Sample Desc.: Well Graded Sand with Silt and Gravel (SW - SM)
Date: August 2017
42
35
28
24
21
67
55
44
15
11.1
100
88
85
73
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
August 2017
37.50 6.69 3.64
Schlagel Properties
Fort Collins, Colorado
1172056
PZ-4, S-4, 14'
Well Graded Sand with Silt and Gravel (SW - SM)
D100 D
60 D50
0.78 0.08
Fine
89.15 1.22
D30 D
10 Cu
CC
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Schlagel Properties
Location: Fort Collins, Colorado
Project No: 1172056
Sample ID: PZ-6, S-3, 9'
Sample Desc.: Well Graded Sand with Silt and Gravel (SW - SM)
Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
100
100
95
85
79
70
59
14
9.0
56
46
33
27
21
0.52 0.09
Fine
29.80 1.12
D30 D
10 Cu
CC
August 2017
25.00 2.68 1.51
Schlagel Properties
Fort Collins, Colorado
1172056
PZ-6, S-3, 9'
Well Graded Sand with Silt and Gravel (SW - SM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
1 1/2" (37.5 mm)
1" (25 mm)
3/4" (19 mm)
1/2" (12.5 mm)
3/8" (9.5 mm)
No. 4 (4.75 mm)
No. 8 (2.36 mm)
No. 10 (2 mm)
No. 16 (1.18 mm)
No. 30 (0.6 mm)
No. 40 (0.425 mm)
No. 50 (0.3 mm)
No. 100 (0.15 mm)
No. 200 (0.075 mm)
Project: Schlagel Properties
Location: Fort Collins, Colorado
Project No: 1172056
Sample ID: PZ-7, S-3, 9'
Sample Desc.: Well Graded Sand with Silt and Gravel (SW - SM)
Date: August 2017
EARTH ENGINEERING CONSULTANTS, LLC
SUMMARY OF LABORATORY TEST RESULTS
Sieve Analysis (AASHTO T 11 & T 27 / ASTM C 117 & C 136)
Sieve Size Percent Passing
100
90
78
71
65
55
44
11
7.4
42
33
23
19
16
1.00 0.13
Fine
53.94 1.09
D30 D
10 Cu
CC
August 2017
37.50 7.04 3.61
Schlagel Properties
Fort Collins, Colorado
1172056
PZ-7, S-3, 9'
Well Graded Sand with Silt and Gravel (SW - SM)
D100 D
60 D50
EARTH ENGINEERING CONSULTANTS, LLC
Summary of Washed Sieve Analysis Tests (ASTM C117 & C136)
Date:
Project:
Location:
Project No:
Sample ID:
Sample Desc.:
Cobble Silt or Clay
Gravel
Coarse Fine
Sand
Coarse Medium
6"
5"
4"
3"
2.5"
2"
1.5"
1"
3/4"
1/2"
3/8"
No. 4
No. 8
No. 10
No. 16
No. 30
No. 40
No. 50
No. 100
No. 200
0
10
20
30
40
50
60
70
80
90
100
1000 100 10 1 0.1 0.01
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 3.0 4951.6 4957.6 5.0 4946.8 4952.8 5.0 4951.5 4957.5
7/27/2017 3.8 4950.8 4956.8 5.3 4946.5 4952.5 4.7 4951.8 4957.8
9/19/2017 4.0 4950.6 4956.6 5.7 4946.1 4952.1 5.2 4951.3 4957.3
10/19/2017 4.0 4950.6 4956.6 5.6 4946.2 4952.2 5.0 4951.5 4957.5
2/12/2017 5.7 4948.9 4954.9 7.0 4944.8 4950.8 6.8 4949.7 4955.7
6/7/2018 3.7 4950.9 4956.9 5.2 4946.6 4952.6 4.4 4952.1 4958.1
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 5.5 4947.7 4953.7 5.0 4951.1 4957.1 5.0 4948.5 4954.5
7/27/2017 4.6 4948.6 4954.6 5.1 4951.0 4957.0 5.0 4948.5 4954.5
9/19/2017 4.7 4948.5 4954.5 5.8 4950.3 4956.3 5.3 4948.2 4954.2
10/19/2017 4.6 4948.6 4954.6 5.9 4950.2 4956.2 5.1 4948.4 4954.4
2/12/2017 6.2 4947.0 4953.0 7.5 4948.6 4954.6 6.5 4947.0 4953.0
6/7/2018 4.6 4948.6 4954.6 4.4 4951.7 4957.7 5.3 4948.2 4954.2
Boring/Piezometer No. (PZ)
Approx Surface Elev (ft)
Date Measured
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
Approx Depth
to GW
Approx
GW Elev
Min Bldg FG
7/26/2017 5.0 4952.3 4958.3 6.5 4947.7 4953.7 7.0 4949.1 4955.1
7/27/2017 6.0 4951.3 4957.3 6.8 4947.4 4953.4 7.2 4948.9 4954.9
9/19/2017 7.0 4950.3 4956.3 6.7 4947.5 4953.5 7.3 4948.8 4954.8
10/19/2017 7.1 4950.2 4956.2 6.6 4947.6 4953.6 7.3 4948.8 4954.8
2/12/2017 8.8 4948.5 4954.5 8.0 4946.2 4952.2 8.9 4947.2 4953.2
6/7/2018 5.1 4952.2 4958.2 7.2 4947.0 4953.0 7.0 4949.1 4955.1
4957.3 4954.2 4956.1
4953.5
PZ-7
PZ-4
4953.2
4954.6 4951.8 4956.5
4956.1
MW-1 MW-2 PZ-1
PZ-2 PZ-3
PZ-5 PZ-6
Northfield - (AKA Schalagel Property)
Earth Engineering Consultants, LLC (EEC) - Project No. 1172056
Groundwater Monitoring - Summary Table
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
Finer by Weight (%)
Grain Size (mm)
Standard Sieve Size
START DATE
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-7 AUGUST 2017
7/26/2017 WHILE DRILLING 7.0'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
SURFACE ELEV N/A 24 HOUR 7.2'
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
WELL GRADED SAND with SILT and GRAVEL
(SW / SM)
START DATE
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-6 AUGUST 2017
7/26/2017 WHILE DRILLING 6.5'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
SURFACE ELEV N/A 24 HOUR 6.8'
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
WELL GRADED SAND with SILT and GRAVEL
(SW / SM)
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-5 AUGUST 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 7/26/2017 WHILE DRILLING 5.0'
SURFACE ELEV N/A 24 HOUR 6.0'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
START DATE
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-4 AUGUST 2017
7/26/2017 WHILE DRILLING 5.0'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
SURFACE ELEV N/A 24 HOUR 5.0'
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
WELL GRADED SAND with SILT and GRAVEL
(SW / SM)
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-3 AUGUST 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 7/26/2017 WHILE DRILLING 5.0'
SURFACE ELEV N/A 24 HOUR 5.1'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-2 AUGUST 2017
SHEET 1 OF 1 WATER DEPTH
START DATE 7/26/2017 WHILE DRILLING 5.5'
SURFACE ELEV N/A 24 HOUR 4.6'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
START DATE
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
PROJECT NO: 1172056 LOG OF PIEZOMETER PZ-1 AUGUST 2017
7/26/2017 WHILE DRILLING 5.0'
FINISH DATE 7/26/2017 AFTER DRILLING N/A
SURFACE ELEV N/A 24 HOUR 4.7'
*Note: Hand/field slotted 1-1/2-inch diameter PVC
casing was installed after completion of drilling
operations.
A-LIMITS SWELL
WELL GRADED SAND with SILT and GRAVEL
(SW / SM)
SS
WHILE DRILLING 5.0'
GROUND SURFACE ELEV N/A AFTER DRILLING N/A
PZ DETAILS START DATE 7/26/2017
FOREMAN: DG FINISH DATE 7/26/2017
TOP OF CASING ELEV.
SCHLAGEL PROPERTY
FORT COLLINS, COLORADO
PROJECT NO: 1172056
LOG OF GROUND MONITORING WELL MW-2
DATE: AUGUST 2017
SHEET 1 OF 1
Soil Classification
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests
Sands 50% or more
coarse fraction
passes No. 4 sieve
Fine-Grained Soils
50% or more passes
the No. 200 sieve
<0.75 OL
Gravels with Fines
more than 12%
fines
Clean Sands Less
than 5% fines
Sands with Fines
more than 12%
fines
Clean Gravels Less
than 5% fines
Gravels more than
50% of coarse
fraction retained on
No. 4 sieve
Coarse - Grained Soils
more than 50%
retained on No. 200
sieve
CGravels with 5 to 12% fines required dual symbols:
Kif soil contains 15 to 29% plus No. 200, add "with sand"
or "with gravel", whichever is predominant.
<0.75 OH
Primarily organic matter, dark in color, and organic odor
ABased on the material passing the 3-in. (75-mm)
sieve
ECu=D60/D10 Cc=
HIf fines are organic, add "with organic fines" to
group name
LIf soil contains ≥ 30% plus No. 200 predominantly sand,
add "sandy" to group name.
MIf soil contains ≥30% plus No. 200 predominantly gravel,
add "gravelly" to group name.
DSands with 5 to 12% fines require dual symbols:
BIf field sample contained cobbles or boulders, or
both, add "with cobbles or boulders, or both" to
group name. FIf soil contains ≥15% sand, add "with sand" to
GIf fines classify as CL-ML, use dual symbol GC-
CM, or SC-SM.
Silts and Clays
Liquid Limit less
than 50
Silts and Clays
Liquid Limit 50 or
more
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100 110
PLASTICITY INDEX (PI)
LIQUID LIMIT (LL)
ML OR OL
MH OR OH
For Classification of fine-grained soils and
fine-grained fraction of coarse-grained
soils.
Equation of "A"-line
Horizontal at PI=4 to LL=25.5
then PI-0.73 (LL-20)
Equation of "U"-line
Vertical at LL=16 to PI-7,
then PI=0.9 (LL-8)
CL-ML
HARDNESS AND DEGREE OF CEMENTATION:
Limestone and Dolomite:
Hard Difficult to scratch with knife.
Moderately Can be scratched easily with knife.
Hard Cannot be scratched with fingernail.
Soft Can be scratched with fingernail.
Shale, Siltstone and Claystone:
Hard Can be scratched easily with knife, cannot be
scratched with fingernail.
Moderately Can be scratched with fingernail.
Hard
Soft Can be easily dented but not molded with
fingers.
Sandstone and Conglomerate:
Well Capable of scratching a knife blade.
Cemented
Cemented Can be scratched with knife.
Poorly Can be broken apart easily with fingers.
Cemented
As previously mentioned a final subgrade investigation and pavement design should be performed
in general accordance with LCUASS prior to placement of any pavement sections, to determine the
required pavement section after design configurations, roadway utilities have been installed and
roadways have been prepared to “rough” subgrade elevations.