Loading...
HomeMy WebLinkAboutReports - Soils - 05/19/2025 4396 GREENFIELD DRIVE WINDSOR, COLORADO 80550 (970) 545-3908 FAX (970) 663-0282 May 19, 2025 Realty Capital Residential 909 Lake Carolyn Parkway, Suite 150 Irving, Texas 75039 Attn: Mr. Spencer Long (Spencer@realtycapital.com) Re: Supplemental Subsurface Exploration Report - Executive Summary Letter Proposed Development of Property Located at 360 Linden Street Southwest Corner of Linden Street and Willow Street – Multi-Family Development Fort Collins, Colorado EEC Project No. 1252035 Mr. Long: Enclosed, herewith, are the results of the supplemental geotechnical engineering subsurface exploration services completed by Earth Engineering Consultants, LLC (EEC) personnel for the proposed multi-family/mixed use development project planned for design and construction at 360 Linden Street in Fort Collins, Colorado. It should be noted that in 2014, EEC completed a subsurface exploration on this property for, at that time, the proposed “Old Elk Distillery.” For further information and findings thereof, please refer to our “Subsurface Exploration Report” with a revised date of May 10, 2016, EEC Project No. 1142032. During our 2014 subsurface exploration, five (5) borings were completed at select locations across the site. We have reviewed these borings, and we have relied upon the data for the currently proposed development concept. Based on the most recently updated plan concept proposed the site, we now understand the development will consist of two (2) 5-story wood-framed multi-family buildings having at grade parking along with store front retail, and lobby/amenity space, then 4 levels above for multi- family apartments with a total of 160 units, along with on-site pavement improvements as indicated on the enclosed site diagram. Based on the new development plan concept, the design team and the developer determined that a supplemental subsurface exploration should be performed to provide comprehensive subsurface condition coverage across the entire development plan concept, as well as to update the geotechnical recommendations for the new plan concept. The updated detailed site plan/schematic included herein also illustrates our proposed test boring locations in comparison to those previously completed. This supplemental Earth Engineering Consultants, LLC EEC Project No. 1252035 May 19, 2025 Page 2 subsurface exploration was completed in general accordance with our proposal dated April 10, 2025. The site was occupied in 2014 and based on the current Google Earth Imagery; the southern portion of the site is still occupied with existing buildings. EEC borings in 2014 were mainly within the northern portion of the site as depicted in blue font on the enclosed site plan/test boring location diagram. Due to the increase in size and complexity of the proposed building footprints also exhibiting greater anticipated wall and column loads, three (3) supplemental borings were completed within the building footprints in areas accessible to our drilling equipment. A 4th boring was also completed within the proposed pavement improvement area. We anticipate maximum foundations loads will be relatively low to moderate with maximum wall and column loads less than 4 klf and 150 kips, respectively. If the actual loads vary significantly from the assumed loads, we should be consulted to verify our recommendations are consistent for the actual loads. Floor loads are expected to be light to moderate. Pavement areas are expected to accommodate large volumes of light vehicles and smaller volumes of heavy-duty traffic. Small grade changes are expected to develop site grades for the proposed improvements. Overall, cuts and fills are anticipated to be less than 5 feet to develop finish site grades. Based on the previously completed borings as well as the recently completed supplemental borings on May 16, 2025, we anticipate providing a potential spread footing foundation system for supporting the proposed building(s), either on new fill material which extends to the native coarse granular strata, on the granular strata, or extended to the underlying bedrock formation. Depending upon the actual maximum wall and column loads, consideration could also be given to supporting the mixed-use development building(s) on a drilled pier/deep foundation system and/or rammed aggregate piers. In summary, the subsurface materials encountered in the four (4) supplemental exploration borings completed on the site on May 16, 2025, generally consisted of approximately 2 to 4½ feet of existing fill overlying native sand and gravel with intermittent apparent cobbles. The native sand and gravel with intermittent cobbles extended to sandstone bedrock at approximate depths of 10 feet below existing site grades. The bedrock extended to the depths explored, approximately 10 to 25 feet below existing site grades. As noted on the enclosed boring logs, interbedded well cemented sandstone lenses were encountered with increased depth within the Earth Engineering Consultants, LLC EEC Project No. 1252035 May 19, 2025 Page 3 sandstone bedrock formation, (i.e., SPT results of less than 50 blows per 1” of penetration). Excavation penetrating the bedrock or cemented soils may require the use of specialized heavy- duty equipment, together with drilling and/or controlled blasting to facilitate rock break-up and removal. Consideration should be given to obtaining a unit price for difficult excavation in the contract documents for the project. Groundwater was not encountered in the May 16, 2025, supplemental borings; however, in 2016, EEC also installed groundwater piezometers and groundwater measured during that time period was encountered at depths of approximately 11 to 13 feet below current ground surface. Based on results of the previously completed and most recently completed field borings and laboratory testing, it is our opinion the proposed buildings could be supported on a conventional spread footing foundation system bearing on suitable strength native granular subsoils or on approved engineered fill material which extends to the native granular subsoils and/or to the underlying sandstone bedrock. No foundation should be founded within existing fill materials or on loose in-place natural soils. Alternative foundation systems could be considered such as drilled piers and/or rammed aggregate piers extending to and/or into the underlying sandstone bedrock formation. Footing bearing on the native undisturbed granular subsoils and/or on approved imported structural fill material extending to the native granular subsoils could be designed using a maximum net allowable bearing pressure of 3,000 psf. If a rammed aggregate pier (RAP) concept is implemented to enhance the structural integrity of bearing subsoils, typically the bearing capacity could be increased on the range of 5,000 to 8,000 psf. Rammed aggregate piers (RAP) consist of driving/placing aggregate into the supporting subgrades to develop aggregate piers or columns. The rammed aggregate piers would provide support for the overlying foundations while also improving the stiffness of the adjacent subgrades. Allowable bearing pressures of 5,000 pounds per square foot or higher can be developed with this system. Typically, the system installer provides a rammed aggregate pier design which provides design bearing pressures and post-construction settlement limits. We recommend pile load tests be carried out to verify actual pile load capacity and displacement characteristics. Rammed aggregate piers would likely be installed after removal of existing material and after completion of any new fill material. A qualified and reputable rammed aggregate pier installer should provide the necessary design recommendations for the piers. B-5 B-1B-4 B-3 B-2 B-1 B-2 B-3 B-4 12 EARTH ENGINEERING CONSULTANTS, LLC Legend Boring Location Diagram 360 Linden Street Fort Collins, Colorado EEC Project #: 1252035 Date: May 2025 Aroimate Boring Locations 1 Site Potos Potos taen in aroimate location, in direction o arro B1 Trog B5 Aro Locations o Preios Borings, 201 360 Linden Street Fort Collins, Colorado Log of Soil Boring B-1 Page 1 of 1 Project Number:1252035 Drilling Firm:Quality Rig Type:CME-55 Drilling Method:Auger Logged By:DG Date Drilled:05/16/2025 Boring Elevation:N/A Boring Depth:25.5' Lat / long: -, - At time of drilling:None After Drilling:N/A De p t h ( f t ) 5 10 15 20 25 30 35 Gr a p h i c L o g Visual Classification and Remarks 0.3 4.0 12.0 25.5 GRAVEL LOT SANDY LEAN CLAY - FILL (CL) brown SAND WITH GRAVEL (SP-GP) dense SANDSTONE brown, olive, gray well cemented, hard Interbedded cemented lenses with depth Samples Sa m p l e T y p e Modified CA SS Modified CA SS SS Sa m p l e G r a p h i c De p t h o f S a m p l e ( ft ) 14 ft 19 ft 4 ft 24 ft 9 ft N- V a l u e 43 50 50/1" 50/0.75" 50/3" Lab Un c o n f i n e d S t r e n g t h (P S F ) Mo i s t u r e C o n t e n t ( % ) 4.3 2.4 11.2 8.2 15.7 Dr y D e n s i t y ( P C F ) Li q u i d L i m i t Pl a s t i c i t y I n d e x % Fi n e s Lo a d i n g S t r e s s ( P S F ) % Sw e l l Sw e l l P r e s s u r e ( P S F ) Su l f a t e ( % ) RE M A R K S 1. Unconfined strength was estimated using a calibrated hand penetrometer. 2. Latitude, longitude, and elevation were taken from Google Earth and should be considered approximate. Graphics Legend Gravel Lot CL Sandstone SP-GP Modified CA - Modified California Sampler SS - Small Split Spoon DRAFT Earth Engineering Consultants, LLC | 4396 Greenfield Drive | Windsor, Colorado | 970-545-3908 | www.earth-engineering.com 360 Linden Street Fort Collins, Colorado Log of Soil Boring B-2 Page 1 of 1 Project Number:1252035 Drilling Firm:Quality Rig Type:CME-55 Drilling Method:Auger Logged By:DG Date Drilled:05/16/2025 Boring Elevation:N/A Boring Depth:30.5' Lat / long: -, - At time of drilling:17'After Drilling:N/A De p t h ( f t ) 5 10 15 20 25 30 35 Gr a p h i c L o g Visual Classification and Remarks 7.0 10.5 30.5 SILTY, SANDY LEAN CLAY - FILL (CL) brown very stiff to medium stiff SAND WITH GRAVEL (SP-GP) brown dense SANDSTONE brown, gray, rust well cemented, hard Interbedded cemented lenses with depth Samples Sa m p l e T y p e SS Modified CA SS Modified CA SS Modified CA SS Sa m p l e G r a p h i c De p t h o f S a m p l e ( ft ) 24 ft 29 ft 14 ft 4 ft 19 ft 2 ft 9 ft N- V a l u e 16 7 40 50/7" 50/4" 50/1.25" 50/0.5" Lab Un c o n f i n e d S t r e n g t h (P S F ) Mo i s t u r e C o n t e n t ( % ) 8.5 7.2 1.9 15.3 18.0 8.7 20.9 Dr y D e n s i t y ( P C F ) Li q u i d L i m i t Pl a s t i c i t y I n d e x % Fi n e s Lo a d i n g S t r e s s ( P S F ) % Sw e l l Sw e l l P r e s s u r e ( P S F ) Su l f a t e ( % ) RE M A R K S 1. Unconfined strength was estimated using a calibrated hand penetrometer. 2. Latitude, longitude, and elevation were taken from Google Earth and should be considered approximate. Graphics Legend Water at Time of Drilling (ATD) Sandstone SP-GP CL Modified CA - Modified California Sampler SS - Small Split Spoon DRAFT Earth Engineering Consultants, LLC | 4396 Greenfield Drive | Windsor, Colorado | 970-545-3908 | www.earth-engineering.com 360 Linden Street Fort Collins, Colorado Log of Soil Boring B-3 Page 1 of 1 Project Number:1252035 Drilling Firm:Quality Rig Type:CME-55 Drilling Method:Auger Logged By:DG Date Drilled:05/16/2025 Boring Elevation:N/A Boring Depth:25.0' Lat / long: -, - At time of drilling:20'After Drilling:N/A De p t h ( f t ) 5 10 15 20 25 30 35 Gr a p h i c L o g Visual Classification and Remarks 0.6 6.0 12.0 25.0 GRAVEL LOT SILTY, SANDY LEAN CLAY (CL) brown stiff SAND WITH GRAVEL (SP-GP) brown very dense SANDSTONE brown, gray, rust well cemented, hard Interbedded cemented lenses with depth Samples Sa m p l e T y p e Modified CA SS Modified CA SS Modified CA Sa m p l e G r a p h i c De p t h o f S a m p l e ( ft ) 9 ft 19 ft 4 ft 14 ft 24 ft N- V a l u e 9 50/6.5" 50/7" 50/10" 50/3" Lab Un c o n f i n e d S t r e n g t h (P S F ) Mo i s t u r e C o n t e n t ( % ) 9.9 2.5 11.7 14.3 12.6 Dr y D e n s i t y ( P C F ) Li q u i d L i m i t Pl a s t i c i t y I n d e x % Fi n e s Lo a d i n g S t r e s s ( P S F ) % Sw e l l Sw e l l P r e s s u r e ( P S F ) Su l f a t e ( % ) RE M A R K S 1. Unconfined strength was estimated using a calibrated hand penetrometer. 2. Latitude, longitude, and elevation were taken from Google Earth and should be considered approximate. Graphics Legend Water at Time of Drilling (ATD) SP-GP CL Gravel Lot Sandstone SS - Small Split Spoon Modified CA - Modified California Sampler DRAFT Earth Engineering Consultants, LLC | 4396 Greenfield Drive | Windsor, Colorado | 970-545-3908 | www.earth-engineering.com 360 Linden Street Fort Collins, Colorado Log of Soil Boring B-4 Page 1 of 1 Project Number:1252035 Drilling Firm:Quality Rig Type:CME-55 Drilling Method:Auger Logged By:DG Date Drilled:05/16/2025 Boring Elevation:N/A Boring Depth:10.5' Lat / long: -, - At time of drilling:None After Drilling:N/A De p t h ( f t ) 5 10 15 20 25 30 35 Gr a p h i c L o g Visual Classification and Remarks 6.0 10.0 10.5 SANDY LEAN CLAY - FILL (CL) brown medium stiff SAND WITH GRAVEL (SP-GP) brown loose to medium dense SANDSTONE brown, rust Samples Sa m p l e T y p e Modified CA SS SS Sa m p l e G r a p h i c De p t h o f S a m p l e ( ft ) 9 ft 2 ft 4 ft N- V a l u e 8 4 28 Lab Un c o n f i n e d S t r e n g t h (P S F ) Mo i s t u r e C o n t e n t ( % ) 3.6 7.3 9.3 Dr y D e n s i t y ( P C F ) Li q u i d L i m i t Pl a s t i c i t y I n d e x % Fi n e s Lo a d i n g S t r e s s ( P S F ) % Sw e l l Sw e l l P r e s s u r e ( P S F ) Su l f a t e ( % ) RE M A R K S 1. Unconfined strength was estimated using a calibrated hand penetrometer. 2. Latitude, longitude, and elevation were taken from Google Earth and should be considered approximate. Graphics Legend SP-GP Sandstone CL SS - Small Split Spoon Modified CA - Modified California Sampler DRAFT Earth Engineering Consultants, LLC | 4396 Greenfield Drive | Windsor, Colorado | 970-545-3908 | www.earth-engineering.com DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF GRAVEL - 4" _ _ 1 FILL: Miscellaneous Soil with Cinders & Apparent Coal Ash _ _ black / brown 2 with coal chunks _ _ 3 _ _ 4 _ _ CS 5 9 4000 8.9 115.9 CLAYEY SAND (SC) _ _ brown, medium dense to loose 6 _ _ 7 SAND & GRAVEL (SP/GP) _ _ brown 8 medium dense _ _ 9 _ _ SS 10 50/10" -- 1.8 _ _ SANDSTONE / SILTSTONE 11 brown / rust _ _ poorly cemented to cemented 12 with intermittent well cemented lenses _ _ 13 _ _ 14 _ _ CS 15 50/1" -- 10.4 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ grey SS 20 50/0.5" 9000+ 14.3 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ CS 25 50/0.5" 9000+ 11.8 BOTTOM OF BORING DEPTH 25.0' _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 4/16/2014 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 4/16/2014 WHILE DRILLING None 360 LINDEN STREET FORT COLLINS, COLORADO LOG OF BORING B-1PROJECT NO: 1142032 APRIL 2014 DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF GRAVEL - 4" _ _ 1 FILL: Miscellaneous Soil with Cinders & Apparent Coal Ash _ _ brown / black 2 _ _ 3 _ _ 4 _ _ CLAYEY SAND (SC) CS 5 9 8500 10.9 121.2 <500 psf None brown _ _ medium dense to loose 6 _ _ 7 _ _ 8 1' gravel seam _ _ 9 _ _ SS 10 50/7" -- 10.3 SANDSTONE _ _ brown / rust 11 poorly cemented to cemented _ _ with intermittent well cemented zones 12 _ _ 13 _ _ 14 grey _ _ CS 15 50/1" 9000+ 12.3 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ SS 20 50/2" 9000+ 14.9 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ CS 25 50/0.5" 9000+ 9.4 BOTTOM OF BORING DEPTH 25.0' _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL SURFACE ELEV N/A 24 HOUR 14.0' FINISH DATE 4/16/2014 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 4/16/2014 WHILE DRILLING 19.0' 360 LINDEN STREET FORT COLLINS, COLORADO PROJECT NO: 1142032 LOG OF BORING B-2 APRIL 2014 DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF GRAVEL - 4" _ _ 1 FILL - Miscellaneous Soil with Cinders & Apparent Coal As _ _ brown / black 2 _ _ CLAYEY SAND (SC) CS 3 7 3500 7.5 116.0 brown _ _ medium dense to loose 4 _ _ SS 5 4 6000 8.9 _ _ 6 _ _ SAND & GRAVEL (SP/GP) 7 brown _ _ medium dense 8 _ _ 9 _ _ CS 10 50/5" -- 3.8 _ _ SANDSTONE/SILTSTONE 11 brown / rust _ _ poorly cemented to cemented 12 _ _ 13 _ _ 14 BOTTOM OF BORING DEPTH 14.0' _ _ Auger Refusal on Apparent Well Cemented SS 15 Bounce 9000+ 12.4 Sandstone _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 4/16/2014 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 4/16/2014 WHILE DRILLING None 360 LINDEN STREET FORT COLLINS, COLORADO PROJECT NO: 1142032 LOG OF BORING B-3 APRIL 2014 DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF GRAVEL - 4" _ _ 1 FILL - Miscellaneous Soil with Cinders & Apparent Coal As _ _ brown / black 2 _ _ 3 _ _ 4 _ _ CLAYEY SAND (SC) CS 5 10 7500 11.8 120.0 brown, medium dense _ _ 6 SAND & GRAVEL (SP/GP) _ _ brown 7 medium dense _ _ 8 _ _ 9 _ _ SS 10 50 -- 1.9 _ _ 11 SANDSTONE/SILTSTONE _ _ brown / rust 12 poorly cemented to cemented _ _ 13 _ _ 14 _ _ with intermittent well cemented lenses CS 15 -- _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ grey SS 20 50/0.5" 9000+ 13.8 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ CS 25 50/0.5" BOTTOM OF BORING DEPTH 25.0' _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 4/16/2014 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 4/16/2014 WHILE DRILLING None 360 LINDEN STREET FORT COLLINS, COLORADO PROJECT NO: 1142032 LOG OF BORING B-4 APRIL 2014 DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ FILL: LEAN CLAY (CL) with Apparent Cinders & Coal Ash 1 brown / black _ _ 2 _ _ CS 3 10 9000+ 11.7 113.8 _ _ 4 _ _ CLAYEY GRAVEL, brown, medium dense SS 5 34 6000 14.3 _ _ SAND & GRAVEL (SP/GP) 6 brown _ _ medium dense 7 _ _ 8 _ _ 9 _ _ CS 10 50/8" -- 1.1 132.4 _ _ SANDSTONE 11 grey / olive _ _ poorly cemented to cemented 12 with intermittent well cemented zones _ _ 13 _ _ 14 _ _ SS 15 50/3" 9000+ 14.0 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ CS 20 50/1.5" 9000+ 13.7 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ SS 25 50/1.5" 9000+ 13.7 BOTTOM OF BORING DEPTH 25.5' _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 4/16/2014 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 4/16/2014 WHILE DRILLING None 360 LINDEN STREET FORT COLLINS, COLORADO PROJECT NO: 1142032 LOG OF BORING B-5 APRIL 2014