3-River Well House 1 Condition Assessment Tech Memo - September 2023.pdf

541-385-4772 ■ 963 SW Simpson Avenue, Suite 200 ■ Bend, Oregon 97702 ■ www.dowl.com

TECHNICAL MEMORANDUM

BACKGROUND

The City of Bend (City) contracted DOWL to perform a condition assessment of the existing River Well #1 building and provide recommended repair and replacement cost estimates. The building is located at 341 SW Shevlin Hixon Drive in Bend, Oregon. The original date of construction is unknown. The building is exhibiting signs of geotechnical and structural distress.

This memorandum summarizes the findings from a condition assessment site visit and geotechnical investigation, and it presents recommended repair and replacement alternatives.

An opinion of construction costs for each alternative is included.

Figure 1: Location map

TO: Nick McAteer, Assistant City Engineer - Utilities, City of Bend

David Buchanan, Project Manager, City of Bend

FROM: Jim Albin, Project Manager, DOWL Kenton Alldritt, Project Engineer, DOWL

DATE: 9/12/2023

PROJECT: City of Bend River Well #1 Condition Assessment Project Number: 2190.14934.01

EXPIRES:

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Figure 2: General site photo looking south

CONDITION ASSESSMENT

Scope of Assessment

The assessment of the River Well #1 building was performed on May 9th, 2023. Kenton Alldritt from DOWL performed the structural assessment. Lisa Splitter from Wallace Group was also on site. The assessment included examination and recording of the following:

� Signs of concrete cracking

� Signs of leakage or soil infiltration

� Deterioration of concrete, including delamination and spalling

� Exposed rebar, including corrosion and section loss

� Connections between the roof and the walls, and the walls and the floor

� Condition of the walls and floor slab

� General condition of visible building appurtenances, such as piping and vents

� Condition of any previous repairs

� General measurements of the existing structure

The scope of the assessment was limited to visual observation of general structural condition.

Inspection of mechanical and electrical equipment was not within the scope of the assessment.

Mechanical and electrical equipment inside the building were not moved to observe structural components hidden by the equipment. Additionally, the roof of the building was not accessed, and the ceiling was not removed to inspect the attic or underside of roof. The building assessment was performed by walking the perimeter and interior of the building and noting abnormalities or signs of distress. Removal of soil to inspect the building foundation was not performed.

Structural Condition Assessment

The condition assessment results are referenced from the wall orientation detailed in Figure 3.

Figure 3: Wall orientation map

Exterior Assessment Results

The east wall had a horizontal crack approximately mid-height of the wall stretching from the center pilaster to the southeast pilaster, which is shown in Figures 4 and 5.

Figure 4: Horizontal crack in east wall (overview)

Figure 5: Horizontal crack in east wall

Each wall had a concrete pilaster at each corner and in the middle of the wall. Nearly all pilasters had vertical cracks along the full height of the pilaster. Examples of these cracks are shown in Figures 6 and 7.

Figure 6: Vertical crack in north wall

Figure 7: Vertical crack in south wall

The south wall is leaning to the north and was measured to be out of plumb by 2.5 inches in the southeast corner. Figure 8 shows the southeast wall corner next to the electrical cabinet, which was measured to be plumb for reference. The north wall also appeared to be out of plumb but not to the severity of the south wall. The east and west walls appeared to be plumb.

Figure 8: Southeast wall corner

Interior Assessment Results

Two wall cracks were found inside the building. One wall crack was found running vertical in the center of the east wall. The other crack was found stemming from the wall vent in the east wall.

Figure 9 shows a vertical wall crack found in the east interior wall.

Figure 9: Vertical crack in wall

The floor slab exhibited significant cracking. The floor slab cracks were stemming from the pipe penetrations. The floor slab outside of the pipe penetrations appeared lower than the slab adjacent to the pipes. Some of the cracks connected to previous construction joints, and some of the cracks stretched to the walls-to-slab joints. No visible cracks appeared to travel from the slab up into the walls. The floor slab had a coating that was also cracked like the substrate concrete. The floor slab appeared to slope from the southeast to the northwest. Evidence of ponding water was found in the northwest corner; however, there was no sump or drainage line in the northwest corner. Figures 10 through 19 show example photos of the floor slab cracking.

Figure 20 shows the debris build-up in the northwest corner, which could be a result of the sloped floor.

Figure 10: Crack in floor slab (south slab section)

Figure 11: Crack in floor slab (south slab section)

Figure 12: Crack in floor slab (north slab section)

Figure 13: Crack in floor slab near construction joint

Figure 14: Crack in floor slab (north slab section)

Figure 15: Crack in floor slab (north slab section at construction joint)

Figure 16: Crack in floor slab (north slab section at construction joint)

Figure 17: Crack in floor slab (north slab section at construction joint, close up)

Figure 18: Crack in floor slab at north drain hole

Figure 19: Crack in floor slab at south drain hole

Figure 20: Evidence of water gathering in northwest corner

Geotechnical Investigation

Wallace Group developed a Geotechnical Exploration Summary, which is attached to this memorandum. Two geotechnical borings were taken near the building on April 24th and 25th, 2023, with one boring near the northwest building corner and one near the southeast corner.

The Geotechnical Exploration Summary states the subsurface consists of the following soil layers:

� Landscaping and undocumented fill – organic soils and undocumented fill materials composed of organic material, wood chips, and metal debris contained within silt and sand soil

� Alluvial sand, gravel, and silt – generally medium to very dense stratum consisting of layers of gravel, sand and silt

� Decomposed tuff – saturated decomposed tuff, which was completely weathered and exhibited low strength based on the Standard Penetration Tests

� Alluvial gravel – very dense alluvial gravel, cobble, and sands that were wet, subangular to rounded, and fine to coarse grained

The Geotechnical Exploration Summary states that the soils supporting the building are consolidating. Consolidation is occurring from organic material decay and consolidating decomposed tuff. Laboratory consolidation tests were conducted, and Wallace Group estimates the settlement ranges between 14 to 25 inches, where at least 3.5 inches of differential settlement has already occurred.

The Geotechnical Exploration Summary also states that the settlement of the soil around the well casing may cause downdrag forces on the well casing. Preliminary downdrag forces were provided in the Geotechnical Exploration Summary.

REPAIR RECOMMENDATIONS

The building is experiencing differential settlement caused by multiple layers of consolidating soil supporting the building. Continued settlement of the supporting soil is expected. Mitigation of the settlement is achieved by installing deep foundation elements, such as helical piers. The deep foundation elements must be installed deeper than the consolidating soil layers. The following repair measures are available for the building:

� Deep foundation retrofit with floor slab replacement – Install helical piers or micropiles around the building. Install a connection between the existing footing and the retrofit deep foundation element. Replace the floor slab inside the building with a cast-in-place concrete slab that is free to float from the wall foundation and well casing. Figure 21 shows a detail of the foundation retrofit alternative. The repair most likely will need to be constructed during a shut down of the well operations.

� Building replacement – Demolish the existing building and construct a new building using deep foundation elements. The well operations need to be shut down during building replacement.

Figure 21: Foundation retrofit detail (not-to-scale)

Due to the high cost of installing deep foundation elements on the existing building, the extensive floor slab cracking, and the remaining useable life of the building, DOWL recommends the building be replaced. The cost of building replacement has a similar magnitude as installing a deep foundation retrofit and floor slab replacement for the existing structure.

For the interim before building replacement, DOWL recommends the following measures:

� Patching the cracks in the floor slab with concrete crack repair materials.

� Removing a modest amount of concrete around of the base of the pump support to allow differential movement between the pump support and floor slab.

� Regular structural and mechanical inspections of the building to monitor structural deficiencies and mechanical systems subject to settlement deformations. DOWL recommends inspecting the building every 2 years.

� Regular survey measurements of the building including 3D scanning to precisely monitor the settlement of the building.

The City requested recommendations for slowing the settlement rate to extend the life span of the building. One method to address the settlement is to preform injection grouting or compaction grouting under the building to densify the consolidating soil layers. An illustration of injection grouting is shown in Figure 22. Injection grouting a portion of the consolidating layers to slow the settlement is not recommended due to the high cost of mobilizing the injection grouting operation and the thick layer of consolidating soil on the site. If injection grouting is performed, DOWL recommends completing the repair by injecting the entire consolidating layers.

Figure 21: Injection grouting (diagram courtesy of UC Davis)

The Geotechnical Exploration Summary stated that the soil settlement around the well casing may be causing downdrag forces on the well casing and that a structural analysis of the casing should be completed. DOWL did not perform a structural analysis of the well casing as part of the condition assessment and development of this memorandum. DOWL recommends a structural analysis of the well casing be performed to investigate the effects of settlement downdrag on the well casing.

PRELIMINARY COST ESTIMATE

An engineer’s opinion of probable construction cost is shown in Table 1. The cost table includes the deep foundation repair measures and the cost to replace the building.

The cost estimates include an accuracy range of -15% to +50%. This accuracy range is based on the preliminary nature of the recommended repairs and replacement design effort completed at the time of this memorandum. All estimate data includes contractor mobilization, engineering design, and construction engineering support. Unit prices used in this opinion of probable cost represent DOWL’s opinion of today's costs. The prices of construction materials and labor are currently in a state of high volatility. The unit costs listed in the cost estimates attempt to account for this volatility. However, prices may need to be adjusted for future escalation or market changes.

The replacement cost estimate does not include the cost of site and pipe improvements, which is outside the scope of this memorandum. The City should be aware that these costs can be significant, and the total project cost are likely larger than the cost shown herein. Preliminary analysis and appropriate due diligence should be completed before selecting this alternative. In addition, the cost estimate assumes the existing material is free of hazardous materials. The existing material should be tested for hazardous material prior to commencing work so any additional costs can be accounted for.

Two cost estimates are listed in Table 1. A short description of each alternative follows:

� Repair and Retrofit Alternative: Includes replacing the existing floor slab and installing new deep foundation elements to extend the remaining life of the structure. Includes a 10% mobilization cost, 30% design engineering cost, and 30% construction engineering cost.

� Replacement Alternative: An estimate for the removal of the existing building and replacement with a new building. The preliminary cost estimate is based on average unit costs for building construction materials. The cost includes percentages estimates for building mechanical, electrical and finish work. The costs do not include civil site work, piping mechanical and electrical, auxiliary buildings, vaults, upgrades and permitting efforts.

Existing piping mechanical, electrical and controls may be able to be salvaged and reused in the new building pending confirmation from a mechanical and electrical design effort.

Includes a 10% mobilization cost, 30% design engineering cost, and 30% construction engineering cost.

Table 1: Engineer's Opinion of Probable Cost Summary

Alternatives Probable Cost

Total Cost Low Range

@ -15% Cost High Range

@ 50%

Repair and Retrofit* $722,000 $614,000 $1,083,000

Replacement* $1,256,000 $1,068,000 $1,884,000

*Note: cost does not include civil site work, piping mechanical and electrical, auxiliary buildings, vaults and modifications to existing vaults, upgrades and permitting efforts.

CONCLUSION

The City River Well #1 building is showing signs of geotechnical and structural distress. DOWL assessed the building and presented recommended repair and replacement options with associated preliminary costs. Due to the high cost of the repair and the age of the structure, DOWL recommends the City make plans to replace the structure. DOWL recommends that floor slab cracks be patched, and regular inspections be performed to monitor the continued settlement of the building. DOWL recommends a structural analysis of the well casing be completed to evaluate the risk of downdrag forces on the well casing.

ATTACHMENTS

Attachment A: Engineer’s Opinion of Probable Costs

Attachment B: Geotechnical Exploration Summary

ATTACHMENT A:

ENGINEER’S OPINION OF

PROBABLE COSTS

Spec.

Sec. No. Item Unit Quantity Unit Price Total Price

BUILDING ACCESS

10 Mobilization (@ 10% subtotal of items) LS 1 45,100.00$ 45,100.00$

01 57 00 20 Erosion Control LS 1 10,000.00$ 10,000.00$

01 50 00 30 Temporary Work Access LS 1 5,000.00$ 5,000.00$

SUBTOTAL 60,100.00$

REPAIR ITEMS

02 30 00 40 Slab Removal SF 300 200.00$ 60,000.00$ 31 00 00 50 Structural Excavation CY 60 200.00$ 12,000.00$ 31 00 00 60 Granular Structure Backfill CY 60 300.00$ 18,000.00$ 31 00 00 70 Furnish Micropile Equipment LS 1 75,000.00$ 75,000.00$ 31 00 00 80 Micropiles EA 12 15,000.00$ 180,000.00$ 31 00 00 90 Micropile Verification Load Test EA 1 20,000.00$ 20,000.00$ 31 00 00 100 Micropile Proof Load Test EA 2 2,000.00$ 4,000.00$ 03 30 00 110 Structural Concrete CY 8 1,800.00$ 14,400.00$

03 20 00 120 Reinforcement, Grade 60 LB 3,000 2.50$ 7,500.00$

SUBTOTAL 390,900.00$

SUBTOTAL OF ITEMS 451,000.00$

PE SERVICES @ 30% 135,300.00$

CE SERVICES @ 30% 135,300.00$

SUBTOTAL OF BIDDABLE ITEMS, PE, AND CE 721,600.00$

SUBTOTAL OF BIDDABLE ITEMS, PE, AND CE (rounded) 722,000.00$

ACCURACY LOW RANGE @ -15% 614,000.00$

ACCURACY LOW RANGE @ +50% 1,083,000.00$

River Well #1 Building

City of Bend

DOWL Project No. 2190.14934.01

Engineer's Opinion of Probable Cost

Building Repair Alternative - Micropile Repair with Slab Replacement

September 2023

Spec.

Sec. No. Item Unit Quantity Unit Price Total Price

BUILDING ACCESS

10 Mobilization (@ 10% subtotal of items) LS 1 62,900.00$ 62,900.00$

01 57 00 20 Erosion Control LS 1 10,000.00$ 10,000.00$

01 50 00 30 Temporary Work Access LS 1 5,000.00$ 5,000.00$

SUBTOTAL 77,900.00$

REPLACEMENT ITEMS

02 30 00 40 Building Removal SF 300 300.00$ 90,000.00$ 31 00 00 50 Structural Excavation CY 30 200.00$ 6,000.00$ 31 00 00 60 Granular Structure Backfill CY 5 300.00$ 1,500.00$ 31 00 00 70 Furnish Pile Driving Equipment LS 1 80,000.00$ 80,000.00$ 31 00 00 80 Furnish Steel Piles FT 300 200.00$ 60,000.00$ 31 00 00 90 Drive Steel Piles EA 4 3,000.00$ 12,000.00$ 31 00 00 100 Steel Pile Splices EA 4 1,500.00$ 6,000.00$ 03 30 00 110 Structural Concrete CY 50 1,800.00$ 90,000.00$

03 20 00 120 Reinforcement, Grade 60 LB 20,000 2.50$ 50,000.00$

06 00 00 130 Timber Roof SF 320 300.00$ 96,000.00$

- 140 Building Mechanical & Electrical (@ 4%) LS 1 30,000.00$ 30,000.00$

- 150 Openings & Finish Work (@ 4%) LS 1 30,000.00$ 30,000.00$

SUBTOTAL 707,300.00$

SUBTOTAL OF ITEMS 785,000.00$

PE SERVICES @ 30% 235,500.00$

CE SERVICES @ 30% 235,500.00$

SUBTOTAL OF BIDDABLE ITEMS, PE, AND CE 1,256,000.00$

SUBTOTAL OF BIDDABLE ITEMS, PE, AND CE (rounded) 1,256,000.00$

ACCURACY LOW RANGE @ -15% 1,068,000.00$

ACCURACY LOW RANGE @ +50% 1,884,000.00$

River Well #1 Building

City of Bend

DOWL Project No. 2190.14934.01

Engineer's Opinion of Probable Cost

Building Replacement Alternative - CIP Concrete Building

September 2023

ATTACHMENT B:

GEOTECHNICAL EXPLORATION

SUMMARY

TWG23L023 Page 1 of 6 June 9, 2023

62915 NE 18th Street, Suite 1, Bend, OR 97701 p | 541.382.4707 f | 541.383.8118 wallacegroup-inc.com

June 9, 2023

DOWL

c/o Mr. Jim Albin 963 SE Simpson Ave., Suite 200 Bend, Oregon 97702

Subject: Geotechnical Exploration Summary

City River Well No. 1 341 SW Shevlin Hixon Drive Bend, Oregon

Project No. 23044-1

Dear Mr. Albin:

The Wallace Group completed a geotechnical exploration to evaluate the subsurface conditions adjacent to the City River Well No. 1, located on SW Shevlin Hixon Drive in Bend, Oregon. We understand that the City of Bend has observed signs of foundation distress of the pump house building, which appears to have progressed in the past two years. Based on information provided by DOWL (Client), the River Well No. 1 building was constructed in approximately

1972. We understand that DOWL will be preparing repair recommendations and our findings will be incorporated into the repair documents.

The purpose of our geotechnical exploration and analysis was to evaluate subsurface conditions and material properties of the foundation materials located adjacent to the River Well No. 1 building. The Wallace Group used the results of our subsurface explorations to develop conclusions regarding the cause of settlement and options for repair. A Vicinity Map is shown in

Figure 1.

SUBSURFACE EXPLORATION

Subsurface conditions at the site were explored by drilling two borings (designated B-01 and B-

02) adjacent to the well building. B-01 was drilled south of the existing building, and B-02 was drilled north of the building. The Exploration Location Map is presented on Figure 2. Borings

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62915 NE 18th Street, Suite 1, Bend, OR 97701 p | 541.382.4707 f | 541.383.8118 wallacegroup-inc.com were drilled on April 24 and 25, 2023, and were advanced to depths ranging between approximately 41- to 50-feet below ground surface (bgs) using mud-rotary drilling techniques.

The geotechnical borings were drilled by Western States Soil Conservation Inc., of Hubbard, Oregon. Approximate boring locations are shown on Figure 2, Exploration Location Map.

Wallace Group geotechnical professionals observed the drilling, standard penetration tests

(SPT), collected samples, and visually classified the materials encountered. The boring logs in

Appendix A describe the materials encountered at each location explored. The soil types between explorations are anticipated to be similar; however, some variation should be expected. The stratigraphic contacts indicated at each exploration represent the approximate boundaries between soil and bedrock types.

A more complete description of the exploration methods, sampling techniques and depths, and soil classification terminology is presented in Appendix A, Field Exploration Summary.

LABORATORY TESTING

Soil samples were transported to our Bend geotechnical laboratory where they were visually-classified according to the Unified Soil Classification System (USCS). The classification is based on the ‘finer fraction’ of soil and gravel particles smaller than three-inches in diameter.

Representative samples were tested to evaluate soil engineering properties. The tests were completed in general accordance with the following standards:

• ASTM D2488 – Classification of Soil for Engineering Purposes,

• ASTM D2974 – Organic Content, and

• ASTM D2435– Consolidation Test.

The results of laboratory testing are presented in Appendix B.

SUBSURFACE CONDITIONS

Irrigated lawn surfaces were underlain by loose undocumented fill materials in both boring locations that contained high to very high organic content. The undocumented fill materials extended from the surface to depths ranging between approximately 1.5- to 4.5-feet below ground surface (bgs). Below the undocumented fill materials, alluvial deposits consisting of interbedded layers of sand, gravel, and silt were encountered. The alluvium extended to depths ranging between approximately 21- to 27.5-feet bgs and was generally medium dense to very dense. Very soft, saturated tuff deposits were encountered below the alluvium in both exploration locations. The saturated tuff was completely weathered and exhibited no welding

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62915 NE 18th Street, Suite 1, Bend, OR 97701 p | 541.382.4707 f | 541.383.8118 wallacegroup-inc.com or structure and instead consisted of free ash and pumice clasts. The weathered tuff extended to depths ranging between approximately 40.5- to 44-feet bgs and was underlain by dense gravel alluvium to the maximum depths explored.

Landscaping and Undocumented Fill

Irrigated lawn surfaces were underlain by organic soil and undocumented fill materials in both exploration locations. The undocumented fill materials extended from the surface to depths ranging from approximately 1.5- to 4.5-feet bgs. The undocumented fill materials were composed of organic material, wood chips, and metal debris contained within a silt and sand soil. The undocumented fill material was generally very loose to medium dense, blackish brown with orange to gray mottling, and was fine to coarse grained. Organic content of the fill ranged from 4.7 to 21.1 percent by weight.

Alluvial Sand, Gravel, and Silt

Alluvium was encountered below the undocumented fill materials in both exploration locations.

The alluvium extended to depths ranging between approximately 21- to 27.5-feet bgs and was generally medium to very dense. The stratum consisted of numerous interbedded layers gravel, sand, and silt which reflect the variable depositional energy of the adjacent Deschutes River.

The material was fine to coarse grained, subangular to subrounded, moist to wet, and was blackish brown to tannish red and gray. Organic content of the alluvial layer ranged from 1.0 to

1.2 percent.

Decomposed Tuff

Below the alluvium, saturated decomposed tuff was encountered that was very soft. This layer ranged in thickness from approximately 16.5- to 19.5-feet and extended to depths ranging from approximately 40.5- to 44-feet bgs. The material was completely weathered and exhibited very low strength based on the Standard Penetration Tests (SPT’s). Recovered samples had the appearance of fine ash with pumice clasts. The material was tannish to orangish white, fine grained, and very moist to completely saturated. A relatively undisturbed shelby tube sample was collected in B-01 and, based on consolidation testing, indicates the material is still consolidating (the layer is expected to settle even if new loads are not added).

Alluvial Gravel

Below the saturated tuff, very dense alluvial gravel, cobble, and sands were encountered which extended to the limits of our exploration at depths between 41.3- to 50.4-feet bgs. The material was wet, subangular to rounded, and was fine to coarse grained.

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Groundwater

In B-01, groundwater was measured at a depth of approximately 25.4-feet. Due to the mud-rotary drilling techniques used, groundwater depth was not easily discerned from B-02, but we anticipate it will be similar to B-01.

FLOOR LEVEL SURVEY

A floor level survey was performed by Wallace Group on May 9, 2023 using a water level manometer. Spot elevations of the interior floor slab were measured at building corners and areas where building distress was observed. Based on the results of the survey and evaluation of the contours, floor slab settlement has occurred throughout the well house building with the highest elevation adjacent to the well casing and the lowest elevation near the northwest corner. Between the well casing and the exterior edges of the building, approximately 1.1- to

3.5- inches of differential settlement was measured.

CONCLUSIONS AND DISCUSSION

Based on the results of the floor level survey and evaluation of the settlement contours, subsurface explorations, laboratory testing, and engineering analyses, two potential causes of settlement of the well house include organic decomposition of the upper 1.5- to 4.5-foot-thick fill layer and consolidation of the very soft decomposed tuff.

Estimated Future Settlement

The well house building has experienced a significant amount of settlement and additional settlement will occur as the organic material decays. Organic contents measured in the upper

1.5- to 4.5-feet range 4.7 to 21.1 percent and Wallace Group estimates that an additional 1- to

8- inches of settlement should be expected, dependent on the layer thickness.

The laboratory consolidation test results indicate that the decomposed tuff is still consolidating.

Even if new fill or loads are not added, the site will continue to settle as a result of primary consolidation. Based on the decomposed tuff thickness and an overconsolidation ratio of 0.47, Wallace Group estimates that an additional 13- to 17-inches of consolidation settlement is expected.

Estimates of total settlement caused by organic decay and consolidation settlement ranges between 14- to 25-inches within the footprint of the well house, where at least 3.5-inches of differential settlement has already occurred.

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Downdrag Forces

As the soil settles around the well casing, negative skin friction will be imposed on the well casing in the layer above the dense gravel (encountered at depths ranging between 40.5- to 44-feet bgs). Therefore, we recommend that the structural capacity of the well and well casing are evaluated based on negative skin friction values of 645 pounds per square foot (psf) in the upper sand and gravel and 970 psf in the decomposed tuff.

Mitigation Measures

The high point observed on the slab adjacent to the well casing indicates that the well is not experiencing settlement while the surrounding ground surface, floor slab, and well house continue to settle. In order the mitigate settlement of the well house, deep foundation elements would be needed which extend into the competent material below the very soft tuff

(greater than 45- to 50-feet bgs). Because the installation of deep foundation elements is likely cost prohibitive for the existing structure, alternative mitigation options include: 1) leaving the structure in place and minimizing potential damage to the existing well or 2) demolition and construction of a new well house.

Provided the structural capacity of the existing well and casing can adequately withstand the anticipated downdrag loads, the first mitigation option includes cutting the floor slab adjacent to the well casing to allow the slab and surrounding surface to settle without adding an additional load to the casing. The structural evaluation performed by DOWL (project structural engineer) should be used to determine if the structure can remain or needs to be replaced. If the existing structure remains in place, continued structural monitoring should occur and continued repairs should be expected.

If a new structure is constructed, the new well house should be constructed using deep foundation elements. Wallace Group can provide recommendations for deep foundation elements, if needed.

CLOSING

The services provided, as described in this summary letter, have been performed according to generally accepted engineering and design practices that exist in central Oregon at the time the work was performed. No warranty, express or implied, is provided.

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We sincerely appreciate the opportunity to provide our professional services and trust this work meets the project design team requirements. If any questions arise concerning this letter, please contact our Bend office at (541) 382.4707.

Respectfully submitted, Wallace Group, Inc.

Lisa M. Splitter, P.E., G.E.

Senior Geotechnical Engineer

Adam Larson, P.E.

Project Geotechnical Engineer

ATTACHMENTS:

Figure 1: Vicinity Map Figure 2: Exploration Location Map Appendix A: Boring Logs Appendix B: Laboratory Results Appendix C: Photographs

FIGURES

APPENDIX A

TWG23R026 Page 1 of 8 June 9, 2023

APPENDIX A

FIELD EXPLORATION SUMMARY

GENERAL

Subsurface conditions for the City of Bend Well #1 project, located in Bend, Oregon, were explored were explored by drilling two (2) borings (designated B-01 and B-02), at locations shown on Figure 2, Exploration Location Map. Geotechnical boring logs are included in this appendix. The exploration program was completed on April 24, 2023. The procedures used to drill the borings and collect soil samples, and other field techniques are described in detail in this appendix. Unless otherwise noted, all soil sampling and classification procedures followed local engineering practices, which are in general conformance with relevant ASTM procedures and the Unified Soil Classification System (USCS). “General conformance” means that certain local and common drilling and descriptive practices and methodologies have been followed.

BORINGS

Two (2) borings were drilled adjacent to the well house by Western States Soil Conservation, Inc. of Hubbard, Oregon. The borings were drilled to depths of between approximately 41- to

50-feet bgs with a Central Mining Equipment (CME) 75 track-mounted drilling rig. Borings were advanced using mud-rotary drilling and sampling techniques. Borings were abandoned in accordance with Oregon Water Resources Department requirements by backfilling the borehole with bentonite.

MATERIAL DESCRIPTIONS

Soil samples were visually classified in the field as they were collected. Consistency, color, relative moisture, degree of plasticity, and other distinguishing characteristics of the samples were noted. Afterwards, the samples were re-examined in the laboratory, various standard classification tests were conducted, and the field classifications were modified where necessary. The terminology used in the soil classifications and rock descriptions are defined beginning on Page 3 and are included under material description on each log.

BORING LOGS

Figure A is a Legend explaining the information and symbols presented on the boring logs. The logs of the borings are presented on Figures A-1 through A-2. The logs describe the materials encountered and the depths where materials and/or characteristics of these materials changed, although the changes may be gradual. Where material types and descriptions changed between samples, the contacts were interpreted. On each boring log, the types of samples collected

(including their identification number) are reported, including laboratory test results, and SPT

TWG23R026 Page 2 of 8 June 9, 2023 blow counts. Corrected SPT blowcounts, presented on the boring logs, have been corrected for sampler type and hammer energy.

GROUNDWATER

Groundwater was measured in B-01 at a depth of 25.4-feet below ground surface during subsurface exploration for this project.

TWG23R026 Page 3 of 8 June 9, 2023

TERMINOLOGY USED TO DESCRIBE SOIL AND ROCK

Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based upon total dry weight, is the primary soil type and is capitalized in our log descriptions, e.g., SAND, GRAVEL, SILT or CLAY. Lesser percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the Visual-Manual Procedure (ASTM D2488-93). “General Accordance” means that certain local and common descriptive practices have been followed. In accordance with ASTM D2488, group symbols (such as GP or CH) are applied on that portion of the soil passing the 3-inch

(75mm) sieve based upon visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils.

Fine - Grained SOILS (More than 50% fines passing 0.074 mm, #200 sieve) The primary soil type i.e. SILT or CLAY is designated through visual – manual procedures to evaluate soil toughness, dilatancy, dry strength, and plasticity. The following describes the terminology used to describe fine - grained soils and varies from ASTM 2488 terminology in the use of some common terms.

Primary soil NAME, adjective and symbols

Plasticity Description

Plasticity Index (PI)

SILT

ML & MH

CLAY

CL & CH

ORGANIC

SILT & CLAY

OL & OH

SILT Organic SILT Non-plastic 0 - 3

SILT Organic SILT Low plasticity 4 - 10

Clayey SILT Silty CLAY Organic clayey SILT Medium Plasticity

>10 – 20

Clayey SILT CLAY Organic silty CLAY High Plasticity >20 – 40

Clayey SILT CLAY Organic CLAY Very Plastic >40

Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:

Description % Composition

Trace sand, trace gravel 5% - 10%

With sand; with gravel 15% - 25%

Sandy, or gravelly 30% - 45%

TWG23R026 Page 4 of 8 June 9, 2023

Borderline Symbols, for example CH/MH, are used where soils are not distinctly in one category or where variable soil units contain more than one soil type. Dual Symbols, for example CL-ML, are used where two symbols are required in accordance with ASTM D2488.

Soil Consistency. Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 4).

Descriptive terms are based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows.

Consistency Term SPT N-value Unconfined Compressive Strength Tons/sq.ft. kPa

Very soft Less than 2 Less than 0.25 Less than 24 Soft 2 - 4 0.25 - 0.5 24 - 48 Medium stiff 5 - 8 0.5 - 1.0 48 – 96 Stiff 9 - 15 1.0 - 2.0 96 – 192 Very stiff 16 - 30 2.0 - 4.0 192 – 383 Hard Over 30 Over 4.0 Over 383

Note: For SILT with low to non-plastic behavior, (i.e., PI < 4) a relative density description is applied.

Coarse-Grained Soils (less than 50% fines)

Coarse-grained soil descriptions, i.e., SAND or GRAVEL, are based on that portion of materials passing a 3-inch (75mm) sieve. Coarse-grained soil group symbols are applied in accordance with ASTM D2488 based upon the degree of grading, or distribution of grain sizes of the soil.

For example, well graded sand containing a wide range of grain sizes is designated SW; poorly graded gravel, GP, contains high percentages of only certain grain sizes. Terms applied to grain sizes follow.

Particle Diameter

Inches Millimeters

Sand (S) 0.003 - 0.19 0.075 - 4.8

Gravel (G) 0.19 - 3.0 4.8 - 75

Additional Constituents

Cobble 3.0 - 12 75 - 300

Boulder 12 - 120 300 - 3050

Rock Block >120 >3050

The primary soil type is capitalized, and the amount of ‘fines’ in the soil are described as indicated by the following examples. Other soil mixtures will provide similar descriptive names.

TWG23R026 Page 5 of 8 June 9, 2023

Example: Coarse-Grained Soil Descriptions with Fines

5% fines

10% fines

(Dual Symbols) 15% to 45% fines

GRAVEL with trace silt: GW or GP GRAVEL with silt, GW-GM Silty GRAVEL: GM

SAND with trace clay: SW or SP SAND with clay, SP-SC Silty SAND: SM

Additional descriptive terminology applied to coarse-grained soils follow.

Coarse-Grained Soil Containing Secondary Constituents

Clean < 5% fines With sand or with gravel 15% - 25% sand or gravel Sandy or gravelly 30% - 45% sand or gravel With cobbles; with boulders Any amount cobbles or boulders.

Additional terms may be used to describe amount including abundant, scattered.

Cobble and boulder deposits may include a description of the matrix soils, as defined above.

Relative Density terms are applied to granular, non-plastic soils based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586.

Relative Density Term SPT N-value

Very loose 0 - 4

Loose 4 - 10

Medium dense 10 - 30

Dense 30 - 50

Very dense > 50

TWG23R026 Page 6 of 8 June 9, 2023

Terminology Used to Describe Rock

Scale of Rock Strength

Description Designation

Unconfined Compressive Strength, psi

Unconfined Compressive Strength, MP

Field Identification

Very low strength R1 100 – 1000 0.7 – 7 Crumbles under firm blows with point of geology pick; can be peeled by a pocketknife.

Low strength R2 1,000 – 4,000 7 – 28 Can be peeled by a pocketknife with difficulty;

shallow indentation made by firm blows of geology pick.

Moderate strength R3 4,000 – 8,000 28 – 55 Cannot by scraped or peeled with a pocketknife; specimen can be fractured with a single firm blow of geology hammer.

Medium high strength

R4 8,000 – 16,000 55 – 110 Specimen requires more than one blow with a geology hammer to fracture it.

High strength R5 16,000 – 32,000 110 – 120 Specimen requires many blows of geology hammer to fracture it.

Very high strength

R6 > 32,000 > 220 Specimen can only be chipped with geology pick.

Descriptive Terminology for Joint Spacing or Bedding

Descriptive Term Spacing of Joints

Very close Less than 2 inches < 50 mm Close 2 inches - 1 foot 50 mm – 300 mm

Moderately close 1 foot - 3 feet 300 mm – 1 m Wide 3 feet -10 feet 1 m – 3 m

Very wide Greater than 10 feet > 3 m

Descriptive Terminology for Vesicularity

Descriptive Term Percent voids by volume

Dense < 1% Slightly vesicular 1 – 10%

Moderately vesicular 10 – 30% Highly vesicular 30 – 50%

Scoriaceous > 50%

TWG23R026 Page 7 of 8 June 9, 2023

Correlation of RQD and Rock Quality

Rock Quality Descriptor RQD Value

Very poor 0 – 25 Poor 25 - 50 Fair 50 - 75

Good 75 - 90

TWG23R026 Page 8 of 8 June 9, 2023

SCALE OF ROCK WEATHERING

Stage Description Quality Distinction

Fresh Rock is fresh, crystals are bright, a few joints may show slight staining because of ground water.

No Discoloration

Very Slight Rock is generally fresh, joints are stained, some joints may have thin clay coatings, crystals in broken faces show bright.

Discoloration only on major discontinuity surfaces i

Slight Rock is generally fresh, joints are stained, and discoloration extends into rock up to 1 in. Joints may contain clay. In granitoid rocks some feldspar crystals are dull and discolored. Rocks ring under hammer if crystalline.

Discoloration on all discontinuity surfaces and on rock

Moderate Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull and discolored; some are clayey. Rock has dull sound under hammer and shows significant loss of strength as compared with fresh rock.

Decomposition and/or disintegration < 50% of rock ii

Moderately Severe All rock, except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority show kaolinization. Rock shows severe loss of strength and can be excavated with geologist’s pick.

Rock goes “clunk” when struck.

Decomposition and/or disintegration > 50%, but not complete

Severe All rock, except quartz, discolored or stained. Rock “fabric” is clear and evident but reduced in strength to strong soil. In granitoid rocks, all feldspars kaolinized to some extent. Some fragments of harder rock usually left, such as corestones in basalt.

Decomposition and/or disintegration > 75%, nearly complete

Very Severe All rock, except quartz, discolored or stained. Rock “fabric” is discernible, but mass effectively reduced to “soil” with only fragments of harder rock remaining.

Decomposition and/or disintegration 100% with structure/fabric intact

Complete Rock is reduced to “soil”. Rock “fabric” is not discernible, or only in small scattered locations. Quartz may be present as dikes or stringers.

Decomposition and/or disintegration 100% with structure/fabric destroyed

NOTES: i Discontinuities consist of any natural break (joint, fracture or fault) or plane of weakness (shear or gouge zone, bedding plane) in a rock mass ii Decomposition refers to chemical alteration of mineral grains; disintegration refers to mechanical breakdown iii Stage and description from ASCE Manual No. 56 (1976), quality distinction from Murray (1981)

CLIENT DOWL

PROJECT NUMBER 23044-1

PROJECT NAME City River Well #1

PROJECT LOCATION Bend, OR

ABBREVIATIONS

Standard Penetration Test

Shelby Tube

SAMPLER SYMBOLSLITHOLOGIC SYMBOLS

(Unified Soil Classification System)

WELL CONSTRUCTION SYMBOLS

KEY TO SYMBOLS

Water Level After 24 Hours, or as Shown

Water Level at End of Drilling, or as Shown

TV

PID

UCCS

ppm

FILL: Fill (artificial fill)

GM: USCS Silty Gravel

GP: USCS Poorly-graded Gravel

GP-GM: USCS Poorly-graded Gravel with Silt

ML: USCS Silt

SM: USCS Silty Sand

SP-SM: USCS Poorly-graded Sand with Silt

TOPSOIL: Topsoil

LL

PI

MC

DD

NP

FINES

PP

OC

LIQUID LIMIT (%)

PLASTIC INDEX (%)

MOISTURE CONTENT (%)

DRY DENSITY (PCF)

NON PLASTIC

PERCENT PASSING NO. 200 SIEVE

POCKET PENETROMETER (TSF)

ORGANIC CONTENT (%)

TORVANE

PHOTOIONIZATION DETECTOR

UNCONFINED COMPRESSION

PARTS PER MILLION

Water Level at Time of Drilling, or as Shown

K E

Y T

O S

Y M

B O

LS

W A

LL

A

C E

G R

O U

P D

A T

A T

E M

P

LA

T E

.G D

T

/8

/2

:0

W :\G

IN

T

P R

O

F

IL

E S

\B E

N T

LE

Y

\G

IN

T \P

R O

JE

C

T S

\2

-1

C

IT

Y R

IV

E

R W

E

LL

1.

G P

J

Wallace Group Inc.

62915 NE 18th Street, Suite 1 Bend, OR 97701

Figure: A

SPT

S-1

SPT

S-2

SPT

S-3

SPT

S-4

SPT

S-5

SPT

S-6

SPT

S-7

SPT

S-8

SPT

S-9

SPT

S-10

SPT

S-11

SPT

S-12

SPT

S-13

OC: 2.1%

OC: 3.4%

OC: 1.0%

SM

SP-

SM

GP

ML

0.3

1.5

6.0

27.5

Green, grass sod SILTY SAND, gravel, moist, blackish brown with orangeish gray, fine to coarse grained, subangular to rounded, black organic lenses, [FILL] POORLY GRADED SAND WITH SILT AND GRAVEL, loose to medium dense, moist, blackish brown with whiteish red, fine to coarse grained, subangular to rounded, volcaniclastic grains

POORLY GRADED GRAVEL WITH SAND, medium dense to very dense, moist, brownish gray with whiteish red, fine to coarse grained, subangular to rounded, volcaniclastic grains

SILT WITH SAND, very soft, wet, orangeish yellow to brownish yellow, weathered tuffaceous pumice

NOTES

GROUND ELEVATION

LOGGED BY KAK

DRILLING METHOD CME 55

DRILLING CONTRACTOR Western States Soil Conservation Inc. GROUND WATER LEVELS:

CHECKED BY LMS

DATE STARTED 4/24/23 COMPLETED 4/24/23

AT TIME OF DRILLING 25.40 ft

24HRS AFTER DRILLING ---

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

BORING NUMBER B-01

CLIENT DOWL

PROJECT NUMBER 23044-1

PROJECT NAME City River Well #1

PROJECT LOCATION Bend, OR

T W

G -B

O R

IN

G

L O

G S

W

A

LL

A C

E G

R O

U P

D A

T A

T E

M P

LA

T

E .G

D T

/9 /2

:1

W

:\G

IN

T P

R O

F

IL

E

S \B

E N

T

LE

Y \G

IN

T

\P R

O

JE

C T

S \2

-1 C

IT

Y

R

IV

E R

W E

LL

.G

P J

Wallace Group Inc.

62915 NE 18th Street, Suite 1 Bend, OR 97701

B

LO

W C

O U

N T

S

C or re ct ed N

-V al ue

TESTS

U

.S .C

.S

G R

A P

H

IC

LO

G

MATERIAL DESCRIPTION

Figure: A - 1.1

S-14

SPT

S-15

ST

S-16

SPT

S-17

SPT

S-18

50/5"

60/5"

ML

GM

44.0

50.4

SILT WITH SAND, very soft, wet, orangeish yellow to brownish yellow, weathered tuffaceous pumice (continued)

SILTY GRAVEL WITH SAND, very dense, wet, grayish brown with brownish white, fine to coarse grained, subangular to rounded, volcaniclastic grains

Bottom of borehole at 50.4 feet.

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

BORING NUMBER B-01

CLIENT DOWL

PROJECT NUMBER 23044-1

PROJECT NAME City River Well #1

PROJECT LOCATION Bend, OR

T W

G -B

O R

IN

G

L O

G S

W

A

LL

A C

E G

R O

U P

D A

T A

T E

M P

LA

T

E .G

D T

/9 /2

:1

W

:\G

IN

T P

R O

F

IL

E

S \B

E N

T

LE

Y \G

IN

T

\P R

O

JE

C T

S \2

-1 C

IT

Y

R

IV

E R

W E

LL

.G

P J

Wallace Group Inc.

62915 NE 18th Street, Suite 1 Bend, OR 97701

B

LO

W C

O U

N T

S

C or re ct ed N

-V al ue

TESTS

U .S

.C .S

G R

A P

H

IC

LO

G

Figure: A - 1.2

S-1

SPT

S-2

SPT

S-3

SPT

S-4

SPT

S-5

SPT

S-6

SPT

S-7

SPT

S-8

SPT

S-9

SPT

S-10

OC: 4.7%

OC: 21.1%

OC: 1.2%

SM

SM

GP-

GM

GP

ML

GP-

GM

ML

0.3

4.5

6.0

9.0

16.0

17.5

21.0

Green, grass sod SILTY SAND, moist, brown, fine to coarse grained, subangular to subrounded, organic chips, metal shavings, [FILL]

SILTY SAND WITH GRAVEL, medium dense, moist, blackish brown with reddish gray, fine to coarse grained, subangular to rounded

POORLY GRADED GRAVEL WITH SILT AND SAND, very dense, moist, blackish brown with tannish red, fine to coarse grained, subangular to rounded, volcaniclastic grains

POORLY GRADED GRAVEL WITH SAND, medium dense, moist, blackish brown with red, fine to coarse grained, subangular to rounded, volcaniclastic grains

SILT WITH SAND, silt, moist, brown, fine grained

POORLY GRADED GRAVEL WITH SILT AND SAND, medium dense, moist, blackish brown with reddish gray, fine to coarse grained, subangular to rounded, volcaniclastic grains

SILT WITH SAND, very soft, very moist to wet, tannish white to orangeish white, fine grained, weathered tuffaceous pumice

NOTES

GROUND ELEVATION

LOGGED BY KAK

DRILLING METHOD CME 55

DRILLING CONTRACTOR Western States Soil Conservation Inc. GROUND WATER LEVELS:

CHECKED BY LMS

DATE STARTED 4/24/23 COMPLETED 4/25/23

AT TIME OF DRILLING ---

24HRS AFTER DRILLING ---

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

BORING NUMBER B-02

CLIENT DOWL

PROJECT NUMBER 23044-1

PROJECT NAME City River Well #1

PROJECT LOCATION Bend, OR

T W

G -B

O R

IN

G

L O

G S

W

A

LL

A C

E G

R O

U P

D A

T A

T E

M P

LA

T

E .G

D T

/9 /2

:1

W

:\G

IN

T P

R O

F

IL

E

S \B

E N

T

LE

Y \G

IN

T

\P R

O

JE

C T

S \2

-1 C

IT

Y

R

IV

E R

W E

LL

.G

P J

Wallace Group Inc.

62915 NE 18th Street, Suite 1 Bend, OR 97701

B

LO

W C

O U

N T

S

C or re ct ed N

-V al ue

TESTS

U

.S .C

.S

G R

A P

H

IC

LO

G

Figure: A - 2.1

S-11

SPT

S-12

50/3"

83/9"

ML

GP

40.5

41.3

SILT WITH SAND, very soft, very moist to wet, tannish white to orangeish white, fine grained, weathered tuffaceous pumice (continued)

POORLY GRADED GRAVEL WITH SAND, cobbles, very dense, wet, blackish gray, fine to coarse grained, subangular to rounded

Bottom of borehole at 41.3 feet.

S A

M P

LE

T

Y P

E N

U M

B E

R

D E

P T

H (f t)

BORING NUMBER B-02

CLIENT DOWL

PROJECT NUMBER 23044-1

PROJECT NAME City River Well #1

PROJECT LOCATION Bend, OR

T W

G -B

O R

IN

G

L O

G S

W

A

LL

A C

E G

R O

U P

D A

T A

T E

M P

LA

T

E .G

D T

/9 /2

:1

W

:\G

IN

T P

R O

F

IL

E

S \B

E N

T

LE

Y \G

IN

T

\P R

O

JE

C T

S \2

-1 C

IT

Y

R

IV

E R

W E

LL

.G

P J

Wallace Group Inc.

62915 NE 18th Street, Suite 1 Bend, OR 97701

B

LO

W C

O U

N T

S

C or re ct ed N

-V al ue

TESTS

U .S

.C .S

G R

A P

H

IC

LO

G

Figure: A - 2.2

APPENDIX B

4/24 - 4/25/23 23044 - 1

WGG0311

4/27/2023

B-01 B-01 B-01

1.5' 3' 6'

Sand w/ Silt and Gravel Sand w/ Silt and Gravel Gravel w/ Sand

5704.6 5134.2 6030.3

5701.0 5120.1 6025.5

5530.5 4715.3 5530.0

174.1 418.9 500.3

170.5 404.8 495.5

Percent Moisture 27.7% 29.4% 13.7%

97.9 96.6 99.0

2.1 3.4 1.0

B-02 B-02 B-02

0' 1.5' 7.5'

Silty Sand Silty Sand Gravel w/Silt and Sand

5907.7 4821.6 6244.8

5889.9 4799.2 6236.4

5530.6 4715.3 5530.2

377.1 106.3 714.6

359.3 83.9 706.2

Percent Moisture 26.2% 103.2% 11.6%

95.3 78.9 98.8

4.7 21.1 1.2

Wt Dish & Dry Soil

Wt Dish & Ash

Wt of Dish

Wt of Dry Soil

Wt of Ash

Percent Ash

Percent Organics

Percent Organics

Location

Depth

Percent Ash

ASTM D-2974

ORGANIC CONTENT BY IGNITION

Location

Depth

Description

Date Analyzed:

DOWL

City River Well #1

PJH

LMS

Remarks: Furnace Temp. Used: 540° C

Moisture Content by proportion of oven-dried mass

Note: Data and results shown above include ASTM Test Method D-2974. This report pertains only to the material testedand/or inspected and is not to be reproduced without prior authorization of Wallace Group. If part of a larger document, this report is not to be removed or reproduced separately. This report is the property of the Client and shall not be distributed to other parties without Client's permission.

Client:

Project Name:

Technician:

Reviewed By:

Date Sampled:

Project No.:

Lab No.:

Description

Wt Dish & Dry Soil

Wt Dish & Ash

Wt of Dish

Wt of Dry Soil

Wt of Ash

62915 NE 18th St, Ste 1

Bend, OR 97701

541.382.4707 www.wallacegroup-inc.com

Revised 03/08/23

APPENDIX C

TWG23R026 Figure D-1 June 9, 2023

Existing site conditions. View looks southeast.

Drilled boring explorations performed with tracked CME drilling rig.

TWG23R026 Figure D-2 June 9, 2023

Mud-rotary drilling techniques were used for borings.

B-01 split-spoon sample from 3-feet bgs. Note dark brown to black organic material.

TWG23R026 Figure D-3 June 9, 2023

B-01 split-spoon sample at 35-feet bgs. Note saturated weathered tuff.

B-02 cuttings. Note wood shaving debris.