Site work for a water / sewer project in Aurora, Colorado. Completed plans call for site work for a water / sewer project.

As of January 16, 2024, a general contractor has been awarded and construction is underway. It is anticipated construction will be completed by summer 2024. *The closed solicitation has been included below for reference: Source ID PU.AG.USA.1028.C5891301 Piggyback Contract No Question Acceptance Deadline 06/23/2023 04:00 PM EDT Questions are submitted online No The Project for the construction of a buried vault that will connect Pressure Zone 5 (PZ5) to Pressure Zone 4 (PZ4) with a pressure reducing valve (PRV) which will control flow between the two zones, and to provide system redundancy and a backup supply to the Southeast Area Maintenance (SEAM) Facility. The project is located near the intersection of E. Jewell Avenue and future South Powhaton Road intersection. The vault adds operational flexibility and greater reliability in selectively delivering water sources to current and future customers. The new buried concrete PRV vault will be approximately 420-SF and will house the required pipe connections, piping, and PRVs and will be accessed through roof hatches. There are also two butterfly valve vaults with manholes and a tunnel across E Jewell Ave is needed to make the connection between between PZ5 and PZ4. The electrical, instrumentation, and control systems will enable the PRV vault to be powered and controlled remotely through the Owner's existing fiber-based control network. GENERAL STATEMENT OF WORK The Project for the construction of a buried vault that will connect Pressure Zone 5 (PZ5) to Pressure Zone 4 (PZ4) with a pressure reducing valve (PRV) which will control flow between the two zones, and to provide system redundancy and a backup supply to the Southeast Area 1908 S. Powhaton Rd, Aurora, CO 80018, NW 1/4 Section 28 Township 4S Range 65W. This PRV will be located on the southeast corner of the future proposed intersection of E Jewell Ave and the future Powhaton Rd, Right-of-Way (ROW). This project has considered that the future intersection will be a six-lane arterial road with future landscape vegetation and sidewalk buffer according to the standard six-lane arterial road cross-section per City of Aurora (City) Standards and Specifications. This project does not include design and therefore construction of the Powhaton Road and Jewell Avenue roadway intersection. Deferral for the construction of Powhaton Road and Jewell Avenue will include the design and construction of the stormwater facilities including stormwater quality, storm drainage and stormwater detention. This project connects the existing dead-end of Pressure Zone 5 waterline to Pressure Zone 4 waterline and will provide additional system redundancy to the feeding Pressure Zone 4 for various future development projects to the north and east of the project location. The construction work will consist open-trench installation of approximately 300 linear feet (LF) of 30-inch, 24-inch and 16-inch waterline, connections to existing system waterline, 3 below grade butterfly valve vaults, a cast-in-place PRV vault, and a trenchless installation of 30-inch waterline crossing E Jewell Ave. A new concrete pad with an instrumentation panel will be placed above grade on the southeast corner of the future intersection. All pipeline, appurtenances, and instrumentation will be installed in City ROW. The existing gravel entrance will be removed and replaced with a new gravel road to provide access to the PRV Vault location. The total disturbed area for this project is 0.93 acres, so a Stormwater Management Plan (SWMP) Report or Preliminary Drainage Plan are not required, per the City of Aurora Rules and Regulations Regarding Stormwater Discharges Associated with Construction Activities. The installation of the new pipelines and vaults will not result in any significant changes to the existing project site conditions, and all grades will be returned to the pre-construction grading at the completion of construction. Grading, Erosion and Sediment Control Plans will be provided as part of the project delivery and will reference the appropriate Best Management Practices (BMPs) in accordance with City of Aurora Standards. None of the disturbed areas in this project are located within the floodway. Please reference the project drawings for additional information BURNS^MCDONNELL Digitally signed by Kate Henske DN: C=US, LZ ofo I--IoKiO Ixo E=khenske@burnsmcd.com, r\.ate^nenSke O=Burns & McDonnell Engineering, CN=Kate Henske Date: 2023.04.10 15:18:58-06'00' Aurora Water Janet Bender, PE Page 2 9785 Maroon Circle \ Centennial, CO 80112 O 303-721-9292 \ F 303-721-0563 \ burnsmcd.com regarding this project. A FEMA FIRMette centered on the project site is included for with this letter. If you should have any comments or questions regarding this project please contact me at (303) 474-2208, khenske@burnsmcd.com. Sincerely, Burns & McDonnell Engineering Company, Inc. Kate Henske, PE Senior Project Engineer Attachment: National Flood Hazard Layer FIRMette cc: Catherine Schumacher, PE - City of Aurora Steve Fiori, PE - City of Aurora FACSIMILE This electronic plan is a facsimile of the signed and sealed pdf set. r '* >T4S R65WS21 11 i 11 i i 5623'1 TEETi I lZtJfieTAE: U 662*. 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FLOODWAY) FZu'ne'AEflHH L' 513****~ WFEMA 1 TFJT S1' .,Y - IBs i1 1 CITYpFAURORA nsnnn-___________ 1SI L1 *^ o I % NationalFloodHazardLayerFIRMette 0 250 500 1,000 1,500 2,000 Feet U SEEFISREPORTFORDETAILEDLEGENDANDINDEXMAPFORFIRMPANELLAYOUT SPECIALFLOOD HAZARDAREAS WithoutBaseFloodElevation(BFE) ZoneA,V,A99 WithBFEorDepthZoneAE,AO,AH,VE,AR RegulatoryFloodway 0.2%AnnualChanceFloodHazard,Areas of1%annualchancefloodwithaverage depthlessthanonefootorwithdrainage areasoflessthanonesquaremileZoneX FutureConditions1%Annual ChanceFloodHazardZoneX AreawithReducedFloodRiskdueto Levee.SeeNotes.ZoneX AreawithFloodRiskduetoLeveeZoneD NOSCREENAreaofMinimalFloodHazard ZoneX AreaofUndeterminedFloodHazardZoneD Channel,Culvert,orStormSewer Levee,Dike,orFloodwall CrossSectionswith1%AnnualChance 17.5 WaterSurfaceElevation CoastalTransect CoastalTransectBaseline ProfileBaseline HydrographicFeature BaseFloodElevationLine(BFE) EffectiveLOMRs LimitofStudy JurisdictionBoundary DigitalDataAvailable NoDigitalDataAvailable Unmapped ThismapcomplieswithFEMA'sstandardsfortheuseof digitalfloodmapsifitisnotvoidasdescribedbelow. ThebasemapshowncomplieswithFEMA'sbasemap accuracystandards Thefloodhazardinformationisderiveddirectlyfromthe authoritativeNFHLwebservicesprovidedbyFEMA.Thismap wasexportedon11/2/2022at11:30AManddoesnot reflectchangesoramendmentssubsequenttothisdateand time.TheNFHLandeffectiveinformationmaychangeor becomesupersededbynewdataovertime. Thismapimageisvoidiftheoneormoreofthefollowingmap elementsdonotappear:basemapimagery,floodzonelabels, legend,scalebar,mapcreationdate,communityidentifiers, FIRMpanelnumber,andFIRMeffectivedate.Mapimagesfor unmappedandunmodernizedareascannotbeusedfor regulatorypurposes. Legend OTHERAREASOF FLOODHAZARD OTHERAREAS GENERAL STRUCTURES OTHER FEATURES MAPPANELS 8 B 20.2 Thepindisplayedonthemapisanapproximate pointselectedbytheuseranddoesnotrepresent anauthoritativepropertylocation. Engineering from the ground down GEOTECHNICAL INVESTIGATION REPORT FINAL AURORA ZONE 5 TO ZONE 4 PRV AT JEWELL AND POWHATON AURORA, COLORADO May 2023 LITI-KS ENGINEERING LITH^S ENGINEERING j'c 59501 mX 2750 S. Wadsworth Blvd, Suite D-200 Denver, Colorado 80227 303.625.9502 www.LithosEng.com May 23, 2023 Project No. 22066 Burns & McDonnell 9785 Maroon Circle Suite 400 Centennial, Colorado 80112 Attention: Kate Henske, PE, Senior Project Manager Brett Holzapfel, Project Manager Regarding: Geotechnical Engineering Investigation Report - Final Aurora Zone 4 to Zone 5 PRV at Jewell & Powhaton Aurora, Colorado Ms. Henske and Mr. Holzapfel, Submitted herewith is the Geotechnical Engineering Investigation Report for the Aurora Zone 5 to Zone 4 PRV project. This study was conducted in general accordance with our contract between Lithos Engineering and Burns & McDonnell dated October 19 th , 2022. This report contains the results of our findings, an engineering interpretation with respect to the available project characteristics, and recommendations to aid design and construction of earth-related phases of this project. If you have any questions regarding the contents of this report, please contact the undersigned. Sincerely, Lithos Engineering Rob Johanson, EI Adam Pring, PE Staff Engineer Project Engineer Nate Soule, PE, PG Principal Additionally reviewed by: Ryan Marsters, Project Manager 05/23/23 LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page i of ii TABLE OF CONTENTS 1 INTRODUCTION & PROJECT BACKGROUND..................................................................................1 2 REGIONAL GEOLOGY...................................................................................................................1 3 GEOTECHNICAL INVESTIGATION..................................................................................................1 3.1 Subsurface Investigation...............................................................................................................1 3.2 Geotechnical Laboratory Testing ..................................................................................................2 3.2.1 Corrosion Potential Testing...................................................................................................2 4 SUBSURFACE CONDITIONS..........................................................................................................3 4.1 Subsurface Materials ....................................................................................................................3 4.1.1 Eolian Deposits......................................................................................................................3 4.1.2 Coarse Alluvium ....................................................................................................................3 4.1.3 Denver Formation Bedrock...................................................................................................3 4.2 Groundwater.................................................................................................................................4 5 GEOTECHNICAL DESIGN RECOMMENDATIONS.............................................................................4 5.1 Foundation Recommendations.....................................................................................................4 5.2 Lateral Earth Pressures.................................................................................................................5 5.3 Frost Protection ............................................................................................................................5 5.4 Geotechnical Parameters for Counteracting Buoyancy................................................................5 5.5 Surface and Subsurface Drainage .................................................................................................6 5.6 Corrosion.......................................................................................................................................6 5.7 Pipeline Recommendations..........................................................................................................6 5.7.1 Differential Movement .........................................................................................................6 5.7.2 Thrust Restraint.....................................................................................................................6 5.7.3 Modulus of Soil Reaction (E')................................................................................................7 6 CONSTRUCTION CONSIDERATIONS..............................................................................................7 6.1 Temporary Excavations.................................................................................................................7 6.1.1 Permanent Slopes.................................................................................................................8 6.2 Site Grading and Earthwork ..........................................................................................................8 6.2.1 Site Preparation ....................................................................................................................8 6.2.2 Structure and Trench Backfill Material .................................................................................9 6.2.3 Pipe Bedding .........................................................................................................................9 6.2.4 Fill Placement and Compaction ............................................................................................9 6.3 Bedrock or Oversized Material Excavation.................................................................................10 6.4 Construction Dewatering............................................................................................................10 6.5 Unstable Subgrade Conditions....................................................................................................10 6.6 Trench Plugs................................................................................................................................11 7 LIMITATIONS ............................................................................................................................11 REFERENCES ....................................................................................................................................12 LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page ii of ii LIST OF FIGURES Figure Number Title 1 Site Vicinity 2 Boring Location Map APPENDICES Appendix Title A Standard Geotechnical Drilling Key and Boring Logs B Geotechnical Laboratory Testing Results C Laboratory Corrosion Results LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 1 of 12 1 INTRODUCTION & PROJECT BACKGROUND The City of Aurora (Aurora) is planning the installation of a pressure reducing valve (PRV) as part of the Zone 5 to Zone 4 PRV project (Project). The PRV is intended to control flow between Pressure Zone 5 and Pressure Zone 4 of the Aurora transmission and distribution system and connect existing pipelines to service development north and east of the Project site. The Project includes the installation of approximately 358 feet of new waterline and a valve vault to house the PRV. The installation will include a tunnel crossing under East Jewell Ave with the alignment located east of South Powhaton Rd. The crossing will be approximately 60 feet of 30-inch-diameter steel waterline at 8.30% slope downwards from south to north. Initial support for the crossing will include a 42-inch-diameter steel casing pipe. The Project location is shown in Figure 1 at the end of this report. Burns & McDonnell (BMcD) retained Lithos Engineering (Lithos) to function as the Project's geotechnical engineer. The purpose of this report is to provide the results of the geotechnical investigation and provide geotechnical recommendations for design and construction of various project elements. 2 REGIONAL GEOLOGY Geologic mapping performed by Trimble and Machette (1979) indicates the site is underlain by Holocene to Pleistocene-aged Windblown (Eolian) Sands and Pleistocene-aged Louviers Alluvium. Alluvium (stream deposited) is described as gravel, sand, silt, and clay. Windblown Sand is described as fine to medium sand that is derived from alluvium of major nearby streams. Bedrock in the area is mapped as Paleocene to Cretaceous-aged Denver Formation. Bedrock is described as claystone, siltstone, sandstone, and conglomerate with a unit thickness of 920 feet. 3 GEOTECHNICAL INVESTIGATION Lithos conducted a geotechnical investigation at the project site on December 1, 2022. The geotechnical investigation included geotechnical drilling and a subsequent geotechnical laboratory testing program. Lithos completed a total of 2 geotechnical test boreholes ("borings") to investigate the general subsurface conditions, including 1 boring on the north side of Jewell Avenue and 1 boring on the south side of Jewell Avenue near the proposed PRV vault. A boring location map is shown in Figure 2 at the end of this report. 3.1 Subsurface Investigation Geotechnical borings were advanced to depths of 35 feet below the existing ground surface (bgs). Lithos subcontracted Vine Laboratories to drill the borings utilizing a buggy mounted CME 750 drilling rig. Drilling and sampling procedures were conducted in general accordance with ASTM D3440 - Standard Practice for Thick Wall, Ring-Lined, Split Barrel, Drive Sampling of Soils. Continuous-flight, solid-stem augers were used to advance borings below the existing ground surface through soil and into the bedrock. During advance of the solid-stem augers, Modified California samples (2.0-inch inner diameter) were obtained at 5-foot and 2.5-foot intervals. The number of blows by a 140-pound hammer falling 30 inches required for 12 inches of sampler penetration (recorded in 6-inch increments) are presented on the boring logs (Appendix A). The boring near the proposed PRV vault was developed as a temporary monitoring well. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 2 of 12 3.2 Geotechnical Laboratory Testing A geotechnical laboratory testing program was developed by Lithos and conducted by Martinez Associates in Golden, Colorado and Project X in Murrieta, California on representative samples collected during the subsurface investigation. A laboratory summary table and graphical testing results are provided in Appendix B. Laboratory tests conducted in general accordance with associated ASTM standards are presented in the table below. Geotechnical Laboratory Testing Test Standard Grain Size Distribution ASTM D422/ASTM C136 #200 Sieve Wash ASTM D1140 Atterberg Limits ASTM D4318 Moisture Content ASTM D2216 Dry Density ASTM D2937 If field characterized soil and bedrock descriptions differed from results indicated by laboratory classification testing, the boring logs presented in Appendix A were amended to reflect laboratory testing results. 3.2.1 Corrosion Potential Testing Corrosion laboratory tests conducted in general accordance with associated ASTM and AASHTO standards are presented in the table below. Corrosion Laboratory Testing Test Standard Chloride AASHTO T291-91/ASTM D4327 pH AASHTO T289-91 Redox Potential ASTM G200 Sulfate-Water Soluble AASHTO T290-91/ASTM D4327 Sulfide SM 4500-S2 Resistivity AASHTO T288-91 Ammonia ASTM D4327 Nitrate ASTM D4327 Fluoride SM 2320B Phosphate ASTM D4327 Lithium ASTM D4327 Sodium ASTM D4327 Potassium ASTM D4327 Magnesium ASTM D4327 Calcium ASTM D4327 LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 3 of 12 4 SUBSURFACE CONDITIONS Subsurface conditions were assessed based on the findings of the geotechnical investigation described in the previous section. Soil and rock descriptions noted on the boring logs and below are in general accordance with ASTM D 2487 - Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) and D 2488 - Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). 4.1 Subsurface Materials Primary materials encountered during the subsurface investigation include eolian deposits, coarse alluvium, and claystone, siltstone, and sandstone bedrock of the Denver Formation. Boring logs and a supplementary boring log key explaining boring log details are provided in Appendix A. 4.1.1 Eolian Deposits Eolian deposits were encountered in all borings generally at the ground surface and extended to depths from 17.5 to 19.0 feet bgs. Encountered eolian deposits were described as the following in accordance with the United Soil Classification System (USCS): o Silty Sand (SM) o Poorly graded sand with silt (SP-SM) Eolian deposits were primarily comprised of sand with varying amounts of silt. Blow counts ranged from 19 blows per foot (bpf) to 41 bpf correlating to a relative density of medium dense to dense. Eolian deposits are not anticipated to be at risk of swelling since high plasticity clays were not encountered; thus, no swell testing was completed. Eolian deposits are not anticipated to be at risk of collapse because of their relative density, therefore no collapse testing was completed. 4.1.2 Coarse Alluvium Coarse alluvium was encountered in all borings at depths ranging from 17.5 to 19.0 feet bgs and extended to depths of 34.8 feet bgs and the end of exploration. Encountered coarse alluvium was described as the following in accordance with USCS: o Poorly graded sand (SP) o Poorly graded sand with silt (SP-SM) o Clayey Sand (SC) Coarse alluvium consisted of primarily sand with varying amounts of silt and clay. Blow counts ranged from 16 bpf to 42 bpf correlating to a relative density of medium dense to dense. 4.1.3 Denver Formation Bedrock Claystone bedrock of the Denver Formation was encountered in boring LE-2 MW at a depth of 34.8 feet below the existing ground surface. The bedrock was soft, slightly to moderately weathered, greenish black to black, and very fine grained. No lab testing was performed on the bedrock due to the limited sample size. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 4 of 12 4.2 Groundwater Groundwater was encountered during the subsurface investigation in boring LE-2 MW at 23.7-feet bgs. A temporary monitoring well was installed in boring LE-2 MW for additional monitoring. The table below presents initial groundwater levels in the boring and groundwater fluctuations in the monitoring well as measured after drilling. Natural fluctuations in the groundwater level may occur due to variations in rainfall, temperature, site development, and other factors not evident at the time that these measurements were made. 5 GEOTECHNICAL DESIGN RECOMMENDATIONS The following sections are included primarily for the engineer performing design. If additional geotechnical design recommendations are necessary or site construction differs from the assumptions included herein, Lithos should be contacted to provide or modify relevant information. 5.1 Foundation Recommendations Based on our understanding of the proposed valve vault and the results of our subsurface investigation, we anticipate the valve vault will bear at least 11 feet deep within medium dense to dense coarse eolian deposits. We recommend the valve vault utilize a shallow foundation supported on onsite Select Fill (as defined in section 6.2.2) or imported CDOT class 1 structure backfill. Lithos recommends the following criteria be utilized in design of the spread footings or mat foundation elements: o The foundations should be designed using a maximum allowable bearing pressure of 3,000 psf This value includes appropriate allowable-stress-design (ASD) safety factors. o The foundations should be designed to withstand a total settlement of 1 inch and differential settlements of 0.5 inches. o Sliding friction between anticipated subgrade and foundation materials should be evaluated using a coefficient of 0.35. o The coefficient of subgrade reaction (k) is typically used for flexible foundation analysis and describes the load intensity per unit of displacement. For recompacted onsite fill or structural backfill, a k value of 125 psi/in is recommended. Groundwater Readings Boring Groundwater Level (feet bgs) 12/1/22 1/10/23 05/23/23 LE-2 MW 23.7 23.5 22.7 LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 5 of 12 5.2 Lateral Earth Pressures Lateral earth pressures presented below should be considered during the structural design process for foundation elements extending below grade. Lateral earth pressure values are a function of the properties and the geometry of the retained fill, soil, and/or bedrock and anticipated magnitude of lateral deflection. In addition, the presence of groundwater and saturated materials will increase the total horizontal stress, resulting in higher lateral earth pressures in comparison to retained materials above a groundwater table. Static Lateral Earth Pressures Backfill Material Type Unit Weight (pcf) Friction Angle (degrees) Static Earth Pressure Coefficients Static Equivalent Fluid Pressure (pcf) Active At-Rest Passive Above GWT 1 Below GWT 1 Above GWT 1 Below GWT 1 Above GWT 1 Below GWT 1 Active At-Rest Passive CDOT Class 1 Structure Backfill 130 34 0.28 0.44 3.54 37 82 57 92 460 302 Select Fill 125 31 0.32 0.48 3.12 40 82 61 93 391 258 1 GWT stands for Groundwater Table For the lateral earth pressures presented above to remain applicable, backfill material placement adjacent to below-grade walls should be in accordance with procedures outlined in this report. In addition, backfilled material must be placed within a 1 horizontal to 1 vertical (1H:1V) backfill geometry, up and away from the base of the structure. If the excavation is steeper than 1:1, the more conservative values outlined above should be used. Consideration has not been given to vertical loads applied to the backfill surfaces during or after construction as a result of traffic and/or other surcharge loads. The design high groundwater (highwater) elevation should be taken as the 100-yr flood elevation of nearby Senac Creek. 5.3 Frost Protection We recommend that perimeter shallow foundations and shallow foundations in non-heated enclosed areas have a minimum cover of 36 inches for frost protection. 5.4 Geotechnical Parameters for Counteracting Buoyancy Structures and pipelines which extend below the highwater elevation should be evaluated for buoyancy. Where the structure loads are not sufficient to counteract buoyancy, additional resistance to uplift can be achieved by extending the foundation outside the vertical walls and engaging the weight of an additional wedge of soil. For design purposes, the wedge of soil providing resistance on the extended foundation can be defined by including the soil within a 12-degree slope (measured from vertical) up and away from the bottom exterior edge of the extended footing to the ground surface. A saturated unit weight of 125 pcf may be used for the soil wedge if the buoyant force on the structure includes the weight of water displaced by the soil wedge. If the buoyant force on the structure does not include the weight of water displaced by the soil wedge, i.e., only the volume of water that is displaced by the structure itself, then a soil unit weight of 62 pcf should be used. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 6 of 12 Pipelines that do not have enough soil overburden to prevent flotation when empty should be mitigated for buoyancy. The typical method to reduce buoyancy concerns is to encase the pipeline in concrete or flowfill, which adds weight to the system. Another option if concrete is not sufficient is to design tiedowns that are evenly spaced and secured to the pipe. If tie-downs are necessary, Lithos should be contacted to provide appropriate geotechnical design recommendations. 5.5 Surface and Subsurface Drainage Construction details should ensure that surface water does not penetrate utility trenches and migrate beneath the structures. Vegetation should not be located within a distance of 5 feet from structures. Irrigation systems should be arranged so that water under pressure does not spray within 5 feet of foundation walls. 5.6 Corrosion Pipe installation trenches are anticipated to be backfilled with properly compacted granular pipe bedding material. Depending on the specific pipe type selected, the corrosion potential of soils and water surrounding trench backfill should be assessed. Water soluble sulfate testing was conducted on 1 representative sample collected during the site investigation. The test result was 0.0016% which would characterize the risk to concrete as "Not Applicable" as shown in the table below. Complete results of the corrosion test are in Appendix C. These results should be considered when specifying the allowable cement types and concrete mixes. American Concrete Institute Code 318-19(22) Water Soluble Sulfates Class Water-Soluble Sulfate in Soil SO4, Percent by Weight Risk S0 SO4 <0.10 Not Applicable S1 0.10< SO4 <0.20 Moderate S2 0.20< SO4 <2.00 Severe S3 SO4 >2.00 Very Severe 5.7 Pipeline Recommendations 5.7.1 Differential Movement Pipelines excavated through soils will be susceptible to differential movements up to 1 inch. Pipe penetrations into structures should be designed to tolerate a total of 1 inch of upward or downward relative movement. Existing and proposed structures are expected to function as relatively rigid structures, therefore, flexible joints and/or connections between lines and structures are recommended. Allowance for differential movement should be expected and planned for where pipelines penetrate structures. We recommend CLSM (flowable fill) backfill be used in pipe trenches within 10 feet of structures, in lieu of traditional pipe bedding and pipe trench backfill to mitigate the migration of groundwater which could lead to soil movement. 5.7.2 Thrust Restraint Buried, pressurized pipes experience thrust forces at various pipe configurations including tees, reducers, dead ends, valves, bends, and wyes. To balance internal transient pressures, thrust blocks or restrained joints are recommended for pipe restraint and as required by Aurora Water Design Standards Section 11. For thrust block design, an allowable lateral bearing pressure of 1,500 psf is recommended. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 7 of 12 A minimum of 1 foot of cover over thrust blocks is recommended and thrust blocks should be oriented such that the passive pressure influence zones do not overlap for adjacent blocks and do not impact other subsurface utilities. If restrained joints are selected, various coefficients of friction for potential pipe materials against anticipated trench backfill material are presented below. Coefficient of Friction for Buried Pipe Pipe Type Coefficient of Friction Steel 0.30 5.7.3 Modulus of Soil Reaction (E') The modulus of soil reaction (E') is an empirically derived coefficient which is related to the stiffness of the native soils and the nature and degree of compaction of the pipe bedding and backfill material. Various design guidelines specific to pipe material provide recommended values for E'. For full embedment of pipe in compacted granular pipe bedding, where the trench is excavated in soils that are loose/medium stiff or better (stiffer or denser, typically with blow counts greater than 4 blows per foot), and where the trench width measured at the pipe elevation (Bd) is at least 2 times the pipe diameter (D), an E' value as shown in the table below should be used. Modulus of Soil Reaction (E') Pipe Type E' (psi) 0-5ft depth of cover (psi) 5-10ft depth of cover (psi) Steel 1,200 1,800 6 CONSTRUCTION CONSIDERATIONS The following sections are intended for the Engineer producing specifications and the contractor constructing the proposed project. Construction considerations include temporary excavations, preparation of excavated surfaces for foundations, backfill materials, fill placement and compaction, and construction dewatering. 6.1 Temporary Excavations General site safety including temporary excavations are the sole responsibility of the contractor performing construction. Lithos is providing temporary excavation information strictly as an informational benefit to the project team, specifically the general contractor. An Occupational Safety and Health Administration (OSHA) defined competent person should be identified by the contractor to be in charge of temporary excavations. In general, the contractor's competent person should have experience or training in determining soil types, benching and shoring, and have the ability to detect potential temporary slope stability and protective system issues. OHSA defines an excavation as a man-made cut, trench, or depression formed by the removal of earth. A trench is a specific type of narrow excavation with a geometry including a greater depth than width and a width of 15 feet or less. Trenches 5 feet deep or greater should be sloped, retained with shoring, or shielded appropriately. Shielding most commonly includes trench boxes. In general, shoring can include inclined, horizontal, or vertical systems depending on the excavation geometry and availability of retention alternatives. Sloping and benching should be in accordance with OSHA recommendations. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 8 of 12 Benching should include a maximum 4-foot vertical face for each bench and the overall excavation geometry less than or equal to the OSHA defined slope. A registered professional engineer should approve the contractor's approach for trenches greater than or equal to 20 feet in depth. In addition, shoring for trench excavations should be based on tabulated data prepared or approved by a registered professional engineer in accordance with OSHA 1926.652(b) and (c). Lithos has evaluated observed soil conditions likely to be excavated by the proposed construction. Based on the OSHA determined soil Types, the following table presents maximum recommended temporary excavation slopes to be utilized during construction. OSHA Temporary Excavation Slopes Backfill Material Type OSHA Classification Maximum Recommended Slope (H:V) 1,2 Select Fill Type C 1 1/2 :1 1 H:V is an abbreviation for Horizontal:Vertical 2 Valid for trench excavations less than 20 feet in depth During construction, heavy equipment or excavated material stockpiles should be kept away from excavation edges to the extent possible. It is recommended that heavy equipment or excavated material stockpiles be kept at least 10 feet from the edges of excavations. Underground and overhead utilities should be fully understood and documented prior to initiating excavations. Finally, the contractor's competent person should inspect trenches and excavations routinely for signs of instability including sliding, toppling, subsidence and bulging, heaving or squeezing, boiling, and/or other visual concerns. Typically, trench boxes are used to support lateral loads during excavation and construction in soils that have sufficient standup time to excavate the trench, install the trench box, complete installation and remove the trench box without full contact of the soils. Tight shoring typically involves full contact of the soils with the shoring system. Typical tight shoring systems include sheet pile walls, soldier pile and lagging walls, secant pile walls, soil nail walls and slide rail systems. 6.1.1 Permanent Slopes Lithos recommends a maximum slope of 3:1 for permanent cuts and fills. Erosion control may be required for slope stabilization. Erosion control options include erosion control blankets, fiber rolls, reinforcement mats and vegetation. 6.2 Site Grading and Earthwork Appropriate site preparation, material placement and compaction, and backfill selection can reduce the risk of post-construction settlement and potential issues related to lateral earth pressures. General site grading and earthwork considerations are presented in the following sections. 6.2.1 Site Preparation Areas supporting backfill and pipe bedding should be properly prepared. Once the rough grade has been established in excavated areas, and prior to placement of backfill, the exposed subgrade should be carefully inspected via proof rolling, probing, and other testing as determined necessary by the LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 9 of 12 geotechnical engineer. At the time of such observation, it may be necessary to hand auger borings and/or use a hand penetration device in the base of the foundation excavation to confirm that soils below the base are satisfactory for foundation support. The necessary depth of penetration should be established by the geotechnical engineer during observation. Frozen, wet, soft, or loose soil, as well as any other undesirable material should be removed. Once suitable soil conditions are achieved, exposed subgrade soil materials should be scarified and moistened or dried, as necessary, to a minimum depth of 8 inches below the proposed construction. Scarified material should be compacted to the minimum specifications defined in section 6.2.4. 6.2.2 Structure and Trench Backfill Material Backfill is anticipated adjacent to the walls of the valve vault and within pipeline trenches above pipe bedding. Pipeline trenches and foundation walls may be backfilled with Select Fill with no particle size greater than 3 inches, less than 40% fines, a plasticity index (PI) less than 10, and a liquid limit (LL) less than 30 providing that appropriate lateral earth pressures are used in design as outlined in Section 5.2. It is anticipated Select Fill can be generated from screened onsite surficial materials. Claystone should not be used as backfill. Excavated claystone fragments should be screened from Select Fill. If another material is considered for backfill applications, Lithos should be contacted to review submitted particle size distribution and plasticity testing results. CDOT Class 1 Structure Backfill may be used as backfill surrounding foundation walls if desired. CDOT Class 1 Structure Backfill should have a maximum PI of 6, maximum Liquid Limit (LL) of 35, and gradation as shown in the table below: CDOT Class 1 Structure Backfill Sieve Size Percentage Passing 2 inch 100 #4 30-100 #50 10-60 #200 5-20 6.2.3 Pipe Bedding Piping should be bedded in a clean granular material from a depth of minimum of 6 inches below the pipe or 1/4 of the outside diameter of the pipe to 12 inches above the pipe per Aurora Water Standards sections 9.05.3 and 13.09.2. We recommend Pipe Bedding consist of ASTM C33 No. 67 coarse aggregate with less than 5 percent passing the #8 sieve or coarse sand with a maximum size of 3/8-inch and less than 3 percent passing the #200 sieve, per Aurora Water Standards section 9.02. 6.2.4 Fill Placement and Compaction We recommend fill placement occurs in maximum 8-inch loose lifts for fill under and backfill adjacent to structures. Lift thickness for pipe bedding should not exceed 6 inches. Minimum recommended compaction specifications are outlined in the following table. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 10 of 12 Soil Compaction Recommendations Backfill Material Type Moisture and Compaction Specifications Moisture Content 1 Dry Density 2 Relative Density 3 Select Fill -2% to +2% = 95% -- CDOT Class I Structure Backfill -2% to +2% = 95% -- Pipe Bedding -- -- >65% 1 Moisture content relative to the optimum moisture content as determined by ASTM D698 2 Dry density relative to the maximum dry density as determined by ASTM D698 3 Relative density in accordance with ASTM D4263 and D4254. Mechanical compaction is required for all materials placed as backfill during construction. Compaction of cohesive materials is best accomplished with equipment such as a jumping jack or padfoot roller. Non-cohesive soils are best compacted with a vibratory plate or vibratory smooth-drum roller. Compaction utilizing any flooding technique should not be allowed. Care should be taken when compacting fill adjacent to structures. Generally, we recommend operating only light-weight compaction equipment such as jumping jacks and vibratory plates immediately adjacent to structures. Quality assurance of backfill material and backfill placement will be necessary to reduce potential for long-term differential settlements. Inspection of subgrade materials prior to placing or forming and casting structural elements is also critical to project success. Lithos recommends a qualified testing agency is retained to provide quality assurance services during the backfill process. 6.3 Bedrock or Oversized Material Excavation Bedrock was encountered at depths greater than the lowest structure or pipeline element. Bedrock and oversized material excavation is not anticipated during proposed construction activities. The use of standard excavation equipment is anticipated to be sufficient (i.e., no hydraulic breakers or blasting anticipated with a sufficiently sized excavator). 6.4 Construction Dewatering Based upon the observed groundwater levels in LE-2 MW, temporary construction dewatering is not anticipated for the valve vault, tunnel, or shaft construction because these features do not extend below the observed groundwater elevation. The section of the pipeline located in the southwest area of the project site extends to within 3 feet of the observed groundwater elevation. If groundwater is encountered in this section of the excavation, sump pumps will likely be sufficient to control minor groundwater seepage. Groundwater will fluctuate, and more extensive dewatering using trench drains, deep wells, and well points may also be necessary depending on the construction season. Lithos is available to assist with dewatering design if required. Dewatering should be carefully evaluated based upon future groundwater readings by the design team or contractor and accounted for in the construction estimate to avoid construction cost and time increases. 6.5 Unstable Subgrade Conditions If soft/loose pockets or undesirable materials are encountered in the excavations, the proposed excavations may be re-established by backfilling after the deleterious material has been removed. The backfill should consist of CDOT Class 5 or 6 base course. If the base of the excavation is still soft and further excavation is not practical, then a woven geotextile such as Mirafi 600x should be placed prior to LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 11 of 12 backfilling. The backfill should be placed and compacted according to specifications outlined in this report. Field observations by a geotechnical engineer and testing of the open excavations should be performed prior to concrete placement to verify the subgrade conditions and/or to make corrective recommendations, as necessary. 6.6 Trench Plugs Trench plugs should be constructed from impervious material and should be keyed into the in-situ soils along the trench bottom and sidewalls, extending at least 6 inches to 12 inches above the top of the bedding elevation. Trench plugs are recommended to be installed on either side of structures. Trench plugs may be constructed from imported compacted clay soils with a USCS classification of CL or with at least 60 percent fines and a plasticity index of 15 or greater. Trench plugs constructed from clay soils should have a minimum thickness of 2 feet as measured parallel to the pipe. Trench plugs can also be constructed from reinforced concrete, lean concrete, or CLSM (flowable fill). 7 LIMITATIONS This study was conducted in accordance with generally accepted geotechnical engineering and engineering geologic practices and principals; no warranty, express or implied is made. The subsurface conditions described in this report were based on data obtained from widely spaced exploratory borings, geotechnical laboratory testing, information provided by the client, engineering judgement, and our experience with similar subsurface conditions and projects. The boring logs presented in this report only depict the subsurface conditions at the actual boring locations. Subsurface conditions are typically variable, both laterally and vertically, and the nature and extent of the subsurface variations across the site may not become evident until construction. The boundaries between different soil types and bedrock presented in this report are approximate and, in some cases, may be more abrupt or gradational than described herein. Groundwater levels may vary with time, adjacent surface water levels, precipitation, and changes to the hydrogeological conditions at or surrounding the project site. This report has been prepared exclusively for our client for design purposes for the subject project. Lithos Engineering is not responsible for technical interpretations by others of the data presented in this report or use of this report by others for the subject project or other projects. If differing site conditions are encountered during further evaluation of the subsurface conditions by others or during construction, Lithos Engineering should be notified immediately to determine if any changes to our recommendations presented in this report are warranted. The recommendations presented in this report are only intended for the proposed design and construction as understood by Lithos Engineering at the time of issuing this report. If the proposed design and construction changes, Lithos Engineering should be notified immediately and given the opportunity to review the proposed changes and if necessary, modify our recommendations presented herein. An environmental assessment was not included in Lithos Engineering scope of work for this project. Any statements regarding the absence or presence of hazardous and/or toxic substances presented herein are only intended for informational purposes. If the client is concerned about the environmental conditions at the site, Lithos Engineering recommends the client and/or owner retain a qualified environmental firm to conduct an environmental site assessment. LITMUS ENGINEERING Burns & McDonnell Aurora Zone 5 to Zone 4 PRV - GIR Final Page 12 of 12 REFERENCES o ASTM Standards, ASTM International, West Conshohocken, PA (2012). o Aurora Water, 2022, Water, Sanitary Sewer & Storm Drainage Infrastructure Standards & Specifications o Colorado Association of Geotechnical Engineers (CAGE), 1996, Guideline for slab performance risk evaluation and residential basement floor system recommendations, Guideline 1. o Trimble, Donald E. and Machette, Michael N. (1979) Geologic Map of the Greater Denver Area, Front Range Urban Corridor, Colorado, USGS National Geologic Map Database. L I T H ^ S E N G I N E E R I N G F I G U R E S LITH*~S ENGINEERING a BURNS ^MSDONNELL E-470 PROJECT LOCATIONJEWELL AVE P O W H A T O N R D AURORA DENVER METRO PROJECT LOCATION COLFAX AVE E-470 I-25 I-70 I-70 303.625.9502 PROJECT DENVER, COLORADO 80227 2750 S. WADSWORTH BLVD. SUITE D-200 TITLE DRAWING TITLE OWNER CLIENT PROJECT NO.: LOCATION: DATE: DRAWN BY: DESIGNED BY: CHECKED BY: FIGURE NUMBER SITE VICINITY AURORA ZONE 5 TO ZONE 4 PRV 22066 AURORA, CO 01/11/2023 RJ APRM 11 SITE VICINITY -- 0 4000 8000 SCALE: 1" = 4000' 0 10 MI 20 MI SCALE: 1" = 10 MILES T t y L TH^S ENGINEERING BURNS ^MCDONNELL 2+00 2+50 60 LF 42" MIN O TUNNEL ALIGNMENT JEWELL AVE LE-1 PROPOSED PRV VALVE VAULT 0+00 0+50 1+00 1+50 0+50 0+00 LE-2 MW WATERLINE ALIGNMENT LEGEND: LE-XX LE-XX MW APPROXIMATE BORING LOCATION APPROXIMATE MONITORING WELL LOCATION 303.625.9502 PROJECT DENVER, COLORADO 80227 2750 S. WADSWORTH BLVD. SUITE D-200 TITLE DRAWING TITLE OWNER CLIENT PROJECT NO.: LOCATION: DATE: DRAWN BY: DESIGNED BY: CHECKED BY: FIGURE NUMBER BORING LOCATIONS AURORA ZONE 5 TO ZONE 4 PRV 22066 AURORA, CO 01/11/2023 RJ APRM 20 40 80 SCALE: 1" = 40' LITH^S ENGINEERING APPENDIX A Standard Geotechnical Drilling Key and Boring Logs n >> K LITH^S ENGINEERING Soil Classifications: Relative Density or Consistency of Non-cohesive and Cohesive Soils Non-cohesive Soils Cohesive Soils Classification Blows per 12 in Classification Blows per 12 in Very Loose 0 to 4 Very Soft 0 to 2 Loose 5 to 10 Soft 3 to 4 Medium Dense 11-30 Medium Stif 5 to 8 Stif 9 to 15 Dense 31 to 50 Very Stif 16 to 30 Very Dense >50 Hard >30 Description of Odor Description Criteria No Organic Odor Organic odor is not present Trace Organic Odor Mild organic odor; mixture of soil and organics Strong Organic Odor Prominent organic odor; sample is primarily organic Sample Graphics and Descriptions: California Barrel Sampler: Barrel sampler loaded with sample liners and driven to collect a relatively representative and intact specimen of soil or weak rock. Split-Spoon Sampler: Split-barrel sampler driven in accordance with ASTM D1586 used to provide visual material descriptions and collect a disturbed specimen. Groundwater Monitoring Well Graphics: Riser Pipe with Auger Cuttings Well Screen with Silica Sand Riser Pipe with Silica Sand BORINGLOGKEYSTANDARDGEOTECHNICALDRILLINGGradation Estimates by Field Observation Description Quantity (%) Trace <5 Few 5 to 10 Little 15 to 25 Some 30 to 45 Mostly > 50 Color: Sample colors are in general accordance with basic brown, red, yellow, and gray combinations Geologic Interpretation: A Geologic Interpretation of encountered soil and bedrock units is provided for each specific Visual Material Description. Examples of geologic interpretations for soil that may be presented include: FILL, ALLUVIUM, AEOLIAN, AND GLACIAL TILL, AND RESIDUUM. Rock geologic interpretations are referenced based on a combination of field classifications and applicable geologic maps. Riser Pipe with Bentonite Chips Flush Mounted Cap Boring Graphics: Cementation Description Criteria Weak Crumbles with light finger pressure Moderate Crumbles with considerable finger pressure Strong Will not crumble with finger pressure Rock Descriptions: Field Hardness Description Criteria Very Hard Cannot be scratched with a knife or sharp pick. Hard Can be scratched with a knife or pick only with dif iculty Medium Can be gouged 116" deep by firm pressure on knife or pick point Soft Can be grooved or gouged readily with knife or pick point Very Soft Can be carved with knife and scratched readily by fingernail Weathering Description Criteria Fresh No visible sign of rock material weathering: perhaps slight discoloration on major discontinuity surfaces. Slightly Weathered Discoloration of rock material on discontinuity surfaces. Moderately Weathered Less than half of the rock material is decomposed and/or disintegrated to soil. Fresh or discolored rock is present either as a continuous framework or as corestones. Highly Weathered More than half of the rock material is decompsed and/or disintegrated to a soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones Completely Weathered All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact. Texture Description Criteria Very Fine Grained Grains not individually visible to the unaided eye Fine Grained Grains barely visible to the unaided eye, up to 116" diameter Medium Grained Grain diameter between 116" and 316" Coarse Grained Grains diameter between 316" and 14" Very Coarse Grained Grains larger than 14" in diameter 12" Boulders Cobbles Gravel Sand Silts and Clays Coarse Fine Coarse Medium Fine 3" 3/4" 4 10 40 200 300mm 75mm 19mm 4.75mm 2.0mm 0.42mm 0.075mm Clear Square Sieve Openings U.S. Standard Series Sieve Sizes Description of Moisture Description Criteria Dry Absence of moisture, dusty, dry to the touch Moist Damp but no visible water Wet Visible free water, usually soil below the groundwater table Auger Cuttings Stick-Up Well Lean Clay Silt Fat Clay Elastic Silt Well Graded Gravel Poorly Graded Gravel Poorly Graded Sand Sandstone Claystone Well Graded Sand Below are the primary boring log graphics. Any classification combinations will result in a combination of graphics. First Groundwater Reading Second Groundwater Reading Third Groundwater Reading Plasticity Description Criteria Nonplastic A 18" diameter thread cannot be rolled Low A 18" in diameter thread can be rolled with dif iculty; a lump cannot be formed at a moisture lower than the plastic limit Medium A 18" in diameter thread can be rolled easily; a crumbly lump can be formed at a moisture lower than the plastic limit High A 18" in diameter thread can be rolled very easily; a lump can be formed at a moisture lower than the plastic limit Bulk Sample: Bulk or bagged sample taken from auger cuttings. Fill Siltstone L Boring Location: 39.6822, -104.6721 Boring Elevation: 5641 Notes: Location and elevation approximate.