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2025-11-17_Avila Ranch Drainage Report-Berm_ADD#2 - approved
ADDENDUM (BERM OVERFLOW) DRAINAGE REPORT For TRACT 3089 - AVILA RANCH PHASES 2, 3, 4, 5, & 6 FINAL IMPROVEMENTS (Volume 2 of 2) November 2025 Prepared by: Wallace Group 612 Clarion Court San Luis Obispo, CA 93401 805 544-4011 Job Number: 1493-0007 REFERENCE: DRAINAGE REPORT TRACT 3089 - AVILA RANCH PHASES 2, 3, 4, 5, & 6 MASS GRADING PLANS (Volume 1 of 2) April 2023 Approved 01/26/2026 Engineering Development Review Table of Contents Certification ................................................................................................................................. 4 Scope of Work ............................................................................................................................ 4 I. Project Background.................................................................................................................. 5 I.A. Project Description ............................................................................................................ 5 I.B. Project History .................................................................................................................. 6 I.C. Purpose of Addendum ...................................................................................................... 6 III. Hydrologic and Hydraulic Analysis ......................................................................................... 8 III.A. Hydrologic Analysis ......................................................................................................... 8 III.B. Hydraulic Analysis ........................................................................................................... 8 Network Hydraulics, Street Flow, and Inlet Capacity ....................................................... 8 Overland Conveyance Paths ........................................................................................... 8 Storm Drain Culverts (Five-barrel, 18” HDPE) ................................................................. 9 Rock Slope Protection and Erosion Protection .............................................................. 12 Conclusion .................................................................................................................... 13 APPENDIX F ............................................................................................................................ 14 List of Figures Figure 1. Avila Ranch Project Location within the City of SLO ......................................................... 5 Figure 2. Avila Ranch Phase Map .................................................................................................... 6 Figure 3. Overland Conveyance Path .............................................................................................. 9 Figure 4. Stormwater Culverts ........................................................................................................10 Figure 5. Bike Path Flooding in 10-Year Storm Event .....................................................................11 Figure 6: Typical Shore Protection RSP Section (Caltrans HDM Figure 883.2l) ..............................12 List of Appendices Appendix F – Berm Overflow from Chevron Property - Calculations and Exhibits • Avila Ranch Drainage and Flood Study History Memorandum • Overland Escape Path Exhibit • Rock Slope Protection and Run-Up Calculations • HEC-RAS 2 Flood Depth Analysis Results Tables and Exhibits o Table 1 Peak Flows at Cross Sections o Table 2 Maximum Flow Depths at Cross Sections o Table 3 Maximum Flow Water Surface Elevations at Cross Sections o Table 4 Maximum Flow Velocities at Cross Sections o Model Results – No Culverts 10 Year Storm Event 25 Year Storm Event 100 Year Storm Event o Model Results – 5 Barrel 18” HDPE Culverts 10 Year Storm Event 25 Year Storm Event 100 Year Storm Event • HY8 North Jespersen Road Culvert Analysis Results • StormCAD Storm Drain Network Analysis o Storm Drain Network Reference Exhibit o 10 Year Storm Event Hydraulic Results o 25 Year Storm Event Hydraulic Results o 100 Year Storm Event Hydraulic Results Certification Professional Engineers This Addendum to the Volume 2 of 2 Drainage Report for Tract 3089 – Avila Ranch Phases 2, 3, 4, 5, and 6 was prepared by, or under the direction of the following Professional Engineer in accordance with the provisions of Section 6700 of the Business and Professions Code of the State of California. ___________________________________ Rachel Hawthorne, PE C73686 Date Signed: November 17, 2025 Director Civil and Transportation Engineering (Wallace Group) Scope of Work This Addendum includes the following: • Hydraulic analysis of storm drain pipe networks and culverts • Street flow capacity and inlet sizing calculations • Analysis of safe overflow path • Calculations for the sizing of rock-slope protection I. Project Background I.A. Project Description Avila Ranch is a residential development project located within the City of San Luis Obispo, California (see Figure 1). The project includes 149 acres of proposed mixed-use development including single and multi-family homes, commercial areas, parks, and agricultural open space. The project property is bounded by Vachell Lane to the west, Buckley Road to the south, industrial land uses to the north, and agricultural space to the east. The project site is bisected by Tank Farm Creek, which runs from the north edge of the site to the southwest corner. Due to the large scope of the project, the development schedule has been split into six phases. A phase map is seen in Figure 2. Figure 1. Avila Ranch Project Location within the City of SLO Figure 2. Avila Ranch Phase Map I.B. Project History Initially, Avila Ranch and Wallace Group intended to work together with Chevron and TriHydro to design and construct a mutually beneficial overflow spillway and bicycle path at the location of the low point in the existing berm along the southern boundary of the Chevron property. As the Chevron grading plans and related flood zone mapping have been delayed due to additional site investigations of the Chevron property ordered by the Water Board, Avila Ranch has deemed it essential to pursue an alternative design to protect their future development from flood due to overtopping of the Chevron berm. Please refer to the “Avila Ranch Drainage and Flood Study History” memorandum in Appendix F for a summary of the events, meetings, and coordination efforts that led to the shift in drainage strategy for the offsite flow previously understood to be within Tank Farm Creek and now expected to overtop the existing berm on the Chevron property adjacent to the northern tract boundary of Avila Ranch. I.C. Purpose of Addendum The purpose of this memorandum is to document the hydraulic analysis of potential flood impacts resulting from overtopping of the existing Chevron Berm during the 10-, 25-, and 100-year storm events. The existing Chevron Berm on the southern side of the Chevron property is located just north of the Avila Ranch development. The Chevron Berm currently retains some floodwater from Tank Farm Creek. The Chevron Berm overtops in larger storm events, resulting in flooding on the Avila Ranch property. Ultimately, Chevron intends to modify their property and the existing Chevron Berm, with the understanding that peak flows to the Avila Ranch property cannot be increased. Based on discussions with the Chevron team, no onsite or berm improvements will be constructed before the Avila Ranch property is developed. To address this flood risk, Wallace Group is proposing an onsite earthen berm to contain overtopping flows and route flow west to Tank Farm Creek. This onsite earthen berm will be located south or downstream of the existing berm along the southern boundary of Chevron’s property and north/upstream of the multifamily lots in Phase 4 of Avila Ranch. The onsite berm may be removed if Chevron completes improvements to their existing berm. These improvements may include the construction of an armored spillway and concrete bike path. The onsite earthen berm will direct flows along the proposed bike path, over Jespersen Road, and back into Tank Farm Creek. Additionally, this addendum proposes a series of five, 18” HDPE storm drain pipes to be constructed under Jespersen Road just south of the northern tract boundary to reduce the amount of stormwater that would otherwise flow across Jespersen Road and the roundabout at Venture Drive. Wallace Group has developed a HEC-RAS 2D model to analyze the flood affects of the proposed earthen berm with and without the proposed 18” storm drains. An exhibit showing the estimated extents of flood inundation for a 100-year storm event under pre-project conditions, post-project conditions, and post-project conditions with the addition of the onsite earthen berm was also prepared using HEC-RAS 2D and is included in this addendum. During the design of the onsite improvements for the Phase 4 multifamily residential lots, modifications to the points of connection to the storm drain network in Venture Drive were requested by Rick Engineering. In response to City plan review comments on the Phase 5 Improvement Plans, revisions to the alignment and profiles of the storm drain networks within Jespersen Road and Venture Drive were made to increase the depth of pipe cover and reduce the number of waterline lowerings. This addendum provides an update storm drain network analysis for the Venture Drive and Jespersen Road storm drain networks. Wallace Group is also proposing rock slope protection (RSP) to mitigate for erosion of the onsite earthen berm directly across from where the Chevron Berm is most likely to overtop. RSP sizing calculations are included in this Addendum. III. Hydrologic and Hydraulic Analysis III.A. Hydrologic Analysis Chevron Berm overflow values were taken from the existing conditions HEC-RAS 2D model for the Chevron property, developed by TriHydro. The County of San Luis Obispo stated that the existing Chevron Berm overflow values are acceptable and directed Chevron to maintain or reduce these overflow rates with their future improvements. Inflow values for Tank Farm creek were set as constant flow during the 2D model simulation. These values were based on the Phase 2 and 3 LOMR model 10-, 25-, and 100-year flows that have been submitted and approved by FEMA (No. 24-09-1118P). This LOMR became effective July 23, 2025. At the most upstream end of this model, the boundary condition was set using the water surface elevation (WSE) from the LOMR model. 10-year WSE in the creek is 115.13 ft, the 25-year WSE is 115.44 and 100-year WSE is 116.36 ft. III.B. Hydraulic Analysis A flood analysis model was developed using HEC-RAS 2D. The model extents were assigned to represent onsite flooding impacts from overtopping of the Chevron Berm during the 10-, 25-, and 100-year storm events. The terrain data in the model contains both grading design surfaces and topographic survey data from the Avila Ranch development. A 4-foot mesh grid was applied across the model extents to accurately capture the channels and terrain details. Breaklines were included along bank lines, with an additional refinement region within the Tank Farm Creek low-flow channel. There is additional flow entering the model at the existing drainage path that enters Tank Farm Creek from the east. The 10-, 25-, and 100-year flows at this location are 29.5, 34.3, and 51.5 cfs, respectively. Surface roughness values were assigned based on the ultimate land cover conditions outside of the creek. Within Tank Farm Creek, surface roughness values were assigned based on the approved FEMA LOMR model referenced above. Network Hydraulics, Street Flow, and Inlet Capacity The storm drain modifications described above were designed using the methods and criteria described in the approved drainage report for the final improvements. Please refer to Appendix F for the updated calculations and hydraulic grade line profiles. Overland Conveyance Paths Please refer to Figure 3 for an overview of the overflow path for stormwater that may overtop the Chevron berm in large storm events. Flood inundation areas, water surface elevations, velocities, and flow rates for the 10-, 25-, and 100-year storm events for the overflow path were modeled in HEC-RAS 2. Based upon finished floor elevations provided by Rick Engineering on 07/22/25 in the Vesting Tentative Tract Map for the Phase 4 Onsite Improvements, the finished floors are more than 1.0’ above the 100-year water surface elevation when storm water is flowing through the overflow path. The finished floor elevation of the proposed townhome building near the lowpoint in Jespersen Road is 122.5’ and the expected 100-year water surface elevation at that location is 118.6’. At the “Bike Path” cross section, the calculated 100-year water surface elevation is 120.3’ and the nearest adjacent townhome building has a proposed finished floor of 123.5’. Please refer to Figure 3 and Table 3 in Appendix F for additional information. Figure 3. Overland Conveyance Path Storm Drain Culverts (Five-barrel, 18” HDPE) To prevent inundation of the roundabout at Jespersen Road and Venture Drive during a 10 year storm event, a set of five, 18” diameter HDPE culverts have been added under Jespersen Road just south of the tract boundary. The grading of the bike path has been revised to create a low point that funnels stormwater from the Chevron berm to the headwall that serves as an inlet to the five culverts. Please refer to Figure 4. The water surface elevation of Tank Farm Creek in a 100-year storm event near the culvert outlet is approximately 115.8’. To avoid the potential of stormwater from the creek backflowing into the culverts, the flowline of the culverts was designed to be slightly above the creek water surface elevation. This design criteria limited the culvert diameter and vertical clearance from the finished surface of Jespersen Road which was at an approximate elevation of 119.5’ at this location. Figure 5 provides a graphic representation of the limits of ponding in the lowpoint of the bike path upstream of the culvert inlets during a 10-year storm event. The maximum ponding depth on the bike path under these conditions is approximately four inches. Figure 4. Stormwater Culverts Figure 5. Bike Path Flooding in 10-Year Storm Event Rock Slope Protection and Erosion Protection The flow velocity as storm water flows from Jespersen Road and into the creek presents a potential erosion concern. An increase in the velocity of storm water is caused by weir conditions over the road. To mitigate erosion along the sidewalk edge, an 18-inch-deep curb at the pavement edge has been added to Jespersen Road at the overflow location. Additionally, Wallace Group evaluated run-up on the onsite earthen berm for potential impact to Avila Ranch structures. Potential maximum run-up on the berm is equal to the maximum velocity head. The maximum velocity head adjacent to the onsite earthen berm is 0.5 feet in the 100-year storm. Applying a safety factor of 2, a minimum freeboard of 1 foot above the 100-year water surface elevation is required along the onsite earthen berm. As previously stated, model results indicate more than 1.5 feet of freeboard from the 100-year water surface elevation to the onsite earthen berm and pad elevations, adequately mitigating potential run-up impacts. The onsite earthen berm across from the likely Chevron Berm overtopping location (low point) has been designed to be reinforced with 18 inches of Class III (12in, 150lb) RSP placed over RSP fabric or gravel filter. The Caltrans Highway Design Manual was used to design this RSP protection on the onsite earthen berm, and cross checked with the Federal Highway Association (FHWA) HEC-23. See below for a typical section for shore protection RSP. Rock slope protection is included at the outlets of the five-barrel 18” HDPE culverts and at the headwall upstream of the culverts. Additional RSP is proposed at the overflow location of the existing Chevron berm. Figure 6: Typical Shore Protection RSP Section (Caltrans HDM Figure 883.2l) Conclusion Wallace Group analyzed the potential 10-, 25- and 100-year storm event impacts from the overtopping of the existing Chevron Berm and the proposed onsite earthen berm using a HEC-RAS 2D model. The analysis confirms that the proposed onsite earthen berm would provide adequate freeboard to contain the existing Chevron Berm overflow and reduces the area of flood inundation as compared to the approved grading design. The onsite earthen berm is recommended to be reinforced with rock slope protection to help mitigate erosion. Also recommended is an 18-inch- deep curb on Jespersen Road to mitigate potential erosion as flow is conveyed across the road to Tank Farm creek. The installation of the five-barrel 18” HDPE storm drains culverts crossing under Jespersen Road have sufficient capacity to prevent the flood inundation of Jespersen Road during a 10-year storm event. Based upon the results of the updated StormCAD network analysis, the proposed storm drain networks within Venture Drive and Jespersen Road meet the design criteria for the primary storm event. APPENDIX F Appendix F – Berm Overflow from Chevron Property - Calculations and Exhibits • Avila Ranch Drainage and Flood Study History Memorandum • Overland Escape Path Exhibit • Rock Slope Protection and Run-Up Calculations • HEC-RAS 2 Flood Depth Analysis Results Tables and Exhibits o Table 1 Peak Flows at Cross Sections o Table 2 Maximum Flow Depths at Cross Sections o Table 3 Maximum Flow Velocities o Model Results – No Culverts 10 Year Storm Event 25 Year Storm Event 100 Year Storm Event o Model Results – 5 Barrel 18” HDPE Culverts 10 Year Storm Event 25 Year Storm Event 100 Year Storm Event • HY8 North Jespersen Road Culvert Analysis Results • StormCAD Storm Drain Network Analysis o Storm Drain Network Reference Exhibit o 10 Year Storm Event Hydraulic Results o 25 Year Storm Event Hydraulic Results o 100 Year Storm Event Hydraulic Results MEMORANDUM Trumark Construction Services, Inc. Avila Ranch – 1493-0007 Date: August 8, 2025 To: Dan Garson, Trumark Construction Services, Inc. From: Rachel Hawthorne, RCE 73686 Subject: Avila Ranch Drainage and Flood Study History The summary of events, meetings, and coordination efforts below is intended to provide a project history that explains the shift in drainage strategy for the offsite flow previously understood to be within Tank Farm Creek and are now expected to overtop the existing berm on the Chevron property adjacent to the northern tract boundary of Avila Ranch. On June 2, 2021, the representatives of Avila Ranch (formerly Wathen Castanos, now Trumark Construction Services, Inc.) and Wallace Group met with City Staff to discuss the drainage strategy and FEMA processing for Phases 2-6 of Avila Ranch. During that meeting, City Staff shared that the Phase 1 Chevron CLOMR was expected to include the area just north of Tank Farm Road and the Phase 2 Chevron CLOMR may include areas south of Tank Farm Road. A copy of the Chevron CLOMR application was provided to the meeting attendees by City Staff. It was noted that San Luis Obispo County Staff reviewing the Chevron CLOMR application had noted possible inconsistencies between the Chevron as-built grading plans and the 2014 Avocet Flood Study. The following week, June 9, 2021, representatives of Avila Ranch and Wallace Group met with representatives from Chevron and their Engineering Consultant, TriHydro. Chevron and TriHydro provided an update on the status of their remediation work which included a grading plan that was under review by the County of San Luis Obispo. TriHydro was in the process of upgrading their flood analysis model to match the existing work done, modelling as-built for area north of Tank Farm and proposed condition for south of Tank Farm. This model was intended to be re-submitted to the City for review of the CLOMR application after addressing comments provided by the City. TriHydro shared their intent to remap the flood zone on the Avila Ranch property. Wallace Group noted that the CLOMR/LOMR prepared for Avila Ranch would not include remapping or study of the flood zone on the Chevron property. On June 14, 2021, as requested by Chevron, Wallace Group sent follow up questions regarding the status of the CLOMR/LOMR applications, revised hydrologic analysis, as-built improvements, remediation work, and the Tank Farm Creek outlet structure. Chevron responded in December of 2021 that a report would be available in 30-45 days. August 8, 2025 Page 2 of 4 With coordination assistance from County Staff, a meeting was held on Thursday, June 30, 2022 that was attended by representatives of Avila Ranch, Wallace Group, the City, the County, and TriHydro. Below is a summary of key discussion items from that meeting: • Existing historical floodways were impacted by the unpermitted improvements on the Ferris property. Changes on the Ferris site that divert floodwaters from Tank Farm Creek to the Chevron Tank farm and potentially spilling to Avila Ranch include eliminating one of two culverts, and fill in flood flow paths. • City is considering adding flooding impacts to the current Code Enforcement Case against Ferris. • Based upon 2017 FEMA topography, it appears that Tank Farm Creek would overtop the berm at the southern boundary of the Chevron property in the 10- year and larger storm events. Flow will also overtop Ferris. Based on the 2017 FEMA topo, the overflow elevations appear about equal (contour 121), but the path is wider over the Chevron Berm to Avila Ranch. • No CLOMR has been submitted for the southern portion of the Chevron property. A CLOMR has been submitted for Avila Ranch Phases 2-6 and a CLOMR/LOMR has been submitted and approved for Avila Ranch Phase 1 (RRM). • The amount of potential storage behind the berm is approx. 80 ac-ft based upon the 2014 Avocet Report. If the berm is taller than 6 feet and has potential to store more than 50 acre-feet, it would fall under DSOD jurisdiction. City Staff suggested that the berm could be considered a levee under FEMA regulations. • Wallace Group/Avila Ranch requested that Chevron/TriHydro address the stability of the berm if water is to be stored on the north side of the berm. This would include the addition of a concrete spillway at an elevation of 121 feet and a potential low-flow storm drain pipe through the berm to reduce the duration that stormwater was ponded upstream of the berm. • TriHydro was modeling the 100-year storm event upstream of the berm using the 2017 FEMA topo. It is anticipated that the TriHydro model will be available for distribution to the City, Wallace Group, and Avial Ranch by the end of July 2022. Wallace Group requested that TriHydro also provide the results of a 10- year storm event. TriHydro indicated that they would do this. • Avila Ranch will request access to the Ferris property for Wallace Group surveyors to survey the existing headwall and culvert at Ferris. The results of this survey are expected to be shared with the meeting attendees in mid to late July. • City Staff shared the future alignment of the bike path along the western boundary of the Chevron property from Tank Farm Road to the tract boundary of Avila Ranch. It was agreed that the alignment of the bike path may be revised to accommodate the drainage design. Wallace Group shared the alignment of the bike path on the Avila Ranch property which follows the north boundary from Jespersen to below the Chevron Berm low point, and the concept that it was being considered as a flood overflow path. August 8, 2025 Page 3 of 4 o To maintain the overflow path and elevation at the berm, the bike path would need to go over the berm rather than cutting through the berm at an elevation lower than 121. In January 2025, Avila Ranch and Wallace Group had not received an updated model from TriHydro and we contacted the County of San Luis Obispo for a status update. County Staff shared that additional contaminants were located on the Chevron property which were potentially beyond the originally proposed remediation and that the County had not received an updated submittal of the flood analysis or grading plans from Chevron/TriHydro. At the request of Avila Ranch, County Staff coordinated a meeting with Chevron, TriHydro, the City, the County, Avila Ranch, and Wallace Group. Below is a summary of key discussion items from that meeting held on January 30, 2025: • Chevron representatives declined the invitation to attend this meeting. • Avila Ranch is planning to construct Phase 4 in 2026-2027 • The Water Board has issued an order for site investigations on the Chevron property. TriHydro expects to submit the results of the investigation to the Water Board in June 2025. • The grading design and modeling work for the CLOMR on the Chevron site are on hold until comments on the results of the site investigation are received from the Water Board. • TriHydro does not anticipate submittal of a CLOMR to FEMA prior to June 2027. • The future bike path connecting from the northern boundary of Avila Ranch to Tank Farm Road through the Chevron property is the responsibility of the Chevron property Developer/Buyer. • TriHydro expressed concern over channelizing the overflow on the Avila Ranch property and acknowledged that they had no control over the Avila Ranch property. Wallace Group shared that bike paths are frequently built with the 100-year floodplain or 100-year overland escape paths. • TriHydro confirmed that the flow over the berm in the final conditions will match or be less than the flow in current conditions. • TriHydro stated that geotechnical analysis of the berm has been performed, and results show that the berm is stable under current conditions including ponding up to the top of the berm. A copy of the Berm Stability Analysis report conducted in 2022 was provided to Wallace Group and Avila Ranch by TriHydro on 2/20/2025. • City Staff will confirm the status of the code enforcement action on the Ferris property and determine what, if any, grading and drainage modifications that affect the amount of flow overtopping the berm or flowing across Horizon Lane are to be performed by Ferris. On 2/6/2025, City Staff informed Wallace Group and Avila Ranch that the District Attorney was moving forward with an item against Ferris and that item was scheduled for court in February 2025. We have not received an update on the outcome of the District Attorney’s action. August 8, 2025 Page 4 of 4 • Avila Ranch requested an additional meeting with Chevron representatives to discuss a potential interim grading solution for the Avila Ranch project and shared their intent to cooperate with all parties. • TriHydro agreed to assist in facilitating a meeting with Chevron representatives and requested that Avila Ranch provide their project schedule and intent of the requested meeting with Chevron in writing. TriHydro would coordinate the meeting with the Chevron legal team. This meeting has not yet been coordinated as Wallace Group and Avila Ranch decided to have the proposed berm improvements reviewed by City Staff prior to meeting with Chevron. PI : 3 2 + 5 5 . 8 3 ' PC : 3 9 + 8 2 . 0 9 ' P R C : 4 0 + 0 3 . 7 3 ' PI: 17+67.23' PC: 21+65.53' PR C : 2 2 + 7 2 . 2 2 ' 1.50% 1. 5 0 % V V V V XVXVXVXVXVX XXXXXXXXXXXXXXXXXXXXXX X X X X X X X X X X X X X X X X X X 0. 2 5 % 0.25% 0.11% 120 116 117 118 119 121 122 115 120 114 116117118119121 114 1 1 4 121 1 2 2 1 2 2 12 2 1 1 5 1 2 0 1 1 6 1 1 7 1 1 8 1 1 9 12 1 1 2 2 120 120 120 116 117 118 119 121 121 122 122 120 11 8 119 121 122 123 121 122 122 12 2 1 1 7 118 119 119 120 121 1 2 0 12 1 1 2 2 121 122 1 2 0 1 1 9 1 2 1 FG= 1 1 9 . 0 2 FG = 1 1 9 . 3 6 FG = 1 1 9 . 8 1 FG = 1 1 7 . 7 9 HP = 1 1 8 . 4 5 FG = 1 1 8 . 1 4 FG = 1 1 7 . 8 1 FG= 1 2 2 . 2 7 FG = 1 2 1 . 1 3 FG= 1 1 8 . 9 6 FG = 1 2 1 . 4 5 FG = 1 2 1 . 6 8 FG= 1 2 2 . 1 4 FG = 1 2 1 . 2 5 FG = 1 2 1 . 2 5 FG= 1 1 6 . 2 0 FF = 1 2 3 . 5 0 FG= 1 2 2 . 0 1 FF = 1 2 3 . 7 0 FF= 1 2 2 . 7 0 FF= 1 2 2 . 6 0 FF = 1 2 2 . 7 0 FF = 1 2 2 . 7 0 FF = 1 2 3 . 6 0 FF= 1 2 3 . 0 0 FF = 1 2 2 . 7 0 FF = 1 2 2 . 5 0 3 : 1 2:1 3: 1 5: 1 8: 1 6 : 1 0. 8 0 % 1 2 1 12 1 120 117 118 119 117118119 115 116 117 118 119 1 1 5 1 1 3 1 1 4 1 1 5 1 1 6 FF= 1 1 8 . 5 7 FF = 1 1 9 . 4 1 FF= 1 1 9 . 2 3 FF= 1 1 9 . 9 5 FF = 1 2 1 . 5 0 EL E V A T I O N EL E V A T I O N STATION 110 120 130 110 120 130 0+00 0+20 0+40 0+60 0+80 1+00 1+20 1+40 1+53 EL: 1 1 9 . 0 1 T 805 544-4011 F 805 544-4294 612 CLARION COURT SAN LUIS OBISPO, CA 93401 www.wallacegroup.us PLANNING CIVIL AND TRANSPORTATION ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PUBLIC WORKS ADMINISTRATION SURVEYING / GIS SOLUTIONS WATER RESOURCES DESIGNERS: DRAWING NO. DATE: DRAWN BY: JOB #: OF ® DATE SIGNED SIGNATURE These plans and specifications, and the ideas and designs incorporated herein, are instruments of service prepared for the construction of work shown hereon and shall not be used in whole or in part for any other project without written authority of Wallace Group, a California Corporation. Copyright © 2025 Wallace Group, a California Corporation. All rights reserved. Copies of this drawing shall have this notice. 321 4 5 321 4 5 C D B A ORIGINAL SCALE IS IN INCHES FOR REDUCED PLANS 0 1 2 3 SHEETS FILE NAME: PHASE 4 BERM.DWG Plot Date: 7/28/2025 AV I L A R A N C H CI T Y o f S A N L U I S O B I S P O PH A S E 4 B E R M - A D J A C E N T P A R C E L O V E R F L O W 1493.0007 RAH RMS 07/28/25 1 1 RAC H E L A . H AWTH O R N E C I V I L No. 73686REGISTERED P R O F E SSIONAL EN G I N E E R NOT FOR CONSTRUCTION FOR PLAN REVIEW ONLY S T A TE OF C A L I F O R NIA 0 30'60' (IN FEET) 15' GRAPHIC SCALE 1 IN = 30 FT N u uuuuu u uuuuu u u u u u uu 100 y O v e r f l o w P a t h Ta n k F a r m C r e e k Je s p e r s e n R o a d Venture Drive TEMPORARY CONSTRUCTION EASEMENT MULTI-FAMILY GRADING PLAN BY OTHERS MULTI-FAMILY GRADING PLAN BY OTHERS FF 123.50 Tr a c t Bo u n d a r y PL A- Section SCALE: 1"= 30'A Bi k e P a t h C r o s s S e c t i o n Jespersen Road Cross Section Project Avila Ranch Sub-Task Chevron Berm/Spillway Overflow Calculation Earthen Berm RSP Protection Direction Caltrans HDM Chapter 880 - Shore Protection https://dot.ca.gov/-/media/dot-media/programs/design/documents/chp0880-a11y.pdf Variable Unit Value Note γr lb/ft3 156.0 γw lb/ft3 62.4 Water Unit Weight Sr N/A 2.5 Standard Value Sw N/A 1.0 Fresh Water H ft 2.37 Run Up Depth + Max Depth in Channel θ degrees 7.13 Calculated from CAD Design Kd N/A 2.2 W50 lb 35.0 d50 ft 0.64 d50 in 7.7 Use Class III RSP per Caltrans and FHWA sizing sheets (12in, 150lb) Thickness in 18 *Rounded up to next larger size Avila Ranch Ph04 Earthen Berm RSP Calculations Page 1 of 5 Prepared by Wallace Group July 2025 Avila Ranch Ph04 Earthen Berm RSP Calculations Page 2 of 5 Prepared by Wallace Group July 2025 Avila Ranch Ph04 Earthen Berm RSP Calculations Page 3 of 5 Prepared by Wallace Group July 2025 Avila Ranch Ph04 Earthen Berm RSP Calculations Page 4 of 5 Prepared by Wallace Group July 2025 Elev Bottom ft 120.0 Elev Top ft 122.0 Vertical Change ft 2.0 Horizontal Dist.ft 16.0 θ rad 0.12 θ degrees 7.13 Slope Angle Calculations Avila Ranch Ph04 Earthen Berm RSP Calculations Page 5 of 5 Prepared by Wallace Group July 2025 Avila Ranch Chevron Berm Overflow RSP Sizing RSP Sizing Per Design Guideline 5, Riprap Design for Embankment Overtopping Publication No. FHWA-NHI-09-112, Bridge Scour and Stream Instability Countermeasures Variable Units Desciption Notes g 32.2 ft/s2 Acceleration due to gravity Ku 0.525 unitless constant, for English units qf 5.3 ft3/s/ft unit discharge at failure Calculated in step 2 below Cu max 1.92 unitless coefficient of uniformity (d60/d10) Calcuated in step 1 below Cu min 1.21 unitless coefficient of uniformity (d60/d10) Calcuated in step 1 below S 0.277 ft/ft slope of embankment Calculated from CAD, average of 3 lines α 15.5 degrees slope of the embankment Sg 2.5 unitless specific gravity of stone Assumed ϕ 34 degrees angle of repose of the riprap User input Constant or calculated value 1. Calculate approximate Cu per Caltrans gradations. Caltrans provides d15 and d50. Class d15 min (inches) d50 min (inches)Cu d15 max (inches) d50 max (inches)Cu d15 min (inches) d50 max (inches)Cu I 3.7 5.2 1.41 5.7 6.9 1.21 3.7 6.9 1.86 II 5.5 7.8 1.42 5.8 10.5 1.81 5.5 10.5 1.91 III 7.3 11.5 1.58 10.5 14 1.33 7.3 14 1.92 IV 9.2 14.5 1.58 13 17.5 1.35 9.2 17.5 1.90 V 11 17 1.55 15.5 20.5 1.32 11 20.5 1.86 2. Calculate qf, unit discharge at failure Discharge over the low water crossing notes L 20 feet From HEC-RAS Q 105.0 cfs From HEC-RAS qf 5.3 cfs/foot 3. Calculate smallest median rock size, d50 Cu max d50 = 8.6 in Cu min d50 = 6.8 in Use Class III, 12 inches Per Caltrans max RSP slope of 1.5:1. Smaller angle is conservative. Avila Ranch Ph04 Earthen Berm RSP Calculations Page 1 of 2 Prepared by Wallace Group July 2025 FWHA Avila Ranch Chevron Berm Overflow RSP Sizing RSP Sizing Per Design Guideline 5, Riprap Design for Embankment Overtopping Publication No. FHWA-NHI-09-112, Bridge Scour and Stream Instability Countermeasures Avila Ranch Ph04 Earthen Berm RSP Calculations Page 2 of 2 Prepared by Wallace Group July 2025 FWHA Project Avila Ranch Sub-Task Chevron Berm/Spillway Overflow Calculation Earthen Berm RSP Protection Direction Caltrans HDM CHP 870, 2022 Data Description At Earthen Berm Notes y Local Depth (ft)1.37 100-year max depth from HEC- RAS Sf Safety Factor 1.10 Use CT standard value Cs Stability Coefficiant 0.3 Cv Velocity Distribution Coefficiant 1.42 Outside of bend Ct Blanket Thickness Coefficient 1.0 Sg Specific Gravity of Stone 2.50 Assumed g Acceleration due to Gravity (ft/s2)32.2 Vavg Average velocity (fps)3.70 100-year average velocity across channel from HEC-RAS Rc Centerline radius of curvature (ft)5.0 *Assumed to set Vdes to Vmax W Width of water surface (ft)25.0 based on high velocity area across from overflow (from HEC- Vdes Characteristic Velocity for Design (fps)8.34 Looks reasonable based on HEC- RAS K1 Side Slope Correction Factor 1.00 See K1 Tab - used 4:1 slope Results ft in d30 0.7 8.2 d50 0.8 9.9 RSP Use Class III Class II Avila Ranch Ph04 Earthen Berm RSP Calculations Page 1 of 2 Prepared by Wallace Group July 2025Caltrans Avila Ranch Ph04 Earthen Berm RSP Calculations Page 2 of 2 Prepared by Wallace Group July 2025Caltrans Project Avila Ranch Sub-Task Chevron Berm/Spillway Overflow Calculation Side Slope Correction Factor Direction Caltrans HDM CHP 870, 2022 angle (deg)angle (rad) 14 0.24 32 0.56 Slope Angle (rad)Angle (deg)K1 4 0.245 14.0 1.00 3 0.322 18.4 0.98 2.5 0.381 21.8 0.94 2 0.464 26.6 0.87 1.5 0.588 33.7 0.72 Note: 2:1 Results match Caltrans Worked Example, HDM Chp 870 Avila Ranch Ph04 Earthen Berm Caltrans K1 Calculations Page 1 of 1 Prepared by Wallace Group July 2025Caltrans Project Avila Ranch Sub-Task Chevron Berm/Spillway Overflow Calculation Run-Up Freeboard on Earthen Berm Direction Velocity Head = V2/2g (ft) V = Velocity (ft/sec) g = gravity (32.2 ft/s2) Variable Unit Value Note V ft/s 5.27 Maximum 100-yr Velocity Adjacent to CMU Wall g ft/s2 32.2 HV ft 0.43 Velocity Head Safety Factor 2 Min Freeboard ft 1 Max WSE ft 119.6 Maximum 100-yr Depth Adjacent to CMU Wall Pad Elev ft 122 Frm Design Freeboard ft 2.4 Maximum 10-yr Velocities From Model Maximum run up is equal to the velocity head (occurs when flows are perpendicular to an obstruction) Avila Ranch Ph04 Earthen Berm Run-Up Calculations Page 1 of 1 Prepared by Wallace Group July 2025 Avila Ranch – WG Project No. 1493-0007 Date: July 15, 2025 MODEL RESULTS Note that results upstream of Table 1 Peak Flows at Model Result Cross Sections (cfs) Storm Event Berm Overflow1 Bike Path Jespersen Road 10-year No Culvert 37 37 36 10-year 5 HDPE Pipe Culvert 37 37 0 25-year No Culvert 67 67 63 25-year 5 HDPE Pipe Culvert 67 67 18 100-year No Culvert 105 105 94 100-year 5 HDPE Pipe Culvert 105 105 53 1From Trihydro Chevron Property Model Table 2 Maximum Flow Depths at Model Result Cross Sections (feet) Storm Event Berm Overflow1 Bike Path Jespersen Road 10-year No Culvert 0.4 0.8 1.1 10-year 5 HDPE Pipe Culvert 0.4 0.8 0 25-year No Culvert 0.6 1.1 1.2 25-year 5 HDPE Pipe Culvert 0.6 1.1 1.0 100-year No Culvert 0.7 1.4 1.3 100-year 5 HDPE Pipe Culvert 0.7 1.4 1.2 1From Trihydro Chevron Property Model, Stage minus Lowest Weir Elevation MODEL RESULTS Below is a summary of the HEC-RAS 2 Model Results for the peak flows, maximum flow depths, maximum water surface elevations, and maximum velocities at each of the cross sections. April 2025 Page 2 of 3 Table 3 Maximum Flow Water Surface Elevation at Model Result Cross Sections (feet) Storm Event Berm Overflow1 Bike Path Jespersen Road 10-year No Culvert 120.0 119.8 118.4 10-year 5 HDPE Pipe Culvert 120.0 119.8 N/A 25-year No Culvert 120.3 120.0 118.5 25-year 5 HDPE Pipe Culvert 120.3 120.0 118.3 100-year No Culvert 120.6 120.3 118.6 100-year 5 HDPE Pipe Culvert 120.6 120.3 118.5 1From Trihydro Chevron Property Model, Stage minus Lowest Weir Elevation Cross Sections For WSE Jespersen Road Bi k e P a t h Be r m O v e r f l o w April 2025 Page 3 of 3 Table 4 Maximum Flow Velocities (fps) Storm Event Berm Overflow1 Bike Path Jespersen Road 10-year No Culvert 4.9 4.3 5.3 10-year 5 HDPE Pipe Culvert 4.9 4.3 0 25-year No Culvert 5.0 6.9 6.8 25-year 5 HDPE Pipe Culvert 5.0 6.9 1.7 100-year No Culvert 5.3 7.9 9.8 100-year 5 HDPE Pipe Culvert 5.3 7.9 5.3 1Highest velocity at overflow from Jespersen Road to Tank Farm Creek Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft EXHIBIT NOTES: WALLACE GROUP DID NOT PERFORM SURVEY SERVICES FOR THIS MAP. NOT A LEGAL DOCUMENT. AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION FLOOD INUNDATION COMPARISON 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 07-30-2025 LEGEND Property Boundary 100-yr Flood - EG 100-yr Flood - FG Berm 100-yr Flood - FG No Berm CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,200 Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 06-24-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 10-yr Max Depth No Drainage Improvements Feet 0 5 FG-POST-PH04 (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 06-24-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 25-yr Max Depth No Drainage Improvements Feet 0 5 FG-POST-PH04 (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 06-24-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 100-yr Max Depth No Drainage Improvements Feet 0 5 FG-POST-PH04 (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 07-21-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 10-yr Max Depth 5-Barrel 18" HDPE Culvert Feet 0 5 FG-POST-PH04 with Culvert (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 RESULTS ONLY VALID DOWNSTREAM OF CULVERTS Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 07-21-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 25-yr Max Depth 5-Barrel 18" HDPE Culvert Feet 0 5 FG-POST-PH04 with Culvert (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 RESULTS ONLY VALID DOWNSTREAM OF CULVERTS Esri Community Maps Contributors, County Of San Luis Obispo, California State Parks, © OpenStreetMap, Microsoft, Esri, TomTom, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, US Census Bureau, USDA, USFWS, County of San Luis Obispo, Maxar, Microsoft AVILA RANCH CHEVRON BERM OVERFLOW MITIGATION MODEL RESULTS 0 10050 O JOB NO: 1493-0007 CREATED BY: AJM DATE: 07-21-2025 LEGEND Property Boundary Parcel Lines PUE Easements ROAD ROW 100-yr Max Depth 5-Barrel 18" HDPE Culvert Feet 0 5 FG-POST-PH04 with Culvert (ft) Value 108 129 CIVIL ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PLANNING PUBLIC WORKS ADMINISTRATION SURVEYING/GIS SOLUTIONS WATER RESOURCES 612 CLARION COURT SAN LUIS OBISPO, CA 93401 T 805 544-4011 F 805 544-4294 www.wallacegroup.us 1:1,500 RESULTS ONLY VALID DOWNSTREAM OF CULVERTS AVILA RANCH - TRACT 3089 PHASES 5 NORTH JESPERSEN CULVERT ANALYSIS (CHEVRON BERM OVERFLOW PATH) 7/14/2025 Included in this document: -- North Jespersen Culvert - HY8 Culvert Report HY-8 Culvert Analysis Report Crossing Discharge Data Discharge Selection Method: Recurrence NORTH JESPERSEN ROAD CULVERT - CHEVRON BERM OVERFLOW Table 1 - Summary of Culvert Flows at Crossing: North Jespersen Road Headwater Elevation (ft) Discharge Names Total Discharge (cfs) HDPE Pipe Culvert Discharge (cfs) Roadway Discharge (cfs) Iterations 118.07 10 year 37.00 37.00 0.00 1 118.73 25 year 65.00 48.04 16.94 5 119.18 100 year 105.00 54.68 50.31 4 118.30 Overtopping 41.16 41.16 0.00 Overtopping Flow > 41.16 cfs will crest the paved bike path and flow south towards the Jespersen-Venture roundabout. A proposed 36" catch basin will capture and convey this excess flow via the proposed SD pipes beneath Jespersen. Stormwater will then be discharged into Tank Farm Creek to the east. (See Phase 5 Improvement Plans for proposed pipe routing). NOTE: Total Discharge values for the 10, 25, and 100-year storm events are taken from the Chevron property existing conditions flood model prepared by TriHydro. Rating Curve Plot for Crossing: North Jespersen Road Table 2 - Culvert Summary Table: HDPE Pipe Culvert Discharge Names Total Discharge (cfs) Culvert Discharge (cfs) Headwater Elevation (ft) Inlet Control Depth (ft) Outlet Control Depth (ft) Flow Type Normal Depth (ft) Critical Depth (ft) Outlet Depth (ft) Tailwater Depth (ft) Outlet Velocity (ft/s) 10 year 37.00 37.00 118.07 1.710 1.866 7-M2c 1.500 1.050 1.050 0.100 5.598 25 year 65.00 48.04 118.73 2.174 2.528 7-M2c 1.500 1.195 1.195 0.100 6.362 100 year 105.00 54.68 119.18 2.514 2.983 7-M2c 1.500 1.266 1.266 0.100 6.872 ******************************************************************************** Straight Culvert Inlet Elevation (invert): 116.20 ft, Outlet Elevation (invert): 116.01 ft Culvert Length: 97.50 ft, Culvert Slope: 0.0020 ******************************************************************************** Culvert Performance Curve Plot: HDPE Pipe Culvert Water Surface Profile Plot for Culvert: HDPE Pipe Culvert Site Data - HDPE Pipe Culvert Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 116.20 ft Outlet Station: 97.50 ft Outlet Elevation: 116.01 ft Number of Barrels: 5 Culvert Data Summary - HDPE Pipe Culvert Barrel Shape: Circular Barrel Diameter: 1.50 ft Barrel Material: Smooth HDPE Embedment: 0.00 in Barrel Manning's n: 0.0120 Culvert Type: Straight Inlet Configuration: Square Edge with Headwall Inlet Depression: None Flow > 41.16 cfs will crest the paved bike path and flow south towards the Jespersen-Venture roundabout. A proposed 36" catch basin will capture and convey this excess flow via the proposed SD pipes beneath Jespersen. Stormwater will then be discharged into Tank Farm Creek to the east. (See Phase 5 Improvement Plans for proposed pipe routing). Table 3 - Downstream Channel Rating Curve (Crossing: North Jespersen Road) Flow (cfs)Water Surface Elev (ft)Depth (ft) 37.00 116.00 0.10 65.00 116.00 0.10 105.00 116.00 0.10 Tailwater Channel Data - North Jespersen Road Tailwater Channel Option: Enter Constant Tailwater Elevation Constant Tailwater Elevation: 116.00 ft Roadway Data for Crossing: North Jespersen Road Roadway Profile Shape: Constant Roadway Elevation Crest Length: 20.00 ft Crest Elevation: 118.30 ft Roadway Surface: Paved Roadway Top Width: 10.00 ft Avila Ranch Phases 2-6 Drainage Report Addendum #2 StormCAD Reference Exhibit Date: 7-21-2025 North Jespersen Culvert not included in this analysis. See separate calculations in Drainage Report Add. #2 Active Scenario: Phases 2-6 --- 10 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - CB 569, Future E- 10 to CB 568 (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phases 2-6 --- 10 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - CB 605 to MH 758 (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phases 2-6 --- 10 Year Storm WG Project Engineer: Rachel Hawthorne, Zac PowellAvila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - MH 811 to O-311 (Outlet E) (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phases 2-6 --- 10 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 505 to O-305 (Outlet E north) (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phases 2-6 --- 10 Year Storm 110.00 115.00 120.00 -0+50 0+00 0+50 1+00 Station (ft) PH5 - CB 598 to CB 566 CB 598 Rim: 117.98 ft Invert: 114.22 ft HGL (In): 114.80 ft HGL (Out): 114.79 ft Inlet: SLO City Curb Inlet Gutter Depth: 2.5 in Gutter Spread: 5.51 ft Headloss: 0.01 ft Total Intercepted Flow: 0.66 cfs Bypass Flow: 0.01 cfs NOTES: SLO 42 DI CB 566 Rim: 117.30 ft Invert: 114.04 ft HGL (In): 114.78 ft HGL (Out): 114.67 ft Inlet: SLO City Curb Inlet Gutter Depth: 6.7 in Gutter Spread: 4.42 ft Headloss: 0.10 ft Total Intercepted Flow: 0.66 cfs Bypass Flow: 0.00 cfs NOTES: SLO 87 DI CO-298: 18.0 in Length: 89.64 ft S: 0.21 % Up. Invert: 114.22 ft Down. Invert: 114.04 ft HGL (In): 114.79 ft HGL (Out): 114.79 ft Vel (In): 1.09 ft/s Vel (Out): 0.76 ft/s Q: 0.66 cfs WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 598 to CB 566 (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phases 2-6 --- 10 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 599 to CB 567 (Avila Ranch Drainage Model_2.stsw) Active Scenario: Phase 2-6 --- 25 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - CB 569, Future E- 10 to CB 568 (Avila Ranch Drainage Model_2.stsw) 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phase 2-6 --- 25 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - CB 605 to MH 758 (Avila Ranch Drainage Model_2.stsw) 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phase 2-6 --- 25 Year Storm WG Project Engineer: Rachel Hawthorne, Zac PowellAvila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - MH 811 to O-311 (Outlet E) (Avila Ranch Drainage Model_2.stsw) 118.30 ft 114.01 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phase 2-6 --- 25 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 505 to O-305 (Outlet E north) (Avila Ranch Drainage Model_2.stsw) 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phase 2-6 --- 25 Year Storm 110.00 115.00 120.00 -0+50 0+00 0+50 1+00 Station (ft) PH5 - CB 598 to CB 566 CB 598 Rim: 117.98 ft Invert: 114.22 ft HGL (In): 114.88 ft HGL (Out): 114.88 ft Inlet: SLO City Curb Inlet Gutter Depth: 2.6 in Gutter Spread: 6.14 ft Headloss: 0.01 ft Total Intercepted Flow: 0.79 cfs Bypass Flow: 0.04 cfs NOTES: SLO 42 DI CB 566 Rim: 117.30 ft Invert: 114.04 ft HGL (In): 114.87 ft HGL (Out): 114.75 ft Inlet: SLO City Curb Inlet Gutter Depth: 6.9 in Gutter Spread: 5.22 ft Headloss: 0.12 ft Total Intercepted Flow: 0.84 cfs Bypass Flow: 0.00 cfs NOTES: SLO 87 DI CO-298: 18.0 in Length: 89.64 ft S: 0.21 % Up. Invert: 114.22 ft Down. Invert: 114.04 ft HGL (In): 114.88 ft HGL (Out): 114.87 ft Vel (In): 1.07 ft/s Vel (Out): 0.78 ft/s Q: 0.79 cfs WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 598 to CB 566 (Avila Ranch Drainage Model_2.stsw) 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phase 2-6 --- 25 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 599 to CB 567 (Avila Ranch Drainage Model_2.stsw) 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft 118.30 ft Active Scenario: Phases 2-6 --- 100 Year Storm WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - CB 569, Future E- 10 to CB 568 (Avila Ranch Drainage Model_2.stsw) 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft Active Scenario: Phases 2-6 --- 100 Year Storm WG Project Engineer: Rachel Hawthorne, Zac PowellAvila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH4 - MH 811 to O-311 (Outlet E) (Avila Ranch Drainage Model_2.stsw) 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft 118.40 ft Active Scenario: Phases 2-6 --- 100 Year Storm 110.00 115.00 120.00 -0+50 0+00 0+50 1+00 Station (ft) PH5 - CB 598 to CB 566 CB 598 Rim: 117.98 ft Invert: 114.22 ft HGL (In): 115.05 ft HGL (Out): 115.04 ft Inlet: SLO City Curb Inlet Gutter Depth: 2.9 in Gutter Spread: 7.25 ft Headloss: 0.01 ft Total Intercepted Flow: 1.00 cfs Bypass Flow: 0.17 cfs NOTES: SLO 42 DI CB 566 Rim: 117.30 ft Invert: 114.04 ft HGL (In): 115.03 ft HGL (Out): 114.89 ft Inlet: SLO City Curb Inlet Gutter Depth: 7.3 in Gutter Spread: 6.99 ft Headloss: 0.15 ft Total Intercepted Flow: 1.30 cfs Bypass Flow: 0.00 cfs NOTES: SLO 87 DI CO-298: 18.0 in Length: 89.64 ft S: 0.21 % Up. Invert: 114.22 ft Down. Invert: 114.04 ft HGL (In): 115.04 ft HGL (Out): 115.04 ft Vel (In): 1.02 ft/s Vel (Out): 0.80 ft/s Q: 1.00 cfs WG Project Engineer: Rachel Hawthorne, Zac Powell Avila Ranch Tract 3089 - Phases 2, 3, 4, 5 & 6Plot Date: 7/21/2025 StormCAD [10.04.00.158]Wallace Group Profile Report Engineering Profile - E_PH5 - CB 598 to CB 566 (Avila Ranch Drainage Model_2.stsw)