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HomeMy WebLinkAbout2023-10-31_Avila PH2-3 Stormwater O&M_HOASTORMWATER CONTROL MEASURES OPERATION AND MAINTENANCE PLAN For TRACT 3089 - AVILA RANCH PHASES 2 & 3 Entities Responsible for Maintenance: Avila Ranch Development Homeowner’s Association (HOA) July 2023 Prepared by: 612 Clarion Court San Luis Obispo, CA 93401 805 544-4011 Job Number: 1493-0007 Date Signed: 7/28/2023 PRIVATE STORMWATER OPERATIONS AND MAINTENANCE MANUAL FILE COPY STORM-0575-2023 Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 2 of 11 Page 2 of 11 Table of Contents Introduction.................................................................................................................... 3 General Information ...................................................................................................... 4 Facilities to be Maintained ............................................................................................ 4 Underground Gravel Chambers – Motorcourt/ Alleys ............................................... 5 Concrete Perimeter Channels ................................................................................. 6 North Boundary Bypass Culvert............................................................................... 8 Site Inspection Procedures ........................................................................................ 10 Reporting Requirements ............................................................................................ 10 Revisions of Pollution Mitigation Measures ............................................................. 10 Tables Table 1. Stormwater Control Measures ........................................................................... 4 Table 2. Gravel Chamber ................................................................................................ 5 Table 3. Concrete Channels ............................................................................................ 7 Table 4. Bypass Culverts ................................................................................................. 9 Figures Figure 1. Tract 3089 – Avila Ranch Development ........................................................... 3 Figure 2. Motorcourt/Alley Gravel Chamber Typical Section ........................................... 5 Figure 3. Concrete Perimeter Channel Typical Section .................................................. 6 Figure 4. Concrete Perimeter Channel Locations ........................................................... 6 Figure 5: North Boundary Bypass Culvert Location ........................................................ 8 Appendix Avila Ranch (Phases 2-3) Stormwater Control Measures (SCM) Exhibit Maintenance & Inspection Forms Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 3 of 11 Page 3 of 11 Introduction This document is an operations and maintenance plan for the long-term inspection, maintenance, and cleaning requirements of the Stormwater Control Measures (SCMs) installed for Phases 2 & 3 of the Avila Ranch project. The project is a part of the greater Avila Ranch Phases 1-6, which includes 149 acres of proposed development including single and multi-family homes, commercial areas, parks, and agricultural open space. Below is a list of associated documents related to this report, for reference: · Avila Ranch Development – Phase 1 Drainage Report prepared by RRM, dated 9/17/2018 · Stormwater Control Plan for Avila Ranch, prepared by RMM, dated 3/22/2022. · Annual Stormwater Maintenance Plan – Avila Ranch, prepared by RRM. · Tract 3089 Avila Ranch – Phases 2, 3, 4, 5 & 6 Mass Grading – Drainage Report (Vol. 1 of 2), prepared by Wallace Group, dated April 2023. · Tract 3089 Avila Ranch – Phases 2, 3, 4, 5 & 6 Final Improvements – Drainage Report (Vol. 2 of 2), prepared by Wallace Group, dated April 2023. · Tract 3089 Avila Ranch – Phases 2, 3, 4, 5 & 6 Stormwater Control Plan, prepared by Wallace Group, dated December 21, 2022. · Tract 3089 – Public Improvement Plans – Phases 2 & 3, prepared by Wallace Group. Figure 1. Tract 3089 – Avila Ranch Development Phases 2 & 3 Phase 4, 5 & 6 Phase 1 Buckley Road Va c h e l l L a n e Venture Drive Earthwood Lane Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 4 of 11 Page 4 of 11 General Information The stormwater control measures (SCMs) proposed across Phases 2-3 of Avila Ranch have been designed to capture, treat, and retain stormwater where feasible. High groundwater levels and poor soil infiltration capabilities were identified in Phases 2 and 3, which limited greater utilization of retention and infiltration facilities. For more information on project site conditions and SCM design, refer to the Phases 2-6 Drainage Report and Stormwater Control Plan, prepared by Wallace Group. SCMs proposed for this project include the use of bioswales with underground gravel trenches, underground gravel chamber systems, a vegetated basin, vegetated swales, concrete-lined drainage channels, and bypass culverts. Routine inspection, maintenance, and repair is crucial to the long-term success and performance of these stormwater facilities. The proper operation and maintenance of these facilities is described in the following sections. Facilities to be Maintained Table 1 provides a summary of each type of stormwater control measure. Refer to the exhibits in the appendix for a map of where each SCM is located. Table 1. Stormwater Control Measures SCM ID * SCM Type Maintenance Entity · A(#1) · B(#1), B(#2), B(#3), B(#4), B(#7), B(#8), B(#11) · C(#1), C(#2) Motorcourt/ Alley Underground gravel chamber system Home Owners Association (HOA) · Perimeter channel adjacent to Lot 186 and Alley 01 · Perimeter channel adjacent to Lots 327, 307, 322 Concrete-lined perimeter channel · North Boundary Bypass Culverts Two, parallel 48” storm drain culvert systems * Referenced from Avila Ranch Phases 2-6 Stormwater Control Plan, see Stormwater Control Measure (SCM) Exhibit Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 5 of 11 Page 5 of 11 Underground Gravel Chambers – Motorcourt/ Alleys Subsurface gravel chambers will be implemented to retain the 95th percentile runoff from motorcourt/alley areas. The gravel chambers will incorporate Class III aggregate base at varying widths and depths to store runoff and promote infiltration. Runoff will enter into the underground gravel chambers through a storm drain inlet which feeds stormwater into the underground gravel chambers through a 4” perforated PVC pipe. Excess stormwater from larger rain events will overflow into the primary storm drain pipe network and continue downstream. Refer to Figure 3 for a typical detail of the proposed motorcourt/ alley gravel chambers. Figure 2. Motorcourt/Alley Gravel Chamber Typical Section The following maintenance matrix is provided for the underground gravel chamber systems. A corresponding maintenance checklist is provided in the appendix for proper record keeping of these maintenance activities. Table 2. Gravel Chamber Component Description Frequency Maintenance Activities Inlet/Outlets Storm drain box and grate with 4” PVC pipe to gravel trench. Storm drain inlet is integrated with storm drain system to convey excess flows. Semiannually, before & after storm event Lift grate cover to clean. Vacuum any sediment accumulated at the bottom of the box and remove any trash or debris. Inspect for signs of plugging and erosion, as needed. Repair any chips & cracks. Excavate and replace structure, per plan, if needed. ** Note: If the performance of an SCM is severely limited or if failure of the SCM is suspected, the underground aggregate rock storage layer may need to be investigated. If underground aggregate layer is found to be clogged or failing, it may need to be excavated, removed, and replaced. Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 6 of 11 Page 6 of 11 Concrete Perimeter Channels Two rectangular, concrete channels have been integrated into the Avila Ranch drainage design to capture and convey offsite run-on from northern adjacent properties to Tank Farm Creek. These concrete channels are located along the northern (North Boundary Run-on Swale) and western (Northwest Boundary Run-on Swale) perimeter of Phase 3 and will discharge into separate storm drain networks with outlets located south of Venture Drive within the vegetated bypass channel. Steel trash racks will be strategically placed along the flowline of the concrete channels to control debris and minimize clogging of downstream storm drains. Figure 3. Concrete Perimeter Channel Typical Section Figure 4. Concrete Perimeter Channel Locations Venture Dr Earthwood Ln Memphis Belle Piper Ct Jespersen Rd Tank Farm Creek Tank Farm Creek Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 7 of 11 Page 7 of 11 The following maintenance matrix is provided for the concrete channels. A corresponding maintenance checklist is provided in the appendix for proper record keeping of these maintenance activities. Table 3. Concrete Channels Component Description Frequency Maintenance Activities Inlet/Outlets Channels discharge into storm drain pipe networks to convey flows downstream through development. Semiannually, before & after storm event Inspect for signs of clogging. Clean debris & sediment from inlet/ outlet pipes. Channel Concrete, rectangular drainage channel along perimeter of development Semiannually, before & after storm event Inspect for signs of channel damage, clogging, and erosion. Clean out debris & sediment from channel and trash racks. Repair or replace damaged trash racks and protective fencing if needed. Contaminants Spills and contaminants, including oils, grease, illicit discharge, etc. Monthly Clean channels of contaminants, identify and mitigate pollutant source, report hazardous spills or illicit discharges. Embankment Adjacent side slopes surrounding the concrete channels. Semiannually, before & after storm event Check embankment along property lines for signs of erosion and ensure that stormwater enters the concrete channel over the northern or western side walls in a non- erosive sheet flow manner. If erosion or concentrated flow has occurred, correct grading to return to sheet flow conditions. Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 8 of 11 Page 8 of 11 North Boundary Bypass Culvert The North Boundary Bypass Culvert is a storm drain system consisting of two 48-inch HDPE pipes connecting the North Boundary Run-on Swale and Tank Farm Creek in Phase 3 of Avila Ranch. These culverts discharge stormwater into Tank Farm Creek immediately south of Venture Drive within the vegetated bypass channel. Figure 7, below, shows the location of the bypass culverts in Phases 3. For specific information on bypass culverts, refer to the following documents: · Tract 3089 Avila Ranch – Phases 2, 3, 4, 5 & 6 Mass Grading – Drainage Report (Vol. 1 of 2), prepared by Wallace Group, dated April 2023. · Tract 3089 Avila Ranch – Phases 2, 3, 4, 5 & 6 Mass Grading Plan, prepared by Wallace Group, dated May 2023. Figure 5: North Boundary Bypass Culvert Location Venture Dr Earthwood Ln Memphis Belle Piper Ct Jespersen Rd Tank Farm Creek Tank Farm Creek Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 9 of 11 Page 9 of 11 The following maintenance matrix is provided for the bypass culverts. A corresponding maintenance checklist is provided in the appendix for proper record keeping of these maintenance activities. Table 4. Bypass Culverts Component Description Frequency Maintenance Activities Inlets Perimeter channel discharges into storm drain culvert pipes to convey flows downstream through development to Tank Farm Creek. Semiannually, before & after large storm event. Inspect for signs of clogging. Clean debris & sediment from inlets and entry pipes. Manhole Structures Storm drain box structure with metal cover placed along pipe network. Semiannually, before & after large storm event. Lift cover and remove any obstructions within manhole. Vacuum any sediment accumulated at the bottom of the manhole and remove any trash or debris. Pipes HDPE storm drain pipes. Semiannually, Beginning and end of wet season, as needed Inspect for signs of poor performance and clogging. Clean out debris & sediment from pipes. Contaminants Spills and contaminants, including oils, grease, illicit discharge, etc. Monthly Inspect upstream channel and areas surrounding manholes. Clean areas of contaminants, identify and mitigate pollutant source, report hazardous spills or illicit discharges. Outlets Storm drain outlets delivering concentrated flows to Tank Farm Creek. Semiannually, before & after large storm event. Inspect for signs of plugging and erosion. Clean debris & sediment from outlet pipes. Rock slope protection (RSP) RSP pads prevent erosion to the soil at the point where water enters the creek and help to distribute concentrated flows safely. Semiannually, before & after large storm event. Clear obstructing debris & sediment, replace missing or eroded rock slope protection Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 10 of 11 Page 10 of 11 Site Inspection Procedures All site inspections should follow each inspection item outlined in the matrix tables and inspection templates. Additional comments and photos should also be included on the checklist form as needed. Records regarding inspections and maintenance activities as outlined in this plan are to be retained by the owner for a minimum of at least five years, and copies shall be made available upon request to the City of San Luis Obispo or Regional Water Quality Control Board. These records may include copies of completed inspection reports and maintenance checklists to document any inspection and maintenance activities that were conducted over the preceding five years. Corrective actions, repairs, or replacements should also be documented and maintained with SCM inspection and maintenance records for a minimum of five years. The maintenance checklists to be used during inspections can be found in the appendix. Reporting Requirements All required annual inspections, maintenance activities, forms and corresponding documentation must be submitted to the City of San Luis Obispo no later than June 15th of each year. Revisions of Pollution Mitigation Measures If future correction or modification of stormwater control measures or procedures is required, the Owner shall obtain approval from the governing stormwater agency prior to commencing any work. Corrective measures or modifications shall not cause discharges to bypass or otherwise impede existing stormwater control measures. Operations and Maintenance Plan for Tract 3089 Avila Ranch (Ph 2-3) - HOA July 2023 Page 11 of 11 Page 11 of 11 Appendix Avila Ranch (Phases 2-3) Stormwater Control Measures (SCM) Exhibit Maintenance & Inspection Forms: · Underground Gravel Chamber · Concrete Perimeter Channel · North Boundary Bypass Culverts > > c c c c c c c c c c c c c c c c ccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c SD SD SD SD SS SS SD SD SDSD SD SD SS SS SD SS SD SD SD SD SD SD SD SD SD SS SD SD SS SS SS SD SD SD SD SS SS SS S D SD SS SS SD SD SDSD SD SD SD SD SD SD SD SD SD SDSD SD SD SSSS SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SS SD SD SD SD SD SDSD SD SD SD SD SD SD SD COMM #1 H (#3) H (#4) H (#5) H (#9) H (#8) H (#10)H (#11) H (#12) H (#13)H (#14)H (#15) H (#16) H (#17) H (#19) H (#18) E-PH4b (#6) E-PH4b (#5) E-PH4a (#1) E-PH4a (#2) E-PH4a (#3) E-PH4a (#4) E (#2) E (#1) E (#4) E (#3) A (#1) B (#1) B (#2) B (#3)B (#4) B (#5) B (#6) B (#7) B (#8) B (#9) B (#10) C (#1) C (#2) C (#3)C (#4) C (#5) D (#1)D (#2) D (#3) D (#4) D (#5)D (#6) D (#7) D (#8) G (#1) G (#2) G (#3) G (#4) B (#11) COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK DMA E-PH4a & E-PH4b STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK H (#20) COMM #2 5-89 5-80 5-67 5-88 5-81 5-66 5-655-825-87 5-86 5-83 5-64 5-635-845-85 5-62 5-61 5-60 5-59 5-58 5-57 5-56 5-98 5-99 5-100 5-101 232 231 228 227 226229230233 205 206 209 208 207 212 211 210 215 214 213 218 217 216 221 220 219 222 223 225 224 234 239 238235 240 241 242237236 243 244 246 245 248 247 249 250 251 254 253 252 257 256 255 260 259 258 261 262 263 266 265 264 267 268 269 270 271 272 273 276 275 274 277 278 279 282 281 280 283 284 285 287 286 288 289 290 291 292 293 297 296 295 294 307 306 305 304 308 309 310 311 321 320 319 318 322 323 324 325 298 299 300 301 302 303 314 313 312 315 316 317 193 200 330 326 327 186 187 329 202 203 204 328 60 120 1 IN = 60 FT 3000 VENTURE DRIVE EA R T H W O O D L A N E JE S P E R S E N R O A D PAGE 1 OF 4 BASIN B BOT. ELEV ≈ 113.50 GW ELEV = 105.00 Avila Ranch - Phases 2-6 Stormwater Control Measures (SCM) Exhibit WRIGHT BROTHERS BASIN H-1 POND = 0.6' + 1.0' FB BOT. ELEV = 112.00 GW ELEV = 105.00 BASIN H-2 POND = 0.6' + 1.0' FB BOT. ELEV = 110.00 GW ELEV = 105.00 DRAWN BY: RAH/ ZKP 5-16-2022 1493-0007 PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). LEGEND: PHASE BOUNDARY DRAINAGE MANAGEMENT AREA BOUNDARY BIOSWALE WITH UNDERGROUND GRAVEL TRENCH MOTORCOURT/ ALLEY GRAVEL CHAMBER OFFSET GRAVEL CHAMBER VEGETATED RETENTION BASIN RETENTION-BASED TREATMENT AREA (REFER TO APPENDIX F, ATTACHMENT E COMPLIANCE) PERMEABLE PAVERS WITH GRAVEL CHAMBER PROPOSED STORM DRAIN NETWORK SCM IDENTIFICATION (REFER TO PHASES 2-6 SCM SIZING CALCULATIONS). PHASE 5 LOT NUMBERS PHASE 2, 3, 4, 6 LOT NUMBERS SD A (#1) 0-00 199 MULTI-FAMILY LOTS NOT INCLUDED MULTI-FAMILY LOTS NOT INCLUDED MULTI-FAMILY LOTS NOT INCLUDED RAC H E L A . H AWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 12/21/20225/19/2023 NORTH BOUNDARY BYPASS CULVERTS Yes No REQUIRED ACTION ACTION TAKEN If no, lift grate cover to clean. Vacuum any sediment accumulated at the bottom of the box and remove any trash or debris. Inspect for signs of plugging and erosion, as needed. Repair any chips & cracks. Excavate and replace structure, per plan, if needed. SCM LOCATION: MAINTENANCE RECORD AVILA RANCH - SAN LUIS OBISPO - CA MOTORCOURT/ ALLEY UNDERGROUND GRAVEL CHAMBER SCM NUMBER: RAINFALL IN LAST 24 HOURS (inches): WEATHER CONDITIONS: DATE AND TIME OF INSPECTION: SITE PHOTOS ATTACHED NAME OF INSPECTOR: MAINTENANCE ITEMS 1) Inspect the inlet structures for signs of plugging or accumulated debris. Is the structure in adequate condition and is able to carry out its function? ** Note: If the performance of an SCM is severely limited or if failure of the SCM is suspected, the underground aggregate rock storage layer may need to be investigated. If underground aggregate layer is found to be clogged or failing, it may need to be excavated, removed, and replaced. Yes No REQUIRED ACTION ACTION TAKEN If no, lift grate cover and remove any obstructions within the structure. Vacuum/clean any sediment accumulated and remove any trash or debris. If yes, review landscape maintenance operations operations – grass clippings, mulch, dead vegetation. Repair areas of erosion, sweep/vacuum accumulated sediment, prevent/clean contamination from landscape maintenance- grass clippings, leaves, etc. If yes, clean debris and sediment from trash racks. Repair or replace damaged trash rack, if needed. If yes, clean debris or trash from fencing. Repair or replace damaged fencing, if needed. If yes, clean channel of contaminants, identify and mitigate pollutant source, report any hazardous spills or illicit discharges. SCM LOCATION: MAINTENANCE RECORD AVILA RANCH - SAN LUIS OBISPO - CA Concrete Channel SCM NUMBER: RAINFALL IN LAST 24 HOURS (inches): WEATHER CONDITIONS: DATE AND TIME OF INSPECTION: 5) Inspect the channel for contaminants. Are there any contaminant spills such as oils, grease, illicit discharges, etc.? SITE PHOTOS ATTACHED 3) Inspect metal trash racks. Is there evidence of damage, debris, or clogging? NAME OF INSPECTOR: MAINTENANCE ITEMS 1) Inspect the inlet/ outlet structures for signs of plugging or accumulated debris. Is the structure in adequate condition and is able to carry out it's deisgned function? 2) Inspect concrete channel conditions. Is there evidence of channel damage, clogging, or surrounding erosion in tributary areas? 4) Inspect protective fencing. Is there evidence of damage or debris? Yes No REQUIRED ACTION ACTION TAKEN If no, clean debris and sediment from inlets and entry pipes. If no, lift cover and remove any obstructions within the structure. Vacuum/clean any sediment accumulated at bottom and remove any trash or debris. If yes, clean debris and sediment from pipes. If no, clean debris and sediment from outlet structures. If yes, clear obstructing debris & sediment, replace missing or eroded rip rap/ RSP. If erosion is prestn arounf outlets, rehabilitate slopes as needed. If yes, clean channel of contaminants, identify and mitigate pollutant source, report any hazardous spills or illicit discharges. DATE AND TIME OF INSPECTION: ** Note: Bypass Channel is located within environmental permitting agency jurisdiction and additional permits may be required for maintenance operations. MAINTENANCE RECORD AVILA RANCH - SAN LUIS OBISPO - CA Bypass Culverts SCM NUMBER: RAINFALL IN LAST 24 HOURS (inches): WEATHER CONDITIONS: 5) Inspect the splash pads and rock slope protection at culvert outlets. Is there any indication the rip rap/ RSP has been displaced or any other signs of erosion? 6) Inspect the channel for contaminants. Are there any contaminant spills such as oils, grease, illicit discharges, etc.? SCM LOCATION: SITE PHOTOS ATTACHED 3) Inspect storm drain pipes for clogging. Is there evidence of poor performance or clogging? NAME OF INSPECTOR: MAINTENANCE ITEMS 1) Inspect the inlets for signs of plugging or clogging. Is the structure in adequate condition and able to carry out it's deisgned function? 2) Inspect manhole structures. Is there evidence of clogging, accumulated sediment or damage? Is the structure in adequate condition and able to carry out it's deisgned function? 4) Inspect the outlet structures for signs of damage or clogging. Is the structure in adequate condition and able to carry out it's deisgned function?