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HomeMy WebLinkAbout2023-02-20_Zero Year Stormwater Inpection Memo MEMORANDUM Date: 02-20-2023 To: Hal Hannula Supervising Civil Engineer Organization: City of San Luis Obispo From: Robert Camacho Title: Principal Civil Engineer Project Name: Avila Ranch Project Number: 0661-02-LP17 Topic: EOR Certification of Stormwater BMP 0-year Stormwater Inspection The purpose of this memo is to provide the City of San Luis Obispo my engineer’s statement regarding my assessment of the overall stormwater system, since installation, for the project referred to as Avila Ranch. Based on my knowledge of the project and my initial stormwater facility inspection, the existing BMPs, as defined in the Annual Storm Water Maintenance Plan, was constructed per the approved project plans and specifications. The facilities are established and working as intended. These improvements include roadside bio-swales, motor court retention, detention pond and basins that are designed with Bioretention Soil Mix with is designed to the State PCR requirements. Attached to this Memo are site photos of the installed BMP facilities as well as the Annual Storm Water Maintenance Plan. Sincerely, Robert Camacho Principal Avila Ranch SWCP Exhibit Avila Ranch Operations and Maintenance Manual Annual Storm Water Maintenance Plan Avila Ranch San Luis Obispo, CA. Prepared by: RRM Design Group 3765 S Higuera San Luis Obispo, Ca. 93401 Outline This annual storm water maintenance plan has been developed to be in compliance with the City of San Luis Obispo requirements. This plan outlines the permanent facilities and site features that have been included as part of the overall stormwater treatment and conveyance system as designed, for the Avila Ranch subdivision in San Luis Obispo, CA. The design incorporates the necessary improvements to adequately convey, treat and detain storm water during any rain event. The system will require ongoing inspection and maintenance to maintain its effectiveness, as designed. It will be the owner’s responsibility to provide this inspection and maintenance on and as needed, but no less than once per year. Any deficiencies or damages discovered shall be repaired or mitigated in a timely manner. The Annual Storm Water Maintenance Plan includes the following: Training Requirements Exhibit 1 — Detention Pond Maintenance Exhibit 2 — Infiltration Basin Maintenance Exhibit 3 — Permeable Paver Maintenance Training Requirements: The home owner will be responsible for operation and maintenance of the biofiltration planters on their property. The CDF/HOA is to maintain the pervious pavers and all other SCM’s. Both shall be properly trained in storm water pollution prevention and facility maintenance. The responsible parties shall be responsible for ensuring that all contractors and/or personnel hired to perform actual maintenance are qualified and trained to perform the scope of maintenance they are going to perform. Bioretention Soil Mix should be 35% mature compose and 65% sand. When required to replace soil media, contact Central Coast Landscape Products at (805) 595-3478 or contact another provider of BSM materials. Reporting Requirements: The home owner will send qualified reports to the CDF/HOA for their own private SCM’s. Forms can be found in exhibit two of this manual. The CDF/HOA is to complete inspections of all other SCM’s and turn in all reports to the City of San Luis Obispo. These individuals shall be trained in the following: · Good housekeeping procedures defined in the plans and per CASQA requirements. · Proper maintenance of all pollution mitigation devices. · Identifications and cleanup procedures for spills and overflows. · Large-scale spill and hazardous material response. · Safety concerns when maintaining devices and cleaning spills. · Inspection requirements of all pollution mitigation devices covered in this plan. · Hazardous Material response and notification procedures. · If water sampling becomes necessary, the individuals collecting samples shall have adequate training sampling procedures. Pierce County Stormwater Maintenance Manual Page 15 Detention Ponds 3.1 Detention Pond tormwater detention ponds ar e open basins built by excavating below existing ground or by constructing above -ground berms (embankments). The detention pond temporarily stores stormwater runoff during rain events and slowly releases it through a n outlet (control structure ). Detentio n ponds are typically designed to completely drain within 24 hours after the completion of a storm event. Components that are typically associated with a detention pond include the following: control structure/flow restrictor, debris barrier (e.g. trash r ack), energy dissip aters, access road, and fence. Pierce County Stormwater Maintenance Manual Page 16 Detention Ponds Checklist 3.1 Detention Pond Checklist Date Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist MONTHLY , STORM General Trash & Debris Any trash and de bris which exceed 5 cubic feet per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. If less than threshold all trash and debr is will be removed as part of next scheduled maintenance. Trash and debris cleared from site. ANNUAL General Poisonous Vegetation and noxious weeds Any poisonous or nuisance vegetation which may constitute a hazard to maintenance personnel or the pub lic. Any evidence of noxious weeds as defined by State or local regulations. (Apply requirements of adopted IPM policies for the use of herbicides). No danger of poisonous vegetation where maintenance personnel or the public might normally be. (Coordinate with local health department) Complete eradication of noxious weeds may not be possible. Compliance with State or local eradication policies required MONTHLY , STORM General Contaminants and Pollution Any evidence of oil, gasoline, contaminants or o ther pollutants No contaminants or pollutants present. (Coordinate removal/cleanup with local water quality response agency). MONTHLY General Rodent Holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water p iping through dam or berm via rodent holes. Rodents destroyed and dam or berm repaired. (Coordinate with local health department; coordinate with Ecology Dam Safety Office if pond exceeds 10 acre -feet.) MONTHLY General Beaver Dams Dam results in chan ge or function of the facility. Facility is returned to design function. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) ANNUAL General Insects When insects such as wasps and hornets interfere with maintenanc e activities. Insects destroyed or removed from site. Apply insecticides in compliance with adopted IPM policies. ANNUAL General Tree Growth and Hazard Trees Tree growth does not allow maintenance access or interferes with maintenance activity (i .e., slope mowing, silt removal, vacto ring, or equipment movements). If trees are not interfering with access or maintenance, do not remove . Trees do not hinder maintenance activities. Harvested trees should be recycled into mulch or other beneficial uses (e.g., alders for firewood). Detention Pond Checklist (Continued) Pierce County Stormwater Maintenance Manual Page 17 Detention Ponds Checklist Date Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist ANNUAL General If dead, diseased, or dying trees are identified (Use a certified Arborist to determine health of tree or removal requirements) Remove hazard Trees MONTHLY Side Slopes of Pond Erosion Eroded damage o ver 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Slopes should be stabilized using appropriate erosion control measure(s); e.g., rock reinforcement, planting of grass, compaction. MONTHLY ,STORM Side Slopes of Pond Any erosion observed on a compacted berm embankment. If erosion is occurring on compacted berms a licensed civil engineer should be consulted to resolve source of erosion. MONTHLY Storage Area Sediment Accumulated sediment that exceeds 10% (typically 6” to 12”) of the designed pond depth unless otherwise specified or affects inletting or outletting condition of the facility. Sediment cleaned out to designed pond shape and depth; pond reseeded if necessary to control erosion. MON THLY Storage Area Liner (If Applicable) Liner is visible and has more than three 1/4 -inch holes in it. Liner repaired or replaced. Liner is fully covered. ANNUAL Pond Berms (Dikes) Settlements Any part of berm which has settled 4 inches lower tha n the design elevation. If settlement is apparent, measure berm to determine amount of settlement. Settling can be an indication of more severe problems with the berm or outlet works. A licensed civil engineer should be consulted to determine the source of the settlement. Dike is built back to the design elevation. ANNUAL Pond Berms (Dikes) Piping Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. (Recommend a Goethechnical engineer be called in to in spect and evaluate condition and recommend repair of condition. Piping eliminated. Erosion potential resolved. Detention Pond Checklist (Continued) Pierce County Stormwater Maintenance Manual Page 18 Detention Ponds Checklist Date Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist ANNUAL Emergency Overflow/ Spillway Tree Growth Tree growth on emergency spillways creates blockage problems and may cause failure of the b erm due to uncontrolled overtopping. Trees should be removed. If root system is small (base less than 4 inches) the root system may be left in place. Otherwise the roots should be removed and the berm restored. A licensed civil engineer should be consul ted for proper berm/spillway restoration. ANNUAL Emergency Overflow/ Spillway Emergency Overflow/ Spillway Only one layer of rock exists above native soil in area five square feet or larger, or any exposure of native soil at the top of out flow path o f spillway. (Rip -rap on inside slopes need not be replaced.) Rocks and pad depth are restored to design standards. If you are unsure whether a problem exists, please contact a Professional Engineer. Comments: Key: (MONTHLY) Monthly from Novem ber through April. (ANNUAL) Once in late summer (preferable September) (STORM) After any major storm (use 1 -inch in 24 hours as a guideline). Pierce County Stormwater Maintenance Manual Page 19 Infiltration Facilities 3.2 Infiltration /Retention Pond t ormwater infiltration ponds are open basins built by excavating below existing ground or by c onstructing above-ground berms (embankments). Like the detention pond, the infiltration pond temporarily stores stormwater runoff during rain events, but unlike the detention pond, the infiltration pond does not discharge to a downstream co nveyance system or nearby surface water. In stead, the infiltration pond relies on the ability of the site ‟s soils to absorb the stormwater into the ground. Components that are typically associated with a retention pond include the following: energy dissi p aters, access road, and fence. Pierce County Stormwater Maintenance Manual Page 20 Infiltration Facilities Checklist 3.2 Infiltration/ Retention Pond Checklist Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist MONTHLY, STORM General Trash & Debris Any trash and debris which exceed 5 cubic feet per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size garbage can). In general, there should be no visual evidence of dumping. If less than threshold all trash and debris will be removed as part of next scheduled maintenance. Trash and debris cleared from site. ANNUAL General Poisonous Vegetation and noxious weeds Any poisonous or nuisance vegetation which may constitute a hazard to maintenance personnel or the public. Any evidence of noxious weeds as defined by State or local regulations. (Apply requirements of adopted IPM policies for the use of herbicides). No danger of poisonous vegetation where maintenance personnel or the public might normally be. (Coordinate with local health department) Complete eradication of noxious weeds may not be possible. Compliance with State or local eradication policies required MONTHLY, STORM General Contaminants and Pollution Any evidence of oil, gasoline, contaminants or other pollutants No contaminants or pollutants present. (Coordinate removal/cleanup with local water quality response agency). MONTHLY General Rodent Holes Any evidence of rodent holes if facility is acting as a dam or berm, or any evidence of water piping through dam or berm via rodent holes. Rodents destroyed and dam or berm repaired. (Coordinate with local health department; coordinate with Ecology Dam Safety Office if pond exceeds 10 acre-feet.) MONTHLY General Beaver Dams Dam results in change or function of the facility. Facility is returned to design function. (Coordinate trapping of beavers and removal of dams with appropriate permitting agencies) ANNUAL General Insects When insects such as wasps and hornets interfere with maintenance activities. Insects destroyed or removed from site. Apply insecticides in compliance with adopted IPM policies. MONTHLY Storage Area Sediment Water ponding in infiltration pond after rainfall ceases and appropriate time allowed for infiltration. (A percolation test pit or test of facility indicates facility is only working at 90% of its designed capabilities. If two inches or more sediment is present, remove). Sediment is removed and/or facility is cleaned so that infiltration system works according to design. MONTHLY Filter Bags (if applicable) Filled with Sediment and Debris Sediment and debris fill bag more than ½ full. Filter bag is replaced or system is redesigned. Infiltration/ Retention Pond Checklist (Continued) Pierce County Stormwater Maintenance Manual Page 21 Infiltration Facilities Checklist Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist MONTHLY, STORM Rock Filters Sediment and Debris By visual inspection, little or no water flows through filter during heavy rain storms. Gravel in rock filter is replaced. MONTHLY Side Slopes of Pond Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Slopes should be stabilized using appropriate erosion control measure(s); e.g., rock reinforcement, planting of grass, compaction. ANNUAL Pond Berms (Dikes) Settlements Any part of berm which has settled 4 inches lower than the design elevation. If settlement is apparent, measure berm to determine amount of settlement. Settling can be an indication of more severe problems with the berm or outlet works. A licensed civil engineer should be consulted to determine the source of the settlement. Dike is built back to the design elevation. ANNUAL Pond Berms (Dikes) Piping Discernable water flow through pond berm. Ongoing erosion with potential for erosion to continue. (Recommend a Goethechnical engineer be called in to inspect and evaluate condition and recommend repair of condition. Piping eliminated. Erosion potential resolved. ANNUAL Emergency Overflow/ Spillway Tree Growth Tree growth on emergency spillways creates blockage problems and may cause failure of the berm due to uncontrolled overtopping. Trees should be removed. If root system is small (base less than 4 inches) the root system may be left in place. Otherwise the roots should be removed and the berm restored. A licensed civil engineer should be consulted for proper berm/spillway restoration. ANNUAL Emergency Overflow/ Spillway Emergency Overflow/ Spillway Only one layer of rock exists above native soil in area five square feet or larger, or any exposure of native soil at the top of out flow path of spillway. (Rip-rap on inside slopes need not be replaced.) Rocks and pad depth are restored to design standards. MONTHLY Pre-settling Ponds and Vaults Facility or sump filled with Sediment and/or debris 6" or designed sediment traps depth of sediment. Sediment is removed. If you are unsure whether a problem exists, please contact a Professional Engineer. Comments: Key: (MONTHLY) Monthly from November through April. (ANNUAL) Once in late summer (preferable September) Infiltration/ Retention Pond Checklist (Continued) Pierce County Stormwater Maintenance Manual Page 22 Infiltration Facilities Checklist (STORM) After any major storm (use 1-inch in 24 hours as a guideline). Pierce County Stormwater Maintenance Manual Page 23Closed Detention Systems (Tanks/Vaults) Checklist 3.3 Closed Detention Systems (Tanks/Vaults) losed detention systems function similar to detention ponds with the temporary storage volume pr ovided by an underground structure to regulate the storm discharge rate from the site . The structure is typically constructed of large diameter pipe (48” diameter or greater) or a concrete box (Vault). These systems are typically utilized for sites that do not have space avail able for an above -ground system and are more commonly associated with commercial sites. Underground detention systems are a n enclosed space where ha rmful chemicals and vapors can accumulate. Therefore, the inspection and maintenan ce of these facilities should be conducted by an individual with training and certification in working in hazardous confined spaces. 3.3 Closed Detention Systems (Tanks/Vaults) Checklist Pierce County Stormwater Maintenance Manual Page 24Closed Detention Systems (Tanks/Vaults) Checklist Date Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist MONTHLY Storage Area Plugged Air Vents One-half of the cross section of a vent is blocked at any point or the vent is damaged. Vents open and functioning. MONTHLY Storage Area Debris and Sediment Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. (Example: 72- inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than 1/2 length of tank.) All sediment and debris removed from storage area. ANNUAL Storage Area Joints Between Tank/Pipe Section Any openings or voids allowing material to be transported into facility. (Will require engineering analysis to determine structural stability). All joint between tank/pipe sections are sealed. ANNUAL Storage Area Tank Pipe Bent Out of Shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. (Review required by engineer to determine structural stability). Tank/pipe repaired or replaced to design. ANNUAL Storage Area Vault Structure Includes Cracks in Wall, Bottom, Damage to Frame and/or Top Slab Cracks wider than 1/2-inch and any evidence of soil particles entering the structure through the cracks, or maintenance/inspection personnel determines that the vault is not structurally sound. Vault replaced or repaired to design specifications and is structurally sound. ANNUAL Storage Area Cracks wider than 1/2-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the walls No cracks more than 1/4-inch wide at the joint of the inlet/outlet pipe. ANNUAL Manhole Cover Not in Place Cover is missing or only partially in place. Any open manhole requires maintenance. Manhole is closed. ANNUAL Manhole Locking Mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts into frame have less than 1/2 inch of thread. Mechanism opens with proper tools. Pierce County Stormwater Maintenance Manual Page 25Closed Detention Systems (Tanks/Vaults) Checklist Date Frequency Drainage System Feature     Problem Conditions to Check For Conditions That Should Exist ANNUAL Manhole Cover Difficult to Remove One maintenance person cannot remove lid after applying normal lifting pressure. Intent is to keep cover from sealing off access to maintenance. Cover can be removed and reinstalled by one maintenance person. ANNUAL Manhole Ladder Rungs Unsafe Ladder is unsafe due to missing rungs, misalignment, not securely attached to structure wall, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. If you are unsure whether a problem exists, please contact a Professional Engineer. Comments: Key: (MONTHLY) Monthly from November through April. (ANNUAL) Once in late summer (preferable September) (STORM) After any major storm (use 1-inch in 24 hours as a guideline). BUMPBUMPUUSTA. 27+66±10.5± R7 BASIN 1DBASIN 1EWater Treatment Basin DetailN:\0601\0661-02-LP17-Avila-Ranch-Ph1-Con-Docs\Engineering\ConDocs\Hydro\O&M\Basin Exhibit.dwg, Basin Detail, Feb 03, 2023 4:40pm, jewilson FEBRUARY 2023AVILA RANCH0661-02-LP17ON-SITE TREATMENT/RETENTION AREA12"30"COBBLE ORSPLASH BLOCKWHERE STORMWATER ENTERS3" MULCHFLAT BOTTOMNO SLOPES3:1MAXGRAVELSTORAGEBIORETENTION SOIL MIX6"OVERFLOW / OUTLET STRUCTURECONNECT TOADJACENT STORMDRAIN MAINLINETYPICAL WATER TREATMENT BASINNTS 22EARTHWOOD LANETYPICAL MOTOR COURT SECTION F-FNTS30" DIA. PERORATED STORMDRAIN PIPE WRAPPED WITHGEOTEXTILE FABRIC.3/4" CRUSHED DRAIN ROCK WITHGEOTEXTILE FABRICDRY UTILITIESINCLUDING GASIN JOINT TRENCHJTPROPOSED FINISHPADPROPOSED FINISHPAD20'ACCESS EASEMENT6' MIN.4' WIDENATIVE SUBGRADE4" PVC UNLESS NOTEDOTHERWISE6" NDS SPEE-D DRAIN WITHROUND BLACK GRATE ORAPPROVED EQUALUSE ADS INSERTA TEE TOCONNECT TO 30" STORM DRAINADS ANGLEDFITTING12" MIN.WATER SERVICELATERAL TRENCH12"4.5'7.75'5' MIN.U.N.O. ±4.5'SUBGRADE @ 95%COMPACTION, UPPER 12"MIN. OR AS DIRECTED BYSOILS ENGINEERMOTOR COURT PAVING MATERIAL ANDEDGE CURBING IS A DEFERRED SUBMITTAL.INSTALL 18" STORM DRAIN(S=2.0% U.N.O)1% MIN3% MAX12% MAX1% MIN 2:1MAX2:1MAXPROPOSEDGRADE BREAKAT BACK OFSIDEWALKPROPOSEDRESIDENTIALCOMMONDRIVEWAYPROPOSED UPWARD DWY. PER CITY OFSAN LUIS OBISPO STD. 2130.ALSO SEE TYPICAL DWY. PERMEABLEPAVER SECTION ON SHEET C-3.3410' VERTICAL CURVE38.4'RAMPPROVIDE 2' BENCHMINIMUM(TYP)INSTALL NYLOPLAST DRAINBASIN WITH 36" X 36"DUCTILE IRON, TRAFFICRATED GRATECONNECT TOPUBLIC STORMDRAIN (SIZE ANDLOCATION PERPLAN)JOINT TRENCHOPEN BOTTOM BASIN WITHAN 18" SUMP AND 18" OF 1 12"DRAIN ROCK BELOW IT.CONTRACTOR SHALL WRAPMIRAFI 140 FILTER FABRICAROUND ROCK LENS.TYPICAL MOTOR COURT PROFILENTSINSTALL 4" X 30"INSERTA TEE FORLATERAL CONNECTIONINSTALL 4" X 30"INSERTA TEE FORLATERAL CONNECTIONINSTALL NYLOPLAST WEIRSTRUCTURE. INVERTSHALL BE AT TOP OFROCK OVER THE PIPEINSTALL 30" PERFORATEDSTORM DRAIN WITH 34" DRAINROCK (SEE INVERT ELEVATIONSON SHEET C-4.1 AND C-4.2.)INSTALL 30" HDPECAP (U.N.O.)N:\0601\0661-02-LP17-Avila-Ranch-Ph1-Con-Docs\Engineering\ConDocs\Hydro\O&M\Basin Exhibit.dwg, Motor Court, Feb 03, 2023 4:40pm, jewilson FEBRUARY 2023AVILA RANCH0661-02-LP17MOTOR COURT (TYP) U 6 PMI-9CURB AND GUTTER PERCITY STANDARD. CURBCUT WITH DEEPEND CURBAND 18" OPENINGEDGE OFAC PAVINGBIOSOIL MEDIA WITH2.0' MIN DEPTHSIDEWALK PERCITY STANDARD GRAVELSTORAGEWITH 3.5'MIN DEPTH12" DIAMETER SMOOTH DOWEL,INSTALLED PARALLEL TO EARTHWOODLANE, 24" LONG AT ALL EXPANSIONJOINTS OR PER MUNICIPAL STANDARDS.5" COBBLEENERGYDISSIPATERAT CURBOPENING6.0" PONDING DEPTH 12.0" RETAINING CURBTYPICAL BIOSWALE DETAILSCALE: N.T.S.6' DEEP SLURRY WALL. CONCRETE CLASS 3(3 SACK MIX). EXTEND 6" BELOW ROCKSECTION.INSTALL ATRIUM TG 6.0"ABOVE SURFACE OF BSM3' MAX12.0" WIDE SLURRY WALL12.0" WIDE SLURRY WALLNOTE:12" THICK CONCRETE BRACEWALL TO EXTEND 6" BELOWROCK SECTION. TOP OFWALL SHALL BE 4.0' TALL.6.0" TALL RETAINING CURB18" RETAINING CURB 12" DIAMETER SMOOTH DOWEL,INSTALL AT COLD JOINTBETWEEN SIDEWALK ANDRETAINING CURB. 24" LONGPER MUNICIPAL STANDARDS.N:\0601\0661-02-LP17-Avila-Ranch-Ph1-Con-Docs\Engineering\ConDocs\Hydro\O&M\Basin Exhibit.dwg, Bioswale Detail, Feb 03, 2023 4:40pm, jewilson FEBRUARY 2023AVILA RANCH0661-02-LP17ON-SITE TREATMENT/RETENTIONAREA TYP.TYPICAL BIOSWALE Avila Ranch Site Photos