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22-103898-Storm Drain report-9-6-22 www.furrengineering.com Stormwater Site Plan/Report Beehive Food Park 30640 Pacific Hwy Federal Way, WA 98003 March 1, 2022 Revised: May 23, 2022 Prepared by: Rachel Elliott, E.I.T. Reviewed by: Dean A. Furr, P.E. FES Project #21097 05/23/2022 R G G N A FU R SEF O RP I ANO EL T S GE SI N ERE DEEATDSNTAWFO . SAHI IN REENOTR46937 Pg. 1 SECTION 1: PROJECT OVERVIEW 1 Vicinity Map 2 Drainage Review Flow Chart 4 SECTION 2: CORE REQUIREMENTS SUMMARY 5 Core Requirement #1: Discharge at the Natural Location: 5 Core Requirement #2: Offsite Analysis: 5 Core Requirement #3: Flow Control 5 Core Requirement #4: Conveyance System 6 Core Requirement #5: Construction Stormwater Pollution Prevention 6 Core Requirement #6: Maintenance and Operations 7 Core Requirement #7: Financial Guarantees and Liability 7 Core Requirement #8: Water Quality Facilities 7 Core Requirement #9: Flow Control BMP’s 8 Special Requirements 9 SECTION 3: OFF-SITE ANALYSIS 10 SECTION 4: ANALYSIS AND DESIGN 15 Existing Conditions 15 Developed Conditions 16 Water Quality 19 SECTION 5: CONVEYANCE SYSTEM AND ANALYSIS 41 CONTROL STRUCTURE PROFILE PLOT PRINTOUT 51 SAND FILTER PROFILE PLOT PRINTOUT 52 SECTION 6: SPECIAL REPORTS AND STUDIES 53 SECTION 7: OTHER PERMITS 54 SECTION 8: CSWPPP ANALYSIS AND DESIGN 55 SECTION 9: BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT 56 SECTION 10: OPERATIONS AND MAINTENANCE MANUAL 57 Pg. 1 SECTION 1: PROJECT OVERVIEW The site is located at 30600-30640 Pacific Hwy S in Federal Way, WA, and consists of a total area of 33,909 SF (0.78 acre) on parcels no. 092104-9102 (0.598 acre) and 092104-9121(0.780 acre). This project proposes to replace and expand the parking lot at 30600-30640 Pacific Hwy S and create a mobile food truck parking area. Improvements will also include new sidewalks, grade adjustments in order to comply with ADA accessibility requirements, and utilities (i.e. water, sewer, and power) similar to RV/trailer camping facilities. The northern parcel (092104-9102) of the site consists of a paved parking lot for the commercial building located at 30640 Pacific Hwy S; the southern parcel (092104-9121) includes a small portion of the existing lot, and a large, nearly-level area vegetated with grasses. The site is bordered to the north, east, and south by commercial properties, and to the west, by Pacific Hwy S. The City of Federal Way has adopted the 2021 King County Surface Water Design Manual (KCSWDM) and the 2021 Addendum as its basis for stormwater design. Pg. 2 Vicinity Map Vicinity Map Scale: NTS Pg. 3 This project has an existing impervious surface coverage of 49%, and is therefore considered “Redevelopment” per the definition given in the City of Federal Way Revised Code (FWRC) 19.30.120: “[R]edevelop” or “redevelopment” means a project that proposes to add, replace, or modify impervious surface (for purposes other than a residential subdivision or maintenance) on a site that is already substantially developed in a manner consistent with its current zoning, or with a legal nonconforming use, or has an existing impervious surface coverage of 35 percent or more. See the Drainage Review flowchart at the end of Section 1. Pg. 4 Drainage Review Flow Chart Pg. 5 SECTION 2: CORE REQUIREMENTS SUMMARY Full Drainage Review is required because this project results in ≥ 2,000sf of New + Replaced impervious surface or 7,000sf of land disturbance. See the Drainage Review flowchart at the end of Section 1. Core Requirement #1: Discharge at the Natural Location: This project will maintain existing drainage flow paths, with water being channeled into the existing storm drain system. This project is not adjacent to and does not contain a landslide, steep slope, or erosion hazard area. Core Requirement #2: Offsite Analysis: See Section 3 of this report, which satisfies the requirements outlined in the 2021 KCSWDM, including a Level 1 downstream analysis, which examines the drainage system within ¼ mile downstream of the project site. Core Requirement #3: Flow Control Area-specific flow control requirements: This project falls within a Level 2 Conservation Flow Control Area and is subject to Enhanced Basic Flow control; therefore, this project must comply with the following flow control performance standards and assumptions unless modified by offsite analysis per Core Requirement #2. o Level 2 Flow Control: Match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10-year return periods. Assume historic site conditions as the predeveloped condition.  Target surfaces: 1. New impervious surface that is not fully dispersed per the criteria on Page 1-51 or not farmland dispersed as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new impervious surface shall be assumed as specified in Chapter 3. Note, any new impervious surface such as a bridge or boardwalk that spans the ordinary high water of a stream, pond, or lake may be excluded as a target surface if the runoff from such span is conveyed to the ordinary high water area in accordance with Criteria (b), (c), (d), and (e) of the "Direct Discharge Exemption" (p 1-41). 2. New pervious surface that is not fully dispersed or not farmland dispersed as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new pervious surface shall be assumed to be the entire lot area, Pg. 6 except the assumed impervious portion and any portion in which native conditions are preserved by covenant, tract, or easement. In addition, the new pervious surface on individual lots shall be assumed to be 100% grass if located within the Urban Growth Area (UGA) and 50% grass/50% pasture if located outside the UGA. 3. Existing impervious surface added since January 8, 2001 that is not fully dispersed or not farmland dispersed as specified in Appendix C, and not yet mitigated with a County-approved flow control facility or flow control BMP. Note: January 8, 2001 is the effective date of the ESA 4(d) Rule for Puget Sound Chinook salmon. 4. Replaced impervious surface that is not fully dispersed or not farmland dispersed as specified in Appendix C on a non-redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more, OR new pervious surface is ¾ acre or more. 5. Replaced impervious surface that is not fully dispersed on a transportation redevelopment project in which new impervious surface is 5,000 square feet or more and totals 50% or more of the existing impervious surface within the project limits. 6. Replaced impervious surface that is not fully dispersed or not farmland dispersed as specified in Appendix C, on a parcel redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more and whose valuation of proposed improvements (including interior improvements and excluding required mitigation improvements) exceeds 50% of the assessed value of: (a) the existing project site improvements on commercial or industrial projects, or (b) the existing site improvements on other projects. Core Requirement #4: Conveyance System See Section 5: Conveyance System Analysis. Core Requirement #5: Construction Stormwater Pollution Prevention Erosion and Sediment Control (ESC) Measures A Temporary Sediment and Control (TESC) plan will be provided. The requirements of Section 1.2.5.1 will be satisfied as follows: 1. Clearing Limits: Clearing limits are shown on the TESC plan and will be demarcated onsite by high-visibility fencing. 2. Cover Measures: Stockpiles and exposed soils will be protected using methods selected from Section C.3 as appropriate for site conditions. 3. Perimeter Protection: Silt fence will be constructed downstream of the site at the buffer edge. 4. Traffic Area Stabilization: Construction traffic will use existing driveways. 5. Sediment Retention: All downstream catch basins will be fitted with inlet protection. Pg. 7 6. Surface Water Collection: Ditches, berms, and other measures as appropriate will be installed to intercept surface water from disturbed areas, convey it to a sediment pond/trap, and discharge it downstream of any disturbed areas. 7. Dewatering Control: Dewatering is not anticipated on this project. 8. Dust Control: Dust will be controlled as needed by watering and by covering of exposed soils and stockpiles. 9. Flow Control: Surface water from disturbed areas will be routed through the project’s onsite flow control facility in order to prevent increases in the existing site conditions 2- year and 10-year runoff peaks discharging from the project site during construction. 10. Control Pollutants: Stormwater Pollution Prevention (SWPPS) measures will be implemented using BMPs from Section D.2.2 and other BMPs as applicable. 11. Protect Existing and Proposed Flow Control BMPs: Protection measures will be applied/installed in order to prevent impacts to existing flow control BMPs and areas of proposed flow control BMPs for the project. 12. Maintain BMPs: BMPs will be maintained as outlined in the KCSWDM. 13. Manage the Project: Site development activities will be coordinated and timed relative to ESC concerns. Timely inspection, maintenance, and update of protective measures will be carried out in order to effectively manage the project and ensure the success of protective ESC and SWP design and implementation. SWPSS Measures  Follow effective pollutant handling and disposal procedures  Provide cover and containment for materials, fuel, and other pollutants  Manage the project site to maximize pollutant control and minimize pollutant sources  Avoid overapplication or untimely application of chemicals and fertilizers  Prevent or treat contamination of stormwater runoff by pH modifying sources. Core Requirement #6: Maintenance and Operations Instructions are included in the Maintenance and Operations section of this report. Core Requirement #7: Financial Guarantees and Liability These will be provided for at Final Approval. Core Requirement #8: Water Quality Facilities Water Quality Review is Required, as this project is considered Redevelopment per FWRC 19.30.120 and involves the creation of greater than 5,000 square feet of impervious surfaces. Pg. 8 See Section 4: Analysis and Design, Water Quality. Core Requirement #9: Flow Control BMP’s This project is not exempt from implementing FCBMPs. A soil infiltration evaluation determined that the soils do not have the capacity to infiltrate; therefore, any BMP that utilizes infiltration will not be proposed. See the following section, which describes the soils determined in the geotechnical report and the Geotechnical and Infiltration Evaluation in the Special Reports and Studies section of this report. This project site comprises 60,021 square feet, which is greater than the 22,000 square foot threshold for Large Lots according to the KCSWDM. This project is located within the Urban Growth Area (UGA) and is therefore not considered a Large Rural Lot. Therefore, this area will be analyzed against C.1.2.9.2.2: Large Lot BMP Requirements. 1. Full Dispersion: Full dispersion has been evaluated and the area does not comply, because the impervious area percentage is much greater than 15% compared to the available forested area. 2. Full Infiltration: Not feasible due to lack of suitable soils, per Geotech report. 3. Evaluate the following if 1 and 2 are infeasible. a. Full Infiltration: Not feasible due to lack of suitable soils, per Geotech report. b. Limited Infiltration: Not feasible due to lack of suitable soils, per Geotech report. c. Bioretention: Not feasible due to lack of suitable soils, per Geotech report. d. Permeable Pavement: Permeable pavers will be used on this project; see civil plans. 4. Basic Dispersion: Not feasible because there is no available area to provide the 25’ minimum vegetated flow path. 5. Evaluate the following if 1-4 are infeasible. a. Reduced Impervious Surface Credit per Appendix C of the 2021 KCSWDM i. Restricted footprint (see Section C.2.9.2) The combined parcel area is 60,021 sf, and the proposed total impervious is 38,573 sf, which far exceeds 4,000 sf or the maximum allowed; therefore, this option is not feasible. ii. Wheel strip driveways (see Section C.2.9.3, p. C-99) Wheel Strip Driveways are unsuitable for this project due to the extent and proposed usage of this project. iii. Minimum disturbance foundation (see Section C.2.9.4, p. C-99) Pg. 9 Minimum Disturbance Foundations are not proposed, as this project does not include and structural foundations. iv. Open grid decking over pervious surface (see Section C.2.9.5, p. C-99) Open grid decking is not proposed for this project, due to the amount and proposed use of the parking surfaces included in this project. Neither of the RISC’s are applicable to this project. b. Native Growth Retention Credit: There is not available forested area to provide a 3.5 to 1 ratio to impervious surface. 6. Soil Amendment: Feasible. Soil moisture holding capacity of new surfaces will be protected in accordance with KCC 16,82.100(F) and (G). All disturbed pervious areas will be amended per KCC 16.82, using post-construction standard OPTION 3 (import topsoil mix). 7. Perforated Pipe: Perforated pipe connection is not proposed because the underlying soils are not capable of infiltration. Special Requirements The project is subject to the five Special Requirements. Special Requirement #1: Other Adopted Area-Specific Requirements This project is within a Conservation Flow Control Area Special Requirement #2: Flood Hazard Area Delineation The area is not within a Floodplain. Special Requirement #3: Flood Protection Facilities The project will not rely on the levees or flood protection facilities, nor does it propose to construct any new flood protection facilities. Special Requirement #4: Source Controls Source controls for Restaurants and food trucks will be implemented, as laid out in the 2021 KCSWDM, Section 1.3: Structural improvements: indoor sinks for mat and rack washing and mop and wastewater disposal.  A-8 Storage of Solid and Food Wastes  A-12 Cleaning of Cooking Equipment Special Requirement #5: Oil Control The project is not considered a “high-use” site. Pg. 10 SECTION 3: OFF-SITE ANALYSIS Task 1. Study Area Definition and Maps The site is flat and there is generally no stormwater run-on. The site is within the Lower Puget Sound – DM/Fed Way Drainage Basin and the Central Puget Sound Watershed. Stormwater is generally collected by catch basins on the north side of the site and drains into the municipal stormwater system. Task 2. Resource Review a. King County iMap shows that the site is within the Duwamish-Green WRIA. b. Review of the King County Streams Water Quality Monitoring Data does not show any data. c. King County iMAP was used to evaluate the site based on the following criteria: i. Stormwater Services 1. No stormwater facilities located. 2. Drainage Complaints within ¼ mi. downstream: there have been no drainage complaints since 1990. ii. Environmentally Sensitive Areas 1. The site is located within the Lower Puget Sound – DM/Fed Way drainage basin. 2. The site is not located on a Potential Landslide Hazard area. 3. The site is not located on a Potential Steep Slope. 4. The site is located within a Low basin condition. 5. The site is not located within a Shoreline Condition. 6. The site is not located within an Erosion Hazard. 7. The site is not located within a Seismic Hazard. 8. The site is not located within a Coal Mine Hazard. 9. The site does not discharge into a Stream or Wetland. 10. The parcel does not have a Sensitive area notice on title. 11. The site is not located within a Chinook distribution area. 12. The site is not located within a Wildlife network. iii. Flooding Info 1. River Gages: none listed 2. Flood photos: none shown 3. River Facilities: none listed 4. Flood Phases: none listed 5. Elevation Certificates: none listed 6. Letter of Map Amendments and Revisions: none listed 7. Firm cross sections: none shown Pg. 11 8. Firm Panel: 53033C1235G 9. Floodway: not within 10. 100-yr Floodplain: not within 11. 500-yr Floodplain: not within 12. FEMA area with reduced risk due to levee: not within iv. Landslide: Site is not within a Landslide area. v. Groundwater 1. The site is not within a Groundwater source. 2. The site is within the South King County Groundwater Management Area. 3. Susceptible to groundwater contamination Task 3. Areas Susceptible to Groundwater Contamination: Susceptibility code by geology: L Susceptibility code by groundwater: M Susceptibility code by soil type: L Depth: 0 Depth of groundwater (ft): Susceptibility category summary: 1.00 Susceptibility summary code: L 1. The site is not within a Critical Aquifer recharge area. 2. The site is not within a Sole Source Aquifer. 3. The site is not within a Wellhead protection area – one year. 4. The site is not within a Wellhead protection area – five year. 5. The site is not within a Wellhead protection area – 10 year. 6. The site is within the Lakehaven Water and Sewer District water service area. Pg. 12 Task 4. Field Inspection Field inspection was performed remotely using Google Maps and King County iMap. The existing storm system and catch basins lie on private property and are generally not accessible for inspection. Task 5. Drainage System Description and Problem Description The site consists of an existing parking lot and adjacent grassy area and is generally flat. Stormwater is generally collected by catch basins throughout the site and conveyed north into the existing municipal stormwater system. Conveyance passes through adjacent apartment complexes and eventually discharges into Steel Lake. Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of Field Inspector, Resource Reviewer, or Resident See map Type: sheet flow, swale, stream, channel, pipe, pond Size: diameter, surface area Drainage basin, vegetation, cover, depth, type of sensitive area, volume % ¼ mi = 1,320 ft Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A Site discharge into existing municipal storm system Site discharge from sand filter vault into CB Storm system in general is very shallow. A→B 12” corrugated storm pipe Conveyance north through 30620 Pacific Hwy (Asbestos Northwest) 89.7 B→C 12” corrugated storm pipe Conveyance transition from northbound to eastbound flow 0.5% 163.8 C→D 12” corrugated storm pipe Eastbound flow through View at the Lake Apartments lot 0.5% 163.8 D→E 12” corrugated storm pipe Eastbound flow through View at the Lake Apartments lot 0.5% 299.0 E Catch basin Offsite flows from View at the Lake Apartments join stream from catch basin 299.0 E→F 12” corrugated storm pipe Eastbound flow through View at the Lake Apartments lot 0.5% 534.7 F→G 12” corrugated storm pipe Eastbound flow through View at the Lake Apartments lot 0.5% 685.5 G Catch basin Offsite flows from View at the Lake Apartments join stream from catch basin 685.5 G→H 12” corrugated storm pipe Eastbound flow through View at the Lake Apartments lot 0.5% 750.0 H Catch basin Offsite flows from View at the Lake Apartments join stream from catch basin 750.0 H→I 12” corrugated storm pipe Northeast flow through View at the Lake Apartments lot 0.5% 829.6 I→J 12” corrugated storm pipe Northeast flow through View at the Lake Apartments lot 0.5% 913.5 J→K Vegetated ditch Discharge from municipal storm system 0.5% 1,015.5 K Terminus of downstream Discharge into Steel Lake 0.5% 1,015.5 K STEEL LAKE JI HGF ED C B A PACIFIC HWY S89.7 LF74.1 LF135.2 LF 235.7 LF 150.8 LF 64.5 LF 79.6 LF83.9 LF 102.0 L F N NO SCALE DOWNSTREAM MAP ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 May 23, 2022 21097 RCE Pg. 15 SECTION 4: ANALYSIS AND DESIGN Stormwater runoff from the project must comply with the 2021 King County Stormwater Management Manual and 2021 Addendum. Hydrologic modeling was performed using WWHM 2012, using hydrologic soil group C. The project is subject to “Full” Drainage Review. Additional soil analysis was performed; please see the Geotechnical Report in Section 6.0. Review of the 5.9.1 Drainage Basins and Flow Control Standards Map shows the site is within the Level 2 – Conservation to Existing Flow Control area, which states “Runoff from the developed site will be controlled and released at a rate that matches the flow duration for the existing site conditions before the development (pre-project). The flow control duration standard requires runoff from developments to be detained and released at a rate that matches the flow duration over the range of flows extending from ½ of the 2-year up to the 50-year flow. Also match developed peak discharge rates to existing (pre-project) peak discharge rates for the 2- and 10-year return periods.” Existing Conditions The site currently consists of a parking lot associated with the commercial building located at 30600 Pacific Hwy S, and the flat, grassy area adjoining it. The site is generally flat, and the vegetation consists of grass. The site soil consists of approximately 6 inches of grass and topsoil underlain by approximately 6 to 6.5 feet of loose- to medium-dense, silty-fine to medium-grained sand with gravel (fill). These materials are underlain by medium-dense, silty-fine to medium-grained sand with gravel (weathered glacial till). Significant volumes of groundwater are not anticipated to be present at this site. Infiltration is not generally considered feasible on this project due to the large quantity of fill soils, which are of similar composition to native soils and have poor infiltration rates. The site sits upon a shallow ridge, sloping gently to the north and to the south. Stormwater currently follows two regimes; in the north area of the site, an inverted crown parking lot directs stormwater into two catch basins, where flows are conveyed into the existing stormwater system. Flows at the south edge of the site sheet flow through the vegetation southward and are collected by a catch basin offsite, then are conveyed into the existing storm system. Table 1, below, shows the breakdown of on- and off-site existing conditions: Pg. 16 EXISTING CONDITIONS sf ac PARCEL AREA 60,021 1.378 092104-9102 26,054 0.598 092104-9121 33,967 0.780 ON-SITE DISTURBED AREA 46,394 1.065 OFF-SITE DISTURBED AREA 819 0.019 ON-SITE sf ac IMPERVIOUS 18,457 0.424 EXISTING PARKING 17,530 0.402 EXISTING SIDEWALK 308 0.007 WOOD PLATFORM 141 0.003 CONTAINERS 478 0.011 PERVIOUS (LS) 27,937 0.641 OFF-SITE sf ac DRIVEWAY/RAMP 461 0.011 PERVIOUS (LS) 358 0.008 Table 1: Existing Conditions. Historic (predeveloped) site conditions were modeled as 1.084 acres of Forest, flat, hydrologic soil group C. Table 2, below, shows the predeveloped flow frequencies. Flow Frequency Flow (cfs) 15m 2 Year 0.0319 5 Year 0.0501 10 Year 0.0604 25 Year 0.0713 50 Year 0.0780 100 Year 0.0838 Table 2: Existing (Historic Site Conditions) Flow Developed Conditions This project proposes to replace and expand the existing parking lot onsite, to be used as an area for food trucks. Utilities similar to those at RV/trailer campsites (water, sewer, etc.) will also be added. The site will consist mainly of pervious pavers, with a concrete trash enclosure and concrete apron at the driveway entrance from Pacific Hwy. S. Site vegetation will consist of urban landscaping. Soils, consisting largely of native till soils and similarly composed fill soils, are considered acceptable subgrade for the proposed pavement. Infiltration is not considered feasible for this project. Temporary excavations should be sloped no steeper than 1.5H:1V in loose native soils and fills, and 1H:1V in medium-dense native soils. Table 3, below, summarizes the developed condition site breakdown. Pg. 17 PROPOSED ON-SITE DEVELOPED sf ac DISTURBED AREA 46,394 1.065 IMPERVIOUS 37,455 0.860 PERVIOUS PAVERS/CURB/TRASH 32,788 0.753 CONCRETE SIDEWALK 1,611 0.037 POND/WALLS 3,056 0.070 PERVIOUS (LS) 8,939 0.205 PROP. OFF-SITE DEVELOPMENT sf ac DISTURBED AREA 819 0.019 IMPERVIOUS 461 0.011 DRIVEWAY/RAMP 461 0.011 PERVIOUS (LS) 358 0.008 Table 3: Proposed on- and off-site new development area breakdown. This project proposes the construction of a parking area which will consist mainly of permeable pavers, laid flat at an approximate elevation of 476.0 feet. Stormwater will filtrate through the gaps between pavers and into subsurface permeable ballast. The ballast will comprise three cells, connected by 12” storm pipe. From the gravel cells, stormwater will enter the vault structure in the southwest corner of the site. Stormwater will flow through the vault and into the pond, then into the storm drain manhole (SDMH) structure. See the Developed Conditions Exhibit at the end of this Section. WWHM was used to design the gravel cells, given the inputs in Table 4, below, and the following modelling assumptions:  Historic conditions were modelled as flat, forested.  Fifteen-minute timesteps were used.  Soil was modelled as hydrologic group C.  Pervious pavers were modeled as impervious surface in WWHM (PARKING, FLAT). WWHM INPUTS ac PREDEVELOPED 1.084 C, FOREST, FLAT 1.084 DEVELOPED 1.084 C, PASTURE, FLAT 0.213 SIDEWALKS, FLAT 0.037 PARKING, FLAT 0.763 POND 0.070 Table 4: WWHM Input Table The auto-vault feature was used to determine the control structure used to model the permeable ballast storage, which was next modelled in WWHM as a gravel trench. The following outlet structure data was calculated: Pg. 18 Riser Height (ft) 1.75 Riser Diameter (in) 18 Riser Type Notched Notch Type Rectangular Notch Height (ft) 0.8322 Notch Width (ft) 0.013 Orifice Diameter (in) 0.781 A void space of 0.39 was used, based upon a total corrected volume of all available storage from four gravel cells, the vault structure, and the pond. Corrected volumes are calculated based upon total volume and void space. The total corrected volume relative to the total absolute volume was used to obtain a total average void space of 0.39. See Table 5, below. Element Area (sf) Depth (ft) Volume (cf) Void Space Corrected Volume (cf) Gravel Cell #1 7,101.00 1.75 12,426.75 0.30 3,728.03 Gravel Cell #2 4,171.20 1.75 7,299.60 0.30 2,189.88 Gravel Cell #3 681.00 1.75 1,191.75 0.30 357.53 Gravel Cell #4 10,454.60 1.75 18,295.55 0.30 5,488.67 Subtotal 22,407.80 — 39,213.65 — 11,764.1 Vault Structure 480.00 1.75 840.00 1.00 840.00 Pond 2,831.32 1.75 4,954.81 1.00 4,954.81 Subtotal 3,311.32 — 5,794.81 — 5,794.81 TOTAL 25,719.12 — 45,008.46 — 17,558.91 Weighted Void Space 0.39 Table 5: Void space calculations. WWHM was used to model a 45,024 cf gravel trench with a 1.75 foot depth; see the WWHM printout at the end of this section. For modelling purposes, a bottom length of 240 feet and a bottom width of 107.2 feet were used in WWHM, in order to equal the required area of 25,719 sf. Because the facility passed, and was designed to model the proposed system of gravel cells, vault, and pond, this system satisfies the requirements of Level 2 Conservation Flow Control. Table 5, below, shows the flow rates for the unmitigated (0701) and mitigated (0801) developed condition. Flow Frequency Flow (cfs) Developed, Unmitigated (701) Developed, Mitigated (801) 2 Year 0.3358 0.0188 5Year 0.4247 0.0273 10Year 0.4852 0.0341 25 Year 0.5636 0.0440 50 Year 0.6237 0.0524 100 Year 0.6853 0.0618 Pg. 19 Table 5: Unmitigated (0701) and Mitigated (0801) developed runoff (cfs). The SDMH structure shall be fitted with two control risers to mimic the single structure designed in WWHM; see the Control Structure Detail Exhibit at the end of this section. The 6” flat riser shall have a 0.755-inch diameter orifice and will discharge into the sand filter vault (described below, in Section 4: Analysis and Design—Water Quality) with a maximum flow rate equal to the 2-year controlled discharge rate Q2-year=0.0188 cfs determined by WWHM analysis. Flows above this rate will bypass the sand filter through an 18” notched riser, with a notch height of 0.832 ft and a width of 0.013 ft. This riser shall have a height of 1.75 feet. Flows through the 18” notched riser will discharge by 12” storm pipe into a new catch basin, and flow northward. Discharge from the sand filter will join these flows at another catch basin, and the combined flows will be conveyed northwards to join the existing municipal storm system. Water Quality This project is required to provide Enhanced Basic Water Quality Treatment, which will be provided with a treatment train per KCSWDM Section 6.1.2 Enhanced Basic Option 3—Two-Facility Treatment Train. The first stage will be a hybrid vault (Cell #1) and pond (Cell #2), which will provide the required dead storage of 4,991 cf. The vault cell will have a volume of 1,920 cf, which is sufficient to provide at least 25% of the required volume. This vault cell shall have a total depth of 8 feet, with a dead storage depth of 4 feet, and shall be 32 feet long by 15 feet wide. When stormwater reaches the water quality elevation, stormwater will spill over into the pond (Cell #2). The pond is approximately 147 feet long by 20 feet wide, with 3:1 (H:V) sloped sides and a total depth of 5 feet with a dead storage depth of 2 feet. The volume of the pond will be approximately 8,232 cf, with an estimated flow length of 7 to 1. See Vault Detail at the end of this section. The second stage of the treatment train will consist of a sand filter vault, designed in accordance with KCSWDM Section 6.5.2.A. See Sand Filter Detail Exhibit at the end of this section. WWHM was used to calculate the size of the sandfilter vault, given the basin inputs in Table 4; see the Sandfilter Vault WWHM printout at the end of this section. The target infiltration rate of 91% was selected, as the sand filter vault is considered a “basic sand filter vault” as a part of a treatment train; therefore, the required infiltration rate of 91% is used to meet Basic Water Quality standards, per the KCSWDM. The hydraulic conductivity rate of 1 in/hour was used recommended by WWHM’s user guidelines for designing sand filter vaults. A riser height of 1.58 feet (19”) was used. The calculated size of the sand filter vault was approximately 200 sf; in order to meet the dimensional ratio requirements of at least 3:1 width to length, the dimensions of 25’ long by 8’ wide were used as the final proposed design. Pg. 20 Stormwater enters the vault from a 6” riser with an orifice to match the 2-year water quality flow rate at a 1” maximum depth above the sand bed. The flow is dispersed through a perforated pipe atop a gravel pad to minimize erosion of the sand bed. Stormwater filters through the 18”-depth sand medium and is collected by 4” perforated pipes, then is conveyed to an 8” header pipe. The header pipe conveys the stormwater downstream and discharges into the existing storm system. The header pipe will also be fitted with a riser in the event the flows exceed the maximum allowed. Because of the generally shallow storm system, in order to successfully convey flows into the existing storm system with an inlet i.e. of 469.86, the sand filter vault was designed with the 18” sand filter emergency riser elevation set to 1” above the sand surface. This allows the 6” inlet pipe i.e. to be set such that flow control and water quality facilities upstream will still be able to function, given that the gravel storage will be below the proposed finished grade of approximately 476.00 feet. Discharge from the wetvault and pond into the sand filter vault will be through a 54” control structure, which will act as a flow splitter with a 6” notched riser and an 18” notched riser. Flows at or above the two-year historic volume of 0.0319 cfs will bypass the sand filter vault and discharge into a new type 2 catch basin through 18” PVC pipe, and will be conveyed into the existing stormwater system. Flows below these rates will be conveyed into the sand filter vault through a 6” PVC pipe. Sand filter capacity was checked based upon the two-year flow rates using Autodesk Storm and Sanitary Analysis and was found to be sufficient; see Sand Filter Profile Plot Printout at the end of this section. Because flows at or equal to Q2-year will be entering the sand filter vault, the max Q for the control structure vault was set equal to Q2-year = 0.0188 cfs. The hydraulic grade line (HGL) at the sand filter vault was determined to be 470.29. Given the high water surface (HWS) of 472.55 feet and an elevation of 471.16 at the bottom of the sand, this system will be adequate and will not create overflow/overtopping at the catch basins. Bypass structure capacity was checked based upon 25-year flow rates using Autodesk Storm and Sanitary Analysis and was found to be sufficient; see Control Structure Profile Plot Printout at the end of this section. Because flows at or equal to Q2-year will be entering the sand filter vault, the max Q for the control structure vault was set equal to Q25-year minus Q2-year = 0.0252 cfs. Emergency Overflow: The project emergency overflow will be from the 18” bypass riser in the stormwater control structure. The maximum flow rate, Q100-year for the developed, unmitigated condition, shall be considered to determine the height of the 6” riser and ensure that peak flows will bypass it; i.e., the height of the riser must be equal to or greater than the height at which peak flows would enter it. Therefore, the height of the 6” flat riser shall be equal to 1.75 feet plus the riser height calculated using the riser overflow curve equation, found in the 2016 King County Surface Water Design Manual: Pg. 21 𝑄௪௘௜௥ = 9.739𝐷𝐻 ଷ ଶ Where 𝑄௪௘௜௥ = Flow rate, cfs 𝐷 = riser diameter, ft 𝐻 = riser height, ft To determine riser height, 𝐻= ( 𝑄௪௘௜௥ 9.739𝐷) ଶ ଷ Given 𝑄௪௘௜௥ = Q100-year = 0.6853 cfs 𝐷 = 18 inches = 1.5 ft 𝐻 = 0.132 Therefore, the height of the 6” riser shall be 1.88 feet, with an overflow elevation of 474.46. Flood Plain: Review of the King County Flood map: this property is outside of the 100-year flood Zone. ONSITE DISTURBED AREA 46,394 SF OFFSITE DISTURBED AREA 899 SF 39.5'23.8'30.4'0.3'10.2' 0.5'19.7'14.6'14.5'0.5' 190.9'48.9'10.1'0.3'40.5'23.9'23.8'19.5'23.8'40.5' ONE STORY OFFICE BUILDING RH = 491.0' FF = 476.6' CONTAINERS ROOF OVERHANG (TYP.) OVERHEAD BEAM (TYP.) SHEDSTEM WALL (TYP.) WOOD PLATFORM DS24PI16DS6 EX SSMH RIM = 478.37' INV N-S = 468.21' SDMH RIM = 478.70' SDMH RIM = 477.28' CB RIM = 477.02' INV W 12" RCP= 473.82' CB RIM = 478.51' INV W 12" RCP = 475.09' CB RIM = 475.67' INV E 6" RCP = 473.67' CB RIM = 474.82' INV W 6" RCP = 472.62' INV E 12" RCP = 472.62' CB RIM = 474.26' INV W 12" RCP = 469.86' INV S 12" RCP = 469.86' INV N 12" RCP = 469.86' CB RIM = 475.71' UNABLE TO OPEN CB RIM = 474.21' INV W 6" CPEP = 471.71' INV S 12" DI = 471.71' RIM = 474.38' INV N 36" CMP = 472.15'0.5'0.7'0.2'10.4'48.0' 48.2' 13.9'10.2'475 475475475 480 480 475475R=5730.00'PARC E L N O . 092104 - 9 1 2 1 PARCE L N O. 09210 4 - 9 1 2 0 PARCE L N O . 09210 4- 9 1 0 2 PARCE L N O . 09210 4 - 9 2 1 9 178.70'UTILITY EASEMENT AFN: 20090903001420 12" DI8" CONC8" DIN89°50'17"W 251.06' 476 MEDIAN CURB 476 475 EXISTING PARKING 17,530.4 SF WOOD PLATFORM 141.2 SF EXISTING SIDEWALK 307.5 SF CONTAINERS 478.0 SFEXISTING BUILDING ROOF AREA 7,809 SF NOT INCLUDED IN DRAINAGE ANALYSIS N BEEHIVE FOOD TRUCK PARKDEVELOPED CONDITIONSEXHIBITRCE 05/20/2022 21097 OFFSITE DISTURBED AREA ONSITE DISTURBED AREA LEGEND PROPERTY BOUNDARY EXISTING ONSITE IMPERVIOUS EXISTING OFFSITE IMPERVIOUS 8' CANOPY8' CANOPY OHEOHEOHEOHEOHEXUGE 39.5'23.8'30.4'0.3'10.2' 0.5'19.7'14.6'14.5'0.5' 190.9'48.9'10.1'0.3'40.5'23.9'23.8'19.5'23.8'40.5' ONE STORY OFFICE BUILDING RH = 491.0' FF = 476.6' CONTAINERS ROOF OVERHANG (TYP.) OVERHEAD BEAM (TYP.) SHEDSTEM WALL (TYP.)SSSSSSSSSSBUS STOP EVLT EX SSMH RIM = 478.37' INV N-S = 468.21' CB RIM = 477.02' INV W 12" RCP= 473.82'CB RIM = 475.71' UNABLE TO OPEN CB RIM = 474.21' INV W 6" CPEP = 471.71' SDMH RIM = 474.38' INV N 36" CMP = 472.15' PARC E L N O. 092104 - 9 1 2 1 PARC E L N O . 092104 - 9 1 2 0 PARCE L N O. 09210 4 - 9 1 0 2 PARCE L N O. 09210 4 - 9 2 1 9 178.70'UTILITY EASEMENT AFN: 20090903001420 12" DI8" CONC8" DI MEDIAN CURB 39.5'23.8'30.4'0.3'10.2' 0.5'19.7'14.6'14.5'0.5' 190.9'48.9'10.1'0.3'40.5'23.9'23.8'19.5'23.8'40.5' ONE STORY OFFICE BUILDING RH = 491.0' FF = 476.6' ROOF OVERHANG (TYP.) OVERHEAD BEAM (TYP.) SHEDSTEM WALL (TYP.) BUS STOP DS24PI16DS6 SDMH RIM = 478.70' SDMH RIM = 477.28' CB RIM = 477.02' INV W 12" RCP= 473.82' CB RIM = 478.51' INV W 12" RCP = 475.09' CB RIM = 474.26' INV W 12" RCP = 469.86' INV S 12" RCP = 469.86' INV N 12" RCP = 469.86' CB RIM = 475.71' UNABLE TO OPEN CB RIM = 474.21' INV W 6" CPEP = 471.71' SDMH RIM = 474.38' INV N 36" CMP = 472.15'0.5'0.7'0.7'0.2' 0.3' 0.1' 0.4' 0.2' 0.4' 0.2'10.1'48.0' 48.2'41.0'41.0'22.9' 13.9'10.2'475475480475 475PARC E L N O. 092104 - 9 1 2 1 PARC E L N O . 092104 - 9 1 2 0 PARCE L N O. 09210 4 - 9 1 0 2 PARCE L N O. 09210 4 - 9 2 1 9 178.70'UTILITY EASEMENT AFN: 20090903001420 12" DI8" CONC8" DIN89°50'17"W 251.06' MEDIAN CURB OHEOHEOHEOHEOHEXUGE 39.5'23.8'30.4'0.3'10.2' 0.5'19.7'14.6'14.5'0.5' 190.9'48.9'10.1'0.3'40.5'23.9'23.8'19.5'23.8'40.5' ONE STORY OFFICE BUILDING RH = 491.0' FF = 476.6' CONTAINERS ROOF OVERHANG (TYP.) OVERHEAD BEAM (TYP.) SHEDSTEM WALL (TYP.)SSSSSSSSSSBUS STOP EVLT EX SSMH RIM = 478.37' INV N-S = 468.21' CB RIM = 477.02' INV W 12" RCP= 473.82'CB RIM = 475.71' UNABLE TO OPEN CB RIM = 474.21' INV W 6" CPEP = 471.71' SDMH RIM = 474.38' INV N 36" CMP = 472.15' PARC E L N O. 092104 - 9 1 2 1 PARC E L N O . 092104 - 9 1 2 0 PARCE L N O. 09210 4 - 9 1 0 2 PARCE L N O. 09210 4 - 9 2 1 9 178.70'UTILITY EASEMENT AFN: 20090903001420 12" DI8" CONC8" DI MEDIAN CURB VAN 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 PPP8' CANOPY 8' CANOPY 11 12 C C C C C C C C DRIVEWAY/WALK 461 SF EXISTING BUILDING ROOF AREA 7,809 SF NOT INCLUDED IN DRAINAGE ANALYSIS PAVERS/CURBS/GARBAGE 32,788 SF WALKWAY 1,611 SF POND AND WALL 3,056 SF ON-SITE DISTURBED AREA 46,394 SF OFF-SITE DISTURBED AREA 819 SF N BEEHIVE FOOD TRUCK PARKDEVELOPED CONDITIONSEXHIBITRCE 05/20/2022 21097 OFFSITE DISTURBED AREA ONSITE DISTURBED AREA LEGEND PROPERTY BOUNDARY DEVELOPED ONSITE IMPERVIOUS DEVELOPED OFFSITE IMPERVIOUS POND SURFACE CONTROL STRUCTURE SAND FILTER VAULT PERMEABLE BALLAST (TYP) 2.00' LIVE STORAGE 4.00' CELL#1 DEAD STORAGE 2.00' CELL#2 DEAD STORAGE 1.00' FREEBOARD 2.00' DEAD STORAGE 2.00' LIVE STORAGE 5.00' WQS=472.57 HWS=474.57 PARKING SURFACE 476.00 2.5FT OF PERMEABLE BALLAST AGGREGATE RESERVOIR BASE, EXISTING SUBGRADE 12" COMPACTED PROOF ROLLED TO ACHIEVE 95% DENISTY PER ASTM D-1557 PL VAULT CELL #1 POND CELL #2 2.00' LIVE STORAGE 1.00' SEDIMENT STORAGE 8" OF 1-1/4" MINUS CLEAN AGGREGATE PARKING SURFACE 476.00 15.00' 32.02' 5.00' WEIR OPENING 2.5' WEIR OPENING 19.15' 146.99' 7.00' RIP-RAP PAD SOUTH PROPERTY LINE VAULT CELL #1 POND CELL #2 PARKING SURFACE PAVERS SEE DETAIL ABOVE18" PVC 1.00' SEDIMENT STORAGE ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 May 23, 2022 21097 RCE VAULT DETAIL NO SCALE CB-1 TYPE II-60" FLOW CONTROL MANHOLE 18" BYPASS RISER 6" SAND FILTER RISER 6" SAND FILTER RISER 18" BYPASS RISER NO SCALE DEBRIS BARRIER 6" MIN 2' 2' ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 May 23, 2022 21097 RCE CONTROL STRUCTURE DETAIL TOP OF SAND EL=472.66 INLET 6" PVC PIPE 6" PERF. PIPE 18" MIN DEPTH SAND SIZE SHALL BE 0.02" - 0.04" (WSDOT 9-03.13) GEOTECH SHALL VERIFY THAT SAND MEETS REQUREMENTS PRIOR TO INSTALLATION DRAIN ROCK COVER OVER PIPE 4" PERF. PIPE LAID FLAT IE=470.12 8" RISER OUTLET 8" PVC PIPE 4" PERF. PIPE W/ GEOTEXTILE WRAP INLET 6" PVC PIPE 6" PERF. PIPE 0.25' X 1' WIDE SPLASH PAD 1-1/2" WASHED GRAVEL 8" RISER OUTLET 8" PVC PIPE 18" SAND 28.5' B A - MIRAFI FILTER FABRIC (140N) A B - 8.0' HWS=472.55 CLEANOUT CAP (TYP) 12" 4' X 6' GRATED COVER FROM CONTROL STRUCTURE 0.25' X 1' WIDE SPLASH PAD 1-1/2" WASHED GRAVEL 8" RISER 4" PERF. PIPE MIRAFI FILTER FABRIC (140N) OUTLET 8" PVC PIPE BOTTOM OF SAND EL=471.16 IE=470.12 ph 206.890.8291 4715 142nd Pl. SW #B, Edmonds, WA 98026 May 23, 2022 21097 RCE SAND FILTER DETAIL Pg. 27 WWHM2012 PROJECT REPORT ___________________________________________________________________ Project Name: 21097 - sandfilter Site Name: Beehive Food Truck Park Site Address: 30400 Pacific Hwy S City : Federal Way, WA 98003 Report Date: 5/26/2022 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2021/08/18 Version : 4.2.18 ___________________________________________________________________ Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ___________________________________________________________________ High Flow Threshold for POC 1: 50 year ___________________________________________________________________ Low Flow Threshold for POC 2 : 50 Percent of the 2 Year ___________________________________________________________________ High Flow Threshold for POC 2: 50 year ___________________________________________________________________ PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Flat 1.084 Pervious Total 1.084 Impervious Land Use acre Impervious Total 0 Basin Total 1.084 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ MITIGATED LAND USE Name : Basin 1 Pg. 28 Bypass: No GroundWater: No Pervious Land Use acre C, Pasture, Flat .213 Pervious Total 0.213 Impervious Land Use acre SIDEWALKS FLAT 0.037 PARKING FLAT 0.763 POND 0.07 Impervious Total 0.87 Basin Total 1.083 _________________________________________________________________ Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 ___________________________________________________________________ Name : Sand Filter 1 Bottom Length: 14.07 ft. Bottom Width: 14.07 ft. Depth: 2.58 ft. Side slope 1: 0 To 1 Side slope 2: 0 To 1 Side slope 3: 0 To 1 Side slope 4: 0 To 1 Filtration On Hydraulic conductivity: 1 Depth of filter medium: 1.5 Total Volume Infiltrated (ac-ft.): 133.893 Total Volume Through Riser (ac-ft.): 12.711 Total Volume Through Facility (ac-ft.): 146.604 Percent Infiltrated: 91.33 Total Precip Applied to Facility: 0 Total Evap From Facility: 0 Discharge Structure Riser Height: 1.58 ft. Riser Diameter: 18 in. Notch Type: Rectangular Notch Width: 1.000 ft. Notch Height: 0.000 ft. Element Flows To: Outlet 1 Outlet 2 ___________________________________________________________________ Sand Filter Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.004 0.000 0.000 0.000 0.0287 0.004 0.000 0.000 0.004 Pg. 29 0.0573 0.004 0.000 0.000 0.004 0.0860 0.004 0.000 0.000 0.004 0.1147 0.004 0.000 0.000 0.004 0.1433 0.004 0.000 0.000 0.005 0.1720 0.004 0.000 0.000 0.005 0.2007 0.004 0.000 0.000 0.005 0.2293 0.004 0.001 0.000 0.005 0.2580 0.004 0.001 0.000 0.005 0.2867 0.004 0.001 0.000 0.005 0.3153 0.004 0.001 0.000 0.005 0.3440 0.004 0.001 0.000 0.005 0.3727 0.004 0.001 0.000 0.005 0.4013 0.004 0.001 0.000 0.005 0.4300 0.004 0.002 0.000 0.005 0.4587 0.004 0.002 0.000 0.006 0.4873 0.004 0.002 0.000 0.006 0.5160 0.004 0.002 0.000 0.006 0.5447 0.004 0.002 0.000 0.006 0.5733 0.004 0.002 0.000 0.006 0.6020 0.004 0.002 0.000 0.006 0.6307 0.004 0.002 0.000 0.006 0.6593 0.004 0.003 0.000 0.006 0.6880 0.004 0.003 0.000 0.006 0.7167 0.004 0.003 0.000 0.006 0.7453 0.004 0.003 0.000 0.006 0.7740 0.004 0.003 0.000 0.006 0.8027 0.004 0.003 0.000 0.007 0.8313 0.004 0.003 0.000 0.007 0.8600 0.004 0.003 0.000 0.007 0.8887 0.004 0.004 0.000 0.007 0.9173 0.004 0.004 0.000 0.007 0.9460 0.004 0.004 0.000 0.007 0.9747 0.004 0.004 0.000 0.007 1.0033 0.004 0.004 0.000 0.007 1.0320 0.004 0.004 0.000 0.007 1.0607 0.004 0.004 0.000 0.007 1.0893 0.004 0.004 0.000 0.007 1.1180 0.004 0.005 0.000 0.008 1.1467 0.004 0.005 0.000 0.008 1.1753 0.004 0.005 0.000 0.008 1.2040 0.004 0.005 0.000 0.008 1.2327 0.004 0.005 0.000 0.008 1.2613 0.004 0.005 0.000 0.008 1.2900 0.004 0.005 0.000 0.008 1.3187 0.004 0.006 0.000 0.008 1.3473 0.004 0.006 0.000 0.008 1.3760 0.004 0.006 0.000 0.008 1.4047 0.004 0.006 0.000 0.008 1.4333 0.004 0.006 0.000 0.009 1.4620 0.004 0.006 0.000 0.009 1.4907 0.004 0.006 0.000 0.009 1.5193 0.004 0.006 0.000 0.009 1.5480 0.004 0.007 0.000 0.009 1.5767 0.004 0.007 0.000 0.009 1.6053 0.004 0.007 0.064 0.009 1.6340 0.004 0.007 0.199 0.009 Pg. 30 1.6627 0.004 0.007 0.377 0.009 1.6913 0.004 0.007 0.589 0.009 1.7200 0.004 0.007 0.829 0.009 1.7487 0.004 0.007 1.093 0.009 1.7773 0.004 0.008 1.377 0.010 1.8060 0.004 0.008 1.677 0.010 1.8347 0.004 0.008 1.990 0.010 1.8633 0.004 0.008 2.311 0.010 1.8920 0.004 0.008 2.638 0.010 1.9207 0.004 0.008 2.966 0.010 1.9493 0.004 0.008 3.291 0.010 1.9780 0.004 0.009 3.610 0.010 2.0067 0.004 0.009 3.918 0.010 2.0353 0.004 0.009 4.213 0.010 2.0640 0.004 0.009 4.492 0.010 2.0927 0.004 0.009 4.750 0.011 2.1213 0.004 0.009 4.988 0.011 2.1500 0.004 0.009 5.202 0.011 2.1787 0.004 0.009 5.392 0.011 2.2073 0.004 0.010 5.560 0.011 2.2360 0.004 0.010 5.705 0.011 2.2647 0.004 0.010 5.831 0.011 2.2933 0.004 0.010 5.942 0.011 2.3220 0.004 0.010 6.044 0.011 2.3507 0.004 0.010 6.221 0.011 2.3793 0.004 0.010 6.335 0.011 2.4080 0.004 0.010 6.448 0.011 2.4367 0.004 0.011 6.559 0.012 2.4653 0.004 0.011 6.668 0.012 2.4940 0.004 0.011 6.775 0.012 2.5227 0.004 0.011 6.880 0.012 2.5513 0.004 0.011 6.984 0.012 2.5800 0.004 0.011 7.086 0.012 2.6087 0.004 0.011 7.187 0.012 ___________________________________________________________________ Name : Gravel Trench Bed 1 Bottom Length: 240.00 ft. Bottom Width: 107.20 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 1.75 Pour Space of material for first layer: 0.39 Material thickness of second layer: 0 Pour Space of material for second layer: 0 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 1.75 ft. Riser Diameter: 18 in. Notch Type: Rectangular Notch Width: 0.013 ft. Notch Height: 0.832 ft. Orifice 1 Diameter: 0.781 in. Elevation: 0 ft. Pg. 31 Element Flows To: Outlet 1 Outlet 2 Flow Splitter 1 ___________________________________________________________________ Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.590 0.000 0.000 0.000 0.0306 0.590 0.007 0.002 0.000 0.0611 0.590 0.014 0.004 0.000 0.0917 0.590 0.021 0.005 0.000 0.1222 0.590 0.028 0.005 0.000 0.1528 0.590 0.035 0.006 0.000 0.1833 0.590 0.042 0.007 0.000 0.2139 0.590 0.049 0.007 0.000 0.2444 0.590 0.056 0.008 0.000 0.2750 0.590 0.063 0.008 0.000 0.3056 0.590 0.070 0.009 0.000 0.3361 0.590 0.077 0.009 0.000 0.3667 0.590 0.084 0.010 0.000 0.3972 0.590 0.091 0.010 0.000 0.4278 0.590 0.098 0.010 0.000 0.4583 0.590 0.105 0.011 0.000 0.4889 0.590 0.112 0.011 0.000 0.5194 0.590 0.119 0.011 0.000 0.5500 0.590 0.126 0.012 0.000 0.5806 0.590 0.133 0.012 0.000 0.6111 0.590 0.140 0.012 0.000 0.6417 0.590 0.147 0.013 0.000 0.6722 0.590 0.154 0.013 0.000 0.7028 0.590 0.161 0.013 0.000 0.7333 0.590 0.168 0.014 0.000 0.7639 0.590 0.176 0.014 0.000 0.7944 0.590 0.183 0.014 0.000 0.8250 0.590 0.190 0.015 0.000 0.8556 0.590 0.197 0.015 0.000 0.8861 0.590 0.204 0.015 0.000 0.9167 0.590 0.211 0.015 0.000 0.9472 0.590 0.218 0.016 0.000 0.9778 0.590 0.225 0.017 0.000 1.0083 0.590 0.232 0.017 0.000 1.0389 0.590 0.239 0.018 0.000 1.0694 0.590 0.246 0.019 0.000 1.1000 0.590 0.253 0.020 0.000 1.1306 0.590 0.260 0.021 0.000 1.1611 0.590 0.267 0.022 0.000 1.1917 0.590 0.274 0.023 0.000 1.2222 0.590 0.281 0.025 0.000 1.2528 0.590 0.288 0.026 0.000 1.2833 0.590 0.295 0.027 0.000 1.3139 0.590 0.302 0.028 0.000 1.3444 0.590 0.309 0.030 0.000 1.3750 0.590 0.316 0.031 0.000 1.4056 0.590 0.323 0.032 0.000 1.4361 0.590 0.330 0.034 0.000 Pg. 32 1.4667 0.590 0.337 0.035 0.000 1.4972 0.590 0.344 0.037 0.000 1.5278 0.590 0.351 0.038 0.000 1.5583 0.590 0.359 0.040 0.000 1.5889 0.590 0.366 0.041 0.000 1.6194 0.590 0.373 0.042 0.000 1.6500 0.590 0.380 0.044 0.000 1.6806 0.590 0.387 0.045 0.000 1.7111 0.590 0.394 0.047 0.000 1.7417 0.590 0.401 0.048 0.000 1.7722 0.590 0.419 0.102 0.000 1.8028 0.590 0.437 0.242 0.000 1.8333 0.590 0.455 0.432 0.000 1.8639 0.590 0.473 0.659 0.000 1.8944 0.590 0.491 0.919 0.000 1.9250 0.590 0.509 1.204 0.000 1.9556 0.590 0.527 1.512 0.000 1.9861 0.590 0.545 1.837 0.000 2.0167 0.590 0.563 2.174 0.000 2.0472 0.590 0.581 2.520 0.000 2.0778 0.590 0.599 2.870 0.000 2.1083 0.590 0.617 3.218 0.000 2.1389 0.590 0.635 3.561 0.000 2.1694 0.590 0.653 3.894 0.000 2.2000 0.590 0.671 4.212 0.000 2.2306 0.590 0.689 4.511 0.000 2.2611 0.590 0.708 4.789 0.000 2.2917 0.590 0.726 5.043 0.000 2.3222 0.590 0.744 5.270 0.000 2.3528 0.590 0.762 5.471 0.000 2.3833 0.590 0.780 5.645 0.000 2.4139 0.590 0.798 5.795 0.000 2.4444 0.590 0.816 5.924 0.000 2.4750 0.590 0.834 6.038 0.000 2.5056 0.590 0.852 6.213 0.000 2.5361 0.590 0.870 6.337 0.000 2.5667 0.590 0.888 6.458 0.000 2.5972 0.590 0.906 6.577 0.000 2.6278 0.590 0.924 6.693 0.000 2.6583 0.590 0.942 6.808 0.000 2.6889 0.590 0.960 6.921 0.000 2.7194 0.590 0.978 7.032 0.000 2.7500 0.590 0.996 7.141 0.000 ___________________________________________________________________ Name : Flow Splitter 1 Bottom Length: 10.00 ft. Bottom Length: 10.00 ft. Depth: 10 ft. Side slope 1: 0 To 1 Side slope 2: 0 To 1 Side slope 3: 0 To 1 Side slope 4: 0 To 1 Threshold Splitter Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Primary(cfs) Secondary(cfs) Pg. 33 0.000 0.002 0.000 0.018 0.000 0.111 0.002 0.000 0.018 0.000 0.222 0.002 0.000 0.018 0.000 0.333 0.002 0.000 0.018 0.000 0.444 0.002 0.001 0.018 0.000 0.555 0.002 0.001 0.018 0.000 0.666 0.002 0.001 0.018 0.000 0.777 0.002 0.001 0.018 0.000 0.888 0.002 0.002 0.018 0.000 1.000 0.002 0.002 0.018 0.000 1.111 0.002 0.002 0.018 0.000 1.222 0.002 0.002 0.018 0.000 1.333 0.002 0.003 0.018 0.000 1.444 0.002 0.003 0.018 0.000 1.555 0.002 0.003 0.018 0.000 1.666 0.002 0.003 0.018 0.000 1.777 0.002 0.004 0.018 0.000 1.888 0.002 0.004 0.018 0.000 2.000 0.002 0.004 0.018 0.000 2.111 0.002 0.004 0.018 0.000 2.222 0.002 0.005 0.018 0.000 2.333 0.002 0.005 0.018 0.000 2.444 0.002 0.005 0.018 0.000 2.555 0.002 0.005 0.018 0.000 2.666 0.002 0.006 0.018 0.000 2.777 0.002 0.006 0.018 0.000 2.888 0.002 0.006 0.018 1000 3.000 0.002 0.006 0.018 1000 3.111 0.002 0.007 0.018 1000 3.222 0.002 0.007 0.018 1000 3.333 0.002 0.007 0.018 1000 3.444 0.002 0.007 0.018 1000 3.555 0.002 0.008 0.018 1000 3.666 0.002 0.008 0.018 1000 3.777 0.002 0.008 0.018 1000 3.888 0.002 0.008 0.018 1000 4.000 0.002 0.009 0.018 1000 4.111 0.002 0.009 0.018 1000 4.222 0.002 0.009 0.018 1000 4.333 0.002 0.009 0.018 1000 4.444 0.002 0.010 0.018 1000 4.555 0.002 0.010 0.018 1000 4.666 0.002 0.010 0.018 1000 4.777 0.002 0.011 0.018 1000 4.888 0.002 0.011 0.018 1000 5.000 0.002 0.011 0.018 1000 5.111 0.002 0.011 0.018 1000 5.222 0.002 0.012 0.018 1000 5.333 0.002 0.012 0.018 1000 5.444 0.002 0.012 0.018 1000 5.555 0.002 0.012 0.018 1000 5.666 0.002 0.013 0.018 1000 5.777 0.002 0.013 0.018 1000 5.888 0.002 0.013 0.018 1000 6.000 0.002 0.013 0.018 1000 6.111 0.002 0.014 0.018 1000 Pg. 34 6.222 0.002 0.014 0.018 1000 6.333 0.002 0.014 0.018 1000 6.444 0.002 0.014 0.018 1000 6.555 0.002 0.015 0.018 1000 6.666 0.002 0.015 0.018 1000 6.777 0.002 0.015 0.018 1000 6.888 0.002 0.015 0.018 1000 7.000 0.002 0.016 0.018 1000 7.111 0.002 0.016 0.018 1000 7.222 0.002 0.016 0.018 1000 7.333 0.002 0.016 0.018 1000 7.444 0.002 0.017 0.018 1000 7.555 0.002 0.017 0.018 1000 7.666 0.002 0.017 0.018 1000 7.777 0.002 0.017 0.018 1000 7.888 0.002 0.018 0.018 1000 8.000 0.002 0.018 0.018 1000 8.111 0.002 0.018 0.018 1000 8.222 0.002 0.018 0.018 1000 8.333 0.002 0.019 0.018 1000 8.444 0.002 0.019 0.018 1000 8.555 0.002 0.019 0.018 1000 8.666 0.002 0.019 0.018 1000 8.777 0.002 0.020 0.018 1000 8.888 0.002 0.020 0.018 1000 9.000 0.002 0.020 0.018 1000 9.111 0.002 0.020 0.018 1000 9.222 0.002 0.021 0.018 1000 9.333 0.002 0.021 0.018 1000 9.444 0.002 0.021 0.018 1000 9.555 0.002 0.021 0.018 1000 9.666 0.002 0.022 0.018 1000 9.777 0.002 0.022 0.018 1000 9.888 0.002 0.022 0.018 1000 10.00 0.002 0.023 0.018 1000 10.11 0.002 0.023 0.018 1000 ___________________________________________________________________ Discharge Structure Riser Height: 1.88 ft. Riser Diameter: 6 in. Element Flows To: Outlet 1 Outlet 2 Sand Filter 1 ___________________________________________________________________ ___________________________________________________________________ ANALYSIS RESULTS Stream Protection Duration ___________________________________________________________________ Predeveloped Landuse Totals for POC #1 Pg. 35 Total Pervious Area:1.084 Total Impervious Area:0 ___________________________________________________________________ Mitigated Landuse Totals for POC #1 Total Pervious Area:0.213 Total Impervious Area:0.87 ___________________________________________________________________ Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.031871 5 year 0.050054 10 year 0.060359 25 year 0.071276 50 year 0.078031 100 year 0.083777 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.006974 5 year 0.009428 10 year 0.010641 25 year 0.011813 50 year 0.012484 100 year 0.013023 ___________________________________________________________________ Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.031 0.005 1950 0.039 0.009 1951 0.070 0.009 1952 0.022 0.003 1953 0.018 0.007 1954 0.027 0.006 1955 0.044 0.006 1956 0.035 0.009 1957 0.028 0.006 1958 0.032 0.007 1959 0.027 0.005 1960 0.047 0.009 1961 0.027 0.009 1962 0.017 0.003 1963 0.023 0.006 1964 0.030 0.009 1965 0.022 0.009 1966 0.021 0.006 1967 0.043 0.009 1968 0.027 0.006 1969 0.026 0.005 1970 0.022 0.007 1971 0.023 0.007 1972 0.052 0.009 1973 0.024 0.009 Pg. 36 1974 0.026 0.006 1975 0.035 0.005 1976 0.025 0.006 1977 0.003 0.004 1978 0.022 0.009 1979 0.013 0.003 1980 0.050 0.009 1981 0.020 0.006 1982 0.038 0.009 1983 0.034 0.006 1984 0.021 0.004 1985 0.013 0.004 1986 0.055 0.009 1987 0.049 0.009 1988 0.019 0.005 1989 0.013 0.004 1990 0.102 0.009 1991 0.062 0.009 1992 0.024 0.009 1993 0.025 0.004 1994 0.008 0.002 1995 0.035 0.009 1996 0.075 0.009 1997 0.062 0.009 1998 0.014 0.004 1999 0.059 0.009 2000 0.025 0.008 2001 0.004 0.001 2002 0.027 0.009 2003 0.034 0.005 2004 0.045 0.009 2005 0.032 0.006 2006 0.038 0.009 2007 0.076 0.009 2008 0.098 0.010 2009 0.048 0.009 ___________________________________________________________________ Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1022 0.0098 2 0.0978 0.0095 3 0.0758 0.0095 4 0.0747 0.0094 5 0.0702 0.0094 6 0.0624 0.0094 7 0.0615 0.0094 8 0.0585 0.0094 9 0.0552 0.0094 10 0.0523 0.0094 11 0.0495 0.0094 12 0.0489 0.0094 13 0.0480 0.0094 14 0.0475 0.0094 15 0.0446 0.0094 Pg. 37 16 0.0438 0.0094 17 0.0433 0.0094 18 0.0390 0.0094 19 0.0381 0.0094 20 0.0377 0.0094 21 0.0354 0.0094 22 0.0349 0.0094 23 0.0349 0.0094 24 0.0344 0.0090 25 0.0341 0.0088 26 0.0320 0.0086 27 0.0317 0.0086 28 0.0313 0.0086 29 0.0301 0.0084 30 0.0281 0.0073 31 0.0275 0.0067 32 0.0272 0.0067 33 0.0270 0.0066 34 0.0270 0.0065 35 0.0268 0.0063 36 0.0264 0.0063 37 0.0258 0.0061 38 0.0252 0.0061 39 0.0247 0.0059 40 0.0246 0.0059 41 0.0237 0.0059 42 0.0237 0.0058 43 0.0233 0.0058 44 0.0229 0.0058 45 0.0221 0.0055 46 0.0221 0.0053 47 0.0218 0.0052 48 0.0216 0.0048 49 0.0211 0.0048 50 0.0207 0.0046 51 0.0198 0.0042 52 0.0193 0.0041 53 0.0179 0.0040 54 0.0167 0.0038 55 0.0141 0.0036 56 0.0134 0.0036 57 0.0126 0.0032 58 0.0125 0.0032 59 0.0083 0.0025 60 0.0044 0.0022 61 0.0030 0.0013 ___________________________________________________________________ Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0159 17567 15960 90 Pass Pg. 38 0.0166 16164 13509 83 Pass 0.0172 14981 11800 78 Pass 0.0178 13858 10318 74 Pass 0.0184 12816 9208 71 Pass 0.0191 11809 8455 71 Pass 0.0197 10904 7749 71 Pass 0.0203 10121 6994 69 Pass 0.0210 9383 6312 67 Pass 0.0216 8729 5709 65 Pass 0.0222 8153 5180 63 Pass 0.0228 7595 4706 61 Pass 0.0235 7060 4267 60 Pass 0.0241 6592 3906 59 Pass 0.0247 6149 3668 59 Pass 0.0253 5777 3454 59 Pass 0.0260 5431 3217 59 Pass 0.0266 5103 3022 59 Pass 0.0272 4808 2849 59 Pass 0.0279 4524 2601 57 Pass 0.0285 4252 2415 56 Pass 0.0291 4017 2246 55 Pass 0.0297 3784 2083 55 Pass 0.0304 3546 1916 54 Pass 0.0310 3339 1777 53 Pass 0.0316 3138 1611 51 Pass 0.0322 2952 1439 48 Pass 0.0329 2785 1295 46 Pass 0.0335 2599 1155 44 Pass 0.0341 2447 983 40 Pass 0.0348 2304 886 38 Pass 0.0354 2162 816 37 Pass 0.0360 2026 754 37 Pass 0.0366 1898 676 35 Pass 0.0373 1790 579 32 Pass 0.0379 1689 478 28 Pass 0.0385 1586 423 26 Pass 0.0391 1483 381 25 Pass 0.0398 1379 342 24 Pass 0.0404 1292 300 23 Pass 0.0410 1219 235 19 Pass 0.0417 1154 199 17 Pass 0.0423 1098 168 15 Pass 0.0429 1048 151 14 Pass 0.0435 997 139 13 Pass 0.0442 930 127 13 Pass 0.0448 883 112 12 Pass 0.0454 837 108 12 Pass 0.0460 789 102 12 Pass 0.0467 743 79 10 Pass 0.0473 713 56 7 Pass 0.0479 668 47 7 Pass 0.0486 630 38 6 Pass 0.0492 596 35 5 Pass 0.0498 565 35 6 Pass 0.0504 539 34 6 Pass 0.0511 496 34 6 Pass Pg. 39 0.0517 473 33 6 Pass 0.0523 434 32 7 Pass 0.0529 399 32 8 Pass 0.0536 366 32 8 Pass 0.0542 348 31 8 Pass 0.0548 323 31 9 Pass 0.0555 296 30 10 Pass 0.0561 272 30 11 Pass 0.0567 256 27 10 Pass 0.0573 235 24 10 Pass 0.0580 217 21 9 Pass 0.0586 195 18 9 Pass 0.0592 180 17 9 Pass 0.0598 158 17 10 Pass 0.0605 145 17 11 Pass 0.0611 129 15 11 Pass 0.0617 119 15 12 Pass 0.0624 109 15 13 Pass 0.0630 97 14 14 Pass 0.0636 91 13 14 Pass 0.0642 82 12 14 Pass 0.0649 76 11 14 Pass 0.0655 69 9 13 Pass 0.0661 61 8 13 Pass 0.0667 54 7 12 Pass 0.0674 48 5 10 Pass 0.0680 41 4 9 Pass 0.0686 38 0 0 Pass 0.0692 33 0 0 Pass 0.0699 27 0 0 Pass 0.0705 22 0 0 Pass 0.0711 21 0 0 Pass 0.0718 20 0 0 Pass 0.0724 19 0 0 Pass 0.0730 17 0 0 Pass 0.0736 13 0 0 Pass 0.0743 12 0 0 Pass 0.0749 8 0 0 Pass 0.0755 4 0 0 Pass 0.0761 3 0 0 Pass 0.0768 3 0 0 Pass 0.0774 3 0 0 Pass 0.0780 3 0 0 Pass _____________________________________________________ ___________________________________________________________________ Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.1125 acre-feet On-line facility target flow: 0.1398 cfs. Adjusted for 15 min: 0.1398 cfs. Off-line facility target flow: 0.0789 cfs. Adjusted for 15 min: 0.0789 cfs. ___________________________________________________________________ LID Report Pg. 40 LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Sand Filter 1 POC N 133.41 N 0.00 Flow Splitter 1 N 134.15 N 0.54 Gravel Trench Bed 1 N 134.52 N 0.00 Total Volume Infiltrated 402.08 0.00 0.00 0.18 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed ___________________________________________________________________ POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run.Perlnd and Implnd Changes No changes have been made. ___________________________________________________________________ This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2022; All Rights Reserved. Pg. 41 WWHM2012 PROJECT REPORT ___________________________________________________________________ Project Name: 21097 - gravel trench 1.75 Site Name: Beehive Food Truck Park Site Address: 30400 Pacific Hwy S City : Federal Way, WA 98003 Report Date: 5/26/2022 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2021/08/18 Version : 4.2.18 ___________________________________________________________________ Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ___________________________________________________________________ High Flow Threshold for POC 1: 50 year ___________________________________________________________________ PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Forest, Flat 1.084 Pervious Total 1.084 Impervious Land Use acre Impervious Total 0 Basin Total 1.084 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre Pg. 42 C, Pasture, Flat .213 Pervious Total 0.213 Impervious Land Use acre SIDEWALKS FLAT 0.037 PARKING FLAT 0.763 POND 0.07 Impervious Total 0.87 Basin Total 1.083 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 ___________________________________________________________________ Name : Gravel Trench Bed 1 Bottom Length: 240.00 ft. Bottom Width: 107.20 ft. Trench bottom slope 1: 0 To 1 Trench Left side slope 0: 0 To 1 Trench right side slope 2: 0 To 1 Material thickness of first layer: 1.75 Pour Space of material for first layer: 0.39 Material thickness of second layer: 0 Pour Space of material for second layer: 0 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Discharge Structure Riser Height: 1.75 ft. Riser Diameter: 18 in. Notch Type: Rectangular Notch Width: 0.013 ft. Notch Height: 0.832 ft. Orifice 1 Diameter: 0.781 in. Elevation: 0 ft. Element Flows To: Outlet 1 Outlet 2 ___________________________________________________________________ Gravel Trench Bed Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.590 0.000 0.000 0.000 0.0306 0.590 0.007 0.002 0.000 0.0611 0.590 0.014 0.004 0.000 0.0917 0.590 0.021 0.005 0.000 0.1222 0.590 0.028 0.005 0.000 0.1528 0.590 0.035 0.006 0.000 0.1833 0.590 0.042 0.007 0.000 0.2139 0.590 0.049 0.007 0.000 0.2444 0.590 0.056 0.008 0.000 Pg. 43 0.2750 0.590 0.063 0.008 0.000 0.3056 0.590 0.070 0.009 0.000 0.3361 0.590 0.077 0.009 0.000 0.3667 0.590 0.084 0.010 0.000 0.3972 0.590 0.091 0.010 0.000 0.4278 0.590 0.098 0.010 0.000 0.4583 0.590 0.105 0.011 0.000 0.4889 0.590 0.112 0.011 0.000 0.5194 0.590 0.119 0.011 0.000 0.5500 0.590 0.126 0.012 0.000 0.5806 0.590 0.133 0.012 0.000 0.6111 0.590 0.140 0.012 0.000 0.6417 0.590 0.147 0.013 0.000 0.6722 0.590 0.154 0.013 0.000 0.7028 0.590 0.161 0.013 0.000 0.7333 0.590 0.168 0.014 0.000 0.7639 0.590 0.176 0.014 0.000 0.7944 0.590 0.183 0.014 0.000 0.8250 0.590 0.190 0.015 0.000 0.8556 0.590 0.197 0.015 0.000 0.8861 0.590 0.204 0.015 0.000 0.9167 0.590 0.211 0.015 0.000 0.9472 0.590 0.218 0.016 0.000 0.9778 0.590 0.225 0.017 0.000 1.0083 0.590 0.232 0.017 0.000 1.0389 0.590 0.239 0.018 0.000 1.0694 0.590 0.246 0.019 0.000 1.1000 0.590 0.253 0.020 0.000 1.1306 0.590 0.260 0.021 0.000 1.1611 0.590 0.267 0.022 0.000 1.1917 0.590 0.274 0.023 0.000 1.2222 0.590 0.281 0.025 0.000 1.2528 0.590 0.288 0.026 0.000 1.2833 0.590 0.295 0.027 0.000 1.3139 0.590 0.302 0.028 0.000 1.3444 0.590 0.309 0.030 0.000 1.3750 0.590 0.316 0.031 0.000 1.4056 0.590 0.323 0.032 0.000 1.4361 0.590 0.330 0.034 0.000 1.4667 0.590 0.337 0.035 0.000 1.4972 0.590 0.344 0.037 0.000 1.5278 0.590 0.351 0.038 0.000 1.5583 0.590 0.359 0.040 0.000 1.5889 0.590 0.366 0.041 0.000 1.6194 0.590 0.373 0.042 0.000 1.6500 0.590 0.380 0.044 0.000 1.6806 0.590 0.387 0.045 0.000 1.7111 0.590 0.394 0.047 0.000 1.7417 0.590 0.401 0.048 0.000 1.7722 0.590 0.419 0.102 0.000 1.8028 0.590 0.437 0.242 0.000 1.8333 0.590 0.455 0.432 0.000 1.8639 0.590 0.473 0.659 0.000 1.8944 0.590 0.491 0.919 0.000 1.9250 0.590 0.509 1.204 0.000 1.9556 0.590 0.527 1.512 0.000 Pg. 44 1.9861 0.590 0.545 1.837 0.000 2.0167 0.590 0.563 2.174 0.000 2.0472 0.590 0.581 2.520 0.000 2.0778 0.590 0.599 2.870 0.000 2.1083 0.590 0.617 3.218 0.000 2.1389 0.590 0.635 3.561 0.000 2.1694 0.590 0.653 3.894 0.000 2.2000 0.590 0.671 4.212 0.000 2.2306 0.590 0.689 4.511 0.000 2.2611 0.590 0.708 4.789 0.000 2.2917 0.590 0.726 5.043 0.000 2.3222 0.590 0.744 5.270 0.000 2.3528 0.590 0.762 5.471 0.000 2.3833 0.590 0.780 5.645 0.000 2.4139 0.590 0.798 5.795 0.000 2.4444 0.590 0.816 5.924 0.000 2.4750 0.590 0.834 6.038 0.000 2.5056 0.590 0.852 6.213 0.000 2.5361 0.590 0.870 6.337 0.000 2.5667 0.590 0.888 6.458 0.000 2.5972 0.590 0.906 6.577 0.000 2.6278 0.590 0.924 6.693 0.000 2.6583 0.590 0.942 6.808 0.000 2.6889 0.590 0.960 6.921 0.000 2.7194 0.590 0.978 7.032 0.000 2.7500 0.590 0.996 7.141 0.000 ___________________________________________________________________ __________________________________________________________________ ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.084 Total Impervious Area:0 ___________________________________________________________________ Mitigated Landuse Totals for POC #1 Total Pervious Area:0.213 Total Impervious Area:0.87 ___________________________________________________________________ Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.031871 5 year 0.050054 10 year 0.060359 25 year 0.071276 50 year 0.078031 100 year 0.083777 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.01879 5 year 0.027338 Pg. 45 10 year 0.034087 25 year 0.043971 50 year 0.052397 100 year 0.061803 ___________________________________________________________________ Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.031 0.014 1950 0.039 0.018 1951 0.070 0.042 1952 0.022 0.013 1953 0.018 0.016 1954 0.027 0.015 1955 0.044 0.015 1956 0.035 0.026 1957 0.028 0.015 1958 0.032 0.017 1959 0.027 0.014 1960 0.047 0.034 1961 0.027 0.020 1962 0.017 0.013 1963 0.023 0.016 1964 0.030 0.018 1965 0.022 0.023 1966 0.021 0.015 1967 0.043 0.018 1968 0.027 0.015 1969 0.026 0.015 1970 0.022 0.016 1971 0.023 0.016 1972 0.052 0.034 1973 0.024 0.023 1974 0.026 0.016 1975 0.035 0.015 1976 0.025 0.015 1977 0.003 0.013 1978 0.022 0.018 1979 0.013 0.012 1980 0.050 0.038 1981 0.020 0.016 1982 0.038 0.027 1983 0.034 0.016 1984 0.021 0.013 1985 0.013 0.014 1986 0.055 0.020 1987 0.049 0.031 1988 0.019 0.014 1989 0.013 0.013 1990 0.102 0.034 1991 0.062 0.032 1992 0.024 0.018 1993 0.025 0.013 1994 0.008 0.012 1995 0.035 0.021 Pg. 46 1996 0.075 0.041 1997 0.062 0.045 1998 0.014 0.013 1999 0.059 0.034 2000 0.025 0.018 2001 0.004 0.011 2002 0.027 0.022 2003 0.034 0.015 2004 0.045 0.042 2005 0.032 0.015 2006 0.038 0.026 2007 0.076 0.068 2008 0.098 0.038 2009 0.048 0.024 ___________________________________________________________________ Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1022 0.0684 2 0.0978 0.0447 3 0.0758 0.0425 4 0.0747 0.0419 5 0.0702 0.0406 6 0.0624 0.0382 7 0.0615 0.0377 8 0.0585 0.0344 9 0.0552 0.0343 10 0.0523 0.0340 11 0.0495 0.0339 12 0.0489 0.0318 13 0.0480 0.0310 14 0.0475 0.0274 15 0.0446 0.0261 16 0.0438 0.0257 17 0.0433 0.0239 18 0.0390 0.0235 19 0.0381 0.0231 20 0.0377 0.0221 21 0.0354 0.0207 22 0.0349 0.0205 23 0.0349 0.0202 24 0.0344 0.0184 25 0.0341 0.0182 26 0.0320 0.0180 27 0.0317 0.0180 28 0.0313 0.0180 29 0.0301 0.0178 30 0.0281 0.0167 31 0.0275 0.0161 32 0.0272 0.0161 33 0.0270 0.0160 34 0.0270 0.0159 35 0.0268 0.0157 36 0.0264 0.0157 37 0.0258 0.0155 Pg. 47 38 0.0252 0.0155 39 0.0247 0.0154 40 0.0246 0.0153 41 0.0237 0.0152 42 0.0237 0.0152 43 0.0233 0.0152 44 0.0229 0.0149 45 0.0221 0.0149 46 0.0221 0.0147 47 0.0218 0.0146 48 0.0216 0.0142 49 0.0211 0.0142 50 0.0207 0.0140 51 0.0198 0.0136 52 0.0193 0.0135 53 0.0179 0.0134 54 0.0167 0.0131 55 0.0141 0.0130 56 0.0134 0.0129 57 0.0126 0.0126 58 0.0125 0.0126 59 0.0083 0.0119 60 0.0044 0.0116 61 0.0030 0.0112 ___________________________________________________________________ Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0159 17567 15960 90 Pass 0.0166 16164 13509 83 Pass 0.0172 14981 11800 78 Pass 0.0178 13858 10318 74 Pass 0.0184 12816 9208 71 Pass 0.0191 11809 8455 71 Pass 0.0197 10904 7749 71 Pass 0.0203 10121 6994 69 Pass 0.0210 9383 6312 67 Pass 0.0216 8729 5709 65 Pass 0.0222 8153 5180 63 Pass 0.0228 7595 4706 61 Pass 0.0235 7060 4267 60 Pass 0.0241 6592 3906 59 Pass 0.0247 6149 3668 59 Pass 0.0253 5777 3454 59 Pass 0.0260 5431 3217 59 Pass 0.0266 5103 3022 59 Pass 0.0272 4808 2849 59 Pass 0.0279 4524 2601 57 Pass 0.0285 4252 2415 56 Pass 0.0291 4017 2246 55 Pass 0.0297 3784 2083 55 Pass Pg. 48 0.0304 3546 1916 54 Pass 0.0310 3339 1777 53 Pass 0.0316 3138 1611 51 Pass 0.0322 2952 1439 48 Pass 0.0329 2785 1295 46 Pass 0.0335 2599 1155 44 Pass 0.0341 2447 983 40 Pass 0.0348 2304 886 38 Pass 0.0354 2162 816 37 Pass 0.0360 2026 754 37 Pass 0.0366 1898 676 35 Pass 0.0373 1790 579 32 Pass 0.0379 1689 478 28 Pass 0.0385 1586 423 26 Pass 0.0391 1483 381 25 Pass 0.0398 1379 342 24 Pass 0.0404 1292 300 23 Pass 0.0410 1219 235 19 Pass 0.0417 1154 199 17 Pass 0.0423 1098 168 15 Pass 0.0429 1048 151 14 Pass 0.0435 997 139 13 Pass 0.0442 930 127 13 Pass 0.0448 883 112 12 Pass 0.0454 837 108 12 Pass 0.0460 789 102 12 Pass 0.0467 743 79 10 Pass 0.0473 713 56 7 Pass 0.0479 668 47 7 Pass 0.0486 630 38 6 Pass 0.0492 596 35 5 Pass 0.0498 565 35 6 Pass 0.0504 539 34 6 Pass 0.0511 496 34 6 Pass 0.0517 473 33 6 Pass 0.0523 434 32 7 Pass 0.0529 399 32 8 Pass 0.0536 366 32 8 Pass 0.0542 348 31 8 Pass 0.0548 323 31 9 Pass 0.0555 296 30 10 Pass 0.0561 272 30 11 Pass 0.0567 256 27 10 Pass 0.0573 235 24 10 Pass 0.0580 217 21 9 Pass 0.0586 195 18 9 Pass 0.0592 180 17 9 Pass 0.0598 158 17 10 Pass 0.0605 145 17 11 Pass 0.0611 129 15 11 Pass 0.0617 119 15 12 Pass 0.0624 109 15 13 Pass 0.0630 97 14 14 Pass 0.0636 91 13 14 Pass 0.0642 82 12 14 Pass 0.0649 76 11 14 Pass Pg. 49 0.0655 69 9 13 Pass 0.0661 61 8 13 Pass 0.0667 54 7 12 Pass 0.0674 48 5 10 Pass 0.0680 41 4 9 Pass 0.0686 38 0 0 Pass 0.0692 33 0 0 Pass 0.0699 27 0 0 Pass 0.0705 22 0 0 Pass 0.0711 21 0 0 Pass 0.0718 20 0 0 Pass 0.0724 19 0 0 Pass 0.0730 17 0 0 Pass 0.0736 13 0 0 Pass 0.0743 12 0 0 Pass 0.0749 8 0 0 Pass 0.0755 4 0 0 Pass 0.0761 3 0 0 Pass 0.0768 3 0 0 Pass 0.0774 3 0 0 Pass 0.0780 3 0 0 Pass _____________________________________________________ ___________________________________________________________________ Water Quality BMP Flow and Volume for POC #1 On-line facility volume: 0.0288 acre-feet On-line facility target flow: 0.0145 cfs. Adjusted for 15 min: 0.0145 cfs. Off-line facility target flow: 0.0096 cfs. Adjusted for 15 min: 0.0096 cfs. ___________________________________________________________________ LID Report LID Technique Used for Total Volume Volume Infiltration Cumulative Percent Water Quality Percent Comment Treatment? Needs Through Volume Volume Volume Water Quality Treatment Facility (ac-ft.) Infiltration Infiltrated Treated (ac-ft) (ac-ft) Credit Gravel Trench Bed 1 POC N 134.52 N 0.00 Total Volume Infiltrated 134.52 0.00 0.00 0.00 0.00 0% No Treat. Credit Compliance with LID Standard 8 Duration Analysis Result = Passed ___________________________________________________________________ Perlnd and Implnd Changes No changes have been made. ___________________________________________________________________ This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2022; All Rights Reserved. Pg. 50 SECTION 5: CONVEYANCE SYSTEM AND ANALYSIS The most constrained pipe (i.e. smallest diameter and shallowest slope) was considered in order to ensure sufficient capacity. Pipe capacity using Manning’s equation: 𝑄=1.49 𝑛∗𝐴∗𝑅௛ ଶ ଷ ∗𝑆 ଵ ଶ where 𝑛= Manning’s coefficient 𝑄= flow rate 𝐴= cross-sectional area =𝜋𝑅௛ଶ 𝑅௛ = hydraulic radius 𝑆= pipe slope given 𝑛= 0.012 [PVC] 𝑅௛ = 8 in 𝑆= 0.6% 𝑄௙௨௟௟ = 1.017 cfs 𝑄଺଴%= 0.610 cfs Under developed, unmitigated conditions, 𝑄ଶହ௬௥ = 0.5636 cfs 𝑄ଵ଴଴௬௥ = 0.6853 cfs Therefore, all pipes will have sufficient capacity to convey 25- and 100-year peak flows at full capacity. The 25-year peak flows will be adequately conveyed at just over 60% pipe capacity (67%). Developed, mitigated25-year flow rate minus2-year flow rate, calculatedusing WWHM 2012 Developed, mitigated 2-yearflow rate, calculated usingWWHM 2012 Pg. 53 SECTION 6: SPECIAL REPORTS AND STUDIES Geotechnical Investigation Proposed Parking Lot Expansion and Surface Structures, performed Cobalt GeoSciences, dated February 16, 2022. To be provided as a separate document. Pg. 54 SECTION 7: OTHER PERMITS  Land Clearing and Grading Permit  Tree Permit  Sensitive Area Work Permit  Drainage Review  Right of Way  Sewer Permit  Plumbing Permit  Construction Stormwater Permit Pg. 55 SECTION 8: CSWPPP ANALYSIS AND DESIGN TESC measures are put into place to prevent sediment from leaving the site. The proposed TESC plan will include, but not be limited to, the following guidelines set in the 2021 KCSWDM in order to comply with Core Requirement No. 5. 1. Clearing Limits – Clearing limits specify the boundary of the work to be done. Clearing are defined on the TESC plans and will be flagged in the field. 2. Cover Measures – Cover measures are involved (typically) with the means to control erosion of exposed soil and are specified on the TESC plans. 3. Perimeter Protection – Perimeter protection keeps site sediment from leaving the construction site. This type of protection typically involves a silt fence. The silt fence and clearing limits are shown on the TESC plans. 4. Traffic Area Stabilization – Traffic area stabilization is addressed by a stabilized construction entrance. 5. Sediment Retention – Retention will be established by silt fences around the perimeter and catch basin inserts that will control of the on-site sediment- laden water. 6. Surface Water Collection – An interceptor ditch with check dams is shown in the plans and will be implemented in the field if necessary. 7. Dewatering Control – Any water from dewatering shall be filtered or contained so sediment can filter out prior to discharge downstream. 8. Dust Control – Dust control will be provided by sprinkling. 9. Flow Control – Stormwater will be routed to a Sediment Pond, during site preparation. The detention vault will provide further control once constructed. 10. Wet Season Construction – Construction will be conducted according to the jurisdiction’s standards during the wet season. 11. Construction Within Sensitive Areas and Buffers - Any construction within the wetland buffer will be subject to sensitive areas restrictions and is contained in the TESC notes. 12. Maintenance – Maintenance requirements are detailed in the TESC notes within the engineering plans. 13. Final Stabilization – Upon completion of the project, all disturbed areas will be stabilized and Best Management Practices removed. Pg. 56 SECTION 9: BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT These will be submitted separately. Pg. 57 SECTION 10: OPERATIONS AND MAINTENANCE MANUAL The drainage facilities on this project will be privately owned and maintained by the owner. See the following pages. NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damage T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate. Pg. 58 Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If Applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. Pg. 59 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Pg. 60 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. NO. 7 – DEBRIS BARRIERS (E.G., TRASH RACKS) Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed. Site Trash and debris Trash or debris plugging more than 20% of the area of the barrier. Barrier clear to receive capacity flow. Sediment accumulation Sediment accumulation of greater than 20% of the area of the barrier Barrier clear to receive capacity flow. Structure Cracked broken or loose Structure which bars attached to is damaged - pipe is loose or cracked or concrete structure is cracked, broken of loose. Structure barrier attached to is sound. Bars Bar spacing Bar spacing exceeds 6 inches. Bars have at most 6 inches spacing. Damaged or missing bars Bars are bent out of shape more than 3 inches. Bars in place with no bends more than ¾ inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars are loose and rust is causing 50% deterioration to any part of barrier. Repair or replace barrier to design standards. Pg. 61 NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. MAINTENANCE INSTRUCTIONS FOR PERMEABLE PAVEMENT (NON- VEGETATED) Your property contains a stormwater management flow control BMP (best management practice) called "permeable pavement," which was installed to minimize the stormwater quantity and quality impacts of some or all of the paved surfaces on your property. Permeable pavements reduce the amount of rainfall that becomes runoff by allowing water to seep through the pavement into a free-draining gravel or sand bed, where it can be infiltrated into the ground. Permeable Pavements The type(s) of permeable pavement used on your property is (CHECK THE BOX(ES) THAT APPLY): porous concrete porous asphaltic concrete permeable pavers modular grid pavement. MAINTENANCE RESTRICTIONS The area covered by permeable pavement as depicted by the flow control BMP site plan and design details must be maintained as permeable pavement and may not be changed without written approval either from the King County Water and Land Resources Division or through a future development permit from King County. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES • Permeable pavements must be inspected after one major storm each year to make sure it is working properly. More frequent inspection is recommended. • Prolonged ponding or standing water on the pavement surface is a sign that the system is defective and may need to be replaced. If this occurs, contact the pavement installer or the King County Water and Land Resources Division for further instructions. • A typical permeable pavement system has a life expectancy of approximately 25-years. To help extend the useful life of the system, the surface of the permeable pavement should be kept clean, stable and free of leaves, debris, and sediment through regular sweeping or vacuum sweeping. Aggregate fill in modular grid pavement may need periodic surface replenishment. • The owner is responsible for the repair of all ruts, deformation, and/or broken paving units. RECORDING REQUIREMENT These permeable pavement flow control BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the King County Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the King County Department of Permitting and Environmental Services (DPER) may require additional instructions based on site-specific conditions. See King County’s Surface Water Design Manual website for additional information and updates. NO. 30 – PERMEABLE PAVEMENT BMP Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Preventative Surface cleaning/ vegetation control Media surface vacuumed or pressure washed annually, vegetation controlled to design maximum. Weed growth suggesting sediment accumulation. No dirt, sediment, or debris clogging porous media, or vegetation limiting infiltration. Porous Concrete, Porous Asphaltic Concrete, and Permeable Pavers Trash and debris Trash and debris on the pavement interfering with infiltration; leaf drop in fall season. No trash or debris interfering with infiltration. Sediment accumulation Sediment accumulation on the pavement interfering with infiltration; runoff from adjacent areas depositing sediment/debris on pavement. Pavement infiltrates as designed; adjacent areas stabilized. Infiltration rate Pavement does not infiltrate at a rate of 10 inches per hour. Pavement infiltrates at a rate greater than 10 inches per hour. Ponding Standing water for a long period of time on the surface of the pavement. Standing water infiltrates at the desired rate. Broken or cracked pavement Pavement is broken or cracked. No broken pavement or cracks on the surface of the pavement. Settlement Uneven pavement surface indicating settlement of the subsurface layer. Pavement surface is uniformly level. Moss growth Moss growing on pavement interfering with infiltration. No moss interferes with infiltration. Inflow Inflow to the pavement is diverted, restricted, or depositing sediment and debris on the pavement. Inflow to pavement is unobstructed and not bringing sediment or debris to the pavement. Underdrain Underdrain is not flowing when pavement has been infiltrating water. Underdrain flows freely when water is present. Overflow Overflow not controlling excess water to desired location; native soil is exposed or other signs of erosion damage are present. Overflow permits excess water to leave the site at the desired location; Overflow is stabilized and appropriately armored. Permeable Pavers Broken or missing pavers Broken or missing paving blocks on surface of pavement. No missing or broken paving blocks interfering with infiltration. Level surface Uneven surface due to settlement or scour of fill in the interstices of the paving blocks. Pavement surface is uniformly level. Compaction Poor infiltration due to soil compaction between paving blocks. No soil compaction in the interstices of the paver blocks limiting infiltration. Dead grass Grass in the interstices of the paving blocks is dead. Healthy grass is growing in the interstices of the paver blocks. Inspection Frequency Annually and after large storms, and as needed seasonally to control leaf drop, evergreen needles etc. Permeable pavement is functioning normally. NO. 1 – DETENTION PONDS Maintenance Component Defect or Problem Conditions When Maintenance Is Needed Results Expected When Maintenance Is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Top or Side Slopes of Dam, Berm or Embankment 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 removed or destroyed and dam or berm repaired. Tree growth Tree growth threatens integrity of slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat or not interfering with access or maintenance, they do not need to be removed. Trees do not hinder facility performance or maintenance activities. Erosion Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Any erosion observed on a compacted slope. Slopes stabilized using appropriate erosion control measures. If erosion is occurring on compacted slope, a licensed civil engineer should be consulted to resolve source of erosion. Settlement Any part of a dam, berm or embankment that has settled 4 inches lower than the design elevation. Top or side slope restored to design dimensions. If settlement is significant, a licensed civil engineer should be consulted to determine the cause of the settlement. Storage Area Sediment accumulation Accumulated sediment that exceeds 10% of the designed pond depth. Sediment cleaned out to designed pond shape and depth; pond reseeded if necessary to control erosion. Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced. Inlet/Outlet Pipe. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Emergency Overflow/Spillway Tree growth Tree growth impedes flow or threatens stability of spillway. Trees removed. Rock missing Only one layer of rock exists above native soil in area five square feet or larger or any exposure of native soil on the spillway. Spillway restored to design standards. NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation 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 ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. NO. 8 – ENERGY DISSIPATERS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed. Site Trash and debris Trash and/or debris accumulation. Dissipater clear of trash and/or debris. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Rock Pad Missing or moved Rock Only one layer of rock exists above native soil in area five square feet or larger or any exposure of native soil. Rock pad prevents erosion. Dispersion Trench Pipe plugged with sediment Accumulated sediment that exceeds 20% of the design depth. Pipe cleaned/flushed so that it matches design. Not discharging water properly Visual evidence of water discharging at concentrated points along trench (normal condition is a “sheet flow” of water along trench). Water discharges from feature by sheet flow. Perforations plugged. Over 1/4 of perforations in pipe are plugged with debris or sediment. Perforations freely discharge flow. Water flows out top of “distributor” catch basin. Water flows out of distributor catch basin during any storm less than the design storm. No flow discharges from distributor catch basin. Receiving area over-saturated Water in receiving area is causing or has potential of causing landslide problems. No danger of landslides. Gabions Damaged mesh Mesh of gabion broken, twisted or deformed so structure is weakened or rock may fall out. Mesh is intact, no rock missing. Corrosion Gabion mesh shows corrosion through more than ¼ of its gage. All gabion mesh capable of containing rock and retaining designed form. Collapsed or deformed baskets Gabion basket shape deformed due to any cause. All gabion baskets intact, structure stands as designed. Missing rock Any rock missing that could cause gabion to loose structural integrity. No rock missing. Manhole/Chamber Worn or damaged post, baffles or side of chamber Structure dissipating flow deteriorates to ½ or original size or any concentrated worn spot exceeding one square foot which would make structure unsound. Structure is in no danger of failing. Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch or any evidence of soil entering the structure through cracks, or maintenance inspection personnel determines that the structure is not structurally sound. Manhole/chamber is sealed and structurally sound. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No soil or water enters and no water discharges at the joint of inlet/outlet pipes. NO. 9 – FENCING Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12- 18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. NO. 11 – GROUNDS (LANDSCAPING) Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash or litter Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. NO. 17 – WETVAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Treatment Area Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won’t seal Valve does not seal completely. Valve completely seals closed. Access Manhole Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Access doors/plate has gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. NO. 20 – SAND FILTER VAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Pre-Treatment Chamber Sediment accumulation Sediment accumulation exceeds the depth of the sediment zone plus 6 inches. Sediment storage contains no sediment. Sand Filter Media Sediment accumulation Sediment depth exceeds ½-inch on sand filter media. Sand filter freely drains at normal rate. Trash and debris Trash and debris accumulated in vault (floatables and non-floatables). No trash or debris in vault. Plugging Drawdown of water through the sand filter media, takes longer than 24 hours, and/or flow through the overflow pipes occurs frequently. A sieve analysis of >4% -100 or >2% -200 requires replacing sand filter media. Sand filter media drawdown rate is normal. Short circuiting Seepage or flow occurs along the vault walls and corners. Sand eroding near inflow area. Cleanout wyes are not watertight. Sand filter media section re-laid and compacted along perimeter of vault to form a semi-seal. Erosion protection added to dissipate force of incoming flow and curtail erosion. Vault Structure Damaged to walls, frame, bottom and/or top slab. Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault replaced or repaired to provide complete sealing of the structure. Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Underdrains and Cleanouts Sediment/debris Underdrains or clean-outs partially plugged, filled with sediment and/or debris or not watertight. Underdrains and clean-outs free of sediment and debris and sealed. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate.