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Home My WebLink AboutAvana Ridge PUD TIR 151229© 2015 D. R. STRONG Consulting Engineers Inc. Preliminary Technical Information Report (TIR) for AVANA RIDGE PUD 17249 Benson Road S and 10615 SE 172nd Street Renton, Washington ____________________________________________________________________________ DRS Project No. 15088 Renton File No. PRE15-000611 Owner/Applicant Avana Ridge, LLC 9725 SE 36th Street, Suite 214 Mercer Island, Washington 98040 Report Prepared by D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue Kirkland WA 98033 (425) 827-3063 Report Issue Date December 28, 2015 2015 D. R. STRONG Consulting Engineers Inc. i Avana Ridge Technical Information Report Renton, Washington PRELIMINARY TECHNICAL INFORMATION REPORT AVANA RIDGE TABLE OF CONTENTS SECTION I .................................................................................................................................................... 1 PROJECT OVERVIEW: ............................................................................................................................ 1 PREDEVELOPED SITE CONDITIONS: ................................................................................................... 1 DEVELOPED SITE CONDITIONS: ........................................................................................................... 1 NATURAL DRAINAGE SYSTEM FUNCTIONS: ....................................................................................... 3 FIGURE 1. TIR WORKSHEET ............................................................................................................ 4 FIGURE 2. VICINITY MAP .................................................................................................................. 9 FIGURE 3. DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS ........................... 10 FIGURE 4. SOILS ............................................................................................................................. 11 SECTION II ................................................................................................................................................. 14 CONDITIONS AND REQUIREMENTS SUMMARY ................................................................................ 14 SECTION III ................................................................................................................................................ 16 OFF-SITE ANALYSIS ............................................................................................................................. 16 SECTION IV ................................................................................................................................................ 17 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN .................................. 17 EXISTING SITE HYDROLOGY .............................................................................................................. 17 FIGURE 5. PREDEVELOPMENT AREA MAP .................................................................................. 18 DEVELOPED SITE HYDROLOGY ......................................................................................................... 19 BYPASS AREA HYDROLOGY ............................................................................................................... 20 FIGURE 6. POST DEVELOPMENT AREA MAP ............................................................................... 21 PERFORMANCE STANDARDS ............................................................................................................. 22 FLOW CONTROL SYSTEM ................................................................................................................... 22 FIGURE 7. DETENTION & WATER QUALITY FACILITY DETAILS ................................................ 28 SECTION V ................................................................................................................................................. 29 CONVEYANCE SYSTEM ANALYSIS AND DESIGN .............................................................................. 29 SECTION VI ................................................................................................................................................ 30 SPECIAL REPORTS AND STUDIES ...................................................................................................... 30 SECTION VII ............................................................................................................................................... 31 OTHER PERMITS, VARIANCES AND ADJUSTMENTS ........................................................................ 31 SECTION VIII .............................................................................................................................................. 32 ESC AND CSWPPP ANALYSIS AND DESIGN ...................................................................................... 32 SECTION IX ................................................................................................................................................ 33 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ........................ 33 STORMWATER FACILITY SUMMARY SHEET ..................................................................................... 34 SECTION X ................................................................................................................................................. 35 OPERATIONS AND MAINTENANCE MANUAL ..................................................................................... 35 APPENDIX A ............................................................................................................................................... 36 2015 D. R. STRONG Consulting Engineers Inc. 1 Avana Ridge Technical Information Report Renton, Washington SECTION I PROJECT OVERVIEW: The applicant is seeking approval to construct 74 apartment units, surface parking, and amenities on 3.78 acres (Parcel Numbers 292305900 and 292309148) (Project). The Project is located at 17249 Benson Road S in Renton, Washington. PREDEVELOPED SITE CONDITIONS: Total site area is approximately 164,828 s.f. (3.78 acres) (Site). The Parcels are currently undeveloped and are heavily forested with moderate underbrush. The predeveloped Site is contained within one Threshold Discharge Area (TDA). The TDA has two Natural Discharge Areas (NDAs), NDA 1 and NDA 2. Runoff from NDA 1 discharges at the Site’s western property line (south of NDA 2) and heads north through the conveyance system in Benson Drive S, where it meets NDA 2. NDA 2 discharges across the western property line (north of NDA1). Flow from both NDAs eventually crosses under Benson Road S in a westerly direction. Runoff outlets into a ditch between parcels 2923059150 and 2923059134, flowing west. Before reaching Cedar Ave S, flow is conveyed into a system of pipes and catch basins and continues west along S 36th Street. Runoff is conveyed south between parcels 1441000150 and 1441000170 before moving west – parallel to S 36th Street along the south side of the parcels. Runoff crosses under Wells Ave S and outfalls into parcel 144100TRCT – a tract for an adjacent development. Based on available topography, runoff sheet flows west through the tract into another tract (810630TRCT). Runoff appears to continue into a pond in parcel 8106301170. Overflow from the pond travels southwest to Morris Ave S, where it continues south. Runoff continues south, crossing under S 38th Ct and eventually outfalling into Panther Creek. Panther Creek flows north and eventually becomes a tributary for Black River and the Duwamish River. DEVELOPED SITE CONDITIONS: The applicant is seeking approval to construct a 74-unit apartment complex on 3.78 acres (Project). The developable area (Project Area) is approximately 159,574 s.f. (3.64 acres) (excludes right-of-way dedication area and area of the identified stream from the gross Site area). A total of 66,438 S.F. of impervious area is proposed for the Site – which is less than 75 percent of total Site Area (123,620 S.F.). The remainder of the Project Area will consist of residential landscaping and other pervious surfaces. Per Section 5.2.1 of the 2009 King County Surface Water Design Manual (Manual), projects are required to mitigate for impervious surface by use of Flow Control Best Management Practices (BMP’s). The Project falls within the “Large Lot High Impervious” category, as the proposed impervious is approximately 40% of the total Site area and the total project area is larger than 22,000 SF. However, to meet the intent of the Manual, we have analyzed the impervious surface percentage based upon the developable area as approximately one acre of the site is encumbered by sensitive areas. With 1.53 acres of the 2.64 acres of developable area categorized as impervious (58%), it would be prudent to analyze the Project as “Large Lot High 2015 D. R. STRONG Consulting Engineers Inc. 2 Avana Ridge Technical Information Report Renton, Washington Impervious”. For projects that will result in an impervious surface coverage of more than 45% up to 65%, flow control BMPs must be applied to an impervious area equal to at least 20% of the Site area or 40% of the target impervious surface, whichever is less. Projects are required to first analyze the feasibility of dispersal and infiltration before choosing another method. The soils investigation summarized by the project geotechnical report are confined to the upper layers (up to 12 feet deep) of Site soils. That report indicates the presence of glacial till not conducive to infiltration. Further investigation may be conducted to assess infiltration capacity of deeper soils. Until further evaluation occurs, alternative BMPs must be considered. The presence of a stream and buffers provide an opportunity to fully disperse runoff from a portion of the Site. In other areas, rain gardens, Native Growth Retention Credit and dry wells are also possible Flow Control BMP’s that may be utilized. These options will be further analyzed at the time of engineering plan review. The Project is located within a Conservation Flow Control and Basic Water Quality Area. However due to the fact that the Project is a multifamily development, it shall be required to adhere to the Enhanced Water Quality Treatment criteria. Runoff will be collected and conveyed to a wet vault at the west end of the Site. The vault will be followed by a media filtration system to accommodate the Enhanced Water Quality Treatment requirements. Preliminary sizing is shown on the engineering plans and final sizing will be performed at the time of engineering plan review. 2015 D. R. STRONG Consulting Engineers Inc. 3 Avana Ridge Technical Information Report Renton, Washington NATURAL DRAINAGE SYSTEM FUNCTIONS: A portion of the Natural Resource Conservation Service (NRCS) soil survey of King County is included as Figure 4 and indicates the presence of Alderwood gravelly sandy loam with 8 to 15 percent slopes (AgC). Per the 2009 King County Surface Water Design Manual, this soil type is classified as “Till” material. The Natural Re Soil series descriptions follow Figure 4. The upstream basin area was evaluated by examining the King County topographic map, City of Renton Mapping Application and by conducting field reconnaissance on December 15, 2015 under overcast conditions. Upstream runoff enters the Site in two locations. Portions of SE 172nd St and 106th Ave SE direct upstream runoff across the northern property line. Runoff from 106th Ave SE and the north side of SE 172nd St. enters a Type 1 catch basin at the intersection of these two streets. An 18-inch diameter concrete pipe conveys runoff south under SE 172nd St. and outfalls onto the Site. Runoff from the southern portion of SE 172nd St is intercepted by a ditch along the south side of SE 172nd St. and enters the Site where the previously mentioned 18-inch diameter concrete pipe outlets. Upstream runoff from the west side of Benson Rd S flows west into a ditch along the east property line. This ditch conveys upstream runoff southwest along the east property line until it enters a stream about halfway down the property line. This stream conveys water through the Site. The Project proposes to construct a conveyance system to collect runoff from these two upstream tributary areas and bypass the infiltration facility on Site. 2015 D. R. STRONG Consulting Engineers Inc. 4 Avana Ridge Technical Information Report Renton, Washington FIGURE 1. TIR WORKSHEET King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Avana Ridge, LLC Phone: (425) 588-1147 Address: 9675 SE 36th Street, Suite 105 Mercer Island, WA 98040 Project Engineer: Toby Coenen, P.E. Company: D. R. STRONG Consulting Engineers Inc. Phone: (425) 827-3063 Project Name: Avana Ridge DDES Permit#: N/A Location: Township: 23 North Range: 05 East Section: 29 Site Address: 17249 Benson Road S 10615 SE 172nd Street Renton, Washington Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse Services Subdivision/ Short Subd. PUD Building Services M/F / Commercial / SFR Clearing and Grading Right-of-Way Other: DFW HPA Shoreline Management COE 404 Structural DOE Dam Safety Rockery/Vault/Wall FEMA Floodplain ESA Section 7 COE Wetlands Other: Part 5 PLAN AND REPORT INFORMATION Technical Information Report Drainage Review Type Full / Targeted / Large (circle one): Site Date (include revision December 29, 2015 dates): Date of Final: Site Improvement Plan (Engr. Plans) Type Full / Targeted / Small (circle one): Site Date (include revision December 29, 2015 dates): Date of Final: Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) _____________________________________________________________________________________ _____________________________________________________________________________________ ____________________________________________________________________________________ Date of Approval: 2015 D. R. STRONG Consulting Engineers Inc. 5 Avana Ridge Technical Information Report Renton, Washington Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes/ No Start Date: Completion Date Describe: __________________________ ___________________________________ ___________________________________ ___________________________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: Soos Creek Special District Overlays: N/A Drainage Basin: Black River, Panther Creek Sub-Basin Stormwater Requirements: Conservation Flow Control, Enhanced WQ Treatment Menu Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/ Stream Unnamed Type Ns stream Lake Wetlands: Closed Depression Floodplain Other Steep Slope Erosion Hazard Landslide Hazard Coal Mine Hazard (High) Seismic Hazard Habitat Protection Part 10 SOILS Soil Type _________AGC____ _________________ _________________ Slopes ________8-15%____ _________________ _________________ Erosion Potential Slight to Moderate _________________ _________________ High Groundwater Table (within 5 feet) Sole Source Aquifer other Low infiltration rate Seeps/Springs Additional Sheets Attached 2015 D. R. STRONG Consulting Engineers Inc. 6 Avana Ridge Technical Information Report Renton, Washington Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis Sensitive / Critical Area SEPA Other LIMITATION / SITE CONSTRAINT None Stream and associated buffers through Site T/B/D Additional Sheet attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: Site comprised of single, unnamed TDA (name or description) Core Requirements (all 8 apply) Discharge of Natural Location yes Number of Natural Discharge Locations: 2 Offsite Analysis Level: 1 / 2 / 3 dated: 12/15/2015 Flow Control Level: 1 / 2 / 3 or Exemption Number (incl. facility summary sheet Small Site BMPS N/A Conveyance System Spill containment located at: Detention facilities Erosion and Sediment Control ESC Site Supervisor: T/B/D Contact Phone: T/B/D After Hours Phone: T/B/D Maintenance and Operation Responsibility: Private / Public (Both) If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No Liability Water Quality Type: Basic / Sens Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. Landscape Management Plan: Yes / No Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared / None Requirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/A Source Control Describe Landuse: Multi Family (comm. / industrial landuse) Describe any structural controls: covered trash storage, Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? Other Drainage Structures Describe: N/A 2015 D. R. STRONG Consulting Engineers Inc. 7 Avana Ridge Technical Information Report Renton, Washington Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operations of Permanent Facilities Flag Limits of SAO and open space Preservation areas Other Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other Vault Dispersion, Dry well Biofiltration Wetpool Media Filtration Oil Control Spill Control Flow Control BMPs Other Wet vault Contech StormFilter See flow control Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other: Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other: 2015 D. R. STRONG Consulting Engineers Inc. 8 Avana Ridge Technical Information Report Renton, Washington Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. Signed/Date 2015 D. R. STRONG Consulting Engineers Inc. 9 Avana Ridge Technical Information Report Renton, Washington FIGURE 2. VICINITY MAP SITE 2015 D. R. STRONG Consulting Engineers Inc. 10 Avana Ridge Technical Information Report Renton, Washington FIGURE 3. DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS GRAPHIC SCALE 0 40 80 120 1 INCH = 80 FT. 2015 D. R. STRONG Consulting Engineers Inc. 11 Avana Ridge Technical Information Report Renton, Washington FIGURE 4. SOILS King County Area, Washington AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting • National map unit symbol: 2t626 • Elevation: 50 to 800 feet • Mean annual precipitation: 20 to 60 inches • Mean annual air temperature: 46 to 52 degrees F • Frost-free period: 160 to 240 days • Farmland classification: Prime farmland if irrigated Map Unit Composition • Alderwood and similar soils: 85 percent • Minor components: 15 percent • Estimates are based on observations, descriptions, and transects of the mapunit. SITE 2015 D. R. STRONG Consulting Engineers Inc. 12 Avana Ridge Technical Information Report Renton, Washington Description of Alderwood Setting • Landform: Ridges, hills • Landform position (two-dimensional): Shoulder • Landform position (three-dimensional): Nose slope, talf • Down-slope shape: Linear, convex • Across-slope shape: Convex • Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile • A - 0 to 7 inches: gravelly sandy loam • Bw1 - 7 to 21 inches: very gravelly sandy loam • Bw2 - 21 to 30 inches: very gravelly sandy loam • Bg - 30 to 35 inches: very gravelly sandy loam • 2Cd1 - 35 to 43 inches: very gravelly sandy loam • 2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities • Slope: 8 to 15 percent • Depth to restrictive feature: 20 to 39 inches to densic material • Natural drainage class: Moderately well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 18 to 37 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Very low (about 2.7 inches) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: B • Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA) Minor Components Everett • Percent of map unit: 5 percent • Landform: Eskers, kames, moraines • Landform position (two-dimensional): Shoulder, footslope • Landform position (three-dimensional): Crest, base slope • Down-slope shape: Convex • Across-slope shape: Convex Indianola • Percent of map unit: 5 percent • Landform: Eskers, kames, terraces • Landform position (three-dimensional): Tread • Down-slope shape: Linear • Across-slope shape: Linear 2015 D. R. STRONG Consulting Engineers Inc. 13 Avana Ridge Technical Information Report Renton, Washington Shalcar • Percent of map unit: 3 percent • Landform: Depressions • Landform position (three-dimensional): Dip • Down-slope shape: Concave • Across-slope shape: Concave Norma • Percent of map unit: 2 percent • Landform: Depressions, drainageways • Landform position (three-dimensional): Dip • Down-slope shape: Concave, linear • Across-slope shape: Concave 2015 D. R. STRONG Consulting Engineers Inc. 14 Avana Ridge Technical Information Report Renton, Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 – Discharge at the Natural Location: Runoff from the Site will discharge at the natural location. • C.R. #2 – Offsite Analysis: An Offsite Analysis is included in Section III. The Analysis describes the Site’s runoff patterns in detail. • C.R. #3 – Flow Control: The Project is located in a Conservation Flow Control Area and will therefore adhere to Level 2 Flow Control Standards, forested conditions. A combined detention/wet vault will provide flow control consistent with that standard. The Project is required to “match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the two-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 the 10-year return periods. Assum(ing) historic conditions as the predeveloped condition.” (KCSWDM, Sec. 1.2) Preliminary flow control calculations were conducted at this time. Final sizing will be completed at time of final engineering. • C.R. #4 – Conveyance System: New pipe systems and ditches/channels are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures and ditches/channels may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. The proposed conveyance system will be analyzed using the KCBW program to determine if the proposed conveyance system is capable of conveying the 100-year peak storm without overtopping any structures or channels. This analysis will be performed at time of construction plan preparation. • C.R. #5 – Erosion and Sediment Control: The Project provides the seven minimum ESC measures. A temporary erosion and sedimentation control plan will be prepared at time of construction plan preparation. • C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual will be included in Section X at the time of construction plan preparation. 2015 D. R. STRONG Consulting Engineers Inc. 15 Avana Ridge Technical Information Report Renton, Washington • C.R. #7 – Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. • C.R. #8 - The Project is located in the Enhanced Water Quality Treatment area. A combined detention/wet vault will be followed by a StormFilter media filtration system to meet water quality requirements. • S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 – Floodplain/Floodway Delineation: Not applicable for this Project. • S.R. #3 – Flood Protection Facilities: Not applicable for this Project. • S.R. #4 – Source Control: The project shall comply with the 2009 Stormwater Pollution Prevention Manual with such measures as cleaning of the storm drain system, prohibiting illicit connections to the storm drainage system and stenciling the site storm drains among other BMP’s. • S.R. #5 – Oil Control: Not applicable to this project. 2015 D. R. STRONG Consulting Engineers Inc. 16 Avana Ridge Technical Information Report Renton, Washington SECTION III OFF-SITE ANALYSIS A Level One Downstream Analysis was prepared by D.R. STRONG Consulting Engineers Inc. and is included in Appendix A. 2015 D. R. STRONG Consulting Engineers Inc. 17 Avana Ridge Technical Information Report Renton, Washington SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN The continuous simulation model, the King County Runoff Time Series, KCRTS, was used to analyze the pre and post developed runoff rates. Per Table 3.2.2.b of the Manual, the soil type is modeled as “Till” for the Alderwood gravelly sandy loam SCS classification as shown in Figure 4. Soils. Results of the KCRTS analysis are included in this section. EXISTING SITE HYDROLOGY Modeling input Hourly Time Series Predev.tsf Impervious 0.035 Till Grass 0.000 Pre-Developed Conditions 2.905 Till Forest 2.870 Wetland 0.000 Time Step: Scale Factor: 1.000 Rainfall Gage Seatac Total Area: Land cover Acres Data Type: Reduced Modeling results Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.186 2 2/09/01 18:00 0.245 1 100.00 0.990 0.054 7 1/05/02 16:00 0.186 2 25.00 0.960 0.143 4 2/28/03 3:00 0.145 3 10.00 0.900 0.009 8 8/26/04 2:00 0.143 4 5.00 0.800 0.085 6 1/05/05 8:00 0.125 5 3.00 0.667 0.145 3 1/18/06 20:00 0.085 6 2.00 0.500 0.125 5 11/24/06 4:00 0.054 7 1.30 0.231 0.245 1 1/09/08 9:00 0.009 8 1.10 0.091 Computed Peaks 0.225 50.00 0.980 2015 D. R. STRONG Consulting Engineers Inc. 18 Avana Ridge Technical Information Report Renton, Washington FIGURE 5. PREDEVELOPMENT AREA MAP GRAPHIC SCALE040801201 INCH = 80 FT. 2015 D. R. STRONG Consulting Engineers Inc. 19 Avana Ridge Technical Information Report Renton, Washington DEVELOPED SITE HYDROLOGY Soil type The soil types are unchanged from pre-developed conditions. Land covers KCRTS was used to model the developed peak runoff from the Site. The portions of the Site within the proposed clearing limits tributary to the proposed detention vault were modeled as “Till Grass” and Impervious as appropriate. Results of the KCRTS analysis are included in this section. Modeling input Time Step: Hourly Time Series Rdin.tsf Impervious 1.861 2.550 Till Grass 0.689 Wetland 0.000 Till Forest 0.000 Reduced Post-Developed Conditions Scale Factor: 1.000 Rainfall Gage Seatac Total Area: Land cover Acres Data Type: Modeling results Flow Frequency Analysis Time Series File:rdin.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.513 6 2/09/01 2:00 1.03 1 100.00 0.990 0.429 8 1/05/02 16:00 0.693 2 25.00 0.960 0.614 3 2/27/03 7:00 0.614 3 10.00 0.900 0.476 7 8/26/04 2:00 0.571 4 5.00 0.800 0.571 4 10/28/04 16:00 0.546 5 3.00 0.667 0.546 5 1/18/06 16:00 0.513 6 2.00 0.500 0.693 2 10/26/06 0:00 0.476 7 1.30 0.231 1.03 1 1/09/08 6:00 0.429 8 1.10 0.091 Computed Peaks 0.915 50.00 0.980 2015 D. R. STRONG Consulting Engineers Inc. 20 Avana Ridge Technical Information Report Renton, Washington BYPASS AREA HYDROLOGY Modeling input 0.355 Impervious 0.000 Data Type: Reduced Wetland 0.000 Till Grass 0.355 Bypass Area Time Step: Hourly Scale Factor: 1.000 Rainfall Gage Seatac Time Series Bypass.tsf Total Area: Till Forest 0.000 Land cover Acres Modeling results Flow Frequency Analysis Time Series File:bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.032 4 2/09/01 2:00 0.075 1 100.00 0.990 0.016 7 1/05/02 16:00 0.040 2 25.00 0.960 0.040 2 2/27/03 7:00 0.032 3 10.00 0.900 0.007 8 3/24/04 19:00 0.032 4 5.00 0.800 0.017 6 1/05/05 8:00 0.029 5 3.00 0.667 0.032 3 1/18/06 16:00 0.017 6 2.00 0.500 0.029 5 11/24/06 3:00 0.016 7 1.30 0.231 0.075 1 1/09/08 6:00 0.007 8 1.10 0.091 Computed Peaks 0.063 50.00 0.980 2015 D. R. STRONG Consulting Engineers Inc. 21 Avana Ridge Technical Information Report Renton, Washington FIGURE 6. POST DEVELOPMENT AREA MAP XX XGRAPHIC SCALE040801201 INCH = 80 FT. 2015 D. R. STRONG Consulting Engineers Inc. 22 Avana Ridge Technical Information Report Renton, Washington PERFORMANCE STANDARDS The Project is located in a Conservation Flow Control Area and will therefore adhere to Level 2 Flow Control Standards, forested conditions. A detention vault will provide flow control as required. The Project is required to “match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the two-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 the 10 year return periods. Assum(ing) historic conditions as the predeveloped condition.” (KCSWDM, Sec. 1.2). FLOW CONTROL SYSTEM Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 158.00 ft Facility Width: 30.00 ft Facility Area: 4740. sq. ft Effective Storage Depth: 8.00 ft Stage 0 Elevation: 352.00 ft Storage Volume: 37920. cu. ft Riser Head: 8.00 ft Riser Diameter: 18.00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.75 0.043 2 5.50 1.60 0.110 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 352.00 0. 0.000 0.000 0.00 0.01 352.01 47. 0.001 0.001 0.00 0.02 352.02 95. 0.002 0.002 0.00 0.03 352.03 142. 0.003 0.003 0.00 0.04 352.04 190. 0.004 0.003 0.00 0.05 352.05 237. 0.005 0.004 0.00 0.06 352.06 284. 0.007 0.004 0.00 0.20 352.20 948. 0.022 0.007 0.00 0.33 352.33 1564. 0.036 0.009 0.00 0.47 352.47 2228. 0.051 0.010 0.00 0.60 352.60 2844. 0.065 0.012 0.00 0.74 352.74 3508. 0.081 0.013 0.00 0.88 352.88 4171. 0.096 0.014 0.00 1.01 353.01 4787. 0.110 0.015 0.00 1.15 353.15 5451. 0.125 0.016 0.00 1.28 353.28 6067. 0.139 0.017 0.00 1.42 353.42 6731. 0.155 0.018 0.00 1.55 353.55 7347. 0.169 0.019 0.00 1.69 353.69 8011. 0.184 0.020 0.00 1.83 353.83 8674. 0.199 0.021 0.00 2015 D. R. STRONG Consulting Engineers Inc. 23 Avana Ridge Technical Information Report Renton, Washington 1.96 353.96 9290. 0.213 0.021 0.00 2.10 354.10 9954. 0.229 0.022 0.00 2.23 354.23 10570. 0.243 0.023 0.00 2.37 354.37 11234. 0.258 0.023 0.00 2.50 354.50 11850. 0.272 0.024 0.00 2.64 354.64 12514. 0.287 0.025 0.00 2.77 354.77 13130. 0.301 0.025 0.00 2.91 354.91 13793. 0.317 0.026 0.00 3.05 355.05 14457. 0.332 0.027 0.00 3.18 355.18 15073. 0.346 0.027 0.00 3.32 355.32 15737. 0.361 0.028 0.00 3.45 355.45 16353. 0.375 0.028 0.00 3.59 355.59 17017. 0.391 0.029 0.00 3.72 355.72 17633. 0.405 0.029 0.00 3.86 355.86 18296. 0.420 0.030 0.00 3.99 355.99 18913. 0.434 0.030 0.00 4.13 356.13 19576. 0.449 0.031 0.00 4.27 356.27 20240. 0.465 0.032 0.00 4.40 356.40 20856. 0.479 0.032 0.00 4.54 356.54 21520. 0.494 0.032 0.00 4.67 356.67 22136. 0.508 0.033 0.00 4.81 356.81 22799. 0.523 0.033 0.00 4.94 356.94 23416. 0.538 0.034 0.00 5.08 357.08 24079. 0.553 0.034 0.00 5.22 357.22 24743. 0.568 0.035 0.00 5.35 357.35 25359. 0.582 0.035 0.00 5.49 357.49 26023. 0.597 0.036 0.00 5.50 357.50 26070. 0.598 0.036 0.00 5.52 357.52 26165. 0.601 0.036 0.00 5.53 357.53 26212. 0.602 0.038 0.00 5.55 357.55 26307. 0.604 0.041 0.00 5.57 357.57 26402. 0.606 0.044 0.00 5.58 357.58 26449. 0.607 0.049 0.00 5.60 357.60 26544. 0.609 0.055 0.00 5.62 357.62 26639. 0.612 0.060 0.00 5.63 357.63 26686. 0.613 0.062 0.00 5.77 357.77 27350. 0.628 0.073 0.00 5.90 357.90 27966. 0.642 0.081 0.00 6.04 358.04 28630. 0.657 0.089 0.00 6.18 358.18 29293. 0.672 0.095 0.00 6.31 358.31 29909. 0.687 0.101 0.00 6.45 358.45 30573. 0.702 0.106 0.00 6.58 358.58 31189. 0.716 0.111 0.00 6.72 358.72 31853. 0.731 0.116 0.00 6.85 358.85 32469. 0.745 0.121 0.00 6.99 358.99 33133. 0.761 0.125 0.00 7.12 359.12 33749. 0.775 0.129 0.00 7.26 359.26 34412. 0.790 0.133 0.00 7.40 359.40 35076. 0.805 0.137 0.00 7.53 359.53 35692. 0.819 0.141 0.00 7.67 359.67 36356. 0.835 0.144 0.00 7.80 359.80 36972. 0.849 0.148 0.00 7.94 359.94 37636. 0.864 0.151 0.00 8.00 360.00 37920. 0.871 0.153 0.00 8.10 360.10 38394. 0.881 0.617 0.00 8.20 360.20 38868. 0.892 1.460 0.00 2015 D. 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STRONG Consulting Engineers Inc. 24 Avana Ridge Technical Information Report Renton, Washington 8.30 360.30 39342. 0.903 2.560 0.00 8.40 360.40 39816. 0.914 3.860 0.00 8.50 360.50 40290. 0.925 5.330 0.00 8.60 360.60 40764. 0.936 6.760 0.00 8.70 360.70 41238. 0.947 7.290 0.00 8.80 360.80 41712. 0.958 7.780 0.00 8.90 360.90 42186. 0.968 8.250 0.00 9.00 361.00 42660. 0.979 8.690 0.00 9.10 361.10 43134. 0.990 9.100 0.00 9.20 361.20 43608. 1.001 9.500 0.00 9.30 361.30 44082. 1.012 9.880 0.00 9.40 361.40 44556. 1.023 10.250 0.00 9.50 361.50 45030. 1.034 10.610 0.00 9.60 361.60 45504. 1.045 10.950 0.00 9.70 361.70 45978. 1.056 11.280 0.00 9.80 361.80 46452. 1.066 11.610 0.00 9.90 361.90 46926. 1.077 11.920 0.00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 1.03 0.30 8.03 360.03 38073. 0.874 2 0.51 0.15 7.72 359.72 36616. 0.841 3 0.61 0.13 7.04 359.04 33377. 0.766 4 0.69 0.11 6.60 358.60 31304. 0.719 5 0.55 0.04 5.43 357.43 25738. 0.591 6 0.37 0.03 4.73 356.73 22443. 0.515 7 0.43 0.03 4.70 356.70 22287. 0.512 8 0.48 0.03 3.13 355.13 14830. 0.340 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.30 0.08 ******** ******* 0.33 2 0.15 0.03 ******** 0.19 0.17 3 0.13 0.04 ******** ******* 0.14 4 0.11 0.03 ******** ******* 0.13 5 0.04 0.03 ******** ******* 0.06 6 0.03 0.02 ******** ******* 0.05 7 0.03 0.02 ******** ******* 0.04 8 0.03 0.01 ******** ******* 0.03 ---------------------------------- Route Time Series through Facility Inflow Time Series File:rdin.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 1.03 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.303 CFS at 11:00 on Jan 9 in Year 8 Peak Reservoir Stage: 8.03 Ft Peak Reservoir Elev: 360.03 Ft Peak Reservoir Storage: 38073. Cu-Ft : 0.874 Ac-Ft Add Time Series:bypass.tsf Peak Summed Discharge: 0.326 CFS at 11:00 on Jan 9 in Year 8 2015 D. R. STRONG Consulting Engineers Inc. 25 Avana Ridge Technical Information Report Renton, Washington Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.146 2 2/09/01 20:00 0.303 8.03 1 100.00 0.990 0.033 7 1/07/02 4:00 0.146 7.73 2 25.00 0.960 0.127 3 3/06/03 22:00 0.127 7.04 3 10.00 0.900 0.027 8 8/26/04 8:00 0.112 6.60 4 5.00 0.800 0.033 6 1/08/05 5:00 0.036 5.43 5 3.00 0.667 0.036 5 1/19/06 5:00 0.033 4.74 6 2.00 0.500 0.112 4 11/24/06 8:00 0.033 4.70 7 1.30 0.231 0.303 1 1/09/08 11:00 0.027 3.13 8 1.10 0.091 Computed Peaks 0.251 8.02 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.170 2 2/09/01 20:00 0.326 1 100.00 0.990 0.044 7 1/05/02 16:00 0.170 2 25.00 0.960 0.144 3 3/06/03 22:00 0.144 3 10.00 0.900 0.031 8 8/26/04 2:00 0.132 4 5.00 0.800 0.046 6 1/05/05 8:00 0.062 5 3.00 0.667 0.062 5 1/18/06 16:00 0.046 6 2.00 0.500 0.132 4 11/24/06 7:00 0.044 7 1.30 0.231 0.326 1 1/09/08 11:00 0.031 8 1.10 0.091 Computed Peaks 0.274 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 27332 44.573 44.573 55.427 0.554E+00 0.006 6675 10.886 55.458 44.542 0.445E+00 0.010 7340 11.970 67.428 32.572 0.326E+00 0.014 5847 9.535 76.963 23.037 0.230E+00 0.018 4961 8.090 85.054 14.946 0.149E+00 0.023 3595 5.863 90.917 9.083 0.908E-01 0.027 2060 3.359 94.276 5.724 0.572E-01 0.031 2038 3.324 97.599 2.401 0.240E-01 0.035 1022 1.667 99.266 0.734 0.734E-02 0.039 232 0.378 99.644 0.356 0.356E-02 0.043 12 0.020 99.664 0.336 0.336E-02 0.047 5 0.008 99.672 0.328 0.328E-02 0.051 5 0.008 99.680 0.320 0.320E-02 0.055 7 0.011 99.692 0.308 0.308E-02 0.059 7 0.011 99.703 0.297 0.297E-02 0.063 10 0.016 99.720 0.280 0.280E-02 0.067 17 0.028 99.747 0.253 0.253E-02 0.072 23 0.038 99.785 0.215 0.215E-02 0.076 10 0.016 99.801 0.199 0.199E-02 2015 D. 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STRONG Consulting Engineers Inc. 26 Avana Ridge Technical Information Report Renton, Washington 0.080 11 0.018 99.819 0.181 0.181E-02 0.084 6 0.010 99.829 0.171 0.171E-02 0.088 5 0.008 99.837 0.163 0.163E-02 0.092 7 0.011 99.848 0.152 0.152E-02 0.096 9 0.015 99.863 0.137 0.137E-02 0.100 8 0.013 99.876 0.124 0.124E-02 0.104 11 0.018 99.894 0.106 0.106E-02 0.108 7 0.011 99.905 0.095 0.946E-03 0.112 11 0.018 99.923 0.077 0.766E-03 0.116 7 0.011 99.935 0.065 0.652E-03 0.120 9 0.015 99.949 0.051 0.506E-03 0.125 10 0.016 99.966 0.034 0.342E-03 0.129 5 0.008 99.974 0.026 0.261E-03 0.133 3 0.005 99.979 0.021 0.212E-03 0.137 3 0.005 99.984 0.016 0.163E-03 0.141 3 0.005 99.989 0.011 0.114E-03 0.145 5 0.008 99.997 0.003 0.326E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 27637 45.070 45.070 54.930 0.549E+00 0.007 7531 12.281 57.352 42.648 0.426E+00 0.012 7290 11.888 69.240 30.760 0.308E+00 0.017 6628 10.809 80.049 19.951 0.200E+00 0.021 4370 7.127 87.175 12.825 0.128E+00 0.026 3365 5.488 92.663 7.337 0.734E-01 0.031 1978 3.226 95.889 4.111 0.411E-01 0.036 1259 2.053 97.942 2.058 0.206E-01 0.041 738 1.204 99.145 0.855 0.855E-02 0.045 229 0.373 99.519 0.481 0.481E-02 0.050 44 0.072 99.591 0.409 0.409E-02 0.055 38 0.062 99.653 0.347 0.347E-02 0.060 8 0.013 99.666 0.334 0.334E-02 0.064 16 0.026 99.692 0.308 0.308E-02 0.069 12 0.020 99.711 0.289 0.289E-02 0.074 15 0.024 99.736 0.264 0.264E-02 0.079 14 0.023 99.759 0.241 0.241E-02 0.083 17 0.028 99.786 0.214 0.214E-02 0.088 8 0.013 99.799 0.201 0.201E-02 0.093 12 0.020 99.819 0.181 0.181E-02 0.098 7 0.011 99.830 0.170 0.170E-02 0.102 7 0.011 99.842 0.158 0.158E-02 0.107 8 0.013 99.855 0.145 0.145E-02 0.112 6 0.010 99.865 0.135 0.135E-02 0.117 10 0.016 99.881 0.119 0.119E-02 0.122 10 0.016 99.897 0.103 0.103E-02 0.126 6 0.010 99.907 0.093 0.930E-03 0.131 11 0.018 99.925 0.075 0.750E-03 0.136 10 0.016 99.941 0.059 0.587E-03 0.141 10 0.016 99.958 0.042 0.424E-03 0.145 8 0.013 99.971 0.029 0.294E-03 0.150 2 0.003 99.974 0.026 0.261E-03 0.155 3 0.005 99.979 0.021 0.212E-03 0.160 4 0.007 99.985 0.015 0.147E-03 0.164 3 0.005 99.990 0.010 0.978E-04 2015 D. 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STRONG Consulting Engineers Inc. 27 Avana Ridge Technical Information Report Renton, Washington 0.169 3 0.005 99.995 0.005 0.489E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.043 | 0.88E-02 0.64E-02 -27.2 | 0.88E-02 0.043 0.040 -5.2 0.054 | 0.61E-02 0.36E-02 -40.9 | 0.61E-02 0.054 0.043 -20.2 0.065 | 0.47E-02 0.31E-02 -34.6 | 0.47E-02 0.065 0.046 -29.5 0.076 | 0.36E-02 0.26E-02 -29.0 | 0.36E-02 0.076 0.054 -29.2 0.087 | 0.27E-02 0.20E-02 -25.1 | 0.27E-02 0.087 0.073 -15.9 0.098 | 0.21E-02 0.17E-02 -17.5 | 0.21E-02 0.098 0.086 -11.7 0.109 | 0.14E-02 0.14E-02 2.4 | 0.14E-02 0.109 0.111 1.9 0.120 | 0.99E-03 0.11E-02 8.2 | 0.99E-03 0.120 0.122 2.2 0.131 | 0.60E-03 0.75E-03 24.3 | 0.60E-03 0.131 0.135 3.4 0.142 | 0.34E-03 0.39E-03 14.3 | 0.34E-03 0.142 0.143 0.5 0.153 | 0.20E-03 0.24E-03 25.0 | 0.20E-03 0.153 0.159 3.6 0.164 | 0.15E-03 0.98E-04 -33.3 | 0.15E-03 0.164 0.161 -1.7 0.175 | 0.82E-04 0.00E+00 -100.0 | 0.82E-04 0.175 0.167 -4.7 0.186 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.186 0.170 -8.7 Maximum positive excursion = 0.006 cfs ( 5.2%) occurring at 0.121 cfs on the Base Data:predev.tsf and at 0.127 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.020 cfs (-29.9%) occurring at 0.067 cfs on the Base Data:predev.tsf and at 0.047 cfs on the New Data:dsout.tsf Water Quality Treatment The Project is located in the Enhanced Water Quality Treatment area. A wet vault followed by a media filtration system will be utilized. Rainfall (R) of the mean annual storm =0.52 in. From KCSWDM Fig. 6.4.1.A Area of impervious surface (Ai) =81,054 s.f. Area of till soil covered with till grass (Atg) =30,026 s.f. Area of till soil covered with till forest (Atf) =0 s.f. Area of outwash soil covered with grass or forest (Ao) =0 s.f. Volume factor (f) =3 N/A From KCSWDM Sec. 6.4.1.1 Calculations Units Notes Volume of runoff from mean annual storm (Vr) =3486 c.f. =(0.9Ai + 0.25Atg + 0.10Atf + 0.01Ao) * R/12 Minimum Wetpool volume required (Vb) =10,459 c.f. =f * Vr A 72” Stormfilter manhole will be installed downstream of the detention facility with 6 ZPG cartridges. 2015 D. R. STRONG Consulting Engineers Inc. 28 Avana Ridge Technical Information Report Renton, Washington FIGURE 7. DETENTION & WATER QUALITY FACILITY DETAILS To be completed at time of final engineering 2015 D. R. STRONG Consulting Engineers Inc. 29 Avana Ridge Technical Information Report Renton, Washington SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per Core Requirement, #4 of the KCSWDM, the conveyance system must be analyzed and designed for existing tributary and developed onsite runoff from the proposed project. Pipe systems shall be designed to convey the 100-year design storm. The Rational Method will be used to calculate the Q-Ratio for each pipe node. A conveyance system consisting primarily of pipes and catch basins will be designed for the Project. Onsite runoff from PGIS will be collected by the multiple catch basins. Pipes are typically twelve-inch diameter LCPE material. A backwater analysis will be provided at time of final engineering. 2015 D. R. STRONG Consulting Engineers Inc. 30 Avana Ridge Technical Information Report Renton, Washington SECTION VI SPECIAL REPORTS AND STUDIES A number of reports have been prepared for the project as well as an earlier development proposal (Springbrook Ridge) on this parcel. These include: • Geological Engineering Services, Coal Mine Hazard Assessment, Cugini Property; Icicle Creek Engineers, Inc.; June 24, 1999. • Geological Engineering Services, Coal Mine Hazard Assessment, Cugini Property – Northwest Parcel; Icicle Creek Engineers, Inc.; March 22, 2004. • Geological Engineering Services, Proposed Property Development, Springbrook Ridge; Icicle Creek Engineers, Inc.; January 26, 2009. • Cugini Property wetland and stream delineation study – TWC Ref# 080109, The Watershed Company, January 25, 2009. • Environmental Checklist, Springbrook Ridge PUD; Century Pacific, LP; February 4, 2009. • Geotechnical Engineering Study – Avana Ridge Apartments; Earth Solutions NW, LLC; December 21, 2015. • Tree Inspection, Avana Ridge PPUD, Parcel Numbers 292305-9148, -9009, Renton, WA; Greenforest Incorporated; December 16, 2015 • Wetland and Supplemental Stream Study – Avana Ridge PUD; Sewall Wetland Consulting, Inc.; December 22, 2015. • Habitat Data Report – Avana Ridge; Sewall Wetland Consulting, Inc.; December 22, 2015. • Avana Ridge Apartments, Traffic Impact Analysis; TraffEx; December 21, 2015. 2015 D. R. STRONG Consulting Engineers Inc. 31 Avana Ridge Technical Information Report Renton, Washington SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS No other permits have been required as part of this development, as of the date of this report. 2015 D. R. STRONG Consulting Engineers Inc. 32 Avana Ridge Technical Information Report Renton, Washington SECTION VIII ESC AND CSWPPP ANALYSIS AND DESIGN The Erosion and Sedimentation Control Design meets the seven minimum King County requirements: 1. Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Site disturbed areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. A stabilized construction entrance will be located at the point of ingress/egress (i.e. onsite access road). 5. A sediment pond will be utilized for sediment retention (see calculations below). Perimeter silt fences will provide sediment retention within the bypass areas. 6. Surface water from disturbed areas will sheet flow to the sediment pond for treatment. 7. Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. The complete CSWPPP will be completed and submitted at time of final engineering. 2015 D. R. STRONG Consulting Engineers Inc. 33 Avana Ridge Technical Information Report Renton, Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – will be submitted at time of final engineering. 2. Facility Summary – will be submitted at time of final engineering. 2015 D. R. STRONG Consulting Engineers Inc. 34 Avana Ridge Technical Information Report Renton, Washington STORMWATER FACILITY SUMMARY SHEET Number 1 (Detention Vault) (provide one Stormwater Facility Summary Sheet per Natural Discharge Location) Overview: Avana Ridge December 29, 2015 Project Name Date Downstream Drainage Basins Black River Panther Creek Major Basin Name Minor Basin Name Flow Control: Detention Vault Private Parking Lot Flow Control Facility Name/Number Facility Location If none, Flow control provided in regional/shared facility (give location) N/A No flow control required Exemption number General Facility Information: Type/Number of detention facilities Type/Number of infiltration facilities: Ponds Ponds 1 Vaults Tanks Tanks Trenches Control Structure Location Located inside proposed vault Type of Control Structure FROP-T Number of Orifices/Restrictions 2 Size of Orifice/Restriction: No. 1 0.75” No. 2 1.60” No. 3 No. 4 Flow Control Performance Standard: Level 2 Live Storage Volume 37,920 cf Depth 8 feet Volume Factor of Safety 1.0 Number of Acres Served 2.55 Number of Lots N/A Dam Safety Regulations (Washington State Department of Ecology) Reservoir Volume above natural grade N/A Depth of Reservoir above natural grade N/A Facility Summary Sheet Sketch All detention, infiltration and water quality facilities must include a detailed sketch. 2015 D. R. STRONG Consulting Engineers Inc. 35 Avana Ridge Technical Information Report Renton, Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL To be completed at time of final engineering 2015 D. R. STRONG Consulting Engineers Inc. 36 Avana Ridge Technical Information Report Renton, Washington APPENDIX A ____________________________________________________________________________ LEVEL ONE DOWNSTREAM ANALYSIS AVANA RIDGE 17249 Benson Road S and 10615 SE 172nd Street Renton, Washington ____________________________________________________________________________ DRS Project No. 15088 City Of Renton File No. XXXX Owner/Applicant Avana Ridge, LLC 9675 SE 36th Street, Suite 105 Mercer Island, Washington 98040 Report Prepared by D. R. STRONG Consulting Engineers, Inc. 620 7th Avenue Kirkland, WA 98033 (425) 827-3063 Report Issue Date December 28, 2015  2015 D. R. STRONG Consulting Engineers Inc. Avana Ridge Level One Downstream Analysis Renton, Washington AVANA RIDGE LEVEL ONE DOWNSTREAM ANALYSIS DISCLAIMER: ........................................................................................................................... 1 TASK 1: DEFINE AND MAP STUDY AREA ........................................................................ 1 TASK 2: RESOURCE REVIEW ............................................................................................. 1 FIGURE 1. Vicinity Map................................................................................. 2 FIGURE 2: Site Map ....................................................................................... 3 FIGURE 3. King County iMap Topography .............................................. 4 FIGURE 4. King County Sensitive Area Map .......................................... 5 FIGURE 5. City of Renton Erosion Hazards Map ................................... 6 FIGURE 6. City of Renton Landslide Hazards Map ............................... 7 FIGURE 7. City of Renton Coal Mine Hazards Map ............................... 8 FIGURE 8. City of Renton Steep Slopes .................................................. 9 FIGURE 9. City of Renton Flood Hazard ................................................ 10 FIGURE 10. City of Renton Seismic Hazards ....................................... 11 FIGURE 11. City of Renton Liquefaction Hazards ............................... 12 FIGURE 12. City of Renton Aquifer Protection Zones........................ 13 FIGURE 13. USDA King County Soils Survey Map ............................. 14 FIGURE 14. FEMA Map ............................................................................... 17 TASK 3: FIELD INSPECTION ............................................................................................. 18 Upstream Tributary Area ........................................................................................... 18 General Onsite and Offsite Drainage Description ................................................ 18 TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS ........................................................................................................ 18 Drainage System Description ................................................................................... 18 TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS .......................... 20 APPENDIX A. OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE & DOWNSTREAM MAP ............................................................................................... 21  2015 D. R. STRONG Consulting Engineers Inc 1 Avana Ridge Level One Downstream Analysis Renton, Washington LEVEL ONE DOWNSTREAM ANALYSIS DISCLAIMER: THIS REPORT WAS PREPARED AT THE REQUEST OF PNW HOLDINGS, LLC FOR THE 3.78 ACRE PARCELS KNOWN AS A PORTION OF THE SOUTHEAST QUARTER OF SECTION 29, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, TAX PARCEL NUMBERS 292305900 AND 292309148 (SITE). D. R. STRONG CONSULTING ENGINEERS INC. (DRS) HAS PREPARED THIS REPORT FOR THE EXCLUSIVE USE OF DRS, THE OWNER, AND THEIR AGENTS, FOR SPECIFIC APPLICATION TO THE DEVELOPMENT PROJECT AS DESCRIBED HEREIN. USE OR RELIANCE ON THIS REPORT, OR ANY OF ITS CONTENTS FOR ANY REVISIONS OF THIS PROJECT, OR ANY OTHER PROJECT, OR BY OTHERS NOT DESCRIBED ABOVE, IS FORBIDDEN WITHOUT THE EXPRESSED PERMISSION BY DRS. TASK 1: DEFINE AND MAP STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2009 King County Surface Water Design Manual and Section 2.3 of the 2010 City of Renton Amendments to the King County Surface Water Design Manual (Manual). The Site is located at 17249 Benson Road S and 10615 SE 172nd Street Renton, Washington. The Project is the development of two parcels into a 74 unit apartment complex. See Figures 1, 2 and 3 for maps of the study area. TASK 2: RESOURCE REVIEW  Adopted Basin Plans: None at this time  Finalized Drainage Studies: None available  Basin Reconnaissance Summary Reports: The Green-Duwamish and Puget Sound Water Resource Inventory Area 9 Habitat Limiting Factors And Reconnaissance Assessment Report is available for the Basin.  Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 14  Other Offsite Analysis Reports: Technical Information Report (TIR) for Fieldbrook Commons, dated December 2nd, 2013 by D.R. Strong Consulting Engineers  Sensitive Areas Map: See Figures 4-12  DNRP Drainage Complaints and Studies: Per King County Water and Land Resources Division, there are no complaints within the downstream path, 1 mile from the Site within the last 10 years.  USDA King County Soils Survey: See Figure 13  Wetlands Inventory: Vol. 2 East (1990) – The wetland inventory revealed no additional wetlands within one mile along the downstream path, see Appendix C.  Migrating River Studies: None Applicable  King County Designated Water Quality Problems: None at this time  2015 D. R. STRONG Consulting Engineers Inc 2 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 1 - Vicinity Map SITE  2015 D. R. STRONG Consulting Engineers Inc 3 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 2 - Site Map GRAPHIC SCALE 0 40 80 120 1 INCH = 80 FT.  2015 D. R. STRONG Consulting Engineers Inc 4 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 3 - King County iMap Topography SITE  2015 D. R. STRONG Consulting Engineers Inc 5 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 4 - King County Sensitive Area Map SITE  2015 D. R. STRONG Consulting Engineers Inc 6 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 5 - City of Renton Erosion Hazards Map NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 7 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 6 - City of Renton Landslide Hazards Map NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 8 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 7 - City of Renton Coal Mine Hazards Map NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 9 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 8 - City of Renton Steep Slopes NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 10 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 9 - City of Renton Flood Hazard NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 11 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 10 - City of Renton Seismic Hazards NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 12 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 11 - City of Renton Liquefaction Hazards NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 13 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 12 - City of Renton Aquifer Protection Zones NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 14 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 13 - USDA King County Soils Survey Map King County Area, Washington AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes Map Unit Setting  National map unit symbol: 2t626  Elevation: 50 to 800 feet  Mean annual precipitation: 20 to 60 inches  Mean annual air temperature: 46 to 52 degrees F  Frost-free period: 160 to 240 days  Farmland classification: Prime farmland if irrigated Map Unit Composition  Alderwood and similar soils: 85 percent  Minor components: 15 percent  Estimates are based on observations, descriptions, and transects of the mapunit. Description of Alderwood SITE  2015 D. R. STRONG Consulting Engineers Inc 15 Avana Ridge Level One Downstream Analysis Renton, Washington Setting  Landform: Ridges, hills  Landform position (two-dimensional): Shoulder  Landform position (three-dimensional): Nose slope, talf  Down-slope shape: Linear, convex  Across-slope shape: Convex  Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits Typical profile  A - 0 to 7 inches: gravelly sandy loam  Bw1 - 7 to 21 inches: very gravelly sandy loam  Bw2 - 21 to 30 inches: very gravelly sandy loam  Bg - 30 to 35 inches: very gravelly sandy loam  2Cd1 - 35 to 43 inches: very gravelly sandy loam  2Cd2 - 43 to 59 inches: very gravelly sandy loam Properties and qualities  Slope: 8 to 15 percent  Depth to restrictive feature: 20 to 39 inches to densic material  Natural drainage class: Moderately well drained  Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr)  Depth to water table: About 18 to 37 inches  Frequency of flooding: None  Frequency of ponding: None  Available water storage in profile: Very low (about 2.7 inches) Interpretive groups  Land capability classification (irrigated): None specified  Land capability classification (nonirrigated): 4s  Hydrologic Soil Group: B  Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA) Minor Components Everett  Percent of map unit: 5 percent  Landform: Eskers, kames, moraines  Landform position (two-dimensional): Shoulder, footslope  Landform position (three-dimensional): Crest, base slope  Down-slope shape: Convex  Across-slope shape: Convex Indianola  Percent of map unit: 5 percent  Landform: Eskers, kames, terraces  Landform position (three-dimensional): Tread  Down-slope shape: Linear  Across-slope shape: Linear Shalcar  2015 D. R. STRONG Consulting Engineers Inc 16 Avana Ridge Level One Downstream Analysis Renton, Washington  Percent of map unit: 3 percent  Landform: Depressions  Landform position (three-dimensional): Dip  Down-slope shape: Concave  Across-slope shape: Concave Norma  Percent of map unit: 2 percent  Landform: Depressions, drainageways  Landform position (three-dimensional): Dip  Down-slope shape: Concave, linear  Across-slope shape: Concave  2015 D. R. STRONG Consulting Engineers Inc 17 Avana Ridge Level One Downstream Analysis Renton, Washington FIGURE 14 - FEMA Map NTS SITE  2015 D. R. STRONG Consulting Engineers Inc 18 Avana Ridge Level One Downstream Analysis Renton, Washington TASK 3: FIELD INSPECTION Upstream Tributary Area The upstream basin area was evaluated by examining the King County topographic map (see Figure 3), City of Renton Mapping Application and by conducting field reconnaissance on December 15, 2015 under overcast conditions. Upstream runoff enters the Site in two locations. Portions of SE 172nd St and 106th Ave SE direct upstream runoff across the northern property line. Runoff from 106th Ave SE and the north side of SE 172nd St. enters a Type 1 catch basin at the intersection of these two streets. An 18-inch diameter concrete pipe conveys runoff south under SE 172nd St. and outfalls onto the Site. Runoff from the southern portion of SE 172nd St is intercepted by a ditch along the south side of SE 172nd St. and enters the Site where the previously mentioned 18-inch diameter concrete pipe outlets. Upstream runoff from the west side of Benson Rd S flows west into a ditch along the east property line. This ditch conveys upstream runoff southwest along the east property line until it enters a stream about halfway down the property line. This stream conveys water through the Site. The Project proposes to construct a conveyance system to collect runoff from these two upstream tributary areas and bypass the infiltration facility on Site. General Onsite and Offsite Drainage Description The Site is contained within one Threshold Discharge Area (TDA) but is divided into two distinct Natural Discharge Areas (NDA’s), NDA 1 and NDA 2. See Downstream Analysis Map for the location of each NDA. Natural Discharge Point 1 (NDP 1) is located at approximately the midpoint of the southwestern property line. NDP 2 is northwest of NDP 1. See Appendix A for a map of the NDAs and downstream paths. Runoff exits the Site via an onsite ditch from both NDAs. NDA 1 is approximately 2.65 acres (115,449 SF) and NDA 2 is approximately 1.13 acres (49,378 SF). The flow paths were observed and appear to converge at points D1 and C2. TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS Drainage System Description The downstream area was evaluated by reviewing available resources and by conducting a field reconnaissance on December 15, 2015 under overcast conditions. The analysis is illustrated and detailed in the Downstream Map and Downstream Table located in Appendix A. The downstream path is located within the Black River Drainage Basin; more specifically the Panther Creek Subbasin. For point-to-point descriptions of downstream flow, see Appendix A. Runoff exits the Site via channel flow from an onsite ditch in two locations – NDP 1 and NDP 2. Both NDPs are located along the western property line. Runoff enters box culverts on the northeast side of SR 515, eventually crossing under the road to the southwest. Flows from each NDA converge at a Type 2 catch basin on the southwest side of SR 515, just east of parcel  2015 D. R. STRONG Consulting Engineers Inc 19 Avana Ridge Level One Downstream Analysis Renton, Washington 2923059150. Runoff continues west through a ditch between parcels 2923059150 and 2923059134 and is conveyed west through a series of catch basins and PVC pipes. Runoff outlets west of Wells Ave S and continues west, eventually outfalling into Panther Creek. A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow paths revealed no complaints within the last ten years along all downstream paths for the Site.  2015 D. R. STRONG Consulting Engineers Inc 20 Avana Ridge Level One Downstream Analysis Renton, Washington TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS No drainage complaints were found in Task 4, and therefore no mitigation is required by this Project. All potential maintenance issues should be resolved by either City Maintenance (public systems) or the respective property owners (private systems). No further analysis should be required of this Project. The Project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. Project runoff will be collected and released per the Manual’s requirements to accommodate Flow Control Duration Standard – Matching Forested Site Conditions (Level 2 Flow Control). The Project is located within a Basic Water Quality Area, but since the Project is a multifamily development, it will adhere to Enhanced Basic Water Quality requirements. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction.  2015 D. R. STRONG Consulting Engineers Inc. 21 Avana Ridge Level One Downstream Analysis Renton, Washington APPENDIX A. OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE & DOWNSTREAM MAP OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 TDA 1: NDA 1 Basin: Black River Subbasin Name: Panther Creek Subbasin Number: N/A 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 % 1/4 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. A1 2’ x 4’ Concrete Box Culvert Northeast side of SR 515, approximate midpoint of western property line. 0’ None Observed Slight potential for blockage from debris/foliage Light flow observed A1-B1 Southwesterly Pipe Flow 18” Concrete Pipe 0’-19’ None Observed None Anticipated B1 Type 2 Catch Basin Slightly southwest of box culvert on the northeast side of SR 515. 18” Conc. (NE,SW) 19’ None Observed None Anticipated Light flow observed B1-C1 Southwesterly Pipe Flow 18” Concrete Pipe, travels southwest under SR515 19’-74’ None Observed None Anticipated C1 Type 2 Catch Basin On the southwest side of SR 515, across the street from CB at point B1. 12” Conc. (SE), 18” Conc. (NE, NW) 74’ None Observed None Anticipated Light flow observed C1-D1 Northwesterly Pipe Flow 18” Concrete Pipe, travels northwest along the southwestern side of SR 515. 74’-358’ None Observed None Anticipated D1 Type 2 Catch Basin Southwestern side of SR 515, just east of parcel 2923059150. 18” Conc. (NE,SE), 24” Conc. (SW) 358’ None Observed None Anticipated Moderate flow observed D1-E1 Southwesterly Pipe Flow 24” Concrete Pipe, travels southwest under the sidewalk and outfalls into ditch. 358’-378’ None Observed None Anticipated  2015 D. R. STRONG Consulting Engineers Inc. 22 Avana Ridge Level One Downstream Analysis Renton, Washington E1 Pipe Outlet 24” Concrete Pipe outfalls into ditch on the southwest side of SR 515, heading southwest between parcels 2923059150 and 2923059134 378’ None Observed None Anticipated Moderate flow observed E1-F1 Channel Flow Runoff flows southwesterly between the parcels through a moderately vegetated ditch, approximately 2’ wide 378’-791’ None Observed General maintenance and clearing may be necessary in the future F1 Culvert Inlet Runoff flows into 30” CMP with trash rack. Flow is separated from the sidewalk by a ~2’ high concrete wall and chainlink fence. Inlet is custom designed and transitions from 30” to 18” pipe. 791’ None Observed Heavy flow may erode subgrade of wooden fence near inlet and cause problems Moderate flow observed F1-G1 Southwesterly Pipe Flow 18” PVC Pipe 791’-856’ None Observed None Anticipated G1 Type 1 Catch Basin South side of S 36th St. 18” (NE, SE, W) 856’ None Observed None Anticipated Moderate flow observed G1-H1 Westerly Pipe Flow 18” PVC Pipe 856’-954’ None Observed None Anticipated H1 Type 2 Catch Basin Solid lid in south side of S 36th St. 18” PVC (E, NW) 954’ None Observed None Anticipated Moderate flow observed H1-I1 Northwesterly Pipe Flow 18” PVC Pipe 954’-1127’ None Observed None Anticipated I1 Type 2 Catch Basin Solid lid in south side of S 36th St. 18” PVC (SE, W) 1127’’ None Observed None Anticipated Moderate flow observed I1-J1 Westerly Pipe Flow 18” PVC Pipe 1127’-1264’ None Observed None Anticipated J1 Type 2 Catch Basin Solid lid in south side of S 36th St. 18” PVC (E, SW) 1264’ None Observed None Anticipated Moderate flow observed J1-K1 Southwesterly Pipe Flow 18” PVC Pipe 1264’-1377’ None Observed None Anticipated  2015 D. R. STRONG Consulting Engineers Inc. 23 Avana Ridge Level One Downstream Analysis Renton, Washington K1 Type 2 Catch Basin Solid lid in south side of S 36th St. 18” PVC (NE, S). Over ¼ mile downstream - end of field reconnaissance. Runoff continues south between parcels 1441000150 and 1441000160. According to record drawings from the City of Renton, flow enters a CB at the back of parcel 1441000150, moves to another CB at the back of parcel 8106300980, and then moves west towards a CB at the front of parcel 8106300890, 1866’ along the downstream path. This Type 2 CB was observed during field reconnaissance. Moderate flow was observed. 18” pipe (E,W). Runoff outlets to the west. 1377’ None Observed None Anticipated Moderate flow observed  2015 D. R. STRONG Consulting Engineers Inc. 24 Avana Ridge Level One Downstream Analysis Renton, Washington OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 TDA 1: NDA 2 Basin: Black River Subbasin Name: Panther Creek Subbasin Number: N/A 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 % 1/4 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. A2 2’ x 4’ Concrete Box Culvert Northeast side of SR 515, just southeast of the northwest property corner. 0’ None Observed Slight potential for blockage from debris/foliage Light Flow Observed A2-B2 Southwesterly Pipe Flow 18” Concrete Pipe 0’-16’ None Observed None Anticipated B2 Type 2 Catch Basin Slightly southwest of box culvert on the northeast side of SR 515. 18” Conc. (NE,W) 16’ None Observed None Anticipated Light Flow Observed B2-C2 Westerly Pipe Flow 18” Concrete Pipe, travels west under SR515 16’-84’ None Observed None Anticipated C2 (D1) Type 1 CB Southwestern side of SR 515, just east of parcel 2923059150. 18” Conc. (NE,SE), 24” Conc. (SW). Flow combines at point D1 and continues along path for NDA 1 84’ None Observed None Anticipated Moderate Flow Observed GRAPHIC SCALE 0 75 150 225 1 INCH =150 FT.