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Home My WebLink About30_2016-02-24 WN Drainage Report February 24, 2016 Weston Heights North Technical Information Report 702 Nile Ave NE, Renton, WA SDA Project #349-007-15 Prepared for: Prospect Development, LLC 2913 5th Avenue NE, Ste. 201 Puyallup, WA 98372 CIVIL ENGINEERING | PROJECT MANAGEMENT | PLANNING 1724 W. Marine View Drive, Suite 140, Everett, WA 98201 | 425.486.6533 | www.sdaengineers.com Weston Heights North Technical Information Report Weston Heights North Technical Information Report Prepared For: Prospect Development, LLC 2913 5th Avenue NE, Ste. 201 Puyallup, WA 98372 Prepared By: SDA Engineers 1724 West Marine View Drive, Ste 140 Everett, WA 98201 (425) 486-6533 Last save by: Jay Anderson on 2/23/16 R:\Projects\349 (prospect development)\007-15 (Weston North)\Technical\Reports\2016-02-24 TIR\2016-02-24 WN Drainage Report.docm 02-24-16 Weston Heights North Technical Information Report TABLE OF CONTENTS SECTION 1 PROJECT OVERVIEW  Project Overview  Figure 1 – TIR Worksheet  Figure 2 – Vicinity Map SECTION 2 CONDITIONS AND REQUIREMENTS SUMMARY SECTION 3 OFF-SITE ANALYSIS  Task 1 – Study Area Definition & Maps  Task 2 – Resource Review  Task 3 – Field Inspection  Task 4 – Drainage System Description and Problem Descriptions  Task 5 – Mitigation of Existing or Potential Problems  Appendix 3A – Downstream Analysis Map and Photos  Appendix 3B – Resource Review Documents SECTION 4 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN  Part A – Existing Site Hydrology  Part B – Developed Site Hydrology  Part C – Performance Standards  Part D – Flow Control System  Part E – Water Quality System  Part F – Wetland Hydrology  Appendix 4A – Flow Control Design Calculations  Appendix 4B – Treatment Design Calculations  Appendix 4C – Wetland Hydroperiod Calculations SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN SECTION 6 SPECIAL REPORTS AND STUDIES  Appendix 6A – Geotechnical Report  Appendix 6B – Olympus Villa LUA 10-090  Appendix 6C – Olympus Villa As-Built Plans SECTION 7 OTHER PERMITS SECTION 8 CSWPPP ANALYSIS AND DESIGN SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT SECTION 10 OPERATIONS AND MAINTENANCE MANUAL Weston Heights North Technical Information Report SECTION 1 PROJECT OVERVIEW Weston Heights North Technical Information Report Project Overview The Weston North project proposes the construction of 6 single family lots (1 existing single family residence to remain with 5 new lots) on two existing parcels totaling approximately 2.47 acres. Frontage improvements along both Nile Ave NE and NE 7th Pl, as well utility connections to the site are also proposed. The project occupies King County Tax Parcel Numbers 11230590002 and 947794TR-L, and is situated in the southwest quarter of Section 11, Township 28 North, Range 5 East, W.M. More specifically, the project is located on the east side of Nile Ave NE and south side of NE 7th Pl, approximately 0.4 miles north of the intersection of Nile Ave and NE 4th Street. A vicinity map has been provided as Figure 2 of this document. A wetland is located in the southcentral region of the project. This wetland and its surrounding buffer will remain undisturbed. As a result of these two separate projects, Weston North and Weston Heights, predeveloped runoff will be directed away from the wetland in order to mitigate developed conditions. An end goal of this project is to ensure the existing wetland hydroperiod is satisfied in the developed condition. The majority of land cover in the Weston North project limits has been developed. The western region currently houses a single family residence, a detached Quonset hut, shed and garage. The surrounding area features typical residential landscaping. The eastern region has been previously cleared of the historic forested vegetation and is currently all grassed area with no tree canopy. The wetland and area to the east of the wetland, outwards to the projects eastern border, remain forested. The topography of the combined subject parcel slopes moderately from east to west, with the southcentral section sloping inwards towards the wetland. The USDA Soil Survey for King county indicates that the site consists of Alderwood gravelly sandy loam, which is generally characterized as glacial till, with moderate runoff rates and low capacity for infiltration. Surface runoff will be detained through three separate facilities in order to avoid concentration of flows. Surface runoff will be directed to combined detention ponds, and/or a detention vault. Flow control structures are included to match the historic release rates. A flow spreader will service the Weston Heights detention pond on the east, spreading flows overland and ultimately into the wetland. New storm sewer infrastructure will convey storm water from the Weston Heights western detention vault to an existing roadside ditch along the eastern edge of Nile Ave NE. The Olympus Villa Pond ‘A’ flow control structure will be reconfigured to satisfy the historic release rates. This meets the requirements for Full Drainage Review, as described further in Section 4 of this report. Weston Heights North Technical Information Report FIGURE 1 TIR WORKSHEET Weston Heights North Technical Information Report FIGURE 2 VICINITY MAP Weston Heights North Technical Information Report SECTION 2 CONDITIONS AND REQUIREMENTS SUMMARY Weston Heights North Technical Information Report Conditions and Requirements Summary The project proposes more than 2,000 square feet of new impervious surface area, and is subject to the provisions for Full Drainage Review as outlined in the 2009 King County stormwater Design Manual (KCSWDM). Full Drainage Review requires the accommodation of 8 core requirements in addition to 5 special requirements – all of which are listed and discussed below.  Core Requirement #1 – Discharge at Natural Location The pre-developed drainage discharge locations will be maintained for post-developed conditions. Drainage improvements consist of implementing additional storm sewer infrastructure to utilize three separate facilities – the Weston Heights facility serving the eastern developments, the Weston Heights facility serving the western developments, and the Olympus Villa Pond ‘A’ serving the NE 7th Pl frontage and impervious areas of Lots 2 and 3. The eastern detention facility will discharge via level spreader into the existing wetland, maintaining the pre-developed surface water discharge location. The western detention facility will discharge via a new conveyance system into the existing roadside ditch along Nile Ave NE, maintaining the pre- developed surface water discharge location. The northern detention facility will discharge via improved conveyance system into the existing roadside ditch along Nile Ave NE, maintaining the pre-developed surface water discharge location.  Core Requirement #2 – Offsite Analysis A thorough off-site analysis is presented in Section 3 of this report.  Core Requirement #3 – Flow Control Flow control of surface runoff for this site is provided via three detention facilities – the Weston Heights facility serving the eastern developed area, the Weston Heights facility serving the western developed area, and the Olympus Villa Pond ‘A’ serving the northern developed areas. Design calculations for these facility are contained in Section 4 of this report.  Core Requirement #4 – Conveyance System Stormwater conveyance has been analyzed in Section 5 of this report.  Core Requirement #5 – Erosion & Sediment Control An erosion and sediment control analysis has been provided in Section 8 of this report.  Core Requirement #6 – Maintenance & Operations Maintenance and operations of the proposed storm drainage facilities is addressed in Section 10 of this report.  Core Requirement #7 – Financial Guarantees & Liabilities Financial guarantees and liabilities are addressed in Section 9 of this report.  Core Requirement #8 – Water Quality The two Weston Heights detention facilities, and Olympus Villa Pond ‘A’ each house permanent wetpools to allow for settling of solids that are suspended in the stormwater runoff. A discussion Weston Heights North Technical Information Report of the design methodology and calculations for this feature are provided in Section 4 of this document. SUMMARY OF SPECIAL REQUIREMENTS  Special Requirement #1 – Other Adopted Area-Specific Requirements There are no adopted basin plans or area-specific requirements affecting Parcel’s 1123059002 and 947794TR-L. Therefore, the project is exempt from this requirement.  Special Requirement #2 – Flood Hazard Area Delineation The project site and surrounding area is shown on FEMA Flood Insurance Rate Map No. 53033C0982, and is not located within a flood hazard area. Therefore, the project is exempt from this requirement. A portion of the FEMA map referenced above is included in Appendix 3-B of this report.  Special Requirement #3 – Flood Protection Facilities The project neither relies on an existing flood protection facility, nor proposes a new flood protection facility, and therefore, is exempt from this requirement.  Special Requirement #4 – Source Control This project does not require a commercial building or commercial site development permit, and therefore, is exempt from this requirement.  Special Requirement #5 – Oil Control This project does not have high-use site characteristics as defined in KCSWDM Section 1.3.5, and therefore, is exempt from this requirement. Weston Heights North Technical Information Report SECTION 3 OFFSITE ANALYSIS Weston Heights North Technical Information Report Task 1 – Study Area Definitions and Maps The project’s study area includes the subject parcels, and a flow path extending approximately 1-mile downstream of the site. An off-site analysis map has been included in Appendix 3A. Task 2 – Resource Review The following documents were reviewed, as prescribed by the 2009 King County Surface Water Design Manual:  Adopted Basin Plans There are no adopted basin plans which affect the subject property.  Floodplain/Floodway Maps The project site and surrounding area is shown on FEMA Flood Insurance Rate Map No. 53033C0982, and is not located within a flood hazard area. Therefore, the project is exempt from this requirement. A portion of the FEMA map referenced above is included in Appendix 3-B of this report.  Sensitive Areas Folio Maps The King County Sensitive Areas Folio Maps are outdated, and were not consulted for this project. However, a search for other sensitive area documents was performed, and the site was not to contain or be near a coal mine hazard area, erosion hazard area, steep slope, or landslide hazard area. A wetland area occupies the southcentral portion of the site, but will remain undisturbed by the project.  Drainage Complaints No documented downstream drainage complaints were located. The preliminary technical information report (prepared by others) also found no relevant drainage complaints.  Road Drainage Problems No road drainage problems were located that would be impacted by the project.  USDA Soil Survey for King County The USDA Soil Survey for King County indicates that the site is underlain by Alderwood soils, which are generally characterized as a consolidated till, with moderate runoff rates and little capacity for infiltration. A portion of the USDA Soil Survey map is included in Appendix 3B.  Wetlands Inventory Mapping A wetland exists near the middle of the project site.  Migrating River Studies No migrating river studies were located which affect the subject property. Weston Heights North Technical Information Report  DOE 303(d) List of Polluted Waters The DOE’s Water Quality Assessment Map tool does not identify any 303(d)-listed waterways in the downstream flowpath within several miles of the site. The project is ultimately tributary to the Cedar River, which is a 303(d) listed waterway at its discharge point to Lake Washington, but this is a substantial distance from the site, and the flow contribution from the project site is expected to be insignificant compared to the full capacity of the river at that point.  King County Designated Water Quality Problems King County I-Map does not identify the project site as containing or being tributary to any designated water quality problems. Task 3 – Field Inspection A Level 1 Downstream Analysis was prepared in the preliminary design phase by Core Design, and the photos from that analysis have been provided in Appendix 3A. The project site and downstream flowpath were visited on the afternoon of June 10, 2015 to verify the findings of that downstream analysis. Conditions at the time of the visit were warm and sunny, with no significant precipitation having occurred within the previous few days. No surface runoff was observed at the project site during the site visit. The downstream flowpath for the west side of the project simply follows a road-side ditch which extends southerly along the east side of Nile Ave NE. The ditch is primarily grassed, but has been stabilized with quarry spalls in some locations, and contains a number of culvert crossings beneath various intersections and driveways. The east half of the project falls to the central wetland area, then flows west where it is intercepted by the public storm drainage system in Orcas Ave W. This storm system flows to NE 6th Street, jogs westerly, and then discharges to the road-side ditch in Nile Ave NE. Task 4 – Drainage System Description and Problem Description The west half of the project generally falls toward the west, discharging to the road-side ditch along the east side of Nile Ave NE. The east half of the project generally falls toward the west, and is collected in the wetland area in the center of the project. Water from this wetland enters an overflow device just north of Orcas Ave W, then is conveyed to the Nile Ave NE roadside ditch. There were no significant erosion or sediment issues identified in the downstream system for the ¼-mile analysis distance. Task 5 – Mitigation of Existing or Potential Problems No significant hydraulic problems were observed at the project site or downstream. With routine maintenance to keep debris clear of the ditch/culverts, the downstream system is expected to continue functioning. Weston Heights North Technical Information Report APPENDIX 3A DOWNSTREAM ANALYSIS MAP AND PHOTOS Project Site Core Design, Inc. WESTON HEIGHTS Page 6 Level 1 Downstream Analysis Field Investigation A field investigation was completed on May 21, 2014. The temperature was approximately 60 degrees and sunny. The existing site has two residences with gravel driveways and a detached garage. The western quarter of the site is covered in lawn (surrounding the residences and garage) and the remaining site is forested with a wetland in the center of the site. The wetland drains south and overflows into a 12-inch storm drain in the Edenwood Plat which continues south to NE 6th Street. From NE 6th Street, the 12-inch storm drain flows west where it has a confluence with the drainage system on the east side of Nile Avenue NE. Overland flow from the west portion of the site drains west to Nile Avenue NE and drains south in series of grass or rock lined ditches and culverts on the east side of the street. The open channels range from a depth of 1 foot and a width of 4 feet with rock lining on the north end of the site (Picture 1) to a vegetated channel with a depth of 2 feet and width of 3 feet just below the project’s south property line. The ditch and culvert section continues south on the east side of Nile Avenue NE until approximately 300 feet north of NE 4th Pl, where it drains into an 18-inch storm drain and flows south. This is the quarter mile point downstream of the site. The City of Renton provides current storm water information online, using a GIS based system called COR Maps. COR Maps provides information on the type of pipes, manholes and catch basins in the city. Following the pipe flow direction from COR Maps, the 18-inch diameter concrete pipe crosses over to the west side of Nile Avenue just before it intersects with NE 4th street. The pipe then heads west down NE 4th street and crosses to the south side just before Jericho Avenue. The storm water pipe parallels Jericho Avenue running through private property until NE 2nd street. Picture 10 shows the manhole as the pipe crosses from the east side of Jericho Avenue and heads south down the center line of the road. Flow continues south until NE 1st street, where the 36-inch pipe heads west and discharges into Maplewood Creek. Core Design, Inc. WESTON HEIGHTS Page 7 1 – Looking south in drainage ditch along the east side of Nile Avenue next to the site 2 – Looking south along the east side of Nile Avenue into first culvert 3 – Looking south on the east side of Nile Avenue just downstream of site 4 – Looking south along the east side of Nile Avenue just before NE 6th Street Core Design, Inc. WESTON HEIGHTS Page 8 5 – Looking at a concrete pipe junction with water flowing left to right (south) down Nile Avenue 6 – Looking south on the east side of Nile Avenue at the last drainage ditch before pipe flow 7 – Looking south on the east side of Nile Avenue before NE 4th Street 8 – Looking South at the intersection of 4th and Nile Avenue where pipe flow crosses Nile Avenue from left to right (east to west) Core Design, Inc. WESTON HEIGHTS Page 9 9 – Existing man hole looking west on NE 4th street 10 – Existing Man hole looking South down Jericho Avenue 11 – Storm water outlet into Maplewood stream next to Jericho Street 12 – Looking at the downstream flow from Maplewood just after outlet Looking south on Weston Heights North Technical Information Report APPENDIX 3B RESOURCE REVIEW DOCUMENTS Soil Map—King County Area, Washington (Weston North) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/4/2016 Page 1 of 35260210526028052603505260420526049052605605260630526028052603505260420526049052605605260630564330564400564470564540564610564680564750564820564890564960 564330 564400 564470 564540 564610 564680 564750 564820 564890 564960 47° 29' 45'' N 122° 8' 45'' W47° 29' 45'' N122° 8' 14'' W47° 29' 31'' N 122° 8' 45'' W47° 29' 31'' N 122° 8' 14'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 100 200 400 600Feet 0 40 80 160 240Meters Map Scale: 1:3,000 if printed on A landscape (11" x 8.5") sheet. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 11, Sep 14, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 8, 2014—Jul 15, 2014 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—King County Area, Washington (Weston North) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/4/2016 Page 2 of 3 Map Unit Legend King County Area, Washington (WA633) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI AgC Alderwood gravelly sandy loam, 8 to 15 percent slopes 3.6 100.0% Totals for Area of Interest 3.6 100.0% Soil Map—King County Area, Washington Weston North Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 2/4/2016 Page 3 of 3 Weston Heights North Technical Information Report SECTION 4 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Weston Heights North Technical Information Report Part A – Existing Site Hydrology The project site runoff is contributory to the Weston Heights basins and the Olympus Villa Pond ‘A’ basin. This project utilizes the detention facilities constructed for those developments. The western portion of the project is intercepted by Nile Ave NE. The eastern portion discharges to the central wetland area. The central wetland area will be left undisturbed. The majority of land cover in the Weston North project limits has been developed. The western region currently houses a single family residence, a detached Quonset hut, shed and garage. The surrounding area features typical residential landscaping. The eastern region has been previously cleared of the historic forested vegetation and is currently all grassed area with no tree canopy. The wetland and area to the east of the wetland, outwards to the projects eastern border, remain forested. The topography of the combined subject parcel slopes moderately from east to west, with the southcentral section sloping inwards towards the wetland. For purposes of the stormwater model, both basins are considered to be forested in the historic condition, as prescribed by the 2009 King County Surface Water Design Manual (KCSWDM). Part B – Developed Site Hydrology The project proposes 6 single family lots (1 lot to remain with 5 new lots proposed) with the associated roadways and utilities. The 1 lot to remain will be undisturbed, but an interceptor ditch/swale will be installed to collect surface runoff to distribute into the central wetland, thereby satisfying the hydroperiod. The remaining 5 proposed lots (excluding the impervious areas for Lot 2 and Lot 3) will be collected and mitigated by the east pond. The landscape/yard area in Lot 2 will be a bypass basin and will be mitigated for by the west vault. The frontage improvements along Nile Ave NE will also be mitigated by the west vault. The frontage improvements along NE 7th Pl will be mitigated by the Olympus Villa Pond ‘A’, to the north. All three mitigation facilities downstream flow paths reconnect within ¼ mile of surface discharge. Part C – Performance Standards The project is subject to the “Conservation Flow Control” criteria outlined in Chapter 1 (Core Requirement #3) of the 2009 King County Surface Water Design Manual (KCSWDM). This requires that the 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. The project is subject to the “Basic Treatment” criteria outlined in Chapter 1 (Core Requirement #8). The goal of this requirement is 80% removal of total suspended solids for a typical rainfall year. Part D – Flow Control System The Weston Heights flow control facilities and the Olympus Villa Pond ‘A’ are utilized for this projects separate basins (separate basins in one similar threshold discharge area). Flow control will be achieved via an underground detention vault in the west basin, an open detention pond in the east basin, and an open detention pond in the Olympus Villa development – Pond ‘A’, to the north. An equivalent area trade has been utilized for a section of proposed target surface in Weston Heights that may not be feasibly routed to the west underground detention vault. The equivalent area is the eastern side of crowned Nile Ave NE roadway contributing offsite flow. This runoff will be collected in an underground conveyance system and routed to the west underground detention vault. In addition to the equivalent area, the west underground detention vault provides flow control for Weston Heights Lots 1-9. Weston North Lot 2 landscaping/yard area is not feasibly routed to the east pond, and there is not capacity in Olympus Villa Pond ‘A’. Therefore, this area is considered bypass and is mitigated by oversizing the west underground detention vault. The Olympus Villa LUA and as-built plans have been included in this report as Weston Heights North Technical Information Report Appendices 6B, and 6C, respectively. The Olympus Villa Pond ‘A’ was constructed larger than designed, thereby allowing this project’s utilization. The required detention volume of the original design was 36,042-CF. The constructed detention volume, as reported in the as-built plans, is 38,648-CF. This project directs the frontage improvement area (sidewalk/roadway/planter area) along NE 7th Pl, as well as the impervious areas of Lot 2 and Lot 3, to Olympus Villa Pond ‘A’. The ultimate discharge of Pond ‘A’ is the same point as the discharge for the west underground detention vault. Lots 4, 5, and 6, as well as Weston Heights Lots 10, 11, and 12 will be collected via underground conveyance and directed to the east pond. Lot 3 landscape/yard area will also be collected and directed to the east pond. All facilities have been designed using King County Runoff Time Series (KCRTS) stormwater runoff modeling software. Refer to Appendix 4A for “Flow Control Design Calculations”. Part E – Water Quality System Basic treatment for all basins on this project will be provided via wetpool storage. The Weston Heights project proposed a combined detention/treatment vault in the west basin. This vault will contain a permanent wetpool in the bottom of the vault, and room for detention storage in the upper portion of the vault. The Weston Heights project also proposed a combined detention/treatment pond in the east basin. This facility will contain a permanent wetpool in the bottom of the pond, and room for detention storage in the top portion of the pond. Olympus Villa Pond ‘A’ was constructed larger than designed. The required water quality volume of the original design was 9,881-CF. The constructed water quality volume, as reported in the as-built plans, is 15,479-CF. Refer to Appendix 4B for “Water Quality Design Calculations”. Part F – Wetland Hydrology A wetland is located in the southcentral region of the project. This wetland and its surrounding 56.26-ft buffer will remain undisturbed. This wetland area divides the Weston Heights development, immediately south of Weston North, into two separate drainage basins. The separate drainage basins, named West Basin and East Basin, are contained within one single threshold discharge area. The predeveloped conditions would have runoff from the eastern most extents of the Weston North project, in addition to the buffer area to the north and west, contributing flow to this wetland. The Weston Heights areas that contribute flow to the wetland include the entire East basin and a portion of the West basin. As a result of these two separate projects, Weston North and Weston Heights, predeveloped runoff will be directed away from the wetland in order to satisfy flow control requirements. In order to satisfy the existing wetland hydroperiod the runoff from the undisturbed Weston North Lot 1, will be redirected into the wetland via an interceptor dike. Refer to Appendix 4C for “Wetland Hydroperiod Calculations”. Weston Heights North Technical Information Report APPENDIX 4A FLOW CONTROL DESIGN CALCULATIONS Weston Heights North Technical Information Report KCSWDM – SCALE FACTOR Weston Heights North Technical Information Report Predeveloped West Basin Flow Frequency Analysis Time Series File:west-pre.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.139 2 2/09/01 18:00 0.167 1 100.00 0.990 0.024 7 1/05/02 16:00 0.139 2 25.00 0.960 0.089 4 2/28/03 16:00 0.113 3 10.00 0.900 0.016 8 3/03/04 2:00 0.089 4 5.00 0.800 0.081 5 1/05/05 10:00 0.081 5 3.00 0.667 0.066 6 1/18/06 21:00 0.066 6 2.00 0.500 0.113 3 11/24/06 5:00 0.024 7 1.30 0.231 0.167 1 1/09/08 7:00 0.016 8 1.10 0.091 Computed Peaks 0.157 50.00 0.980 Weston Heights North Technical Information Report Predeveloped Bypass Basin Flow Frequency Analysis Time Series File:bypass-pre.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.007 2 2/09/01 14:00 0.009 1 100.00 0.990 0.001 7 1/05/02 17:00 0.007 2 25.00 0.960 0.005 4 2/28/03 16:00 0.006 3 10.00 0.900 0.001 8 3/03/04 1:00 0.005 4 5.00 0.800 0.004 5 1/05/05 10:00 0.004 5 3.00 0.667 0.004 6 1/18/06 21:00 0.004 6 2.00 0.500 0.006 3 11/24/06 5:00 0.001 7 1.30 0.231 0.009 1 1/09/08 7:00 0.001 8 1.10 0.091 Computed Peaks 0.008 50.00 0.980 Weston Heights North Technical Information Report Combined Predeveloped Time-Series & Peaks – West Basin, Bypass Basin, East Basin Flow Frequency Analysis Time Series File:combined-pre.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.146 2 2/09/01 18:00 0.175 1 100.00 0.990 0.024 7 1/05/02 16:00 0.146 2 25.00 0.960 0.093 4 2/28/03 16:00 0.119 3 10.00 0.900 0.017 8 3/03/04 2:00 0.093 4 5.00 0.800 0.086 5 1/05/05 10:00 0.086 5 3.00 0.667 0.070 6 1/18/06 21:00 0.070 6 2.00 0.500 0.119 3 11/24/06 5:00 0.024 7 1.30 0.231 0.175 1 1/09/08 7:00 0.017 8 1.10 0.091 Computed Peaks 0.166 50.00 0.980 Weston Heights North Technical Information Report Developed West Basin Flow Frequency Analysis Time Series File:west-dev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.389 6 2/09/01 2:00 0.700 1 100.00 0.990 0.239 8 12/03/01 17:00 0.470 2 25.00 0.960 0.407 4 9/10/03 15:00 0.463 3 10.00 0.900 0.463 3 8/26/04 1:00 0.407 4 5.00 0.800 0.382 7 10/28/04 18:00 0.397 5 3.00 0.667 0.397 5 10/22/05 17:00 0.389 6 2.00 0.500 0.470 2 11/21/06 9:00 0.382 7 1.30 0.231 0.700 1 1/09/08 7:00 0.239 8 1.10 0.091 Computed Peaks 0.623 50.00 0.980 Weston Heights North Technical Information Report Developed Bypass Basin Flow Frequency Analysis Time Series File:bypass-dev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.013 3 2/09/01 2:00 0.028 1 100.00 0.990 0.004 8 12/03/01 17:00 0.015 2 25.00 0.960 0.007 5 2/28/03 16:00 0.013 3 10.00 0.900 0.009 4 8/26/04 1:00 0.009 4 5.00 0.800 0.007 6 1/05/05 10:00 0.007 5 3.00 0.667 0.006 7 10/22/05 17:00 0.007 6 2.00 0.500 0.015 2 11/21/06 9:00 0.006 7 1.30 0.231 0.028 1 1/09/08 7:00 0.004 8 1.10 0.091 Computed Peaks 0.023 50.00 0.980 Weston Heights North Technical Information Report West Vault Design Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 62.00 ft Facility Width: 48.00 ft Facility Area: 2976. sq. ft Effective Storage Depth: 7.51 ft Stage 0 Elevation: 505.79 ft Storage Volume: 22350. cu. ft Riser Head: 7.51 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.78 0.045 2 4.10 1.00 0.050 4.0 3 6.40 1.00 0.029 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 505.79 0. 0.000 0.000 0.00 0.01 505.80 30. 0.001 0.001 0.00 0.02 505.81 60. 0.001 0.003 0.00 0.03 505.82 89. 0.002 0.003 0.00 0.04 505.83 119. 0.003 0.003 0.00 0.05 505.84 149. 0.003 0.004 0.00 0.06 505.85 179. 0.004 0.004 0.00 0.07 505.86 208. 0.005 0.004 0.00 0.21 506.00 625. 0.014 0.008 0.00 0.36 506.15 1071. 0.025 0.010 0.00 0.51 506.30 1518. 0.035 0.012 0.00 0.65 506.44 1934. 0.044 0.013 0.00 0.80 506.59 2381. 0.055 0.015 0.00 0.95 506.74 2827. 0.065 0.016 0.00 1.10 506.89 3274. 0.075 0.017 0.00 1.24 507.03 3690. 0.085 0.018 0.00 1.39 507.18 4137. 0.095 0.020 0.00 1.54 507.33 4583. 0.105 0.021 0.00 1.68 507.47 5000. 0.115 0.021 0.00 1.83 507.62 5446. 0.125 0.022 0.00 1.98 507.77 5893. 0.135 0.023 0.00 2.13 507.92 6339. 0.146 0.024 0.00 2.27 508.06 6756. 0.155 0.025 0.00 2.42 508.21 7202. 0.165 0.026 0.00 2.57 508.36 7648. 0.176 0.027 0.00 2.72 508.51 8095. 0.186 0.027 0.00 2.86 508.65 8511. 0.195 0.028 0.00 3.01 508.80 8958. 0.206 0.029 0.00 3.16 508.95 9404. 0.216 0.029 0.00 3.30 509.09 9821. 0.225 0.030 0.00 3.45 509.24 10267. 0.236 0.031 0.00 3.60 509.39 10714. 0.246 0.031 0.00 3.75 509.54 11160. 0.256 0.032 0.00 3.89 509.68 11577. 0.266 0.033 0.00 4.04 509.83 12023. 0.276 0.033 0.00 Weston Heights North Technical Information Report 4.10 509.89 12202. 0.280 0.034 0.00 4.11 509.90 12231. 0.281 0.034 0.00 4.12 509.91 12261. 0.281 0.034 0.00 4.13 509.92 12291. 0.282 0.035 0.00 4.14 509.93 12321. 0.283 0.037 0.00 4.15 509.94 12350. 0.284 0.039 0.00 4.16 509.95 12380. 0.284 0.041 0.00 4.17 509.96 12410. 0.285 0.041 0.00 4.18 509.97 12440. 0.286 0.042 0.00 4.19 509.98 12469. 0.286 0.042 0.00 4.34 510.13 12916. 0.297 0.048 0.00 4.49 510.28 13362. 0.307 0.052 0.00 4.64 510.43 13809. 0.317 0.055 0.00 4.78 510.57 14225. 0.327 0.059 0.00 4.93 510.72 14672. 0.337 0.061 0.00 5.08 510.87 15118. 0.347 0.064 0.00 5.22 511.01 15535. 0.357 0.067 0.00 5.37 511.16 15981. 0.367 0.069 0.00 5.52 511.31 16428. 0.377 0.071 0.00 5.67 511.46 16874. 0.387 0.073 0.00 5.81 511.60 17291. 0.397 0.075 0.00 5.96 511.75 17737. 0.407 0.077 0.00 6.11 511.90 18183. 0.417 0.079 0.00 6.26 512.05 18630. 0.428 0.081 0.00 6.40 512.19 19046. 0.437 0.083 0.00 6.41 512.20 19076. 0.438 0.083 0.00 6.42 512.21 19106. 0.439 0.084 0.00 6.43 512.22 19136. 0.439 0.085 0.00 6.44 512.23 19165. 0.440 0.087 0.00 6.45 512.24 19195. 0.441 0.089 0.00 6.46 512.25 19225. 0.441 0.091 0.00 6.47 512.26 19255. 0.442 0.091 0.00 6.48 512.27 19284. 0.443 0.092 0.00 6.49 512.28 19314. 0.443 0.092 0.00 6.64 512.43 19761. 0.454 0.099 0.00 6.79 512.58 20207. 0.464 0.105 0.00 6.94 512.73 20653. 0.474 0.109 0.00 7.08 512.87 21070. 0.484 0.113 0.00 7.23 513.02 21516. 0.494 0.117 0.00 7.38 513.17 21963. 0.504 0.121 0.00 7.51 513.30 22350. 0.513 0.124 0.00 7.61 513.40 22647. 0.520 0.434 0.00 7.71 513.50 22945. 0.527 1.000 0.00 7.81 513.60 23243. 0.534 1.730 0.00 7.91 513.70 23540. 0.540 2.520 0.00 8.01 513.80 23838. 0.547 2.810 0.00 8.11 513.90 24135. 0.554 3.070 0.00 8.21 514.00 24433. 0.561 3.300 0.00 8.31 514.10 24731. 0.568 3.520 0.00 8.41 514.20 25028. 0.575 3.730 0.00 8.51 514.30 25326. 0.581 3.930 0.00 8.61 514.40 25623. 0.588 4.110 0.00 8.71 514.50 25921. 0.595 4.290 0.00 8.81 514.60 26219. 0.602 4.460 0.00 8.91 514.70 26516. 0.609 4.630 0.00 9.01 514.80 26814. 0.616 4.790 0.00 9.11 514.90 27111. 0.622 4.940 0.00 9.21 515.00 27409. 0.629 5.090 0.00 9.31 515.10 27707. 0.636 5.230 0.00 Weston Heights North Technical Information Report Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.70 0.65 7.65 513.44 22761. 0.523 2 0.39 0.12 7.44 513.23 22136. 0.508 3 0.47 0.12 7.50 513.29 22327. 0.513 4 0.23 0.06 5.02 510.81 14929. 0.343 5 0.27 0.06 5.02 510.81 14946. 0.343 6 0.23 0.03 3.85 509.64 11463. 0.263 7 0.46 0.03 2.99 508.78 8903. 0.204 8 0.22 0.02 2.08 507.87 6192. 0.142 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.65 0.03 ******** 0.17 0.67 2 0.12 0.01 ******** ******* 0.13 3 0.12 0.02 ******** ******* 0.13 4 0.06 0.01 ******** ******* 0.07 5 0.06 0.01 ******** ******* 0.07 6 0.03 0.01 ******** ******* 0.04 7 0.03 0.01 ******** ******* 0.03 8 0.02 0.00 ******** ******* 0.03 ---------------------------------- Route Time Series through Facility Inflow Time Series File:west-dev.tsf Outflow Time Series File:WV_rdout.tsf POC Time Series File:WV_dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.700 CFS at 7:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.649 CFS at 8:00 on Jan 9 in Year 8 Peak Reservoir Stage: 7.65 Ft Peak Reservoir Elev: 513.44 Ft Peak Reservoir Storage: 22761. Cu-Ft : 0.523 Ac-Ft Duration Comparison Anaylsis Base File: combined-pre.tsf New File: wv_dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.035 | 0.98E-02 0.87E-02 -11.6 | 0.98E-02 0.035 0.034 -1.4 0.043 | 0.67E-02 0.65E-02 -2.9 | 0.67E-02 0.043 0.040 -8.6 0.052 | 0.45E-02 0.48E-02 8.4 | 0.45E-02 0.052 0.054 3.1 0.061 | 0.30E-02 0.33E-02 9.9 | 0.30E-02 0.061 0.062 1.8 0.069 | 0.20E-02 0.18E-02 -9.8 | 0.20E-02 0.069 0.066 -4.4 0.078 | 0.14E-02 0.14E-02 -2.3 | 0.14E-02 0.078 0.077 -0.3 0.086 | 0.10E-02 0.99E-03 -1.6 | 0.10E-02 0.086 0.086 -0.3 0.095 | 0.75E-03 0.75E-03 0.0 | 0.75E-03 0.095 0.095 0.6 0.103 | 0.55E-03 0.60E-03 8.8 | 0.55E-03 0.103 0.106 2.8 0.112 | 0.31E-03 0.47E-03 52.6 | 0.31E-03 0.112 0.119 6.1 0.120 | 0.20E-03 0.26E-03 33.3 | 0.20E-03 0.120 0.125 3.9 0.129 | 0.13E-03 0.82E-04 -37.5 | 0.13E-03 0.129 0.127 -1.4 0.137 | 0.82E-04 0.00E+00 -100.0 | 0.82E-04 0.137 0.129 -6.2 0.146 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.146 0.130 -10.6 Maximum positive excursion = 0.007 cfs ( 6.7%) occurring at 0.112 cfs on the Base Data:combined-pre.tsf and at 0.120 cfs on the New Data:wv_dsout.tsf Maximum negative excursion = 0.006 cfs (-13.1%) Weston Heights North Technical Information Report occurring at 0.042 cfs on the Base Data:combined-pre.tsf and at 0.037 cfs on the New Data:wv_dsout.tsf Duration Comparison Anaylsis Weston Heights North Technical Information Report Predeveloped East Basin Flow Frequency Analysis Time Series File:east-pre.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.139 2 2/09/01 18:00 0.164 1 100.00 0.990 0.022 7 1/05/02 16:00 0.139 2 25.00 0.960 0.088 4 2/28/03 16:00 0.113 3 10.00 0.900 0.016 8 3/03/04 2:00 0.088 4 5.00 0.800 0.081 5 1/05/05 10:00 0.081 5 3.00 0.667 0.065 6 1/18/06 21:00 0.065 6 2.00 0.500 0.113 3 11/24/06 5:00 0.022 7 1.30 0.231 0.164 1 1/09/08 7:00 0.016 8 1.10 0.091 Computed Peaks 0.156 50.00 0.980 Weston Heights North Technical Information Report Developed East Basin Flow Frequency Analysis Time Series File:east-dev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.340 4 2/09/01 2:00 0.641 1 100.00 0.990 0.183 8 12/03/01 17:00 0.411 2 25.00 0.960 0.295 7 9/10/03 15:00 0.366 3 10.00 0.900 0.366 3 8/26/04 1:00 0.340 4 5.00 0.800 0.298 6 10/28/04 18:00 0.308 5 3.00 0.667 0.308 5 10/22/05 17:00 0.298 6 2.00 0.500 0.411 2 11/21/06 9:00 0.295 7 1.30 0.231 0.641 1 1/09/08 7:00 0.183 8 1.10 0.091 Computed Peaks 0.564 50.00 0.980 Weston Heights North Technical Information Report East Pond Design Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 3.30 H:1V Pond Bottom Length: 70.00 ft Pond Bottom Width: 39.00 ft Pond Bottom Area: 2730. sq. ft Top Area at 1 ft. FB: 7416. sq. ft 0.170 acres Effective Storage Depth: 4.00 ft Stage 0 Elevation: 518.00 ft Storage Volume: 17604. cu. ft 0.404 ac-ft Riser Head: 4.00 ft Riser Diameter: 12.00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.88 0.042 2 2.40 1.13 0.043 4.0 Top Notch Weir: Rectangular Length: 1.00 in Weir Height: 3.50 ft Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 518.00 0. 0.000 0.000 0.00 2730. 0.01 518.01 27. 0.001 0.002 0.00 2737. 0.02 518.02 55. 0.001 0.003 0.00 2744. 0.03 518.03 82. 0.002 0.003 0.00 2752. 0.04 518.04 110. 0.003 0.004 0.00 2759. 0.05 518.05 137. 0.003 0.005 0.00 2766. 0.06 518.06 165. 0.004 0.005 0.00 2773. 0.07 518.07 193. 0.004 0.006 0.00 2781. 0.17 518.17 475. 0.011 0.009 0.00 2854. 0.27 518.27 764. 0.018 0.011 0.00 2927. 0.37 518.37 1060. 0.024 0.013 0.00 3002. 0.47 518.47 1364. 0.031 0.014 0.00 3078. 0.57 518.57 1676. 0.038 0.016 0.00 3154. 0.67 518.67 1995. 0.046 0.017 0.00 3232. 0.77 518.77 2322. 0.053 0.018 0.00 3310. 0.87 518.87 2657. 0.061 0.019 0.00 3389. 0.97 518.97 3000. 0.069 0.020 0.00 3469. 1.07 519.07 3351. 0.077 0.022 0.00 3550. 1.17 519.17 3710. 0.085 0.022 0.00 3631. 1.27 519.27 4077. 0.094 0.023 0.00 3714. 1.37 519.37 4453. 0.102 0.024 0.00 3797. 1.47 519.47 4837. 0.111 0.025 0.00 3882. 1.57 519.57 5229. 0.120 0.026 0.00 3967. 1.67 519.67 5630. 0.129 0.027 0.00 4053. 1.77 519.77 6040. 0.139 0.028 0.00 4140. 1.87 519.87 6458. 0.148 0.028 0.00 4228. 1.97 519.97 6885. 0.158 0.029 0.00 4316. 2.07 520.07 7321. 0.168 0.030 0.00 4406. 2.17 520.17 7766. 0.178 0.031 0.00 4496. 2.27 520.27 8220. 0.189 0.031 0.00 4587. Weston Heights North Technical Information Report 2.37 520.37 8684. 0.199 0.032 0.00 4680. 2.40 520.40 8825. 0.203 0.032 0.00 4707. 2.41 520.41 8872. 0.204 0.032 0.00 4717. 2.42 520.42 8919. 0.205 0.033 0.00 4726. 2.44 520.44 9014. 0.207 0.035 0.00 4745. 2.45 520.45 9061. 0.208 0.037 0.00 4754. 2.46 520.46 9109. 0.209 0.039 0.00 4763. 2.47 520.47 9156. 0.210 0.042 0.00 4773. 2.48 520.48 9204. 0.211 0.043 0.00 4782. 2.49 520.49 9252. 0.212 0.043 0.00 4791. 2.59 520.59 9736. 0.224 0.049 0.00 4885. 2.69 520.69 10229. 0.235 0.053 0.00 4980. 2.79 520.79 10732. 0.246 0.056 0.00 5076. 2.89 520.89 11244. 0.258 0.059 0.00 5173. 2.99 520.99 11767. 0.270 0.062 0.00 5270. 3.09 521.09 12299. 0.282 0.065 0.00 5369. 3.19 521.19 12840. 0.295 0.068 0.00 5468. 3.29 521.29 13392. 0.307 0.070 0.00 5568. 3.39 521.39 13954. 0.320 0.072 0.00 5669. 3.49 521.49 14526. 0.333 0.075 0.00 5771. 3.50 521.50 14584. 0.335 0.075 0.00 5782. 3.56 521.56 14933. 0.343 0.080 0.00 5843. 3.63 521.63 15344. 0.352 0.086 0.00 5915. 3.69 521.69 15701. 0.360 0.092 0.00 5978. 3.75 521.75 16061. 0.369 0.101 0.00 6040. 3.81 521.81 16426. 0.377 0.110 0.00 6103. 3.88 521.88 16856. 0.387 0.121 0.00 6177. 3.94 521.94 17228. 0.396 0.132 0.00 6241. 4.00 522.00 17604. 0.404 0.144 0.00 6305. 4.10 522.10 18240. 0.419 0.454 0.00 6412. 4.20 522.20 18887. 0.434 1.020 0.00 6520. 4.30 522.30 19544. 0.449 1.750 0.00 6629. 4.40 522.40 20213. 0.464 2.540 0.00 6739. 4.50 522.50 20892. 0.480 2.830 0.00 6849. 4.60 522.60 21583. 0.495 3.080 0.00 6961. 4.70 522.70 22284. 0.512 3.320 0.00 7073. 4.80 522.80 22997. 0.528 3.540 0.00 7187. 4.90 522.90 23722. 0.545 3.750 0.00 7301. 5.00 523.00 24458. 0.561 3.940 0.00 7416. 5.10 523.10 25205. 0.579 4.130 0.00 7532. 5.20 523.20 25964. 0.596 4.310 0.00 7649. 5.30 523.30 26735. 0.614 4.480 0.00 7766. 5.40 523.40 27517. 0.632 4.640 0.00 7885. 5.50 523.50 28312. 0.650 4.800 0.00 8004. 5.60 523.60 29118. 0.668 4.950 0.00 8125. 5.70 523.70 29937. 0.687 5.100 0.00 8246. 5.80 523.80 30767. 0.706 5.250 0.00 8368. 5.90 523.90 31610. 0.726 5.390 0.00 8491. 6.00 524.00 32466. 0.745 5.520 0.00 8615. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.64 0.16 0.60 4.13 522.13 18403. 0.422 2 0.34 ******* 0.14 3.97 521.97 17430. 0.400 3 0.41 ******* 0.13 3.94 521.94 17212. 0.395 4 0.30 ******* 0.06 3.02 521.02 11940. 0.274 5 0.30 ******* 0.06 2.95 520.95 11560. 0.265 6 0.31 ******* 0.03 2.42 520.42 8914. 0.205 7 0.37 ******* 0.03 1.68 519.68 5670. 0.130 8 0.18 ******* 0.02 1.33 519.33 4301. 0.099 Weston Heights North Technical Information Report ---------------------------------- Route Time Series through Facility Inflow Time Series File:east-dev.tsf Outflow Time Series File:EP_rdout Inflow/Outflow Analysis Peak Inflow Discharge: 0.641 CFS at 7:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.597 CFS at 8:00 on Jan 9 in Year 8 Peak Reservoir Stage: 4.13 Ft Peak Reservoir Elev: 522.13 Ft Peak Reservoir Storage: 18403. Cu-Ft : 0.422 Ac-Ft Duration Comparison Anaylsis Base File: east-pre.tsf New File: ep_rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.032 | 0.10E-01 0.84E-02 -17.3 | 0.10E-01 0.032 0.032 -1.5 0.041 | 0.70E-02 0.73E-02 4.9 | 0.70E-02 0.041 0.043 6.9 0.049 | 0.47E-02 0.58E-02 24.8 | 0.47E-02 0.049 0.052 6.8 0.057 | 0.31E-02 0.36E-02 14.7 | 0.31E-02 0.057 0.059 3.0 0.065 | 0.20E-02 0.18E-02 -8.9 | 0.20E-02 0.065 0.063 -3.3 0.073 | 0.15E-02 0.12E-02 -17.4 | 0.15E-02 0.073 0.070 -4.1 0.081 | 0.10E-02 0.90E-03 -12.7 | 0.10E-02 0.081 0.077 -5.3 0.089 | 0.78E-03 0.62E-03 -20.8 | 0.78E-03 0.089 0.084 -5.7 0.098 | 0.55E-03 0.47E-03 -14.7 | 0.55E-03 0.098 0.091 -6.5 0.106 | 0.33E-03 0.34E-03 5.0 | 0.33E-03 0.106 0.110 3.6 0.114 | 0.20E-03 0.26E-03 33.3 | 0.20E-03 0.114 0.120 5.6 0.122 | 0.15E-03 0.18E-03 22.2 | 0.15E-03 0.122 0.126 2.9 0.130 | 0.98E-04 0.82E-04 -16.7 | 0.98E-04 0.130 0.130 -0.2 0.138 | 0.16E-04 0.16E-04 0.0 | 0.16E-04 0.138 0.138 0.0 Maximum positive excursion = 0.005 cfs ( 10.6%) occurring at 0.044 cfs on the Base Data:east-pre.tsf and at 0.048 cfs on the New Data:ep_rdout.tsf Maximum negative excursion = 0.004 cfs (-11.3%) occurring at 0.036 cfs on the Base Data:east-pre.tsf and at 0.032 cfs on the New Data:ep_rdout.tsf Weston Heights North Technical Information Report Weston Heights North Technical Information Report Equivalent East Pond Water Quality Storage Equivalent East Pond Detention Storage Equivalent Pond Sizing Calculation Pond Length =43 ft Pond Width =65 ft Actual Measured Pond Side Slope =3.3 :1 Contour Elev. Actual Contour Area Actual Incremental Volume Actual Cumulative Volume Contour Elev. Calculated Contour Area Calculated Incremental Volume Calculated Cumulative Volume Volume Difference (Calculated - Actual) (ft)(ft2)(ft3)(ft3)(ft)(ft2)(ft3)(ft3)(ft3) 514.00 674 0.00 0 514.00 641 0 0 0 514.50 875 387.13 387 514.50 834 369 369 -18 515.00 1075 487.38 875 515.00 1049 471 839 -35 515.50 1315 597.50 1,472 515.50 1285 583 1,423 -49 516.00 1555 717.50 2,190 516.00 1544 707 2,130 -60 516.50 1831 846.50 3,036 516.50 1824 842 2,972 -64 517.00 2107 984.50 4,021 517.00 2126 987 3,959 -61 517.50 2420 1,131.63 5,152 517.50 2449 1,144 5,103 -49 518.00 2732 1,287.88 6,440 518.00 2795 1,311 6,414 -26 Project: Project No: Sheet No: Made by: Checked by: Backchecked by: Date: 2/4/2016 Date: Date: Weston Heights 349-004-14 JDA Equivalent Pond Sizing Calculation Pond Length =70 ft Pond Width =39 ft Actual Measured Pond Side Slope =3.3 :1 Contour Elev. Actual Contour Area Actual Incremental Volume Actual Cumulative Volume Contour Elev. Calculated Contour Area Calculated Incremental Volume Calculated Cumulative Volume Volume Difference (Calculated - Actual) (ft)(ft2)(ft3)(ft3)(ft)(ft2)(ft3)(ft3)(ft3) 518.00 2732 0.00 0 518.00 2730 0 0 0 518.50 3107 1,459.75 1,460 518.50 3101 1,458 1,458 -2 519.00 3506 1,653.25 3,113 519.00 3493 1,648 3,106 -7 519.50 3932 1,859.50 4,973 519.50 3907 1,850 4,956 -16 520.00 4386 2,079.50 7,052 520.00 4343 2,063 7,019 -33 520.50 4866 2,313.00 9,365 520.50 4801 2,286 9,305 -60 521.00 5373 2,559.75 11,925 521.00 5280 2,520 11,825 -100 521.50 5907 2,820.00 14,745 521.50 5782 2,765 14,590 -155 522.00 6468 3,093.75 17,839 522.00 6305 3,022 17,612 -227 522.50 7055 3,380.75 21,219 522.50 6849 3,288 20,900 -319 523.00 7656 3,677.75 24,897 523.00 7416 3,566 24,467 -430 JDZ Project: Project No: Sheet No: Made by: Checked by: Backchecked by: Date: 12/21/2015 Date: Date: Weston Heights 349-004-14 Weston Heights North Technical Information Report Predeveloped Olympus Villa Pond ‘A’ Basin 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 0.222 2 2/09/01 18:00 0.303 1 100.00 0.990 0.075 7 1/05/02 16:00 0.222 2 25.00 0.960 0.178 3 2/28/03 3:00 0.178 3 10.00 0.900 0.025 8 8/26/04 2:00 0.176 4 5.00 0.800 0.107 6 1/05/05 8:00 0.157 5 3.00 0.667 0.176 4 1/18/06 20:00 0.107 6 2.00 0.500 0.157 5 11/24/06 4:00 0.075 7 1.30 0.231 0.303 1 1/09/08 9:00 0.025 8 1.10 0.091 Computed Peaks 0.276 50.00 0.980 *The original design information for Olympus Villa Pond ‘A’ may be found in the provided “Olympus Villa LUA 10-090” report included in Appendix 6C. The original predeveloped areas for Olympus Villa were: - 2.78 ac Till Forest - 0.10 ac Existing Wetland (modeled as impervious) The Weston North project added the following values to the predeveloped conditions: - 0.40 ac Till Forest Weston Heights North Technical Information Report Developed Olympus Village Basin Flow Frequency Analysis Time Series File:dev.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 0.633 6 2/09/01 2:00 1.29 1 100.00 0.990 0.510 8 1/05/02 16:00 0.792 2 25.00 0.960 0.763 3 2/27/03 7:00 0.763 3 10.00 0.900 0.545 7 8/26/04 2:00 0.671 4 5.00 0.800 0.658 5 10/28/04 16:00 0.658 5 3.00 0.667 0.671 4 1/18/06 16:00 0.633 6 2.00 0.500 0.792 2 10/26/06 0:00 0.545 7 1.30 0.231 1.29 1 1/09/08 6:00 0.510 8 1.10 0.091 Computed Peaks 1.12 50.00 0.980 *The original design information for Olympus Villa Pond ‘A’ may be found in the provided “Olympus Villa LUA 10-090” report included in Appendix 6C. The original developed areas for Olympus Villa were: - 1.35 ac Till Grass - 1.77 ac Impervious The Weston North project added the following values to the predeveloped conditions: - 0.09 ac Till Grass - 0.31 ac Impervious Weston Heights North Technical Information Report Olympus Village Pond ‘A’ Revised Riser Design & Equivalent Area/Volume Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 2.35 H:1V Pond Bottom Length: 96.36 ft Pond Bottom Width: 60.51 ft Pond Bottom Area: 5831. sq. ft Top Area at 1 ft. FB: 10980. sq. ft 0.252 acres Effective Storage Depth: 4.93 ft Stage 0 Elevation: 0.00 ft Storage Volume: 38588. cu. ft 0.886 ac-ft Riser Head: 4.93 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 1.04 0.065 2 3.27 1.63 0.092 4.0 3 3.90 1.04 0.030 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 0.00 0. 0.000 0.000 0.00 5831. 0.01 0.01 58. 0.001 0.003 0.00 5838. 0.02 0.02 117. 0.003 0.004 0.00 5846. 0.03 0.03 175. 0.004 0.005 0.00 5853. 0.04 0.04 234. 0.005 0.006 0.00 5860. 0.05 0.05 293. 0.007 0.007 0.00 5868. 0.06 0.06 351. 0.008 0.007 0.00 5875. 0.08 0.08 469. 0.011 0.008 0.00 5890. 0.09 0.09 528. 0.012 0.009 0.00 5897. 0.10 0.10 587. 0.013 0.009 0.00 5905. 0.20 0.20 1181. 0.027 0.013 0.00 5979. 0.30 0.30 1783. 0.041 0.016 0.00 6054. 0.40 0.40 2392. 0.055 0.018 0.00 6129. 0.50 0.50 3009. 0.069 0.021 0.00 6205. 0.60 0.60 3633. 0.083 0.023 0.00 6281. 0.70 0.70 4265. 0.098 0.024 0.00 6358. 0.80 0.80 4904. 0.113 0.026 0.00 6435. 0.90 0.90 5552. 0.127 0.028 0.00 6512. 1.00 1.00 6207. 0.142 0.029 0.00 6590. 1.10 1.10 6870. 0.158 0.031 0.00 6669. 1.20 1.20 7541. 0.173 0.032 0.00 6747. 1.30 1.30 8219. 0.189 0.033 0.00 6827. 1.40 1.40 8906. 0.204 0.035 0.00 6906. 1.50 1.50 9601. 0.220 0.036 0.00 6986. 1.60 1.60 10303. 0.237 0.037 0.00 7067. 1.70 1.70 11014. 0.253 0.038 0.00 7148. 1.80 1.80 11733. 0.269 0.039 0.00 7230. 1.90 1.90 12460. 0.286 0.040 0.00 7311. 2.00 2.00 13195. 0.303 0.041 0.00 7394. 2.10 2.10 13939. 0.320 0.042 0.00 7477. 2.20 2.20 14691. 0.337 0.043 0.00 7560. 2.30 2.30 15451. 0.355 0.044 0.00 7643. Weston Heights North Technical Information Report 2.40 2.40 16219. 0.372 0.045 0.00 7728. 2.50 2.50 16996. 0.390 0.046 0.00 7812. 2.60 2.60 17782. 0.408 0.047 0.00 7897. 2.70 2.70 18576. 0.426 0.048 0.00 7983. 2.80 2.80 19378. 0.445 0.049 0.00 8068. 2.90 2.90 20189. 0.463 0.050 0.00 8155. 3.00 3.00 21009. 0.482 0.051 0.00 8242. 3.10 3.10 21838. 0.501 0.052 0.00 8329. 3.20 3.20 22675. 0.521 0.052 0.00 8416. 3.27 3.27 23266. 0.534 0.053 0.00 8478. 3.29 3.29 23436. 0.538 0.054 0.00 8496. 3.30 3.30 23521. 0.540 0.055 0.00 8504. 3.32 3.32 23691. 0.544 0.058 0.00 8522. 3.34 3.34 23862. 0.548 0.062 0.00 8540. 3.35 3.35 23947. 0.550 0.067 0.00 8549. 3.37 3.37 24118. 0.554 0.073 0.00 8566. 3.39 3.39 24290. 0.558 0.079 0.00 8584. 3.41 3.41 24462. 0.562 0.080 0.00 8602. 3.42 3.42 24548. 0.564 0.082 0.00 8611. 3.52 3.52 25413. 0.583 0.091 0.00 8700. 3.62 3.62 26288. 0.603 0.098 0.00 8789. 3.72 3.72 27171. 0.624 0.105 0.00 8879. 3.82 3.82 28064. 0.644 0.110 0.00 8970. 3.90 3.90 28784. 0.661 0.115 0.00 9042. 3.91 3.91 28875. 0.663 0.115 0.00 9051. 3.92 3.92 28965. 0.665 0.117 0.00 9060. 3.93 3.93 29056. 0.667 0.118 0.00 9070. 3.94 3.94 29147. 0.669 0.120 0.00 9079. 3.95 3.95 29237. 0.671 0.123 0.00 9088. 3.96 3.96 29328. 0.673 0.125 0.00 9097. 3.98 3.98 29510. 0.677 0.127 0.00 9115. 3.99 3.99 29602. 0.680 0.128 0.00 9124. 4.09 4.09 30519. 0.701 0.137 0.00 9216. 4.19 4.19 31445. 0.722 0.144 0.00 9308. 4.29 4.29 32380. 0.743 0.151 0.00 9400. 4.39 4.39 33325. 0.765 0.157 0.00 9493. 4.49 4.49 34279. 0.787 0.163 0.00 9587. 4.59 4.59 35242. 0.809 0.169 0.00 9680. 4.69 4.69 36215. 0.831 0.175 0.00 9775. 4.79 4.79 37197. 0.854 0.180 0.00 9869. 4.89 4.89 38189. 0.877 0.185 0.00 9964. 4.93 4.93 38588. 0.886 0.187 0.00 10003. 5.03 5.03 39593. 0.909 0.500 0.00 10098. 5.13 5.13 40608. 0.932 1.070 0.00 10194. 5.23 5.23 41632. 0.956 1.800 0.00 10291. 5.33 5.33 42666. 0.979 2.600 0.00 10388. 5.43 5.43 43710. 1.003 2.880 0.00 10486. 5.53 5.53 44763. 1.028 3.140 0.00 10584. 5.63 5.63 45827. 1.052 3.380 0.00 10682. 5.73 5.73 46900. 1.077 3.600 0.00 10781. 5.83 5.83 47983. 1.102 3.810 0.00 10880. 5.93 5.93 49076. 1.127 4.010 0.00 10980. 6.03 6.03 50179. 1.152 4.200 0.00 11080. 6.13 6.13 51292. 1.177 4.380 0.00 11181. 6.23 6.23 52415. 1.203 4.550 0.00 11282. 6.33 6.33 53548. 1.229 4.720 0.00 11383. 6.43 6.43 54691. 1.256 4.880 0.00 11485. 6.53 6.53 55845. 1.282 5.040 0.00 11587. 6.63 6.63 57009. 1.309 5.190 0.00 11690. 6.73 6.73 58183. 1.336 5.330 0.00 11793. 6.83 6.83 59368. 1.363 5.470 0.00 11897. 6.93 6.93 60563. 1.390 5.610 0.00 12001. Weston Heights North Technical Information Report Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 1.29 0.30 0.83 5.09 5.09 40178. 0.922 2 0.79 ******* 0.05 3.01 3.01 21125. 0.485 3 0.76 ******* 0.15 4.31 4.31 32548. 0.747 4 0.67 ******* 0.11 3.82 3.82 28033. 0.644 5 0.66 ******* 0.04 1.60 1.60 10319. 0.237 6 0.63 ******* 0.19 4.93 4.93 38544. 0.885 7 0.54 ******* 0.04 2.14 2.14 14214. 0.326 8 0.51 ******* 0.05 2.86 2.86 19900. 0.457 ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:OV_rdout.tsf Inflow/Outflow Analysis Peak Inflow Discharge: 1.29 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.828 CFS at 10:00 on Jan 9 in Year 8 Peak Reservoir Stage: 5.09 Ft Peak Reservoir Elev: 5.09 Ft Peak Reservoir Storage: 40179. Cu-Ft : 0.922 Ac-Ft Duration Comparison Anaylsis Base File: predev.tsf New File: ov_rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.053 | 0.76E-02 0.66E-02 -12.3 | 0.76E-02 0.053 0.052 -1.2 0.066 | 0.56E-02 0.53E-02 -4.1 | 0.56E-02 0.066 0.061 -7.6 0.078 | 0.43E-02 0.49E-02 14.8 | 0.43E-02 0.078 0.085 8.9 0.091 | 0.32E-02 0.38E-02 17.6 | 0.32E-02 0.091 0.096 5.5 0.103 | 0.25E-02 0.28E-02 12.6 | 0.25E-02 0.103 0.107 3.7 0.116 | 0.18E-02 0.16E-02 -10.9 | 0.18E-02 0.116 0.113 -2.5 0.128 | 0.12E-02 0.14E-02 18.9 | 0.12E-02 0.128 0.137 6.9 0.141 | 0.91E-03 0.11E-02 19.6 | 0.91E-03 0.141 0.147 4.7 0.153 | 0.59E-03 0.67E-03 13.9 | 0.59E-03 0.153 0.157 2.3 0.166 | 0.36E-03 0.34E-03 -4.5 | 0.36E-03 0.166 0.165 -0.4 0.178 | 0.18E-03 0.16E-03 -9.1 | 0.18E-03 0.178 0.177 -0.4 0.191 | 0.13E-03 0.33E-04 -75.0 | 0.13E-03 0.191 0.181 -5.1 0.203 | 0.82E-04 0.00E+00 -100.0 | 0.82E-04 0.203 0.185 -9.0 0.216 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.216 0.199 -7.8 Maximum positive excursion = 0.007 cfs ( 9.5%) occurring at 0.073 cfs on the Base Data:predev.tsf and at 0.080 cfs on the New Data:ov_rdout.tsf Maximum negative excursion = 0.006 cfs (-10.4%) occurring at 0.061 cfs on the Base Data:predev.tsf and at 0.054 cfs on the New Data:ov_rdout.tsf Weston Heights North Technical Information Report Equivalent Olympus Villa Pond ‘A’ Dimensions/Side Slope Equivalent Pond Sizing Calculation Pond Length =96.35721918 ft Pond Width =60.51331798 ft Actual Measured Pond Side Slope =2.354987615 :1 Contour Elev. Actual Contour Area Actual Incremental Volume Actual Cumulative Volume Contour Elev. Calculated Contour Area Calculated Incremental Volume Calculated Cumulative Volume Volume Difference (Calculated - Actual) (ft)(ft2)(ft3)(ft3)(ft)(ft2)(ft3)(ft3)(ft3) 512.10 6370 0.00 0 512.10 5831 0 0 0 514.00 7198 12,889.60 12,890 514.00 7315 12,488 12,488 -401 516.00 8872 16,070.00 28,960 516.00 9050 16,365 28,853 -107 517.03 10115 9,778.30 38,738 517.03 10013 9,817 38,670 -68 518.00 10720 10,104.98 48,843 518.00 10962 10,173 48,843 0 JDA Project: Project No: Sheet No: Made by: Checked by: Backchecked by: Date: 2/24/2016 Date: Date: Weston Heights North 349-007-15 Weston Heights North Technical Information Report APPENDIX 4B WATER QUALITY DESIGN CALCULATIONS Weston Heights North Technical Information Report KCSWDM – SCALE FACTOR Weston Heights North Technical Information Report Date: 2/5/2016 Date: Date: Wetpool Description: Step 1: Identify the required wetpool volume factor (f) f =3 Fixed value per KCSWDM Section 6.4.1.1 (P. 6-70) Step 2: Determine rainfall (R) for the mean annual storm R =0.47 ft Per KCSWDM Figure 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V r) for the developed site A i =52,272 ft2 Area of impervious surface A tg =29,185 ft2 Area of till soil covered with grass A tf =0 ft2 Area of till soil covered with forest A o =0 ft2 Area of outwash soil covered with grass or forest R =0.47 in Rainfall from mean annual storm (from Step 2) V r =2,128 ft2 [KCSWDM Eq. 6-13] Step 4: Calculate required wetpool volume (V b) VB =6,385 ft3 [KCSWDM Equation 6-14] Step 5: Calculate minimum required wetpool depth (DREQ) Z1 =0.00 H:1V Side Slope #1 Z2 =0.00 H:1V Side Slope #2 Z3 =0.00 H:1V End Slope #3 Z4 =0.00 H:1V End Slope #4 LPOND =62 ft Pond length at top of wetpool WPOND =24 ft Pond width at top of wetpool DREQ =4.29 ft Minimum required pond depth Weston Heights - West Vault Wetpool Sizing Calculation (Per KCSWDM Section 6.4.1.1) Made by: Checked by: Backchecked by: Project: Project No: Weston Heights 349-004 JDA Weston Heights North Technical Information Report Date: 2/23/2016 Date: Date: Wetpool Description: Step 1: Identify the required wetpool volume factor (f) f =3 Fixed value per KCSWDM Section 6.4.1.1 (P. 6-70) Step 2: Determine rainfall (R) for the mean annual storm R =0.47 ft Per KCSWDM Figure 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V r) for the developed site A i =52,272 ft2 Area of impervious surface A tg =29,185 ft2 Area of till soil covered with grass A tf =0 ft2 Area of till soil covered with forest A o =0 ft2 Area of outwash soil covered with grass or forest R =0.47 in Rainfall from mean annual storm (from Step 2) V r =2,128 ft2 [KCSWDM Eq. 6-13] Step 4: Calculate required wetpool volume (V b) VB =6,385 ft3 [KCSWDM Equation 6-14] Step 5: Calculate minimum required wetpool depth (DREQ) Z1 =0.00 H:1V Side Slope #1 Z2 =0.00 H:1V Side Slope #2 Z3 =0.00 H:1V End Slope #3 Z4 =0.00 H:1V End Slope #4 LPOND =64 ft Pond length at top of wetpool WPOND =24 ft Pond width at top of wetpool DREQ =4.16 ft Minimum required pond depth Made by: Checked by: Backchecked by: Project: Project No: Weston Heights 349-004 JDA Weston Heights - West Vault Wetpool Sizing Calculation (Per KCSWDM Section 6.4.1.1) Weston Heights North Technical Information Report *This is the original design required volume for water quality in the Olympus Villa Pond ‘A’. The as-built facility provides 15,479-CF of volume, for a difference of 5,598-CF in additional wetpool storage capacity. Weston Heights North Technical Information Report *This is the required wetpool volume resulting from the addition of the Weston North basin area to Olympus Villa Pond ‘A’ (depicted as North Basin in the basin figures). This volume is below the as-built facility’s 15,479-CF of useable wetpool storage. The additional areas from Weston North leaves a remainder of 4,055-CF in wetpool storage capacity. Date: 2/24/2016 Date: Date: Wetpool Description: Step 1: Identify the required wetpool volume factor (f) f =3 Fixed value per KCSWDM Section 6.4.1.1 (P. 6-70) Step 2: Determine rainfall (R) for the mean annual storm R =0.47 ft Per KCSWDM Figure 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V r) for the developed site A i =90,605 ft2 Area of impervious surface A tg =62,726 ft2 Area of till soil covered with grass A tf =0 ft2 Area of till soil covered with forest A o =0 ft2 Area of outwash soil covered with grass or forest R =0.47 in Rainfall from mean annual storm (from Step 2) V r =3,808 ft2 [KCSWDM Eq. 6-13] Step 4: Calculate required wetpool volume (V b) VB =11,424 ft3 [KCSWDM Equation 6-14] Made by: Checked by: Backchecked by: Project: Project No: Weston Heights North 349-007 JDA Olympus Villa Pond 'A' - Proposed Design Req'd Volume Wetpool Sizing Calculation (Per KCSWDM Section 6.4.1.1) Weston Heights North Technical Information Report APPENDIX 4C WETLAND HYDROPERIOD CALCULATIONS Weston Heights North Technical Information Report WWHM2012 – Wetland Fluctuation Report WWHM2012 PROJECT REPORT ___________________________________________________________________ Project Name: Wetland Hydroperiod_160127 Site Name: Weston Heights Site Address: Nile Ave City : Renton Report Date: 2/2/2016 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.17 Version : 2015/02/16 ___________________________________________________________________ PREDEVELOPED LAND USE Name : Predeveloped Bypass: No GroundWater: No Pervious Land Use Acres C, Forest, Mod 2.39 C, Lawn, Flat 1.64 Pervious Total 4.03 Impervious Land Use Acres ROADS FLAT 0.12 Impervious Total 0.12 Basin Total 4.15 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ MITIGATED LAND USE Name : Developed Bypass: No GroundWater: No Pervious Land Use Acres C, Forest, Mod 3.01 C, Lawn, Flat 1.14 Pervious Total 4.15 Impervious Land Use Acres ROADS FLAT 0.2 Weston Heights North Technical Information Report Impervious Total 0.2 Basin Total 4.35 ___________________________________________________________________ Element Flows To: Surface Interflow Groundwater ___________________________________________________________________ ___________________________________________________________________ ANALYSIS RESULTS Wetland Hydroperiod ___________________________________________________________________ Wetlands Fluctuation for POC 1 Average Annual Volume (acft) Month Predevel Mitigated Percent Pass/Fail Jan 83.5601 86.9170 104.0 Pass Feb 63.2200 66.2666 104.8 Pass Mar 54.1575 56.9560 105.2 Pass Apr 33.8289 35.8210 105.9 Pass May 18.5240 19.7525 106.6 Pass Jun 14.2424 15.0048 105.4 Pass Jul 9.8981 10.6035 107.1 Pass Aug 9.1697 9.6184 104.9 Pass Sep 9.0665 9.3872 103.5 Pass Oct 17.9055 17.3633 97.0 Pass Nov 53.2741 52.4182 98.4 Pass Dec 75.5175 77.4050 102.5 Pass Day Predevel Mitigated Percent Pass/Fail Jan1 2.7430 2.8534 104.0 Pass 2 2.7092 2.7884 102.9 Pass 3 2.5126 2.6107 103.9 Pass 4 2.8627 2.9740 103.9 Pass 5 2.9059 3.0093 103.6 Pass 6 3.0584 3.1707 103.7 Pass 7 2.8224 2.9184 103.4 Pass 8 2.8327 2.9262 103.3 Pass 9 2.4328 2.5347 104.2 Pass 10 2.2725 2.3652 104.1 Pass 11 2.4503 2.5511 104.1 Pass 12 2.5436 2.6594 104.6 Pass 13 3.0111 3.1398 104.3 Pass 14 3.0505 3.1595 103.6 Pass 15 2.7660 2.8722 103.8 Pass 16 2.7902 2.8977 103.9 Pass 17 2.7323 2.8478 104.2 Pass 18 2.9999 3.1201 104.0 Pass 19 2.8991 3.0167 104.1 Pass 20 2.6959 2.8032 104.0 Pass 21 2.4794 2.5859 104.3 Pass 22 2.6825 2.8027 104.5 Pass 23 3.0014 3.1211 104.0 Pass 24 2.7711 2.8702 103.6 Pass Weston Heights North Technical Information Report 25 2.4305 2.5326 104.2 Pass 26 2.4197 2.5290 104.5 Pass 27 2.3875 2.5004 104.7 Pass 28 2.5203 2.6423 104.8 Pass 29 2.7496 2.8666 104.3 Pass 30 2.6812 2.8084 104.7 Pass 31 2.6590 2.7690 104.1 Pass Feb1 2.4262 2.5359 104.5 Pass 2 2.1887 2.2876 104.5 Pass 3 2.1662 2.2711 104.8 Pass 4 1.8991 1.9977 105.2 Pass 5 2.0356 2.1533 105.8 Pass 6 2.1972 2.3083 105.1 Pass 7 2.6078 2.7387 105.0 Pass 8 2.6145 2.7341 104.6 Pass 9 2.2087 2.3179 104.9 Pass 10 1.9356 2.0377 105.3 Pass 11 2.1449 2.2598 105.4 Pass 12 2.2049 2.3058 104.6 Pass 13 2.0175 2.1154 104.9 Pass 14 2.1635 2.2767 105.2 Pass 15 2.3941 2.5015 104.5 Pass 16 2.3948 2.5049 104.6 Pass 17 2.3224 2.4363 104.9 Pass 18 2.7174 2.8362 104.4 Pass 19 2.4868 2.5887 104.1 Pass 20 2.2243 2.3342 104.9 Pass 21 2.0803 2.1826 104.9 Pass 22 2.0157 2.1201 105.2 Pass 23 2.1781 2.2843 104.9 Pass 24 2.1322 2.2339 104.8 Pass 25 1.9896 2.0836 104.7 Pass 26 2.1143 2.2143 104.7 Pass 27 2.1150 2.2224 105.1 Pass 28 2.2285 2.3415 105.1 Pass 29 1.9059 2.0044 105.2 Pass Mar1 1.8695 1.9637 105.0 Pass 2 2.1162 2.2193 104.9 Pass 3 2.1276 2.2285 104.7 Pass 4 2.2343 2.3427 104.9 Pass 5 1.8870 1.9784 104.8 Pass 6 1.7340 1.8280 105.4 Pass 7 1.6571 1.7591 106.2 Pass 8 1.9223 2.0242 105.3 Pass 9 1.9731 2.0676 104.8 Pass 10 1.9524 2.0541 105.2 Pass 11 2.1620 2.2708 105.0 Pass 12 1.9730 2.0618 104.5 Pass 13 1.8341 1.9234 104.9 Pass 14 1.8731 1.9703 105.2 Pass 15 1.7426 1.8322 105.1 Pass 16 1.7716 1.8597 105.0 Pass 17 1.7369 1.8329 105.5 Pass 18 1.6771 1.7601 105.0 Pass 19 1.5238 1.6050 105.3 Pass 20 1.3688 1.4434 105.5 Pass 21 1.5437 1.6436 106.5 Pass 22 1.7103 1.8065 105.6 Pass 23 1.6897 1.7777 105.2 Pass 24 1.6292 1.7066 104.7 Pass 25 1.5146 1.5882 104.9 Pass 26 1.4484 1.5233 105.2 Pass 27 1.3629 1.4393 105.6 Pass Weston Heights North Technical Information Report 28 1.4321 1.5121 105.6 Pass 29 1.4413 1.5171 105.3 Pass 30 1.3416 1.4118 105.2 Pass 31 1.2912 1.3637 105.6 Pass Apr1 1.2031 1.2743 105.9 Pass 2 1.2292 1.2982 105.6 Pass 3 1.4703 1.5584 106.0 Pass 4 1.5932 1.6776 105.3 Pass 5 1.4277 1.5050 105.4 Pass 6 1.2210 1.2883 105.5 Pass 7 1.2380 1.3139 106.1 Pass 8 1.3309 1.4079 105.8 Pass 9 1.2034 1.2700 105.5 Pass 10 1.1577 1.2253 105.8 Pass 11 1.1392 1.2042 105.7 Pass 12 1.1922 1.2654 106.1 Pass 13 1.1368 1.2038 105.9 Pass 14 1.0513 1.1166 106.2 Pass 15 1.2047 1.2791 106.2 Pass 16 1.2644 1.3280 105.0 Pass 17 0.9998 1.0551 105.5 Pass 18 1.1756 1.2543 106.7 Pass 19 1.2570 1.3122 104.4 Pass 20 0.9942 1.0472 105.3 Pass 21 0.9451 1.0103 106.9 Pass 22 1.1374 1.2077 106.2 Pass 23 0.9987 1.0579 105.9 Pass 24 0.8788 0.9316 106.0 Pass 25 0.7714 0.8228 106.7 Pass 26 0.8072 0.8689 107.6 Pass 27 0.7815 0.8327 106.6 Pass 28 0.8216 0.8813 107.3 Pass 29 0.9064 0.9602 105.9 Pass 30 0.8834 0.9340 105.7 Pass May1 0.8146 0.8594 105.5 Pass 2 0.7234 0.7672 106.1 Pass 3 0.7039 0.7546 107.2 Pass 4 0.7335 0.7820 106.6 Pass 5 0.7237 0.7734 106.9 Pass 6 0.6674 0.7119 106.7 Pass 7 0.6067 0.6482 106.8 Pass 8 0.5894 0.6303 106.9 Pass 9 0.5948 0.6358 106.9 Pass 10 0.6170 0.6672 108.1 Pass 11 0.5564 0.5989 107.6 Pass 12 0.5951 0.6374 107.1 Pass 13 0.6041 0.6489 107.4 Pass 14 0.5836 0.6227 106.7 Pass 15 0.5778 0.6119 105.9 Pass 16 0.5337 0.5718 107.1 Pass 17 0.5369 0.5784 107.7 Pass 18 0.5724 0.6180 108.0 Pass 19 0.5710 0.6071 106.3 Pass 20 0.5182 0.5539 106.9 Pass 21 0.5125 0.5471 106.8 Pass 22 0.5033 0.5448 108.3 Pass 23 0.4946 0.5343 108.0 Pass 24 0.4706 0.5038 107.1 Pass 25 0.4739 0.5185 109.4 Pass 26 0.4951 0.5241 105.9 Pass 27 0.5079 0.5349 105.3 Pass 28 0.5618 0.5888 104.8 Pass 29 0.5996 0.6263 104.5 Pass Weston Heights North Technical Information Report 30 0.5979 0.6163 103.1 Pass 31 0.5806 0.5976 102.9 Pass Jun1 0.6004 0.6172 102.8 Pass 2 0.5982 0.6274 104.9 Pass 3 0.5865 0.6154 104.9 Pass 4 0.5109 0.5358 104.9 Pass 5 0.5241 0.5587 106.6 Pass 6 0.6303 0.6477 102.8 Pass 7 0.5774 0.5972 103.4 Pass 8 0.5766 0.6013 104.3 Pass 9 0.5866 0.6113 104.2 Pass 10 0.5274 0.5552 105.3 Pass 11 0.5057 0.5314 105.1 Pass 12 0.4584 0.4785 104.4 Pass 13 0.4170 0.4425 106.1 Pass 14 0.4063 0.4375 107.7 Pass 15 0.4152 0.4464 107.5 Pass 16 0.4373 0.4724 108.0 Pass 17 0.4199 0.4459 106.2 Pass 18 0.3956 0.4247 107.4 Pass 19 0.3964 0.4291 108.3 Pass 20 0.4374 0.4605 105.3 Pass 21 0.4318 0.4480 103.8 Pass 22 0.4067 0.4312 106.0 Pass 23 0.4853 0.5189 106.9 Pass 24 0.4480 0.4598 102.6 Pass 25 0.3991 0.4185 104.9 Pass 26 0.3748 0.4001 106.8 Pass 27 0.3709 0.4006 108.0 Pass 28 0.3681 0.3962 107.6 Pass 29 0.3693 0.3977 107.7 Pass 30 0.3923 0.4172 106.4 Pass Jul1 0.3715 0.3955 106.5 Pass 2 0.3610 0.3851 106.7 Pass 3 0.3479 0.3709 106.6 Pass 4 0.3485 0.3757 107.8 Pass 5 0.3339 0.3571 107.0 Pass 6 0.3323 0.3599 108.3 Pass 7 0.3402 0.3676 108.1 Pass 8 0.3416 0.3708 108.6 Pass 9 0.3339 0.3588 107.5 Pass 10 0.3199 0.3419 106.9 Pass 11 0.3344 0.3629 108.5 Pass 12 0.3449 0.3654 105.9 Pass 13 0.3392 0.3601 106.1 Pass 14 0.3227 0.3387 105.0 Pass 15 0.3399 0.3708 109.1 Pass 16 0.3213 0.3408 106.1 Pass 17 0.3107 0.3297 106.1 Pass 18 0.3072 0.3298 107.4 Pass 19 0.3010 0.3230 107.3 Pass 20 0.2948 0.3157 107.1 Pass 21 0.2980 0.3207 107.6 Pass 22 0.2921 0.3132 107.2 Pass 23 0.2869 0.3069 107.0 Pass 24 0.2856 0.3063 107.2 Pass 25 0.2988 0.3269 109.4 Pass 26 0.2873 0.3070 106.9 Pass 27 0.2835 0.3032 106.9 Pass 28 0.2769 0.2951 106.6 Pass 29 0.2751 0.2941 106.9 Pass 30 0.2745 0.2926 106.6 Pass 31 0.2818 0.3025 107.3 Pass Weston Heights North Technical Information Report Aug1 0.2813 0.3042 108.2 Pass 2 0.3049 0.3226 105.8 Pass 3 0.2855 0.3021 105.8 Pass 4 0.2758 0.2904 105.3 Pass 5 0.2902 0.3117 107.4 Pass 6 0.2885 0.3115 108.0 Pass 7 0.2744 0.2880 105.0 Pass 8 0.2818 0.3032 107.6 Pass 9 0.2690 0.2837 105.5 Pass 10 0.2651 0.2833 106.8 Pass 11 0.2607 0.2792 107.1 Pass 12 0.2557 0.2731 106.8 Pass 13 0.2935 0.3143 107.1 Pass 14 0.3247 0.3377 104.0 Pass 15 0.2920 0.3008 103.0 Pass 16 0.2925 0.3040 103.9 Pass 17 0.3120 0.3270 104.8 Pass 18 0.2945 0.3112 105.7 Pass 19 0.2755 0.2881 104.6 Pass 20 0.2755 0.2965 107.6 Pass 21 0.2855 0.3098 108.5 Pass 22 0.3410 0.3609 105.8 Pass 23 0.3444 0.3501 101.7 Pass 24 0.3414 0.3409 99.9 Pass 25 0.3505 0.3513 100.2 Pass 26 0.3272 0.3359 102.6 Pass 27 0.2986 0.3082 103.2 Pass 28 0.3044 0.3168 104.1 Pass 29 0.3133 0.3128 99.8 Pass 30 0.2885 0.2968 102.9 Pass 31 0.2829 0.2972 105.1 Pass Sep1 0.2818 0.2979 105.7 Pass 2 0.2649 0.2800 105.7 Pass 3 0.2810 0.2997 106.7 Pass 4 0.2587 0.2722 105.2 Pass 5 0.2713 0.2908 107.2 Pass 6 0.2465 0.2570 104.3 Pass 7 0.2661 0.2854 107.3 Pass 8 0.2659 0.2772 104.3 Pass 9 0.2721 0.2949 108.4 Pass 10 0.2597 0.2759 106.2 Pass 11 0.2652 0.2706 102.0 Pass 12 0.2525 0.2652 105.0 Pass 13 0.2644 0.2894 109.5 Pass 14 0.2478 0.2658 107.3 Pass 15 0.2569 0.2762 107.5 Pass 16 0.3463 0.3755 108.4 Pass 17 0.3285 0.3301 100.5 Pass 18 0.3278 0.3360 102.5 Pass 19 0.3146 0.3221 102.4 Pass 20 0.3152 0.3166 100.4 Pass 21 0.3942 0.3991 101.2 Pass 22 0.4552 0.4377 96.2 Pass 23 0.3714 0.3707 99.8 Pass 24 0.3180 0.3269 102.8 Pass 25 0.3202 0.3270 102.1 Pass 26 0.3047 0.3161 103.7 Pass 27 0.3497 0.3484 99.6 Pass 28 0.3116 0.3119 100.1 Pass 29 0.3716 0.3736 100.6 Pass 30 0.3468 0.3376 97.3 Pass Oct1 0.3370 0.3322 98.6 Pass 2 0.3294 0.3376 102.5 Pass Weston Heights North Technical Information Report 3 0.3590 0.3714 103.5 Pass 4 0.3794 0.3717 98.0 Pass 5 0.6622 0.6694 101.1 Pass 6 0.5517 0.5501 99.7 Pass 7 0.5764 0.5836 101.2 Pass 8 0.6355 0.6100 96.0 Pass 9 0.6238 0.5983 95.9 Pass 10 0.4975 0.4661 93.7 Pass 11 0.3969 0.3927 98.9 Pass 12 0.3829 0.3864 100.9 Pass 13 0.3533 0.3641 103.1 Pass 14 0.3660 0.3652 99.8 Pass 15 0.3655 0.3683 100.7 Pass 16 0.4480 0.4502 100.5 Pass 17 0.5083 0.4877 95.9 Pass 18 0.5993 0.5724 95.5 Pass 19 0.9120 0.8832 96.8 Pass 20 0.9762 0.9332 95.6 Pass 21 0.7848 0.7455 95.0 Pass 22 0.6761 0.6374 94.3 Pass 23 0.6093 0.5795 95.1 Pass 24 0.5887 0.5680 96.5 Pass 25 0.6908 0.6507 94.2 Pass 26 0.7488 0.7118 95.1 Pass 27 0.7848 0.7261 92.5 Pass 28 0.8381 0.7874 93.9 Pass 29 0.8031 0.7701 95.9 Pass 30 0.7731 0.7555 97.7 Pass 31 0.7833 0.7544 96.3 Pass Nov1 0.8828 0.8560 97.0 Pass 2 1.1326 1.0864 95.9 Pass 3 1.3244 1.2282 92.7 Pass 4 1.1448 1.0417 91.0 Pass 5 1.3206 1.2589 95.3 Pass 6 1.3471 1.2806 95.1 Pass 7 1.1443 1.0887 95.1 Pass 8 1.2744 1.2302 96.5 Pass 9 1.4212 1.3733 96.6 Pass 10 1.6837 1.6439 97.6 Pass 11 1.8512 1.7812 96.2 Pass 12 1.7836 1.7170 96.3 Pass 13 1.8537 1.7787 96.0 Pass 14 1.5832 1.5346 96.9 Pass 15 1.5666 1.5344 97.9 Pass 16 1.6178 1.5823 97.8 Pass 17 1.6998 1.6613 97.7 Pass 18 2.0576 2.0667 100.4 Pass 19 2.3915 2.3789 99.5 Pass 20 2.2344 2.2116 99.0 Pass 21 1.9792 1.9702 99.5 Pass 22 2.0826 2.1103 101.3 Pass 23 2.9019 2.9154 100.5 Pass 24 2.9612 2.9930 101.1 Pass 25 2.6232 2.6335 100.4 Pass 26 2.3597 2.3573 99.9 Pass 27 1.9725 1.9817 100.5 Pass 28 2.0196 2.0490 101.5 Pass 29 2.2769 2.3194 101.9 Pass 30 2.1939 2.2162 101.0 Pass Dec1 2.3079 2.3272 100.8 Pass 2 2.8916 2.9337 101.5 Pass 3 2.6311 2.6640 101.3 Pass 4 2.3432 2.3947 102.2 Pass Weston Heights North Technical Information Report 5 2.3360 2.3678 101.4 Pass 6 2.0890 2.1250 101.7 Pass 7 2.0435 2.0847 102.0 Pass 8 2.1148 2.1701 102.6 Pass 9 2.3573 2.4166 102.5 Pass 10 2.4178 2.4762 102.4 Pass 11 2.5444 2.5989 102.1 Pass 12 2.5694 2.6223 102.1 Pass 13 2.6401 2.6939 102.0 Pass 14 3.0557 3.1354 102.6 Pass 15 2.7431 2.8105 102.5 Pass 16 2.4663 2.5182 102.1 Pass 17 2.2397 2.2970 102.6 Pass 18 2.0809 2.1458 103.1 Pass 19 2.4036 2.4877 103.5 Pass 20 2.4839 2.5477 102.6 Pass 21 2.3052 2.3657 102.6 Pass 22 2.3251 2.3955 103.0 Pass 23 2.2466 2.3116 102.9 Pass 24 2.1462 2.2270 103.8 Pass 25 2.5632 2.6587 103.7 Pass 26 2.9059 2.9964 103.1 Pass 27 2.3743 2.4429 102.9 Pass 28 2.3438 2.4457 104.3 Pass 29 2.9308 3.0287 103.3 Pass 30 2.4225 2.5019 103.3 Pass 31 2.3459 2.4386 104.0 Pass ___________________________________________________________________ This program and accompanying documentation are provided 'as-is' without warranty of any kind. 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Weston Heights North Technical Information Report WWHM2012 – Site Information WWHM2012 – Predeveloped Scenario Weston Heights North Technical Information Report WWHM2012 – Developed Scenario WWHM2012 – Fluctuation Analysis Weston Heights North Technical Information Report SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN Weston Heights North Technical Information Report Conveyance System Analysis and Design The project is proposing to tie into the Weston Heights conveyance systems. A new conveyance system will be installed beneath the sidewalk along the Nile Ave NE frontage improvements. An existing conveyance system is located at the curb line, restricting the location of the proposed conveyance system. Shallow inlets will be installed at the curb line and will tightlined back to catch basins beneath the sidewalk. The system will tie into the Weston Heights system at the intersection of the Weston Heights developments’ roadway and Nile Ave NE. Yard drains, installed in Lots 3 – 6 will be tightlined to a conveyance system along the private drive on the east basin. The new conveyance system will then tie into the Weston Heights conveyance system, also along the private drive. Yard drains will be installed on Lot 2, and the roof downspout of Lot 3 will be connected to an existing conveyance system along NE 7th Pl. This conveyance will tie into the Olympus Villa conveyance system, directing this runoff into Pond ‘A’. The KCSWDM requires that the conveyance flows tributary to each catch basin be calculated with KCRTS using 15-minute timesteps. The KCRTS also requires that the 25-year peak design flows be contained within the conveyance system with no surcharge. The 100-year peak design flows must also be analyzed, and it must be demonstrated that any surcharge during the 100-year peak design event must not cause or aggravate a flooding problem. Conveyance calculations for this project are provided in Appendix 5A. For simplicity of the calculation, and in order to provide a conservative design, the calculations only analyze the 100-year storm event, and show that there is no surcharge during that event. Weston Heights North Technical Information Report APPENDIX 5A CONVEYANCE CALCULATIONS Weston Heights North Technical Information Report Conveyance Calculations to be provided for final review. Weston Heights North Technical Information Report SECTION 6 SPECIAL REPORTS AND STUDIES Weston Heights North Technical Information Report Special Reports and Studies A geotechnical report was prepared by The Riley Group, Inc. for the project on January 29th, 2015. A copy of this report is included in Appendix 6A. A copy of the Olympus Villa LUA 10-090 TIR has been attached as Appendix 6B. The Olympus Villa Pond ‘A’ was utilized as part of this project. A copy of the Olympus Villa original design and As-Built plans has been attached as Appendix 6C. The Olympus Villa Pond ‘A’ was utilized as part of this project. Weston Heights North Technical Information Report APPENDIX 6A GEOTECHNICAL REPORT Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311 www.riley-group.com GEOTECHNICAL ENGINEERING REPORT PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011 PREPARED FOR: WESTON HEIGHTS, LLC 15 LAKE BELLEVUE DRIVE, SUITE 102 BELLEVUE, WASHINGTON 98005 RGI PROJECT NO. 2016-009 WESTON NORTH 702 NILE AVENUE NORTHEAST RENTON, WASHINGTON JANUARY 29, 2016 Geotechnical Engineering Report i January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................................... 1 2.0 PROJECT DESCRIPTION ............................................................................................................... 1 3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1 3.1 FIELD EXPLORATION ................................................................................................................................... 1 3.2 LABORATORY TESTING ................................................................................................................................ 2 4.0 SITE CONDITIONS ........................................................................................................................... 2 4.1 SURFACE .................................................................................................................................................. 2 4.2 GEOLOGY ................................................................................................................................................. 2 4.3 SOILS ....................................................................................................................................................... 3 4.4 GROUNDWATER ........................................................................................................................................ 3 4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3 4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4 5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4 5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4 5.2 EARTHWORK ............................................................................................................................................. 4 5.2.1 Erosion and Sediment Control ..................................................................................................... 4 5.2.2 Stripping ....................................................................................................................................... 5 5.2.3 Excavations................................................................................................................................... 6 5.2.4 Site Preparation ........................................................................................................................... 6 5.2.5 Structural Fill ................................................................................................................................ 7 5.2.6 Cut and Fill Slopes ........................................................................................................................ 8 5.2.7 Wet Weather Construction Considerations ................................................................................. 8 5.3 FOUNDATIONS .......................................................................................................................................... 9 5.4 RETAINING WALLS ................................................................................................................................... 10 5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10 5.6 DRAINAGE .............................................................................................................................................. 11 5.6.1 Surface ....................................................................................................................................... 11 5.6.2 Subsurface .................................................................................................................................. 11 5.6.3 Infiltration .................................................................................................................................. 11 5.7 UTILITIES ................................................................................................................................................ 11 5.8 PAVEMENTS ............................................................................................................................................ 11 6.0 ADDITIONAL SERVICES .............................................................................................................. 12 7.0 LIMITATIONS ................................................................................................................................. 12 LIST OF FIGURES AND APPENDICES Figure 1 ..................................................................................................................... Site Vicinity Map Figure 2 ............................................................................................... Geotechnical Exploration Plan Figure 3 ...................................................................................Typical Retaining Wall Drainage Detail Figure 4 ....................................................................................................Typical Footing Drain Detail Appendix A .......................................................................... Field Exploration and Laboratory Testing Geotechnical Engineering Report ii January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 Executive Summary This Executive Summary should be used in conjunction with the entire Geotechnical Engineering Report (GER) for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and the GER must be read in its entirety for a comprehensive understanding of the items contained herein. Section 7.0 should be read for an understanding of limitations. RGI’s geotechnical scope of work included the advancement of 3 hand augers to a maximum depth of 3.5 feet below existing site grades. Based on the information obtained from our subsurface exploration, the site is suitable for development of the proposed project. The following geotechnical considerations were identified: Soil Conditions: The soils encountered during field exploration includes soft to medium stiff silt with some sand and medium dense silty sand with some gravel . Groundwater: Light groundwater seepage was encountered between depths of 8 to 18 inches bgs during our subsurface exploration. Foundations: Foundations for the proposed building may be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported on medium dense to dense native soil or structural fill. Pavements: The following pavement sections are recommended:  For heavy truck traffic areas: 3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock base (CRB)  For general parking areas: 2 inches of HMA over 4 inches of CRB Geotechnical Engineering Report 1 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the Weston North short plat in Renton, Washington. The purpose of this evaluation is to assess subsurface conditions and provide geotechnical recommendations for the construction of single family residences. Our scope of services included field explorations, laboratory testing, engineering analyses, and preparation of this GER. The recommendations in the following sections of this GER are based upon our current understanding of the proposed site development as outlined below. If actual features vary or changes are made, RGI should review them in order to modify our recommendations as required. In addition, RGI requests to review the site grading plan, final design drawings and specifications when available to verify that our project understanding is correct and that our recommendations have been properly interpreted and incorporated into the project design and construction. 2.0 Project description The project site is located at 702 Nile Avenue Northeast in Renton, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by a single family residence with a shop to the west and a grass field to the east of the residence. RGI understands that the parcel will be subdivided into six lots with construction of five new single family residences. The existing residence and shop will remain on Lot 1. Our understanding of the project is based on conversations with the client, and a site plan that was forwarded to us by SDA dated October 24, 2015. At the time of preparing this GER, building plans were not available for our review. Based on our experience with similar construction, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of two to four kips per linear foot, and a series of columns with a maximum load up to 20 kips. Slab-on-grade floor loading of 250 pounds per square foot (psf) are expected. 3.0 Field Exploration and Laboratory Testing 3.1 FIELD EXPLORATION On January 22, 2016, RGI excavated three hand augers. The approximate exploration locations are shown on Figure 2. Field logs of each exploration were prepared by the geologist that completed the excavation. These logs included visual classifications of the materials encountered during excavation. The hand augers logs included in Appendix A represent an interpretation of Geotechnical Engineering Report 2 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 the field logs and include modifications based on laboratory observation and analysis of the samples. 3.2 LABORATORY TESTING During the field exploration, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination. Selected samples retrieved from the hand augers were tested for moisture content and grain size analysis, to aid in soil classification and provide input for the recommendations provided in this GER. The results and descriptions of the laboratory tests are enclosed in Appendix A. 4.0 Site Conditions 4.1 SURFACE The subject site is a rectangular-shaped parcel of land approximately 2.3 acres in size. The site is bound to the north by Northeast 7th Place, to the east by residential property and a private road, to the south by a wetland and residential properties, and to the west by Nile Avenue Northeast. The existing site houses a shop and a single family residence that are located within the western section of the site. A handful of trees are located along the western portion of the south property line with a cluster of 20 foot tall bamboo stalks to the northeast of the house. The remaining area (central to eastern portion of the site) is occupied by a large grassy field, where the proposed new single family residences would be constructed. The site is relatively flat with an overall elevation difference of approximately 6 feet, increasing in elevation towards the east. 4.2 GEOLOGY Review of the Geologic Map of the Renton Quadrangle King County, Washington, by D.R. Mullineaux, (1965) indicates that the soil in the project vicinity is mapped as Ground moraine deposits (Qgt), which is mostly thin ablation till over lodgment till, deposited by Puget glacial lobe. Lodgment till generally compact, coherent, unsorted mixture of sand, silt, clay and gravel: commonly termed hardpan. Ablation till similar, but much less compact and coherent. Highly variable in thickness and in relative proportion of lodgment to ablation till; lodgment till generally 5 to 30 feet thick, ablation till 2 to 10 feet. North of Cedar River, till is mostly sand, is relatively friable and locally less than 5 feet thick. Between Renton and Lake Youngs, lodgment till locally is thin, but ablation till is relatively thick and grades to stratified drift. Moderately drumlinized, forms undulating, locally irregular surface characterized by southeast-ward-trending hills and swales, commonly overlain by thin sand, clay or peat. Surface drainage is locally poor. Lodgment till is nearly impermeable and relatively difficult to excavate, but relatively stable in cut slopes. These descriptions are generally similar to the findings in our field explorations. Geotechnical Engineering Report 3 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 4.3 SOILS The soils encountered during field exploration include silt with some sand to silty sand with some gravel. Hand auger locations HA-2 and HA-3 encountered dense to very dense soils that contained large gravels and cobbles that prevented further advancement in depth. More detailed descriptions of the subsurface conditions encountered are presented in the hand auger logs included in Appendix A. Sieve analysis was performed on two selected soil samples. Grain size distribution curves are included in Appendix A. 4.4 GROUNDWATER Light groundwater seepage was encountered between 8 to 18 inches bgs during our subsurface exploration. The groundwater appears to be perched over the top of a medium stiff SILT layer. Surface water was also observed in the grassy field during the exploration. It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the explorations were performed. In addition, perched water can develop within seams and layers contained in fill soils or higher permeability soils overlying less permeable soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels during construction or at other times in the future may be higher or lower than the levels indicated on the logs. Groundwater level fluctuations should be considered when developing the design and construction plans for the project. 4.5 SEISMIC CONSIDERATIONS Based on the 2012 International Building Code (IBC), RGI recommends the follow seismic parameters for design. Table 1 2012 IBC Parameter Value Site Soil Class1 C2 Site Latitude 47.494016o N Site Longitude 122.141161o W Short Period Spectral Response Acceleration, SS (g) 1.387 1-Second Period Spectral Response Acceleration, S1 (g) 0.521 Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.387 Adjusted 1-Second Period Spectral Response Acceleration, SM1 (g) 0.677 1. Note: In general accordance with Chapter 20 of ASCE 7. The Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. Geotechnical Engineering Report 4 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 2. Note: The 2012 IBC and ASCE 7 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Hand augers extended to a maximum depth of 3.5 feet, and this seismic site class definition considers that very dense soil continues below the maximum depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations from a seismic event. Liquefaction mainly affects geologically recent deposits of fine-grained sands that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength. RGI reviewed the results of the field and laboratory testing and assessed the potential for liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacial till, RGI considers that the possibility of liquefaction during an earthquake is minimal. 4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the definitions in the Renton Municipal Code, the site does not contain geologically hazardous areas. There are not mapped coal mine hazards, steep slopes or landslide hazard on the site or in the near vicinity of the site. A wetland is mapped on the parcel to the south of the site and appears to extend slightly into the site. 5.0 Discussion and Recommendations 5.1 GEOTECHNICAL CONSIDERATIONS Based on our study, the site is suitable for the proposed construction from a geotechnical standpoint. Foundations for the proposed building can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Slab-on- grade and pavements can be similarly supported. Detailed recommendations regarding the above issues and other geotechnical design considerations are provided in the following sections. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 EARTHWORK The earthwork is expected to include installing underground utilities excavating and backfilling the residence foundations and preparing sidewalk, driveway and frontage improvement roadway subgrades. 5.2.1 EROSION AND SEDIMENT CONTROL Potential sources or causes of erosion and sedimentation depend on construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, Geotechnical Engineering Report 5 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 construction sequencing and weather. The impacts on erosion-prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. RGI recommends the following erosion control Best Management Practices (BMPs):  Scheduling site preparation and grading for the drier summer and early fall months and undertaking activities that expose soil during periods of little or no rainfall  Retaining existing vegetation whenever feasible  Establishing a quarry spall construction entrance  Installing siltation control fencing or anchored straw or coir wattles on the downhill side of work areas  Covering soil stockpiles with anchored plastic sheeting  Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw if surfaces will be left undisturbed for more than one day during wet weather or one week in dry weather  Directing runoff away from exposed soils and slopes  Minimizing the length and steepness of slopes with exposed soils and cover excavation surfaces with anchored plastic sheeting (Graded and disturbed slopes should be tracked in place with the equipment running perpendicular to the slope contours so that the track marks provide a texture to help resist erosion and channeling. Some sloughing and raveling of slopes with exposed or disturbed soil should be expected.)  Decreasing runoff velocities with check dams, straw bales or coir wattles  Confining sediment to the project site  Inspecting and maintaining erosion and sediment control measures frequently (The contractor should be aware that inspection and maintenance of erosion control BMPs is critical toward their satisfactory performance. Repair and/or replacement of dysfunctional erosion control elements should be anticipated.) Permanent erosion protection should be provided by reestablishing vegetation using hydroseeding and/or landscape planting. Until the permanent erosion protection is established, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 5.2.2 STRIPPING Stripping efforts should include removal of pavements, vegetation, organic materials, and deleterious debris from areas slated for building, pavement, and utility construction. The hand augers encountered eight to 14 inches of topsoil and rootmass. Deeper areas of stripping may be required in forested or heavily vegetated areas of the site. Geotechnical Engineering Report 6 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. The site soils consist of dense native soils. Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary side slopes should be laid back with a minimum slope inclination of 1.5H:1V (Horizontal:Vertical) where groundwater seepage is encountered and 3/4H:1V in the underlying dense soils. If there is insufficient room to complete the excavations in this manner, or excavations greater than 20 feet in depth are planned, using temporary shoring to support the excavations should be considered. For open cuts at the site, RGI recommends:  No traffic, construction equipment, stockpiles or building supplies are allowed at the top of cut slopes within a distance of at least five feet from the top of the cut  Exposed soil along the slope is protected from surface erosion using waterproof tarps and/or plastic sheeting  Construction activities are scheduled so that the length of time the temporary cut is left open is minimized  Surface water is diverted away from the excavation  The general condition of slopes should be observed periodically by a geotechnical engineer to confirm adequate stability and erosion control measures In all cases, however, appropriate inclinations will depend on the actual soil and groundwater conditions encountered during earthwork. Ultimately, the site contractor must be responsible for maintaining safe excavation slopes that comply with applicable OSHA or WISHA guidelines. 5.2.4 SITE PREPARATION Once stripping, clearing and other preparing operations are complete, the footings should be excavated into the native soils. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond that which would be expected during the drier summer and fall months. Geotechnical Engineering Report 7 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 5.2.5 STRUCTURAL FILL RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is that moisture that results in the greatest compacted dry density with a specified compactive effort. Non-organic site soils are only considered suitable for structural fill provided that their moisture content is within about two percent of the optimum moisture level as determined by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill depending on the moisture content and weather conditions at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be protected with plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning (such as, windrowing and drying) of site soils to be reused as structural fill may be required. Even during the summer, delays in grading can occur due to excessively high moisture conditions of the soils or due to precipitation. If wet weather occurs, the upper wetted portion of the site soils may need to be scarified and allowed to dry prior to further earthwork, or may need to be wasted from the site. The native soils were over the optimum moisture content during our explorations. The native soils may require moisture conditioning even in the drier summer months. If on- site soils are or become unusable or earthwork will be completed in wet weather, it may become necessary to import clean, granular soils to complete site work that meet the grading requirements listed in Table 2 to be used as structural fill. Table 2 Structural Fill Gradation U.S. Sieve Size Percent Passing 4 inches 100 No. 4 sieve 75 percent No. 200 sieve 5 percent * *Based on minus 3/4 inch fraction. Geotechnical Engineering Report 8 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 Prior to use, an RGI representative should observe and test all materials imported to the site for use as structural fill. Structural fill materials should be placed in uniform loose layers not exceeding 12 inches and compacted as specified in Table 2. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Table 3 Structural Fill Compaction ASTM D1557 Location Material Type Minimum Compaction Percentage Moisture Content Range Foundations On-site granular or approved imported fill soils: 95 +2 -2 Retaining Wall Backfill On-site granular or approved imported fill soils: 92 +2 -2 Slab-on-grade On-site granular or approved imported fill soils: 95 +2 -2 General Fill (non- structural areas) On-site soils or approved imported fill soils: 90 +3 -2 Pavement – Subgrade and Base Course On-site granular or approved imported fill soils: 95 +2 -2 Placement and compaction of structural fill should be observed by RGI. A representative number of in-place density tests should be performed as the fill is being placed to confirm that the recommended level of compaction is achieved. 5.2.6 CUT AND FILL SLOPES All permanent cut and fill slopes (except interior slopes of detention pond) should be graded with a finished inclination no greater than 2H:1V. The interior slopes of the detention pond must be graded with a slope gradient no steeper than 3H:1V. Upon completion of construction, the slope face should be trackwalked, compacted and vegetated, or provided with other physical means to guard against erosion. Final grades at the top of the slopes must promote surface drainage away from the slope crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If it is necessary to direct surface runoff towards the slope, it should be controlled at the top of the slope, piped in a closed conduit installed on the slope face, and taken to an appropriate point of discharge beyond the toe of the slope. All fill placed for slope construction should meet the structural fill requirements as described in Section 5.2.5. 5.2.7 WET WEATHER CONSTRUCTION CONSIDERATIONS RGI recommends that preparation for site grading and construction include procedures intended to drain ponded water, control surface water runoff, and to collect shallow subsurface seepage zones in excavations where encountered. It will not be possible to Geotechnical Engineering Report 9 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 successfully compact the subgrade or utilize on-site soils as structural fill if accumulated water is not drained prior to grading or if drainage is not controlled during construction. Attempting to grade the site without adequate drainage control measures will reduce the amount of on-site soil effectively available for use, increase the amount of select import fill materials required, and ultimately increase the cost of the earthwork phases of the project. Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will be required for surface water control during wet weather and/or wet site conditions. 5.3 FOUNDATIONS Following site preparation and grading, the proposed residence foundations can be supported on conventional spread footings bearing on medium dense to dense native soil or structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed building footprint. If unsuitable soils are encountered, they should be overexcavated and backfilled with structural fill. Perimeter foundations exposed to weather should be at a minimum depth of 18 inches below final exterior grades. Interior foundations can be constructed at any convenient depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation for perimeter (or exterior) footings and finished floor level for interior footings. Table 4 Foundation Design Design Parameter Value Allowable Bearing Capacity - Structural Fill Dense native soils 2,500 psf1 4,000 psf Friction Coefficient 0.30 Passive pressure (equivalent fluid pressure) 250 pcf2 Minimum foundation dimensions Columns: 24 inches Walls: 16 inches 1. psf = pounds per square foot 2. pcf = pounds per cubic foot The allowable foundation bearing pressures apply to dead loads plus design live load conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable capacity may be used. At perimeter locations, RGI recommends not including the upper 12 inches of soil in the computation of passive pressures because they can be affected by weather or disturbed by future grading activity. The passive pressure value assumes the foundation will be constructed neat against competent soil or backfilled with Geotechnical Engineering Report 10 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 structural fill as described in Section 5.2.5. The recommended base friction and passive resistance value includes a safety factor of about 1.5. With spread footing foundations designed in accordance with the recommendations in this section, maximum total and differential post-construction settlements of 1 inch and 1/2 inch, respectively, should be expected. 5.4 RETAINING WALLS If retaining walls are needed for the residences, RGI recommends cast-in-place concrete walls be used. The magnitude of earth pressure development on retaining walls will partly depend on the quality of the wall backfill. RGI recommends placing and compacting wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown in Figure 3. With wall backfill placed and compacted as recommended, and drainage properly installed, RGI recommends using the values in the following table for design. Table 5 Retaining Wall Design Design Parameter Value Allowable Bearing Capacity - Structural Fill Dense native soils 2,500 psf 4,000 psf Active Earth Pressure (unrestrained walls) 35 pcf At-rest Earth Pressure (restrained walls) 50 pcf For seismic design, an additional uniform load of 7 times the wall height (H) for unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.3. 5.5 SLAB-ON-GRADE CONSTRUCTION Once site preparation has been completed as described in Section 5.2, suitable support for slab-on-grade construction should be provided. RGI recommends that the concrete slab be placed on top of medium dense native soil or structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed on a 4-inch thick layer of clean gravel. Geotechnical Engineering Report 11 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 For the anticipated floor slab loading, we estimate post-construction floor settlements of 1/4- to 1/2-inch. For thickness design of the slab subjected to point loading from storage racks, RGI recommends using a subgrade modulus (KS) of 150 pounds per square inch per inch of deflection. 5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the residences. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. For non-pavement locations, RGI recommends providing a minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the building perimeter. In paved locations, a minimum gradient of 1 percent should be provided unless provisions are included for collection and disposal of surface water adjacent to the structure. 5.6.2 SUBSURFACE RGI recommends installing perimeter foundation drains. A typical footing drain detail is shown on Figure 4. The foundation drains and roof downspouts should be tightlined separately to an approved discharge facility. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. 5.6.3 INFILTRATION Infiltration is not feasible on the site due to the presence of nearly impermeable soils and shallow groundwater conditions. 5.7 UTILITIES Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. For site utilities located within the right-of-ways, bedding and backfill should be completed in accordance with City of Renton specifications. At a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2.5. Where utilities occur below unimproved areas, the degree of compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as determined by the referenced ASTM D1557. As noted, soils excavated on site may not be suitable for use as backfill material. Imported structural fill meeting the gradation provided in Table 2 may be necessary for trench backfill. 5.8 PAVEMENTS Pavement subgrades should be prepared as described in Section 5.2 and as discussed below. Regardless of the relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade should be proofrolled with heavy construction equipment to verify this condition. Geotechnical Engineering Report 12 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 With the pavement subgrade prepared as described above, RGI recommends the following pavement sections for parking and drive areas paved with flexible asphalt concrete surfacing.  For heavy truck traffic areas: 3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock base (CRB)  For general parking areas: 2 inches of HMA over 4 inches of CRB The asphalt paving materials used should conform to the Washington State Department of Transportation (WSDOT) specifications for HMA and CRB surfacing. Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their supporting capability. For optimum pavement performance, surface drainage gradients of no less than 2 percent are recommended. Also, some degree of longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. 6.0 Additional Services RGI is available to provide further geotechnical consultation throughout the design phase of the project. RGI should review the final design and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and incorporated into project design and construction. RGI is also available to provide geotechnical engineering and construction monitoring services during construction. The integrity of the earthwork and construction depends on proper site preparation and procedures. In addition, engineering decisions may arise in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this scope of work. If these services are desired, please let us know and we will prepare a cost proposal. 7.0 Limitations This GER is the property of RGI, Weston Heights, LLC, and its designated agents. Within the limits of the scope and budget, this GER was prepared in accordance with generally accepted geotechnical engineering practices in the area at the time this GER was issued. This GER is intended for specific application to the Weston North project in Renton, Washington, and for the exclusive use of Weston Heights, LLC and its authorized representatives. No other warranty, expressed or implied, is made. Site safety, excavation support, and dewatering requirements are the responsibility of others. The scope of services for this project does not include either specifically or by implication any environmental or biological (for example, mold, fungi, bacteria) assessment of the Geotechnical Engineering Report 13 January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, we can provide a proposal for these services. The analyses and recommendations presented in this GER are based upon data obtained from the test exploration performed on site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, RGI should be requested to reevaluate the recommendations in this GER prior to proceeding with construction. It is the client’s responsibility to see that all parties to the project, including the designers, contractors, subcontractors, are made aware of this GER in its entirety. The use of information contained in this GER for bidding purposes should be done at the contractor’s option and risk. USGS, 2014, Mercer Island, Washington USGS, 2014, Renton, Washington 7.5-Minute Quadrangle Approximate Scale: 1"=1000' 0 500 1000 2000 N Site Vicinity Map Figure 1 01/2016 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Weston North RGI Project Number 2016-009 Date Drawn: Address: 702 Nile Avenue Northeast, Renton, Washington 98059 SITE HA-1HA-2HA-301/2016Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Weston NorthRGI Project Number2016-009Date Drawn:Address: 702 Nile Avenue Northeast, Renton, Washington 98059Geotechnical Exploration PlanFigure 2Approximate Scale: 1"=80'04080160N = HA-1 to HA-3 excavated by RGI, 1/22/16Drawn from Roadway and Drainage Plan by SDA, Civil Engineers Incliniations) 12" Over the Pipe 3" Below the Pipe Perforated Pipe 4" Diameter PVC Compacted Structural Backfill (Native or Import) 12" min. Filter Fabric Material 12" Minimum Wide Free-Draining Gravel Slope to Drain (See Report for Appropriate Excavated Slope 01/2016 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Weston North RGI Project Number 2016-009 Date Drawn: Address: 702 Nile Avenue Northeast, Renton, Washington 98059 Retaining Wall Drainage Detail Figure 3 Not to Scale 3/4" Washed Rock or Pea Gravel 4" Perforated Pipe Building Slab Structural Backfill Compacted Filter Fabric 01/2016 Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone: 425.415.0551 Fax: 425.415.0311 Weston North RGI Project Number 2016-009 Date Drawn: Address: 702 Nile Avenue Northeast, Renton, Washington 98059 Typical Footing Drain Detail Figure 4 Not to Scale Geotechnical Engineering Report January 29, 2016 Weston North, Renton, Washington RGI Project No. 2016-009 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On January 22, 2016, RGI performed field explorations using a hand auger. We explored subsurface soil conditions at the site by excavating three hand augers to a maximum depth of 3.5 feet below existing grade. The hand augers locations are shown on Figure 2. The hand augers locations were approximately determined by measurements from existing property lines and paved roads. A geologist from our office conducted the field exploration and classified the soil conditions encountered, maintained a log of each test exploration, obtained representative soil samples, and observed pertinent site features. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS). Representative soil samples obtained from the explorations were placed in closed containers and taken to our laboratory for further examination and testing. As a part of the laboratory testing program, the soil samples were classified in our in house laboratory based on visual observation, texture, plasticity, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with ASTM D2216-10 Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration in order to aid in identification and correlation of soil types. The moisture content of typical sample was measured and is reported on the hand augers logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on two of the samples. THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Weston North SAMPLE ID/TYPE HA-1 S-3 PROJECT NO.2016-009 SAMPLE DEPTH 3.5' TECH/TEST DATE PL 1/22/2106 DATE RECEIVED 1/22/2016 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)347.8 Weight Of Sample (gm)268.5 Wt Dry Soil & Tare (gm)(w2)268.5 Tare Weight (gm) 8.5 Weight of Tare (gm)(w3)8.5 (W6) Total Dry Weight (gm)260.0 Weight of Water (gm)(w4=w1-w2)79.3 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)260.0 Cumulative Moisture Content (%) (w4/w5)*100 31 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"8.5 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"8.5 0.00 0.00 100.00 coarse gravel % F GRAVEL 1.3 2.5" coarse gravel % C SAND 2.7 2.0" coarse gravel % M SAND 6.7 1.5"8.5 0.00 0.00 100.00 coarse gravel % F SAND 6.5 1.0" coarse gravel % FINES 82.8 0.75"8.5 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"8.5 0.00 0.00 100.00 fine gravel D10 (mm)#4 11.8 3.30 1.27 98.73 coarse sand D30 (mm)#10 18.8 10.30 3.96 96.04 medium sand D60 (mm)#20 medium sand Cu #40 36.1 27.60 10.62 89.38 fine sand Cc #60 fine sand #100 47.4 38.90 14.96 85.04 fine sand #200 53.1 44.60 17.15 82.85 fines PAN 268.5 260.00 100.00 0.00 silt/clay DESCRIPTION SILT with some sand USCS ML Prepared For:Reviewed By:KMW Weston Heights, LLC 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 THE RILEY GROUP, INC. 17522 Bothell Way NE Bothell, WA 98011 PHONE: (425) 415-0551 FAX: (425) 415-0311 GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913 PROJECT TITLE Weston North SAMPLE ID/TYPE HA-2 S-2 PROJECT NO.2016-009 SAMPLE DEPTH 2' TECH/TEST DATE PL 1/22/2106 DATE RECEIVED 1/22/2016 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1)322.0 Weight Of Sample (gm)238.0 Wt Dry Soil & Tare (gm)(w2)238.0 Tare Weight (gm) 8.4 Weight of Tare (gm)(w3)8.4 (W6) Total Dry Weight (gm)229.6 Weight of Water (gm)(w4=w1-w2)84.0 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3)229.6 Cumulative Moisture Content (%) (w4/w5)*100 37 Wt Ret (Wt-Tare) (%Retained)% PASS +Tare {(wt ret/w6)*100}(100-%ret) % COBBLES 0.0 12.0"8.4 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0"8.4 0.00 0.00 100.00 coarse gravel % F GRAVEL 15.4 2.5" coarse gravel % C SAND 11.7 2.0" coarse gravel % M SAND 13.9 1.5"8.4 0.00 0.00 100.00 coarse gravel % F SAND 21.6 1.0" coarse gravel % FINES 37.4 0.75"8.4 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375"17.6 9.20 4.01 95.99 fine gravel D10 (mm)#4 43.8 35.40 15.42 84.58 coarse sand D30 (mm)#10 70.7 62.30 27.13 72.87 medium sand D60 (mm)#20 medium sand Cu #40 102.6 94.20 41.03 58.97 fine sand Cc #60 fine sand #100 133.2 124.80 54.36 45.64 fine sand #200 152.1 143.70 62.59 37.41 fines PAN 238.0 229.60 100.00 0.00 silt/clay DESCRIPTION Silty SAND with some gravel USCS SM Prepared For:Reviewed By:KMW Weston Heights, LLC 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.11101001000 % P A S S I N G Grain size in millimeters 12"3"2"1".75".375"#4 #10 #20 #40 #60 #100 #200 Weston Heights North Technical Information Report APPENDIX 6B OLYMPUS VILLA LUA 10-090 Weston Heights North Technical Information Report APPENDIX 6C OLYMPUS VILLA AS-BUILT PLANS Weston Heights North Technical Information Report SECTION 7 OTHER PERMITS Weston Heights North Technical Information Report Other Permits This project will require the following permits: Grading Permit - City of Renton Right-of-Way Use Permit - City of Renton Construction Stormwater Permit - WA Dept. of Ecology Weston Heights North Technical Information Report SECTION 8 CSWPPP ANALYSIS AND DESIGN Weston Heights North Technical Information Report ESC Plan Analysis and Design This section, along with the Temporary Erosion and Sediment Control (TESC) Plan contained in the engineering drawings, is intended to serve as the construction Stormwater Pollution Prevention Plan (SWPPP) for the project. The SWPPP is outlined in conformance with the 2005 edition of the Washington State Department of Ecology’s Stormwater Management Manual for Western Washington (DOE Manual). 1.0 – INTRODUCTION An introductory overview of the project has been provided in the Project Overview section of this report. 2.0 – SITE DESCRIPTION A general site description has been provided in the Project Overview section of this report. Additional detailed information is provided through the rest of this report. 3.0 – CONSTRUCTION STORMWATER BMPs 3.1 – 12 BMP ELEMENTS Element #1 – Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing limits are identified in Appendix 8B. Alternate BMPs for marking clearing limits are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. Element #2 – Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. All wash wastewater shall be controlled on site. The specific BMPs related to establishing construction access that will be used on this project are identified in Appendix 8B. Alternate construction access BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. Weston Heights North Technical Information Report Element #3 - Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. The specific BMPs for flow control that shall be used on this project are identified in Appendix 8B. Alternate flow control BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit. To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements (e.g. discharge to combined sewer systems). Element #4 - Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged to an infiltration facility. The specific BMPs to be used for controlling sediment on this project are identified in Appendix 8B. Alternate sediment control BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs at the first sign that existing BMPs are ineffective or failing. In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize wash off of sediments from adjacent streets in runoff. Whenever possible, sediment laden water shall be discharged into onsite, relatively level, vegetated areas (BMP C240 paragraph 4, Volume II page 116). In some cases, sediment discharge in concentrated runoff can be controlled using permanent stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment loads can limit the effectiveness of some permanent stormwater BMPs, such as those used for infiltration or biofiltration; however, those BMPs designed to remove solids by settling (wet ponds or detention ponds) can be used during the construction phase. When permanent stormwater BMPs will be used to control sediment discharge during construction, the structure will be protected from excessive sedimentation with adequate erosion and sediment control BMPs. Any accumulated sediment shall be removed after construction is complete and the permanent stormwater BMP will be restabilized with vegetation per applicable design requirements once the remainder of the site has been stabilized. Weston Heights North Technical Information Report Element #5 - Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project are identified in Appendix 8B. Seeding will be used on disturbed areas that have reached final grade or that will remain unworked for more than thirty days. Plastic Covering will be used on the temporary stock pile areas and elsewhere on the site as needed. Dust control will be implemented as needed, to prevent it being required all roadways and driveways to be paved will receive early application of gravel base. Alternate soil stabilization BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and unworked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet season (October 1 to April 30). Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. Element #6 - Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes erosion. The specific BMPs that will be used to protect slopes for this project are identified in Appendix 8B. Alternate slope protection BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. Element #7 - Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. The inlet protection measures to be applied on this project are identified in Appendix 8B. Weston Heights North Technical Information Report If the primary BMP options are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D), or if no BMPs are listed above but deemed necessary during construction, the Certified Erosion and Sediment Control Lead shall implement one or more of the alternative BMP inlet protection options. Element #8 - Stabilize Channels and Outlets Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. The specific BMPs for channel and outlet stabilization that shall be used on this project are identified in Appendix 8B. Alternate channel and outlet stabilization BMPs are included in Appendix 8C as a quick reference tool for the onsite inspector in the event the primary BMP(s) are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix 8D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest. As such, all temporary on- site conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate indicated by an approved continuous runoff simulation model, increased by a factor of 1.6, shall be used. Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches shall be provided at the outlets of all conveyance systems. Element #9 - Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. Any required BMPs to be implemented to control specific sources of pollutants are identified in Appendix 8B. The contractor shall implement the following measures as much as is practicable, in order to mitigate pollutant impacts from vehicles, construction equipment, and/or petroleum product storage/dispensing:  All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills.  On-site fueling tanks and petroleum product storage containers shall include secondary containment.  Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment.  In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle. Weston Heights North Technical Information Report  Contaminated surfaces shall be cleaned immediately following any discharge or spill incident.  The contractor shall implement the following concrete and grout pollution control measures:  Process water and slurry resulting from concrete work will be prevented from entering the waters of the State by implementing Concrete Handling measures (BMP C151). The contractor shall implement the following Solid Waste pollution control measures:  Solid waste will be stored in secure, clearly marked containers. Element #10 - Control Dewatering Foundation, vault, and trench de-watering water, which shall have similar characteristics to stormwater runoff at the site, shall be discharged into a controlled conveyance system prior to discharge to a sediment trap, pond, or other specified facility. Channels must be stabilized as specified in Element #8. Clean, non-turbid de-watering water, such as well-point groundwater, can be discharged to systems tributary to state surface waters, provided the de-watering flow does not cause erosion or flooding of receiving waters. These clean waters should not be routed through stormwater sediment ponds. Highly turbid or contaminated dewatering water shall be handled separately from stormwater. Element #11 - Maintain BMPs All BMPs should be monitored and maintained regularly to ensure adequate operation. A TESC supervisor shall be identified at the beginning of the project to provide monitoring and direct the appropriate maintenance activity. As site conditions change, all BMPs shall be updated as necessary to maintain compliance with local regulations. Temporary BMPs can be removed when they are no longer needed. All temporary erosion and sediment control BMPs shall be removed within 30 days after construction is completed and the site is stabilized. Element #12 - Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles:  Design the project to fit the existing topography, soils, and drainage patterns.  Emphasize erosion control rather than sediment control.  Minimize the extent and duration of the area exposed.  Keep runoff velocities low.  Retain sediment on site.  Thoroughly monitor site and maintain all ESC measures. Weston Heights North Technical Information Report  Schedule major earthwork during the dry season. As this project site is located west of the Cascade Mountain Crest, the project will be managed according to the following key project components: Phasing of Construction  The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible, the transport of sediment from the site during construction.  Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities during each phase of construction, per the Scheduling BMP (C 162). Seasonal Work Limitations  From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt- laden runoff will be prevented from leaving the site through a combination of the following: o Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and o Limitations on activities and the extent of disturbed areas; and o Proposed erosion and sediment control measures.  Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance.  The following activities are exempt from the seasonal clearing and grading limitations: o Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and o Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. Coordination with Utilities and Other Jurisdictions  Care has been taken to coordinate with utilities, other construction projects, and the local jurisdiction in preparing this SWPPP and scheduling the construction work. Inspection and Monitoring  All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: o Assess the site conditions and construction activities that could impact the quality of stormwater, and o Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. Weston Heights North Technical Information Report  A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times.  Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. Maintaining an Updated Construction SWPPP  This SWPPP shall be retained on-site or within reasonable access to the site.  The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state.  The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. 3.2 – SITE SPECIFIC BMPs Site specific BMPs are shown on the TESC plan sheet(s) in Appendix 8A. 4.0 – CONSTRUCTION PHASING AND BMP IMPLEMENTATION The BMP implementation schedule will be driven by the construction schedule. The list below provides an estimate of the anticipated construction schedule. The project site is located west of the Cascade Mountain Crest. As such, the dry season is considered to be from May 1 to September 30, and the wet season is considered to be from October 1 to April 30. 5.0 – POLLUTION PREVENTION TEAM 5.1 ROLES AND RESPONSIBILITIES The pollution prevention team consists of personnel responsible for implementation of the SWPPP, including the following:  Certified Erosion and Sediment Control Lead (CESCL) – primary contractor contact, responsible for site inspections (BMPs, visual monitoring, sampling, etc.); to be called upon in case of failure of any ESC measures.  Resident Engineer – For projects with engineered structures only (sediment ponds/traps, sand filters, etc.): Site representative for the owner that is the project’s supervising engineer responsible for inspections and issuing instructions and drawings to the contractor’s site supervisor or representative.  Emergency Ecology Contact – Individual to be contacted at Ecology in case of emergency.  Emergency Owner Contact – Individual that is the site owner or representative of the site owner to be contacted in the case of an emergency.  Non-Emergency Ecology Contact – Individual that is the site owner or representative of the site owner that can be contacted if required. Weston Heights North Technical Information Report  Monitoring Personnel – Personnel responsible for conducting water quality monitoring; for most sites this person is also the CESCL. 5.2 TEAM MEMBERS Names and contact information for those identified as members of the pollution prevention team are provided in the project summary in Appendix 8B. 6.0 – SITE INSPECTIONS AND MONITORING Monitoring includes visual inspection, monitoring for water quality parameters of concern, and documentation of the inspection and monitoring findings in a site log book. A site log book will be maintained for all on-site construction activities and will include:  A record of the implementation of the SWPPP and other permit requirements;  Site inspections; and,  Stormwater quality monitoring. For convenience, the inspection forma and water quality monitoring forms included in Appendix 8E of this report include the required information for the site log book. This SWPPP may function as the site log book, if desired, or the forms may be separated and included in a separate site log book. However, if separated, the site log book must be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 6.1 SITE INSPECTION All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead (CESCL) per BMP C160. The name and contact information for the CESCL is provided in Section 5 of this SWPPP. Site inspection will occur in all areas disturbed by construction activities and at all stormwater discharge points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be documented in the site log book or forms provided in this document. All new BMPs or design changes will be documented in the SWPPP as soon as possible. 6.1.1 Site Inspection Frequency Site inspections will be conducted at least once a week and within 24 hours following any rainfall event which causes a discharge of stormwater from the site. For sites with temporary stabilization measures, the site inspection frequency can be reduced to once every month. 6.1.2 Site Inspection Documentation The site inspector will record each site inspection using the site log inspection forms provided in Appendix 8E. The site inspection log forms may be separated from this SWPPP document, but will be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Weston Heights North Technical Information Report 6.2 Stormwater Quality Monitoring 6.2.1 Turbidity Sampling Monitoring requirements for the proposed project will include turbidity sampling to monitor site discharges for water quality compliance with the 2010 Snohomish County Drainage manual and Snohomish County Code Title 30.63A NPDES Construction Stormwater General Permit (Appendix 8D). Sampling will be conducted at all site discharge points at least once per calendar week. Turbidity monitoring will follow the analytical methodologies described in Section S4 of the 2005 Construction Stormwater General Permit (Appendix 8D). The key benchmark values that require action include 25 NTU and 250 NTU for turbidity. If the 25 NTU benchmark for turbidity is exceeded, the following steps will be conducted: 1. Ensure all BMPs specified in this SWPPP are installed and functioning as intended. 2. Assess whether additional BMPs should be implemented and make revisions to the SWPPP as necessary. 3. Sample the discharge location daily until the analysis results are less than 25 NTU (turbidity) or 32 cm (transparency). If the turbidity is greater than 25 NTU but less than 250 NTU for more than 3 days, additional treatment BMPs will be implemented within 24 hours of the third consecutive sample that exceeded the benchmark value. Additional treatment BMPs will include, but are not limited to, off-site treatment, infiltration, filtration and chemical treatment. If the 250 NTU benchmark for turbidity is exceeded at any time, the following steps will be conducted: 1. Notify Ecology by phone within 24 hours of analysis. 2. Continue daily sampling until the turbidity is less than 25 NTU. 3. Initiate additional treatment BMPs such as off-site treatment, infiltration, filtration and chemical treatment within 24 hours of the first 250 NTU exceedance. 4. Implement additional treatment BMPs as soon as possible, but within 7 days of the first 250 NTU exceedance. 5. Describe inspection results and remedial actions that are taken in the site log book and in monthly discharge monitoring reports. 6.2.2 pH Sampling Stormwater runoff will be monitored for pH starting on the first day of any activity that includes more than 40 yards of poured or recycled concrete, or after the application of “Engineered Soils” such as, Portland cement treated base, cement kiln dust, or fly ash. This does not include fertilizers. For concrete work, pH monitoring will start the first day concrete is poured and continue until 3 weeks after the last pour. For engineered soils, the pH monitoring period begins when engineered soils are first exposed to precipitation and continue until the area is fully stabilized. Weston Heights North Technical Information Report Stormwater samples will be collected daily from all points of discharge from the site and measured for pH using a calibrated pH meter, pH test kit, or wide range pH indicator paper. If the measured pH is 8.5 or greater, the following steps will be conducted: 1. Prevent the high pH water from entering storm drains or surface water. 2. Adjust or neutralize the high pH water if necessary using appropriate technology such as CO2 sparging (liquid or dry ice). 3. Contact Ecology if chemical treatment other than CO2 sparging is planned. 7.0 – REPORTING AND RECORDKEEPING 7.1 RECORDKEEPING 7.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include:  A record of the implementation of the SWPPP and other permit requirements;  Site inspections; and,  Stormwater quality monitoring. For convenience, the inspection form and water quality monitoring forms included in Appendix 8E of this report include the required information for the site log book. 7.1.2 Records Retention Records of all monitoring information (site log book, inspection reports/checklists, etc.), this Stormwater Pollution Prevention Plan, and any other documentation of compliance with permit requirements will be retained during the life of the construction project and for a minimum of three years following the termination of permit coverage in accordance with permit condition S5.C. 7.1.3 Access to Plans and Records The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be retained on site or within reasonable access to the site and will be made immediately available upon request to Ecology or the local jurisdiction. A copy of this SWPPP will be provided to Ecology within 14 days of receipt of a written request for the SWPPP from Ecology. Any other information requested by Ecology will be submitted within a reasonable time. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with permit condition S5.G. 7.1.4 Updating the SWPPP In accordance with Conditions S3, S4.B, and S9.B.3 of the General Permit, this SWPPP will be modified if the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site or there has been a change in design, construction, operation, or maintenance at the site that has a significant effect on the discharge, or potential for discharge, of pollutants to the waters of the State. The SWPPP will be modified within seven days of determination based on inspection(s) that Weston Heights North Technical Information Report additional or modified BMPs are necessary to correct problems identified, and an updated timeline for BMP implementation will be prepared. 7.2 REPORTING 7.2.1 Discharge Monitoring Reports Discharge Monitoring Report (DMR) forms will not be submitted to Ecology because water quality sampling is not being conducted at the site. 7.2.2 Notification of Noncompliance If any of the terms and conditions of the permit are not met, and it causes a threat to human health of the environment, the following steps will be taken in accordance with permit section S5.F: 1. Ecology will be immediately notified of the failure to comply. 2. Immediate action will be taken to control the noncompliance issue and to correct the problem. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. In accordance with permit condition S2.A, a complete application form will be submitted to Ecology and the appropriate local jurisdiction (if applicable) to be covered by the General Permit. Weston Heights North Technical Information Report APPENDIX 8A SITE PLAN WITH BMP MEASURES Weston Heights North Technical Information Report APPENDIX 8B SWPPP PROJECT SUMMARY Weston Heights North Technical Information Report PROJECT TEAM MEMBERS: Title Name(s) Phone Number Certified Erosion & Sediment Control Lead To be provided Resident Engineer To be provided Emergency Ecology Contact Puget Sound Office (425) 649-7000 Emergency Owner Contact To be provided Non-Emergency Ecology Contact Northwest Region (425) 649-7000 Monitoring Personnel To be provided ESTIMATED CONSTRUCTION SCHEDULE:  Construction Start Date July 2016  Install ESC Measures July 2016  Construction End Date October 2016 CONSTRUCTION BMP LIST:  Silt Fence (BMP C233)  Storm Drain Inlet Protection (BMP C220)  Materials on Hand (BMP C150) may also be applicable  Detention Pond Or Vault  Temporary and Permanent Seeding (BMP C120)  Plastic Covering (BMP C123)  Interceptor Dike and Swale (BMP C200)  Check Dams (BMP C207) Weston Heights North Technical Information Report APPENDIX 8C ALTERNATIVE BMPs Weston Heights North Technical Information Report The following includes a list of possible alternative BMPs for each of the 12 elements not described in the main SWPPP text. This list can be referenced in the event a BMP for a specific element is not functioning as designed and an alternative BMP needs to be implemented. Element #1 - Mark Clearing Limits  High Visibility Plastic or Metal Fence (BMP C103) Element #2 - Establish Construction Access  Wheel Wash (BMP C106) Element #3 - Control Flow Rates  (none) Element #4 - Install Sediment Controls  Straw Bale Barrier (BMP C230)  Vegetated Strip (BMP C234)  Materials on Hand (BMP C150) Element #5 - Stabilize Soils  Dust Control (BMP C140)  Topsoiling (BMP C125)  Sodding (BMP C124) Element #6 - Protect Slopes  Straw Wattles (BMP C235)  Grass-Lined Channels (BMP C201) Element #7 - Protect Drain Inlets  (none) Element #8 - Stabilize Channels and Outlets  Level Spreader (BMP C206) Element #10 - Control Dewatering  (none) Weston Heights North Technical Information Report APPENDIX 8D GENERAL PERMIT Weston Heights North Technical Information Report Construction Stormwater General Permit A copy of the construction stormwater general permit will be added to this appendix once it is obtained. Weston Heights North Technical Information Report APPENDIX 8E SITE LOG & INSPECTION FORMS Weston Heights North Technical Information Report Site Inspection Forms (and Site Log) The results of each inspection shall be summarized in an inspection report or checklist that is entered into or attached to the site log book. It is suggested that the inspection report or checklist be included in this appendix to keep monitoring and inspection information in one document, but this is optional. However, it is mandatory that this SWPPP and the site inspection forms be kept onsite at all times during construction, and that inspections be performed and documented as outlined below. At a minimum, each inspection report or checklist shall include: a. Inspection date/times b. Weather information: general conditions during inspection, approximate amount of precipitation since the last inspection, and approximate amount of precipitation within the last 24 hours. c. A summary or list of all BMPs that have been implemented, including observations of all erosion/sediment control structures or practices. d. The following shall be noted: i. Locations of BMPs inspected, ii. Locations of BMPs that need maintenance, iii. The reason maintenance is needed iv. Locations of BMPs that failed to operate as designed or intended, and v. Locations where additional or different BMPs are needed, and the reason(s) why. e. A description of stormwater discharged from the site. The presence of suspended sediment, turbid water, discoloration, and/or oil sheen shall be noted, as applicable. f. A description of any water quality monitoring performed during inspection, and the results of that monitoring. g. General comments and notes, including a brief description of any BMP r repairs, maintenance or installations made as a result of the inspection. h. A statement that, in the judgment of the person conducting the site inspection, the site is either in compliance or out of compliance with the terms and conditions of the SWPPP and the NPDES permit. If the site inspection indicates that the site is out of compliance, the inspection report shall include a summary of the remedial actions required to bring the site back into compliance, as well as a schedule of implementation. i. Name, title, and signature of person conducting the site inspection; and the following statement: “I certify under penalty of law that this report is true, accurate, and complete, to the best of my knowledge and belief”. When the site inspection indicates that the site is not in compliance with any terms and conditions of the NPDES permit, the Permittee shall take immediate action(s) to: stop, contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance; correct the problem(s); implement appropriate Best Management Practices (BMPs), and/or conduct maintenance of existing BMPs; and achieve compliance with all applicable standards and permit conditions. In addition, if the noncompliance causes a threat to human health or the environment, the Permittee shall comply with the Noncompliance Notification requirements in Special Condition S5.F of the permit. Weston Heights North Technical Information Report Site Inspection Form General Information Project Name: Inspector Name: Title: CESCL # : Date: Time: Inspection Type: □ After a rain event □ Weekly □ Turbidity/transparency benchmark exceedance □ Other Weather Precipitation Since last inspection In last 24 hours Description of General Site Conditions: Inspection of BMPs Element 1: Mark Clearing Limits BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 2: Establish Construction Access BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Weston Heights North Technical Information Report Element 3: Control Flowrates BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 4: Install Sediment Controls BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 5: Stabilize Soils BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Weston Heights North Technical Information Report Element 6: Protect Slopes BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 7: Protect Drain Inlets BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 8: Stabilize Channels and Outlets BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Weston Heights North Technical Information Report Element 9: Control Pollutants BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Element 10: Control Dewatering BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP BMP: Location Inspected Functioning Problem/Corrective Action Y N Y N NIP Stormwater Discharges From the Site Observed? Problem/Corrective Action Y N Location Turbidity Discoloration Sheen Location Turbidity Discoloration Sheen Weston Heights North Technical Information Report Water Quality Monitoring Was any water quality monitoring conducted? □ Yes □ No If water quality monitoring was conducted, record results here: If water quality monitoring indicated turbidity 250 NTU or greater; or transparency 6 cm or less, was Ecology notified by phone within 24 hrs? □ Yes □ No If Ecology was notified, indicate the date, time, contact name and phone number below: Date: Time: Contact Name: Phone #: General Comments and Notes Include BMP repairs, maintenance, or installations made as a result of the inspection. Were Photos Taken? □ Yes □ No If photos taken, describe photos below: Weston Heights North Technical Information Report SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Weston Heights North Technical Information Report Bond Quantities, Facilities Summaries, and Declaration of Covenant Bond Quantities can be provided to the City upon request Storm drainage facilities are detailed on the engineering plans A declaration of covenant can be provide as part of the homeowner’s association documentation if required. Weston Heights North Technical Information Report SECTION 10 OPERATIONS AND MAINTENANCE MANUAL Weston Heights North Technical Information Report Operations and Maintenance Manual The following pages are selections from Appendix A of the 2009 King County Stormwater Design Manual, applicable to this project: Weston Heights North Technical Information Report 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. Weston Heights North Technical Information Report 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. Weston Heights North Technical Information Report NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed 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 and 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. Weston Heights North Technical Information Report 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/ inch wide at 4 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. Weston Heights North Technical Information Report NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR person. Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed 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/ inch. 8 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. footnote to guidelines for disposal 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 Weston Heights North Technical Information Report 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/ the depth from the bottom of basin to invert the 3 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 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/ inch wide at 4 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. Weston Heights North Technical Information Report NO. 5 – CATCH BASINS AND MANHOLES person. 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/ inch. 8 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. footnote to guidelines for disposal 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 Weston Heights North Technical Information Report 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. Weston Heights North Technical Information Report 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 1 ½ 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 1 ½ inches. Top rails bent more than 6 inches. Top rail free of bends greatyer 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 point 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. Weston Heights North Technical Information Report NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Chain Link Fencing Gate Damaged or missing members Missing gate. Gates in place. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Hinges intact and lubed. Gate is working freely. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical. Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. 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. Bar Gate Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access. Cross bar swings fully open and closed and prevents vehicle access. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility. Bollards Damaged or missing Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility. Does not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility. Boulders Dislodged Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility. Circumvented Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility. Weston Heights North Technical Information Report 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. Weston Heights North Technical Information Report NO. 12 – ACCESS ROADS Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet (i.e., trash and debris would fill up one standards size garbage can). Roadway drivable by maintenance vehicles. Debris which could damage vehicle tires or prohibit use of road. Roadway drivable by maintenance vehicles. 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. Blocked roadway Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high. Any obstruction restricting the access to a 10- to 12 foot width for a distance of more than 12 feet or any point restricting access to less than a 10 foot width. At least 12-foot of width on access road. Road Surface Erosion, settlement, potholes, soft spots, ruts Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles. Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility. Shoulders and Ditches Erosion Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Shoulder free of erosion and matching the surrounding road. Weeds and brush Weeds and brush exceed 18 inches in height or hinder maintenance access. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access. Modular Grid Pavement 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. Damaged or missing Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates. Weston Heights North Technical Information Report NO. 16 – WETPOND Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed Site Trash and debris Any trash and debris accumulated on the wetpond site. Wetpond site free of any trash or debris. 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. Side Slopes of Dam, Berm, internal 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 dams, berms or slopes, does not allow maintenance access, or interferes with maintenance activity. If trees are not a threat to dam, berm or embankment integrity, are not interfering with access or maintenance or leaves do not cause a plugging problem 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. Top or Side Slopes of Dam, Berm, internal berm or Embankment 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. Irregular surface on internal berm Top of berm not uniform and level. Top of berm graded to design elevation. Pond Areas Sediment accumulation (except first wetpool cell) Accumulated sediment that exceeds 10% of the designed pond depth. Sediment cleaned out to designed pond shape and depth. Sediment accumulation (first wetpool cell) Sediment accumulations in pond bottom that exceeds the depth of sediment storage (1 foot) plus 6 inches. Sediment storage contains no sediment. Liner damaged (If Applicable) Liner is visible or pond does not hold water as designed. Liner repaired or replaced. Water level (first wetpool cell) First cell empty, doesn't hold water. Water retained in first cell for most of the year. Algae mats (first wetpool cell) Algae mats develop over more than 10% of the water surface should be removed. Algae mats removed (usually in the late summer before Fall rains, especially in Sensitive Lake Protection Areas.) 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. Weston Heights North Technical Information Report NO. 16 – WETPOND Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance Is Performed 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 at the top of out flow path of spillway. Rip- rap on inside slopes need not be replaced. Spillway restored to design standards. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of 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. Weston Heights North Technical Information Report NO. 17 – WETVAULT access. 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 and 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