TECHNICAL INFORMATIO N REPORT
FOR
SHERLOCK DUVALL SELF -STORAGE
C&A PROJ ECT # 1 13 -00 4-16
PREPARED FOR:
Jackson Main Architecture 311 FIRST AVENUE SOUTH SEATTLE, WA 98104
PREPARED BY:
Cecil & Associates, LLC PO BOX 598 BOTHELL, WA 98041
JUNE 02, 2017 PERMIT SUBMITTAL
TECHNICAL INFORMATIO N REPORT
FOR
SHERLOCK DUVALL SELF -STORAGE
C&A PROJ ECT # 113 -004 -16
PREPARED FOR:
Jackson Main Architecture 311 FIRST AVENUE SOUTH SEATTLE, WA 98104
PREPARED BY:
Cecil & Associates, LLC PO BOX 598 BOTHELL, WA 98041
JUNE 02, 2017 PERMIT SUBMITTAL
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage i Duvall, WA TECHNICAL INFORMATIO N REPORT Sherlock Duvall Self-Storage Cecil & Associates Project No. 113-004-16 June 02, 2017
TABLE OF CONTENTS Section Page
1. PROJECT OVERVIEW ...... 1
FIGURE 1: T IR WORKSHEET ...... 3
FIGURE 2: SITE LOCAT ION ...... 8
FIGURE 3: DRAINAGE B ASINS, SUBBASINS, AN D SITE CHARACTERISTI CS ...... 9
FIGURE 4: SOILS ...... 11
2. CONDITIONS AND REQUIREMENTS SUMMARY ...... 12
2.01 CORE REQUIREMEN T #1 – DISCHARGE AT THE NATURAL LOCATION ...... 12
2.02 CORE REQUIREMEN T #2 – OFFSITE ANALY SIS ...... 12
2.03 CORE REQUIREMEN T #3 – FLOW CONTROL ...... 12
2.04 CORE REQUIREMEN T #4 – CONVEYANCE SY STEM ...... 12
2.05 CORE REQUIREMEN T #5 – CONSTRUCTION STORMWATER POLLUTION PREVENTION ...... 13
2.06 CORE REQUIREMEN T #6 – MAINTENANCE AND O PERATIONS ...... 13
2.07 CORE REQUIREMEN T #7 – FINANCIAL GUA RANTEES AND LIABILIT Y ...... 13
2.08 CORE REQUIREMEN T #8 – WATER QUALITY ...... 13
2.09 CORE REQUIREMEN T #9 – FLOW CONTROL BMPS ...... 13
2.10 SPECIAL REQUIRE MENTS ...... 13
3. OFFSITE ANALYSIS ...... 14
3.1: UPSTREAM ANALYS IS ...... 14
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage ii Duvall, WA 3.2: DOWNSTREAM ANAL YSIS ...... 14
3.3: ASSESSMENT SUMM ARY ...... 14
4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ...... 15
4.1: EXISTING SITE H YDROLOGY ...... 15
4.2: DEVELOPED SITE HYDROLOGY ...... 16
4.4: FLOW CONTROL SY STEM ...... 18
4.5: WATER QUALITY S YSTEM ...... 18
5. CONVEYANCY SYSTEM ANALYSIS AND DESIGN ...... 19 6. SPECIAL REPORTS AND STUDIES ...... 20 7. OTHER PERMITS ...... 21 8. CSWPP PLAN ANALYSIS AND DESIGN ...... 22
8.1: ESC PLAN ANALYS IS AND DESIGN ...... 22
8.2: SWPPS PLAN DESI GN ...... 22
9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ...... 25 10. OPERATIONS AND MAINTENANCE MANUAL ...... 26 11. APPENDICES ...... 27
APPENDIX A: Supporting Calculations ...... 28
APPENDIX B: Downstream System Map ...... 29
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage iii Duvall, WA 1. PROJECT OVERVIEW
The Sherlock Duvall Self-Storage project (project) is located at 14441 Main Street NE, in Duvall, Washington. The project will improve the site will a new 4-story self-storage building grossing approximately 105,000 square feet of leasable storage and office space. The project area consists of a single parcel (2426069058) approximately 42,385 square feet, or 0.973 acres, in size. The project is bordered by State Route (SR) 203 a.k.a. Carnation Duvall Rd. NE to the east; and, the Duvall Public Works Facility to the north. The western and southern property lines border vacant commercial/agricultural property currently proposed for a multi-family residential development, called the Duvall Village project. Thayer Creek bisects the Duvall Village project site providing a riparian buffer between the two projects. This project has classified the adjacent critical area buffers and will conform with the prescribed building setbacks.
The site improvements will include removal of the existing site structures, a shop and a modular home/office, and construct a new fully sprinkled self-storage building, surface parking area, associated utility service connections, and critical area buffer enhancements. Permitting for the project will be completed through the City of Duvall. The City will require (at a minimum) the following permits:
• Master Use Permit • Site Plan Review Application • Conditional Use Permit • SEPA Review • Grading and Utilities Permit; and, • Building Permit
Site Parameters The project will be required to coordinate site improvements with the City’s SR 203 Safety Improvements Project. The SR 203 Safety Improvements Project implements safety improvements including roadway widening and utility upgrades. Roadside pedestrian walkways (sidewalks) will be installed across the eastern frontage of the site, permitted by the SR 203 Safety Improvements Project.
Natural Drainage System The existing site is developed with a commercial retail land use. The site contains two buildings, a shop/garage and a mobile home/office. Access to the site is gained from a paved driveway to SR 203. The site is predominately impervious, consisting of buildings, asphalt driveway and gravel parking surfaces. Generally, the site slopes from east to west classified as mild slopes (0- 5%). The site does not contain a formal drainage network; runoff currently follows grade across the paved surfaces and discharges over the property line, assumed to be in a dispersed fashion. Runoff leaving the site discharges immediately to Thayer Creek. The creek flows in the northeast
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 1 Duvall, WA direction for approximately ¼ mile and discharges to the Snoqualmie River. The Snoqualmie River flows north and discharges to Possession Sound, offshore from the City of Everett. Runoff from upstream areas draining onto the site is limited and considered insignificant. The SR 203 road is uphill of the site. It has a paved shoulder that that would allow runoff to flow from the road onto the site. However, the SR 203 Safety Improvements project will improve the road with curb and gutter and a new stormwater drainage system for collection of runoff. Therefore, little or no runoff from the road will contribute to the project runoff in the developed condition.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 2 Duvall, WA KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND PROJECT ENGINEER DESCRIPTION
Project Owner ______Project Name ______Phone ______DPER Permit # ______Address ______Location Township ______Range ______Project Engineer ______Section ______Company ______Site Address ______Phone ______
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Landuse (e.g.,Subdivision / Short Subd. / UPD) DFW HPA Shoreline Management Building (e.g.,M/F / Commercial / SFR) COE 404 Structural Clearing and Grading DOE Dam Safety Rockery/Vault/_____ Right-of-Way Use FEMA Floodplain ESA Section 7 Other ______ COE Wetlands Other ______
Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Full Full Type of Drainage Review Targeted Plan Type (check Modified (check one): Simplified one): Large Project Simplified Date (include revision Directed Date (include revision ______dates): ______dates): ______Date of Final: Date of Final: ______
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Experimental / Blanket Description: (include conditions in TIR Section 2) ______Approved Adjustment No. ______Date of Approval: ______
2016 Surface Water Design Manual 4/24/2016 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No Describe: ______Start Date: ______Completion Date: ______Re: KCSWDM Adjustment No. ______
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan : ______Special District Overlays: ______Drainage Basin: ______Stormwater Requirements: ______
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ______ Steep Slope ______ Lake ______ Erosion Hazard ______ Wetlands ______ Landslide Hazard ______ Closed Depression ______ Coal Mine Hazard ______ Floodplain ______ Seismic Hazard ______ Other ______ Habitat Protection ______ ______
Part 10 SOILS
Soil Type Slopes Erosion Potential ______
High Groundwater Table (within 5 feet) Sole Source Aquifer Other ______ Seeps/Springs Additional Sheets Attached
2016 Surface Water Design Manual 4/24/2016 2 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE LIMITATION / SITE CONSTRAINT Core 2 – Offsite Analysis ______ Sensitive/Critical Areas ______ SEPA ______ LID Infeasibility ______ Other ______ ______ Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description)
Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:______
Flow Control (include facility Level: 1 / 2 / 3 or Exemption Number ______summary sheet) Flow Control BMPs ______
Conveyance System Spill containment located at: ______
Erosion and Sediment Control / CSWPP/CESCL/ESC Site Supervisor: ______Construction Stormwater Contact Phone: ______Pollution Prevention After Hours Phone: ______
Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Provided: Yes / No Liability
Water Quality (include facility Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog summary sheet) or Exemption No. ______Landscape Management Plan: Yes / No
Special Requirements (as applicable): Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Requirements Name: ______
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): ______Datum:
Flood Protection Facilities Describe:
2016 Surface Water Design Manual 4/24/2016 3 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Source Control Describe land use: (commercial / industrial land use) Describe any structural controls:
Oil Control High-use Site: Yes / No Treatment BMP: ______Maintenance Agreement: Yes / No with whom? ______Other Drainage Structures Describe:
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION Clearing Limits Stabilize exposed surfaces Cover Measures Remove and restore Temporary ESC Facilities Perimeter Protection Clean and remove all silt and debris, ensure operation of Permanent Facilities, restore Traffic Area Stabilization operation of Flow Control BMP Facilities as Sediment Retention necessary Surface Water Collection Flag limits of SAO and open space preservation Dewatering Control areas Dust Control Other ______ Flow Control Protection of Flow Control BMP Facilities (existing and proposed) Maintain BMPs / Manage Project
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention ______ Vegetated Flowpath ______
Infiltration ______ Wetpool ______
Regional Facility ______ Filtration ______
Shared Facility ______ Oil Control ______
Flow Control BMPs ______ Spill Control ______
Other ______ Flow Control BMPs ______ Other ______
2016 Surface Water Design Manual 4/24/2016 4 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement Cast in Place Vault Covenant Retaining Wall Native Growth Protection Covenant Rockery > 4’ High Tract Structural on Steep Slope Other ______ Other ______
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate.
Signed/Date
2016 Surface Water Design Manual 4/24/2016 5
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2. CONDITIONS AND REQUIREMENTS SUMMARY
The project is a commercial site development that triggers Full Drainage Review for proposing over 2,000 square feet of new or replaced impervious surfaces and contains over 7,000 square feet of land disturbing activity. Full Drainage Review comply with all nine core requirements and all five special requirements. The core requirements and special requirements applicability to this project are reviewed below.
2. 01 CORE REQUIREMENT #1 – DISCHARGE AT THE NAT URAL LOCATION Section 1.2.1 states that projects that either discharge over 0.5 cfs for the 100-year storm must provide a tight line system for offsite discharge to prevent erosion. This project exceeds 0.5 cfs during the 100-year peak storm event. The project proposes a connection to the public storm line located immediately north of the project.
2. 02 CORE REQUIREMENT #2 – OFFSITE ANALYSIS A level 1 downstream analysis has been completed for the area downstream of the site to the receiving water body, the Snoqualmie River. A level 1 downstream analysis consists of studying maps and resource materials, field observation, and a description of drainage system and potential problems. The downstream analysis is contained is Section 3 – Offsite Analysis.
2. 03 CORE REQUIREMENT #3 – FLOW CONTROL The Snoqualmie River is a flow control exempt water body for the portion downstream of the Middle Fork. The project is within a ¼ of an exempt receiving body per KCSWDM 1.2.3.1. Therefore, this project is exempt from flow control.
2. 04 CORE REQUIREMENT # 4 – CONVEYAN CE SYSTEM The on-site conveyance system will consist of roof downspouts, footing drains, Type 1 and Type 2 catch basins, and conveyance pipes ranging in size from with a minimum diameter of 12- inches. For basic conveyance system design the latest edition of the King County Surface Water Design Manual (SWDM), Chapter 4: Conveyance System Analysis and Design will be followed.
Pipe Systems: 1. New pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for onsite tributary areas and existing conditions for any offsite tributary areas.
2. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a severe flooding problem or sever erosion problem as described in Core Requirement #2, Section 1.2.2. Any overflow occurring onsite for runoff events up to and including the 100- year event must discharge at the natural location for the project site.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 12 Duvall, WA 2. 05 CORE REQUIREMENT #5 – CONSTRUCTION STORMWA TER POLLUTION PREVEN TION A Temporary Erosion Sedimentation Control Plan (TESC) has been provided with the permit application. Enforcement of the construction SWPPP will be by the City since the site is less than an acre, under thresholds for a registering under Ecology’s construction stormwater program.
2. 06 CORE REQ UIREMENT #6 – MAI NTENANCE AND OPERATI ONS This report contains an Operations and Maintenance (O&M) manual that serves as a guideline for maintaining the stormwater facilities. The O&M Manual is attached in Section 10.
2. 07 CORE REQUIREMENT #7 – FINANCIAL GUARANTEES AND LIA BILITY The purpose of the financial guarantees and liability section is for projects to comply with King County Ordinance 12020 and the liability requirements of King County Code 9.04.100. Financial guarantees can be either a drainage facilities restoration and site stabilization guarantee or a drainage defect and maintenance guarantee. The project will comply with financial and liability guarantees as required by the City.
2. 08 CORE REQUIREMENT #8 – WATER QUALITY The project will install approximately 6,700 square feet of asphalt parking area, exceeding the 5,000 square feet threshold for providing water quality. Water quality treatment will be provided to the Enhanced Basic treatment level. The Enhanced Basic treatment targets 30% dissolved copper removal and greater than 60% dissolved zinc removal, in addition to 80% TSS removal. This is functionally equivalent to Ecology’s Enhanced Water Quality Treatment Level. The project will provide a bioretention BMP to achieve the Basic Enhanced treatment level, approved by the Washington State Department of Ecology.
2. 09 CORE REQUIREMENT #9 – FLOW CONTROL BMPS Flow control BMPs are required to provide flow mitigation in addition to standard flow control requirements to the maximum extent feasible. Individual lot BMP requirements per section 1.2.9.2 will be provided. This project will comply with Large Lot BMP requirements. See Section 4 for LID BMP feasibility analysis.
2. 10 SPECIAL REQUIREMENTS The project does not trigger Special Requirements pertaining to area-specific requirements, flood hazard area delineation, flood protection facilities, source control, or oil control. However, the project will occur adjacent to a waterway of the state, the Thayer Creek, and buffer enhancement will be incorporated into the project. The project will obtain all necessary State and local permits required for such improvements. A Critical Areas Study by Altmann Oliver Associates, LLC has been included with the submittal.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 13 Duvall, WA 3. OFFSITE ANALYSIS Projects are required to completed an offsite analysis for engineering review. The primary component of the offsite analysis is a study of the downstream flow path. The purpose of the study is to determine if the downstream conveyance system is constrained or has restrictions that could require additional flow mitigation for the project. Though, the upstream areas have not been omitted from the offsite analysis they are considered insignificant as described below.
3.1 : UPSTR EAM ANALYSIS Runoff from upstream areas draining onto the site is limited and considered insignificant. The SR 203 road is uphill of the site. It has a paved shoulder that that would allow runoff to flow from the road onto the site. However, the SR 203 Safety Improvements project will improve the road with curb and gutter and a new stormwater drainage system for collection of runoff. Therefore, little or no runoff from the road will contribute to the project runoff in the developed condition.
3. 2: DOWNS TREAM ANALYSIS The downstream flow path was researched using the City’s published storm drain map. The Cecil & Associates field verified the downstream flow path with a site visit completed on October 17, 2016. The project site is contained within one basin dubbed the Thayer Creek Basin. All stormwater runoff will discharge to a public storm line located parallel to the northern property line on the Duvall Public Works Facility site. The public storm main is an 18” diameter pipe with an outfall to Thayer Creek. The creek flows in the northeast direction for approximately ¼ mile and discharges to the Snoqualmie River. The Snoqualmie River flows north and discharges to Possession Sound, offshore from the City of Everett.
3. 3: ASSESSMENT S UMMARY
A site visit was conducted on April 5, 2017, to observe the storm line located downstream of the site, bisecting the City’s Public Works Facility (north). Representatives from the City Public Works facility presented erosion occurring at the outfall. Based on the erosion, the pipe has been flagged as a capacity restrained system. As a result, the project will provide an energy dissipation design to reduce erosion potential and stabilize the outfall. The energy dissipation and stabilization design will be coordinated with the City and permitted with the project.
No other capacity, flooding, or erosion problems were evident along the downstream system, and we do not anticipate any significant impacts to the downstream system resulting from impacts by the project once the downstream outfall is stabilized.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 14 Duvall, WA 4. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID) AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
4.1: EXISTING SITE HYDROL OGY The existing site is developed with a commercial retail land use. The site contains two buildings, a shop/garage and a mobile home/office. Access to the site is gained from a paved driveway to SR 203. The site is predominately impervious, consisting of buildings, asphalt driveway and gravel parking surfaces. Generally, the site slopes from east to west classified as mild slopes (0- 5%). The site does not contain a formal drainage network; runoff currently follows grade across the paved surfaces and discharges over the property line, assumed to be in a dispersed fashion. Runoff leaving the site discharges immediately to Thayer Creek.
The existing surface coverage summary is shown in the table below: Existing Site Conditions Shop 2,905 sf 0.067 acres Mobile Home 1,684 sf 0.039 acres Asphalt 6,717 sf 0.154 acres Gravel 20,270 sf 0.465 acres Concrete 1,842 sf 0.042 acres Pervious 8,967 sf 0.206 acres
A geotechnical engineering report was prepared by Geotech Consultants, Inc., attached in Section 6. The report describes the soils as containing fill. Fill varies in consistency and depth across the site. Fill soils have been described as typically loose, but consisted of soils varying from a sandy silt to a silty pit-run. The fill contained occasional cobbles and boulders, organic debris, and concrete chunks up to 2-feet across. Underlying the fill was medium dense, native silt or gravelly, silty sand (glacial till). The depth of fill soils varied from 6 to 16 feet below existing ground surface. For runoff modeling purposes class C soils have been assumed.
Existing site peak runoff rates have been estimated using WWHM4, shown in the table below:
Return Period Flow(cfs) 2 year 0.305584 5 year 0.390731 10 year 0.449129 25 year 0.525441 50 year 0.584228 100 year 0.644748
Calculations are attached in Appendix A.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 15 Duvall, WA 4.2: DEVELOPED SITE HYDRO LOGY The site improvements will include removal of the existing site structures, a shop and a modular home/office, and construct a new fully sprinkled self-storage building, surface parking area, associated utility service connections, and critical area buffer enhancements.
From the core requirements above, the project will be required to implement water quality BMPs for all pollution generating surfaces and LID stormwater BMPs to the maximum extent feasible. The water quality sizing and design is described in more detail in section 4.5, below. A Large Lot LID BMP feasibility has been added within this section, below.
The developed surface coverage summary is shown in the table below: Developed Site Conditions Total Site 42,385 sf 0.973 acres Building Area 24,740 sf 0.568 acres Road 5,526 sf 0.127 acres Walkway (Hardscape) 246 sf 0.006 acres Pervious 11,532 sf 0.273 acres
Developed site peak runoff rates have been estimated using 2012 WWHM, shown in the table below:
Return Period Flow(cfs) 2 year 0.2843 5 year 0.3657 10 year 0.4218 25 year 0.4954 50 year 0.5522 100 year 0.6109
Calculations are attached in Appendix A.
LID BMP Feasibility Analysis BMPs must be implemented, at a minimum for impervious surfaces area amounts, for sites that have impervious area greater than 65% of the buildable lot area, to 20% of the target impervious surfaces or to an impervious area equal to at least 10% of the site/lot, whichever is less.
Total Site Area 42,385 sf 0.973 acres Buffer Area 4,073 sf 0.094 acres Buildable Area 38,988 sf 0.880 acres Total Impervious Area 30,512 sf 0.700 acres Percent Impervious of Buildable Area 80%
20% of Target Impervious Surface 6,102 sf 0.140 acres 10% of Site Area 4,239 sf 0.097 acres
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 16 Duvall, WA
Therefore, LID BMPs are required for 4,239 sf of targeted impervious area. Section 1.2.9.2.2 states that LID BMPs must be evaluated in the following order:
1) Apply Full Dispersion to all targeted impervious surfaces. 2) Apply Full Infiltration of roof runoff. 3) Apply Full Infiltration, Partial Infiltration, Bioretention, or Permeable Pavement. 4) Apply Basic Dispersion. 5) Pay a fee in lieu of using feasible BMPs from requirements 1-4 above or apply Reduced Impervious Surface Credit or native Growth Retention Credit.
• All new pervious surfaces must be protected by retaining the duff layer or native topsoil to the maximum extent practicable. Soil amendment to new pervious surfaces shall be applied. • Any proposed connection to roof downspouts must be via a perforated pipe connection.
Infeasibility criteria for each BMP in order are listed below:
Full Dispersion: Full Dispersion is considered infeasible and not required for projects that cannot meet the minimum design requirements per section C.2.1.1. This project cannot provide a minimum 100-foot flow path per C.2.1.1.
Full Infiltration: Full Infiltration is considered infeasible and not required for projects that cannot meet the minimum design requirements per section C.2.2.2. Coarse sands, cobbles, or medium sands are required for full infiltration. This site contains silty fill over silty glacial till with perched groundwater. Therefore, full infiltration is not feasible.
Limited Infiltration: Limited Infiltration is considered infeasible and not required for projects that cannot meet the minimum design requirements per section C.2.3.2. Fine sands, loamy sands, sandy loams, or loams allow for limited infiltration. This site contains silty fill over silty glacial till with perched groundwater. Therefore, limited infiltration is not feasible.
Bioretention: Bioretention is considered infeasible and not required for projects that contain any criteria on the bioretention infeasibility criteria list in section C.2.6. A minimum soil saturated hydraulic conductivity of 0.3 inches per hour is required. Also, a vertical separate of 3’ from the seasonal groundwater table is required. Therefore, bioretention is not feasible.
Permeable Pavement: Permeable Pavement is considered infeasible and not required for projects that contain any criteria on the bioretention infeasibility criteria list in section C.2.7. A minimum soil saturated hydraulic conductivity of 0.3 inches per hour is required. Also, a vertical separate of 1 foot from the seasonal groundwater table is required. Therefore, permeable pavement is not feasible.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 17 Duvall, WA
Basic Dispersion: Basic Dispersion is considered infeasible and not required for projects that cannot meet the minimum design requirements per section C.2.4.1. Basic dispersion is not feasible is a vegetated flow path over slopes less than 15% can be achieved without site specific geotechnical review and approval. Therefore, basic dispersion is not feasible.
Perforated stub connections for roof downspouts are considered not feasible on this project because infiltration would occur directly adjacent to the building’s basement. The property line makes moving the downspout roof leaders away from the building impossible.
4.3: PERFORMANCE STANDARD S This section states the performance requirements for flow control systems, conveyance systems, and water quality systems.
Flow Control: N/A
Conveyance Systems: New pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for onsite tributary areas and existing conditions for any offsite tributary areas.
Water Quality Systems: The water quality filtration standard is Basic Enhanced.
4.4: FLOW CONTROL SYSTEM The project discharges to an exempt water body, the Snoqualmie River. Therefore, detention is not required.
4.5: WATER QU ALITY SYSTEM The project will install approximately 5,526 square feet of asphalt parking area, exceeding the 5,000 square feet threshold for providing water quality. Water quality treatment will be provided to the Enhanced Basic treatment level. The Enhanced Basic treatment targets 30% dissolved copper removal and greater than 60% dissolved zinc removal, in addition to 80% TSS removal. This is functionally equivalent to Ecology’s Enhanced Water Quality Treatment Level. The project will provide a bioretention BMP to achieve the Basic Enhanced treatment level, approved by the Washington State Department of Ecology.
The bioretention BMP has been sized using the approved continuous runoff model, WWHM4, so that at least 91% of the runoff volume will filter through the amended bioretention soil. Calculations are attached in Appendix A.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 18 Duvall, WA
5. CONVEYANCY SYSTEM ANALYSIS AND DESIGN
Conveyance calculations are attached in Appendix A.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 19 Duvall, WA 6. SPECIAL REPORTS AND STUDIES
The following studies and/or reports were referenced in the compilation of this Technical Information Report (TIR). • Geotechnical Engineering Report – The Riley Group, Inc. • Geotechnical Engineering Report – Geotech Consultants, Inc. • Critical Areas Report - Altmann Oliver Associates, LLC • Floodplains Map – City of Duvall • 303d Listing – Washington State Department of Ecology
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 20 Duvall, WA
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY: THE RILEY GROUP, INC. 17522 BOTHELL WAY NORTHEAST BOTHELL, WASHINGTON 98011
PREPARED FOR: SHERLOCK INVESTMENTS – DUVALL, LLC 700 HIGHWAY 308 POULSBO, WASHINGTON 98370
RGI PROJECT NO. 2016-185
DUVALL SHERLOCK STORAGE 14441 STATE ROUTE 203 DUVALL, WASHINGTON 98019
DECEMBER 9, 2016
Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
Geotechnical Engineering Report i December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
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 ...... 5 5.2.2 Stripping ...... 6 5.2.3 Excavations...... 6 5.2.4 Site Preparation ...... 6 5.2.5 Structural Fill ...... 7 5.3 FOUNDATIONS ...... 9 5.3.1 Driven Piles...... 9 5.4 RETAINING WALL ...... 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 ...... 12 6.0 ADDITIONAL SERVICES ...... 13 7.0 LIMITATIONS...... 13
LIST OF FIGURES AND APPENDICES
Figure 1 ...... Site Vicinity Map Figure 2 ...... Geotechnical Exploration Plan Figure 3 ...... Retaining Wall Drainage Detail Figure 4 ...... Typical Footing Drain Detail
Appendix A ...... Field Exploration and Laboratory Testing
Geotechnical Engineering Report ii December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
Executive Summary This Executive Summary should be used in conjunction with the entire GER for design and/or construction purposes. It should be recognized that specific details were not included or fully developed in this section, and this 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 4 test pits to depths up to 13 feet below ground surface (bgs). 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 site is underlain by 2 feet to over 12 feet of loose to medium dense fill consisting of silty sand with gravel over native soil. The native soil is stiff to very stiff silt and silty clay to dense silty sand with gravel. Groundwater: Groundwater seepage was encountered at 9 feet bgs in TP-3 during our field exploration. Foundations: The building should be supported on a grade beam foundation on driven piles extending to the suitable sand soils encountered 12 feet below the ground surface. As an alternative, if the building can be designed to tolerate some settlement, the grid foundation can be supported on 24 inches of reinforced structural fill. Slab-on-grade: Slab-on-grade floors for the proposed building can be supported on at least 24 inches of reinforced structural fill if some settlement of the floor is acceptable. If settlement of the floors is not desired, the floors should be supported on the grade beam system. Pavements: The following pavement sections are recommended: For heavy duty traffic areas: 3 inches of hot mix asphalt (HMA) over 6 inches of crushed rock base (CRB) over 18 inches of structural fill For standard duty traffic areas or general parking areas: 2 inches of HMA over 6 inches of CRB over 12 inches of structural fill For heavy duty concrete pavement areas: 6 inches of concrete over 4 inches of CRB over 18 inches of structural fill For standard duty concrete pavement areas: 5 inches of concrete over 4 inches of CRB over 12 inches of structural fill
Geotechnical Engineering Report 1 December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
1.0 Introduction This Geotechnical Engineering Report (GER) presents the results of the geotechnical engineering services provided for the proposed Sherlock Storage project in Duvall, Washington. The purpose of this GER is to assess subsurface conditions and provide geotechnical recommendations for the construction of a new storage building and related facilities. 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 site is located at 14441 State Route 203 in Duvall, Washington. The approximate location of the site is shown on Figure 1. The site is currently occupied by a single-family residence built in 1960 with several outbuildings. RGI understands that a 4-story storage building will be constructed at the site. Development will include an associated covered customer service area, parking, and associated utilities. Our understanding of the project is based on a site plan prepared by David Charles Beal Architect dated October 2, 2016. Based on our experience of similar development, RGI anticipates that the proposed building will be supported on perimeter walls with bearing loads of 4 to 8 kips per linear foot, and a series of columns with a maximum load up to 250 kips. Slab-on-grade floor loading of 300 pounds per square foot (psf) are expected. RGI also expects that some site grading will be needed to reach the final grade.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION On November 21, 2016, RGI observed the excavation of 4 test pits. The approximate exploration locations are shown on Figure 2. At the time the exploration was performed, a major portion of the site was occupied by existing buildings, debris, and construction equipment. There was limited space for test exploration and the number of test pits were less than what we originally planned.
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Field logs of each exploration were prepared by the geologist who continuously observed the excavation. These logs included visual classifications of the materials encountered during excavation as well as our interpretation of the subsurface conditions between samples. The test pit logs included in Appendix A represent an interpretation of the field logs and include modifications based on laboratory observation and analysis of the samples.
3.2 LABORATORY TESTING During the field explorations, a representative portion of each recovered sample was sealed in containers and transported to our laboratory for further visual and laboratory examination and testing. Samples retrieved from the test pits were tested for moisture content and grain size 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 site is a trapezoidal-shaped parcel of land approximately 41,535 square feet in size. The site is bound to the north by the Duvall Sewage Treatment Plant, to the west and south by undeveloped properties, and to the east by State Route 203. The site is occupied by a single-family residence built in 1960 in the southwest portion of the site and several outbuildings. The site gently slopes to the west in the major portion of the site and there is an approximately 15-foot-high west facing fill slope along the western edge of the property.
4.2 GEOLOGY Review of the Geologic Map of King County, Washington by Derek B. Booth, etc (2002) indicates that the major portion of the site soil is mapped as glacial till (Map Unit Qvt) and the western edge of the property close to Snoqualmie Valley is mapped as alluvium deposit (Map Unit Qal). Till which is an unsorted, unstratified, highly compacted mixture of clay, silt, sand, gravel, and boulders deposited directly by glacial ice. Alluvium deposit is moderately sorted deposits of cobble gravel, pebbly sand, and sandy silt along major rivers and stream channel deposited at higher elevations and typically have greater relief than younger alluvium. The soils encountered was different from the descriptions on the geology map. The site is underlain by over 12 feet of the fill over stiff to very stiff silt to silty clay.
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4.3 SOILS The site is underlain by 2 feet to over 12 feet of loose to medium dense fill consisting of silty sand with gravel over native soil. The native soil is stiff to very stiff silt and silty clay to dense silty sand with gravel. The fill thickness increases significantly along the western edge of the property. Test pit TP-4 was excavated at the edge of the property to explore the depth of the fill. The test pit was terminated before reaching the native soil due to heavy caving. Based on the topography and the soil exposed on the slope surface, the fill thickness is estimated to be approximately 20 feet. More detailed descriptions of the subsurface conditions encountered are presented in the test pits are included in Appendix A. Sieve analysis was performed on 3 selected soil samples. The grain-size distribution curves are included in Appendix A.
4.4 GROUNDWATER Groundwater seepage was encountered at 9 feet bgs in TP-3 during our field 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.
4.5 SEISMIC CONSIDERATIONS Based on the 2012 International Building Code (IBC), RGI recommends the follow seismic parameters in Table 1 be used for design. Table 1 IBC Seismic Parameters 2012 IBC Parameter Value
Site Soil Class1 D2 Site Latitude 47.7317466 N Site Longitude 121.9874529 W Maximum considered earthquake spectral response Ss =1.227, S1 =0.468 acceleration parameters (g) Spectral response acceleration parameters adjusted for site Sms =1.238, Sm1 =0.717 class (g)
Design spectral response acceleration parameters (g) Sds =0.826, Sd1 =0.478 1 Note: In general accordance with the USGS 2012 International Building Code. IBC Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile.
Geotechnical Engineering Report 4 December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
2 Note: The 2012 International Building Code requires 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. Test pits extended to a maximum depth of 13 feet, and this seismic site class definition considers that similar soil continues below the maximum depth of the subsurface 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 soil conditions encountered during field exploration and assessed the potential for liquefaction of the site’s soil during an earthquake. The native soil is stiff to very stiff silt to clay over dense silty sand; in our professional opinion the potential of soil liquefaction during an earthquake event is minimal.
4.6 GEOLOGIC HAZARD AREAS Regulated geologically hazardous areas include erosion, landslide, earthquake, or other geological hazards. Based on the conditions observed on the site, the site does not contain geologically hazardous areas.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS Based on the explorations, the major geotechnical concern of the proposed development is the fill underlying the site. If the building foundation is supported on shallow footings bearing on existing fill, it will experience differential settlement that potentially damage the building structural system. RGI recommends that the building be supported on a deep foundation system bearing on competent native soil. Slab-on-grade floors for the proposed building can be similarly supported on deep foundation system. Pavements can be supported on 12 to 18 inches of structural fill with a woven geotextile fabric over existing native soil. 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 RGI expects that site grading will consist of shallow cuts and fills to achieve building and pavement grades and excavation for utilities including storm, water, sanitary sewer, and other utilities.
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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, 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.
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5.2.2 STRIPPING Stripping should include removal of the existing foundations, pavements and vegetation. The test pits encountered 2 to 12 inches of grass and topsoil. Based on the conditions encountered in the vegetated areas, a stripping depth of 6 inches should be used with deeper areas in the heavily vegetated areas of the site.
5.2.3 EXCAVATIONS All temporary cut slopes associated with the site and utility excavations should be adequately inclined to prevent sloughing and collapse. 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). 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 5 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 RGI anticipates that some areas of loose or soft soil will be exposed upon completion of stripping and grubbing. Proofrolling and subgrade verification should be considered an essential step in site preparation. After stripping, grubbing, and prior to placement of structural fill, RGI recommends proofrolling building and pavement subgrades and areas to receive structural fill. These areas should be proofrolled under the observation of RGI and compacted to a firm and unyielding condition in order to achieve a minimum compaction level of 95 percent of the modified proctor maximum dry density as determined by the American Society of Testing and Materials D1557-09 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557).
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Proofrolling and adequate subgrade compaction can only be achieved when the soils are within approximately ± 2 percent moisture content of the optimum moisture content. Soils that appear firm after stripping and grubbing may be proofrolled with a heavy compactor, loaded double-axle dump truck, or other heavy equipment under the observation of an RGI representative. This observer will assess the subgrade conditions prior to filling. The need for or advisability of proofrolling due to soil moisture conditions should be determined at the time of construction. 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.
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 2 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
Geotechnical Engineering Report 8 December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185 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 onsite is consider unsuitable for being reused as structural fill. It may be necessary to import structural fill meeting the gradation requirements listed in Table 2 for wet weather conditions. 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.
For dry season earthwork, the percent passing the No. 200 may be increased to 10 percent maximum or materials meeting the 2012 Washington State Department of Transportation (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction, Section 9-03.14(1) may be used. 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 3. The soil’s maximum density and optimum moisture should be determined by ASTM D1557. Table 3 Structural Fill Compaction ASTM D1557
Minimum Moisture Content Location Material Type Compaction Range Percentage
On-site granular or approved Foundations imported fill soils: 95 +2 -2 On-site granular or approved Retaining Wall Backfill imported fill soils: 92 +2 -2 On-site granular or approved Slab-on-grade imported fill soils: 95 +2 -2 General Fill (non- On-site soils or approved 90 +3 -2 structural areas) imported fill soils: Pavement – Subgrade On-site granular or approved 95 +2 -2 and Base Course imported fill soils:
Geotechnical Engineering Report 9 December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
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 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 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 As discussed, the major geotechnical concern with this project is the existing fill underlying the site. If the foundations are directly supported on existing fill, the building will experience unacceptable differential settlement. RGI recommends supporting the building using piles to transfer building loads to the competent native soil.
5.3.1 DRIVEN PILES To avoid the potential damages from settlement, typically the building should be supported on driven piles bearing on dense native soil below the fill. RGI recommends that two test piles be installed before construction. The test piles will provide the necessary information for pile capacity and pile depth. RGI expects 4- to 6- inch-diameter steel pipe piles may be used for supporting the proposed building foundation. The piles should be driven to refusal in the competent native soil below the fill. Based on our experience with similar projects, the pile capacities listed in Table 4 can be used for project planning and preliminary structural design. Based on the soil information, RGI expects that the pile termination depth will be from 15 feet to 25 feet. The actual pile depth will be determined in the field based on actual driving condition.
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Table 4 Driven Pier Capacities (kips)
Pile Diameter Pile Type Compression Uplift Lateral* (inches)
Steel Pipe 6 30 14 3
Steel Pipe 4 20 14 2 *Lateral load assumes 1” top deflection and uplift can only be achieved by welding the pile couplers. With pile 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 WALL If retaining walls are needed, 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. The retaining wall foundation must be supported on firm native soil or structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall drainage detail is shown on 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 2,500 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 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 the Section 5.3.
5.5 SLAB-ON-GRADE CONSTRUCTION The slab-on-grade supported on existing fill will be subject to differential settlement that can potential damage the slab. If this is not acceptable, the slab should be supported on the grade beam system and piles.
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Immediately below the floor slab, RGI recommends placing a 4-inch-thick capillary break layer of clean, free-draining pea gravel, washed rock, or crushed rock that has less than 5 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 the 4-inch-thick layer of clean gravel or rock
5.6 DRAINAGE 5.6.1 SURFACE Final exterior grades should promote free and positive drainage away from the building area. 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 Perimeter foundation drains, details shown on Figure 4, are generally installed around the building. 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. If the building is supported on pile foundation, the footing drains can be eliminated.
5.6.3 INFILTRATION The site contains loose fill over native soil which is impermeable. Groundwater seepage was encountered at shallow depth. No suitable soil layer was encountered to support infiltration. Infiltration system is not recommended for the site.
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 Duvall 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 ASTM D1557. As noted, soils excavated on site will not be suitable for use as backfill material. Imported structural fill meeting the gradation provided in Table 2 should be used for trench backfill.
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Since the site will subject to differential settlements, all utilities pipes should use flexible joints for connections to structures.
5.8 PAVEMENTS Pavement subgrades should be stripped and proofrolled as described in Section 5.2 of this GER. The pavement sections should be supported on 12 and 18 inches of structural fill for standard and heavy duty pavements, respectively. If the exposed soils can be moisture conditioned and compacted to the requirements of structural fill to the depths specified, overexcavation should not be necessary. In areas where the existing fill soils are not suitable for moisture conditioning and compaction or where soft deeper areas are identified during proofrolling, the soils should be overexcavated and replaced with suitable structural fill underlain by a woven geotextile fabric. Regardless of the relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. This condition should be verified by proofrolling with heavy construction equipment. With the pavement subgrade prepared as described above, RGI recommends the following pavement sections for paved with flexible asphalt concrete surfacing. For heavy duty traffic areas: 3 inches of hot mix asphalt (HMA) over 6 inches of crushed rock base (CRB) over 18 inches of structural fill For standard duty traffic areas or general parking areas: 2 inches of HMA over 4 inches of CRB over 12 inches of structural fill The asphalt paving materials used should conform to the Washington State Department of Transportation (WSDOT) specifications for Hot Mix Asphalt Class 1/2 inch and CRB surfacing. The following concrete pavement sections can be used for heavy duty traffic and parking areas pavement section: For heavy duty concrete pavement areas: 6 inches of concrete over 4 inches of CRB over 18 inches of structural fill For standard duty concrete pavement areas: 5 inches of concrete over 4 inches of CRB over 12 inches of structural fill 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 two 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.
Geotechnical Engineering Report 13 December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185 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 proposal.
7.0 Limitations This GER is the property of RGI, Sherlock Investments - Duvall, 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 report was issued. This GER is intended for specific application to the Proposed Sherlock Investments - Duvall, LLC project at 14441 State Route 203 in Duvall, Washington, and for the exclusive use of Sherlock Investments - Duvall, 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 site or identification or prevention of pollutants, hazardous materials, or conditions. Our Phase I Environmental Site Assessment is provided under a separate cover. 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.
SITE
USGS, 2014, Carnation, Washington Approximate Scale: 1"=1000' 7.5-Minute Quadrangle 0 500 1000 2000 N Corporate Office Duvall Sherlock Storage Figure 1 17522 Bothell Way Northeast RGI Project Number Site Vicinity Map Date Drawn: Bothell, Washington 98011 2016-185 12/2016 Phone: 425.415.0551 Address: 14441 SR 203, 14441 Main Street Northeast, 14441 Carnation Duvall Road Northeast, Fax: 425.415.0311 Duvall, Washington 98019 TP-3 TP-2
TP-4
TP-1
Approximate Scale: 1"=40' = Test pit excavated by RGI, 11/21/16 0 20 40 80 N = Site boundary Corporate Office Duvall Sherlock Storage Figure 2 17522 Bothell Way Northeast RGI Project Number Date Drawn: Bothell, Washington 98011 2016-185 Geotechnical Exploration Plan 12/2016 Phone: 425.415.0551 Address: 14441 SR 203, 14441 Main Street Northeast, 14441 Carnation Duvall Road Northeast, Fax: 425.415.0311 Duvall, Washington 98019 12" Minimum Wide Free-Draining Gravel
Slope to Drain
12" min.
Filter Fabric Material Excavated Slope (See Report for Appropriate Incliniations) Compacted Structural Backfill (Native or Import)
12" Over the Pipe
4" Diameter PVC 3" Below the Pipe Perforated Pipe
Not to Scale
Corporate Office Duvall Sherlock Storage Figure 3 17522 Bothell Way Northeast RGI Project Number Retaining Wall Drainage Detail Date Drawn: Bothell, Washington 98011 2016-185 12/2016 Phone: 425.415.0551 Address: 14441 SR 203, 14441 Main Street Northeast, 14441 Carnation Duvall Road Northeast, Fax: 425.415.0311 Duvall, Washington 98019 Building Slab
Compacted Structural Backfill
Filter Fabric
4" Perforated Pipe
3/4" Washed Rock or Pea Gravel
Not to Scale
Corporate Office Duvall Sherlock Storage Figure 4 17522 Bothell Way Northeast RGI Project Number Typical Footing Drain Detail Date Drawn: Bothell, Washington 98011 2016-185 12/2016 Phone: 425.415.0551 Address: 14441 SR 203, 14441 Main Street Northeast, 14441 Carnation Duvall Road Northeast, Fax: 425.415.0311 Duvall, Washington 98019 Geotechnical Engineering Report December 9, 2016 Duvall Sherlock Storage, Duvall, Washington RGI Project No. 2016-185
APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING On November 21, 2016, RGI explored the subsurface soil conditions at the site by observing the excavation of 4 test pits to a maximum depth of 13 feet below existing grade. The test pit locations are shown on Figure 2. The test pit 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, and the limited laboratory testing described below. Moisture Content Determinations Moisture content determinations were performed in accordance with the American Society of Testing and Materials 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 test pit logs. Grain Size Analysis A grain size analysis indicates the range in diameter of soil particles included in a particular sample. Grain size analyses for the greater than 75 micrometer portion of the samples were performed in accordance with American Society of Testing and Materials D422 Standard Test Method for Particle-Size Analysis of Soils (ASTM D422) on three of the samples, the results of which are attached in Appendix A.
Project Name: Duvall Sherlock Storage Test Pit No.: TP-1 Project Number: 2016-185 Sheet 1 of 1 Client: Sherlock Investments - Duvall, LLC
Date(s) Excavated: 11/21/2016 Logged By ELW Surface Conditions: Gravel
Excavation Method: Excavator Bucket Size: N/A Total Depth of Excavation: 4.5 feet bgs
Approximate Excavator Type: Tracked Excavator Excavating Contractor: Kelly's Excavating, Inc. 84 Surface Elevation Sampling Groundwater Level: Not Encountered Grab Compaction Method Bucket Method(s)
Test Pit Backfill: Cuttings Location 14441 State Route 203, Duvall, Washington
MATERIAL DESCRIPTION REMARKS AND OTHER TESTS Elevation (feet) Depth (feet) Sample Type Sample Number USCS Symbol Graphic Log 84 0 Fill Gray GRAVEL with some sand, medium dense, moist (Fill) ML Brown sandy SILT, stiff, moist to wet
ML Tan mottled SILT with some sand, stiff, moist 23% moisture
Becomes gray, moist to wet 32% moisture 79% fines Contains occasional cobbles and boulders
Test Pit terminated at 4.5' due to boulder obstruction 79 5
74 10
69 15
The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name: Duvall Sherlock Storage Test Pit No.: TP-2 Project Number: 2016-185 Sheet 1 of 1 Client: Sherlock Investments - Duvall, LLC
Date(s) Excavated: 11/21/2016 Logged By ELW Surface Conditions: Gravel
Excavation Method: Excavator Bucket Size: N/A Total Depth of Excavation: 7 feet bgs
Approximate Excavator Type: Tracked Excavator Excavating Contractor: Kelly's Excavating, Inc. 83 Surface Elevation Sampling Groundwater Level: Not Encountered Grab Compaction Method Bucket Method(s)
Test Pit Backfill: Cuttings Location 14441 State Route 203, Duvall, Washington
MATERIAL DESCRIPTION REMARKS AND OTHER TESTS Elevation (feet) Depth (feet) Sample Type Sample Number USCS Symbol Graphic Log 83 0 Fill Brown sandy GRAVEL, medium dense, moist (Fill)
Fill Brown silty SAND, loose to medium dense, moist to wet (Fill) Contains wood debris
ML Tan SILT with some sand, stiff, moist
33% moisture
CL-ML Gray silty CLAY, stiff, moist 41% moisture
ML Brown sandy SILT with some gravel, stiff, moist 78 5 Occasional cobble and boulder 15% moisture
SM Gray silty SAND with trace gravel, dense, moist 13% moisture Lightly cemented, 47% fines 11% moisture Test Pit terminated at 7'
73 10
68 15
The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name: Duvall Sherlock Storage Test Pit No.: TP-3 Project Number: 2016-185 Sheet 1 of 1 Client: Sherlock Investments - Duvall, LLC
Date(s) Excavated: 11/21/2016 Logged By ELW Surface Conditions: Gravel and Saw Dust
Excavation Method: Excavator Bucket Size: N/A Total Depth of Excavation: 13 feet bgs
Approximate Excavator Type: Tracked Excavator Excavating Contractor: Kelly's Excavating, Inc. 78 Surface Elevation Sampling Groundwater Level: Seepage at 9' Grab Compaction Method Bucket Method(s)
Test Pit Backfill: Cuttings Location 14441 State Route 203, Duvall, Washington
MATERIAL DESCRIPTION REMARKS AND OTHER TESTS Elevation (feet) Depth (feet) Sample Type Sample Number USCS Symbol Graphic Log 78 0 Fill Gray sandy GRAVEL, medium dense, moist (Fill)
Fill Gray silty SAND with some gravel, very dense, moist (Fill)
7% moisture Trace wood and brick debris
Contains concrete rubble Becomes medium dense
73 5 Light caving, contains garbage debris
High amount of garbage debris
Localized groundwater seepage
68 10
ML Tan SILT with some sand, very stiff, moist
29% moisture Test Pit terminated at 13'
63 15
The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name: Duvall Sherlock Storage Test Pit No.: TP-4 Project Number: 2016-185 Sheet 1 of 1 Client: Sherlock Investments - Duvall, LLC
Date(s) Excavated: 11/21/2016 Logged By ELW Surface Conditions: Blackberries
Excavation Method: Excavator Bucket Size: N/A Total Depth of Excavation: 9 feet bgs
Approximate Excavator Type: Tracked Excavator Excavating Contractor: Kelly's Excavating, Inc. 76 Surface Elevation Sampling Groundwater Level: Not Encountered Grab Compaction Method Bucket Method(s)
Test Pit Backfill: Cuttings Location 14441 State Route 203, Duvall, Washington
MATERIAL DESCRIPTION REMARKS AND OTHER TESTS Elevation (feet) Depth (feet) Sample Type Sample Number USCS Symbol Graphic Log 76 0 4" topsoil Fill Brown sandy GRAVEL, medium dense, moist (Fill)
Fill Brown sandy GRAVEL with some silt, loose to medium dense, moist to wet (Fill) Contains asphalt debris
Moderate caving
71 5 8% fines 11% moisture
Heavy caving
Test Pit terminated due to caving
66 10
61 15
The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 Project Name: Duvall Sherlock Storage Key to Logs Project Number: 2016-185 Sheet 1 of 1 Client: Sherlock Investments - Duvall, LLC
MATERIAL DESCRIPTION REMARKS AND OTHER TESTS Elevation (feet) Depth (feet) Sample Type Sample Number USCS Symbol Graphic Log 1 2 3 4 5 6 7 8
COLUMN DESCRIPTIONS 1 Elevation (feet): Elevation (MSL, feet). 5 USCS Symbol: USCS symbol of the subsurface material. 2 Depth (feet): Depth in feet below the ground surface. 6 Graphic Log: Graphic depiction of the subsurface material 3 Sample Type: Type of soil sample collected at the depth interval encountered. shown. 7 MATERIAL DESCRIPTION: Description of material encountered. 4 Sample Number: Sample identification number. May include consistency, moisture, color, and other descriptive text. 8 REMARKS AND OTHER TESTS: Comments and observations regarding drilling or sampling made by driller or field personnel.
FIELD AND LABORATORY TEST ABBREVIATIONS CHEM: Chemical tests to assess corrosivity PI: Plasticity Index, percent COMP: Compaction test SA: Sieve analysis (percent passing No. 200 Sieve) CONS: One-dimensional consolidation test UC: Unconfined compressive strength test, Qu, in ksf LL: Liquid Limit, percent WA: Wash sieve (percent passing No. 200 Sieve)
MATERIAL GRAPHIC SYMBOLS
SILTY CLAY (CL-ML) SILT, SILT w/SAND, SANDY SILT (ML)
AF Silty SAND (SM)
TYPICAL SAMPLER GRAPHIC SYMBOLS OTHER GRAPHIC SYMBOLS
Auger sampler CME Sampler Pitcher Sample Water level (at time of drilling, ATD) Water level (after waiting) 2-inch-OD unlined split Bulk Sample Grab Sample spoon (SPT) Minor change in material properties within a stratum 3-inch-OD California w/ 2.5-inch-OD Modified Shelby Tube (Thin-walled, Inferred/gradational contact between strata brass rings California w/ brass liners fixed head) ? Queried contact between strata
GENERAL NOTES
1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be gradual. Field descriptions may have been modified to reflect results of lab tests. 2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative of subsurface conditions at other locations or times.
The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011 THE RILEY GROUP, INC. PHONE: (425) 415-0551 17522 Bothell Way NE FAX: (425) 415-0311 Bothell, WA 98011
GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Duvall Sherlock Storage SAMPLE ID/TYPE TP-1 PROJECT NO. 2016-185 SAMPLE DEPTH 2.5 TECH/TEST DATE EW/CM 12/1/2016 DATE RECEIVED 11/21/2016 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 292.9 Weight Of Sample (gm) 226.1 Wt Dry Soil & Tare (gm) (w2) 226.1 Tare Weight (gm) 16.0 Weight of Tare (gm) (w3) 16.0 (W6) Total Dry Weight (gm) 210.1 Weight of Water (gm) (w4=w1-w2) 66.8 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 210.1 Cumulative Moisture Content (%) (w4/w5)*100 32 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 16.0 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0" 16.0 0.00 0.00 100.00 coarse gravel % F GRAVEL 1.1 2.5" coarse gravel % C SAND 1.3 2.0" coarse gravel % M SAND 7.6 1.5" 16.0 0.00 0.00 100.00 coarse gravel % F SAND 11.1 1.0" coarse gravel % FINES 78.8 0.75" 16.0 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 17.9 1.90 0.90 99.10 fine gravel D10 (mm) #4 18.3 2.30 1.09 98.91 coarse sand D30 (mm) #10 21.1 5.10 2.43 97.57 medium sand D60 (mm) #20 medium sand Cu #40 37.1 21.10 10.04 89.96 fine sand Cc #60 fine sand #100 49.8 33.80 16.09 83.91 fine sand #200 60.5 44.50 21.18 78.82 fines PAN 226.1 silt/clay
12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 100 % 90 80 P 70 A 60 50 S 40 S 30 I 20 N 10 G 0 1000 100 10 1 0.1 0.01 0.001
Grain size in millimeters
DESCRIPTION SILT with some sand
USCS ML
Prepared For: Sherlock Investments - Duvall, LLC Reviewed By: RW THE RILEY GROUP, INC. PHONE: (425) 415-0551 17522 Bothell Way NE FAX: (425) 415-0311 Bothell, WA 98011
GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Duvall Sherlock Storage SAMPLE ID/TYPE TP-2 PROJECT NO. 2016-185 SAMPLE DEPTH 6.5' TECH/TEST DATE EW/CM 12/1/2016 DATE RECEIVED 11/21/2016 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 237.4 Weight Of Sample (gm) 215.2 Wt Dry Soil & Tare (gm) (w2) 215.2 Tare Weight (gm) 15.7 Weight of Tare (gm) (w3) 15.7 (W6) Total Dry Weight (gm) 199.5 Weight of Water (gm) (w4=w1-w2) 22.2 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 199.5 Cumulative Moisture Content (%) (w4/w5)*100 11 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.7 0.00 0.00 100.00 cobbles % C GRAVEL 0.0 3.0" 15.7 0.00 0.00 100.00 coarse gravel % F GRAVEL 9.7 2.5" coarse gravel % C SAND 3.5 2.0" coarse gravel % M SAND 12.0 1.5" 15.7 0.00 0.00 100.00 coarse gravel % F SAND 27.5 1.0" coarse gravel % FINES 47.3 0.75" 15.7 0.00 0.00 100.00 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 29.1 13.40 6.72 93.28 fine gravel D10 (mm) #4 35.1 19.40 9.72 90.28 coarse sand D30 (mm) #10 42.0 26.30 13.18 86.82 medium sand D60 (mm) #20 medium sand Cu #40 66.0 50.30 25.21 74.79 fine sand Cc #60 fine sand #100 101.3 85.60 42.91 57.09 fine sand #200 120.8 105.10 52.68 47.32 fines PAN 215.2 silt/clay
12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 100 % 90 80 P 70 A 60 50 S 40 S 30 I 20 N 10 G 0 1000 100 10 1 0.1 0.01 0.001
Grain size in millimeters
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For: Sherlock Investments - Duvall, LLC Reviewed By: RW THE RILEY GROUP, INC. PHONE: (425) 415-0551 17522 Bothell Way NE FAX: (425) 415-0311 Bothell, WA 98011
GRAIN SIZE ANALYSIS ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Duvall Sherlock Storage SAMPLE ID/TYPE TP-4 PROJECT NO. 2016-185 SAMPLE DEPTH 5' TECH/TEST DATE EW/CM 12/1/2016 DATE RECEIVED 11/21/2016 WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture Wt Wet Soil & Tare (gm) (w1) 580.9 Weight Of Sample (gm) 526.8 Wt Dry Soil & Tare (gm) (w2) 526.8 Tare Weight (gm) 15.8 Weight of Tare (gm) (w3) 15.8 (W6) Total Dry Weight (gm) 511.0 Weight of Water (gm) (w4=w1-w2) 54.1 SIEVE ANALYSIS Weight of Dry Soil (gm) (w5=w2-w3) 511.0 Cumulative Moisture Content (%) (w4/w5)*100 11 Wt Ret (Wt-Tare) (%Retained) % PASS +Tare {(wt ret/w6)*100} (100-%ret) % COBBLES 0.0 12.0" 15.8 0.00 0.00 100.00 cobbles % C GRAVEL 12.3 3.0" 15.8 0.00 0.00 100.00 coarse gravel % F GRAVEL 42.9 2.5" coarse gravel % C SAND 14.7 2.0" coarse gravel % M SAND 14.9 1.5" 15.8 0.00 0.00 100.00 coarse gravel % F SAND 7.3 1.0" coarse gravel % FINES 8.0 0.75" 78.8 63.00 12.33 87.67 fine gravel % TOTAL 100.0 0.50" fine gravel 0.375" 206.1 190.30 37.24 62.76 fine gravel D10 (mm) 0.15 #4 297.9 282.10 55.21 44.79 coarse sand D30 (mm) 2 #10 372.9 357.10 69.88 30.12 medium sand D60 (mm) 8.5 #20 medium sand Cu 56.7 #40 448.8 433.00 84.74 15.26 fine sand Cc 3.1 #60 fine sand #100 475.1 459.30 89.88 10.12 fine sand #200 485.9 470.10 92.00 8.00 fines PAN 526.8 silt/clay
12" 3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200 100 % 90 80 P 70 A 60 50 S 40 S 30 I 20 N 10 G 0 1000 100 10 1 0.1 0.01 0.001
Grain size in millimeters
DESCRIPTION Sandy GRAVEL with some silt
USCS GP-GM
Prepared For: Sherlock Investments - Duvall, LLC Reviewed By: RW
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Listing ID: 6647 Main Listing Information Listing ID: 6647 2014 Category: 4A Waterbody Name: SNOQUALMIE RIVER 2012 Category: 4A Medium: Water 2008 Category: 4A Parameter: Bacteria 2004 Category: 4A WQI Project: Snoqualmie River Watershed On 1998 303(d) List?: N Multiparameter TMDL Designated Use: None Assigned On 1996 303(d) List?: N Assessment Unit Assessment Unit ID: 17110010000189 Location Identification Counties: King WRIA: 7 - Snohomish Waterbody ID (WBID): None Assigned Waterbody Class: RA Town/Range/Section (Legacy): 26N-6E-13 Basis Joy, 1991. 2 of 6 single samples exceeding the criterion at RM 9.8 between 7/89 and 9/89; Remarks Modified Modified Remark Visibility By On Part of Snoqualmie River TMDL. Approved 7/3/96. Ken Koch 10/30/2012 Public Data is only available in hardcopy format. Ken Koch 10/30/2012 Public The water segment is listed as Category 5 based on the 1998 Ken Koch 10/30/2012 Public assessment. EIM No EIM Records Entered
https://fortress.wa.gov/ecy/approvedwqa/ApprovedPrintListing.aspx?LISTING_ID=6647 2/ 24/ 2017 7. OTHER PERMITS
Permitting for the project will be completed through the City of Duvall. The City will require (at a minimum) the following permits: Master Use Permit Site Plan Review Application Conditional Use Permit SEPA Review Grading and Utilities Permit; and, Building Permit
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 21 Duvall, WA 8. CSWPP PLAN ANALYSIS AND DESIGN
A Temporary Sedimentation and Erosion Control Plan and supporting calculations have been provided in the plans. A copy of the plan and calculation are attached in Appendix A.
8.1: ESC PLAN ANALYSIS AN D DESIGN Since flow control is not required for the project temporary storage facilities will be provided for containment and treatment of construction runoff. Discharges during construction will be monitored to comply with the City’s approved NPDES permit.
8.2: SWPPS PLAN DESIGN The project will provide BMPs per 2014 Stormwater Management Manual for Western Washington Volume II Chapter 4 Best Management Practices to prevent erosion and offsite sediment transport during construction until the site is fully stabilized. Generally, below grade detention tanks will be installed to mitigate flow rates for runoff from the developed site. The detention tanks will be installed during the early periods of construction, during the dry summer months. Once completed, the permanent flow control facility will be implemented to manage construction stormwater by collecting site runoff and discharging to either permanent or temporary stormwater conveyance systems. A summary of additional erosion control measures, modeled from Volume II of the Manual is shown below.
Prior to beginning land disturbing activities, all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area will be clearly marked to prevent damage and offsite impacts. A stabilized entrance for construction vehicle access will be provided to minimize the tracking of sediment onto public roads. Entrance and exit shall be limited to one route, if possible. If sediment is tracked offsite, public roads shall be cleaned thoroughly at the end of each day, or more frequently during wet weather, if necessary. In order to prevent erosion and trap sediments within the project site, the following BMPs will be used approximately as shown on the ESC plan:
• Clearing limits will be marked by fencing in accordance with BMP C103 High Visibility Fencing or other means on the ground. • A construction entrance will be constructed and graveled immediately in accordance with BMP C105 Stabilized Construction Entrance/Exit. Dispersion trenches will be placed according to flow control requirements. Cleared areas accepting sheet flow from the driveway and parking area will be seeded and mulched per BMP C120 Temporary and Permanent Seeding and BMP C121 Sodding respectively. • Silt fencing will be placed along slope contours at the downslope limit of site, perpendicular to the flow path per C233 Silt Fence. • Mulch will be spread over all cleared areas of the site when they are not being worked. Mulch will consist of air-dried straw and chipped site vegetation per BMP C121 Mulching.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 22 Duvall, WA Runoff from disturbed areas will pass through sediment control measures to prevent the transport of sediment downstream until the disturbed area is fully stabilized. Sediment controls will be installed as one of the first steps in grading and will be functional before other land disturbing activities take place. Sediment control BMPs that may be used consist of:
Silt Fence per BMP C233 Silt Fence Storm Drain Inlet Protection per BMP C220 Storm Drain Inlet Protection Straw wattles in accordance with BMP C235 Wattles
All exposed and unworked soils will be stabilized through the application of cover measures to protect the soil from the erosive forces of raindrop impact, flowing water, and wind erosion. One or more of the following cover measures may be used to meet this requirement during the construction phase:
Mulching per BMP C121 Mulching Nets and Blankets per BMP C122 Nets and Blankets Plastic Covering per BMP C123 Plastic Covering Seeding per BMP C120 Temporary and Permanent Seeding Sodding per BMP C124 Sodding
Cover measures will be applied in accordance with the following requirements: 1. Cover measures must be installed if an area is to remain unworked for more than seven days during the dry season (May 1 to September 30) or for more than two consecutive working days during the wet season (October 1 to April 30). These time limits may be relaxed if an area poses a low risk of erosion due to soil type, slope gradient, anticipated weather conditions, or other factors. Conversely, the project may reduce these time limits if site conditions warrant greater protection (e.g., adjacent to significant aquatic resources or highly erosive soils) or if significant precipitation is expected. 2. Any area to remain unworked for more than 30 days shall be seeded or sodded unless determined that winter weather makes vegetation establishment infeasible. During the wet season, exposed ground slopes and stockpile slopes with an incline of 3 horizontal to 1 vertical (3H:1V) or steeper and with more than ten feet of vertical relief shall be covered if they are to remain unworked for more than 12 hours. Also during the wet season, the material necessary to cover all disturbed areas must be stockpiled on site. The intent of these cover requirements is to have as much area as possible covered during any period of precipitation.
Stormwater runoff originating on the site and/or entering the site from offsite areas will be controlled so as to minimize erosion of disturbed areas and exposed cut and fill slopes. The following runoff control measures may be used as needed per the conditions of use and specifications for each measure:
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 23 Duvall, WA • Interceptor Dikes and Swales per BMP C200 Interceptor Dike and Swale • Grass lined channels per BMP C201 Grass-Lined Channels • Pipe Slope Drain per C204 Pipe Slope Drains
Prior to final construction approval, the project site will be stabilized to prevent sediment-laden water from leaving the project site after project completion. All disturbed areas of the project site will be vegetated or otherwise permanently stabilized. At a minimum, disturbed areas will be seeded and mulched to ensure that sufficient cover will develop shortly after final approval. All temporary ESC measures will be removed within 30 days after final site stabilization is achieved or after the temporary measures are no longer needed. Trapped sediment will be removed or stabilized onsite. Disturbed soil areas resulting from removal of measures or vegetation will be permanently stabilized with seeding or sodding.
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 24 Duvall, WA 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT
• Bond Quantities Worksheet (Will be provided at a later date) • Flow Control and Water Quality Facility Summary Sheet and Sketch (Will be provided at a later date) • Declaration of Covenant for Privately Maintained Flow Control Facilities and WQ Facilities (Will be provided at a later date) • Declaration of Covenant for Privately Maintained Flow Control BMPs (Will be provided at a later date)
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 25 Duvall, WA 10. OPERATIONS AND MAINTENANCE MANUAL
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 25 Duvall, WA KING COUNTY DRAINAGE MAINTENANCE STANDARDS FOR COMMERCIAL AND MULTIFAMILY DRAINAGE FACILITIES
Definitions, Defects & Maintenance Necessary to Bring to Standard
June 2008
Contents
A. Type I Catch Basin...... 4 B. Type II Catch Basin...... 5 C. Flow Restrictor...... 7 D. Debris Barrier...... 8 E. Energy Dissipater/Dispersion Trench...... 9 F. Pipe/Culvert...... 10 G. Ditch...... 10 H. Fencing...... 11 I. Access Road...... 13 J. Other—Specific to Ponds (Including Infiltration Ponds)...... 14 K. Other—Specific to Tanks (Including Infiltration Tanks/Vaults)...... 17 L. Other—Specific to Wet Vaults...... 18 M. Other—Specific to Bioswales...... 20 N. Other—Specific to Wet Ponds...... 22
Appendix A: Disposal of Trash Debris and Sediment...... 25
Appendix B: Facility Sketches
Figure B-1—Typical Type I Catch Basin...... 31 Figure B-2—Typical II Catch Basin...... 32 Figure B-3—Typical Flow Restrictor (T-section)...... 33 Figure B-4—Typical Detention Pond...... 34 Figure B-5—Typical Infiltration Pond...... 35 Figure B-6—Typical Detention Tank...... 36 Figure B-7—Typical Detention Vault...... 37 Figure B-8—Typical Wet Vault...... 38 Figure B-9—Typical Bioswale...... 39 Figure B-10—Typical Wetpond...... 40 Figure B-11—Typical Infiltration Tank...... 41
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page A. Type I Catch Basin (See Figure B-1 in Appendix) Definition: An underground concrete water receiving inlet, rectangular in shape (approximately 3’ X 2’ X 4’ deep) with a slotted iron grate on top to inlet water or a solid rectangular cover. Water may also enter/exit through cul- verts visible in the side walls of basin. Invert refers to the lowest point of a pipe where it enters or exits a catch basin.
Defect Number & Defect:
A-1 General—Trash & Debris (Including Sediment) Blocking Water From Entering Basin: Trash or debris covering any portion of the catch basin grate or blocking inlet grate to basin. Maintenance Necessary to Bring to Standard: Remove all trash, debris and sediment from in front of the catch basin inlet. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
A-2 General—Trash & Debris (Including Sediment): Trash, debris and sediment (in the basin) that exceeds one-third the depth from the bottom of the basin to invert of the lowest pipe into or out of the basin. This is the most common maintenance requirement. Maintenance Necessary to Bring to Standard: Remove all trash, debris and sediment from the catch basin. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
A-3 General—Trash & Debris (Including Sediment): Trash, debris and sediment in any inlet or outlet pipe blocking more than one-third of its height. Maintenance Necessary to Bring to Standard: Remove all trash, debris and sediment from inlet and outlet pipes. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
A-4 Structural—Structural Damage to Frame and/or Top Slab: Top concrete slab has holes larger than 2 square inches or cracks wider than 1/4 inch (intent is to make sure all material is running into the basin through the grate). Maintenance Necessary to Bring to Standard: Repair top slab so that it is free of holes and cracks.
A-5 Structural—Frame not sitting flush on top slab, i.e., separation of more than 3/4 inch of the frame from the top slab. Maintenance Necessary to Bring to Standard: Repair so that frame is sitting flush on top slab.
A-6 Structural—Cracks in Basin Walls/Bottom: Cracks wider than 1/2 inch, any evidence of soil particles or water entering catch basin through cracks, or maintenance person judges that structure is unsound. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
A-7 Structural—Cracks in Basin Around Inletting Culverts: Cracks wider than 1/2 inch at the joint of any inlet/outlet pipe or any evidence of soil particles or water entering catch basin through cracks. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
A-8 Structural—Settlement/Misalignment: Basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
Page King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities A-9 General—Pollution: Presence of any pollutants (including paint, auto fluids, grease and food waste) or flammable materials. Maintenance Necessary to Bring to Standard: Remove contaminants so that none are present. Contact the Waste Characterization Program at 206-296-4633 to determine how to dispose of pollutants and flammable material. Also, contact Water and Land Resources at 206-296-1900 for a water quality site consultation to eliminate the source of the pollution.
A-10 Catch Basin Cover—Not in Place: Cover is missing or only partially in place. Any open catch basin requires maintenance. Maintenance Necessary to Bring to Standard: Replace missing cover or repair catch basin cover so that it is closed.
A-11 Metal Grates—Safety Hazard: Grate with opening wider than 7/8 inch. Maintenance Necessary to Bring to Standard: Repair grate openings so that they meet design standards.
A-12 Metal Grates—Trash & Debris: Trash and debris that is blocking grate surface. Maintenance Necessary to Bring to Standard: Remove all trash and debris from grate. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
A-13 Metal Grates—Damaged or Missing: Grate is missing or has broken members. Maintenance Necessary to Bring to Standard: Repair or replace grate so that it is in place and meets design standards.
B. Type II Catch Basin (See Figure B-2 in Appendix) Definition: A round concrete underground basin (4’-8’ in diameter; 6’ deep or deeper); may contain a Flow Restrictor Oil Pollution (FROP) control device or a T-section with a specifically sized orifice(s) to control release rates or a spill control device. These basins are also required when larger diameter culverts are used.
Defect Number & Defect:
B-1 General—Trash & Debris (Including Sediment): Trash, debris and sediment covering the catch basin grate or is blocking any portion of inlet to basin. Maintenance Necessary to Bring to Standard: Remove trash, debris and sediment so that none is located immediately in front of catch basin inlet. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
B-2 General—Trash & Debris (Including Sediment): Trash, debris and sediment (in the basin) that exceeds one-third the depth from the bottom of the basin to invert of the lowest pipe into or out of the basin. This is the most common maintenance requirement. Maintenance Necessary to Bring to Standard: Remove all trash, debris and sediment from the catch basin. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page B-3 General—Trash & Debris (Including Sediment): Trash, debris and sediment in any inlet or outlet pipe blocking more than one-third of its height. Maintenance Necessary to Bring to Standard: Remove all trash, debris and sediment from inlet and outlet pipes. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
B-4 Structural—Structural Damage to Frame and/or Top Slab: Top slab has holes larger than 2 square inches or cracks wider than 1/4 inch (intent is to make sure all material is running into the basin). Maintenance Necessary to Bring to Standard: Repair top slab so that it is free of holes and cracks.
B-5 Structural—Frame Not Sitting Flush on Top Slab, i.e., separation of more than 3/4 inch of the frame from the top slab. Maintenance Necessary to Bring to Standard: Repair so that frame is sitting flush on top slab.
B-6 Structural—Cracks in Basin Walls/Bottom: Cracks wider than 1/2 inch and longer than 3 feet, any evidence of soil particles or water entering catch basin through cracks, or maintenance person judges that structure is unsound. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
B-7 Structural—Cracks in Pipe Joints: Cracks wider than 1/2 inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles or water entering catch basin through cracks. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
B-8 Structural—Settlement/Misalignment: Basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Maintenance Necessary to Bring to Standard: Replace or repair basin to design standards.
B-9 General—Pollution: Presence of any chemical pollutants or flammable materials. Maintenance Necessary to Bring to Standard: Remove contaminants so that none are present. Contact the Waste Characterization program at 206-296-4633 to determine how to dispose of pollutants and flammable material. Also, contact Water and Land Resources at 206-296-1900 for a water quality site consultation to eliminate the source of the pollution.
B-10 Catch Basin Cover—Not in Place: Cover is missing or only partially in place. Any open catch basin requires maintenance. Maintenance Necessary to Bring to Standard: Repair or replace catch basin cover so that it is closed.
B-11 Metal Grates—Safety Hazard: Grate with opening wider than 7/8 inch. Maintenance Necessary to Bring to Standard: Repair grate openings so that they meet design standards.
B-12 Metal Grates—Trash & Debris: Trash and debris that is blocking grate surface. Maintenance Necessary to Bring to Standard: Remove all trash and debris from grate. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
Page King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities B-13 Metal Grates—Damaged or Missing: Grate is missing or has broken members. Maintenance Necessary to Bring to Standard: Repair or replace grate so that it is in place and meets design standards.
B-14 Ladder—Rungs Unsafe: Maintenance person judges that ladder is unsafe due to missing rungs, misalignment, rust, or cracks. Maintenance Necessary to Bring to Standard: Repair ladder so that it meets design standards and allows maintenance person safe access.
C. Flow Restrictor (See Figure B-3 in Appendix) Definition: A facility such as a Flow Restrictor Oil Pollution (FROP) control device with a specifically sized orifice(s) to control release rates or a spill control device. Usually located in a Type II Catch Basin/Control Manhole; designated as “CS,” “CS/CB,” or “CS/MH” on your site plan. There may be a vertical culvert at the outlet (“T”) with additional elbow orifice inlets (secondary orifice).
Defect Number & Defect:
C-1 General—Trash & Debris (Includes Sediment): Distance between debris buildup and bottom of orifice plate is less that 1-1/2 feet (18 inches). Similar to B-2. Maintenance Necessary to Bring to Standard: Remove all trash and debris. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
C-2 General—Structural Damage: Structure is not securely attached to manhole wall (outlet pipe structure should support at least 1,000 pounds of up or down pressure); and/or structure is not in upright position (allow up to 10% from plumb). (Structure is usually secured with banding material.) Maintenance Necessary to Bring to Standard: Repair structure to be securely attached to wall so that outlet pipe supports at least 1,000 pounds of up or down pressure; and ensure outlet pipe is in correct position.
C-3 General—Structural Damage: Connections to outlet pipe are not watertight and show signs of rust or deteriorated grout. Maintenance Necessary to Bring to Standard: Repair connections to outlet pipe so that they are watertight; repair or replace structure so that it works as designed.
C-4 General—Structural Damage: Any holes—other than designed holes—in the structure. Maintenance Necessary to Bring to Standard: Repair holes so that structure has no holes other than designed holes.
C-5 Cleanout Gate—Damaged or Missing: Cleanout gate is not watertight or is missing. Maintenance Necessary to Bring to Standard: Repair or replace gate so that it is watertight and works as designed.
C-6 Cleanout Gate—Will Not Open or Opens with Difficulty:Gate cannot be moved up and down by one person. Maintenance Necessary to Bring to Standard: Repair gate so that it moves up and down easily and is watertight.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page C-7 Cleanout Gate—Damaged or Missing Chain or Rod: Chain or rod leading to gate is missing or damaged (must be accessible from street level). Maintenance Necessary to Bring to Standard: Repair or replace chain or rod so that it is in place and works as designed.
C-8 Cleanout Gate—Rusted: Gate is rusted over 50% of its surface area. Maintenance Necessary to Bring to Standard: Repair or replace gate to meet design standards.
C-9 Orifice Plate (Including Secondary Orifices)—Damaged or Missing: Control device is not working properly due to missing, out of place, or bent orifice plate; or secondary orifice elbows have become loosened from structure. Maintenance Necessary to Bring to Standard: Repair or replace orifice plate so that it is in place and works as designed.
C-10 Orifice Plate (Including Secondary Orifices)—Trash and Debris: Any trash, debris, sediment, or vegetation blocking the plate Maintenance Necessary to Bring to Standard: Remove all obstructions so that orificate plate works as designed. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment. H. C-10 Secondary Orifices (Elbow Restrictors)—Integrity: Secondary orifice is securely attached and properly functioning Maintenance Necessary to Bring to Standard: Repair secondary orifice to be properly functioning.
C-11 Overflow Pipe—Obstructions: Any trash or debris blocking (or having the potential of blocking) the overflow pipe. (Overflow pipe is at the top of FROP, “T-section” device or spill control device.) Maintenance Necessary to Bring to Standard: Remove trash and debris so that the overflow pipe is free of all obstructions and works as designed. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
D. Debris Barrier Definition: Metal trash rack usually located over the entrance to a pipe or culvert. A debris barrier may also be a conical structure constructed of metal bars and/or rods place over a Type II Catch Basin.
Defect Number & Defect:
D-1 General—Trash & Debris: Trash or debris that is plugging of the openings in the barrier. Maintenance Necessary to Bring to Standard: Remove trash or debris so that barrier is clear to receive capacity flow. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
D-2 General—Damaged/Bars: Bars are bent out of shape more than 3 inches. Maintenance Necessary to Bring to Standard: Repair or replace bars so that they are in place with no bends more than 3/4 inch.
Page King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities D-3 General—Missing Bars: Bars are missing, or entire barrier is missing. Maintenance Necessary to Bring to Standard: Repair or replace bars according to design standards.
D-4 General—Bars are loose and rust is causing 50% deterioration to any part of barrier. Maintenance Necessary to Bring to Standard: Repair or replace barrier according to design standards.
E. Energy Dissipater/Dispersion Trench Definition: A rock pad constructed at inlets/outlets to prevent erosion (Energy Dissipater), or a catch basin used to slow fast flowing runoff (Energy Dissipater), or a constructed percolation trench to disperse outletting flows over a large area (Dispersion Trench). Catch basins may be a part of the dispersion trench; see Type I or Type II Catch Basins (Items A and B) for maintenance requirements.
Defect Number & Defect:
E-1 Rock Pad—Missing or Moved Rock: One layer or less of rock exists above native soil in area five square feet or larger, or any exposure of native soil. Maintenance Necessary to Bring to Standard: Replace rocks to design standard.
E-2 Energy Dissipater—Needs Replacement: Visible signs of pad erosion, or plugged dispersion trenches. Maintenance Necessary to Bring to Standard: Replace energy dissipater.
E-3 Dispersion Trench—Pipe Plugged with Sediment: Accumulated sediment that exceeds 20% of the design depth. Maintenance Necessary to Bring to Standard: Clean/flush pipe so that it matches design. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
E-4 Dispersion Trench—Not Discharging Water Properly: Visual evidence of water discharging at concentrated points along trench (normal condition is a “sheet flow” of water along trench). Intent is to prevent erosion damage. Maintenance Necessary to Bring to Standard: Rebuild trench to design standards.
E-5 Dispersion Trench—Perforations Plugged: Over 1/2 of perforations in pipe are plugged with debris and sediment. Maintenance Necessary to Bring to Standard: Clean or replace perforated pipe. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
E-6 Dispersion Trench—Water Flows Out Top of “Distributor” Catch Basin: Water has been observed flowing out during any storm less than the design storm, or it is causing or appears likely to cause damage. Maintenance Necessary to Bring to Standard: Rebuild facility to design standards.
E-7 Dispersion Trench—Receiving Area Oversaturated: Water in receiving area is causing or has potential of causing landslide problems. Maintenance Necessary to Bring to Standard: Ensure that engineer’s evaluation of outlet function and soil stability is satisfactory.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page E-8 Dispersion Trench—Vegetation: Any vegetation growing on dispersion trench. Maintenance Necessary to Bring to Standard: Remove vegetation including root system.
F. Pipe/Culvert Definition: A conveyance culvert of varying diameter. May be constructed of concrete pipe (CP), corrugated metal pipe (CMP), or smooth wall high density polyethylene pipe (HDPP).
Defect Number & Defect:
F-1 General—Sediment & Debris: Accumulated sediment and/or debris that exceeds 20% of the diameter of the pipe. Maintenance Necessary to Bring to Standard: Clean pipe of all sediment and debris. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
F-2 Vegetation—Overgrowth: Vegetation that reduces free movement of water through pipes. Maintenance Necessary to Bring to Standard: Remove all vegetation so water flows freely through pipes.
F-3 Structural—Protective Coating is Damaged: Rust is causing more than 50% deterioration to any part of the pipe. Maintenance Necessary to Bring to Standard: Repair or replace pipe.
F-4 Structural—Joints: Joints are visibly misaligned, or culvert alignment is disrupted. Maintenance Necessary to Bring to Standard: Realign/reconnect affected culvert.
F-5 Structural—Damaged Pipe: Any dent that decreases the cross section area of pipe by more than 20%. Maintenance Necessary to Bring to Standard: Repair or replace pipe.
G. Ditch Definition: Conveyance system. May be U-shaped or trapezoidal with flat bottom. May be rock lined. A ditch is not the same as a bioswale (See Section M. Other—Specific to Bioswale).
Defect Number & Defect:
G-1 General—Trash & Debris: Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Maintenance Necessary to Bring to Standard: Clear trash and debris from ditch. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
G-2 General—Sediment: Accumulated sediment that exceeds 20% of the design depth. Maintenance Necessary to Bring to Standard: Clean/flush ditch of all sediment and debris so that it matches design. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
Page 10 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities G-3 Vegetation—Overgrowth: Vegetation that reduces free movement of water through ditch (vegetation taller than 8 inches or trees such as alders). Maintenance Necessary to Bring to Standard: Remove vegetation so that water flows freely through ditch or bioswale.
G-4 Side Slopes—Erosion Damage to Slopes: Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Maintenance Necessary to Bring to Standard: Stabilize slopes by using appropriate erosion control measure(s): for example, rock reinforcement, planting of grass, erosion control blankets, bonded fiber matrices or compaction.
G-5 Check Dams—Sedimentation: Silt deposition causes standing water behind check dam Maintenance Necessary to Bring to Standard: Replace check dam; remove silt. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
G-6 Rock Lined Ditch—Failure of Rock-Lined Ditch: Erosion or failure of rock slopes of ditch line. Maintenance Necessary to Bring to Standard: Replace/repair rock lining to reestablish ditch cross- section.
H. Fencing Definition: Six-foot-high fence, required by County if pond slopes are steeper than 3:1 to prohibit entry due to safety considerations in steep side slopes. Gates are a part of fencing.
Defect Number & Defect:
H-1 General—Missing or Broken Parts: Any defect in the fence that permits easy entry to a facility. Maintenance Necessary to Bring to Standard: Repair or replace parts to provide adequate security.
H-2 General—Missing or Broken Parts: Parts broken or missing that can be seen by the public that are below the appearance standards of the neighborhood. Maintenance Necessary to Bring to Standard: Repair or replace broken or missing parts to conform to the standards of the neighborhood.
H-3 General—Erosion: Erosion more than 4 inches deep and 12-18 inches wide permitting an opening under a fence. Maintenance Necessary to Bring to Standard: Fill in openings so that there are no openings under the fence that exceed 4 inches in height.
H-4 General—Damaged Parts: Posts out of plumb more than 6 inches. Maintenance Necessary to Bring to Standard: Correct position so that posts are plumb to within 1-1/2 inches.
H-5 General—Damaged Parts: Any part of fence (including posts, top rails, and fabric) more than 1 foot out of design alignment. Maintenance Necessary to Bring to Standard: Align fence so that it meets design standards.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 11 H-6 Chain Link Fences—Damaged Parts: Top rails bent more than 6 inches. Maintenance Necessary to Bring to Standard: Repair or replace top rails so that they are free of bends greater than 1 inch.
H-7 Chain Link Fences—Damaged Parts: Missing or loose tension wire. Maintenance Necessary to Bring to Standard: Repair or replace tension wire so that it is in place and holding fabric.
H-8 Chain Link Fences—Damaged Parts: Missing or loose barbed wire that is sagging more than 2-1/2 inches between posts. Maintenance Necessary to Bring to Standard: Repair or replace barbed wire so that it is in place with less than 3/4 inch sag between posts.
H-9 Chain Link Fences—Damaged Parts: Extension arm missing, broken, or bent out of shape more than 1-1/2 inches. Maintenance Necessary to Bring to Standard: Repair or replace extension arm so that it is in place with no bends larger than 3/4 inch.
H-10 Chain Link Fences—Deteriorated Paint or Protective Coating: Part or parts have a rusting or scaling condition that has affected structural adequacy. Maintenance Necessary to Bring to Standard: Repair posts or parts so that they are structurally adequate with a uniform protective coating.
H-11 Chain Link Fences or Gates—Openings in Fabric: Openings in fabric are such that an 8 inch diameter ball could fit through (intent is to prevent a small child from entering). Maintenance Necessary to Bring to Standard: Repair fabric so that there are no openings in fence.
H-12 Gates—Damaged or Missing Members: Missing gate or locking devices. Maintenance Necessary to Bring to Standard: Repair or replace gates and locking devices so that all are in place.
H-13 Gates—Damaged or Missing Members: Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Maintenance Necessary to Bring to Standard: Repair or replace hinges so that they are intact and lubed, and gate is working freely.
H-14 Gates—Damaged or Missing Members: Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Maintenance Necessary to Bring to Standard: Align gate so that it is vertical.
H-15 Gates (Chain Link)—Damaged or Missing Members: Missing stretcher bar, stretcher bands, and ties. Maintenance Necessary to Bring to Standard: Repair or replace stretcher bar, bands, and ties so that all are in place.
Page 12 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities I. Access Road Definition: Used to access control structure and other facility components. Minimum of 12 feet wide, may be constructed of asphalt, concrete, rock or other approved material.
Defect Number & Defect:
I-1 General—Support: Access road is capable of supporting trucks and maintenance equipment. Maintenance Necessary to Bring to Standard: Repair road to design standards.
I-2 General—Trash & Debris: Trash and debris exceeds 1 cubic foot per 1,000 square feet; i.e., trash and debris would fill up one standard-sized garbage can. Maintenance Necessary to Bring to Standard: Clear trash and debris from site. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
I-3 General— Pollution: Presence of any chemical pollutants or flammable materials. Maintenance Necessary to Bring to Standard: Remove contaminants so that none are present. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
I-4 Access—Blocked Roadway/Safety Hazard: Debris that could damage vehicle tires (glass or metal). Maintenance Necessary to Bring to Standard: Remove debris so that roadway is free of debris that could damage tires. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
I-5 Access—Blocked Roadway/Safety Hazard: Any obstructions or vegetation that reduces clearance above road surface to less than 14 feet. Maintenance Necessary to Bring to Standard: Remove obstructions or vegetation so that roadway overhead is clear to 14 feet high.
I-6 Access—Blocked Roadway/Safety Hazard: Any obstructions or vegetation restricting the access to a 10- to 12-foot width for a distance of more than 12 feet or at any point restricting access to less than a 10-foot width. Maintenance Necessary to Bring to Standard: Remove obstructions to allow at least a 12-foot access.
I-7 Road Surface—Settlement, Potholes, Soft Spots, or Ruts: Any surface defect that exceeds 6 inches in depth and 6 square feet in area. In general, any surface defect that hinders or prevents maintenance access. Maintenance Necessary to Bring to Standard: Repair road surface so that it is uniformly smooth with no evidence of settlement, potholes, soft spots, or ruts.
I-8 Road Surface—Vegetation: Trees growing or vegetation in excess of 6 inches. Maintenance Necessary to Bring to Standard: Remove trees, mow access road surface and/or remove trees.
I-9 Road Surface (if applicable)—Modular Grid Pavement Contamination: Build up of sediment mildly contaminated with petroleum hydrocarbons. Maintenance Necessary to Bring to Standard: Repair road surface so that it is uniformly smooth with no evidence of settlement, potholes, soft spots, or ruts. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 13 I-10 Shoulders & Ditches—Erosion Damage: Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Maintenance Necessary to Bring to Standard: Repair shoulder so that it is free of erosion and matching the surrounding road.
I-11 Shoulders & Ditches—Weeds & Brush: Weeds and brush exceed 18 inches in height or hinder maintenance access. Maintenance Necessary to Bring to Standard: Cut weeds and brush to 2 inches in height, or clear in such a way as to allow maintenance access.
J. Other—Specific to Ponds (Including Infiltration Ponds) (See Figures B-4 and B-5 in Appendix) Definition: A pond is a facility designed to temporarily store excess stormwater and slowly release it downstream to prevent flooding and erosion. An infiltration pond releases the stored stormwater to groundwater instead of downstream. A dike is a feature of a pond where earth has been built up to provide some portion of the side slope of the pond.
Defect Number & Defect:
J-1 General—Trash & Debris: Trash and debris exceed 1 cubic foot per 1000 square feet, or there is visual evidence of dumping, or any trash and debris that could block the pond outlet. Maintenance Necessary to Bring to Standard: Remove trash and debris from site. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-2 General—Contamination: Oil, gasoline, or other contaminants in any amount found that could: 1) cause damage to plant, animal, or marine life; 2) constitute a fire hazard; or 3) be flushed downstream during rain storms. Maintenance Necessary to Bring to Standard: Remove all contaminants so that none are present. Contact the Waste Characterization program at 206-296-4633 to determine how to dispose of pollutants and flammable material. Also, contact Water and Land Resources at 206-296-1900 for a water quality site consultation to eliminate the source of the pollution.
J-3 Vegetation—Unmowed Grass/Ground Cover (Not Including Infiltration—See J-15): If facility is located in private residential area, mowing is needed when grass exceeds 18 inches in height. In other areas, the general policy is to make the pond site match adjacent ground cover and terrain as long as there is no interference with the function of the facility. Maintenance Necessary to Bring to Standard: Mow grass/ground cover to 2 inches in height.
J-4 Dike—Rodent Holes: Any evidence of rodent holes, or any evidence of water piping through dike via rodent holes. Maintenance Necessary to Bring to Standard: Ensure that rodents are destroyed and holes are repaired.
J-5 Side Slopes and Dikes—Erosion: Eroded damage over 2 inches deep where cause of damage is still present or where there is potential for continued erosion. Maintenance Necessary to Bring to Standard: Stabilize slopes by using appropriate erosion control measure(s): for example, rock reinforcement, planting of grass or hydroseeding, erosion control blankets, bonded fiber matrices or compaction.
Page 14 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities J-6 Storage Area—Sediment (Except Infiltration—See J-12 and J-13): Accumulated sediment exceeds 10% of the designed pond depth. Periodic sediment removal is critical to proper pond function. Maintenance Necessary to Bring to Standard: Clean out sediment to designed pond shape and depth; reseed pond if necessary to control erosion. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-7 Storage Area—Liner Damage (If Applicable): Liner is visible and has more than three 1/4-inch holes in it. Maintenance Necessary to Bring to Standard: Repair or replace liner
J-8 Pond Dikes—Settlements: Any part of dike has settled 4 inches lower than the design elevation, or water is visibly piping (leaking) through dikes. Maintenance Necessary to Bring to Standard: Build dike back to the design elevation or repair piping.
J-9 Emergency Overflow/Spillway—Rock Missing, Erosion, or Obstruction: One layer or less of rock exists above native soil in area 5 square feet or larger; any exposure of native soil; or blockage by debris or vegetation. Maintenance Necessary to Bring to Standard: Replace rocks to design standards. Remove debris. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-10 Emergency Overflow/Spillway and Dikes Over 4 Feet in Height—Tree Growth: Tree growth on emergency spillways create blockage problems and may cause failure of the dike due to uncontrolled overtopping. Tree growth on dikes over 4 feet in height may lead to piping through the dike which could lead to failure of the dike. Maintenance Necessary to Bring to Standard: Remove tree. If root system is small (base less than 4 inches) the root system may be left in place. Otherwise the roots should be removed and the dike restored. A licensed civil engineer should be consulted for proper dike/spillway restoration.
J-11 Emergency Overflow/Spillway—Does Not Control Storm Flow: Emergency overflow or spillway is not large enough to handle heavy rain storms. Maintenance Necessary to Bring to Standard: Increase capacity (size) of emergency overflow so that there is no danger of flood damage to County roads or private property.
J-12 Storage Area—Sediment (Infiltration Only):A percolation test of facility indicates facility is only working at 90% of its designed capabilities, or water remains in pond for more than 24 hours after rain has stopped. Frequent sediment removal in infiltration facilities is important to insure proper function. Maintenance Necessary to Bring to Standard: Remove sediment and/or clean facility so that infiltration system works according to design. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
Note: Sediment accumulation of more than 0.25 inches per year may indicate excessive erosion is occurring upstream of the facility or that conveyance systems are not being properly maintained. The contributing drainage area should be checked for erosion problems or inadequate maintenance of conveyance systems if excessive sedimentation is noted in an infiltration facility.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 15 J-13 Rock Filters—Sediment & Debris: By visual inspection, little or no water flows through filter during heavy rain storms. Maintenance Necessary to Bring to Standard: Replace gravel in rock filter. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-14 Infiltration Facility Sump—Sump Filled with Sediment and Debris:Any sediment and debris filling vault to 10% of depth from sump bottom to bottom of outlet pipe or obstructing flow into the connector pipe. Maintenance Necessary to Bring to Standard: Clean out sump to design depth. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-15 Infiltration Facility Filter Bags (If Applicable)—Filled with Sediment and Debris:Sediment and debris fill bag more than 1/2 full. Maintenance Necessary to Bring to Standard: Replace filter bag or redesign system. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-16 Infiltration Facility Pre-settling Ponds and Vaults—Sediment:Sediment 6 inches or more. Maintenance Necessary to Bring to Standard: Sediment cleaned out to designed pond shape and depth or sediment is removed from vault. Ponds are reseeded if necessary to control erosion. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-17 Settling Ponds—Sediment (Infiltration Only): Pond contains 6 inches or more of sediment. Maintenance Necessary to Bring to Standard: Remove sediment completely. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-18 Vegetation (Infiltration Only)—Overgrowth: Vegetation such as trees, brush, grass and weeds impedes infiltration function, or when height exceeds 18 inches. Maintenance Necessary to Bring to Standard: Mow vegetation to 2 inches in height and remove clippings. Remove trees and bushes where they impact the infiltrating area of the pond.
J-19 Inlet/Outlet Pipe (Infiltration Only)—Plugged: Inlet/outlet pipe plugged with sediment and/or debris. Maintenance Necessary to Bring to Standard: Remove sediment and debris so that there is no clogging or blockage in the inlet and outlet piping. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-20 Dike—Settlement of Pond Dike (Infiltration Only):Any part of these components has settled 4 inches or lower than the design elevation, or inspector determines dike is unsound. Maintenance Necessary to Bring to Standard: Repair dike to specifications.
J-21 Rock Window (Infiltration Only)—Plugged: Rock Window of filter dike is plugged with sediment. Maintenance Necessary to Bring to Standard: Remove sediment from rock window. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
J-22 Access Ramp—In Useable Condition: Access ramp is capable of supporting trucks and equipment. Maintenance Necessary to Bring to Standard: Repair ramp deficiencies.
Page 16 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities K. Other—Specific to Tanks/Vaults (Including infiltration tanks/vaults) (See Figures B-6, B-7, and B-11 in Appendix) Definition: A tank or vault is an underground facility designed to store excess stormwater and slowly release it downstream to prevent flooding and erosion. An infiltration tank or vault releases the stored stormwater to groundwater instead of downstream.
Defect Number & Defect:
K-1 Storage Area—Plugged Air Vents: Any amount of blockage. (Vents are at upstream end of storage tank.) Maintenance Necessary to Bring to Standard: Remove debris and sediment from vents.
K-2 Storage Area (FC Tanks/Vaults Only)—Debris & Sediment: Accumulated sediment depth exceeds 10% of the diameter of the storage area for one-half the length of the storage tank, or any point depth exceeds 15% of diameter. Example: A 72-inch storage tank would require cleaning when sediment reaches a depth of 7 inches for more than one-half the length of the tank. Maintenance Necessary to Bring to Standard: Remove all sediment and debris from storage area. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
K-3 Storage Area—Joints Between Tank/Pipe Section: Any crack allowing material to be transported into facility. Maintenance Necessary to Bring to Standard: Seal all joints between tank/pipe sections.
K-4 Storage Area—Tank/Pipe Bent Out of Shape: Any part of tank/pipe is bent out of shape more than 10% of its design shape. Maintenance Necessary to Bring to Standard: Repair or replace tank/pipe to design.
K-5 Vault Structure—Damage to Wall, Frame, Bottom, and/or Top Slab: Cracks wider than ½-inch and any evidence of soil particles entering the structure through the cracks, or maintenance inspection personnel determines that the vault is not structurally sound. Maintenance Necessary to Bring to Standard: Vault replaced or repaired to design specifications.
K-6 Vault Structure—Damaged Pipe Joints: Cracks wider than ½-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the walls. Maintenance Necessary to Bring to Standard: Repair so no cracks more than 1/4 inch wide at any pipe joint.
K-7 Large Access Doors/Plates (If Applicable)—Gaps in Door or Plate: Large access doors not flat and/or access hole not completely covered. Note, however, that grated doors are acceptable. Maintenance Necessary to Bring to Standard: Repair so door/plate closes flat and covers access hole completely.
K-8 Large Access Doors/Plats (If Applicable)—Lifting Rings Missing, Rusted: Lifting rings not capable of lifting weight of door or lid. Maintenance Necessary to Bring to Standard: Repair so lifting ring is sufficient to remove lid.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 17 K-9 Plugged Air Vents (Infiltration Tanks Only):One-half of the end area of a vent is blocked at any point with debris and sediment. (Vents are at upstream end of storage tank.) Maintenance Necessary to Bring to Standard: Remove all debris and sediment from vents. If using a vendor, ensure that the vendor properly disposes of waste. If not using a vendor, call the King County Health Department Business Waste Line at (206) 296-3976 for information on how to dispose of waste.
K-10 Storage Area—Sediment (Infiltration Tanks and Vaults Only): Sediment depth exceeds 6 inches in depth. Maintenance Necessary to Bring to Standard: Remove all sediment from tank or vault bottom. If using a vendor, ensure that the vendor properly disposes of waste. If not using a vendor, call the King County Health Department Business Waste Line at (206) 296-3976 for information on how to dispose of waste.
K-11 Joints Between Tank/Pipe Section (Infiltration Tanks Only): Any crack allowing material to be transported into facility. Maintenance Necessary to Bring to Standard: Seal all joints between tank/pipe sections.
K-12 Tank/Pipe Bent out of Shape (Infiltration Tanks Only): Any part of tank/pipe is bent out of shape more than 10 percent of its design shape. Maintenance Necessary to Bring to Standard: Repair or replace tank/pipe to design.
Notes: 1. Sediment accumulation of more than .25 inches per year may indicate excessive erosion is occurring upstream of the facility or that conveyance systems are not being properly maintained. The contributing drainage area should be checked for erosion problems or inadequate maintenance of conveyance systems if excessive sedimentation is noted in an infiltration facility. 2. In order to assess the effectiveness of infiltration function, inspection is recommended of downspouts, drains and catch basins during a storm. Also, evaluate adjacent properties for damages caused by system failure. Slow water dissipation or system backups and flooding may indicate that an infiltration system is not adequately performing.
L. Other—Specific to Wet Vaults (See Figure B-8 in Appendix) Definition: A wet vault is an underground facility with a permanent pool of water that dissipates energy and improves the settling of particulate pollutants from incoming stormwater to improve water quality.
Defect Number & Defect:
L-1 Vault Area—Trash/debris Accumulated in Vault, Pipe, or Inlet/outlet: Includes floatables and non-floatables. Maintenance Necessary to Bring to Standard: Remove trash and debris from vault. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
L-2 Vault Area—Sediment Accumulation: Vault bottom contains sediment that exceeds the depth of the sediment zone plus 6 inches. Maintenance Necessary to Bring to Standard: Remove sediment from vault. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
Page 18 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities L-3 Vault Area—Oil Accumulation: Oil floating on surface of water in vault. Maintenance Necessary to Bring to Standard: Remove oil from vault. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
L-4 Vault Structure—Damage to Walls, Frame, Bottom, and/or Top Stab: Cracks wider than ½-inch and any evidence of soil particles entering the structure through the cracks, vault does not hold water, or maintenance inspection personnel determines that the vault is not structurally sound. Maintenance Necessary to Bring to Standard: Vault replaced or repaired to design specifications.
L-5 Vault Structure—Damaged Pipe Joints: Cracks wider than ½-inch at the joint of any inlet/outlet pipe or any evidence of soil particles entering the vault through the walls. Maintenance Necessary to Bring to Standard: Repair so no cracks more than 1/4 inch wide at any pipe joint.
L-6 Baffles—Damaged/Defective:Baffles corroding, cracking, warping and/or showing signs of failure. Maintenance Necessary to Bring to Standard: Repair or replace baffles to specifications.
L-7 Inlet/outlet Pipes—Damaged Pipes: Piping damaged or broken and in need of repair. Pipe or T-section does not retain floatables. Maintenance Necessary to Bring to Standard: Repair and/or replace pipe.
L-8 Inlet/outlet Pipes—Trash/Debris, Floating Oil Accumulations: Trash, debris or floating oils have accumulated in inlet/outlet pipe (includes floatables and non-floatables). Maintenance Necessary to Bring to Standard: Remove trash and debris. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
L-9 Access Cover—Damaged/Not Working: Access cover cannot be opened or removed, especially by one person. Maintenance Necessary to Bring to Standard: Loosen cover or remove objects hindering removal.
L-10 Access Cover—Ventilation Impaired: Ventilation grates blocked or not providing adequate ventilation. Maintenance Necessary to Bring to Standard: Restore full ventilation capacity.
L-11 Access Ladder—Damaged: Access ladder is corroded or deteriorated, not functioning properly, missing rungs, has cracks, and/or is misaligned. Maintenance Necessary to Bring to Standard: Repair or replace ladder to specifications so that it is safe to use.
L-12 Gravity Drain (If Applicable)—Proper Operation: Gravity Drain Valve operates and pipes are clear and capable of flow. Maintenance Necessary to Bring to Standard: Repair inoperable parts.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 19 M. Other—Specific to Bioswales (Including wet bioswales) (See Figure B-9 in Appendix) Definition: A bioswale is a grass lined swale whose purpose is to improve water quality by filtering surface water flow through the grass. A wet bioswale replaces grass with selected wetland vegetation. A flow spreader is a feature which helps to keep the flow spread evenly across the width of the bioswale.
Defect Number & Defect:
M-1 Swale Section—Sediment Accumulation on Grass: Sediment depth exceeds 2 inches. Maintenance Necessary to Bring to Standard: Remove sediment deposits on grass treatment area of the bioswale. When finished, swale should be level from side to side and drain freely toward outlet. There should be no areas of standing water once inflow has ceased. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
M-2 Swale Section—Standing Water: Water stands in the swale between storms and does not drain freely. Maintenance Necessary to Bring to Standard: Any of the following may apply: remove sediment or trash blockages, improve grade from head to foot of swale, remove clogged check dams, add underdrains or convert to a wet bioswale. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
M-3 Swale Section—Constant Baseflow: Small quantities of water continually flow through the swale, even when it has been dry for weeks, and an eroded, muddy channel has formed in the swale bottom. Maintenance Necessary to Bring to Standard: Repair swale bottom and divert baseflow around swale (or provide low flow drain if baselow <0.01 cfs) or convert to wet bioswale (with high flow bypass).
M-4 Swale Section—Poor Vegetation Cover: Grass is sparse or bare or eroded patches occur in more than 10% of the swale bottom. Maintenance Necessary to Bring to Standard: Determine why grass growth is poor and correct that condition. Replant with plugs of grass from the upper slope: plant in the swale bottom at 8-inch intervals, or re-seed into loosened, fertile soil. Do not use sod to re-establish grass.
M-5 Swale Section—Grass Length/Weeds: Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other vegetation (e.g. cattails) start to take over; or grass has died. Maintenance Necessary to Bring to Standard: Mow vegetation or eradicate nuisance vegetation such that flow is not impeded. Mow grass to a height of between 4 and 9 inches. If grass has died, replant/reestablish grass. Do not use sod to reestablish grass.
M-6 Swale Section—Excessive Shading: Grass growth is poor because sunlight does not reach swale. Maintenance Necessary to Bring to Standard: If possible, trim back over-hanging limbs, remove brushy vegetation on adjacent slopes. If grass still cannot survive due to lack of sunlight, replace with another type of water quality facility.
M-7 Swale Section—Trash and Debris Accumulation: Trash and debris accumulated in the bioswale. Maintenance Necessary to Bring to Standard: Remove trash and debris from bioswale. Reseed if necessary. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
Page 20 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities M-8 Swale Section—Erosion/Scouring: The bioswale has eroded or scoured the bottom due to flow channelization, or higher flows. Maintenance Necessary to Bring to Standard: Regrade and reseed bioswale to specification to eliminate channeled flow. Overseed when bare spots are evident. Install flow spreaders if condition is persistent.
M-9 Inlet/Outlet Pipe—Sediment and Debris: Inlet/outlet pipe clogged with sediment and/or debris. Maintenance Necessary to Bring to Standard: Remove sediment and/or debris so that there is no clogging or blockage in the inlet and outlet piping. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
M-10 Flow Spreader—Concentrated Flow: Flow spreader uneven or clogged so that flows are not uniformly distributed through entire swale width. Maintenance Necessary to Bring to Standard: Level the spreader and clean so that flows are spread evenly over entire swale width.
M-11 Swale Section (Wet Bioswale)—Sediment Accumulation: Sediment depth exceeds 2 inches in 10% of the swale treatment area. Maintenance Necessary to Bring to Standard: Remove sediment deposits in treatment area. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
M-12 Swale Section (Wet Bioswale)—Wetland Vegetation Health: Vegetation becomes sparse and does not provide adequate filtration, OR vegetation is crowded out by very dense clumps of cattail or other vegetation which do not allow water to flow through the clumps. Maintenance Necessary to Bring to Standard: Determine cause of lack of vigor of vegetation and correct. Replant as needed. For excessive cattail growth,remove with roots and compost offsite.
M-13 Swale Section (Wet Bioswale)—Trash and Debris Accumulation: Trash and debris accumulated in the wet swale. Maintenance Necessary to Bring to Standard: Remove trash and debris from wet swale. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
M-14 Swale Section (Wet Bioswale)—Erosion and Scouring: Swale has eroded or scoured due to flow channelization, or higher flows. Maintenance Necessary to Bring to Standard: Check bypass flow controls are operating correctly and swale design is adequate for design flows. Correct deficiencies. Replant eroded areas with fibrous- rooted plants (see the King County Surface Water Design Manual for a list of suitable plants).
M-15 Inlet/Outlet Pipe (Wet Bioswale)—Sediment and Debris: Inlet/outlet pipe clogged with sediment and/or debris. Maintenance Necessary to Bring to Standard: Remove sediment and/or debris so that there is no clogging or blockage in the inlet and outlet piping. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 21 N. Other—Specific to Wet Ponds (See Figure B-10 in Appendix) Definition: A wet pond is a stormwater pond that retains a permanent pool of water to dissipate energy and im- proves the settling of particulate pollutants from incoming stormwater to improve water quality.
Defect Number & Defect:
N-1 Pond Area—Water Level: First cell empty, doesn’t hold water. Maintenance Necessary to Bring to Standard: Line the first cell with an impermeable liner to maintain at least 4 feet of water. Although the second cell may drain, the first cell must remain full to control turbulence of the incoming flow and reduce sediment resuspension. If the second cell doesn’t hold water, line with low permeable liner or treatment liner If infiltration rate is greater than 9 inches/hour (2.4 inches/hour in a critical aquifer recharge area).
N-2 Pond Area—Defective Vegetation: Vegetation such as grass and weeds needs to be mowed when height exceeds 18 inches. Mowed vegetation should be removed from areas where it could enter the pond, either when the pond level rises, or by rainfall runoff. Trees, brush, and shrubs are impeding maintenance or flow. Maintenance Necessary to Bring to Standard: Mow vegetation to 4-5 inches in height. Remove trees, bushes and shrubs where they are interfering with pond maintenance activities; that is, at the inlet, outlet and near engineered structures. Some wetland species may require harvesting or special maintenance rather than mowing.
N-3 Pond Area—Algae Mats: When algae mats develop over more than 10% of the water surface, they should be removed. Also remove mats in the late summer before fall rains, especially in Sensitive Lake Protection Areas. Excessive algae mats interfere with dissolved oxygen content in the water and pose a threat to downstream lakes if excess nutrients are released. Maintenance Necessary to Bring to Standard: Algae mats that cover more than 10% of the surface of any cell should be removed. A rake or mechanical device should be used to remove the algae. Removed algae can be left to dry on the pond slope above the 100-year water surface.
N-4 Pond Area—Trash and Debris: Accumulation that exceeds 1 cubic foot per 1000 square foot of pond area. Maintenance Necessary to Bring to Standard: Trash and debris removed from pond. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
N-5 Pond Area—Sediment Accumulation: Sediment accumulations in pond bottom that exceeds the depth of sediment zone (typically 1’) plus 6 inches, usually in the first cell. Maintenance Necessary to Bring to Standard: Removal of sediment from pond bottom. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
N-6 Pond Area—Oil Sheen on Water: Prevalent and visible oil sheen. Maintenance Necessary to Bring to Standard: Remove oil from water by use of oil-absorbent pads or vactor truck. Locate source and correct. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
N-7 Pond Area—Erosion: Erosion of the pond’s side slopes and/or scouring of the pond bottom, that exceeds 6 inches, or where continued erosion is prevalent. Maintenance Necessary to Bring to Standard: Slopes should be stabilized by using appropriate erosion control measures, and repair methods.
Page 22 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities N-8 Pond Dike—Settlement: Any part of these components that has settled 4 inches or more lower than the design elevation, or inspector determines dike is unsound. Maintenance Necessary to Bring to Standard: Dike is repaired to specifications.
N-9 Internal Dike—Concentrated Flow: Dike dividing cells should be level. Maintenance Necessary to Bring to Standard: Build up low areas of dike or lower high areas so that the dike surface is level and water flows evenly over the entire length of the dike from the first cell to the second. Repair eroded areas and establish erosion control on areas that erode.
N-9 Inlet/Outlet Pipe—Trash and Debris: Inlet/outlet pipe clogged with sediment and/or debris material. Maintenance Necessary to Bring to Standard: Remove sediment and/or debris so that there is no clogging or blockage in the inlet and outlet piping. Ensure outlet pipe (or T-section if applicable) retains floatables. Refer to the disposal guidelines in Appendix A for instructions on disposal of trash, debris and sediment.
N-10 Inlet/Outlet Pipe—Floatables are Captured: Floatable material is retained by outlet pipe or T-section. Maintenance Necessary to Bring to Standard: Ensure outlet pipe (or T-section if applicable) retains floatables.
N-11 Overflow Spillway—Rock Missing: Rock is missing and soil is exposed at top of spillway or outside slope. Maintenance Necessary to Bring to Standard: Replace rocks to specifications.
N-12 Access Ramp—In Useable Condition: Access ramp is capable of supporting trucks and maintenance equipment. Maintenance Necessary to Bring to Standard: Repair ramp so it can support trucks and maintenance equipment.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 23 Page 24 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Appendix A: Disposal of Trash Debris and Sediment
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 25 Page 26 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Appendix A Disposal of Trash Debris and Sediment
Trash and Debris
Small amounts of trash and debris can be put into your solid waste container. Large amounts may require hiring a vendor to dispose of the material. If using a vendor, ensure that the vendor properly disposes of waste.
Sediment
1. Clean sediment may be used as landscape material or sent to yard waste recyclers.
2. Sediment that does not appear to be heavily contaminated with oil or grease can be double bagged and put into your solid waste container. Material that appears to be heavily contaminated must be disposed of by a qualified vendor.
If you have any questions, contact the Waste Characterization Program at 206-296-4633.
Additional information can be found at www.govlink.org/hazwaste/business/.
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 27 Page 28 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Appendix B: Facility Sketches
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 29 Page 30 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-1 Typical I Catch Basin
GRATE (May have solid lid)
FRAME
TOP SLAB OR RISER 6, 12 or 24 inches
36 inches
32 inches
42 inches typical BASE SECTION
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 31 Figure B-2 Typical Type II Catch Basin (Round Concrete Structure)
A A
Type II catch basin
frame with grate or solid cover PLAN VIEW shown with soil removed - not to scale
frame with grate or solid cover
handholds, steps or ladder
outlet inlet pipe pipe INVERT
SECTION A-A not to scale
Page 32 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-3 Typical Flow Restrictor (T-section) (Found in Type 2 Catch Basins)
frame with grate or solid cover marked “DRAIN” with locking bolts Type II catch basin
FROP-T
A A
secondary orifice elbow restrictor, removable watertight see detail coupling or flange
PLAN VIEW shown with soil removed - not to scale
frame with grate or solid cover plate welded to elbow marked “DRAIN” with locking bolts with orifice as specified SECONDARY ORIFICE ELBOW RESTRICTOR DETAIL vertical bar not to scale grate for secondary inlet (not always present) secondary orifice elbow restrictor, see detail pipe supports cleanout FROP-T gate rod or chain outlet pipe inlet
Pipe
cleanout gate
handholds, steps or ladder
orifice plate
SECTION A-A not to scale King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 33 Figure B-4 Typical Detention Pond flow access ramp into pond
pond inlet pipe flow energy dissipator
6" sediment storage
pond design water surface road alternate emergency outflow level structure for ponds not required bottom 12'/15' maintenance to provide a spillway
flow
control flow structure
emergency overflow spillway rip rap
Page 34 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-5 Typical Infiltration Pond
access road A
inflow pipe
slopes down settling pond if required
connecting spillway
slopes down
infiltration pond
outflow/ overflow structure emergency overflow spillway
A PLAN VIEW not to scale
rocks here?
H 3:1 slope inflow pipe
SECTION A-A not to scale
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 35 Figure B-6 Typical Detention Tank
A A flow
inlet pipe Control structure (FROP-T) Type 2 frame with catch basin solid locking cover Type 2 catch basin PLAN VIEW Shown with soil removed - not to scale
Type 2 frame with air vent Type 2 catch basin solid locking cover catch basin
sediment storage
inlet pipe
control structure (FROP-T) SECTION A-A not to scale
Page 36 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-7 Typical Detention Vault
frames with solid locking covers
outlet pipe A steps or ladder flow
flow sediment sump A SECTION LINE BENDS
PLAN VIEW Shown with soil removed - not to scale
frames with solid locking covers
flow secondary flow orifice restrictor (FROP-T) steps or ladder cleanout gate flow
sediment SECTION A-A sump not to scale
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 37 Figure B-8 Typical Wet Vault
access (cover/plate removed)
frame with locking outlet grate or solid pipe cover ventilation grate
high flow gravity outlet drain
HiFlo outlet water surface
baffle HiFlo outlet inlet pipe
sediment sump
CUTAWAY ISOMETRIC VIEW (with parts of top and sides removed)
not to scale
Page 38 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-9 Typical Bioswale
grass (or wetland plants if wet bioswale)
bottom width = 2-16'
BIOSWALE SECTION not to scale
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 39 Figure B-10 Typical Wetpond
access road to inlet structure
energy dissipator access ramp
FIRST WETPOOL CELL
berm top
SECOND WETPOOL CELL
emergency spillway manhole & outlet pipe
energy dissipator access road to outlet structure
PLAN VIEW not to scale
Page 40 King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Figure B-11 Typical Infiltration Tank
washed rock bedding
frames with outlet pipe solid locking Type 2 covers catch basin A A Inlet pipe (flow through)
outlet/overflow structure PLAN VIEW not to scale
air vent pipe welded to tank (required if no access riser on tank)
type 2 catch basin or settling vault if required 6” dead storage
1” holes as overflow structure washed required catch basin rock bedding
SECTION A-A not to scale
King County Drainage Maintenance Standards for Commercial and Multifamily Drainage Facilities Page 41 PHIC COMMUNICATIO GRA NS UNION LABEL IN TERGCINAT LUUNION IONA 1202M
Produced by: WLRD Visual Communications and Web Unit File Name: 0706_ComDrainBook.indd lpre WLRD Unit Archives
Alternate formats available 206-296-6519 TTY Relay: 711 11. APPENDICES
Appendix A: Supporting Calculations
Appendix B: Downstream System Map
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 26 Duvall, WA
APPENDIX A: Supporting Calculations
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 27 Duvall, WA
WWHM2012 PROJECT REPORT ______
Project Name: Duvall Peaks Site Name: Sherlock Self-Storage Site Address: 14441 Main Street City : Duvall Report Date: 5/31/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 ______
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ______
High Flow Threshold for POC 1: 50 year ______
PREDEVELOPED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Lawn, Flat .206
Pervious Total 0.206
Impervious Land Use acre ROADS FLAT 0.767
Impervious Total 0.767
Basin Total 0.973
______
Element Flows To: Surface Interflow Groundwater
______
MITIGATED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Lawn, Flat .273
Pervious Total 0.273
Impervious Land Use acre ROADS FLAT 0.7
Impervious Total 0.7
Basin Total 0.973
______
Element Flows To: Surface Interflow Groundwater
______
______
ANALYSIS RESULTS
Stream Protection Duration
______
Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.206 Total Impervious Area:0.767 ______
Mitigated Landuse Totals for POC #1 Total Pervious Area:0.273 Total Impervious Area:0.7 ______
Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.305584 5 year 0.390731 10 year 0.449129 25 year 0.525441 50 year 0.584228 100 year 0.644748
Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.284348 5 year 0.365748 10 year 0.421833 25 year 0.495385 50 year 0.552226 100 year 0.610888
WWHM2012 PROJECT REPORT ______
Project Name: Duvall Sherlock Site Name: Sherlock Self-Storage Site Address: 14441 Main Street City : Duvall Report Date: 5/31/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 ______
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ______
High Flow Threshold for POC 1: 50 year ______
PREDEVELOPED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Forest, Flat .147
Pervious Total 0.147
Impervious Land Use acre
Impervious Total 0
Basin Total 0.147
______
Element Flows To: Surface Interflow Groundwater
______
MITIGATED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Lawn, Flat .02
Pervious Total 0.02
Impervious Land Use acre ROADS FLAT 0.127
Impervious Total 0.127
Basin Total 0.147
______
Element Flows To: Surface Interflow Groundwater Surface retention 1 Surface retention 1 ______
Name : Bioretention 1 Bottom Length: 20.00 ft. Bottom Width: 3.00 ft. Material thickness of first layer: 1.5 Material type for first layer: SMMWW 12 in/hr Material thickness of second layer: 0.5 Material type for second layer: GRAVEL Material thickness of third layer: 0 Material type for third layer: GRAVEL Underdrain used Underdrain Diameter (feet): 0.5 Orifice Diameter (in.): 6 Offset (in.): 4 Flow Through Underdrain (ac-ft.): 21.522 Total Outflow (ac-ft.): 22.42 Percent Through Underdrain: 96 Discharge Structure Riser Height: 1 ft. Riser Diameter: 6 in.
Element Flows To: Outlet 1 Outlet 2
______
Bioretention 1 Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs) 0.0000 0.0110 0.0000 0.0000 0.0000 0.0385 0.0108 0.0000 0.0000 0.0000 0.0769 0.0105 0.0000 0.0000 0.0000 0.1154 0.0103 0.0000 0.0000 0.0000 0.1538 0.0100 0.0001 0.0000 0.0000 0.1923 0.0098 0.0001 0.0000 0.0000 0.2308 0.0096 0.0001 0.0000 0.0000 0.2692 0.0093 0.0001 0.0000 0.0000 0.3077 0.0091 0.0001 0.0000 0.0000 0.3462 0.0089 0.0002 0.0000 0.0000 0.3846 0.0087 0.0002 0.0000 0.0000 0.4231 0.0084 0.0002 0.0000 0.0000 0.4615 0.0082 0.0002 0.0000 0.0000 0.5000 0.0080 0.0003 0.0000 0.0000 0.5385 0.0078 0.0003 0.0000 0.0000 0.5769 0.0076 0.0003 0.0000 0.0000 0.6154 0.0073 0.0003 0.0000 0.0000 0.6538 0.0071 0.0004 0.0000 0.0000 0.6923 0.0069 0.0004 0.0000 0.0000 0.7308 0.0067 0.0004 0.0000 0.0000 0.7692 0.0065 0.0005 0.0002 0.0000 0.8077 0.0063 0.0005 0.0002 0.0000 0.8462 0.0061 0.0006 0.0002 0.0000 0.8846 0.0059 0.0006 0.0003 0.0000 0.9231 0.0057 0.0006 0.0003 0.0000 0.9615 0.0056 0.0007 0.0004 0.0000 1.0000 0.0054 0.0007 0.0005 0.0000 1.0385 0.0052 0.0008 0.0005 0.0000 1.0769 0.0050 0.0008 0.0006 0.0000 1.1154 0.0048 0.0009 0.0007 0.0000 1.1538 0.0046 0.0009 0.0008 0.0000 1.1923 0.0045 0.0010 0.0009 0.0000 1.2308 0.0043 0.0011 0.0010 0.0000 1.2692 0.0041 0.0011 0.0011 0.0000 1.3077 0.0040 0.0012 0.0012 0.0000 1.3462 0.0038 0.0012 0.0014 0.0000 1.3846 0.0036 0.0013 0.0015 0.0000 1.4231 0.0035 0.0014 0.0017 0.0000 1.4615 0.0033 0.0014 0.0018 0.0000 1.5000 0.0032 0.0015 0.0020 0.0000 1.5385 0.0030 0.0016 0.0022 0.0000 1.5769 0.0029 0.0016 0.0024 0.0000 1.6154 0.0027 0.0017 0.0025 0.0000 1.6538 0.0026 0.0018 0.0028 0.0000 1.6923 0.0024 0.0018 0.0030 0.0000 1.7308 0.0023 0.0019 0.0032 0.0000 1.7692 0.0022 0.0020 0.0034 0.0000 1.8077 0.0020 0.0021 0.0037 0.0000 1.8462 0.0019 0.0021 0.0039 0.0000 1.8846 0.0018 0.0022 0.0042 0.0000 1.9231 0.0016 0.0023 0.0042 0.0000 1.9615 0.0015 0.0024 0.0042 0.0000 2.0000 0.0014 0.0025 0.0042 0.0000
Surface retention 1 Hydraulic Table Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) To Amended(cfs) Wetted Surface 2.0000 0.0110 0.0025 0.0000 0.0171 0.0000 2.0385 0.0113 0.0029 0.0000 0.0171 0.0000 2.0769 0.0115 0.0033 0.0000 0.0175 0.0000 2.1154 0.0118 0.0038 0.0000 0.0179 0.0000 2.1538 0.0120 0.0042 0.0000 0.0184 0.0000 2.1923 0.0123 0.0047 0.0000 0.0188 0.0000 2.2308 0.0126 0.0052 0.0000 0.0192 0.0000 2.2692 0.0128 0.0057 0.0000 0.0197 0.0000 2.3077 0.0131 0.0062 0.0000 0.0201 0.0000 2.3462 0.0134 0.0067 0.0000 0.0205 0.0000 2.3846 0.0136 0.0072 0.0000 0.0209 0.0000 2.4231 0.0139 0.0077 0.0000 0.0214 0.0000 2.4615 0.0142 0.0083 0.0000 0.0218 0.0000 2.5000 0.0145 0.0088 0.0000 0.0222 0.0000 2.5385 0.0147 0.0094 0.0000 0.0226 0.0000 2.5769 0.0150 0.0100 0.0000 0.0231 0.0000 2.6154 0.0153 0.0105 0.0000 0.0235 0.0000 2.6538 0.0156 0.0111 0.0000 0.0239 0.0000 2.6923 0.0159 0.0117 0.0000 0.0244 0.0000 2.7308 0.0162 0.0124 0.0000 0.0248 0.0000 2.7692 0.0165 0.0130 0.0000 0.0252 0.0000 2.8077 0.0168 0.0136 0.0000 0.0256 0.0000 2.8462 0.0171 0.0143 0.0000 0.0261 0.0000 2.8846 0.0174 0.0149 0.0000 0.0265 0.0000 2.9231 0.0177 0.0156 0.0000 0.0269 0.0000 2.9615 0.0180 0.0163 0.0000 0.0274 0.0000 3.0000 0.0183 0.0170 0.0000 0.0278 0.0000 3.0385 0.0186 0.0177 0.0399 0.0282 0.0000 3.0769 0.0189 0.0184 0.1109 0.0286 0.0000 3.1154 0.0193 0.0192 0.1943 0.0291 0.0000 3.1538 0.0196 0.0199 0.2743 0.0295 0.0000 3.1923 0.0199 0.0207 0.3368 0.0299 0.0000 3.2308 0.0202 0.0215 0.3761 0.0303 0.0000 3.2692 0.0206 0.0222 0.4086 0.0308 0.0000 3.3077 0.0209 0.0230 0.4368 0.0312 0.0000 3.3462 0.0212 0.0238 0.4633 0.0316 0.0000 3.3846 0.0216 0.0247 0.4883 0.0321 0.0000 3.4231 0.0219 0.0255 0.5122 0.0325 0.0000 3.4615 0.0222 0.0264 0.5349 0.0329 0.0000 3.5000 0.0226 0.0272 0.5568 0.0333 0.0000 3.5000 0.0226 0.0272 0.5778 0.0333 0.0000 ______
Name : Surface retention 1
Element Flows To: Outlet 1 Outlet 2 Bioretention 1 ______
______
ANALYSIS RESULTS
Stream Protection Duration
______
Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.147 Total Impervious Area:0 ______
Mitigated Landuse Totals for POC #1 Total Pervious Area:0.02 Total Impervious Area:0.127 ______
Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.003875 5 year 0.006235 10 year 0.007546 25 year 0.008898 50 year 0.009708 100 year 0.010378
Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.015974 5 year 0.0342 10 year 0.050047 25 year 0.074153 50 year 0.094934 100 year 0.118012 ______
Stream Protection Duration Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.004 0.004 1950 0.007 0.024 1951 0.009 0.037 1952 0.003 0.004 1953 0.002 0.004 1954 0.003 0.014 1955 0.006 0.032 1956 0.005 0.030 1957 0.004 0.020 1958 0.004 0.009 1959 0.003 0.017 1960 0.006 0.030 1961 0.003 0.018 1962 0.002 0.004 1963 0.003 0.021 1964 0.003 0.013 1965 0.002 0.016 1966 0.003 0.004 1967 0.005 0.035 1968 0.003 0.004 1969 0.003 0.009 1970 0.003 0.013 1971 0.002 0.027 1972 0.007 0.036 1973 0.003 0.004 1974 0.003 0.011 1975 0.005 0.036 1976 0.003 0.015 1977 0.000 0.004 1978 0.003 0.017 1979 0.002 0.004 1980 0.004 0.038 1981 0.002 0.004 1982 0.004 0.053 1983 0.004 0.023 1984 0.003 0.004 1985 0.001 0.015 1986 0.007 0.036 1987 0.006 0.037 1988 0.002 0.004 1989 0.001 0.004 1990 0.009 0.062 1991 0.008 0.057 1992 0.003 0.021 1993 0.003 0.007 1994 0.001 0.004 1995 0.004 0.025 1996 0.009 0.039 1997 0.008 0.038 1998 0.002 0.008 1999 0.005 0.032 2000 0.003 0.016 2001 0.000 0.004 2002 0.004 0.040 2003 0.003 0.004 2004 0.007 0.071 2005 0.004 0.025 2006 0.005 0.023 2007 0.012 0.054 2008 0.011 0.059 2009 0.006 0.038 ______
Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0119 0.0709 2 0.0105 0.0620 3 0.0095 0.0590 4 0.0092 0.0566 5 0.0087 0.0541 6 0.0084 0.0527 7 0.0080 0.0404 8 0.0073 0.0391 9 0.0071 0.0378 10 0.0068 0.0377 11 0.0067 0.0376 12 0.0060 0.0375 13 0.0060 0.0370 14 0.0057 0.0360 15 0.0057 0.0360 16 0.0055 0.0360 17 0.0050 0.0348 18 0.0050 0.0319 19 0.0047 0.0318 20 0.0046 0.0303 21 0.0045 0.0302 22 0.0045 0.0273 23 0.0042 0.0248 24 0.0042 0.0245 25 0.0041 0.0236 26 0.0040 0.0229 27 0.0039 0.0227 28 0.0037 0.0205 29 0.0036 0.0205 30 0.0034 0.0204 31 0.0033 0.0176 32 0.0033 0.0171 33 0.0033 0.0170 34 0.0033 0.0163 35 0.0032 0.0161 36 0.0032 0.0152 37 0.0032 0.0151 38 0.0031 0.0141 39 0.0031 0.0129 40 0.0030 0.0129 41 0.0028 0.0106 42 0.0027 0.0094 43 0.0026 0.0093 44 0.0026 0.0078 45 0.0026 0.0069 46 0.0025 0.0042 47 0.0025 0.0042 48 0.0025 0.0042 49 0.0025 0.0042 50 0.0024 0.0042 51 0.0024 0.0042 52 0.0022 0.0042 53 0.0022 0.0042 54 0.0020 0.0042 55 0.0016 0.0042 56 0.0015 0.0042 57 0.0014 0.0042 58 0.0014 0.0042 59 0.0008 0.0042 60 0.0004 0.0042 61 0.0003 0.0042 ______
Stream Protection Duration POC #1
Facility FAILED duration standard for 1+ flows.
Flow(cfs) Predev Mit Percentage Pass/Fail 0.0019 4412 59461 1347 Fail 0.0020 4061 58284 1435 Fail 0.0021 3757 57055 1518 Fail 0.0022 3480 55985 1608 Fail 0.0023 3226 54969 1703 Fail 0.0023 2991 54007 1805 Fail 0.0024 2762 53007 1919 Fail 0.0025 2574 51985 2019 Fail 0.0026 2406 51082 2123 Fail 0.0026 2251 50194 2229 Fail
WWHM2012 PROJECT REPORT ______
Project Name: Duvall Peaks Site Name: Sherlock Self-Storage Site Address: 14441 Main Street City : Duvall Report Date: 5/31/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 ______
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ______
High Flow Threshold for POC 1: 50 year ______
PREDEVELOPED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Lawn, Flat .206
Pervious Total 0.206
Impervious Land Use acre ROADS FLAT 0.767
Impervious Total 0.767
Basin Total 0.973
______
Element Flows To: Surface Interflow Groundwater
______
MITIGATED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Lawn, Flat .273
Pervious Total 0.273
Impervious Land Use acre ROADS FLAT 0.7
Impervious Total 0.7
Basin Total 0.973
______
Element Flows To: Surface Interflow Groundwater
______
______
ANALYSIS RESULTS
Stream Protection Duration
______
Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.206 Total Impervious Area:0.767 ______
Mitigated Landuse Totals for POC #1 Total Pervious Area:0.273 Total Impervious Area:0.7 ______
Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.305584 5 year 0.390731 10 year 0.449129 25 year 0.525441 50 year 0.584228 100 year 0.644748
Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.284348 5 year 0.365748 10 year 0.421833 25 year 0.495385 50 year 0.552226 100 year 0.610888
WWHM2012 PROJECT REPORT ______
Project Name: Duvall Sherlock Site Name: Sherlock Self-Storage Site Address: 14441 Main Street City : Duvall Report Date: 5/31/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 ______
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ______
High Flow Threshold for POC 1: 50 year ______
PREDEVELOPED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Forest, Flat .568
Pervious Total 0.568
Impervious Land Use acre
Impervious Total 0
Basin Total 0.568
______
Element Flows To: Surface Interflow Groundwater
______
MITIGATED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre ROOF TOPS FLAT 0.568
Impervious Total 0.568
Basin Total 0.568
______
Element Flows To: Surface Interflow Groundwater
______
______
ANALYSIS RESULTS
Stream Protection Duration
______
Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.568 Total Impervious Area:0 ______
Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.568 ______
Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.0167 5 year 0.026227 10 year 0.031627 25 year 0.037347 50 year 0.040887 100 year 0.043898
Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.216558 5 year 0.273538 10 year 0.312252 25 year 0.36247 50 year 0.400905 100 year 0.440274 ______Steel Tank Open-Top Weir
Overview: 18,100 gallon open top weir tanks from Rain for Rent come with over and under weirs for separation of oils or particulates. This tank has a standard “V” shaped floor for ease of draining all stored liquids completely through a 4” butterfly valve with Buna seals standard.
Features: Store and separate liquids with confidence with Rain for Rent’s 18,100 gallon open top weir tank. Permanently attached axels for maximum maneuverability allow this 18,100 gallon tank to be moved with ease on the jobsite and a safety staircase ensures proper protection for workers on site.
Specs: Accessories: • Spillguard Manways Three 22” hatches • Suction and discharge piping Material Steel • Level gauges Capacity 18,100 gallons Dry weight 27,000 lbs. Footprint: 516” x 96” x 126”
PUMPS • TANKS • FILTRATION • PIPE • SPILLGUARDS 800-742-7246 Rain for Rent is a registered trademark of Western Oilfields Supply Company. Features and specifications are subject to change without notice. rainforrent.com
WWHM2012 PROJECT REPORT ______
Project Name: Duvall Sherlock Site Name: Sherlock Self-Storage Site Address: 14441 Main Street City : Duvall Report Date: 5/31/2017 Gage : Seatac Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version Date: 2016/02/25 Version : 4.2.12 ______
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year ______
High Flow Threshold for POC 1: 50 year ______
PREDEVELOPED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre C, Forest, Flat .406
Pervious Total 0.406
Impervious Land Use acre
Impervious Total 0
Basin Total 0.406
______
Element Flows To: Surface Interflow Groundwater
______
MITIGATED LAND USE
Name : Basin 1 Bypass: No
GroundWater: No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use acre ROOF TOPS FLAT 0.406
Impervious Total 0.406
Basin Total 0.406
______
Element Flows To: Surface Interflow Groundwater
______
______
ANALYSIS RESULTS
Stream Protection Duration
______
Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.406 Total Impervious Area:0 ______
Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.406 ______
Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.011937 5 year 0.018747 10 year 0.022607 25 year 0.026696 50 year 0.029226 100 year 0.031378
Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.154793 5 year 0.195522 10 year 0.223194 25 year 0.259089 50 year 0.286562 100 year 0.314703 ______
Key divider into slope to prevent flow around sides
Emergency The pond length shall overflow spillway be 3 to 6 times the maximum pond width
Pond length Inflow Discharge to stabilized Riser pipe conveyance, outlet, or level spreader
Silt fence or equivalent divider
Note: Pond may be formed by berm or by partial or complete excavation
NOT TO SCALE
Figure II-4.2.18 Sediment Pond Plan View D E P A R T M E N T O F Revised November 2015
ECOLOGY Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer. Crest of Riser pipe emergency spillway 6' Min. width. (principal spillway) open at top with 1' Min. trash rack
3H : 1V Max.Dewatering device 1' 2H : 1V Max. (see riser detail)
Discharge to 3H : 1V Max. stabilized conveyance outlet 1.5' or level spreader
Embankment Wire-backed silt fence compacted 95% Dewatering staked haybales pervious materials orifice wrapped with filter fabric, such as gravel or clean or equivalent divider Concrete base sand shall not be used (see riser detail)
NOT TO SCALE
Figure II-4.2.19 Sediment Pond Cross Section D E P A R T M E N T O F Revised November 2015
ECOLOGY Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, State of Washington limitation of liability, and disclaimer.
APPENDIX B: Downstream System Map
CECIL & ASSOCIATES, LLC Sherlock Duvall Self-Storage 28 Duvall, WA