Loading...
SIT2022-00016 1 STOPMWATER 1 0 o) z RE PORT 1 Si-V 2D2z-cco 1 co 1 Z Q 9TG Cacr&c1 n BMW of Tigard >- g 1 F- 10031 SW Cascade Avenue 7' Tigard, OR 97223 1 Ilimima > RECEIVED June 14,2022 1 o JUL 18 2022 �� U CITY OF TIGARD I BUILDING DIVISION Vl Prepared For: III pU Holman Automotive Group 911 NE 2nd Avenue 1 Fort Lauderdale, FL 33304 VI) (../.) III I0�c��c'� F G I N EF `S,D� I I I - 95gfFPF \c I < pig p OREGON o r�� U y� q oti ' � p Jun\(6 ?�f�t14 A` y . -,, dA M ES ' ." 0 0 1 Z/ EXPIRES: 12/31/22 rY p II ( I I Prepared By: 31 Consulting,Inc. I Z111.11101) Z 9600 SW Nimbus Avenue,Suite 100 Beaverton,Oregon 97008 L1J Project No:21684 1 P1P 1 1144) L.) 1 ' LIST OF FIGURES Figure 1 -Vicinity Map 3 ' Figure 2-Site Location 4 LIST OF TABLES Table 1 -Onsite Soil Types 4 ' Table 2- Existing Basin Areas 5 Table 3- Post-Developed Basin Areas 6 Table 4- Design Storms 6 Table 5- Peak Runoff Rates 7 Table 6- Proprietary Treatment Devices 8 Table 7-Summary of Approaches 8 Table 8-Water Quality Volumes and Flow Rates 9 Table 9- Downstream Analysis Results 10 Table 10- Flow Control Criteria 11 Table 11 -Target Release Rates 11 Table 12- Flow Control Manhole 12 Table 13- Post-Developed Release Rates 12 1 1 I BMW of Tigard Page 1 of 13 Stormwater Report DESIGNER ' S CERTIFICATION & STATEMENT ' I hereby certify that this Stormwater Management Report for the BMW of Tigard development has been prepared by me or under my supervision and meets minimum standards of the City of Tigard and Clean Water Services and normal standards of engineering practice. I hereby acknowledge and agree that the jurisdiction 111 does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities designed by me. 1 1 r I 1 I I 1 I I I 1 3J' r -� BMW of Tigard Page 2 of 13 Stormwater Report EXECUTIVE SUMMARY 111 The proposed BMW of Tigard development is located at 10031 SW Cascade Avenue (tax lot 15127DD01200) in the City of Tigard, Oregon. The project site is within the jurisdictions of City of Tigard and Clean Water Services (CWS). The design and analysis of all required stormwater management approaches will be in accordance with CWS' Design & Construction Standards for Sanitary Sewer& Surface Water Management(CWS D&C; 2019). The property is currently developed with a lot size of 3.65 ac but will be reduced to 3.52 ac in post-developed conditions.This project proposes improvements on the private lot and in the public right-of-way(ROW)along Cascade Avenue. For this report,the area of analysis(project site) is 4.06 ac,which consists of onsite and ROW areas. Due to the amount of new and modified impervious area generated by the project, CWS requires the implementation of stormwater management approaches,which will be addressed as follows: • Water Quality Approaches , o Three(3) Proprietary Treatment Devices (PTD), 2 StormFilter Manholes and 1 StormFilter Catch Basin,will capture and treat runoff from post-developed impervious areas. o Flow-Through Planters will capture and treat runoff from post-developed impervious areas in the ROW.The design and analysis of the Planters is expounded upon in"Stormwater Report for Public Facilities Improvement for BMW of Tigard". • Hydromodification Approach o Peak Flow Matching will be accomplished via a Contech CMP Detention Facility and flow control manhole.The facility will over-detain for unmitigated impervious areas along Cascade Avenue to the maximum extent practicable. • Quantity Control for Conveyance Capacity o A Downstream Analysis was performed and demonstrates that this project does not result in downstream conveyance deficiencies;therefore, no additional water quantity management criteria are required. There are no upstream drainage areas for the private property. There are upstream drainage areas for the 111 storm drain systems in the public ROW that are discussed in "Stormwater Report for Public Facilities Improvement for BMW of Tigard". , An Operations & Maintenance Plan has been prepared and attached. Please refer to this project's Construction Plans for locations and construction details of all stormwater management facilities. The purpose of this report is to accomplish the following. , • Describe pre-and post-developed basins and drainage; • Describe the design and analysis of the proposed stormwater management facilities; and, • Demonstrate compliance with City of Tigard and Clean Water Services standards pertaining to stormwater management. 3J� � r ~~ BMW orTigard Page nov1n etormwate,nepox __~ ' �___-- U� �� P 0U E o� l� U� �� S o� P U �� 77 U �� A� The BMW of Tigard development proposes site and utility improvements at 10031 SVV Cascade Avenue (tax lot 1S1270001200) in the City of Tigard, Oregon. The project site is within the jurisdictions of City of Tigard and Clean Water Services (CVVS). The property is currently developed with a lot size of 3.65 ac but will be reduced to 3.52 ac in post-developed conditions.This project proposes improvements on the private lot and in the public right-of-way(ROW)along Cascade Avenue. For this report, hydrologic analyses are based on a cumulative area of 4.06 ac,which includes � areas on the property and in the public right-of-way. project also consists of proposed storm drain M� The pr �^ � system consisting of stormwater management approaches. Runoff from the project site eventually discharges � to Ash Creek. BANKS � "vRE,r GRESHAN BEAVERTON ILWAUKI PY VALLEY PROJECT SITE TIGARn\ LAKEJP�WEGO 7iP SHERWOOD OREGON CITY m� Figure 1 'Vicimity Map BMW of Tigard Page 4 of 13 Stormwater Report i , '« a , : '' ate ` ���'� �aSY 'hest Cascade Aver• '` t Washington I pss\ss',,:::::\oss ` . Square PROJECTVA 1 ' SITE 0 ,7 P : g ca 20,\ �� t t t ,, so,,,, 1. 1 • 4 t i da P I o . WoshingtoR 1 Satare Figure 2-Site Location I EXISTING CONDITIONS Site I In existing conditions, the project site is occupied by a building, parking lots, driveways, and hardscaping. Onsite pervious areas consist of landscaping. All onsite impervious area will be demolished. Cascade Avenue along the northern and eastern edges of the property will be disturbed to implement frontage improvements in the public right-of-way(ROW). Flood Map I The site is located within Zone X (unshaded) per flood insurance rate map (FIRM) community-panel number 41067C0533E (See Technical Appendix: Exhibits - National Flood Hazard Layer FIRMette). FEMA's definition of I Zone X(un-shaded) is an area of minimal flood hazard. Site Geology & Infiltration I The soil types as classified by the United States Department of Agriculture Soil Survey of Washington County are identified in Table 1 (See Technical Appendix: Exhibits - Hydrologic Soil Group). Soil Type Hydrologic Soil I Group (HSG) Aloha Silt Loam C/D I Huberly Silt Loam C/D Cove Silty Clay Loam D Table 1 - Onsite Soil Types Jr� 1 I BMW of Tigard Page 5 of 13 Stormwater Report For conservativeness, the entire site will be modeled as soil type D. Since the project site coincides with D soils, infiltration is not recommended. ' Drainage The existing site drains to local low points and enters the onsite storm drain system via catch basins. The ' system drains westerly and outlets to the existing drainage ditch that runs parallel to the train tracks, which conveys flow to the south through a system of drainage ditches ' The portion of Cascade Avenue to be disturbed along the northern edge of the project site drains to a curb inlet near the intersection with Scholls Ferry Road. Runoff is conveyed westerly and discharges to the same ditch system described above. The portion of Cascade Avenue to be disturbed along the eastern edge of the project site drains to a curb inlet near the southeast corner of the project site. Runoff is conveyed southerly and discharges to a ditch along the eastern edge of Cascade Avenue. Flows continue south via open channel conveyances, intermittently ' discharges to a vegetated channel between the 10065 & 10075 SW Cascade Avenue properties,which carries flow east and discharges to the ditch system along the tracks as mentioned previously. All runoff from this project ultimately discharges to Ash Creek, relatively close to its confluence with Fanno Creek, approximately 0.60 miles south of the project site. See 'Technical Appendix: Exhibits - Existing Conditions"for basin locations. Basin Areas Table 2 shows the existing impervious and pervious areas for each basin (See Technical Appendix: Exhibits - ' Existing Conditions). Existing Conditions sf ac ' Impervious Area Modified = 136,111 sf 140,433 3.22 Existing to Remain =4,322 sf Pervious Area 36,565 0.84 Total Area 176,998 4.06 ' Table 2- Existing Basin Areas POST - DEVELOPED CONDITIONS Site & Drainage In post-developed conditions, the proposed onsite improvements include a new building, parking lots, ' driveways, and hardscaping. The project will propose a new storm drain system, consisting of stormwater management facilities, which will maintain discharge to the drainage ditch to the west running parallel to the train tracks. Stormwater management facilities are proposed for water quality treatment and detention. The design and analysis of the facilities will be discussed in later sections. For conveyance analyses and stormwater management facility sizing,the Onsite basin was divided into seven (7) subbasins (See Technical Appendix: Exhibits - Post-Developed Conditions). 3J' BMW of Tigard Page 6 of 13 Stormwater Report Basin Areas Table 3 summarizes the post-developed basin areas for the project site (See Technical Appendix: Exhibits - Post-Developed Conditions). , Post-Developed Conditions sf ac Impervious Area , New& Replaced = 148,678 sf 153,000 3.51 Existing to Remain =4,322 sf Pervious Area 23,998 0.55 Total Area 176,998 4.06 Table 3- Post-Developed Basin Areas When comparing Tables 2 & 3, it is determined that the project results in 12,567 sf of new impervious area (i.e. 153,000 - 140,433). , HYDROLOGIC ANALYSIS Design Guidelines ' The site is located within the jurisdictions of the City of Tigard and Clean Water Services. The guidelines used for the design of this project reflect current Clean Water Services Design&Construction Standards(CWS D&C), issued in December 2019. Hydrograph Method Naturally occurring rainstorms dissipate over long periods of time. An effective way of estimating storm rainfall is by using the hydrograph method. In accordance with the CWS D&C, the Santa Barbara Urban Hydrograph (SBUH) method was used to develop runoff rates.The computer software XPSTORM was used in modeling the hydrology during the predeveloped and post-developed storm events to determine the increase in runoff due to the development. Design Storms ' The rainfall distribution to be used for this area is the design storm of 24-hour duration based on the standard Type 1A rainfall distribution. Table 4 shows total precipitation depths for the storm events used in analysis, which were used as multipliers for the Type 1A 24-hour rainfall distribution. Recurrence Precipitation Interval (yr) Depth (in) 2 2.50 5 3.10 10 3.45 25 3.90 100 4.50 1 Table 4- Design Storms Curve Number The major factors for determining the runoff curve numbers (CN) are hydrologic soil group, cover type, treatment, hydrologic condition, and antecedent runoff condition. The curve number represents runoff potential from the ground. Table 2-2a from the TR-55 Urban Hydrology for Small Watersheds manual was used 3J' I BMW of Tigard Page 7 of 13 Stormwater Report i to determine the appropriate curve numbers (See Technical Appendix: Exhibits - Curve Numbers). As indicated previously, the site is underlain by soil type D. IIn predeveloped conditions, pervious areas except in modified impervious areas were modeled with a CN of 79, which is associated with a cover type of woods-grass combination in good condition. Per the CWS D&C, I modified impervious areas may be modeled with a CN of 75. Existing impervious areas to remain will be modeled with a CN of 98. In post-developed conditions, pervious areas were modeled with a CN of 80, which is associated with a cover I type of lawn in good condition. Impervious areas were modeled with a CN of 98. Time of Concentration 1 In accordance with the CWS D&C, the predeveloped time of concentration (Tc) for the onsite basin was evaluated per the USDA TR-55 manual. The Tc for the project site was evaluated to be 13 minutes (See Technical Appendix - Calculations). Due to their small drainage areas, the predeveloped frontage basins are Iassumed to have Tc's of 5 minutes.The post-developed Tc for all subbasins was assumed to be 5 minutes. Basin Runoff I Table 5 summarizes the pre- and post-developed runoff rates from the project site (See Technical Appendix: Hydrographs). I Recurrence Peak Runoff Rates (cfs) Interval (yr) Predev. Post-Dev. Increase 2 0.429 2.117 +1.688 I5 0.791 2.693 +1.902 10 1.027 3.031 +2.004 I 25 1.351 3.467 +2.116 Table 5- Peak Runoff Rates I WATER QUALITY TREATMENT LIDA Feasibility I Per Section 4.05 of the CWS D&C, new development shall reduce its hydrologic impacts through Low Impact Development Approaches unless the criteria in 4.05.2 apply. Site and drainage constraints make the implementation of LIDA approaches onsite infeasible; therefore, Proprietary Treatment Devices (PTD)will be I proposed. Flow-Through Planters are proposed to treat runoff along Cascade Avenue, in the ROW. The design and analysis of the Planters are discussed in "Stormwater Report for Public Facilities Improvements for BMW of ITigard". Design Criteria IRequired Treatment Area Per the CWS D&C, the impervious area requiring water quality treatment is evaluated as the new impervious I area plus three times the modified impervious area. The following calculation were performed to determine the required treatment area. 1 Treatment Area = New Impervious Area + 3 x Modified Imp.Area I = 12,567 sf+ 3 X 136,111 sf=420,900 sf 3J•- BMW of Tigard Page 8 of 13 , Stormwater Report II I The calculated treatment area exceeds the post-developed impervious area (i.e., 153,000 sf); therefore, the 1 I required treatment area is 153,000 sf. Water Quality Flow I Per the CWS D&C, water quality treatment facilities are required to be designed to treat the rainfall of 0.36" over a 4-hour period with a return period of 96-hours. The following equation is used in determining the I design flow rate for water quality treatment facilities. Water Quality Volume (WQV) = Treatment Area (sf)X 0.36 (in) 111 12 (in/ft) Water Quality Flow(WQF) = WQV 14,400 (sec) I Water Quality Approaches Proprietary Treatment Devices I A Contech StormFilter Catch Basin (CB) and two (2) Manholes (MH) are proposed to treat runoff from Subbasins 1 through 4 (see Technical Appendix: Exhibits - Post-Developed Conditions). Each facility will be I equipped with StormFilter EMC cartridges and are designed to treat runoff from contributing impervious area (CIA). Table 6 indicates the required Proprietary Treatment Device to treat runoff from each subbasin. Post-Dev. CIA WQV WQF Proprietary Treatment Treatment I Subbasin (sf) (cf) (cfs) Device Capacity(cfs) 1 + 2 62,449 1,873 0.130 72"StormFilter MH w/five 0.140 (5) 18" EMC cartridges I 3 13,648 412 0.029 Storm Filter CB w/ one (1) 0.042 27" EMC cartridge I 4 56,970 1,709 0.119 72"StormFilter MH w/five 0.140 (5) 18" EMC cartridges Subtotal 133,167 I Table 6- Proprietary Treatment Devices Flow-Through Planters I Flow-Through Planters were sized to treat runoff along Cascade Avenue in Subbasins 6 & 7. The design and analysis of the Planters are discussed in "Stormwater Report for Public Facilities Improvements for BMW of Tigard". I Summary of Approaches Table 7 summarizes the provided treatment by each proposed approach. I Post-Dev. Water Quality Approach Impervious Subbasin Area (sf) I 1 through 4 Proprietary Treatment Devices 133,167 Contains no impervious area; 5 0 No treatment required I 6 and 7 Flow-Through Planters 19,833 Total - 153,000 I Table 7-Summary of Approaches 3J' BMW of Tigard Page 9 of 13 9 9 Stormwater Report Water Quality Manholes There are two (2) proposed pretreatment manholes onsite (CWS Standard Dwg. No. 250). Inline WQMHs are sized using the 25-year post-developed runoff rate for the contributing drainage area. Per the CWS D&C, the following equation was used to size each WQMH. Sump Volume = ( 20 cf/ 1 cfs )x( 25-yr Peak Flow) Table 8 outlines the required sump dimensions for each WQMH. ' Structure Post-Dev. 25-yr Peak Pretreatment Sump Dimensions Subbasins Flow(cfs)(1) Volume (cf) Diameter(in) Height(ft)(2) ' SDMH OS 1 + 2 1.36 27 60 60 1.4 3 SDMH 03 4 1.24 25 1.3 -* 3 Table 8-Water Quality Volumes and Flow Rates ' (1)See Technical Appendix:Hydrographs; (1)Minimum sump height is 3 ft. HYDROMODIFICATION MANAGEMENT ' Hydromodification Assessment Per the CWS D&C, a Hydromodification Assessment was performed to determine the Project Category of the project site. It was established previously that the project site discharges to Ash Creek. The assessment was based on the following factors. ' • Reach-Specific Risk Level -The CWS Hydromod Planning Tool indicates that Ash Creek has a "Moderate" Risk Level. • Development Class -The CWS Hydromod Planning Tool indicates that the entire project site has a ' Development Class of"Developed". • Project Size - Project Size is based on the new& modified impervious areas created by the project. The total new and modified impervious area results in a "Large" Project Size. ' Project Category Based on the Risk Level, Development Class and Project Size indicated above, this project is considered to be ' Category 2. Hydromodification Approach ' The proposed hydromodification approach is Peak Flow Matching Detention via an underground detention facility. The following section will determine if additional water quantity control for conveyance is required. DOWNSTREAM ANALYSIS Design Guidelines ' CWS requires a downstream analysis when a project proposes new impervious area of greater than 5,280 sf or collecting and discharging greater than 5,280 sf of impervious area. Per section 2.04.2(m.3(A)) of the CWS D&C, the analysis must demonstrate capacity in the downstream system for the additional volume of water generated by the development.The analysis shall extend downstream to a point where the drainage from the proposed development contributes less than 10% of total flow.When the flow drops below the 10%threshold the analysis must continue for 1/4 of a mile or until the additional flow is less than 5% of total drainage flow. BMW of Tigard Page 10 of 13 Stormwater Report Design Considerations For the following sections, please see "Technical Appendix: Downstream Analysis" for supporting documentation and exhibits. ' Model Overview An XPSTORM model was developed for the storm drain system that directly receives discharge from the project site.The end of the analysis is located at approximately 0.25 miles downstream from the project. CWS Storm Sewer Map and publicly available Lidar data from the Oregon Department of Geology and Mineral Industries (DOGAMI)were used to determine all contributing basins to the outfall of this analysis. When pipe slopes were unavailable, conservative slopes were assumed (e.g., 0.5% or grade above). The analyzed downstream storm system consists mainly of open channels (e.g., ditches). For each reach of open channel between junctions in the model,an average trapezoidal cross-section was estimated using Lidar data. There is a confluence at approximately 400 feet downstream from the project in which flow merges with discharge from Cascade Avenue to the east via a drainage ditch between the 10065 & 10075 SW Cascade Avenue properties. The contributing discharge to this ditch includes runoff from Cascade Avenue, which consists of this project's frontage improvements, and a vegetated swale that receives runoff from a 42" CMP pipe underneath OR 217 freeway. The slope and contributing drainage area for the 42"CMP crossing OR 217 are unknown. However, assuming a slope of 0.5% and peak open-channel flow (i.e., 94% flow depth), the Manning's Equation was used to estimate a flow of 77 cfs (rounded up to 80 cfs)for the culvert.Although the peak flows would differ between storm events, 80 cfs was applied at culvert outlet (node "D1 U/S") for both 25- and 100-yr analyses for conservativeness. Hydrologic Characteristics , Web Soil Survey was used to determine the hydrologic soil group for each basin. All basins were underlain with soil type D. Aerial imagery was used to determine that the pervious areas mainly consist of landscaping and impervious areas consisting of pavement and gravel. For soil type D, pavement, gravel, and landscaped areas were analyzed with curve numbers (CN) of 98, 91, and 84(lawn, fair), respectively. Each subarea was assigned a reasonable time of concentration based on basin size and imperviousness. ' Typically, smaller and more impervious subareas were assigned a time of concentration of 5 minutes. Larger and/or less impervious subareas were assigned larger times of concentration. Impervious and pervious areas were delineated and quantified using aerial imagery. Spatially-weighted impervious fractions were determined when a subarea consisted of multiple land uses. Results , Table 9 outlines the results from the downstream analysis (See Technical Appendix: Downstream Analysis - Runoff& Conveyance Data). Recurrence Flow Rate (cfs) Min. Freeboard Flow from %of Flow from Site Interval (yr) at Outfall in System (ft) Site (cfs) w/ Respect to Outfall 25 102.53 1.08 3.06 3.0% 100 107.01 1.06 3.57 3.3% Table 9 - Downstream Analysis Results 3J' 1 � BMW of Tigard Page 11 of 13 Stormwater Report The table above indicates that the downstream storm drain system meets the 1-ft freeboard requirement during the 25-yr storm event. Furthermore, a conveyance analysis of 100-yr storm was performed, which ' demonstrates a freeboard of 1.06 ft (i.e., no out-of-system flooding). In conclusion, there are no expected downstream conveyance deficiencies; therefore, quantity control for conveyance capacity is not required. WATER QUANTITY MANAGEMENT Design Guidelines & Criteria ' The project shall meet flow control requirements per City of Tigard and CWS standards. Due to the results of the Downstream Analysis, only hydromodification management is required in designing a Detention Facility for Peak Flow Matching. Table 10 summarizes all flow control requirements for the proposed detention facility. Post-Development Predevelopment Peak Peak Runoff Rate Runoff Rate Target 2 yr, 24 hr 50% 2-yr, 24-hr 5-yr, 24-hr 5-yr, 24-hr ' 10-yr, 24-hr 10-yr, 24-hr Table 10- Flow Control Criteria 1 LIDA Feasibility Due to the lack of onsite infiltration, LIDA approaches cannot be implemented to address quantity control.As a result, Underground Detention will be implemented to meet the flow control criteria. ' Over-Detention &Target Release Rates The proposed detention facility will over-detain for the runoff from post-developed Subbasins 5 through 7 to the maximum extent practicable. Table 11 outlines the target release rates from the proposed detention facility. Recurrence Predeveloped Post-Dev. Runoff for Target Release Rates Interval (yr) Runoff(cfs)(1),A Subbasins 5-7(cfs)(2), B (cfs),A -B 2 0.215(3) 0.317 -0.103 ' 5 0.791 0.420 0.371 10 1.027 0.481 0.546 Table 11 -Target Release Rates (1)See Table 5.(2)See Technical Appendix:Hydrographs;(3)Target release rate is Yz the 2-yr predeveloped peak. Since runoff from post-developed Subbasins 5 through 7 exceeds the predeveloped runoff from the entire site during the 2-yr storm,the diameter of the low-flow orifice with the flow control manhole will be set to the minimum size of 0.5". Runoff from the 2-yr storm will be detained to the maximum extent before proposing additional outlet devices within the flow control manhole. ' Quantity Control Approaches Detention Facility Subbasins 1 through 4 discharge to a storm drain system that outlets to a proposed underground detention facility, a Contech CMP Detention Facility consisting of 48" perforated pipes surrounded by drain rock (See Technical Appendix: Exhibits-Contech CMP Detention Facility-Stage-Storage-Area Table). Outflows from the facility are controlled by a flow control manhole, SDMH 01, as detailed in Table 12. 111 1 BMW of Tigard Page 12 of 13 Stormwater Report Structure Low Flow Orifice Overflow Weir Sump Outlet I on Plans Dia. (in) Center Elev. Length (ft) Crest Elev. Elevation Pipe IE SDMH 01 0.5 189.80 5 196.60 187.80 191.80 1 Table 12- Flow Control Manhole Release Rates I Table 13 compares the post-developed release and target flow rates. Recurrence Peak Release Rates (cfs) I Interval (yr) Target Post-Dev. Difference 2 -0.103 0.015 -0.118 I 5 0.371 0.299 0.072 10 0.546 0.375 0.171 Table 13- Post-Developed Release Rates I As mentioned before, the 2-yr target rate cannot be met due to the unmitigated runoff from Subbasins 5 through 7 exceeding the predeveloped runoff from the entire site. However,the runoff will be detained to the I maximum extent for the 2-yr storm and all other required flow criteria are met. HYDRAULIC ANALYSIS I Design Guidelines In accordance with the CWS D&C, the private storm drain system was sized to convey all storm events up to I and including the 25-yr with a minimum freeboard of 1 ft of freeboard.Additionally,the 100-year storm event will be conveyed without any out-of-system flooding. Methodology I As with the hydrologic analysis, XPSTORM was used to perform a dynamic routing analysis based off runoff rates derived via the SBUH method.An XPSTORM model was developed and evaluated for the post-developed 111 basin (See Technical Appendix: XPSTORM Output- Hydraulic Layout). System Performance I In post-developed conditions,the proposed storm drain systems are expected to sufficiently convey flows for up to and including the 100-yr storm event with no out-of-system flooding. The minimum freeboard in the storm drain systems was determined to be 1.37 ft during the 25-yr storm event (Technical Appendix: I XPSTORM Output- Conveyance Data). OPERATIONS & MAINTENANCE I An Operations & Maintenance Plan (OMP)was prepared to provide a single-source document to explain the maintenance requirements for the proposed stormwater management facilities onsite. The OMP is included I in the Technical Appendix. BMW of Tigard Page 13 of 13 Stormwater Report TECHNICAL APPENDIX Exhibits - FIRMette - Hydrologic Soil Group - Curve Numbers - Existing Conditions - Post-Developed Conditions ' - Contech CMP Detention Facility- Stage-Storage-Area Table Calculations - Time of Concentration ' Hydrographs - Runoff Hydrographs ' - 25-yr Runoff Hydrographs (for Pretreatment Manholes) - Release Rate Hydrographs (for Flow Control Manhole) - Stage Hydrographs (for Detention Facility) ' Hydraulics Analysis - XPSTORM Hydraulic Layout - XPSTORM Runoff Data ' - XPSTORM Conveyance Data Downstream Analysis ' - Clean Water Services -Sewer Map - Hydrologic Soil Group -Washington County - Downstream Analysis- Basin Map ' - Pipe Flow Calculation -42" OR-217 Culvert - XPSTORM Hydraulic Layout - XPSTORM Runoff Data ' - XPSTORM Conveyance Data Operations & Maintenance Plan REFERENCES 1. Design & Construction Standards for Sanitary Sewer& Surface Water Management. December 2019, Clean Water Services 2. Urban Hydrology for Small Watersheds (Technical Release 55). June 1986, U.S. Department of Agriculture 1 3J' � EXHIBITS 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ,..... g fi - Q 1 m c E.E :41 I 4" 1 0 — n L'-' v ...., 03 .$ < ; % 2 A ,„ I. , -2s-6-2 'A'RI 1 ,, v 5 5 6-. l' 1 Z 4) --,.; II z A. , --+_. it ,,,,, . . ..E; E * 1.4,5„tw ca ,z, 08 -EgZ/ Q g2tE"- o 4+ • a , c ig = ,,, ....7, C 4 11) 0 1 CSC -p0 2 V ti 2 i G 'R ,, It ; Lz g. 'r; A I 4 '4v ,.--;: 22: - t-IL,Z4-clt ..pegtxx. i it 1. - 14-. 2 E LT-= ilt '' '" i 2 . 1 ;Illgt- 1.18. 2 t e IT; i5tc-E .13.z :gr:t 'S g am t lb- 21 fgt. till, 1 .--' vi1 ize. '-i ,. 'vg 8-aftl 2 se it ! zt 1 1 ,,,i 7 .1 .2 . 2 ; i _i . g . 31- 10 ,-. _ 2 . ,.. Et I 9 ,73-„!', g' gi .,_ .‘3 ,. ..S47; .,-• ..- / .. 4";.) 74 II 15 -4 .1 2 r -.'i ? `t 1 2 r, " t 4 5-' 8m '-'73 ° :;2Eli 11 -'. t'I'sg. 4*1. ; E 4' a; ..,!, ,c'. 1 : agt IS! I3N `i -2 4 :ro 'LI 4 c! `1"6n-z! lz— E:It1113 Z2iii-E 1 -.E,' 4...._•5 it 4-4t„, i g2 ill E E = r az aiSaf4 -..:, P, 3 z i 6 z ' 1.?.., tiG1 f. ,,,g ,,,, ,e . m m u. 0 d -.I .1 ••ze w 4 .4 a 1 g e [2alit 14, 21-!1 , . -- • - fl ..1! ti i - et I, El: Li 0 I I , 0111 . - - 14 ... I S. I :IWO 142,LT. a., 2 fit2 §17 6. II , 9 4 7, . z I : It • : C) - - • tEal ,,,,It-o4E0,1 ? 0,2fga t: 1. 0 0 ...114 5 5 ,,T, i'v =AigtE -.1; g2,gg, 0 ocr kir < . w , ,.. . gt 1 . = ., z ,...,.., . 0 D a. g0 CD 1 0 co - z3 4t Er 0 r 1- a co 12 i,i1 8 4') . , h ' I ' 100-71nrS4P,004111"4"*** OW , \ 't*r': a I n'i 4:lir 0§.. .,0' 11. V001 I r) 1,:-47„, 1 a) , ,. _ tn411118: ,.. llat)s'v V 0 et- ailliMi ,,,,,,- t* — U. go R.. 5/4' I LL ' ''''''' '''', , , IA,' ,.. ..,.. ..-1 . igt ittl: , „ , . cti , i. Ifi , 0 8.','. C-- . :, ....... I 73 0 s f 3 .4. >.e., ,,, 4*, 0,,,0 • 4 k . ,;: , I L.T... ' ' le e'4661 , 44 4/5 . I C MI 0 '-' , Q i ,,,,Y , kt , 4-0 i-, ,. . k t I c•Z -J , , aui '''' ' I I Z Z LI n 1 1"s ooszco9 mews OVEZEOS 01.132409 OBLZ605 09jl£ N M„6S,9b oZZT M„65,9b oZZT N O s!, 0) N C-3 CZ o ......-. "Crh w, tO 2A 1 cascade Pv S14 i 1 .1 ..„, ffi ► • , I g: (° ''f .4ilk 1 8: 4 176 an to •o :,I' N i LZ 8 I i V N I I •N • /,/ .../ xig 1p O�� lr N-111 M7 a to �, ' b �'v 8 ! U LI:f OL 3 li 1 z l0 O ', T 2 () M.bi Lb oZZT 'n ti� - ``. M bi 1b olli 0 1 oT N Z N I I I 4- 0 0 N N -° o ° CO a m o d w o rn 7 y ` N N N y O O as I "' N N O N I iii CfC ° >. O O ° 2 —O U O co O O co Z co E ai a c°p ° g .0 c w Q [A c E w 0 m� E � 15 f0 c� c@yy �' °'N ° ¢ ww � y c) E o c" L Z o Lt °� co _ o m 0 U` c Z z O U p E V1 Q 3 w ° rn� o co c a °� 73 d 5 o Q U N o m L 2 L y I 0 CO a3 E U W a o at @ cN o o- C i m a w/ U �0 t d _co `p N N = 0 j V p 'O a T LL co E co o ` c o a� a o CO a•- y o O j D O N N 7 U T N .L• O U y C c h O E T a E LL m o - c > o N o o c c E o o N cn L CO E a y Z d L o d -° t N iti 12 .0 7 cn U O y ° -O 13 c o w N N D °> N I a o > co o To U @ Z ° a ° ° ° co3 73 ° o _� w Q U O U N rJ ° f0/! aO ° � > L N L � O C E O N L L Z a E a) Qa U p C m O N O - C caa E a'H -c >. r 2 m - a)o'm w co `o rn E ° •°' >, 7 >' - p 'O N C . a N T N U f0 f6 7 •N -O 0 ..� O U O• a O c as C Vl O c CO Z co w L .O U C Q �o O 'O a fC 7 to °> � Ern TTD � � � o E � o � coi aTi �' � o y oCU N O O U f6 O N 7 O O C O O U p f0 > 7 >+ O O y,- 01 O c N o E co e) ° ` o ° ccoo a m `o a.°°^' m 0 7 N-c - Z E o N N °oi E a. N i L N O C y C O U _N N p >d O f° O N _L U L ,� .O 7 .O S? M CV L p E L CO N i- , > W E _ U co a E co 0 2 O.'O Q@ O co co co — O r 1— U .— N O K ii o .o c o co > m - I. o a m a O N o ° m c m U (7 o co U t m To C O Cl) O = N N N O ca C) E o o a z CO _ O vi N Q' O_ m o ❑ o a c m co m c a� T 0 U 0 Z �f) O c 7 •a Q I 0 m ii t o Z ia n ® ® LL L H co Y W c m 0IC m a °' a a 6 O ti co C C U C 0 O ° C co 17 N N C I Q O o ` C N < O) Q a m m U U ❑ Z O/ Q a m m U U ❑ Z pf < a m Ca Hal nElE ❑ ❑ 1 1 1 1 1' 1 : o ■ ■ ■ ■CO �� r p y N N 3 O Q to y O cc N m y 7CO 0 Z (.,) IHydrologic Soil Group—Washington County,Oregon I Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Aloha silt loam C/D 3.2 63.6% I 13 Cove silty clay loam D 0.2 4.9% 2225A Huberly silt loam,0 to 3 C/D 1.6 31.5% percent slopes I Totals for Area of Interest 5.0 100.0% IDescription Hydrologic soil groups are based on estimates of runoff potential. Soils are I assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. IThe soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (ND, B/D, and C/D). The groups are defined as follows: I Group A. Soils having a high infiltration rate (low runoff potential)when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water Itransmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well I drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. I Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of Iwater transmission. Group D. Soils having a very slow infiltration rate (high runoff potential)when thoroughly wet. These consist chiefly of clays that have a high shrink-swell I potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. IIf a soil is assigned to a dual hydrologic group (ND, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in I their natural condition are in group D are assigned to dual classes. tu,a Natural Resources Web Soil Survey 10/19/2021 small Conservation Service National Cooperative Soil Survey Page 3 of 4 I Mk IHydrologic Soil Group—Washington County,Oregon I Rating Options Aggregation Method: Dominant Condition I Component Percent Cutoff: None Specified Tie-break Rule: Higher I I I I I I I I I I It,,DA Natural Resources Web Soil Survey 10/19/2021 .mill Conservation Service National Cooperative Soil Survey Page 4 of 4 I I Chapter 2 Estimating Runoff Technical Release 55 1 Urban Hydrology for Small Watersheds Table 2-2a Runoff curve numbers for urban areas 1/ misimmi Curve numbers for ---- Cover description — - — hydrologic soil group I Average percent Cover type and hydrologic condition impervious area 2/ A B C D Fully developed urban areas (vegetation established) IOpen space(lawns,parks,golf courses,cemeteries,etc.)3/: Poor condition(grass cover<50%) 68 79 86 89 Fair condition(grass cover 50%to 75%) 49 69 79 84 I Good condition(grass cover>75%) 39 61 74 80 Impervious areas: Paved parking lots,roofs,driveways,etc. (excluding right-of-way) 98 98 98 98 I Streets and roads: Paved;curbs and storm sewers(excluding right-of-way) 98 98 98 98 Paved;open ditches(including right-of-way) 83 89 92 93 I Gravel(including right-of-way) 76 85 89 91 Dirt(including right-of-way) 72 82 87 89 Western desert urban areas: Natural desert landscaping(pervious areas only)-4/ 63 77 85 88 I Artificial desert landscaping(impervious weed barrier, desert shrub with 1-to 2-inch sand or gravel mulch and basin borders) 96 96 96 96 Urban districts: I Commercial and business 85 89 92 94 95 Industrial 72 81 88 91 93 Residential districts by average lot size: 1/8 acre or less(town houses) 65 77 85 90 92 I 1/4 acre 38 61 75 83 87 1/3 acre 30 57 72 81 86 1/2 acre 25 54 70 80 85 1 acre 20 51 68 79 84 I2 acres 12 46 65 77 82 Developing urban areas I Newly graded areas (pervious areas only,no vegetation)5/ 77 86 91 94 Idle lands(CN's are determined using cover types I similar to those in table 2-2c). 1 Average runoff condition,and Ia=0.2S. 2 The average percent impervious area shown was used to develop the composite CN's.Other assumptions are as follows:impervious areas are I directly connected to the drainage system,impervious areas have a CN of 98,and pervious areas are considered equivalent to open space in good hydrologic condition.CN's for other combinations of conditions may be computed using figure 2-3 or 2-4. 3 CN's shown are equivalent to those of pasture.Composite CN's may be computed for other combinations of open space cover type. I 4 Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage (CN=98)and the pervious area CN.The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition. 5 Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4 based on the degree of development(impervious area percentage)and the CN's for the newly graded pervious areas. I I (210-VI-TR-55,Second Ed.,June 1986) 2-5 I Chapter 2 Estimating Runoff Technical Release 55 Urban Hydrology for Small Watersheds 1 Table 2-2c Runoff curve numbers for other agricultural lands 11 ICurve numbers for - ------- Cover description ---- ------ --- hydrologic soil group-- Hydrologic ICover type condition A B C D Pasture,grassland,or range—continuous Poor 68 79 86 89 forage for grazing.2i Fair 49 69 79 84 IGood 39 61 74 80 Meadow—continuous grass,protected from — 30 58 71 78 grazing and generally mowed for hay. IBrush—brush-weed-grass mixture with brush Poor 48 67 77 83 the major element.1/ Fair 35 56 70 77 Good 30 4/ 48 65 73 IWoods—grass combination(orchard Poor 57 73 82 86 or tree farm).5/ Fair 43 65 76 82 Good 32 58 72 79 IWoods.5' Poor 45 66 77 83 Fair 36 60 73 79 Good 30 v 55 70 77 IFarmsteads—buildings,lanes,driveways, — 59 74 82 86 and surrounding lots. I i Average runoff condition,and Ia=0.2S. 2 Poor: <50%)ground cover or heavily grazed with no mulch. Fair: 50 to 75%ground cover and not heavily grazed. Cood: >75%ground cover and lightly or only occasionally grazed. I 3 Poor. <50%ground cover. Fair: 50 to 75%ground cover. Good: >75%ground cover. 4 Actual curve number is less than 30;use CN=30 for runoff computations. I 5 CN's shown were computed for areas with 50%woods and 50%grass(pasture)cover.Other combinations of conditions may be computed from the CN's for woods and pasture. 6 Poor: Forest litter,small trees,and brush are destroyed by heavy grazing or regular burning. Fair: Woods are grazed but not burned,and some forest litter covers the soil. I Good: Woods are protected from grazing,and litter and brush adequately cover the soil. I I 1 (210-VI-TR-55,Second Ed.,June 1986) 2-7 I 0 I X L 0 m r` Ln in m c000 coo m Lfl Ln m c000 m Ln Ln N m M p Q "o 0 0 = N m_ m_ v v v v v v _m m_ N 1— 0 0 0 1-1 a) Q O 6 6 O 6 6 0 0 0 06 0 0 0 6 0 0 6 0 CC 1 ns 1- as ar Q o Ln o Ln o Ln o Ln o in o Ln o Ln o in o Ln o N = 4 O N Ln N O. N Ln N O N Ln N O N In N O N Ln 00 0 0 0 0 s- .- N N N N m m M m 4 4 V I ro Ln Ln CoN 4 O N L0 O � O O N Lfl CO V n Co '0 O N N 1/40 0 L- 0 O Ln CO Ln M Cr) 74 ko O O N m Cr Ln Ln Ln Ln Ln Ln Ln Ln V m N O 01 N V N T Ln «1 N LD .- m N M m m Cl LO V Co .- p E O O m LD OC LD (0 r N. LnLn in tT Ln O Ln Ln N 00 Ol CO N to in m 7 N m Ln LD 00 al c- .- v- .- s- NN N N CV N 7 O I U > V a�� a- 1/40 Cr1- CO N N Ln N CO 1/40 N CO O N CU O N N Co L0 N Cl N L0 O on in L0 4 Cl O N in N III t 11 O m V O LID N co Ln N CO d- O 1/40 - N .- N N N• m m Ln Ln LO n r 00 W Ol Cl Q1 NO Ln t u C L4 O O O O O O O O O O O O O O O 0 I m in 00 W 4 No CO LD V N C. CO 1/40 V No coLD 4 73 W O V Cl V O N Co m M 4- 4- Ln Ln LD LD O N N al ri W oo Co W I al 40 La O - N O Cl N Co N CO Co CO' r� CO Ln Ln LD LD L0 V m M m N Ln > o Lo m � "�' � � o0 0o rn Ln N m o � � � La LD 00 O N V LD Di d- N Ln a- N N N i O V W N N N N N m on m 4 V Lrl Ln 0 < I _� C Ln 4t O LD N N d' ,r V LD rf LD CO CO 00 p m a O m L�0 LNn Co . N .. c- a— O CO . n LD 0r1 N N N LLO ,_ Cn LO Ci m N Lf) C1 Cr) LD O (ii LD co O O o m a N N N m m V V d V Ln Ln Ln I C LL O C v v p O O N N N m m d N - Ln co COi Cl LLnn Lin o N o N n. 00 a+ O N CO O Cl co N N LD Ln v m (N O CO v Cr) m O .a LD t- N m m V Ln LO N co Cl to U Ln al _ +-r C C C O N I U m in O LD N00 .7 O LO N 00 V O LD N CO V O LD N CO O V 00 Ln CO N LD Cl cci Lc-..) 4 N 4in C O m ^ ,- s- N N N Cr) m m V V Ln Ln Ln 0 0 lL I C" � „0 `" m M Cl V un LD r N Cl N CO 0 0 0 N O N Co LD V O LD LD N CO LO LD O N m CO M Ln > O to N LO CO (6 O• •m LD• •oo O N 4Ln N Co O m Ln CO O Cn CO m a) i c- r- .- - N N N N N m M Cr d' Q C U C L in co O N V 4 Co m Cn N Co N Co N o a, m C1 CO O Cl Co Co CO r\ 1/40 CO Co Cl N N N N a, rn a co rn • Co CO o N Ln oo .-• v o N v LD N N N a a) p, 0 0 N ^ ,- c- N N N CO M m m m m M `0 m Y v = a L;, f0 bp LL N 0 Ln O Ln 0 Ln 0 Ln O Ui 0 Ln O in 0 Ln 0 Ln O C 8 I = O N Ln n O N Ln N CDN Ln N O N Ln N O N Ln 0 0 Y 0 0 N N N N m m m m 4 V La ) m s v La w 0 Lnn CALCULATIONS gr- I ,,, ) TIME OF CONCENTRATION PROJECT NO. 21684 BY PJP DATE 6/2/2022 IPREDEVELOPED CONDITIONS -ENTIRE SITE SHEET FLOW I INPUT VALUE Type Surface Description Woods I (light_underbrush) Manning's "n" 0.4 Flow Length, L 50 ft I 2-Yr 24 Hour Rainfall, P2 2.5 in Land Slope, s " " ft/ft OUTPUT ITravel Time 0.18 hr SHALLOW CONCENTRATED FLOW IINPUT VALUE Surface Description Unpaved I Flow Length, L 325 ft Watercourse Slope*, s n 022 ft/ft OUTPUT VALUE I Average Velocity, V 2.39 ft/s Travel Time 0.038 hr I CHANNEL FLOW INPUT VALUE Cross Sectional Flow Area, a . ft2 IWetted Perimeter, PW 0 ft Channel Slope, s 0 ft/ft Manning's "n" 0.24 IFlow Length, L ft OUTPUT VALUE I Average Velocity 0.00 ft/s Hydraulic Radius, r= a/ PW 1.00 ft Travel Time 0.00 hr 1 Watershed or Subarea T,= 0.21 hr Watershed or Subarea T,= 13 minutes I I 3J CONSULTING ,VL tN ^i EERINC WAIFR RES<URL,'3 (LAIMUE:LTV PI ANN4NG I NYDROGRAPHS ' HydroIogis Analysis - XPSTORM Hydrographs IPredeveloped Conditions Runoff Hydrographs (cfs) I mum um. Predeveloped Conditions UIIIIIIIM 2-Year[Max 0.429] 5-year[Max 0.791] 10-Year[Max 1.027] 25-Year[Max 1.351] 14 I\ I 1.2 I 1.0 0.8 3 I 0.6 I 0.4 I 0.0 1 Sat 3AM 6AM 9AM 12PM 3PM 6PM 9PM 2 Sun 3AM 6AM 9AM 12PM Jan 2022 Time IPost-Developed Conditions - Entire Site I Runoff Hydrographs (cfs) Post-Developed Conditions-Entire Site 11•11111111 MINIM OEM Ell= 2-Year[Max 2.117] 5-year[Max 2.693] 10-Year[Max 3.031] 25-Year[Max 3.467] I 3.5 3.0 1 2.5 1 i 320 0 tL 1.5 1.0 _____„7/,) '\14\\. .%...,.,,,.,.,....,...._._.......................... 0.0 1 Sat 3AM 6AM 9AM 12PM 3PM 6PM 9PM 2 Sun 3AM 6AM 9AM 12PM 1 Jan 2022 Time I 3.t/ 1 of 4 Post-Developed Conditions - Subbasins 5-7 ' Runoff Hydrographs (cfs) Post-Developed Conditions-Subbasins 5-7 2-Year[Max 0.317] 5-year[Max 0.420] 10-Year[Max 0.481] 25-Year[Max 0.561] 0.55 0.50 0.45 0.40 � 0.35 g 0.30 0.25 0.20 0.15 0.10 0.05 0.00 1 Sat 3AM 6AM 9AM 12PM 3PM 6PM 9PM 2 Sun 3AM 6AM 9AM 12PM Jan 2022 Time 1 I 2 of 4 I 1 25-yr Hydrograph - Pretreatment Manhole SDMH 03 I 25-yr Runoff Hydrograph - SDMH 03 25-yr Peak Flow=1.24 cfs IMIN Flow I 1.2 1 1.0 0.8 I U 0 0.6 LL ' 0.4 0.2 I 0.0 1 Sat 2 Sun 3 Mon 4 Tue 5 Wed Jan 2022 Time 25-yr Hydrograph - Pretreatment Manhole SDMH 05 1 25-yr Runoff Hydrograph - SDMH 05 25-yr Peak Flow=1.36 cfs MINIM I Flow 1.4 1.2 1.0 I 70.8 3 2 0.6 0.4 0.2 0.0 ^iNd Nd^J vPU. 1 Sat 2 Sun 3 Mon 4 Tue 5 Wed 1 Jan 2022 Time I I I 3�/ 3 of 4 Release Rate Hydrographs - Flow Control Manhole SDMH 01 I Release Rate Hydrographs(cfs) Flow Control Manhole-SDMH 01 2-Year[Max 0 015] 5-year[Max 0.299] 10-Year[Max 0 375] 25-Year[Max 0.483] 100-Year[Max 0.755] I 0.7 111 0.6 0.5 I 0 0.4 0.3 0.2I Iht I 0.1 00 , ... ., 1 Sat 2 Sun 3 Mon 4 Tue 5 Wed I Jan 2022 Time Stage Hydrographs - Contech CMP Detention Facility I RIM of SDMH 01 = 198.33 Stage Hydrographs(ft) Contech CMP Detention Facility 1 IIIIIIIIM rMEM 2-Year[Max 196 596] 5-year[Max 196.671] 10-Year[Max 196.684] 25-Year[Max 196.700] 100-Year[Max 196.735] 196.5 I 196.0 195.5 111 195.0 m194.5 ir m 1 194.0 1935 i I 193.0 192.5 192.0 I1 Sat i 2 Sun 3 Mon 4 Tue 5 Wed Jan 2022 Time I I 3l 4of4 I 4* HYDRAULICS ANALYSIS 1 1 Hydraulic Analysis -XPSTORM Hydraulic Layout C013 • 1 C604 • Hi05 PT CO23 r *104 WO CO• 03 111 MH 021P40 • 03 PT MN 01 FC • �. OMY FC • •T OUT C8 01 r I I A 1 J'� I 1 o t.o o, N illo m ko E a • o 0 0 0 ' aLn 0 0 0 0 0 0o a 4 4 4 4 jcpw N N m VI W szt a U <- O O O E O a �+ - C a) Ol o--, Ol Ol N a IA rri cri ni ri fri I L0 Ql l0 h 00 O O N �7 } W a U r- O O o Q QO V f� •a u1 In u1 Ln Ln 0 VI o a m n I < i m m m CC } z = O CO U) N rn N m N I 0 w' a V O O O O O ld7 O E 1- V O 4- WI O � -acO o 0 0 0 rri rri rri aJ ao J 0_CO W I W Q C2I C Y u, N Cr) o N m Q N w a V O O O O O L.L. 0_ E L.L. ICC z cL •a o 0 o O o c Ln ui Inui in cc CV a N N N N N 2 I I 0 H X - ul if) LC) ill In In II) if) in if) E a c Z co 0 co O 0o o co 0 0o 0 mU O1 CO 0-1 COOl CO O-% CO CT co I E CO a3 a s o O o 0 0 l - E O o 0 0 0 0 0 0 0 0 0 c m CO O-, N O) N N l0 a) ° m 0 N O m 0 O V m IQ O r- O O O O O O O a) O tf'1 O O Li) Z Z O O V V co i I o � o0ornd 0000CD0 1 a vNN mvr\ uimrn M N 4 d' O Ni d' N k0 k- I co O O O co co O 0000 lO • ' O O O O 6) r- O O ul O in N N N r� N x v N rn I lD 10 o o o k6 o > c) N N 4 4 O N d' N 4 O VI 01 01 01 0) 01 O) 0) 6) 6) 0) 0) 2 0 -J 00 O O O C) N 0 0 0 0 t.I X u1 CO m M Lf) CO CD6) N N l.9 0 0 0 0 Cr? In N 0 r� 0, N ,N VO N NVD CO Cr) dt u1 ‘.0 N I � l0 �D �DD �D �D �D n M d' N 0 dr CO m N d' N 0) 0) al 6) Q) 0) 6) CS) Ol 0-1a.) v 0 w aN N N N d'rn co ON M M m m -+ N co 0 iD - N L) LU d' LD N QU X ,- ,- 00 — - - v— oo v) Mcri r� criri cri m Q F 2 UZ w gcw X in LI) r� co00 dr co00 m d' St G f6 m N dr Ol O) O r� inO N 0 ,- 41 -' in N 00 lD m co d• Lf) N CO Cr) O cn _ I d -O , O O O O O O O a - M M - tD r M m r) ) N V L N 4-J Q Q D Q } C O O O O O O) O O I f) O 0) (?O V to r- CO L!) N N CO 1:3O Lll 0) O O CO O. L!) O 0 CO CO Lf) N '� C6 — CO Lf) - d' Lf) U) O) d' N U In , Cr; N N Lf) N N r� u'1 aJ O M O O �O N O 4 d' 0 00 0) 0) co 6) a) 6) 0) co co 0) N O• V1 U O O r) ~ (�C m Lf) O O O O 0) in O 0) N m z Cl Ln O O O M in in O . N LLJ CO 61 0 0 00 n 00 O in CL Q 0 O O O m O O O u) M iI) U1 6) N N n al N in u1 r� O N r- O) 00 6) 6) 00 6) 00 6) O) O) O) w w Q v oo v� U0- t I } --I 0 to o0 o O 0 0 o 0 0 j v u`Di m Cr) Cr) rn Cr COm co rn O ~ = J OIN O ,- N N p N rrsj D Q lL ` O O 0) Cr) 0) 0) O 0) O 0) 0) I UN7j O c 0 a U N 'D O v r� 0000moomr� o j mdr1Onmmm � Nrnoo N E Q. O O o 00 o O 0o i0 Ln I v ai o 0 00 00 0 o rn 00 6i a CO o o k- s- o 0 0 N w 0) o 0 6) 6) N o o 0) 0) 0) X 0 >o U o a. H >o> U o � U Hcs_O N wQ 0 O 0 0 0 O rcl 0 CO N Q 0 O d' p 0 0 O = 2 = U 2 = = U = _ _ U 2 = = U C 2 2 2 2 2 2 co 2 g 2 2 2 2 C ro n a ro c V) I- a H O 0 E oCO i- 1 � u)a. N00 o E off., 1— - LI)ci Noo Co O _ _ _ _ lmJ u v0 0 = 0020 op OU = = O m u III J J O N i1'1 N m �D CO Co N. N d' ul N M lD CO 0) O Q) 0 0 0 0 0 0 0 6) CS) al 6) 0 0 0 0 0 0 c _Y _Y _ c J C C C C C C C C C C C J CCCCCCCCCCC J = = J J J J J J J = J J .----I 11 = = J J J = I 0 Ov •Ztd- Meo CI" � MUlCO I 'gyp o `� I", h N `� r, it) Cr) T V N 4 4 O N 4 N iD I N N N m N N N N N N J tr ice-+ N •I d" Cr) Cr) `� al I� t\ N N N N N n X N N V I� N _ ' O O i0 O O O > 0 NiN NiN 4 o — r. 4 N 4 o v) al al al al Ol al al a1 al al O-' I _ __IN `r V M N lO X O N 00 LC) Cs CO u1 m in co V 0 in N N N O O N N N N N if„,,' (.0 U N N Cr) I< ul in t.O kO N O� N = Q � � 00 iD lD �O N DD O l0 � � t\ Q a1 (Ni O ul m M N N M 4N cn al Oi Ol Ol al al al al al a-) ✓ > v) w Q LL 4�- Cr) N m yell u�l CO M O N. co ull O o ^ O �fl_ 4 QU x U a- e- Ci O a- a- O O Q M l'rl a- ,- I< Cri Nl a- M ,- f�'1 I < z U j D w C X 0-000 O M al N O N N N 00 ill C N N Cr) O N O N M I. g 2 m `^ QO `O rn ,- m lD °4 m O - w CO N CO ul m m in - m m 00E O N N O O O M O O O Otil o m M r- Lc; M� M M M .- N t~n 2 a c/ 4-4 w D I Q ce } C w 000006100 �norn � bO Li N C O a- CO n N a- N ul CO Oi O o CO O in O o CO 00 inO I- 0 � (0 y_ 00 Lc' ul Nu N ' al Ni Ni t\ Lc; Ni Ni Ol I� ul a1 Q. U O M o O LD N o 4 4 0 co al al 0o Ol Ol al Ol 0o o0 al N LL i 0 U r- l- l- c- a- a- l- l- r- O I 0 � Z N > Q aJ m H ul O O O O O1 ul 0 al N f20 d ul O O O m ul ul O - in N uJ W al O O CO N CO O ul N. D_ 0 Q 0 o o O M 0 0 o ul M ul u1 al N N a; N LC; ul N O) co al Ol co a> CO al O O) O 0 0 l O W Ua i } O O o 0 0 o 0 0 ,`� , C j VD k.0 Ln Cr) m Cr) rn N m ,- Cr) am Z 0 J O O O N N O O N N W O O Ql Ol Ol Ol O al O Ol O1 O 0 I o cea. 0 L- '0 O 4-,j NOOOOM o o CO NO yC„ j N in CO CO m v- N al O CO N E 'ID. 0. co. 0. 0. 00 O o 00 'D ui 0 a) rn O O o0 00 O o ai oo ai I o O 0 0 0 N W O o o CT) O o 0 o CT) CT) O X 0 r CL v_ > �CL- u_ - a u_ > CL F- u_ M Cr)N > V> LL Cr) M ~ N > in LL N FQ- o o p o S O o p o 0 0 FQ- o o p o S O o p o o O S S S O U S TSU S S M .-. UM S S tJ C 2 2 g 2 2 2 C 2 g 2 g 2 2 0 I > > � �, aa C � 1- >a Ha o O m N "- m in > N O O O EO M N Lu > m if) > N 0 0 Q O = o o 5 O = .1. O m CO � 0 = o p 022 = o O m U O N III N M l0 CO 01 N O N V ul N M kD CO Cr) Y O CT) a, 000000 Y O a, Oi a, 0-10 0 0 0 0 0 C Y [ Y Y Y 1 Y C Y Y Y Y Y Y J C C C C C C C C C C C J C C C C C C C C C C C J J J J J J J J J J J J J J J J J J J J J J I DOWNSTREAM ANALYSIS ic up E 8C) (.0 0E cv co c T O - _ m d O N c c 3 C0 D %'i-+ +' '' C J c O O -o .— -• (6 1— O p U w U O m O 0 Cl)co 0 0 O 06 7 O O > O '= Ca U it > d > H 70 d O > d U U U 00 1 ❑ 0 4 t t ' 1000 XU zQ U ftt • " _w 3 ♦ ,v{4` NiNto •v 8#i *moo YYY q C�p�O �F _ e in,y in 8 LT;v .t G � Bm 2 z� ., r a � S� P8"Y Ne8 CC L. , ti �a2 `_ ac� � x n +Y 4 RP p C Q,T rr.)^ , N 11 (I) "= ` -.Ec8- u3 u i ( r r 3"o s. - m CD E °) g_.E e� m,- -0 nVJ d ! O'( ) �- N g II E.coQ.) Ncts .f ENNP f # f0 Q) al* p `. 5g.40 �i2 In - E L t o AF. Z a a—N N Mg , iI 0 _ co p� C O .!,-' Q+� O yO YO . A,,L,F.,I:1 4.,,,,,,, - ', 4 it'-° � m �:z: .Via..-..* *, , _ o b7 is P .G I Chapter 2 Estimating Runoff Technical Release 55 1 Urban Hydrology for Small Watersheds 1 Table 2-2a Runoff curve numbers for urban areas 1i imilimmili 1 Curve numbers for — Cover description - -- hydrologic soil group I Average percent Cover type and hydrologic condition impervious area 2/ A B C D Fully developed urban areas (vegetation established) IOpen space(lawns,parks,golf courses,cemeteries,etc.)2/: Poor condition(grass cover<50%) 68 79 86 89 Fair condition(grass cover 50%to 75%) 49 69 79 r84� I Good condition(grass cover>75%) 39 61 74 �� Impervious areas: Paved parking lots,roofs,driveways,etc. (excluding right-of-way) 98 98 98 11 98 I Streets and roads: Paved;curbs and storm sewers(excluding right-of-way) 98 98 98 98 Paved;open ditches(including right-of-way) 83 89 92 93 I Gravel(including right-of-way) 76 85 89 91 Dirt(including right-of-way) 72 82 87 89 Western desert urban areas: Natural desert landscaping(pervious areas only)-4/ 63 77 85 88 I Artificial desert landscaping(impervious weed barrier, desert shrub with 1-to 2-inch sand or gravel mulch and basin borders) 96 96 96 96 Urban districts: I Commercial and business 85 89 92 94 95 Industrial 72 81 88 91 93 Residential districts by average lot size: 1/8 acre or less(town houses) 65 77 85 90 92 I 1/4 acre 38 61 75 83 87 1/3 acre 30 57 72 81 86 1/2 acre 25 54 70 80 85 1 acre 20 51 68 79 84 I2 acres 12 46 65 77 82 Developing urban areas I Newly graded areas (pervious areas only,no vegetation)5/ 77 86 91 94 Idle lands(CN's are determined using cover types I similar to those in table 2-2c). 1 Average runoff condition,and Ia=0.2S. 2 The average percent impervious area shown was used to develop the composite CN's.Other assumptions are as follows:impervious areas are I directly connected to the drainage system,impervious areas have a CN of 98,and pervious areas are considered equivalent to open space in good hydrologic condition.CN's for other combinations of conditions may be computed using figure 2-3 or 2-4. 3 CN's shown are equivalent to those of pasture.Composite CN's may be computed for other combinations of open space cover type. I 4 Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage (CN=98)and the pervious area CN.The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition. 5 Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4 based on the degree of development(impervious area percentage)and the CN's for the newly graded pervious areas. 1 1 I (210-VI-TR-55,Second Ed.,June 1986) 2-5 3 Hydrologic Soil Group—Washington County,Oregon I a (21684-Kuni BMW-Downstream Analysis HSG) N I516300 516400 516500 516600 516700 516900 516900 5170W 517100 51rcu 517300 517400 45°27 25"N _ i I j 45°27 25"N it xi Ili ,,,l' 10 1 '''';', n ,--"14'"- , 1 0 L 4,, l'4'.' - '.- 4 4 I HIw ! g 4� d'L .?a P a t ,,, 8 ,, , u a c 1 1 ,fro' 111611:, , . , ,,,, s,,.i I d II „..000,,,,"4,..:.,.. 21,225A:' '4.4 1104:11.1 A E ii.,i va p 0.41,1, c 11111, , I X f '" : '4111'.' I ' sit::,1,016.'4:::::e rli lt,::, x - 4 t Io ' '✓ 'zi ; , , ma • �,6q : ' ''' .iA6"g � t Ut -ti• J* o L - . 45°26'34"N i"' 45°26'34"N ' rA 516300 516400 516500 516600 516700 516800 516900 517000 517100 517200 51r,xU 517400 3 3 Fv Map Scale:1:7,610 if printed on A portrait(8.5"x 11")sheet. N 0 10 N Meters ° I 0 200 400 600 Feet0 0 350 700 1400 21 Map projection:Web Mercator Corner coordinates:WGS84 Edge tics:UTM Zone lON WGS84 II till+, Natural Resources Web Soil Survey 7/25/2021 III". Conservation Service National Cooperative Soil Survey Page 1 of 4 N 4- I N a) N N ° _c CO O'ca a) 2N O) N rpn .@ o U N CO cn 01) N `o n a_m � a) a) orf° d a��i 32 -o ` V1 a) CO 17 y N w co O C O U O O N 'O n N — Y a) nn rn ° E co--0 a) o o c) I Z o a m o o g u ai v CO c E m y r°n O Cl)E O fa E f0 t Z m e n '� 02 U cn o Q « y . c Cl) co E co N 3 w Cl) 0 ° c cv E Z � o E cov Q3 w w 60 o n N Ln 0 -o c0 ON 3 -o o C '> rL O a) n3 �' E U w comd ° m ❑ �� `0 -c 3 � 00 m corm ° aci r � c ° c=i, c° � c a) m cooQ � O o a) E cc) 2, m �' ° 10 c o y 3 ° � m o au'o > > l o o m m 7• E T ` o m O co T n E cn /� 0a) 7 c) 'o co a a) ii o C a) n 7 U o _n CD 'o 4- ) f/) u) N 0 92 N n a) C • o 43• m E no a) .n cal' ,aE < Bc a) co > o a) oYow, CCD Cr) CO w Z ❑ E (Da ' o m m E o)H w T r t m 2 .o c1 m 2 coo co a) E ° .CO m D ' T 2 O • N C . a m >. a) U co IC 7 N V d co O V ,, n Z o c c0 N T co 7 N w 3 c m •o o > cca o m voi E 7 In a) �, E rn E _ rn E p 7 c) 7 ` > kz 7 O ` ,E N 0 c, o o c0) C e E ° 'o c D O a) a) o a) Q c 00 „co O) _ O N C 'p c co N co ' U• cn '� y ° C N Ei 0- a) cn a) E O N O p .Q y c C O O o ° n N CO CO 7 O O-N ra a) 7 N .0 — Z - 0 w N a) E m 4 I m 0 L N W c '- C O U a) a) O a) O o O y 8 t w 5 7 O Ln cC Cs./ -C O E L a, = I- � W E — o u, a E c030 o o< o h o co cn cn - ❑ — f- o ._ u O , c( aa)) I U• C ) c 7 c Q O E To 0 C coi j IIco a) o o2 T U o S E n 7 co oc c0 VcC Ct v a = -0mop.0 mOO o a Cl) ° o o Z .� o E m o a w a ov E m u � c2 `o m ° O O a) O c m a' cn cop U U O Z in O Q j J ,O Q > o N C 0 N z ® ® .w 2 ca 1 1 rn I O m m 03 w to d m m I Q ° m m O G O ,I Q o m m0 c H m a° o a ❑ ❑ ❑ ❑ 0 ❑ o ° ❑ ❑ tntQ a m m c) c) o Z onQ a m 'm c..) 3o z mQ a co m CC c c c a) irlin E _ 5 cf) V) co3 N I p C ToU gl j it IHydrologic Soil Group—Washington County,Oregon 21684-Kuni BMW-Downstream Analysis-HSG I Hydrologic Soil Group 1 IMap unit symbol Map unit name Rating Acres in AOI Percent of AO1 1 Aloha silt loam C/D 96.5 66.1% i 13 Cove silty clay loam D 16.7 11.4% 45A Woodburn silt loam,0 to C 0.2 0.2% 3 percent slopes I 45B Woodburn silt loam,3 to C 20.4 14.0% 7 percent slopes 2027A Verboort silty clay loam, D 0.1 0.1% I 0 to 3 percent slopes 2225A Huberly silt loam,0 to 3 C/D 12.0 8.2% percent slopes ITotals for Area of Interest 146.0 100.0% I I I I I I I I IUSDA Natural Resources Web Soil Survey 7/25/2021 7111. Conservation Service National Cooperative Soil Survey Page 3 of 4 I IHydrologic Soil Group—Washington County,Oregon 21684-Kuni BMW-Downstream Analysis-HSG I Description I Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the I soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. I The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (ND, B/D, and C/D). The groups are defined as follows: I Group A. Soils having a high infiltration rate (low runoff potential)when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. IGroup B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well I drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist I chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. IGroup D. Soils having a very slow infiltration rate (high runoff potential)when thoroughly wet. These consist chiefly of clays that have a high shrink-swell I potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. I If a soil is assigned to a dual hydrologic group (ND, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. I Rating Options I Aggregation Method: Dominant Condition Component Percent Cutoff. None Specified Tie-break Rule: Higher I I l!5i)n Natural Resources Web Soil Survey 7/25/2021 mg. Conservation Service National Cooperative Soil Survey Page 4 of 4 I I 4*j PIPE FLOW CALCULATIONS I PROJECT NAME BMW of Tigard BY: PJP DATE: 10/19/2021 IPROJECT NO. 21684 Note: This calculation was performed to estimate the flow within the 42" CMP culvert crossing OR 217 Hwy. IEstimation of Peak Flow for 36" Pipe Input Description Value I y depth of flow 3.29 ft do depth of flow section 3.50 ft, 0 S pipe slope 0.005 ft/ft n manning's coefficient 0.013 Output Description Value X ratio of y/do(max flow at 0.94) 0.940 A flow area 9.39 ft2 P wetted perimeter 9.26 ft R hydraulic radius 1.01 ft T top width 1.66 ft D hydraulic depth 5.65 ft Q flow 76.5 cfs IV flow velocity 8.2 ft/s Note: Typically, CMP has a n of 0.024;however, 0.013 was used for conservativeness. I I I I I I I I I 3J CONSULTING Downstream Analysis -XPSTORM Hydraulic Layout Y Y Y • 1 1 MH1 MH2 • 1 CSC UlS 411 ct • 1 D1 U/S • 1 CDS 1 •I 2 US 1 1 i-; 1 • . 1 1 • � 1 1 1 1 C u1ta11 A • 1 3J' I - XPSTORM RUNOFF DATA- BMW OF TIGARD - DOWNSTREAM ANAYLSIS IPOST-DEVELOPED CONDITIONS Runoff Parameters (Input) 25-yr Storm Event 100-yr Storm Event Node I Name Area Impervious Curve Tc Precip Peak Precip Peak acre % Number min. in cfs in cfs Upstream 2.71 0 85.6 10 3.90 10.60 4.50 12.54 III 4.31 0 96.6 8 6.57 0 94.4 8 J1 0.07 100 98 5 3.90 0.25 4.50 0.31 I 0.33 0 84 5 J2 4.12 100 98 5 3.90 4.49 4.50 5.26 0.46 0 84 5 I0.37 0 91 5 0.33 0 84 5 J3 1.66 100 98 5 3.90 1.87 4.50 2.19 I0.18 0 84 5 0.12 0 91 5 I 0.28 0 84 5 J4 1.54 0 91 5 3.90 1.73 4.50 2.11 0.56 0 84 5 I _ 0.05 0 91 5 0.39 0 84 5 Site 3.06 100 98 5 3.90 3.06 4.50 3.57 I 0.46 0 _ 84 5 Outfall 0.13 0 91 5 3.90 0.47 4.50 0.59 0.67 0 84 5 I M H 1 0.29 100 98 5 3.90 0.29 4.50 0.34 0.04 0 84 5 OC U/S 2.33 100 98 15 3.90 3.09 4.50 3.71 I2.43 0 84 15 I I I I I I Page 1of1 1 0 tD ul <t in k.0 N CO CO r N 1 73 ul N O r, CO e- N (.0 O O Ci O Ci O Ci Ci o N O O > J _ _ _ O +�-+ m m V N 00 m m m ul I N N CO ul O � k0 COO C00 000 L.L Cl -+ N Cl 00 N N N e- _ 00 1/40 ul 77 00 O N n N 0 e- — N o 0 o N N N N IA N N N N N al CT) CT) COOl 00 00 2 0 1 _ _ __Im Ol m l0 CT) CO X N m CO m o0 O �O O N o LC) N N CO N L0 �0 00 �O LC) (..01 .4_, N v0 O o d- Ol k.0 e- Ol e- 00 o = O 00 u0 U'1 ul N Ol al ul 4 4 o0 4 m N ul O O N CT) n r, n co Ol al al a, O 00 00 .-i (n .5 1 U' ° 0 Q u LL ut 000 ,- oo umi N t.0 01 Ol k.0 O ° Qt CO al CT) I, o N 4- O N O N N m $+ tO '.0 Ol o t0 N lO 00 o e- e- e- Z " c`l o 0 0 cri o o cri °m° 4 rri csi �o 4 4 cri cri < Z 2 1 IQ > > c ~Z CO N 0rn � Oe- ulNo r, rn N CO N O N r, v C e- C Cr) m N O e- e- O N N a) N to '.O CS) e- N N. '.0 e- 00 O O I Z o QC00000 - 000000 N a 0a vmcril< - , � tOd V 171 1 _ C m m m Li, 00 m N 0 0 0 0 0 0 0 00 W 0 0 Q u1 b.0 * N O e- rn N Ln ul rn O LiJ o co CO m ul �o l7 N ( M - N W ul o ul L0 00 (ri u6 o lJ t ) I� ui O I: Oi N oo Oi un Ln w 0 — o N g N m 7r N N N N N N 00 01 O 00 CO CO 00 1— .. N Q U u) C N N N N e- N 0I O _ %-1! 0.0 2 0 N w O O o 0 0 t N 0 00 00 00 M m Z Cl N N 00 '.0 N ul 1,- N CO O 00 00 CO N O N d: m ul '.O m in ul d 1 O m 0 0 0 N 0 e- .- O e- 4N ` Ol IN N N ul O V �' O N 00 00 Q in D 00 n N. r, CO Ol 0') Ol CO CT) 00 00 Q 0 v W CU 1 Z O 0 -- `CC O O O O O O O O O O O O O O O o 0 o ul O O O o 0 > '�' O O O O O O o 0 0 0 0 0 L > N Ol N al N m co ul N o 0 0 >- W d c -'' N m V O o ul 00 m o o V� 0) 0 0 Oi N O N lO O m v3 . LLJ Q + tU CT) o N O Ol N VD N N N O ,D in W CO 00 I", N CO Ol al al Ol Ol Ol Ol > = J m N N ul m e- e- e- Q . . . . . . e- e- e- e- e- e- Z H 1 t4 C U O g a v v O O O o o N N u) 0 0 0 0 O O O O O O O m O m 0 0 i j m N Oi N O m o ul N N O �-+ ul 7 7 Ql oo O O 0o e- 00 O ul 0 a) , cNi O Ci Oi ' 00 r< kDO� Oi (ri cri 1 F- f� Q m u0 N l e- N e- e- o VI o m Ul W m 0-1 CO00 Ol Ol Ol Ol al Ql al al VI d X 1 (6 N tO N r/7 � V _- N N r- -' 7 -' -� 2 V U = N N 0 0 0 0 0 0 0 0 0 0 c c 0 0 rip �0 4, cc N N V1 V1 N C Nultn N VI VI O 0 Q ut Q VO OV O O LL 0 2 2 0 0 0 0 1 i N vl V V V J J 1 CT) O ill N 7T V0 Ol O o 0 0 01 0 in N 0 0 0 0 ,[ CO Ol Ol Ol O Ol Ol Cr) ,[ 00 6l Ol Ol Ol Ol Ol Ol C J C C_ C_ C C C C C C C J C_ C CC C_ _C C_ C_ E C C C J J J J J J J J J J J J J Ti J J J J J J J J J 1 1 -O tN N LU N O1 Ql Om d' LU N O7 I j, Ci Ci 0 0 0 Ci Ci Ci Ci c-Ni o 0 I In o .o m .D al an d to m m J +=4 m m ‘.0 .D m t11 m m Ln m N CO to O .0 ‘.0 .0 CO CO CO ' V V N r- Cl N N N _ 00 Li. t11 00 O 4 N 6 n X >< 0 e- N O O O N N N N Vl N N N N N Ol Ol 0") Ol CO CO y y 'J 0 M 0 i0 In Vl O 0") to M 7T CO O 0O to M N CO M N L0 CO L0 L0 0 ,� f0 0 Oi N 4 Ol o-, Om o CO co. h h 2 '' O CO .O to to N Ql Oi I z 2 N t!l 4 4 W 4 M M t!l o N a) NN N CO Oi Cl al 01 0) CO 00 > e- e- VI I til J O N k.0 O rn O QlN O O Ol VI N 0 d' .O N .0 N VD Vl N N .fl m rl O .0 .0 Ol 0 .O N .D CO O e- z U 1D o 0 0 cri o o v m m N e- .o 4 ri cri 0 Q 1_ 2 < w ct w C f�6 •- N CO N O 6l N N N e- .0 N O 'ct N O N N O to .O .O Z a. E o e- o m 'ct 0 e- e- O N N N ,V N .O .0 O'1 e- e- N LU e- 00 O O -� O O O O O �- O O O O O O Z. = N 4 m M I� ,- ,- 4 .O 4 4 O V1 Ni 0 ce w I Z.0 m o m t11 CO Ln m N C w 0 0 0 0 0 0 0 00 00 0 0 Q CD 00 u N r- CT) N to ul a- Ql e- O - n O CO e- CO ul m to .O O N .fl ul O Is) .0 CO M • .0 O V Vi Le n 4 O n Ol 4 Ni CO O� L.fl L.fl N a U — .O w 0 N 4 N m m 4 N 0 N N N N N CO al al CO CO CO CO N f- , 0 f6 t!1 t11 N N ,_ N ,} U V1 U O I O Z N O c00 21= O O O O O N O W a0 00 C mCo N o N v M to .o m t!1 t!1 N1 d N N co00 .0 N to N . CO00 .O CO00 CO I Q' O ri Ci O O N O e- e- Ci e- 4 CT; N to t!1 O 0) Oi fV CO o N N I� co rn rn rn Co Cl Co C000 F- U O .a w d N ' z 0 Q 0 0 0 0 0 0 0 0 00 0 0 0 00 0 0 0 0 0 a W � •' 000000000 0 0 0 i j N Ol N Ol N m r1 tf1 0 0 0 >- > a C Nrl v • oa .rioocrioo l7 (1) . 000inioN .oaim .D w w r> 0 _+ aJ m O N o Cl N N N N V1 W 00 CO N N CO Ol al Ol Ol 0) m N N Lfl M e- e- e- e- e- e- e- . . . . . . . e- J 0 I O /1 C a u '- a o o O o o N N t!1 0 0 0 0 v �j O O O O O O O m O m 0 0 i j m N Cl N o 4 m o t!1 N N O E in 7 7 rn 00 O o W e- 00 O ul 0 NU N 6 Ci of DO N: .D .D Ci ri m I- N M to e- N e- e- o t!l O M M v, W 0-, CO co N� O1 Ol o-) Ol Ol Ol CT) a Q e- e- •X I = - to U) l/1 l/1 to to DD -' -. D N, 2 U 0 - N N ,� e-IO t. 2 2 U ? N N 0 0 0 0 0 0 0 0 0 0 C C I 47, 044.4 0 0 N E N N � l/1 l/1 o E N N N l/�1 In l!1 CO 0 N P V 2 ,-. = 2 2 2 0 0 0 a N M 2 2 2 0 0 I VO 0 Q D U U J ti 0 Vl 0 0 U U I O VI N .O CT) O O O O CT) O t!l N .0 O� O O O CI,[ CO00 CT) 01 Ol O) O) O) Y CO Ol 0 . ) 0) C) 0) 01 OCT)_J C C C .0 •C •C •C .0 CCCC _I .0 .0 .0 .0 .0 .0 C .0 CCCC J J J J J J J J J J = J J J J J J J J J J J J J 1 I OPERATIONS & MAINTENANCE ' PLAN ♦J' 1 OPERATIONS & MAINTENANCE PLAN FOR STORMWATE R FACILITIES At: BMW of Tigard ' 10031 SW Cascade Avenue Tigard, OR 97223 ' June 14,2022 Prepared For: Holman Automotive Group 911 NE 2nd Avenue Fort Lauderdale, FL 33304 Prepared By: ' 31 Consulting,Inc. 9600 SW Nimbus Avenue,Suite 100 Beaverton,Oregon 97008 ' Project No:21684 PIP PURPOSE The purpose of this Operations & Maintenance (O&M) Plan is to bringattention to the on-going needs p p p g g of the stormwater management facilities located at the BMW of Tigard in Tigard, OR. For the stormwater management facilities to operate as intended and increase the environmental benefits, a high-quality maintenance program is required. This document has been prepared to provide the owner with a single source document that will explain the maintenance requirements of the proposed onsite stormwater management facilities. The owner of this property will be the fiscally responsible party for operating and maintaining the stormwater maintenance facilities. STORMWATER MANAGEMENT FACILITIES There are seven (7) stormwater management facilities, requiring ongoing inspection & maintenance, described as follows: • Two(2)Contech StormFilter Manholes are proposed onsite. Per the Construction Drawings,structures "SDMH 02"and "SDMH 04"are both equipped with five (5) cartridges (18" height), respectively. • One(1) Contech StormFilter Catch Basin is proposed onsite. Per the Construction Drawings, structure "SDCB 01" is equipped with one (1) 27"treatment cartridge. • Two (2) Pretreatment Manholes ("SDMH 03"and "SDMH 05") are proposed upstream of the detention facility. • The Contech CMP Detention Facility, consisting of 48" diameter corrugated metal pipes (CMP) surrounded by drain rock detains flows on the property. • One (1) Flow Control Manhole ("SDMH 01") is proposed downstream of the detention facility. All facilities above were designed per the City of Tigard and Clean Water Services (CWS) Standards. Please refer to the Construction Drawings and the Stormwater Report for more information pertaining the facilities described above. INSPECTION & MAINTENANCE SCHEDULE Each part of the system shall be inspected and maintained quarterly for the first 2 years of operation and twice a year thereafter. Additionally, each facility shall be inspected within 48 hours after each major storm event. For this O&M plan, a major storm event is defined as 1.0-inch of rain or greater falling in 24 hours. All components of the storm system as described above must be inspected and maintained frequently or they will cease to function effectively.The Owner shall keep a log, recording all inspection dates, observations, and maintenance activities. Receipts shall be saved when maintenance is performed and there is a record of expense. 1 I 1 of 3 Contech StormFilter Manholes & Catch Basin I • Manholes - Maintenance should be performed per attached Contech StormFilter Operations & Maintenance Manual - Manholes &Vaults. • Catch Basin - Maintenance should be performed per attached Contech CatchBasin StormFilter IOperations & Maintenance Manual. Maintenance Schedule: 1 I • Annual inspections are required. • It is recommended that each StormFilter be inspected every six(6) months when first installed. I Pretreatment & Flow Control Manholes • Remove sediment, oil, and debris when they are more than half full or when the sediment is within 18 inches of the bottom of the outlet pipe. I • Remove debris and sediment. Maintenance Schedule: • Summer: Make any structural repairs. Remove sediment, oil and debris from conveyance system I and manholes. • Winter: Monitor water levels and sediment level. IUnderground Detention Facilities (Contech CMP Detention Facility) I • Inspect sediment level in underground storage facility via riser(inspection port). Using a flashlight and stadia rod, measure depth of sediment and record results on maintenance log. If sediment is at or above 3", clean out storage with JetVac (or city-approved equivalent) process. I • Inspect manholes and catch basins upstream and downstream of detention facility to ensure drainage. Remove sediment and debris from structures, as needed. • Flow control -All facilities must drain within 48 hours. Record time/date,weather and conditions when I ponding occurs. Maintenance Schedule: • Annual inspections are required. I • It is recommended that each underground detention facility be inspected every six(6) months for the first year of operation. For subsequent years,the inspection should be adjusted based upon previous observation of sediment deposition. IMaintenance Records All facility operators must keep an inspection and maintenance log (see Elements). Record date, description I and contractor (if applicable) for all repairs, landscaped maintenance and facility cleanout activities. Keep work orders and invoices on file. IAccess Maintain ingress/egress per design standards. IPollution Prevention All sites shall implement best management practices to prevent hazardous wastes, litter, or excessive oil and I sediment from contaminating stormwater. Contact Clean Water Services' 24-hour response line at 503-681- 3600 for general questions about stormwater pollution or if you witness a problem that is an immediate threat to public health or property. Record time/date/weather, location of spill, any corrective action that has been Itaken, and site conditions if site activities are found to contaminate stormwater. 2 of 3 Vector Control 1 Stormwater facilities must not harbor mosquito larvae or rodents that pose a threat to public health or that undermine facility structures. Record the time/date, weather and site conditions when vector activity observed. Record when vector abatement started and ended. ELEMENTS This document contains the following information. 1. Maintenance Contact List 2. Sample Maintenance Logs 3. Construction Drawings 4. Contech StormFilter O&M Manual - Manholes &Vaults 5. Contech CatchBasin StormFilter O&M Manual 6. Private Stormwater Facilities Agreement I 1 I 3 of 3 1 I MAINTENANCE CONTACT LIST IOwner's Name: Holman Automotive Group Contact Person: Steve Presson Phone No.: I Owner's Mailing Address I Holman Automotive Group 911 NE 2nd Avenue Fort Lauderdale, FL 33304 iSite Address: BMW of Tigard 10031 SW Cascade Avenue ITigard, OR 97223 Site Legal Description or Tax Lot(s): III 1 S127DD01200 IParty/Parties responsible for maintenance (only if different than owner). I Contact Name: Address: Company: Phone No.: ( ) IEmergency/After-Hours Contact Phone No. ( ) IEmergency/Afterhours Contact: Phone No.: ( ) I I I I I I 1 III SAMPLE MAINTENANCE LOGS Year: Facility: , Notes Initial & Date Maintenance Item January February March ' April ' May June July August ' September I October I November December I I 1 C=.. NTECH ENGINEERED SOLUTIONS 1 StormFilter Inspection and Maintenance Procedures 44, • • ti. " o1J � 2 c 5. The Stormwater Management StormFilter Maintenance Guidelines In addition to these two activities, it is important to check The primary purpose of the Stormwater Management the condition of the StormFilter unit after major storms for StormFilter®is to filter and prevent pollutants from entering our potential damage caused by high flows and for high sediment accumulation that may be caused by localized erosion in the waterways. Like any effective filtration system, periodically these drainage area. It may be necessary to adjust the inspection/ pollutants must be removed to restore the StormFilter to its full maintenance schedule depending on the actual operating efficiency and effectiveness. conditions encountered by the system. In general, inspection Maintenance requirements and frequency are dependent on the activities can be conducted at any time, and maintenance should pollutant load characteristics of each site. Maintenance activities occur, if warranted, during dryer months in late summer to early may be required in the event of a chemical spill or due to fall. excessive sediment loading from site erosion or extreme storms. It is a good practice to inspect the system after major storm events. Maintenance Frequency The primary factor for determining frequency of maintenance for Maintenance Procedures the StormFilter is sediment loading. Although there are many effective maintenance options,we A properly functioning system will remove solids from water by believe the following procedure to be efficient, using common trapping particulates in the porous structure of the filter media equipment and existing maintenance protocols.The following inside the cartridges.The flow through the system will naturally two-step procedure is recommended:: decrease as more and more particulates are trapped. Eventually 1. Inspection the flow through the cartridges will be low enough to require • Inspection of the vault interior to determine the need for replacement. It may be possible to extend the usable span of the maintenance. cartridges by removing sediment from upstream trapping devices on a routine as-needed basis, in order to prevent material from 2. Maintenance being re-suspended and discharged to the StormFilter treatment • Cartridge replacement system. • Sediment removal The average maintenance lifecycle is approximately 1-5 years. Inspection and Maintenance Timing Site conditions greatly influence maintenance requirements. At least one scheduled inspection should take place per year with StormFilter units located in areas with erosion or active maintenance following as warranted. construction may need to be inspected and maintained more often than those with fully stabilized surface conditions. First, an inspection should be done before the winter season. During the inspection the need for maintenance should be Regulatory requirements or a chemical spill can shift maintenance determined and, if disposal during maintenance will be required, timing as well.The maintenance frequency may be adjusted as samples of the accumulated sediments and media should be additional monitoring information becomes available during the obtained. inspection program.Areas that develop known problems should be inspected more frequently than areas that demonstrate no Second, if warranted, a maintenance(replacement of the filter problems, particularly after major storms. Ultimately, inspection ' cartridges and removal of accumulated sediments)should be and maintenance activities should be scheduled based on the performed during periods of dry weather. historic records and characteristics of an individual StormFilter system or site. It is recommended that the site owner develop a database to properly manage StormFilter inspection and maintenance programs.. 7 6- I I • f 1t +.L 111 H , Maintenance Decision Tree .. � The need for maintenance is typically based on results of the I a � '4, YP Y, `A �> inspection. The following Maintenance Decision Tree should be used as a general guide.(Other factors,such as Regulatory Requirements,may need to be considered) ��" � � A"�$>7.;;;." ,. er y, s 1. Sediment loading on the vault floor. ^�"`` ,"42. { 4` , , a. If >4" of accumulated sediment, maintenance is r ve _ q ,!„ !ate >t. ,, required. 2. Sediment loading on top of the cartridge. ,._ a. If >1/4" of accumulation, maintenance is required. I 3. Submerged cartridges. a. If >4" of static water above cartridge bottom for more 5^ • ' . than 24 hours after end of rain event, maintenance it ..4 ;+ . is required. (Catch basins have standing water in the ' *< �� � � ^' cartridge bay.) Inspection Procedures I 4. Plugged media. The primary goal of an inspection is to assess the condition of a. If pore space between media granules is absent, the cartridges relative to the level of visual sediment loading as maintenance is required. it relates to decreased treatment capacity. It may be desirable to I conduct this inspection during a storm to observe the relative 5. Bypass condition. flow through the filter cartridges. If the submerged cartridges a. If inspection is conducted during an average rain fall are severely plugged,then typically large amounts of sediments event and StormFilter remains in bypass condition I will be present and very little flow will be discharged from the (water over the internal outlet baffle wall or submerged drainage pipes. If this is the case, then maintenance is warranted cartridges), maintenance is required. and the cartridges need to be replaced. 6. Hazardous material release. I Warning: In the case of a spill,the worker should abort a. If hazardous material release(automotive fluids or other) inspection activities until the proper guidance is obtained. is reported, maintenance is required. Notify the local hazard control agency and Contech Engineered I Solutions immediately. 7. Pronounced scum line. a. If pronounced scum line(say >_ 1/4"thick) is present To conduct an inspection: above top cap, maintenance is required. Important: Inspection should be performed by a person Iwho is familiar with the operation and configuration of the StormFilter treatment unit. I1. If applicable, set up safety equipment to protect and notify surrounding vehicle and pedestrian traffic. 2. Visually inspect the external condition of the unit and take !a notes concerning defects/problems. v I 3. Open the access portals to the vault and allow the system ' vent. I 4. Without entering the vault,visually inspect the inside of the - unit, and note accumulations of liquids and solids. 5. Be sure to record the level of sediment build-up on the floor 4 of the vault, in the forebay, and on top of the cartridges. If •ii I flow is occurring, note the flow of water per drainage pipe. Record all observations. Digital pictures are valuable for historical documentation. ' 6. Close and fasten the access portals. 7. Remove safety equipment. . 8. If appropriate, make notes about the local drainage area tir 1 I relative to ongoing construction, erosion problems, or high loading of other materials to the system. 9. Discuss conditions that suggest maintenance and make i ' decision as to whether or not maintenance is needed. Maintenance Depending on the configuration of the particular system, .p.i ; maintenance personnel will be required to enter the vault to - ,,.. I perform the maintenance. - . ..... ` �r! Important: If vault entry is required, OSHA rules for confined �,; space entry must be followed. � � + �t ��i � Filter cartridge replacement should occur during dry weather. ._ h" } 1 # y It may be necessary to plug the filter inlet pipe if base flows is _wi occurring. r k I I Replacement cartridges can be delivered to the site or customers a facility. Information concerning how to obtain the replacement cartridges is available from Contech Engineered Solutions. — I Warning: In the case of a spill,the maintenance personnel `� ,. _± b 'r , • should abort maintenance activities until the proper guidance ,', ;....4*.,...y' ' u.� t }; ` I is obtained. Notifythe local hazard control agency and *"' va,r,,,,, , s ''£ 9 Y v s u iini/i��if �fa. .. _ ,. Contech Engineered Solutions immediately. ,& _ ., r%�, 1 To conduct cartridge replacement and sediment removal ,-,c-- _ , A.(' ., ? h / I maintenance: ... , ._ ..„......_ 1. If applicable, set up safety equipment to protect maintenance ",� ,,1111-4 '__.....^"` - .. ! ,,, personnel and pedestrians from site hazards. ;',, I 2. Visually inspect the external condition of the unit and take notes concerning defects/problems. 3. Open the doors(access portals)to the vault and allow the y system to vent. 4. Without entering the vault, give the inside of the unit, Important: Care must be used to avoid damaging the I including components, a general condition inspection. cartridges during removal and installation.The cost of 5. Make notes about the external and internal condition of repairing components damaged during maintenance will be the vault. Give particular attention to recording the level of the responsibility of the owner. sediment build-up on the floor of the vault, in the forebay, C. Set the used cartridge aside or load onto the hauling I and on top of the internal components. truck. 6. Using appropriate equipment offload the replacement cartridges(up to 150 lbs. each)and set aside. D. Continue steps a through c until all cartridges have been I 7. Remove used cartridges from the vault using one of the removed. following methods: Method 2: Method 1: A. This activity will require that maintenance personnel enter I A. This activity will require that maintenance personnel enter the vault to remove the cartridges from the under drain the vault to remove the cartridges from the under drain manifold and place them under the vault opening for manifold and place them under the vault opening for lifting (removal). Disconnect each filter cartridge from the lifting (removal). Disconnect each filter cartridge from the underdrain connector by rotating counterclockwise 1/4 of underdrain connector by rotating counterclockwise 1/4 of a turn. Roll the loose cartridge, on edge, to a convenient a turn. Roll the loose cartridge, on edge,to a convenient spot beneath the vault access. I spot beneath the vault access. B. Unscrew the cartridge cap. Using appropriate hoisting equipment, attach a cable C. Remove the cartridge hood and float. I from the boom, crane, or tripod to the loose cartridge. Contact Contech Engineered Solutions for suggested D. At location under structure access, tip the cartridge on its attachment devices. side. B. Remove the used cartridges(up to 250 lbs. each)from the E. Empty the cartridge onto the vault floor. Reassemble the I vault. empty cartridge. F. Set the empty, used cartridge aside or load onto the I hauling truck. G. Continue steps a through e until all cartridges have been removed. I n 8. Remove accumulated sediment from the floor of.the Material Disposal vault and from the forebay.This can most effectively be The accumulated sediment found in stormwater treatment I accomplished by use of a vacuum truck. and conveyance systems must be handled and disposed of in 9. Once the sediments are removed, assess the condition of the accordance with regulatory protocols. It is possible for sediments vault and the condition of the connectors. to contain measurable concentrations of heavy metals and I10.Using the vacuum truck boom, crane, or tripod, lower and organic chemicals(such as pesticides and petroleum products). install the new cartridges. Once again, take care not to Areas with the greatest potential for high pollutant loading damage connections. include industrial areas and heavily traveled roads. Ii 1.Close and fasten the door. Sediments and water must be disposed of in accordance with 12.Remove safety equipment. all applicable waste disposal regulations. When scheduling 13.Finally, dispose of the accumulated materials in accordance maintenance, consideration must be made for the disposal of I with applicable regulations. Make arrangements to return the solid and liquid wastes.This typically requires coordination with used empty cartridges to Contech Engineered Solutions. a local landfill for solid waste disposal. For liquid waste disposal a number of options are available including a municipal vacuum truck decant facility, local waste water treatment plant or on-site I treatment and discharge. Related Maintenance Activities - Performed on an as-needed basis StormFilter units are often just one of many structures in a more ' comprehensive stormwater drainage and treatment system. �" I In order for maintenance of the StormFilter to be successful, it is imperative that all other components be properly maintained. (( ' The maintenance/repair of upstream facilities should be carried P III out prior to StormFilter maintenance activities. , In addition to considering upstream facilities, it is also important ii Ito correct any problems identified in the drainage area. Drainage area concerns may include: erosion problems, heavy oil loading, k and discharges of inappropriate materials. ` m xi ,11111tlttglt►,. +. attar. moil I I I (;; rm I ', `1 t gam, .: Y4�t lii , `'� / 1 w, G Inspection Report Date: Personnel: Location: System Size: Months in Service: System Type: Vault _ Cast-In-Place Linear Catch Basin Manhole Other: ' Sediment Thickness in Forebay: Date: Sediment Depth on Vault Floor: t Sediment Depth on Cartridge Top(s): Structural Damage: ' Estimated Flow from Drainage Pipes(if available): Cartridges Submerged: Yes No I Depth of Standing Water: StormFilter Maintenance Activities(check off if done and give description) Trash and Debris Removal: Minor Structural Repairs: I Drainage Area Report Excessive Oil Loading: Yes — No Source: Sediment Accumulation on Pavement: Yes No I I Source: Erosion of Landscaped Areas: Yes I No Source: Items Needing Further Work: Owners should contact the local public works department and inquire about how the department disposes of their street waste residuals. Other Comments: - 1 1 Review the condition reports from the previous inspection visits. IStormFilter Maintenance Report IDate: Personnel: Location: System Size:I System Type: Vault Cast-In-Place Linear Catch Basin 1 1 Manhole 1 Other: List Safety Procedures and Equipment Used: I System Observations I Months in Service: Oil in Forebay(if present): Yes No I Sediment Depth in Forebay(if present): Sediment Depth on Vault Floor: I Sediment Depth on Cartridge Top(s): Structural Damage: I Drainage Area Report Excessive Oil Loading: Yes No Source: I Sediment Accumulation on Pavement: Yes — No Source: Erosion of Landscaped Areas: Yes No Source: IStormFilter Cartridge Replacement Maintenance Activities I Remove Trash and Debris: Yes No Details: Replace Cartridges: Yes No Details: Sediment Removed: Yes No Details: I Quantity of Sediment Removed (estimate?): Minor Structural Repairs: Yes No Details: IResiduals(debris, sediment) Disposal Methods: Notes: I Z RECYCLED '"`w..•,,�®�`' PAPER CtitNTECH• ENGINEERED SOLUTIONS © 2020 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY 800-338-1122 www.ContechES.com , All Rights Reserved. Printed in the USA. Contech Engineered Solutions LLC provides site solutions for the civil engineering industry. Contech's portfolio includes bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other Contech division offerings,visit www.ContechES.com or call 800.338.1 122. Support • Drawings and specifications are available at www.conteches.com. • Site-specific design support is available from our engineers. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY.APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS,AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION,CONTECH MAKES NO WARRANTY WHATSOEVER,EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS,MATERIALS,COATINGS,OR PRODUCTS DISCUSSED HEREIN.ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH'S CONDITIONS OF SALE(AVAILABLE AT WWW.CONTECHES.COM/COS)FOR MORE INFORMATION. 800.338.1122 StormFilter Inspection and Maintenance Procedures 3/20 www.conteches.com I ICONTECH® OPERATION AND ENGINEERED SOLUTIONS MAINTENANCE ICatchBasin StormFilterTM Important: These guidelines should be used as a part of your site 'stormwater plan. I Overview The CatchBasin StormFilter'' (CBSF) consists of a multi-chamber Once in the cartridge chamber, polluted water ponds and steel, concrete, or plastic catch basin unit that can contain up to percolates horizontally through the media in the filter cartridges. four StormFilter cartridges. The steel CBSF is offered both as a Treated water collects in the cartridge's center tube from where it 'standard and as a deep unit. is directed by an under-drain manifold to the outlet pipe on the downstream side of the overflow weir and discharged. 'The CBSF is installed flush with the finished grade and is applicable for both constrained lot and retrofit applications. It When flows into the CBSF exceed the water quality design can also be fitted with an inlet pipe for roof leaders or similar value, excess water spills over the overflow weir, bypassing the 'applications. cartridge bay, and discharges to the outlet pipe. The CBSF unit treats peak water quality design flows up to 0.13 Applications Icfs, coupled with an internal weir overflow capacity of 1.0 cfs for The CBSF is particularly useful where small flows are being the standard unit, and 1.8 cfs for the deep steel and concrete treated or for sites that are flat and have little available hydraulic units. Plastic units have an internal weir overflow capacity of 0.5 head to spare. The unit is ideal for applications in which I cfs. standard catch basins are to be used. Both water quality and catchment issues can be resolved with the use of the CBSF. 'Design Operation The CBSF is installed as the primary receiver of runoff, similar Retro-Fit to a standard, grated catch basin. The steel and concrete CBSF The retrofit market has many possible applications for the CBSF. units have an H-20 rated,traffic bearing lid that allows the filter The CBSF can be installed by replacing an existing catch basin 'to be installed in parking lots, and for all practical purposes, without having to "chase the grade,"thus reducing the high cost takes up no land area. Plastic units can be used in landscaped of re piping the storm system. 'areas and for other non-traffic-bearing applications. The CBSF consists of a sumped inlet chamber and a cartridge Ichamber(s). Runoff enters the sumped inlet chamber either by sheet flow from a paved surface or from an inlet pipe discharging directly to the unit vault. The inlet chamber is Iequipped with an internal baffle, which traps debris and floating oil and grease, and an overflow weir. While in the inlet chamber, heavier solids are allowed to settle into the deep sump,while 'lighter solids and soluble pollutants are directed under the baffle and into the cartridge chamber through a port between the baffle and the overflow weir. I I fiy Page 1 I U 1(1 C2 ALlH K1 6 Il D F Ir' ��+I $ www.ContechES.com/stormwater 800-338-1122 Stormwater Solutions from Contech' ©2013 Contech Engineered Solutions CC%0NTECH. OPERATION ANDI ENGINEERED SOLUTIONS MAINTENANCE • CatchBasin StormFilterTM Maintenance Guidelines Mosquito Abatement Maintenance procedures for typical catch basins can be applied yp pp In certain areas of the United t S ates, mosquito abatement is to the CatchBasin StormFilter (CBSF). The filter cartridges desirable to reduce the incidence of vectors. contained in the CBSF are easily removed and replaced during maintenance activities accordingto the followingguidelines. In BMPs with standing water, which could provide mosquito 9 breeding habitat, certain abatement measures can be taken. 1. Establish a safe working area as per typical catch basin service activity. 1. Periodic observation of the standing water to determine if the facility is harboring mosquito larvae. 2. Remove steel grate and diamond plate cover (weight 100 lbs. each). 2. Regular catch basin maintenance. 3. Turn cartridge(s) counter-clockwise to disconnect from pipe 3. Use of larvicides containing Bacillus thuringiensis israelensis manifold. (BTI). BTI is a bacterium toxic to mosquito and black fly larvae. 4. Remove 4" center cap from cartridge and replace with lifting cap. In some cases,the presence of petroleum hydrocarbons may interrupt the mosquito growth cycle. 5. Remove cartridge(s) from catch basin by hand or with vactor truck boom. 6. Remove accumulated sediment via vactor truck (min. Using Larvicides in the CatthBasin StormFilter clearance 13"x 24"). Larvicides should be used according to manufacturer's recommendations. 7. Remove accumulated sediment from cartridge bay. (min. clearance 9.25"x 1 1"). Two widely available products are Mosquito Dunks and Summit B.t.i. Briquets. For more information, visit http://www. 8. Rinse interior of both bays and vactor remaining water and summitchemical.com/mos ctrl/d efault.htm. sediment. The larvicide must be in contact with the permanent pool. The 9. Install fresh cartridge(s) threading clockwise to pipe larvicide should also be fastened to the CatchBasin StormFilter manifold. by string or wire to prevent displacement by high flows. A 10. Replace cover and grate. magnet can be used with a steel catch basin. ' 1 1. Return original cartridges to Contech for cleaning. For more information on mosquito abatement in stormwater Media may be removed from the filter cartridges using the BMPs, refer to the following: http://www.ucmrp.ucdavis.edu/ vactor truck before the cartridges are removed from the catch publications/managingmosquitoesstormwater8125.pdf basin structure. Empty cartridges can be easily removed from the catch basin structure by hand. Empty cartridges should be reassembled and returned to Contech as appropriate. Materials required include a lifting cap, vactor truck and fresh filter cartridges. Contact Contech for specifications and I availability of the lifting cap. The vactor truck must be equipped with a hose capable of reaching areas of restricted clearance. the owner may refresh spent cartridges. Refreshed cartridges are also available from Contech on an exchange basis. Contact the maintenance department of Contech at 503-258-3157 for more information. Maintenance is estimated at 26 minutes of site time. For units with more than one cartridge, add approximately 5 minutes for each additional cartridge. Add travel time as required. , Page 2 T.'P i" URBANGREEN `''' www.ContechES.com/stormwater 800-338-1122 Stormwater Solutions from Contech' ©2013 Contech Engineered Solutions After Recording Return to: ' Clean Water Services 2550 SW Hillsboro Hwy. Hillsboro,OR 97123 I PRIVATE STORMWATER FACILITIES AGREEMENT ' This Agreement is made and entered into this 14 day of June 20 22,by and between Clean Water Services (District)and Holman Automotive Group(Owner)whose address is 10031 SW Cascade Ave, Tigard, OR, 97223. RECITALS A. Owner has developed or will develop the Facilities listed below. (List the type of private stormwater facilities on site and the quantity of each type). ' Facility type(list each) Pretreatment Manhole Quantity 2 ea Contect StormFilter Manhole 2 ea Contech StormFilter Catch Basin 1 ea ' Contech CMP Detention Facility 7,884 sf(approx.) Flow Control Manhole 1 ea B. The Facilities enable development of property while mitigating the impacts of additional surface water and pollutants associated with stormwater runoff prior to discharge from the property to the public stormwater system. The consideration for this Agreement is connection to the public stormwater system. ' C. The property benefited by the Facilities and subject to the obligation of this Agreement is described below or in Exhibit A(Property)attached hereto and incorporated by reference. See attached. D. The Facilities are designed by a registered professional engineer to accommodate the anticipated volume of runoff ' and to detain and treat runoff in accordance with District's Design and Construction Standards. E. Failure to inspect and maintain the Facilities can result in an unacceptable impact to the public stormwater system. 1 ' Page 1 of 3—Private Stormwater Facility Agreement 88 Low Impact Development Approaches Handbook CleanWate Services NOW,THEREFORE,it is agreed by and between the parties as follows: 1. OWNER INSPECTIONS District shall provide Owner an Operations and Maintenance Plan(O&M Plan)for , each Facility. Owner agrees to operate,inspect and maintain each Facility in accordance with the current O&M Plan and any subsequent modifications to the Plan. Owner shall maintain a log of inspection activities. The log shall be available to District upon request or during District inspections. ' 2. DEFICIENCIES All aspects in which the Facilities fail to satisfy the O&M Plan shall be noted as "Deficiencies". 3. OWNER CORRECTIONS All Deficiencies shall be corrected at Owner's expense within thirty(30)days after completion of the inspection. If more than 30 days is reasonably needed to correct a Deficiency,Owner shall have a reasonable period to correct the Deficiency so long as the correction is commenced within the 30-day period and is diligently prosecuted to completion. 4. DISTRICT INSPECTIONS Owner grants District the right to inspect the Facilities. District will endeavor to give ten(10)days prior written notice to Owner,except that no notice shall be required in case of an emergency. District shall determine whether Deficiencies need to be corrected. Owner(at the address provided in this Agreement, or such other address as Owner may designate in writing to District)will be notified in writing through the US Mail of the Deficiencies and shall make corrections within 30 days of the date of the notice. 5. DISTRICT CORRECTIONS If correction of all Owner or District identified Deficiencies is not completed within thirty(30)days after Owner's inspection or District notice,District shall have the right to have any Deficiencies corrected. District(i)shall have access to the Facilities for the purpose of correcting such Deficiencies and(ii) shall bill Owner for all costs reasonably incurred by District for work performed to correct the Deficiencies(District Correction Costs)following Owner's failure to correct any Deficiencies in the Facilities.Owner shall pay District the District Correction Costs within thirty(30)days of the date of the invoice. Owner understands and agrees that upon non-payment,District Correction Costs shall be secured by a lien on the Property for the District Correction Cost amount plus interest and penalties. 6. EMERGENCY MEASURES If at any time District reasonably determines that the Facilities create any imminent threat to public health,safety or welfare,District may immediately and without prior notice to Owner take measures reasonably designed to remedy the threat. District shall provide notice of the threat and the measures taken to Owner as soon as reasonably practicable,and charge Owner for the cost of these corrective measures. 7. FORCE AND EFFECT This Agreement has the same force and effect as any deed covenant running with the land and shall benefit and bind all owners of the Property present and future, and their heirs,successors and assigns. 8. AMENDMENTS The terms of this Agreement may be amended only by mutual agreement of the parties.Any amendments shall be in writing, shall refer specifically to this Agreement,and shall be valid only when executed by the owners of the Property,District and recorded in the Official Records of the county where the Property is located. 9. PREVAILING PARTY In any action brought by either party to enforce the terms of this Agreement,the prevailing party shall be entitled to recover all costs,including reasonable attorney's fees as may be determined by the court having jurisdiction,including any appeal. 10. SEVERABILITY The invalidity of any section,clause, sentence, or provision of this Agreement shall not affect , the validity of any other part of this Agreement,which can be given effect without such invalid part or parts. 1 Page 2 of 3—Private Stormwater Facility Agreement , CleanWatcrr Services Low Impact Development Approaches Handbook 89 I IN WITNESS WHEREOF,Owner and District have signed this Agreement. INOTARIZE DOCUMENT BELOW I INDIVIDUAL OWNERS SIGN BELOW CORPORATE,LLC,PARTNERSHIP,TRUST OR OTHER LEGAL ENTITY SIGN BELOW Owner(Individual) Holman Automotive Group (Entity name) I Owner(Individual) By: (Sign here for entity) I Title: i CLEAN WATER SERVICES APPROVED AS TO FORM By:IGeneral Manager or Designee District Counsel I [Use this notary block if OWNER is an individual.] STATE OF ) ) County of ) I This instrument was acknowledged before me this day of ,20 , by INotary Public I [Use this notary block if OWNER is an entity.] ISTATE OF ) ) County of ) This instrument was acknowledged before me on (date) I by (name of person) as (title) of (name of entity). Notary Public I Page 3 of 3 Private Stormwater Facility Agreement 90 Low Impact Development Approaches Handbook Cleanwater��Services I / I 7\ /.' I 5���� �4144, 1 ZG�OV a So \ / S • i . ; , . i .' PROP BLDG ��1-7Ss 400;00,„ilk _ ro ___ . .___., ,! SD k-----:-.,, ,.. il. ..:-.117N PTMH r Ii� \\t � \ \ SFMH Il:lm Ji) i *% '` 1 ■I I ' -nee `� ,,, _ - I : I, a �� U .❖., ems__ ti1fr •: ci .•:. re PROPOSED BUILDING St IcL 1 1 •.• I L� CONTECH CMP ..4 DETENTIONI v I .. ►••••, I I Ir. 1 �••••. r ill ill I ::, I •••••, ,� • MIME — ♦•♦ 1 U GP 'Rpm° U t �S 11 • :: 1. : U ►:•i i I�. n .rot=e___,= FA' "�; F' ❖: �� Q 4 w %�V ��� 0 •.. S ..•-•....... FCMH s 1 ph • „ D ,3sm j i SFMH Nmo•■s-a mit I 0 •�11� 0 At-; I ' 1 N IIII , I/V 0 6 ui I S ABBREVIATIONS SCALE: 1" =80' PTMH: PRETREAMENT MANHOLE II 0 80 FT SFCB: CONTECH STORMFILTER CATCH BASIN SFMH: CONTECH STORMFILTER MANHOLE JUN 2022 FCMH: FLOW CONTROL MANHOLE I O&M MAINTENANCE AGREEMENT 3J CONSULTING BMW OF TIGARD EXHIBITA 1 CIVIL ENGNEERRSG.WATER RESOURCES.COMMUNITVPLANNING PRIVATE SD LAYOUT