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Report (17) • k, vc`c - lX v u . [El BARGUAUS EN \A Sv, _; - ,h \v vai?-4i STORMWATER MANAGEMENT REPORT McDonald's ADA Improvements 12388 SW Scholls Ferry Road RECEIVED Tigard, OR 97223 JUN 17 2.019 CITY OFTIGA D Prepared for: BUILDING DIVISION Freiheit Architecture 929 108th Avenue NE, Suite 210 Bellevue, WA 98004 Engineer of Record: Chris Jensen, PE Barghausen Consulting Engineers, Inc. 18215 - 72nd Avenue S. Kent, WA 98032 ¢E0 F'RQFFS (425) 251-6222 �� s% cjensen@barghausen.com (Y 9,2 9y?.5P . r IlkRevised June 11 , 2019 ��'/S R J�NSF 6/11/19 Aril 19 201 • EXPRES: F 30 1 Our Job No. 20603 BARGHAUSEN CONSULTING ENGINEERS,INC. 18215 72ND AVENUE SOUTH KENT,WA 98032 P)425-251-6222 F)425-251-8782 BRANCH OFFICES. TUMWATER,WA KLAMATH FALLS,OR LONG BEACH,CA ROSEVILLE,CA SAN DIEGO,CA barghausen.com DESIGNERS CERTIFICATION AND STATEMENT I hereby certify that this Stormwater Management Report for McDonald's SW Scholl's Ferry Rd. ADA Improvements has been prepared by me or under my supervision and meets minimum standards of the City of Tigard and normal standards of engineering practice.I hereby acknowledge and agree that the jurisdiction does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities designed by me. ����Vp PROP-4-,s, zu �ciP,/ cF /° 0 * oe 1 `1a ) 0 114:2-'`"yR/S R.3�\'\c'4, 6/11/19 EXPIRES: 6-30-1 9 TABLE OF CONTENTS 1.0 PROJECT OVERVIEW AND DESCRIPTION 2.0 METHODOLOGY 3.0 ANALYSIS 4.0 ENGINEERING CONCLUSIONS 5.0 STORMWATER FACILITY DETAILS AND EXHIBITS 6.0 FINAL OPERATIONS AND MAINTENANCE (O&M) MANUAL AND O&M FORM 7.0 ADDITIONAL FORMS 8.0 ASSOCIATED REPORTS SUBMITTED EXHIBITS EXHIBIT A Vicinity Map EXHIBIT B Assessor's Map EXHIBIT C FEMA Map EXHIBIT D Soils Map EXHIBIT E Existing Conditions Map EXHIBIT F Post-Developed Basin Area Map • a , , „ _ , , „„ .., ..„„ ,, _ , , mart ? y�z .„ ._,„ ..,_.1, _ ,.,j, ., _, ,, .,, ,„. 1 ' " 4 +z k x• f ;. r k N, S`# RY fig, t k z -.,,, tx5''''.- ..144:7:ift7.-_,:t1,,,„1 S�' d su :f f 1.0 PROJECT OVERVIEW AND DESCRIPTION Size and Location of Project Site The project site is located at 12388 SW Scholls Ferry Road in the City of Tigard, Oregon. The generally rectangular parcel is 1.27 acres in size. Please refer to Exhibit A-E for the existing information. Type of Development/proposed Improvements The project proposes to meet accessibility requirements via relocating ADA parking stalls, reconstructing sidewalks around the building perimeter and constructing an ADA path leading to the SW Scholls Ferry Road right-of-way. Moreover, improvements in the drive-thru area include repaving the drive isles and installing landscape. Topography The site is generally elevated at approximately 236 feet above mean sea level with existing slopes that range from 1-5%. The northern portion, bordering SW Scholls Ferry Rd, contains steep slopes within the landscaped area ranging from 8% to 25%. The surface is largely covered with concrete and asphalt pavements, generally sloping down towards the north side of the property. Soils Soil maps from the Natural Resources Conservation Service(NRCS)were utilized to analyze the soil, conditions in the site vicinity. The existing near-surface soils near the site consist of Woodburn silt loam sloped at 0 to 3 percent and Aloha silt loam. Woodburn and Aloha silt loam generally has a moderately low to moderately high hydraulic conductivity ranging from 0.06 to 0.2 inches per hour and from 0.2 to 0.57 inches per hour respectively. The water table is mapped approximately between 18 to 32 inches below ground surface in the site vicinity. Hydrology The area of the site is located within the jurisdiction of Clean Water Services and is located in the Tualatin Watershed. The 712 square mile basin provides storage and releases water to Clean Water Services and a number of tributaries. Per FEMA Standards,the project is situated in a minimal hazard zone (Zone X). Vegetation &Habitat The proposed project has minimal vegetation with existing trees to remain around the perimeter of the site. Water Quality Sensitive Areas The proposed project site does not h-v- - _ .- . .. Property Zoning The project site is zoned General Commercial (C-G), per the Zoning and Comprehensive Plan of Tigard City. This zone permits the operations of restaurants and is designed to accommodate establishments with a citywide trade area. 1 20603.002.docx Access The site has two 23-foot existing driveways located along an ingress/egress easement perpendicular to SW Scholls Ferry Road. The proposed ADA path, leading from the store to the SW Scholls Ferry Road right-of-way, will be constructed on the northeast portion of the building. Utility Availability and Conflicts No utilities are expected to be altered for the scope of this project. The contractor shall verify the location of the existing telephone line along the SW Scholl's Ferry Rd right-of-way to ensure there is no conflict with the proposed pedestrian right-of-way access Site Analysis Permits Required Permits required for this project include a City of Tigard Site Work Permit. Existing vs. Post-Construction Conditions The existing site consists of an existing McDonald's Restaurant with associated concrete sidewalks, paved parking lot and drive aisle(s) for maneuvering. Landscaping surrounds the site boundaries with planters spread evenly amongst the boundary parking stalls. Please see the Existing Conditions Map located in Exhibit E for details of existing site conditions. The total site existing impervious surface is 37,304 square feet. Post-Construction includes the relocation of the ADA parking stalls, repositioned drive thru lanes, regraded sidewalks and an accessible ramp system leading to the SW Scholl's Ferry right-of-way. Please see the Post-Developed Basin Map in Exhibit F. The project proposes to modify 6,737 square feet of impervious surface. 2 20603.002.docx << N • Tab 2 . 0 • • t , „. ,,„ . „.. „.„, . ,... , „. ., . , ..„ , ,,, „ .. ..„ tee . . . „„ „ .. „. .„ • g` • • 1, • „ �1„,a , • • • • • g VZ7a},*,.-4,..< :tft1.1t1: �z fix, c a w� -,- "• ' #fir' Exhibit A VicinityMap p Exhibit B Assessor Map Exhibit C FEMA Map 1 OO - GoO ,..) s\_____i_IL„,r-- SW CONESTOGA DR 1__V.-- .--- .......,„r NOTE: MAP AREA SHOWN ON THIS PANEL IS LOCATED WITHIN TOWNSHIP 1 SOUTH, RANGE a I R� a H E SEND D SW SOON S CC csiH- wLIMIT OF STUDY SW GLEVEt-ANYN D BAL SW TARPAN DR SW SCHOLLS FERRY RD O00 \IsI sw H Q SITE GLEN CWOOD MI s(\ o RD2723 o X SW G I ASHWOOD Q�� 33 wCT 0 z t) cn U H m SW SNOW a CITY" OF TIGARD `� t I BRUSH CT 410276 .,-- EARS ST C} S,// NY-44/ QD SWANTON DR w SW MANZAP , Q 77 SW w = SUMMER ¢ F-- 125TH o, ) 0 SW PL Slimmer Creek TOCTYU i � 1 I s -- t SW GLACIER LILY C/R ZONE SW NORTH DAKOT, O AE © LEGEND +�® SW MILLVIEWI OTHER AREAS _ ZONE X Areas determined to be outside the 0.2% ZONE.AE v \ \SW SUMMERC P annual chanceflood lain. i REFERENCE: Federal Emergency Management Agency(Portion of Map 41067C0533E, Nov. 2016) Scale: For Job Number Horizontal: N.T.S. Vertical: N/A McDonald's Remodel 20603 Barghausen Tigard, Oregon Consulting Engineers, Inc. 18215 72nd Avenue South Title: Kent,WA 98032 FEMA MAP 425.251.6222 barghausen.com DATE:04/10/19 P:120000s1206031exhibitigraphics120603 fema.cdr Exhibit D Soil Survey Map 2.0 METHODOLOGY Drainage at the Existing Site From review of the existing site survey, the site is graded so that runoff flows away from the landscaped perimeter and towards catch basins within the parking lot. The stormwater is then routed north to SW Scholls Ferry Road via a 12-inch public storm drain. There are six (6) on-site catch basins that capture the flow from the site and route it to SW Scholls Ferry Road where it enters existing City storm infrastructure and continues west. There are no anticipated impacts on existing drainage from the site development, as the proposed redevelopment will maintain existing drainage patterns prior to discharge to existing city storm infrastructure. Infiltration Testing Results There are no infiltration testing results provided for this project site. However, soil maps from the Natural Resources Conservation Service (NRCS) were utilized to analyze the soil, conditions in the site vicinity. The area is known to have a groundwater level between 18 to 32 inches below grade. Description of Proposed Stormwater Management Techniques The proposed project includes the redevelopment of more than 1,000 square-feet of impervious surface. Per Section 4.05.1 of the Design and Construction Standards of Clean Water Services exceeding this threshold requires a permanent water quality approach. The impervious area required to be treated for this project, pursuant to Section 4.05.5(c)of the Design and Construction Manual, is all new impervious surfaces and three times the modified impervious surface, up to the total impervious surface of the site. Using the 6,737 square feet of modified impervious area, the required area for treatment is 20,211 square feet. 3 20603.002.docx „,,, ,,,,” : , : 7., _.. , , ..,, _ . _ , 3 . 0 „ , ,_ . , , , _ _ , , . , ,, Ta b , , . . , , .., , , , _ , , , , . , _ , _ „ . , _ , _ , , _. , , _ _ , , , , _ , , , s _ , _ . _ ,... _ , , , , _ , , ,,, . ,,,, ,, , ., ,... , , , , ,, , . , ,, , , _,\, ,. _ , ,„ ,. , . _„<: ., , ,.. „„ , „ , „ , , . , .. _ , , , , , , , , , . , ,_ , , . , , , , , . . _ , , _ , ., , . ... , , , , _ _ „ , , , _ , , , _ , ,,,.. , _ ,, .. ..„ „,, , , _ , , ..„, ,....„. , -Ns er-- , -- _-•...,:- .0., \‘-' ,\FT—,,,,,A0. '"'” ''''— 01_,,,,,,,.,-,,(,,T,,, j ,..ate �,,�� 3.0 ANALYSIS Design Assumptions The project impervious area will largely remain the same from the existing developed condition. In comparing the existing condition and developed condition, it is found that there is no increase in flow from the site. Therefore, detention is not required for the project. To meet water quality standards, the CWS Design and Construction Standards Manual first requires the consideration in the following order of hierarchy: vegetated water quality LIDA, proprietary systems meeting requirements found in Section 4.05.8, or an alternative water quality approach if any. If these techniques are determined to be infeasible due to site constraints, topography, or soils, then a regional approach may be considered. LIDAs can be determined using the site conditions described in Section 1.0 of this report and Table 1 from the LIDA handbook. Based on the known high groundwater (18 to 32 inches below grade) underlying the site vicinity, infiltration is not feasible for this site. The site conditions are also known to have steep slopes (8 to 25 percent) in the largest landscaped area bordering the north boundary and the remaining existing trees, surfaces, and grades onsite make most LIDA techniques infeasible. The following is a discussion considering the feasibility of each LIDA selection found in Table 1 of the LIDA Handbook: • Green Roof: This LIDA cannot be used since the existing site scope does not involve redesigning the existing roof structural ability. • Porous Pavement: Porous pavement is infeasible since it requires the groundwater table to be a minimum of 10 feet below the facility's bottom and the site vicinity groundwater is a maximum of 32 inches below grade. Moreover, porous pavement is not feasible on high- use sites due to its porous characteristics. • Flow-through Planter: The flow-through planter would be feasible if the site possessed a location practical for water to be directed towards the facility, however the existing parking lot is graded away from all planter strips and routed to catch basins within the parking lot. The catch basin in the northeastern corner of the parking lot could be routed to a facility, but the treatment requirement is at least 20,211 square feet of impervious surface which would size the planter strip at 1,213 square feet. There is not enough room to place a planter this size near the catch basins able to convey the required area without extensively regrading the site beyond the intended scope of the project and consequently requiring more impervious area to be treated in the process. Regrading the existing parking lot is not practical to achieve feasibility since it does not align with LIDA objective 1 or 2: Conserve Existing resources and minimize disturbance. • Infiltration Planter/Rain Garden: The infiltration Planter/Rain garden is not feasible due to high groundwater found in the area (18 to 32 inches). • Vegetated Filter Strip:A vegetated filter strip would be ft-m*4e in locations where planter strips exist and grades promote flow towards the planters. However, for the same reason as the flow-through planter, the existing parking would have to be regraded to achieve the required basin flows. • LIDA Swale:The LIDA Swale cannot be placed in steep slopes nor can the existing parking lot be regraded to promote drainage towards planter strips where a swale could be placed. • Street Side LIDA Planter: According to Table 1 in the LIDA Handbook, this Planter is not suited for areas with high groundwater and onsite locations that would support this LIDA are not downstream of runoff. 4 20603.002.docx • Proprietary Units: The LIDA techniques are infeasible as determined by the preceding analysis. Generally when this is the case, treatment can often times be provided via an approved proprietary unit. Pertaining to this project, the existing drainage infrastructure on- site is too shallow to accommodate a proprietary unit for water quality. Furthermore, the treatment basin as required would necessitate multiple units as the existing site is graded to drain to different catch basins. Capturing the required basin would not only require replacing catch basins on-site with multiple proprietary water quality units, but also reconstructing and resetting the existing storm drains. This leads to a 'snowball effect' as the implementation of water quality would add additional scope that would otherwise be unaccounted for in the original proposal. As stated previously, the project proposes to rely on the existing drainage infrastructure in the developed condition as the development will overall be less taxing on the existing system. The project seeks relief from the preceding water quality methods to prevent significant disturbance and deviation from the original intended scope of the project. The CWS manual lists the option to pay a fee in lieu of water quality treatment due to existing site constraints and the need to propose methods that would not correlate with the Five LIDA objectives. Approved Storm water Sizing Calculator Narrative Form and Printouts No LIDA facilities were considered to be feasible for this project. Therefore, no forms or printouts were necessary. 5 20603.002.docx Tab . . — — • .. . . . ..... ...... _ ..,...... ....,. .,.. _, ..,.„. ., ,, „. •,„.,.,..:::.••,..,,,,„::: „,..„,,,,,„,,,,,,,,„,..,„„... rY ,,,,,,,._ ..,, .„,..... ..„...„,„,..„ " „,•,„:„.„.....„..,,,,,,.„.,,,,...„,„...,..„.,,„. ,,,,,,,,„ ,:,.. ••:„. ,:„:„."';'.'":...lit.,'ScL''''''.„5--k,-,*,,,_„:* } ; ii f Y i 4.0 ENGINEERING CONCLUSIONS It is believed that the required water quality facilities to be considered were analyzed and determined infeasible due to existing site constraints. The Fee in Lieu of program is requested to provide more effective treatment to the modified impervious surface in a regional facility downstream than what can be treated onsite. 6 20603.002.docx 34-0 Tab 0 ■ M >a` g' � F I 5.0 STORMWATER FACILITY DETAILS/EXHIBITS The following exhibits are provided herein: EXHIBIT E Existing Conditions Map EXHIBIT F Post-Developed Basin Area Map 7 20603.002.docx a r _ yetu ' k , , r- ?a . -, `n.<- \ „, _, ' ,, amu,..:,>,^a,, \ .. \a,a �g e >�n., „ , fia . a-...,m� a - ,r, a ., � �;,, ,a_ �a ,�.; .� . '.^ 1" `F � 0, `�' � ' uao ,a\�\\. . a \ - ;a e,\ � �, .,,.,o: \,1� pad �` _-: .� pw ..., . � � , ' " �: ,. .. \ ., .. ,-, 4a � ,.�! �\. '^ aua`�<` `�.--. � a- ..v:s �>: - \ ,....�,:, ,a,-<., vv - r�' -uu aa\. \.. '$ , . , , a--.. �'` a,^,,, ,a<a.h...-.. ,- .� , :r\av .„e ,.: . ^. - ^;�s ,a a � �F �\\,• ��\\� \ \ , ,.:.� ,;.:,�- ar )?s uw aa.-. 6 ,. `� �:,.-a d...-� aaau ,�„ <. \\at? a\-- , r, \ �... <,.r, .^, -.> .a..�\\ ', �� �aa\ ,.1 ...: ,AK,,,,,,.,:A. _�;.. .,%..� 'm�.. a ar. �> ,� \ ,, ..,..a., w4.<. ,, a...^, ,\F,,.. :,, ,:�. \\ n=C. � u, ,�,.v ,, m.y .� ... gin, s., \ ; \� �, ,\, �; r , , mus ; a . ; ti: ��, ,';;\0\ <,, > '„ , 141 a „ a F X 1 u � r � \ ,o y ^4 V F \, a s 9 ' d Q a ! 0. > a rt s s..n. ,..,, ... _ .,-,r,��-�,, „p - ',,,:i;v&^P=<.�5u ..s` r,'i" "iwo..... " ".g "°�a y� t ' i\\ \�\�\„� �e,x .t� \<: \� AAAA .\\�'�i\�\ ,, .... , -�„w -.-,in, Os'`‘..,,,,,a ,.,,a 4"„,.a °\0\� �\\\, a\ula\��\\� ���,��<\��aa\\\�\\�e\ \�,.,�(��' �-�\S�\`���'a:... aS \� ��,m\�� 0 • , CC) I Exhibit E Existing Conditions Map Exhibit F Developed Basin Map I 6.0 OPERATIONS AND MAINTENANCE (O&M) PLAN AND O&M FORM No additional facilities are proposed for this project. Therefore an operations and maintenance manual will not be provided in this report. 8 20603.002.docx , ,WS:\ > • `�,31v3,' ttl A.:._ •I 3::: -a„' • ::..: +Y*,'r5f' \ h'>:” t�, >u'tt tviolo ttaf tAttt4 ,+s yq� C„y\. S,�g ,^xis„.r x' _7 \�,.\ ttttd•„41 LttgOgittigttgfttifigillAPIEStWit • �,e�a, ars �„ .>.: ., a . .... • \���R� `\0\\\�\\\\ .err ,,,\\\0\\\\\ rikitritttatti � R a s :,.. .„ ... ,..,; ,>,...<, «<, � .,, �\\\\\ �\. „ '' \`, .; • �� �' r�� \R\ r J,1;a @.�'•'s".fir Olf rags � � 1< a�I�... v "\i r. \h,\\, `,,,, � � t R -i... � p .:.. :�\p \�,. „'+:.. r0. 2.h 1 k�. s:=, \� \a\\ ;¢,x �;. e„,,as. 1 ;s�=.:Fr .+^ a' + • eE k. �p p , ., „.. \��t\,,. .,+. ,���; ✓�>,.,<F.,,,:... 141,404 Uv..:rE, 4.4a.aA�o/V� . k , . � O 7.0 ADDITIONAL FORMS There are no additional forms to include. The project requests the district rates and charges for the Fee in Lieu of construction or implementation of Water Quality approaches as described in Section 4.05.2(b) of the CWS Design and Construction Manual. 9 20603.002.docx \a \ e s r a ,�+ �•,n. \a 'u,a,=:= r\Y r�t a ,.,=«\, s\x�\�� v=�-<..,', 5v�' ._as: f x_d`:. ikiadosigimit , \ ` \\-i; y:Of M \� x :n O , " �. a � . ,� < '4011 1411 olkyi ,.� ,. a c•e,.:: :,,.:,,k,„ �- xi`,`: �� ',� l`\:Sy.• ,. �• P a,4-._ ,..K x .c-,x=� drv, `\\` �`„ .. moi.. � -t: ,.,,.. ,,i ,.y., �' •:,a,..-, a ,,,,, -:': „1Y`..:�, "� 153£d`�„nfiA..a(r°Y\b d��.: �'Fy., .... w�� :ate „, ...,.: ..,,'��,\�� .•. ,a\,,,,:„.a..,::,.,`3\\��,.`.�va.�s==,..sdca.'.aa,\\+�-.�a\aH,S`aa,\:s1-w�<+,r��,d,�,."a,�,��\,� � g-.',a\�_�,,�. > :-, \+ ,e..,_„�1'����`, �. -��ys,1 ra,xr rti \ �, i,k . ` @t Aa _ A \a-- :- . . „ xg, b C • CO tiCS 8.0 ASSOCIATED REPORTS SUBMITTED There are no associated reports to include 10 20603.002.docx