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SWP272171(19)
40 �: CITY OF RENTON .AL Planning/Building/Public Works Department Earl Clymer, Mayor Gregg Zimmerman P.E., Administrator November 2, 1994 Larry Karpack Northwest Hydraulic Consultants, Inc. 22017 - 70th Avenue South Kent, WA 98032 SUBJECT: WETLAND MITIGATION BANK SITE 2 PRELIMINARY HYDROLOGIC ANALYSIS PROFESSIONAL SERVICES CONTRACT CAG-94-130 Dear Mr. Karpack: Enclosed is an original, fully executed contract for the above project authorizing your team to proceed with the project and perform the services outlined in the contract scope of work. Thank you for your efforts in the scope of work development and contract execution. I look forward to working with you toward the successful completion of this project. If you have any questions, please call me at (206) 277-5547. Sincerely, Scott Woodbury, Project lager Surface Water Utility H:DOCS:94-1006:SW:ps CC: Ron Straka Enclosures 200 Mill Avenue South - Renton, Washington 98055 CITY OF RENTON CITY CLERK'S OFFICE MEMORANDUM DATE: November 1, 1994 TO: Scott Woodbury, Utility Systems FROM: Bonnie Walton SUBJECT: CAG-94-130 The attached original document has been fully executed and is being returned to you. Please transmit the original to the contractor and retain a copy for your file. An original document is also retained by the City Clerk. Thank you and have a nice day. Enclosures: (1) CONTRACT CHECKLIST STAFF NAME & EXTENSION NUMBER: —o Ir W Op 06 u 141 �y-7 DIVISION/DEPARTMENT: Su2Fp�c,i- VOIAT R Uri(I/Ty Pi'8 I pw CONTRACT NUMBER: Nam// ANT�� TASK ORDER NUMBER(if applicable): k/a CONTRACTOR: PURPOSE OF CONTRACT: �ti► 1. LEGAL REVIEW: (Attach letter from city attorney.) A)/,A Fok L�54 T�4 x' $ 16 6bt) , 2. RISK MANAGEMENT REVIEW FOR INSURANCE: ( ttach letter.) 576C -krrAU00 i%J sH "41,0 . 3. RESPONSE TO LEGAL OR RISK MGMT CONCERNS: (Explain in writing how concerns have been met.) N)R 4. INSURANCE CERTIFICAT AND/OR POLICY: (Attach original.) � �J�'U4� (/a fAw-?) 5. CITY BUSINESS LICENSE NUMBER: yy62 (Call Finance Dept.) 6. ATTACHED CONTRACTS ARE SIGNED BY CONTRACTOR: (If not, provide explanation.) yo 7. FISCAL IMPACT: A. AMOUNT BUDGETED (LINE ITEM) (See 8.b)* B. EXPENDITURE REQUIRED: 2, 0 8. COUNCIL APPROVAL REQUIRED (Prepare Agenda Bill.): 41)f- A. CONTRACT OR TASK ORDER IS $50,000 OR OVER: (Refer to Council committee for initial contract approval; place subsequent task orders on Council agenda for concurrence.) B. *FUND TRANSFER REQUIRED IF CONTRACT EXPENDITURE EXCEEDS AMOUNT BUDGETED. (Refer to Council committee.) C. SOLE SOURCE CONTRACTS. (Refer to Council committee.) 9. DATE OF COUNCIL APPROVAL: 0A 10. RESOLUTION NUMBER (if applicable): N1p 11. KEY WORDS FOR CITY CLERK'S INDEX: A. Swe ' �3-_;Y7/ B. r_GtS<r 5tc- C—P"` 01-4A !0'o UL' 6�+ -►� ��5�� C. Sekx)6 A ecolc// 6Aalc c:\winword\forms\chk1iat , lJ✓E S( i^+V r0 1 T J 1s AT)0W li/QN JC ' 09/02/93 f v a t� cs CITY OF RENTON ..0 Office of the City Attorney Earl Clymer, Mayor Lawrence I Warren _ MEMORANDUM qPR 1 4 1993 /To: Ron Olsen, Utility Systems C?rY C F r•f'` '``14 From: Lawrence J. Warren, City Attorney Date: April 13, 1993 Subject: Legal Approval of Task Orders You called and asked whether I needed to reveiw Task Orders under $10,000.00 when they were attached to an approved contract and the ;contract was not modified in any fashion. Under those circumstances, there is no need for legal review. The Task Orders themselves are technical in nature and have;little or no legal implication. My main scope of review is of the contract itself, and since the contract will not be changed I do not need to rereview the material_ Lawrence J Warren LJW:as_ cc_ Mayor Earl Clymer A8:96: Dncf (IFF;.n Pn- �7� _. iM C '7nri CtrnPt _ RPntnn Wncl,;nntnn OPnl�- _ /')nFl)��_R079 CITY OF RENTON MEMORANDUM DATE: October 21, 1994 TO: Gregp Zimmerman �t FROM: Isen { STAFF CONTACT: Ron Straka'- U— Scott Woodbury (X-5547) SUBJECT: EAST SIDE GREEN RIVER WATERSHED WETLAND MITIGATION BANK SITE 2 - PRELIMINARY HYDROLOGIC ANALYSIS ANNUAL CONSULTANT CONTRACT WITH NORTHWEST HYDRAULIC CONSULTANTS ISSUE: The Surface Water Utility requests approval of the annual consultant contract with Northwest Hydraulic Consultants (NHC) for Wetland Mitigation Bank Site 2 - Preliminary Hydrologic Analysis. RECOMMENDATION: The Surface Water Utility recommends approval of the annual consultant contract with NHC for Wetland Mitigation Bank Site 2 - Preliminary Hydrologic Analysis. The contract is less than $10,000 and may be signed by the Department Administrator. BACKGROUND: On July 19, 1993 the City executed a professional services consulting contract with Parametrix, Inc., to establish the technical and programmatic framework for the conversion of existing upland on the two City of Renton mitigation bank sites to wetlands and for the use of these wetlands to offset impacts to lower quality wetlands by private and public development that may occur in the same drainage basin. An alternative under consideration in Parametrix's work for the Wetland Mitigation Bank project proposes the excavation of existing fill on migitation bank site 2 down to near the level of the adjacent Springbrook Creek channel. Mitigation bank site 2 is 13.93 acres in size and is located adjacent to and east of Springbrook Creek, south of SW 34th Street, and east of Oakesdale Avenue SW in the City of Renton. The proposed excavation would allow flows in Springbrook Creek above a, specific design flow to backup onto the site and be temporarily stored. As flows in Springbrook Creek recede, the water stored on site 2 would return to the creek. The current Parametrix contract scope and budget does not include hydrologic analysis of the effects of the above alternative on Springbrook Creek flows and water levels Gregg Zimmerman Stream Monitoring and Data Analysis Page 2 through direct modeling techniques. However, because direct modeling will yield more detailed and useful information for the comparison of the wetland mitigation bank alternatives and selection of the preferred alternative which could help solve some of the flooding problems in the valley. The recommended approach is to determine the flood storage benefits by using the hydrologic analysis model, Hydrologic Simulation Program Fortran (HSPF), as currently being refined by NHC for the East Side Green River Watershed Plan project (CAG-90-033 Addendum No. 9-94). The HSPF model will be used to compute continuous flow hydrographs at various stream locations throughout the Black River Basin for a 30-year period of recorded hydrometerologic data (precipitation, etc) and can be modified for use in the wetland mitigation bank project. Through the proposed contract, NHC will use HSPF to analyze the effect of the additional floodplain storage on Springbrook Creek flows and water levels at mitigation bank site 2 (SW 34th Street) under current and future land use scenarios. The contract work will also provide additional hydrologic data for use in the site design of elements such as the type and location of wetland plantings. Depths and quantities of storage that will be provided on the project site for each land use scenario and the time that the stored water is detained on the site at various depths will be estimated. The expenditure required for the proposed contract is $2,892.56. An additional $195 expenditure is required for purchase of the Corps of Engineers HEC-FFA frequency analysis program which NHC recommended be used for the contract work. Funding for the contract is proposed from the Surface Water Utility capital improvement project account budget for the wetland mitigation bank (421/600/18.596.38.65.651 19). The unencumbered balance of the approved 1994 budget for this account is $16,151 .75, which includes the approved 1994 budget mid-year appropriation of $20,000. The remaining 1994 budget for the wetland mitigation bank account will be used to fund staff engineering and project management costs associated with the planning and design of the wetland mitigation bank. H:DOCS:94-966:SSW:ps Attachments CONCURRENCE DATE 6/2'/9f CITY OF RENTON NAME INITi;'•L,'�. �o_uof MEMORANDUM DATE: October 21 , 1994 TO: Gregg Zimmerman FROM: Ron Olsen STAFF CONTACT: Ron Straka Scott Woodbury (X-5547) SUBJECT: EAST SIDE GREEN RIVER WATERSHED WETLAND MITIGATION BANK SITE 2 - PRELIMINARY HYDROLOGIC ANALYSIS ANNUAL CONSULTANT CONTRACT WITH NORTHWEST HYDRAULIC CONSULTANTS ISSUE: The Surface Water Utility requests approval of the annual consultant contract with Northwest Hydraulic Consultants (NHC) for Wetland Mitigation Bank Site 2 - Preliminary Hydrologic Analysis. RECOMMENDATION: The Surface Water Utility recommends approval of the annual consultant contract with NHC for Wetland Mitigation Bank Site 2 - Preliminary Hydrologic Analysis. The contract is less than $10,000 and may be signed by the Department Administrator. BACKGROUND: On July 19, 1993 the City executed a professional services consulting contract with Parametrix, Inc., to establish the technical and programmatic framework for the conversion of existing upland on the two City of Renton mitigation bank sites to wetlands and for the use of these wetlands to offset impacts to lower quality wetlands by private and public development that may occur in the same drainage basin. An alternative under consideration in Parametrix's work for the Wetland Mitigation Bank project proposes the excavation of existing fill on migitation bank site 2 down to near the level of the adjacent Springbrook Creek channel. Mitigation bank site 2 is 13.93 acres in size and is located adjacent to and east of Springbrook Creek, south of SW 34th Street, and east of Oakesdale Avenue SW in the City of Renton. The proposed excavation would allow flows in Springbrook Creek above a specific design flow to backup onto the site and be temporarily stored. As flows in Springbrook Creek recede, the water stored on site 2 would return to the creek. The current Parametrix contract scope and budget does not include hydrologic analysis of the effects of the above alternative on Springbrook Creek flows and water levels Transmittal Letter northwest hydraulic consultants inc. 22017 70th Avenue South Kent Washington 98032 (206) 872-0218 (206) 872-0518 fax Date 1612rolc4 Job No. To SCA (0008buc y Regarding we6rd M 1f;ga+ion Lek Gf e- 2 - Tr'e I;m H We Are Sending attached ❑ separate by Description 2 i �► �C.1 Contra Or X e C uf G� This is M as requested ❑ for your use ❑ for approval ❑ for review and comment Remarks From Copy To PLANNING/ BUILDING/ PUBLIC WORKS DEPARTMENT MUNICIPAL BUILDING 200 MILL AVE. SO. RENTON, WASH. 98055 v �s 0 UTILITY SYSTEMS DIVISION - 235-2631 NT 0 TRANSPORTATION SYSTEMS DIVISION - 235-2620 TO: DATE: JOB NO.: RE: ATTN: GENTLEMEN: WE ARE SENDING YOU ❑ ATTACHED o UNDER SEPARATE COVER VIA THE FOLLOWING ITEMS: o SHOP DRAWINGS o PRINTS ❑ REPRODUCIBLE PLANS ❑ SPECIFICATIONS ❑ COPY OF LETTER o COPIES DATE NUMBER DESCRIPTION AND REMARKS THESE ARE TRANSMITTED AS CHECKED BELOW: ❑ FOR APPROVAL ❑ APPROVED AS SUBMITTED ❑ RESUBMIT COPIES FOR APPROVAL ❑ FOR YOUR USE ❑ APPROVED AS NOTED ❑ SUBMIT COPIES FOR DISTRIBUTION ❑ AS REQUESTED ❑ RETURNED FOR CORRECTIONS ❑ RETURN CORRECTED PRINTS o FOR REVIEW AND COMMENT ❑ o PRINTS RETURNED AFTER LOAN TO US COPIES TO: SIGNED TITLE IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE Y o� CITY OF RENTON t HUMAN RESOURCES AND RISK MANAGEMENT �10 MEMORANDUM October 20, 1994 TO: Scott Woodbury Planning/Building/Public Works FROM: Beverly Nelson Glode Human Resources bV SUBJ: Wetland Mitigation Bank Site 2 Preliminary Hydrologic Analysis I have reviewed the Certificate of Insurance submitted for the above referenced project. The coverage and Certificate meet the City's risk management requirements. If you have questions, please let me know. RNG:sr CITY OF RENTON PUBLIC WORKS DEPARTMENT REQUEST FOR INFORMATION OR CONCURRENCE DATE: October 19, 1994 TO: Beverly Nelson Glode FROM: Scott Woodbury(X-5547) 5Uj CONTACT PERSON: SUBJECT: Annual Consultant Agreement with Northwest Hydraulic Consultants for Professional Services for Wetland Mitigation Bank Site 2 Preliminary Hydrologic Analysis Attached for your review,changes and/or comments are copies of the following • Exhibit A- Scope of Work(1 page) • Exhibit B- Cost Estimate(2 pages) • Consultant insurer's Business Liability Coverage form regarding additional insured(1 page) • Two Certificates of Insurance dated 9/29/94(2 pages) • City of Renton Insurance Information form(1 page) • Memorandum of Insurance Dated October 12, 1994 to supplement the professional liability certificate of insurance regarding cancellation notification(1 page) • insurance policy face sheet and declaration pages(5 pages). Under one alternative under consideration for the City's Wetland Mitigation Bank project, existing fill on site 2 of the City's two wetland mitigation bank sites would be excavated down to near the level of the adjacent Springbrook Creek channel to allow flows in Springbrook Creek above a specific design flow to backup onto the site and be temporarily stored. As flows in Springbrook Creek recede, the water stored on site 2 would return to the creek. The purpose of the proposed contract is to analyze the effect of the additional floodplain storage on Springbrook Creek flows and water levels under current and future land use scenarios and to provide additional hydrologic data to facilitate wetland planting and other site design elements. Depths and quantities of storage that will be provided on the project site and the time that the stored water is detained on the site at various depths will be estimated. The project site is 13.93 acres in size and is located adjacent to and east of Springbrook Creek, south of SW 34th Street, and east of Oakesdale Avenue SW in the City of Renton. The risk associated with the work to be completed is believed to be low. The attached insurance forms are copies of those previously approved this month for the Streamflow Monitoring and Data Analysis contract. The consultant is sending new forms specifically for this project that will be identical to the attached forms, except for the City of Renton project identification number. Your assistance in returning comments to me by October 26, 1994 is appreciated. If you have any questions or need more information, please call me at X-5547. Thank you for your assistance. CONCURRENCE Name Date H:DOCS:94-963!!:SW Attachments OCT 10 '94 12:54 NW HYDRAULIC CONSULT 760 Pal /0//ol q7 northwest hydraulic consultants inc . 22017 70th Avenue South Kent Washington 98032 206-872-0218 206-872-0518 fax FAX MESSAGE Date: From: L-Wr(j ars�or_iC To: Company: Fax #: City: Pages to Follow: 5 Original in Mail: Please call immediately if you do not receive all pages of this transmission. ciCo4, 114 a 100K cc) i�,`s jo see �� eve�� ,�„g c400 Lzaof �s coot't ea 1 /vVT 0 /A,,ic>,fs /`l�au FC0 /.j OCT 10 '94 12:55 NW HYDRAULIC CONSULT 760 P02 Exhibit A - Scope of Work Wetland Mitigation Ban" er S� k Z �ltioGr� /��1�lhSiS �/�tra�n4/�► Task 1 - Preliminary Modeling Northwest Hydraulic Consultants (NHC) will modify our current and future land-use HSPF models of Springbrook eek to account for additional storage proposed at Wetland Mitigation Bank Site 2 near O e Avenue and SW 34th Street. Note that the current conveyance system HSPF models without the mitigation bank site are being developed by NHC under a separate sub-contract to the City's CAG-90-033 Addendum No. 9 contract with RW Beck. The attached estimate assumes these models and time series data will be available for use in tJW cu t study. Quantification of the stage/volume relationship for the proposed bank site will e provided by the City of Renton. For preliminary modeling, the inflow/outflow hydraulics of the wetland banking site will be assumed to be inconsequential. (i.e. flows will be assumed to pass freely into and out of the bank site without hydraulic constraint). NHC will perform long term simulations for water years 1961-1991, and determine flood flow frequency quantiles (2-, 10-, 25-, and 100-year) for Springbrook Creek upstream of SW 34th Street for current and future land-use with the proposed additional off-channel storage provided by the wetland mitigation bank site. These will be compared to flood frequency quantiles for the existing conveyance system as determined in NHC's analyses for the aforementioned RW Beck contract. Using the 30 year simulated record NHC will conduct an inundation analysis of the wetland mitigation bank site (i.e. the HSPF simulated water level upstream of SW 34th Street) under existing and proposed conveyance conditions with the two land-use scenarios. The inundation analysis results shall be presented in tabular form similar to that shown in Exhibit C, using ten increments of stage to cover the entire range of stages simulated over the 30-year simulated record. Inundation analyses will be conducted for the annual time series of stages as well as the following seasons; Oct 1 - Dec 31, March 1 - May 31, and July 1 - Sept 30. NHC will prepare a technical memorandum summarizing our reconnaissance level findings. This memorandum will document our procedure and assumptions and provide a discussion of uncertainties inherent in the analysis. The memorandum will also discuss any follow up work which will be necessary to quantify benefits from the proposed project. Our budget includes several hours for presentation of the results to the City, either in a meeting or via a conference call. C Products: HSPF models (version 10) of Springbrook Creek for current and future land-use scenarios with and without the proposed project Input and output files for HEC-FFA flood frequency analysis of Springbrook Creek upstream of SW 4th Street f Its OCT 10 '94 12:56 NW HYDRAULIC CONSULT 763 P03 Exhibit A Scope of Work Input and output files for ELDUR inundation analysis of simulated stages upstream of SW 34th Street ELDUR executable program for stage duration analyses ' Technical memorandum summarizing the results of our analysis 1 Note: ELDUR is a proprietary software package created by NHC specifically for the analysis of wetland stage/duration data. NHC will provide a copy of the current executable file of ELDUR to the City at no cost as part of this contract. Currently there is no documentation for this menu driven program, with the exception of line prompts during program execution. The software provided to the City will be exclusively for the City's use in review of NHC's results or possible further investigations by the City of the mitigation bank project. The ELDUR software is still in development, and NHC does not warranty it against defect. As with any engineering application, any additional analyses generated with the program should be thorougly verified by the City. Exhibit B - Cost Estimate ESGWP Gaging Services o Cost Estimate for Wetland Banking Rocamaissance Study m Direct Labor A r N Number Units Unit Cast Total Cost CA m Principal Hours 3 hrs 40.38 $121,14 Engineer Hours 35 hrs 22.21 $777.35 Technician Hours 2 hrs 17.67 $35.34 Clerical Hours 4 hrs 14.13 $56.52 d ;a D C C Direct Salary $990.35 (, 0 Overhead 165.0% $1,634.08 co Net Fee 12.0% $314,93 Sub-total $2,939.36 Other Direct Costs Number Units Unit Cost Total Cost Truck Rental 0 Days $3 5.00 $0.00 Truck Mileage 0 Males $0.35 $0.00 Reproduction expenses(copies) 100 Copies $0.l0 $10.00 � Equipment rental for discharge measurements 0 Each $20.00 $0.00 Miscellaneous direct expenses 1 Lump Sum $25.00 $25.00 ELDUR Software User License no charge $0.00 Sub Total $35.00 Grand Total $2,974.36 Exhibit B-Cost Estimate 0 ESGWP Gaging Services-Revised Hourly Rates effective July 1,1994 m A fU Hourly r n Rates m Position ($) z c Project Manager 40.38 Senior Engineer 27,01 Engineer 22.21 � D c E Jr. Engineer 17.67 n TecJu ician 17.67 0 Jr. Technician 13.63 CO Clerical 14.13 -A Q Q m C NN Exhibit B- Cost Estimate ESGWP Consulting Services Task Breakdown for Weiland Banking Reconnaissance Study m Task Hours by Sub-Task Cost Task Cost A Task Description KML LMK ETV PDP ($) ($ N I Preliminary Modeling A. Estimate Stage/Storage Characteristics for Wetland Banking Site (See Note) B. Modify HSPF Model FTABLEs 2 $131.84 E: C. Perform Long Simulation Runs(existing land-use conditions) 4 $263.68 � D. Perform Long Simulation Rums (future land-use conditions) 4 $263,68 E. Flow Frequency Analysis (I EC-FFA format) l 6 $515.36 C F. Stage Inundation Analysis (4 seasons, 4 land-use/conveyance options) 8 $527,35 n G. Technical Memorandum 2 8 2 4 $1,039.69 0 H. Presentation of Findings (meeting or conference call) 3 $197.76 $2,939.36 z c r NOTE:Saineate assumes dud the City of Renton will supply die necessary Stage/Vohane characteristics for the%,Hand banking site Total $2,939.36 Personnel: KML- Leytham - Principal Engineer LMK- Karpack-Staff Engineer ETV-Vanderm©er- Senior Technician PDP - Phillips -Clerical m 0 m m 22 '94 07:50 NW HYDRAULIC CONSULT 604 P02 (444 I4AId FAX TRANSMITTAL MEMO co4,5r16, n4 A tilCf.. y iU FROM LA r kA Exhibit A - Scope of Work ( COMPANY Wetland)Banking Reconnaissance Study for East Side Green River Watershed k-ir/(./kr1Urj T - Preject dministration - Project administra ' cludes quality control, invoicin e control, miscellaneous client contacts, work sum emoranda, effort related to the administration of this contract. Produces• �oniMyinvoicrcs and work summaries, and q ance on all work products I Task $�- Preliminary Modeling Northwest Hydraulic Consultants (NHC) will modify ou future land-uselcurrent conveyance system HSPF model of Springbrook Creek to account for additional storage proposed at Wetland Mitigation Bank Site 2 near Oakesdale Avenue and SW 34th Street. Note that the attached estimate assumes that the current conveyance system HSPF model being developed for the ESGRWP will be available for use in this study. Quantification of the stage/volume relationship for the proposed bank site will be provided by the City of Renton. For preliminary modeling, the inflow/outflow effects of the wetland banking site will be assumed to be negligible (i.e. flows will be assumed to pass freely into and out of the bank site withou hydraulic o strat}. NHC i cd .� will perform long term simulations for water years 1961-191, . or a-e� 'pnngl?roo�c"�: �((s'+rt" °E System with the existing conveyance sys ufitem and with the proposed add'#ti nal off-channel storage S" 3yr� provided by the wetland bank site. o- 1-4 ," ,l +�r� /'` determine ency-quami r Sprinuhrook Cr�ti Ui Str�3iT�Of SW i4th Strt�trwith and withzr rhp b r ct. - mp t. d-+her--mxdnTaTmTvM of rec x"L-they--may-be chosen-to-characterize-th inrpraet events gs of�the� />Trncof.9 2-r9 P6 Bdscd on these preliminary HSPF and HEC-2 modeling results N a recomm ion to the City of Renton on orm more detailed hydraulic and hydrologic m e expected benefit, in terms of flood peak and stage reduction, f e proposed ban o'ect. a a Products: HSPF models (version 10) of the-Jewff Springbrook Creek system with and without the proposed project Frequency plots for Springbrook Creek upstream of SW 34th Street Table of siw&lated-stages for the selected nts Resemmend ---form additional .,,,, lo4 ng 7- A No Fvry [nn•�-1U zi lb-4 p4ar cy,,,v""c1c_ SyST�... 4�k S) tS /3&l.16 >�c ✓N�LR /a S��(�°7� S�3c�,�r/th� T � '�iry� GAS-So- c��3 �oo /�v., wlT (( '), �-x T SU�rS WJ� 3/ Sv►+i /f�l��D /� TitE T����� � � o�aNnyn TO i3r- (AVTk,Atr Full 6,w,/,QM5dJ 7d 7"Gf � wrrN W6� ,ft,A—, 9144R -T frC 4NICI'1StS, S-�o nsgg-/ aY sn .pry c�o�1n�ri Y�L�►/ ,10 S 1r.lNd, 3'Y°v�1�'oS W41C7 "V) S)-SI)gVW rp�y�ipn� ram/ r1P's.V/ /., p. n-,oG S�o(Md �3 coo 0 �/ / NINJ IJ Y/ `/ �I J ��/IH 1-4 m-4 m NN fy',* eA 3'�ls �ki� Mo�y t7 �j S(I57 � MQ L v-pMn nv/ Nd Opp" nw/S yVy� • J __,j?FAX tAANSM1TTAL -- y Table III- ..3-. -- Interpretation of Inundation Data ..Elevation GREATER than or equal Critical Total Hours Analysed: 224016 Period of Analysis :11/ 9/1961 - 5/30/1987 using months 1 to 12 m Critical Depths 17.500 18.000 19.000 20.000 21.000 22.000 23.000 %t >= Critical 4.447 2.615 0.912 0.288 0.077 0.018 0.002 t >= Critical 9962 5859 2044 645 172 40 5 Total Events 427 273 103 35 10 5 1 Duration(hr) Events 3 402 256 99 35 10 5 1 6 356 230 89 30 10 3 0 9 292 188 75 28 8 3 0 12 260 154 57 22 6 1 0 18 191 110 46 15 5 0 0 24 135 90 32 12 1 0 0 30 111 70 24 7 1 0 0 36 91 51 15 4 1 0 0 42 74 40 12 2 0 0 0 48 56 29 7 1 0 0 0 60 32 18 2 0 0 0 -0 72 20 8 1 0 0 0 0 84 12 4 1 0 0 0 0 96 7 3 1 0 0 0 0 108 5 2 1 0 0 0 0 120 4 1 1 0 0 0 0 13232 4 1 0 0 0 0 0 144 4 0 0 0 0 0 0 156 4 0 0 0 0 0 0 168 2 0 0 0 0 0 0 18080 0 0 0 0 0 0 0 Notes: 1. Total no. of hours in analysis 2. Months (season) analyzed 3. Water surface elevation D 4. Percent of time water surface elevation exceeds D 5. No. of hours water surface elevation exceeds D 6. No. of discrete events in which water surface elevation exceeded D 7. No. of events in which water surface elevation exceeded D for a duration greater than T Example: There were 230 events in the period of analysis in which the water surface elevation was greater than +18 ft for a duration greater than 6 hours. Elevation GREATER than or equal Critical Total Hours Analysed: 56304 Period of Analysis :10/ 9/1961 - 5/30/1987 using months 1 to 3 Critical Depths 17.500 18.000 19.000 20.000 21.000 22.000 23.000 %t >= Critical 8.019 3.936 1.060 0.325 0.123 0.016 0.000 t >= Critical 4515 2216 597 183 69 9 0 Total Events 197 103 34 10 5 2 0 Duration(hr) Events 3 187 99 33 10 5 2 0 6 161 84 30 10 5 1 0 9 139 69 23 7 5 0 0 12 119 61 20 6 3 0 0 18 86 53 13 4 1 0 0 24 64 43 9 3 0 0 0 30 50 27 6 2 0 0 0 36 45 20 5 1 0 0 0 42 37 12 2 1 0 0 0 j 48 25 10 1 0 0 0 0 60 15 4 0 0 0 0 0 72 8 2 0 0 0 0 0 84 5 0 0 0 0 0 0 96 3 0 0 0 0 0 0 108 1 0 0 0 0 0 0 120 1 0 0 0 0 0 0 129 0 0 0 0 0 0 0 ..Elevation GREATER than or equal Critical Total Hours Analysed: 56040 Period of Analysis :10/ 9/1961 - 5/30/1987 using months 4 to 6 Critical Depths 17.500 18.000 19.000 20.000 21.000 22.000 23.000 %t >= Critical 1.394 0.439 0.068 0.000 0.000 0.000 0.000 t >= Critical 781 246 38 0 0 0 0 Total Events 58 22 4 0 0 0 0 Duration(hr) Events 3 56 21 4 0 0 0 0 6 42 15 4 0 0 0 0 9 31 11 2 0 0 0 0 12 23 8 1 0 0 0 0 18 17 6 0 0 0 0 0 24 8 2 0 0 0 0 0 30 7 1 0 0 0 0 0 36 3 0 0 0 0 0 0 42 1 0 0 0 0 0 0 48 1 0 0 0 0 0 0 57 0 0 0 0 0 0 0 ..Elevation GREATER than or equal Critical Total Hours Analysed: 55200 Period of Analysis :10/ 9/1961 - 5/30/1987 using months 7 to 9 Critical Depths 17.500 18.000 19.000 20.000 21.000 22.000 23.000 %t >= Critical 0.792 0.250 0.033 0.000 0.000 0.000 0.000 t >= Critical 437 138 18 0 0 0 0 Total Events 44 15 2 0 0 0 0 Duration(hr) Events 3 41 14 1 0 0 0 0 6 32 9 1 0 0 0 0 9 21 6 1 0 0 0 0 12 14 5 1 0 0 0 0 18 6 1 0 0 0 0 0 24 3 1 0 0 0 0 0 30 1 0 0 0 0 0 0 33 0 0 0 0 0 0 0 THE CITY OF RENTON DEPARTMENT OF PLANNING/BUILDING/PUBLIC WORKS ff 1 ""ffr 1 `"r"'f "' - f" vim ,,........ .. >f {s FOURTH FLOOR 200 MILL AVENUE SOUTH «y " f RENTON, WASHINGTON 98055-2189 FAX: 235-2541 .v: •:iiiiiir�vx�. To: Company: Phone: Fax: From: Scams w000go Company: Phone: 2-7,7 S'Sy� Fax: Date: Pages including this cover page: Comments: �L�AS46 ,moo G� wi�� nI7 641�- ,ter S• 7rR dry. (iwUU SEP 22 '94 07:49 NW HYDRAULIC CONSULT 684 P01 Y northwest hydraulic consultants inc . 22017 70th Avenue South Kent Washington 98032 206-872-0218 206-872-0518 fax FAX MESSAGE Date: 9 12 2 From: Larrw I�o.rcnck To: Company: i V 6,40A Fax #: City: Re- o� Pages to Follow: 5 Original in Mail: �. Please call immediately if you do not receive all pages of this transmission. sGop e and eet►`mode -�r• f h e l an $anl� Sic 6�ud u se call aT+tr p u h i%t Inad c chonce '$'o rev►e� tln�s . � �i � � �5e out �U SEP 2 21994 CITY OF RENTON Engineering Dept. SEP 22 '94 07:50 NW HYDRAULIC CONSULT 684 P02 Exhibit A - Scope of Work&,,M, .ram lorWetland anking East Side Green River Watershed Project administrado i cludes quality control, invoicin a control, miscellaneous client contacts, work sum emoranda, effort related to the administration of this contract. Products: Monthly invoices and work summaries, and quOty-assurance on all work products I Task $�- Preliminary Modeling Northwest Hydraulic Consultants (NHC) will modify ourAuture land-use/current conveyance system HSPF model of Springbrook Creek to account for additional storage proposed at Wetland Mitigation Bank Site 2 near Oakesdale Avenue and SW 34th Street. Note that the attached estimate assumes that the current conveyance system HSPF model being developed for the ESGRWP will be available for use in this study. Quantification of the stage/volume relationship for the proposed bank site will be provided by the City of Renton. For preliminary modeling, the inflow/outflow effects of the wetland banking site will be assumed to be negligible (i.e. flows will be assumed to pass freely into and out of the bank site withouj h�draul,c c�orstrai�nt)k NHC +,ks will perform long term simulations for water years 1961-19917.er &fir S' ring�rbWV' ree�C" s� a� System with the existing conveyance system and with the proposed additignal off-channel storage w 3yra provided by the wetland bank site, �Qr �� ,s C'J AN"t uf� e rmme 6 '. vw, requency-quantt es - r $prinvbroolt (`rc lr. .pf S._34th StreeLW&_aAd t. NHC-w4H-eIs"se-=-exisdng-HEC-2-mo&t-to compute-depths of`flow'artht-upsgca fvrup-to-four everrts-with-arf--without--the-prepesed-pre*t. These-.events--tray coincide with the 2-, 10 and 25- year events and the maxis-umr--evvenl of record.or they may be chosen to characterize the impact of the banking site on a pardruiar-flew eeee eveY:' 1[ezlfofce bf evens 'tt`tad�-I—_IL ' gs of g. BAsed on these preliminary HSPF and HEC-2 modeling results a recomffiendadon to the City of Renton-on whether.of-n orm more detailed hydraulic and hydrologic modems gnattttf--the expected benefit, in terms of flood peak and stage reduction, ti frem-iffe proposed ban ect. a �!%4� � �iyfyrc �h7�-'�S��CNrLnA' GrnVCy�n�t Products: HSPF models (version 10) of the ievow Springbrook Creek system with and without the proposed project Frequency plots for Springbrook Creek upstream of SW 34th Street Table 1 �euents ReGG Tlf1Sn11Q1L1An-AT u,hPthPr nr no o perform add itinnal WQjaping L� srisrs>canysciz >. a ■v vaxxxc• r� t NAT 7-Hi G--M/#16 ,,ND G-rvAA 4AtV!9-vSi_1I.uW*jr c,,t,*m"ch !0�Ic StTi 15 voob (/moEa 4 5'¢1,mP.A I t"vdcv)"r/th 7L/E r-try� GAG-`l0-U33 itoo /�v.v, mud. S, CoNTU,4cr L'�//Td (Z'W, /5're T141 05UI,r f 7 kaVAi t CA,t� r of dNn. TU 6 if �4V)"' VNo 6A 7/4Ir 1.AAgkAtr FaA- Tv 7 1 N whrp W4rfLA fl rr.1.Fi(A I*j • lac �,c,� ��,�purr .�N J v urVOA7I41�) S/S (JN�9f-� (T�i•✓6 ,q-,�o /`Mall 6-OW ✓Jl���N1'. 7,�+f I&Suar 5�r.41-u, ___ w 0 W o n �iY/�-!1 T 19f l G t D� Sl'� G E S' /nl 7-iM a v a rrr M M M •a Aix /�4� • ��C,U r�vj /�S' AIVO UUfiS OI` ,Avt Gcvv /U'l¢/l �N/v/' /DU7Pul 065 (-,J) Puy GI of S o-j ? %z' �)/sue. I`CHNI C4 L vh a DbW SUPh/KA Pit 21,j 6 Tr�� �S��s SEP 22 '94 07:50 NW HYDRAULIC CONSULT 604 P03 Exhibit A - Scope of Work Page 2 Task 3 - SuRRIemental Mode!Lng If tXFTAB to perform more precise hydraulic and hydrologic modelling of the pro sed promodify our existing conditions HEC-2 model of Springbrook Creek to ccount for associated with the proposed wetland mitigation bank. Note th this is an itehich involves concurrent modification of the HEC-2 and H models to cos for use in the HSPF modeling. Upon completion of FTABLE development NHC will rerun the wi roject long runs and update the frequency an sis and flow depth computations. NOTE: As an alternative to iterative solution using HSPF and C-2 it may be more appropriate to update the portion of a City's FEQ model of Sprin rook Creek between Oakesdale and SW 34th Street to invests to the effects of the p posed banking project. If NHC were provided with the existing ode1, it would possible to perform these updates for approximately the same budget is includ for the HEC-2 modeling (we would need to review the exact construction of the EQ del before providing a precise cost estimate for modifications). As an alternative to performing this work, the City may find it more expedient to request that RW Be p orm this work under their existing ESGRWP Contract. Products: HSPF models (version 10 of the lower Sprin rook Creek system with and without the proposed project Frequency plots fo pringbrook Creek upstream f SW 34th Street Table of simulat stages for the selected events Task 4 - s nta ' of Results If the proposed pr 'ect provides peak flow and/or flood stage reductions, the City of Renton deems a report be necessary, NHC will prepare a formal report on our r onnaissance level findings. T ' report will document our procedure and assumptions and pro ' e a discussion of un inherent in the analysis. The report will also discuss any follow u work which will be n ssary to quantify benefits from the proposed project. Our budget includ a several hours r presentation of the results to the City, either in a meeting or via a conferen call. ductsi Brief technical report Exhibit B- Cost Estimate ESGWP Gaging Services M Cost Estimate for Wetland Banking Reconnaissance Study Iv ry Direct Labor A m Number Units Unit Cost Total Cost cn Principal Hours 10 hrs 40.38 $403.80 Engineer Hours 64 hrs 22.21 $1,421.44 � Technician Hours 4 hrs 17.67 $70.69 = Clerical Hours 9 hrs 14.13 $127.17 D c Direct Salary $2,023.09 n 0 Overhead 165.0% $3,338.10 c Net Pee 12.0% $643.34 Sub-total $6,004.53 Other Direct Costs Number Units Unit Cost Total cost Truck Rental 0 Days $35.00 $0.00 Truck Mileage 0 Miles $0.35 $0.00 A Reproduction expenses (copies) t00 Copies $0.10 $10.00 IS Equipment rental for discharge measurements 0 Each $20.00 $0.00 m Miscellaneous direct expenses 1 Lump Sum $25.00 $25.00 Sub Total $35.00 Grand Total $6,039.53 Exhibit B - Cost Estimate ESGWP Gaging Services-Revised Hourly Rates effective July 1,1"4 M N N w A Hourly m Rates i.i, r Position (S) Project Manager 40.38 E Senior Engineer 27.01 Engineer 22.21 D Jr. Engineer 17.67 C Technician 17.67 Jr. Technician 13.63 0 Clerical 14.13 c F- --+ m 0 A m Ln Exhibit B - Cost Estimate ESGWP Consulting Services CO Task Breakdown for Wetland Banking Reconnaissance Study N N Task Hours by Sub-Task Cost Task Cost A Task Description KML LMK ETV PDP ($) ($) m i Project Administration 4 $263.68 $263.68 N I1 Preliminary Modeling z A. Estimate Stage/Storage Characteristics for Wetland Banking Site (See Note) B. Modify HSPF Model FTABLEs 2 $131.84 X C. Perform Long Simulation Runs (existing conditions) 4 $263.68 D. Perform Long Simulation Runs (with banking site) 4 $263,68 E. Flow Frequency Analysis 2 4 $503.37 (� F. Stage Analysis For Specified Event(s) 4 $263.68 0 G. Present Preliminary Findings 2 4 2 4 $776.01 $2,202.26 M Potential Supplemental Modeling H. Update HEC-2 Model Using Revised Flows (iterative) 12 $791.03 1. Re-run Long HSPF Model Run With Banking Site 4 $263.68 J. Flow Frequency Analysis 2 4 $503.37 K. Stage Analysis For Specified Event(s) 4 $263,68 $1,821.76 IV Presentation of Results L. Report 4 12 2 4 $1,543.06 01 M. Presentation of Findings (meeting or conference call A ( S ) 2 1 $173.78 $1,716.84 T v m NOTE:Estimate assumes thal the City of Renton will supply the necessary Stage/Volume characteristics for the wetland banking site Personnel: KML- Leytham- Principal Engineer Total $6,0(}4.53 LMK- Karpack - Staff Engineer ETV -Vandermeer-Senior Technician PDP - Phillips - Clerical DRAFT Wetiand Mitigation Banking Plan City of Renton 1 ' Prepared for City of Renton 200 Mill Avenue Renton, Washington 98055 ' Prepared by Parametrix, Inc. 5808 Lake Washington Blvd. NE, Suite 200 Kirkland, Washington 98033 1 (425) 822-8880 www.parametrix.com January 2001 ' Project No.553-1779-009 TABLE OF • EXECUTIVE SUMMARY..................................................................... ........................IV ................................ 1. INTRODUCTION........***.....*.........*"***........ ...............*........ NTRODUCTION........................................ ........................ 1. PROJECT DESCRIPTION AND LOCATION...................................................................................2-1 1.1 PROJECT DESCRIPTION..................................................................................................2-1 1.1 SITE DESCRIPTION..........................................................................................................2-1 1.1 OWNERSHIP......................................................................................................................2-1 1.1 RESPONSIBLE PARTIES..................................................................................................2-1 1.1 RATIONALE FOR CHOICE..............................................................................................2-4 1. EXISTING CONDITIONS AND FUNCTIONS THE MITIGATION BANKING SITES.......................3-1 1.1 MITIGATION BANK SITE 1.............................................................................................3-1 1.1.1 Wetland Delineation...............................................................................................3-1 1.1.1 Vegetation Communities........................................................................................3-3 1.1.1 Soils, Hazardous Material and Geotechnical Information......................................3-3 1.1.1 Hydrology...............................................................................................................3-4 1.1.1 Functional Assessment........................................ ......... ............3-5 1.1.1 Wetland Rating.......................................................................................................3-7 1.1 MITIGATION BANK SITE 2.............................................................................................3-7 1.1.1 Wetland Delineation...............................................................................................3-7 1.1.1 Vegetation...............................................................................................................3-7 1.1.1 Soils,Hazardous Material and Geotechnical Information......................................3-8 1.1.1 Hydrology...............................................................................................................3-9 1.1.1 Functional Assessment...........................................................................................3-9 1.1.1 Wetland Rating......................................................... ........................................3-11 1. MITIGATION APPROACH ...............................................................................................................4-1 1.1 MITIGATION SEQUENCING...........................................................................................4-1 1.1 MITIGATION PLAN GOALS, OBJECTIVES,AND PERFORMANCE STANDARDS .....................................................................................................................4-1 1.1.1 Mitigation Banking Site 1.......................................................................................4-1 1.1.1 Mitigation Banking Site 2.......................................................................................4-2 1.1 PERFORMANCE STANDARDS.......................................................................................4-3 1.1.1 Mitigation Banking Site 1.......................................................................................4-3 1.1.1 Mitigation Banking Site 2.......................................................................................4-4 1. PRELIMINARY SITE PLAN ---...*,,,**...**...*........,...**.....**.....—..........*...... ,"***......... LAN ........................................................................................ ' 1.1 TOPOGRAPHY...................................................................................................................5-1 1.1 SOURCE OF WATER........................................................................................................5-1 1 1.1 SOILS..................................................................................................................................5-1 1.1 PROPOSED PLANT DISTRIBUTION..............................................................................5-4 1.2 SECTION DRAWINGS......................................................................................................5-5 City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan i January 2001 IIKIRKLAND_II VOL]DATAI workingV 770554-1779-07WIT BANK PLAN-revue part It 1-01.doc TABLE OF • • - • 1.3 PUBLIC ACCESS...............................................................................................................5-5 2. MONITORING PLAN........................................................................................................................6-7 2.1 VEGETATION....................................................................................................................6-7 2.2 WATER REGIME...............................................................................................................6-7 2.3 SOILS..................................................................................................................................6-7 2.4 FAUNA............................................................................................................................... 6-8 2.5 DEVELOPMENT OF HABITAT STRUCTURE...............................................................6-8 2.6 BUFFERS............................................................................................................................6-8 2.7 SCHEDULE OF REPORTING MONITORING RESULTS..............................................6-8 3. SITE PROTECTION .........................................................................................................................7-1 3.1 LEGAL PROTECTION ......................................................................................................7-1 3.2 MAINTENANCE AND CONTINGENCY PLAN.............................................................7-1 4. IMPLEMENTATION..........................................................................................................................8-1 5. PERFORMANCE..............................................................................................................................9-1 6. REFERENCES ...............................................................................................................................10-1 GLOSSARY..................................................................................................................................................1 City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan ii January 2001 IIKIRKLAND—IIVOLIIDATAIw rkingU779U54-1779-07WTBANKPLAN-revise part 111-OLdoc TABLEOF •NTENTS (Continued LIST OF FIGURES 1 Location of Mitigation Banking Sites 1 and 2.....................................................................1-2 2 Existing Site Conditions on Mitigation Banking Site 1.......................................................2-2 3 Existing Site Conditions on Mitigation Banking Site 2.......................................................2-3 4 Soil Characteristics of Mitigation Banking Site 1...............................................................3-1 5 Soil Characteristics of Mitigation Banking Site 2...............................................................3-2 6 Proposed Site Plan for Mitigation Banking Site 1...............................................................5-2 7 Proposed Site Plan for Mitigation Banking Site 2...............................................................5-3 ILIST OF TABLES 1 Summary of Functional Evaluation of Wetlands on Mitigation Banking Site I.................3-5 2 Summary of Wetland Functions Provided by Mitigation Banking Site 2...........................3-9 3 Candidate Plant Species Proposed Wetlands and Buffers...................................................5-4 4 Proposed Schedule for Monitoring City of Renton Mitigation Banking Sites....................6-9 rAPPENDICES A CITY OF RENTON WETLAND MANAGEMENT ORDINANCE B WETLAND FUNCTIONAL EVALUATION FORM AND INSTRUCTIONS TO USE FORM C PHOTOGRAPHS OF SOIL TESTS LOCATIONS ON MITIGATION BANKING SITE 2 D COMPLETED WETLAND FUNCTIONAL EVALUATION FORMS FOR MITIGATION BANKING SITES 1 AND 2 City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan iii January 2001 IIKIRKLAND_I I VOLT IDA TA I workingl 17791554-1779-07MIT BANK PLAN-revise part 111-01.dac EXECUTIVE SUMMARY This Mitigation Banking Plan describes development wetland ecosystems two sites as part of a City of Renton (hereafter referred to as the City) mitigation-banking program. The Mitigation Banking Plan is a method by which high function wetlands are created contiguous with other significant habitat in the Black River Drainage Basin to offset the loss of isolated, low function wetlands that may occur through private and public development. The mitigation-banking program and plan are consistent with the City's Wetland Management Ordinance and Comprehensive Plan. The banking plan provides a solution that preserves or I enhances wetland and ecosystem functions while allowing economic growth in compliance with the state of Washington's Growth Management Act. This report provides a conceptual design approach for establishing wetlands and wetland banking credit on to parcels as part of the City's planned mitigation bank. The plan is conceptual because it remains subject to several variable such as finalization of wetland banking rules for Washington State, potential changes to Army Corps of Engineers jurisdiction of isolated wetlands, and review by permitting agencies ' for Clean Water Act and Endangered Species Act compliance. Two mitigation bank sites are proposed: Mitigation Banking Site 1 (Site 1)and Mitigation Banking Site 2 (Site 2), total about 44 acres. Site 1 (about 31 acres) is north of SW 34th Street, south of Boeing Longacres Park, east of Burlington Northern Railroad, and west of Oakesdale Ave. SW. The site consists ly of 12 acres of non-wetland and about 19 acres of emergent, scrub-shrub, and shrub-young forested wetlands. Site 2 (about 14 acres) is located south of SW 34th Street, west of Springbrook Creek, north of SW 40th Street and east of Oakesdale Avenue SW. The site consists of about 7 acres of upland and 7 acres of emergent and scrub-shrub wetlands that developed on fill. iThe Mitigation Banking Plan provides a preliminary wetland mitigation design for the mitigation banking sites. A discussion of existing conditions at each mitigation-bank site including vegetation, soils, and hydrology is included, and provides baseline information to use to compare with post-project construction conditions. The results of the existing conditions assessment indicates that both sites;have been impacted by historic and recent clearing, filling, and grading activities. The existing wetlands are defined as Category 3 wetlands by the City of Renton's categorization for wetlands. The mitigation plan's goal for both sites is to establish a total of about 20 acres of wetland containing four wetland classes. Upland buffers would protect these wetlands. The mitigation will enhance existing wetland functions by providing habitat and food chain support to terrestrial and aquatic wildlife, habitat connectivity, storm and flood water attenuation, downstream water quality improvements, public access, and shoreline stabilization. To accomplish this desired goal, approximately 10 acres of emergent, scrub-shrub and forested wetlands will be established on Site 1 and,for Site 2,approximately 10 acres of open-water,emergent, scrub- shrub, forested wetlands, and transitional buffer. On both sites, the enhancement of existing lower quality wetland or low quality upland buffers should improve wetland function and generate additional mitigation ' credit. The draft mitigation plan specifies mitigation objectives, performance standards, and the methodology to measure whether these standards are met. These objective and standards were developed based on site assessments of wetland functions and potential mitigation opportunities, including; soils, hydrology, vegetation, habitat, flood and storm water attenuation, water quality improvements, public educational and passive recreation. During the 10-year monitoring period,the development of the wetland and buffer plant communities, habitat structure, and other ecological conditions will be measured. Additionally, hydrology, soils,topography, and City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan iv January 2001 IIKIRKLAND_lIVOLIOATAIworkingV779155d-1779-071MITBANK PLAN-revise part ll I-Ol.doc vegetation will be monitored to ensure that they are meeting design criteria. The proposed schedule for monitoring will require preparation of an as-built report after construction and annual reports that will be submitted to the City of Renton. In addition, if, during the monitoring program, maintenance needs and/or contingency actions are identified that are required to ensure the success of the mitigation plan, they will be implemented. A draft implementation schedule must be developed for the mitigation bank. An anticipated schedule is the final wetland mitigation-banking program,,plan, and final draft site designs will be completed by It is anticipated permit approval by will be achieved by and construction would start by The construction period is anticipated to be about months. City of Renton 553-1779-009 Draft-Welland Mitigation Banking Plan v January 2001 II KIRKLAND_11 VOL]IDATAI working)I7 791554-1 779-0 71MIT BANK PLAN-revise part 111-01.doc I ' 1. INTRODUCTION ' The Mitigation Banking Plan will establish wetland communities at the two mitigation banking sites. The mitigation plan includes information generally needed by regulatory agencies to review wetland mitigation plans. The information contained in this plan is generally follows the format provided by ' Ecology(Washington Department of Ecology 1993)for mitigation plans. This report provides a conceptual design approach for establishing wetlands and wetland banking credit on to parcels as part of the City's planned mitigation bank. The plan is conceptual because it remains subject to several variable such as finalization of wetland banking rules for Washington State, potential changes to Army Corps of Engineers jurisdiction of isolated wetlands, and review by permitting agencies for Clean Water Act and Endangered Species Act compliance. ' The final wetland mitigation plan will provide detailed plans, construction drawings, specifications and final schedules. The City of Renton (hereafter referred to as the City) and a larger body of technical and ' regulatory specialists will review the draft final plan. Input from these specialists will be incorporated into a final plan thereby increasing the probability of attaining the projects ecological goals. The wetland Mitigation Banking Plan will create large, high function, contiguous wetlands adjacent to Springbrook Creek in the Black River Drainage Basin(Figure 1). These mitigation wetlands will be used to offset filling of isolated, low function wetlands that may result from private and public development in the same drainage basin. Approximately 10 acres of emergent, shrub, and forested wetlands would be established on the existing uplands on Mitigation Banking Site 1 (see Figure 1). Approximately 2.5 acres of existing wetland would ' be altered and enhanced by construction of the mitigation. The modification of these existing wetlands is necessary to establish new wetland communities and provide the desired ecological functions specified for this site. About 15 acres of existing forest and shrub wetland on the site could be enhanced to 1 generate additional mitigation credit. The specific functions established by this mitigation are biological support, floodwater storage, water quality enhancement, wetland education opportunities, and passive recreation opportunities. ' On Mitigation Banking Site 2(see Figure 1),approximately 10 acres of open water, emergent wetland,scrub- shrub wetland, forested wetland, and upland buffer area would be established. To construct Mitigation I Banking Site 2, about 7 acres of wetland and 7 acres of upland plant communities occurring on fill soils would be modified as the site is graded to create the desired habitat conditions. The functions to be provided at Mitigation Banking Site 2 are biological support, floodwater storage/desynchronization, nutrient and sediment trapping, and shoreline stabilization. Opportunities for passive recreation and education are also included in the proposed site plan. s-53 The City will use about-4-IT-a--cres to compensate for permitted filling of wetlands on some Glacier Park properties. The additional property will be available as mitigation banking credits to offset approved wetland fill elsewhere. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan I-1 January 2001 IVORKLAND_1IVOLIIDATAIworking11779US4-1779-07MIT RANK PLAN-revise part 111-01.doc Figure r1 Location of Mitigation Banking Sites 1 and 2 r City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 1-2 January 2001 ' IWJUMAND_II VOL]DATAiworldng11770554-1779-07WIT BANK PLAN-rMse part II I-Ol.doc 2. PROJECT DESCRIPTION • • 2.1 PROJECT DESCRIPTION The City proposes to develop two wetland mitigation banking sites (called Mitigation Banking Site 1 and ' Mitigation Banking Site 2) totaling 44.80 acres. These sites are to be used for compensatory wetland mitigation for the six parcels originally under Glacier Park ownership (see Figure 1), and for mitigation banking by other public and private.developments to offset losses to lower quality wetlands. Specifically, I Mitigation Banking Site 1 can provide 10 acres of wetland mitigation banking credit. As proposed, Mitigation Banking Site 2 will provide 10 acres of wetland mitigation banking. Additional credit may be assigned to these sites as a result of upland and wetland enhancement actions. 2.2 SITE DESCRIPTION ' Mitigation Banking Site 1 is located.north of Southwest 34'd Street, south of Boeing's Longacres Park site, east of the Burlington Northern Railroad, and west of Oakesdale Avenue Southwest (Figure 2). The site is 30.97 acres and is partially zoned industrial. It is bordered by developed land zoned for industrial ' development along most of the southern boundary. Undeveloped commercial and industrially zoned land is adjacent to the western half of the southern boundary and to the eastern and western boundaries(David Evans and Associates 1991a). The site consists primarily of revegetated fill material,placed approximately 20 years ago, consisting of 12.19 acres of upland meadow and shrubland and 18.78 acres of shrub and emergent ' wetlands(confirmed by the Army Corps of Engineers 1996). Mitigation Banking Site 2 is located south of Southwest 34th Street, west of Springbrook Creek, north of ' Southwest 40th Street, and east of Oakesdale Avenue Southwest(Sec 25, T 23N, R 4E)(Figure 3). The site is approximately 13.93 acres and consists of 7.24 acres of upland meadow and 6.69 acres of emergent and young shrub and forested wetland(David Evans and Associates 1991b). The site was filled over the past 20 years; the topography is relatively flat with small depressional areas. It is bordered to the north by undeveloped industrial and commercially zoned land. ' 2.3 OWNERSHIP The City of Renton is the sole owner of the two mitigation-banking sites. As the City developed its Wetlands Management Ordinance, Burlington Northern (BN) decided to divest some properties held by the Glacier Park Company, a subsidiary to BN. BN also wanted to improve the market value of some of its Valley properties. After meeting with the City to develop a mitigation banking agreement,Glacier Park donated two ' large parcels(see Figure 5)that contained wetlands to the City. 2.4 RESPONSIBLE PARTIES The applicant is the City of Renton, 200 Mill Avenue, Renton, Washington 98055. Contacts at the City of Renton are Mr. Ronald Straka, and Mr. Allen Quynn, Department of Public Works, Surface Water Utility. David Evans and Associates, Inc. delineated the wetlands on the mitigation banking sites, which were confirmed by the US Army Corps of Engineers in 1996. Parametrix is assisting the City with preparing the mitigation banking program and plan. 1 City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 2-1 January 2001 11KIRKLAND_11 VOL11DATA4orkinel7 791554-1 779-0 7MIT BANK PLAN-revise part 171-01.dn Figure 2 Existing Site Conditions on Mitigation Banking Site 1 1 City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 2-2 January 2001 IIKIRKLAND IIVOLIIDATAI»+orEngl1 7791554-1 7 79-071MITBANKPLAN-revise part III-01.doc Figure 3 Existing Site Conditions on Mitigation Banking Site 2 ' City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 2-3 January 2001 IIKIRKLAND_IIVOLIIDATAIwvr*ing11 7 791554-1 779-0 71MIT BANK PLAN-revise part 1I 1-01.doc 2.5 RATIONALE FOR CHOICE ' Glacier Park donated the mitigation banking sites to the City of Renton as part of a mitigation banking agreement between the City and Glacier Park. The two sites are appropriate as mitigation banking sites for ' several reasons. Ecological functions on both sites are degraded by past disturbances that include vegetation clearing, fill placement, hydrologic modification, and other disturbances. The sites are adjacent to Springbrook Creek(Site 1) or to other wetlands that are adjacent and hydrologically connected to the creek (Site 2), and their restoration as wetlands would contribute to function of these systems that provide an ecological corridor through much of the Renton Valley(see Figure 1). Improvements made to the vegetation communities and establishing specific wetland functions would result in a net gain in wetland acreage, habitats and functions. Both sites have the capability of providing wetland functions that will significantly benefit the City of Renton and the public. For example, the City of Renton identified storm andflood water attenuation as an important issue in the Black River Drainage Basin. Mitigation Banking Sites 1 and 2 can provide significant floodwater control that would minimize impacts to downstream areas. In addition, Mitigation Banking Site 1 is adjacent to protected wetlands to the north and east. Mitigation Banking Site 2 immediately borders Springbrook Creek and its associated city-owned wetlands(i.e.Panther Creek Wetland). ' Both sites have been altered by filling,ditching, and diking over the past 20 years,and their ability to provide functions important to the landscape and Black River Drainage Basin is limited to non-existent. Wetlands established on these sites could improve the hydrologic and ecological condition of the Black River Drainage ' Basin by increasing storm and flood water storage capacity, enhance habitat corridors, provide biological support functions,and enhance water quality. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 2-4 January 2001 IWAKLAND_II VOLIIDATAIworking11 7 791554-1 779-0 7UHT BANK PLAN-revise par!II I-01.doc A 1993 field assessment of the two mitigation banking sites indicated that both sites contain relatively low- value seasonally perched wetlands that are generally composed of cottonwood, Populus balsamifera; red alder, Alnus rubra; salmonberry, Rubus spectabilis; willow, Salix spp.; and reed canarygrass, Phalaris arundinaceae. The wildlife habitat value of the mitigation banking sites is limited by lack of habitat structure, wetland classes, and buffers; although the wildlife habitat value of the large wetland on Mitigation Banking Site 1 (see Figure 2) appears to be greater than that value at Mitigation Banking Site 2 (see Figure 3). Both sites support immature deciduous trees. Consequently,habitat for many native wildlife species(e.g. cavity-nesting birds) are limited. The relatively young age of the forested portions of both sites and the relatively low species diversity within the plant communities limit the value of these sites for wildlife. In addition, there are few, if any, permanently wet areas on either site. The existing wetlands are seasonal in character and possess relatively low functional capacity for floodwater storage and water quality improvement. The wetlands are also artificial(i.e.developed on nearly level areas or shallow depressions on top of fill)and occur at elevations 5 to 9 feet higher than neighboring water bodies(e.g., Springbrook Creek) and historical ground surface. Both sites have large areas in which reed canarygrass and introduced blackberry species (Rubus discolor- , procera, R lacianatus)have become established. Both sites also have areas in which Scots broom (Cytisus scoparius)grows. These undesirable plant species will continue to expand their abundance unless shaded by taller vegetation,removed,or otherwise controlled. Mitigation Banking Site 2 shows less evidence of human use, but Mitigation Banking Site 1 is frequently used by off-road vehicles, an activity that has resulted in significant disturbance to the landscape despite efforts by the City to restrict entry for this purpose. A significant amount of fill has been placed on both sites, with the depth of fill as great as 10 ft in some places. This material generally has low organic content and consists of a variety of textures. Where clay and silt contents are relatively high, seasonally perched water is present. Although soils in the wetland areas show signs of mottles,the soils may not have been hydric when deposited. Using a backhoe, three soil test ' technician dug holes on Mitigation Banking Site 1 and five on Mitigation Banking Site 2. The soil test locations are shown in Figures 2 and 3, and the results are presented in Figures 4 and 5. Photographs of the soil test locations are provided in Appendix C. ' 3.1 MITIGATION BANK SITE 1 ' Mitigation Banking Site 1 is 30.97 acres; its northwest corner is within the 100-year floodplain of Springbrook Creek and the Green River. Approximately one-third of the site has been cleared,or cleared and filled,over the past several years. In about 1975 the site was cleared of all trees, and a historical meander of Green River on the site was filled, creating localized wetlands(Hart Crowser 1991 a). Farming appeared to be the predominant activity on the site until the early 1980s. ' 3.1.1 Wetland Delineation Three wetland areas were identified and delineated on Mitigation Banking Site 1; ranging from 0.14 to 17.91 acres in size(David Evans and Associates 1991a; see Figure 2). The wetland communities typically occur in ' the relatively undisturbed areas, and the majority of upland communities occur in elevated areas that have been more recently filled. Topography on the site ranged from an elevation of 18 to 20. Wetland J is a 0.14- acre scrub-shrub wetland, Wetland L is a 0.73-acre scrub-shrub wetland and wetland M is a 17.91-acre emergent, and scrub-shrub, and shrub-young-forested wetland. The wetland boundaries were confirmed by the ACOE in 1996. ' City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-1 January 2001 ' IVORKLAND_II VOL IIDATAIworking11 7 791554-1 779-0 7MITBANKPLAN-revise part 11I-01.dw Figure 4 Soil Characteristics of Mitigation Banking Site 1 i City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan 3-1 January 2001 HKIRKLAND_II VOL]DA TA IwarkingV1 7 791554-1 7 79-0 71MIT BANK PLAN-revise part 111-01.doc Figure 5 Soil Characteristics of Mitigation Banking Site 2 City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-2 January 2001 IIKIRKLAND_II VOLIIDATAIworkingII7 791554-1 7 79-0 71MIT BANK PLAN-revise part 111-01.doc 3.1.2 Vegetation Communities jSeveral vegetation communities occur on the site; these include upland meadow and shrub communities, a wet meadow, and scrub-shrub and shrub-young-forested wetland (see Figure 7). The upland meadow communities are variable in species composition, but in general are dominated by upland and facultative upland species. Species common to the upland meadow community include: creeping bentgrass, Agrostis stoloneifera; English plantain,Plantago lanceolata, velvet grass,Holcus lanatus; common tansy, Tanacetum vulgare; hairy cats-ear, Hypochoeris radicata; soft chess, Bromus mollis; and Canada thistle, Cirsium arvense. (David Evans and Associates 1991a). The upland shrub community consists primarily of Himalayan blackberry and Scot's broom (David Evans and Associates 1991a;personal observation, Parametrix 1993). The Himalayan blackberry stands are almost impenetrable and reach up to 15 ft tall. The blackberry stands have overgrown vegetation described above in the upland meadow community,and below in the seasonally wet meadow community. The seasonally wet meadow portions of on-site wetlands are dominated almost exclusively by reed canarygrass (David Evans and Associates 1991a; personal observation, Parametrix 1993). Secondary vegetation within the wet meadows includes creeping bentgrass and common velvet grass. The scrub-shrub and shrub-young-forested wetland community is dominated by young willows and black cottonwood with some western crab apple,Malus fusca;red-osier dogwood, Cornus stolinifera; and Douglas spirea, Spirea douglasii. The herbaceous layer consists of creeping bentgrass, creeping buttercup, Ranunculus repens,soft rush,Juncus effusus,and common horsetail,Equisetum arvense. 3.1.3 Soils, Hazardous Material and Geotechnical Information 3.1.3.1 Soils The Soil Survey for King County (Snyder et al. 1973) mapped three different soils on Site 1: Puyallup fine sandy loam, Woodinville silt loam, and Puget silty clay loam(Figure x) Puyallup fine sandy loam is a well- drained sandy loam soil formed in alluvium generally found on natural terraces adjacent to streams in valleys. Puget soils are non-hydric, however, hydric inclusions of Woodinville and Puget soils can occur. Woodinville silt loam is a hydric soil composed of poorly drained material. These soils formed in alluvium on stream bottoms.This soil ranges from silt loam to silty clay loam with thin lenses of very fine sandy loam and loamy sand or peat. avid Evans and Associates (1991a) confirmed this soil unit on the western, northwestern, and eastern portions of the site. The third soil unit, Puget silt clay loam, is a hydric soil which developed in small depressions in river valleys. The soil contains silty clay loam to silt loam stratified with silt loam, silty clay, and fine sand. This soil unit is mapped in a small portion of the site along the western edge within the historic influence of the Green River. Fill soils occur on a approximately one-third of the site,with the thickness of fill ranging from 12 to 48 inches in depth. A 4-foot-high mound of fill material covers approximately 1 acre in the southeast portion of the site. 3.1.3.2 Hazardous Materials A preliminary environmental site assessment indicated that the source of fill material brought onto Mitigation Banking Site 1 to fill the meander is unknown without further investigation (Hart Crowser 1991a). The chemical constituents of this fill material are also unknown. A second environmental site assessment City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-3 January 1001 IIKIRKLAND_IIVOLIIDATAIw rking11 7791554-1 7 79-0 71MITBANKPLAN-revisepartll1-01.doc prepared by Golder and Associates (1992), observed that there was no obvious evidence of significant dumping or related chemical contamination on the site. ' 3.1.3.3 Geotechnical Information Several evaluations of soil conditions have been made at the mitigation site. Available data includes the Soil Conservation Service soil survey (1973), test pit data collected by Parametrix, Inc(1993), Dames & Moore (1995)and Hong West(1997). Soils at three locations on Mitigation Banking Site 1 in the summer of 1993 by Parametrix. Soil at test location 1 excavated near wetland flag M-51 (David Evans and Associates 1991a [see Figure 2]) was at a ground surface elevation of approximately 18 ft(see Figure 4). Fill occurred from the surface to an elevation of about 16 ft and consisted of a silty sand, with prominent mottles. Below the fill, soils consisted ofa fine silty sand. The water table occurred at about 9 ft,(9 ft below the ground surface). Test location 2 was excavated in the northwest comer of the site at a ground elevation of approximately 18 ft (see Figure 2). At this site,soil characteristics were similar to those observed in test location 1 (see Figure 4). Fill occurred from the surface to an elevation of about 16 ft. Saturated silty sand mixed with mottles and fill occurred below 16 ft. At an elevation of about 11 ft the sediment was primarily silty sand. The depth of fill was estimated to be at least 5 ft. Soil test location 3 was excavated in the southeast corner of the site at a ground elevation of approximately 18 ft (see Figures 2 and 4). Fill occurred from the surface to an elevation of 16 ft. Below 16 ft was a 3/4 inch deep iron oxide layer followed by a silty fine sand fill layer. Woody debris (natural) was observed at 14 ft. Water seepage was evident at 7 ft. The depth of fill was estimated to be at least 4 ft. Dames &Moore (1995) conducted a geotechnical investigation of the Site 1 which included examination of sub-soil conditions in 5 test pits. Fill was located in test pits 1, 3, and 4 and ranged from 2 to 3 feet in thickness. The fill materials consisted of gravel,silty sand, and silt. The fill soils were underlain by native soils which include interbedded layers of silt, silty sand, and sand. In general, the upper 4 to 10 feet of deposits is a soft silt underlain by sand. An exception to this general condition occurred in the center of the site,where the surface fill material was underlain by sand(test pit#3). 3.1.4 Hydrology The existing wetlands on Mitigation Banking Site 1 are maintained by direct precipitation. A north-south oriented drainage ditch near the west edge of the site provides surface drainage for property located south of the site and portions of the site itself,but does not overflow into wetlands. This ditch contains standing water for much of the year. Monitoring well and test pit data indicate that seasonally high groundwater remains several feet below the surface when at its highest level (late winter). Water leaves Site 1 through evapotranspiration,infiltration,or surface runoff to the drainage ditch. Site 1 is located within an approximately 300 acre subbasin that is tributary to Springbrook Creek. Flows within the subbasin pass outlet through an 18-inch culvert located at the eastern edge of Wetland W-12a. This culvert passes through the fill of an old road bed (constructed in the 197O's) which generally blocks outflow from Wetland W-12a. At its lowest point, the top of the berm is elevation 14.6, and except under extreme flood events (such as occurred on February 8, 1996) the berm prevents floodwaters of Springbrook Creek from entering wetland W-12a. Water levels in wetland W-12a upstream of the culvert have been monitored on a monthly basis since March 1994. Based on the crest stage data for wetland W-12a and the rating curve for the 18-inch culvert outlet City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-4 January 2001 II KIRKLAND_11VOLIIDATAImrkingll7 791554-1 7 79-0 71MIT BANK PLAN-revise part 111-01.doc 1 from the wetland, the normal flow for the approximately 300 acre subbasin averages nearly 1 cfs for the months of November to June. r3.1.5 Functional Assessment A functional assessment of wetlands on Mitigation Banking Site 1 was prepared using the functional evaluation methodology described in Appendix B. The results of the assessment (Table 1) provide information on the functions that the existing wetlands provide, and identifies functions that are absent, degraded, or that could be provided with the proposed site plans for the mitigation banking sites. These results provide the basis for determining the value of the functions established by creating additional wetland habitat,and the baseline information that will be used to compare the success of the mitigation wetlands. Table 1. Summary of Functional Evaluation of Wetlands on Mitigation Banking Site 1 Rating Existing Conditions Proposed Conditions Characteristic/Function Low Medium High Low Medium High Wetland Condition X X Buffer Condition X X to X Biological Support X to X X to X Water Quality X X Flood and Storm Water Desynchronization X X to X Ground Water Exchange X X Support of Base Flow X X to X Cultural Value X X Shoreline Stabilization N/A N/A 3.1.5.1 Wetland Condition A low rating for wetland condition reflects that the wetland has been subject to human disturbance and the current ecological condition of the entire wetland is highly modified.. Mitigation Banking Site 1 has been cleared of native vegetation, filled, and colonized by several invasive vegetation communities. The condition of Mitigation Banking Site 1 could be improved by controlling exotic and invasive species, reestablishing wetland hydrologic conditions affected by fill, replanting with native wetland plant communities, and removing other human caused disturbances. 3.1.5.2 Buffer Condition The existing buffer condition of the site is low due to past and ongoing land-uses. To the north of the site, scrub-shrub and forested wetland communities provide higher quality buffer and habitat functions. Undeveloped land also provides a buffer to the south of the site. Increasing vegetation density along the southern and western perimeter of the site will increase the buffer capacity in these areas. While the BN railroad track west of the site and Oakesdale Avenue limit the ability of off-site areas to function as wetland buffers,plantings along the perimeter of the site would increase the ability of on-site vegetation to protect the site from adjacent land-uses. City of o Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-5 January 1001 IIKIRKLAND_II VOL]IDATAI"Aing11779155J-1779-071MIT BANK PLAN-revise part 111-01.doc I 3.1.5.3 Biological Support The biological support function is considered to be low to moderate. The wetland communities provide limited structural diversity (i.e. the types and diversity of plant communities and habitat types present) and this condition reduces the species diversity of the site. No unique or water-dependent species are present on the site. The forest and shrub communities provide cover and nesting or perching sites for small mammals and birds. The upland and seasonally wet meadow areas provide habitat for small mammals that are prey to larger mammals (e.g., coyote) and raptors (e.g., red-tailed hawks). The functional evaluation indicates that the value of the biological support function would be higher by increasing the habitat structure and interspersion of habitats and habitat types(creating greater edge effects)and adding special habitat features. 3.1.5.4 Water Quality Improvement The functional evaluation indicates a high potential for improving water quality in the existing wetlands. However, the three wetlands do not contribute to improving downstream water quality and filtering of contaminants from adjacent non-point and point source pollutants because there is no flow of urban runoff from off-site areas into the wetland. The wetlands'usefulness in providing significant water quality function would increase directing water contained in the drainage ditch near the southwest corner of the site to on-site wetlands. 3.1.5.5 Storm Water and Flood Water Desynchronization The wetlands are not in any floodplain and do not receive runoff from upslope areas, and are thus rated low for this function. This function could be increased to high by connecting the existing drainage ditch into the mitigation design. Thus, upstream storm runoff that enter the drainage ditch would be attenuated on the mitigation site. 3.1.5.6 Groundwater Exchange Although a potential aquifer occurs deep below the site,the three wetlands are underlain by slowly permeable consolidated fill which causes seasonally perched water. This condition limits the ability to provide 1 significant groundwater recharge functions. Created wetlands on the site are not expected to contribute significantly more than undeveloped uplands or other wetland to groundwater exchange. 3.1.5.7 Support of Base Flow ' All three wetlands have characteristics that indicate seasonal hydrology and ponding which may augmenting base flow to Wetland W-12a and Springbrook Creek. Establishing direct connectivity between the mitigation banking site and the City of Renton wetlands and Springbrook Creek could increase the value of this function. 3.1.5.8 Cultural Value The opportunity for Mitigation Banking Site 1 to provide recreational and visual opportunities, or aesthetic appreciation for the natural environment, is low because of the existing conditions of the site (i.e. lack of habitat diversity, and lack of access). Opportunities for cultural values associated with wetlands would increase by incorporating public access and a trail system into the City of Renton's open space and parks program. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-6 January 2001 IIKIRKLAND_1I VOL]DATA Iw rking11779U54-1779-07MITBANKPLAN-revise part 11 I.01.doc 3.1.5.9 Shoreline Stabilization This function is not applicable to Mitigation Banking Site 1. 3.1.6 Wetland Rating 3.1.6.1 City of Renton Under the City of Renton's wetland classification system, the wetlands qualify as Category 3 wetlands because they are disturbed from(1) clearing and filling, (2)hydrologic alterations, and(3)the presence of fill. 3.1.6.2 Washington Department of Ecology Wetland M on Mitigation Banking Site 1 is classified as a Category II wetland according to the Washington State Wetlands Rating System, Western Washington (Washington Department of Ecology 1993). Wetlands J and L are Category III wetlands. 3.2 MITIGATION BANK SITE 2 Mitigation Banking Site 2 is 13.93 acres,of which 6.69 acres are wetland and 7.24 acres are upland. The site 1 consists primarily of herbaceous perennial grasses and forbs, annual forbs, and early successional shrub and forested wetlands. Forested wetlands are dominated by black cottonwood (see Figure 3; David Evans and Associates 1991b). The entire site was filled within the past 20 years and the topography is relatively flat, with elevation ranging from 15 to about 18 ft. Grading work on the site has resulted in small depressions that contain compacted soil, some of which pond water. The site is not within the 100-year floodplain (City of Renton 1993). 3.2.1 Wetland Delineation Two wetlands totaling 6.69 acres were identified and delineated by David Evans and Associates (1991b). Willow, black cottonwood, and Himalayan blackberry dominate the northern wetlands. The wetlands are classified as palustrine scrub-shrub wetlands. These wetlands occur on fill and are not regulated by the Army Corps of Engineers(ACOE 1996). 3.2.2 Vegetation The shrub plant community consists of black cottonwood saplings and willow shrubs. Salmonbeny and 1 Himalayan blackberry shrubs are also present. Herbaceous plant cover within the shrub community is sparse, but grasses and forbs occur occasionally. The emergent wetlands consist of shallow depressions dominated by bentgrass; foxtail,Alopecurus geniculatus; soft rush; and reed canarygrass. Upland forbs and grasses include clover, Tripholim repens; Kentucky bluegrass, Poa pratensis; tall fescue, Festuca arundinacea; quackgrass,Agropyron repens;and hairgrass,Aira caryophyellea. I City of Renton 553-1779-009 Draft-Weiland Mitigation Banking Plan 3-7 January 2001 � IIKIRKLAND_11VOLIIDATAIwortdng117791554-1779-071M]TBANK PLAN-revise part 111-01.doc ' 3.2.3 Soils, Hazardous Material and Geotechnical Information 3.2.3.1 Soils The Soil Survey for King County (Snyder et al. 1973) mapped the soils on Site 2 as Woodinville silt loam However,the majority of the site consists of urban fill. The type of fill and its compaction have resulted in a low permeability material, which, coupled with ambient hydrology, have lead to hydric conditions developing within the fill. 3.2.3.2 Hazardous Materials A preliminary environmental site assessment made by Kennedy/Jenks/Chilton (1989) indicated that a small potential existed for contamination to enter the site via groundwater. A site reconnaissance did not identify significant potential for environmental contamination from current or past site use. An environmental site assessment(Hart Crowser 1991b)indicated that sediment samples collected from Springbrook Creek south of SW 27th Street (between Lind Avenue and Oakesdale Avenue SW) had contamination below the Model Toxic Control Act Method A cleanup levels and below the WAC Sediment Criteria. No remedial activities were recommended for this area. 3.2.3.3 Geotechnical Information Five soil test pits were examined on Mitigation Banking Site 2 (see Figure 3). The results of this analysis are ' summarized below. Soil test pit 1 was excavated in an upland area adjacent to Springbrook Creek at an elevation of about 19.5-ft. In general,the soils were uniform from the surface to an elevation of about 10.5-ft(see Figure 5). The soils consisted of sandy, silty fill. A blue-gray saturated clay layer was observed at an elevation of about 10.5 ft and extended down to an elevation of about 9 ft. Concrete debris was observed at 4 ft 5 inches. No standing water was observed. The depth of fill was estimated to be approximately 9 ft. Soil test pit 2 was also excavated in an upland area adjacent to an emergent wetland community at a surface elevation of approximately 16.5-ft (see Figure 5). From the surface to an elevation of 12 ft, the soil was sandy and lightly mottled with a thin, silty, clay layer observed at an elevation of about 14.5 ft. At an elevation of 11.5 ft, the silty clay sediment was saturated and mottled. Blue clay was observed at an elevation of 10 ft, followed by saturated silty clay to an elevation of 7 ft. A lens of organic material with woody debris and black wet sand was observed below elevation 6.5 ft. Water was evident at elevation 5.2 ft and seepage was evident at elevation 7 ft. Plant roots were evident as deep as an elevation of 5.5 ft. Soil test pit 3 was excavated in shrub wetland, at a surface elevation of 16 ft (see Figure 5). Mottled sandy silt was evident at an elevation of 15 ft. The soils had more sandy texture above elevation 15 ft,but below elevation 15-ft finer soil textures dominated. An oxidized iron zone was observed at elevation 14 ft. At elevation 11 ft, the soils consisted of damp clay with bright mottles. The depth of fill was estimated to be 4.5 to 5 ft. tSoil test pit 4 was excavated in an upland area with a surface elevation of 15.5-ft(see Figure 5). The soil consisted of sand and gravel fill with silt from the surface to an elevation of 11.5 ft. The historic A horizon, composed of silty clay with mottles, occurred within a 10 to 12-inch band below the fill. Below the historic A horizon was a 4-inch gleyed layer with strong mottles. Water seepage was observed at 7.5 ft. Clay was the dominant sediment to about elevation 4.5-ft. Below 4.5 ft the sediment was black, wet sand. The depth of the fill was estimated to be 4 to 4.5 ft. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-8 January 2001 I1KIRKLAND_11VOLIIDATA1wrhng117791554-1779-07W1T BANK PLAN-revise part 111-01.doc Soil test pit 5 was excavated in an upland area; it had a similar profile to test pit 4, and at a surface elevation of 16 ft. Fill occurred from the surface to an elevation of about 13 ft (see Figure 5). This soil horizon showed no wetland characteristics. The historic A horizon was observed to 12 inches below the fill. Clay was the dominant soil texture below the historic A horizon. Seepage was evident at 8 ft. Black sand was observed at an elevation of 5.5 ft. The depth of the fill was estimated to be 3 ft. ' No differences were observed in the soil texture or composition within the top 3 to 4 ft between wetland and upland areas. Wetlands have developed as a result of fine textured fill material which is able to perch and pond water . Dames & Moore (1995) conducted a geotechnical investigation of the site 2. This study examined five test pits and found fill was present in all test pits. The fill is underlain by alluvial soils, the upper 4 to 10 feet of which was found to be silt. The silt layer contains sand layers ranging from 2 to 2.5 feet in thickness and thin layers of peat. 3.2.4 Hydrology The source of hydrology for the existing wetlands on Mitigation Banking Site 2 is precipitation. Wetlands on this site do not appear to receive runoff from adjacent land and have no inlet or outlet. The elevation of the wetlands are several feet higher the typical water elevation of Springbrook Creek(about 7.8 feet). ' Northwest Hydraulic Consultants, Inc. (NHC) conducted a hydrologic analysis of flood frequencies of Springbrook creek and evaluated changes to stream hydrology based on the proposed mitigation. These analyses are presented in Appendix X). NHC used the hydrologic simulation program-Fortran model (HSPF) to determine flow under different watershed conditions for Springbrook creek as it passes the mitigation Site 2. The model predicted flood flows of Springbrook creek under current land-use to be 355 cubic feet per second (cfs) at bankfull conditions (approximately the 2.0 year storm). At the 10, 25, 50 and 100-year floods, flows of 570, 698, 803, and 917 cfs respectively, are predicted. 3.2.5 Functional Assessment ' The functions of the existing wetlands on Mitigation Banking Site 2 were assessed using the functional evaluation in Appendix B. The results of this assessment(Table 2)indicate that the wetlands are generally of low quality. Table 2. Summary of Wetland Functions Provided by Mitigation Banking Site 2 Rating Existing Conditions Proposed Conditions Characteristic/Function Low Medium High Low Medium High Wetland Condition X X Buffer Condition X X to X Biological Support X X to X ' Water Quality X X Flood and Storm Water Desynchronization X X Ground Water Exchange X X City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-9 January 2001 I IMLAND_IIVOL]OATAI"rhng117791554-1779-071MIT BANK PLAN-revise par!II 1-OLdoc Support of Base Flow X X Cultural Value X X Shoreline Stabilization N/A X to X ' 3.2.5.1 Wetland Condition ' The general condition of the wetland was rated as low, because the site has been impacted by a variety of human activities. Alterations including filling, vegetation clearing,diking of Springbrook Creek, have been occurred on the site for the past 20 years. The wetland would receive a higher rating under the proposed mitigation-banking plan because fill material would be removed, human impacts would not be allowed, and hydrologic conditions could be improved. 3.2.5.2 Buffer Condition The condition of the buffer is considered poor. Oakesdale Avenue constitutes the western buffer of the site. The presence of Springbrook Creek along the south and west sides of the site provides a connection to off site habitats. Undeveloped land (zoned industrial) currently provides a buffer to the north. The rating for the buffer condition would improve slightly over existing conditions by improving the buffer condition between Oakesdale Avenue and the new wetlands,as well as along Springbrook Creek. 3.2.5.3 Biological Support ' The ability of the existing wetlands to provide biological support is low, due to their small size, low plant species diversity, lack of habitat interspersion, early successional state, ongoing disturbances, and lack of hydrologic connectivity with Springbrook Creek. In addition, observations by David Evans and Associates (1991b) indicated that very few animals were using the site. The proposed banking plan for Mitigation Banking Site 2 would increase the number of habitat types,provide habitat interspersion, increase structural diversity,and provide a direct connection to Springbrook Creek. 3.2.5.4 Water Quality Since there appears to be little or no surface water flow onto the site, and the wetlands are not in any floodplain,they have little ability to improve water quality. The proposed plan would allow floodwater from Springbrook Creek to enter the site thereby allowing potential contaminants to be removed by the wetland. ' 3.2.5.5 Flood and Storm Water Desynchronization The on-site wetlands do not provide flood or storm water attenuation due to their small size, lack of hydrologic connections, and elevation above any floodplain. Based on the proposed banking plan, the site would receive a high rating for this function because the proposed connection to Springbrook Creek. 3.2.5.6 Ground Water Exchange 1 The wetlands are underlain by slowly permeable compacted fill. Although a potential aquifer is under the site, the presence of a confining layer of consolidated clay and fill over the aquifer significantly limits the groundwater exchange function. The mitigation-banking plan is not expected to alter the function of this site relative to groundwater exchange. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-10 January 2001 IIKIRKLAND_11 VOLIIDATAIworkingl17 791554-1 779-0 71MIT BANK PLAN-revise part 11 1-01.doc ' 3.2.5.7 Support of Base Flow The existing wetlands are isolated from a surface water system and do not support the base flow of Springbrook Creek. The proposed plan would allow flood and storm waters to be temporarily stored on the site,but relatively rapid release following flood events would not augment base flows of the creek. ' 3.2.5.8 Cultural Values A low rating for cultural value results from an absence of scenic diversity, open water, and public access 1 to the site. The proposed plan would provide for passive recreation, educational opportunities, and a trail link to the City of Renton's park system. 3.2.5.9 Shoreline Stabilization The wetlands do not provide shoreline stabilization functions because they are isolated from any shoreline I area. A direct connection would be established between Springbrook Creek and the site under the proposed plan. The site would attenuate energy from flood and storm water in the creek, and help in preventing downstream stream bank erosion. 3.2.6 Wetland Rating 3.2.6.1 City,of Renton The wetlands on Mitigation Banking Site 2 are classified as Category 3 wetlands (City of Renton 1990). 3.2.6.2 Washington Department of Ecology The wetlands are rated as Category 3 wetlands using the Washington State Wetlands Rating System, Western Washington(Department of Ecology 1993). 1 City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 3-11 January 2001 IIKIRKLAND_I I VOL]0.4 TA Iw rkingl1 7 791554-1 779-07IMIT BANK PLAN-revise part II 1-01.doc APPROACH4. MITIGATION ' 4.1 MITIGATION SEQUENCING Private and public projects that may impact wetlands under City of Renton jurisdiction are required to ' comply with mitigation sequencing as identified in the City of Renton's wetland ordinance (City of Renton, 1992). Section 4-32-5 (A)(1)(i) of the ordinance states that applicants "shall evaluate alternative methods of developing the property using the following criteria in this order: ' • Avoid any disturbances to the wetland or buffer; • Compensate for any wetland or buffer impacts; • Minimize any wetland or buffer impacts; • Restore any wetlands or buffer impacted or lost temporarily; and • Create new wetlands and buffers for those lost. In implementing its ordinance,the City recognizes that there is flexibility in interpreting these guidelines on a case-by-case basis for projects participating in a mitigation bank. In addition, projects using the mitigation bank that require approval by the Army Corps of Engineers under Section 404 of the Clean Water Act,must comply with sequencing requirements of the 404(b)(1) guidelines. Interpretation and standards for meeting guidelines for compliance with City ordinance may differ from those made to comply with Federal requirements. 4.2 MITIGATION PLAN GOALS, OBJECTIVES, AND PERFORMANCE STANDARDS The overall mitigation goal for the City of Renton Wetland Mitigation Banking plan is to: Establish about 20 acres of wetland mitigation and about 24 acres of enhanced wetland and buffer habitat. The wetlands will include 4 wetland classes and upland forested buffer that will provide food chain support and habitat connectivity to terrestrial and aquatic wildlife. The wetlands will provide hydrologic functions such as stormwater/flood flow retention; and quality improvement. (Incorporation of the sites into park and recreation plans will result in public access and the function of the sites as education/cultural values. To achieve this,the following specific objectives have been developed: ' 4.2.1 Mitigation Banking Site 1 Water Rellime • The wetland will provide approximately 10 acre-ft of stormwater storage. • The wetland will contain a hydrologic connection to Wetland W-12a and Springbrook Creek. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 4-1 January 2001 ' IIKIIUQAND_PVOL IIDATA Iworkingl 1779'S54-1779-0WIT BANK PLAN-revise part II I-OLdoc 1 ' Vegetation Structure ' • The wetland will consist of about 2.9 acres of seasonally flooded emergent, 5.7 acres of shrub, and 1.4 acres of forested wetland plant communities. ' • The new wetland will be integrated with vegetation enhancement of about 20 acres of existing upland and wetland areas. Habitat Attributes • Forested components of the mitigation site will provide the structural elements for resident wildlife (birds and small mammals) and migratory birds, including a mixed deciduous and coniferous canopy, understory shrub canopy, and herbaceous ground cover. • Heterogeneity between upland and wetland communities will provide resting, feeding, breeding habitat for aquatic fauna, terrestrial fauna, water foal, and amphibians. • Woody debris(downed logs, snags, and stumps)will provide habitat diversity. 1 • The upland buffers will screen the mitigation wetland from adjacent uplands and roads. 4.2.2 Mitigation Banking Site 2 Water Regime ' • The wetland will provide up to 50 acre-ft of flood storage. • The wetland have a surface hydrologic connection to Springbrook Creek. Vegetation Structure ' • The wetland will consist of 2.0 acres of emergent, 1.4 acres of shrub, and 6.4 acres of forested vegetation classes. ' • Wetland plant communities will be protected and enhanced by about 4 acres of forested upland buffer. Habitat Attributes • Forested components of the mitigation site will provide the structural elements for resident wildlife (birds and small mammals) and migratory birds, including a mixed deciduous and coniferous canopy, understory shrub canopy, and herbaceous ground cover. • Heterogeneity between upland and wetland communities will provide resting, feeding, breeding habitat for aquatic fauna,terrestrial fauna,water foal, and amphibians. • Woody debris(downed logs, snags, and stumps)will provide habitat diversity. • The upland buffers will screen the mitigation wetland from adjacent uplands and roads. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 4-2 January 2001 IIKIRKLAND_II VOL]IDATAIworldngV 779)554-1779-071M1T BANK PLAN-revise part 111-01.doc • Hydrologic connectivity between Site 2 and Springbrook Creek will allow for the downstream transport of organic carbon,thereby assisting in the support of instream food webs. ' 4.3 PERFORMANCE STANDARDS ' Performance standards for wetlands constructed at the mitigation bank sites will be used to determine if the sites have been adequately constructed and if their ecological functions have been achieved. Performance standards will be evaluated by measuring variables and determining if standards and objectives have been ' met. 4.3.1 Mitigation Banking Site 1 Water Regime ' Objective: The wetland will provide approximately 10 acre-ft of stormwater storage. Performance Standard: Grading plans, hydrologic analysis, and monitoring data will demonstrate that the wetland collects runoff from the adjacent ditch and provides a minimum of 10 acre feet of stormwater storage. Objective: The wetland will contain a hydrologic connection to Wetland W-12a and Springbrook Creek. Performance Standard: The wetland will discharge through a surface water connection to Wetland IW-12a. Vegetation Structure ' Objective: The wetland will consist of about 2.9 acres of seasonally flooded emergent, 5.7 acres of shrub, and 1.4 acres of forested wetland plant communities. ' Performance Standard: Analysis of site topography, planting records, and hydrologic monitoring will demonstrated that suitable hydrologic conditions exist for the maintenance of the desired wetland plant communities. ' Objective: The new wetland will be integrated with vegetation enhancement of about 20 acres of existing upland and wetland areas. ' Performance Standard: Trees and shrubs planted to enhance wetland and upland areas bordering the constructed wetland will adapted to observed soil moisture regimes. Habitat Attributes Objective: Forested communities will provide the structural elements for resident wildlife (birds and ' small mammals) and migratory birds, including a mixed deciduous and coniferous canopy,understory shrub canopy, and herbaceous ground cover. ' Performance Standard: Forested plant communities will be multi-structural. While deciduous species are predominant, a minimum of 25 percent of the canopy individuals will consist of coniferous species. Understory shrub species will occur a minimum of 50 percent of the forest zones. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 4-3 January 2001 IIKIRKLAND_I I VOLPDATAI working11779{554-1779-071MIT BANK PLAN-revise pan/I 1-01.doc Herbaceous groundcover shall consist of non-invasive plant species,but may include non-native grass or forb species used in hydroseed mixes to reduce colonization by blackberry or reed canary grass. ' Objective: Heterogeneity between upland and wetland communities will provide resting, feeding, breeding habitat for aquatic fauna, terrestrial fauna,waterfowl, and amphibians. ' Performance Standard: Topographic variation, including microtopographic features, non-linear edges between planting zones, and spatial variation in planting will be present, as verified by analysis of as-built mitigation plans. ' Objective: Woody debris (downed logs, snags, and stumps)will provide habitat diversity. ' Performance Standard: A minimum of 10 habitat structures per acre will be placed in the new wetlands constructed on the mitigation site. These structures will include downed logs (33 percent), standing snags (33 percent) and stumps (33 percent). Objective: The upland buffers will screen the mitigation wetland from adjacent uplands and roads. ' Performance Standard: Upland buffers will be planted with tree and shrub species at densities exceeding 250 trees per acre and 400 shrubs per acre. 4.3.2 Mitigation Banking Site 2 Water Regime ' Objective: The wetland will provide up to about 50 acre-ft of flood storage. Performance Standard: Grading plans, hydrologic analysis, and monitoring data will demonstrate that the wetland collects runoff from the adjacent ditch and provides a minimum of 50 acre feet of flood storage are present. Objective: The wetland will contain a hydrologic connection to Springbrook Creek. Performance Standard. The wetland will discharge through a surface water connection to the adjacent creek. The connection channel will be stabilized with rock as necessary to assure its long term function. Vegetation Structure ' Objective: The wetland will consist of about 2.0 acres of seasonally flooded emergent, 1.4 acres of shrub, and 6.4 acres of forested wetland plant communities. rPerformance Standard: Analysis of site topography,planting records, and hydrologic monitoring will demonstrated that suitable hydrologic conditions exist for the maintenance of the desired wetland plant communities. Objective: The new wetland will be integrated with vegetation enhancement of about 4.0 acres of existing upland and wetland areas. Performance Standard: Trees and shrubs planted to enhance wetland and upland areas bordering the constructed wetland will adapted to observed soil moisture regimes. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 4-4 January 2001 IIKIRKLAND_11 VOLIIDATA Iw rkingV 7791554-1779-07WIT BANK PLAN-revise part I11-Ohloc Habitat Attributes Objective: Forested communities will provide the structural elements for resident wildlife (birds and small mammals) and migratory birds,including a mixed deciduous and coniferous canopy,understory shrub canopy, and herbaceous ground cover. Performance Standard: Forested plant communities will be multi-structural. While deciduous species are predominant, a minimum of 25 percent of the canopy individuals will consist of coniferous species. Understory shrub species will occur a minimum of 50 percent of the forest zones. Herbaceous groundcover shall consist of non-invasive plant species,but may include non-native grass or forb species used in hydroseed mixes to reduce colonization by blackberry or reed canary grass. Objective: Heterogeneity between upland and wetland communities will provide resting, feeding, breeding habitat for aquatic fauna,terrestrial fauna,waterfowl, and amphibians. ' Performance Standard: Topographic variation, including microtopographic features, non-linear edges between planting zones, and spatial variation in planting will be present, as verified by analysis of as-built mitigation plans. ' Objective: Woody debris(downed logs, snags,and stumps)will provide habitat diversity. Performance Standard: A minimum of 10 habitat structures per acre will be placed in the new ' wetlands constructed on the mitigation site. These structures will include downed logs (33 percent), standing snags (33 percent)and stumps(33 percent). Objective: The upland buffers will screen the mitigation wetland from adjacent uplands and roads. Performance Standard: Upland buffers will be planted with tree and shrub species at densities exceeding 250 trees per acre and 400 shrubs per acre. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 4-5 January 2001 IIKIRKLAND_II VOL]DATA Iw rkingi17791554-1779-071MITBANKPLAN-revisepartII1-01.dac PRELIMINARY5. The preliminary site plans for Mitigation Banking Sites 1 and 2 are shown in Figure 6 and Figure 7, respectively. The preliminary site plans illustrate the proposed changes in topography, and hydrology, proposed vegetation distribution and structure, location of habitat types, and the proposed buffer, and section drawing that shows the relationship of topography,hydrology, and vegetation. 5.1 TOPOGRAPHY Excavation on about 10 acres of Mitigation Banking Site 1 is proposed to occur to create new wetland areas up to 6 feet below existing grades. The planned excavation establishes a broad wetland drainageway connecting the existing ditch on the west side of the site to wetland W-12a. Excavation of about 9.8 acres of Mitigation Banking Site 2 will occur to depths up to 15 feet below existing grades. This grading will connect the new wetland to the Springbrook Creek channel, and floodplain. On both sites, the grading will allow for a variety of wetland communities to be established within each ' site; the changes will also result in the removal of significant amounts of material from each site An estimated 172,000 cubic yards of material could be removed from Mitigation Banking Site 1 and 'A to 150,000 cubic yards from Mitigation Banking Site 2. 5.2 SOURCE OF WATER The proposed source of water for Mitigation Banking Site 1 is from the drainage ditch at the southwest corner of the site (see Figure 6) and on-site precipitation. An inlet at an elevation of about 17 feet would be constructed and a notched weir outlet at an elevation of about 12 feet is proposed at the northeast corner of the site. Figure 11 shows the location of a flow splitter at the inlet to Mitigation Banking Site 1. The amount ' of water in the drainage ditch is expected to exceed the amount of water needed to support the proposed wetland communities. ' A potential alternative or complementary source of hydrology is groundwater. Results of 1995 soil investigations, groundwater monitoring data, and measurements of water flow in the drainage ditch will provide additional information to define the source of water for created wetlands on Mitigation Banking Site 1. The proposed water source for Mitigation Banking Site 2 is Springbrook Creek and precipitation(see Figure 7). The site will be graded to establish a hydrologic connection between the wetland and Springbrook Creek. ' Finally, for both mitigation sites, since most forested wetland plant communities of the Puget Sound are typically non-saturated during the late spring to early fall timeframe, wetland hydrology to these systems can be provided by wet season precipitation. Precipitation will be an adequate source of water to the wetland if the site is constructed with low permeability soils such as silty clay loam. 5.3 SOILS Generally soils on site are expected to provide suitable planting media for the planned wetland communities. Development of wetland vegetation could probably be enhanced if the upper 12 inches of on-site soils were ' amended with organic matter. In addition, soils in areas designated as forested wetland are likely to receive much of their wetland hydrology from precipitation. These areas must have a relatively low permeability subsoil that remains saturated during winter and early spring months. In some locations,the existing subsoil may need to be amended with clay soils,or compacted to reduce permeability. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 5-1 January 2001 IIKIRXUAFD_II VOL]DATA4orkingU779US4-1779-07MITBANKPLAN-revisep lIII-01.doc Figure 6 Proposed Site Plan for Mitigation Banking Site 1 1 1 1 1 1 i i 1 1 1 City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan 5-2 January 2001 IIKIRKLAND—II VOLT I DATAI working117791554-1779-071MIT BANK PLAN-revise part 11 1-01.doc i Figure i7 Proposed Site Plan for Mitigation Banking Site 2 City of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan 5-3 January 2001 I WIRKLAND_I I VOL]IDATAI workingV 7791554-1779-07MIT BANK PLAN-revue part 11 1-07.doc 5.4 PROPOSED PLANT DISTRIBUTION The plant species that are proposed for the two mitigation banking sites are the same (Table 3). Some of the proposed species tolerate wide fluctuations in duration of inundation (e.g. salmonberry, red-osier dogwood). In general, trees with a wetland indicator of FAC or FACW will be planted in the areas within elevation zones denoted as created forested wetlands and shrubs will be placed in areas within elevations zones denoted as created scrub-shrub wetlands. Herbs, forbs and grasses will be planted in elevations ' designated for emergent wetland creation and open water habitat (see Figures 6 and 7). The distribution of individual species will be determined based on the final grading plan. Following final site plan design a final planting plan will be prepared that includes planting locations, the quantity of each plant species,plant spacing, plant type (e.g.,root stock,plugs), plant height, and planting specifications. Plant survival on wetland mitigation sites can be improved using temporary irrigation systems, which add flexibility to the season of year planting occurs in and reduce mortality that may occur during dry periods. The final plan will also specify areas where invasive weeds will be removed or other wise managed as part of the planting plan. This management could include herbicide treatment, clearing and grubbing, planting of vegetation to out compete undesirable species, or other methods. ' Table 3. Candidate Plant Species Proposed Wetlands and Buffers Scientific Name Common Name Wetland Status* ' Trees Alnus rubra(1) red alder FAC Crataegus douglasii(2) black hawthorn FAC Fraxinus latifolia(3) Oregon ash FACW Populus trichocarpa(1) black cottonwood FAC Pyrus fusca(3) western crabapple NIL Rhamnus purshiana(3) cascara Facu Salix sitchensis(2) Sitka willow FACW Salix lasiandra(1) Pacific willow FACW+ ' Salix scoulerana(1) Scouler willow FAC Thuja plicata(2) western redceder FAC Shrubs Corpus stolonifera(1) red-osier dogwood FACW Lonicera involucrata(2) black twinberry FAC Ribes bracteosum(3) stink currant FAC Rosa nutkana(3) Nootka rose NI Rosa pisocarpa(2) clustered rose FACU Rubus spectabilis(1) salmonberry FAC Sambucus racemosa(2) red elderberry FACU Spiraea douglasii Douglas spirea FACW Herbs ' Angelica gennuflexa(3) keneeling angelica FACW Aster occidentalis(2) western mountain aster FAC Bidens cernua(2) nodding beggar-tick FACW+ ' Cite of Renton 553-1779-009 Draft- Wetland Mitigation Banking Plan 5-4 January 2001 IIKIRKLAND_11 VOLIIDATAIworking11 7 79155 4-1 7 7 9-0 71MIT BANK PLAN-revise part 11 I-OLdoc Table 3.Candidate Plant Species Proposed Wetlands and Buffers (Continued) Scientific Name Common Name Wetland Status* Herbs(con't) Geum macrophyllum(3) large-leaved avens FACW Lotus pinnatus(3) meadow deer vetch FACW Ludwigia palustris(3) water-purslane OBL Lupinus polyphyllus(3) large-leaved lupine FAC+ Oenanthe sarmentosa(2) water-parsley OBL Polygonum persicaria(2) smartweed Rorippa nasturtium-aquaticum(2) true water-cress OBL Rumex acetasella(3) garden sorrel NI Rumex crlspus(3) curly doc FACW Tolmiea menziesii(2) piggy-back plant FACW Pypha latifolia(1) common cattail OBL Veronica americana(2) American brooklime OBL Graminoids ' Agrostis tenuis(1) colonial bentgrass NL Alopecurus geniculatus(1) water(oxtail FACW+ Carex obnupta(1) slough sedge OBL Carex stipata(1) sawbeak sedge FACW Eleocharis palustris(2) common spike-rush OBL Elymus cinerrus(3) giant wild rye NI Glyceria elata(3) tall manna grass FACW+ Glyceria occidentalis(3) western mannagrass OBL Juncus bufonius(1) toad rush FACW+ Juncus ensifolius(1) dagger-leaf rush FACW Juncus tenuis(1) slender rush FAC Scirpus acutus(1) hard-stem bulrush OBL ' Scirpus microcarpus(1) small-fruited bulrush OBL Sparganium emersum(3) narrow-leaf burreed OBL (1) Dominant Species ' (2) Sub-dominant Species (3) Associated Species 5.5 SECTION DRAWINGS Cross sections and grading plans (see Figures 6 and 7) illustrate the vegetation communities, habitat types, and general hydrologic conditions to be established on the mitigation sites. The cross section also illustrates the proposed interspersion of habitat types and structural diversity that could be developed on this site. The section drawing for Site 2 (Figure 12) also shows the estimated water levels in the wetland during summer base flow conditions and during the 2- and 10-year storm event. 5.6 PUBLIC ACCESS Locations of potential interpretive trails, trail entry;signage, and an interpretive shelter on Mitigation Banking Site l and Mitigation Banking Site 2 must be developed. are shown in;Figures 6 ,and 7, respectively. The interpretive trail for Mitigation Banking Site 1, which would be limited to the western portion of the site, would pass through wetlands. A bridge structure would need to be constructed for portions of the trail within wetland areas. ' City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 5-5 January 2001 IIKIRKLAND_I I VOLIIDA TA Iworldngi 17791554-1779-07MIT BANK PLAN-revise part 11 I-01.doc An interpretive trail for Mitigation Banking Site 2 would be located along the berm of Springbrook Creek; therefore it would not encroach on any wetlands. A bridge would need to be constructed across the breach in the berm to provide public access from SW 34th Street to Oakesdale Avenue. Interpretive signage would be unobtrusive. Signage could illustrate the construction of the mitigation banking sites from existing to post-construction conditions; the wetland communities; habitat types; wildlife that use the wetlands; or document the functions that wetlands provide. The_interpretive shelters, which would also have signage, would be aplace where people can stop to rest and observe the wetlands. The trail systems would be integrated into existing and proposed trail systems within the City of Renton Parks Departinent jurisdiction. Requirements under the American Disability Act for site access will need to 1 be evaluated during final site design. i 1 1 1 1 i 1 1 1 1 City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 5-6 January 2001 I WIRKLAND_11 VOL](DATA 4orking11 7 791554-7 7 79-0 7LLIIT BANK PLAN-revise part 11 I-OLdoc 6. MONITORING • • The following chapter describes a preliminary monitoring plan for evaluating the mitigation banking sites. The anticipated parameters to be evaluated, methods of evaluation, and frequency of evaluation are provided. 6.1 VEGETATION Planted and naturally colonized vegetation will be evaluated to document plant establishment on the site and to determine if the desired wetland plant communities are present. Monitoring will include all wetland areas as well as designated buffer areas. Monitoring will occur systematically along monitoring transects. The transects will be permanently marked and identified on survey maps showing the as-built conditions. Data collection points will be established along transects within the wetland. At each data collection point, a 0.25-m2 quadrat will be used to measure the following: • Percent cover of each species and plant stratum, • The species composition(i.e. percent of each species, exotic or native, planted or colonized), • Average height and general health of each planted species, 1 • Vegetation structure, and • Density and size of snags and downed woody debris. Wetland vegetation will be monitored in early summer(between late June and July), during years 0-5, 7, and 10. 6.2 WATER REGIME The hydrologic conditions of each mitigation site will be evaluated to determine if adequate hydrology is present to support the desired wetland conditions and functions. Hydrologic measurements will include measuring the depth of surface inundation, the presence of soil saturation in the rooting zone, and estimating hydrologic flows into wetland areas from surface water sources (i.e. the ditch on Site 1, or Springbrook Creek on Site 2). Hydrology in each wetland community type will be measured a fixed locations monthly during the first three years following construction. Following this period, the monitoring frequency will be evaluated to determine if additional measurements are necessary to document that the wetlands are experiencing an adequate hydrologic regime. 6.3 SOILS ' The type of soil(s)to be used for construction of the mitigation site has not been determined. It may be possible to use some of the existing soils (i.e. clay) in the construction of open-water areas, and some of the subsurface and/or top soils for a planting medium. However, soil amendments may be necessary. General soil parameters to be monitored at fixed points along the permanent transects include soil color, percent of organic content, and the time and duration of saturation and/or ponding. Soil characteristics will be monitored once during the early portion of the growing season (April/May) in years 0-5, 7, and 10. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 6-7 January 2001 IIKIRKLAND_/IVOLIIDATAIworkingl/779U54-1779-07WrBANKPLO-revise part 11!-01.doc 6.4 FAUNA Wildlife using the mitigation site (including the buffer) will be made during the monitoring period. Wildlife monitoring will include observations of birds and mammals on the site 4 times each year(spring, summer, fall, and winter). Observations of amphibians that may use the sites will be documented through the presence of egg masses during late winter or early spring. Observations will be made from a fixed observation points as well as walk-through surveys during years 0-5, 7, and 10. The observations will be made at the same time (e.g., from 6:00 am to 12:00 pm), and during each sampling event. Between sampling years, observations will be made within 4 calendar days of each other.. 6.5 DEVELOPMENT OF HABITAT STRUCTURE 1 Monitoring the establishment of habitat structure will help determine whether suitable habitat is being established. Measurements of habitat structure will include the number of structural levels and distribution of habitats within the mitigation area. Monitoring parameters that provide information on the development of habitat structure include tree structure, the density and size of habitat features (i.e. snags, downed trees), canopy cover,number of structural levels, descriptions of adjacent land uses, and presence of priority habitats and species (Washington Department of Wildlife 1991). These parameters are discussed under monitoring for vegetation and water regime,above. 6.6 BUFFERS 1 Permanent transects will be established within the buffer area, and data collection points will be established along these transects. At each data collection point,a 0.25-n>?quadrat will be used to measure the following: • Percent cover of each species and plant stratum • The species composition(i.e.percent of each species, exotic or native,planted or colonized) • Average height and general health of each planted species • Vegetation structure Upland buffer vegetation will be monitored once between late June and July in years 0-5, 7, and 10 ' 6.7 SCHEDULE OF REPORTING MONITORING RESULTS For each monitoring year, following implementation of the proposed monitoring schedule (Table 4), data ' will be evaluated and results will be summarized in written monitoring reports. Following construction and planting, an as-built report will be prepared to document the project condition and any changes from the final site plan that may have occurred during construction or planting. The as-built report will serve as the baseline to compare results from subsequent monitoring efforts. Annual reports will be prepared and submitted to the City by December 15 of each monitoring year. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 6-8 January 2001 1 IIKIRKLAND IIVOLIIDATAIworkingll7791554-1779-07WITBANKPLIN-revisepaH1II-01.doc Table 4. Proposed Schedule for Monitoring City of Renton Mitigation Banking Sites Year 0 Monitoring Parameters (as built) 1 2 3 4 5 6 7 8 9 10 Topography X X X X X X X X Vegetation X X X X X X X X Water regime X X X X X X X X ' Soils X X X X X X X X Fauna X X X X X X X X Development of habitat X X X X X X X X structure Buffers X X X X X X X X City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 6-9 January 2001 IIKIRKLAND_1 WOL11DA TA Iworkiag!l7791554-1779-07MIT BANK PLAN-revise part 111-01.doc 7. SITE "PROTECTION 7.1 LEGAL PROTECTION As discussed in Section 2.3, both mitigation banking sites are owned by the City of Renton for the ' express purpose of habitat conservation and mitigation. The City of Renton will identify the mitigation banking sites as wetland management areas, and prepare legal documentation indicating that the sites will be adequately protected. ' 7.2 MAINTENANCE AND CONTINGENCY PLAN If, during the monitoring program, maintenance needs are identified that are required to ensure the 1 success of the mitigation project,they will be implemented. In addition, if performance standards for any element of the mitigation plan are not met, contingency actions will be implemented. For example, if the hydrology or hydroperiod of the wetlands do not correspond to that of the performance standard, actions (e.g. change the engineering design of the breach) will be taken to correct the deficiency. If planted vegetation shows signs of stress, an evaluation can be conducted to determine ' the cause. Replanting with other vegetation could occur after appropriate corrective action (such as soil amendments or regrading) has occurred. Alternatively, different plant species that are better adapted to *the environmental conditions of the site(e.g., elevations)could be planted. ' The probability of success for the proposed wetland communities is high considering that wetland communities, established on fill, currently exist on the site. Hydrologic conditions in the drainage ditch on the western perimeter of Mitigation Banking Site 1 and Springbrook Creek, adjacent to Mitigation Banking Site 2, are considered important elements to effective wetland creation on the mitigation banking sites. Additionally, it should be noted that the City does not have to post a performance bond, but should include funding within its annual budget monitoring and contingency actions. City of Renton 553-1779-009 Draft-We Mitigation Banking Plan 7-1 January 2001 1 IWRKLAND_IIVOLIIDATAIworkingl17791554-1779-071MITBANKPLO-revise pan III-01.doc 8. • • A draft implementation schedule of mitigation activities (through the as-built survey) for Mitigation Banking Site 2 is identified in Figure _. The SEPA review for site 2 was completed as part of the East Side Green River Watershed Project Plan and EIS (draft, Dec. 1996:final Sept. 1997). Design and permitting of Site 2 is schedule to begin An implementation schedule for Mitigation Banking Site ' 1 will be prepared as more information becomes available. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 8-1 January 2001 ' IWRYL4ND_IIYOLIIDATAIworkingll779U54-1779-071MIT BANK PLAN-revim par!11 I-01.dx 9. PERFORMANCE The City will appropriate money for the annual monitoring and maintenance of the mitigation site, and these monies will also include reserve amounts to implement contingency actions if needed. This action will provide the equivalent benefit of a performance bond, and assure that required construction, monitoring, maintenance,and adaptive management actions occur. r City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 9-1 January 2001 IIKIRKLAND_IIVOLIIDATAIworkingll7791554-1779A71MIT BANK PLAN-revise part II I-01.doc 1 . REFERENCES City of Renton. 1993a. Interim land use element of the comprehensive plan. Planning, Building, and ' Public Works Departments. Renton,Washington. City of Renton. 1993b. 1993 AWC Municipal Achievement Awards, City of Renton valley wetland ' mitigation bank program nomination. Renton, Washington. City of Renton. 1992. Wetland Management Ordinance, Ordinance number 4346, Section 4, Chapter 32 of Renton City Codes. Renton,Washington. ' and Associates. 1991a. Wetland determination on the Renton #14 parcel. Prepared for David Evans a P P Glacier Park Company. Seattle, Washington. 20 pp. plus appendices. David Evans and Associates. 1991b. Wetland determination on the Orillia block 8, lot 4 site (Renton #8E parcel). Prepared for Glacier Park Company. Seattle, Washington. 14 pp.plus appendices. ' Environmental Law Institute. 1993. Wetland Mitigation Banking, Environmental Law Institute, Washington,D.C. 159 pp. plus appendices. Golder Associates, Inc. 1992. Level II environmental assessment, south part of parcel 13, glacier park company. Prepared for the City of Renton. Redmond,Washington. Hart Crowser, Inc. 1991 a. Preliminary environmental assessment gpc property sequence no. 968, parcels 13 and 14,Renton, Washington. Prepared for Mark Miller Consultants, Inc. Seattle,Washington. Hart Crowser, Inc. 1991b. Preliminary surface water and sediment quality assessment; Springbrook Creek- Orillia Industrial Park, Renton, Washington. Prepared for Mark Miller Consultants, Inc. Seattle, Washington. Jones and Stokes. 1993. Appendix F—Wetland Inventory 1992. In R.W. Beck and Associates, 1993. Black River Basin. Draft Water Quality Management Plan, prepared for City of Renton, Renton, Washington. Jones and Stokes. 1991. Critical Areas Inventory, City of Renton Wetlands and Stream Corridors, prepared for City of Renton Planning/Building/Public Works, Renton, Washington. 32 pp. plus appendices and map. Kennedy/Jenks/Chilton Consulting Engineers. 1989. Preliminary environmental assessment Orillia ' Corporate Park property (Sequence 850), Renton, Washington. Prepared for Glacier Park Company. Federal Way, Washington. ' R.W. Beck and Associates. 1993. Black River Basin draft water quality management plan. Prepared for the City of Renton Department of Public Works. Renton,Washington. ' Reppert, R.T., Sigleo, W., Stakhiv, E., Messman, L., and Meyers, C. 1979. Wetland Values, Concepts and Methods for Wetlands Evaluation, U.S. Army Corps of Engineers, Institute for Water Resources, Fort Belvoir,Virginia. 109 pp. ' Snyder, D.E., Gale, P.S., and Pringle, R.F. 1973. Soil survey of King County area, Washington. Prepared by the U.S. Department of Agriculture Soil Conservation Service in cooperation with Washington Agricultural Experiment Station. Washington,D.C. 100 pp. plus maps. CityRenton 553-1779-009 of Renton -Wetland Mitigation Banking Plan 10-1 January 2001 ' IWRKLAND_IIVOLIIDATAIworking11 7 791554-1 7 79-0 71MITBANKPLWN evise part 111-01.doc r r Washington State Department of Ecology (Ecology). 1993. Restoring wetlands in Washington. A guidebook for wetland restoration, planning and implementation. Publication 93-17. 110 pp. plus appendices. rWashington Department of Wildlife. 1991. Management Recommendations for Washington's Priority Habitats and Species, Olympia,Washington. r r r r r r r r r r r r r r r City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan 10-2 January 1001 ' IWRKLAND_11 VOL]IDATAIworking17 7791554-1 7 79-0 71MIT BANK PLAN-revise part 111-01.doc ' GLOSSARY Category 1 Wetland - Category 1 wetlands are very high quality wetlands, greater than 2,200 sq.ft. which meet one or more of the following criteria: a. The presence of species listed by federal or state government as endangered or threatened, or the presence of essential habitat for those species; b. Wetlands having 40 to 60 percent permanent open water(in dispersed patches or otherwise)with two or more vegetation classes; c. Wetlands equal to or greater than ten acres in size and having three or more vegetation classes, one iof which is open water; d. The presence of plant associations of infrequent occurrence, or at the geographic limits of their ' occurrence;or e. Wetlands assigned the Unique/Outstanding#1 rating in the current King County Wetlands Inventory 1991 or as thereafter amended(City of Renton 1992). Category 2 Wetland - High quality wetlands greater than 2,200 sq.ft. which meet one or more of the following criteria: fa. Wetlands greater than 2,200 sq.ft.that are not Category 1 or 3 wetlands; b. Wetlands that have heron rookeries or raptor nesting trees,but are not Category 1 wetlands; ' c. Wetlands of any size located at the headwaters of a watercourse,but are not Category 1 wetlands; ' d. Wetlands assigned the Significant#2 rating in the current King County Wetlands Inventory 1991 or as thereafter amended; e. Wetlands having minimum existing evidence of human related physical alteration such as diking, ditching,and channelization(City of Renton 1992); Category 3 Wetland - Lower quality wetlands greater than 5,000 sq.ft. which meet one or more of the following criteria: a. Wetlands that are severely disturbed. Severely disturbed wetlands are wetlands which meet the ' following criteria: (1) Are characterized by hydrologic isolation, human-related hydrologic alterations such as diking, ' ditching,channelization,an/or outlet modification;and (2) Have soil alterations such as the presence of fill,soil removal,and/or compaction of soils; and ' (3) May have altered vegetation. ib. Wetlands that are newly emerging. Newly emerging wetlands are: (1) Wetlands occurring on top of fill materials;and City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan Glossary-I January 2001 ' IIKIRKLAND_IIVOLIIDATAIworking11 7 791554-1 779-0 71MITBANKPLAN-revisepa IIII-01.doc ' (2) Characterized by emergent vegetation, low plant species richness and used minimally by wildlife. These wetlands are generally found in the areas such as the Green River Valley and Black River Drainage Basin(City of Renton 1992). ' Category H Wetlands-These wetlands: (1)provide habitat for very sensitive or important wildlife or plant; (2) are either difficult to replace; or (3) provide very high functions, particularly for wildlife habitat (Washington Department of Ecology 1993). ' Category III Wetlands - These wetlands are important for a variety of wildlife species and occur more g rY p commonly than either Category 1 or 2 wetlands. Generally, these wetlands are smaller, less diverse, and/or ' more isolated in the landscape than Category II wetlands(Washington Department of Ecology 1993). Compensatory Wetland Mitigation - The process of creating, restoring, or enhancing wetlands to offset ' losses to wetland impacts associated with development activities. Ecosystem - A community of living organisms interacting with one another and with their physical ' environment, such as a rain forest,pond, or estuary. An ecosystem is a single complex system and/or as the sum of many interconnected ecosystems such as rivers,wetlands,and bays. ' Emergent Wetland-An emergent wetland is an area of the wetland where non-woody vegetation cover at least 30 percent of the ground. Environmental Site Assessment-An environmental site assessment is an investigation of the presence or likely presence of hazardous substances, including petroleum products, that may exist on a site due to past- on-site or off-site activities. ' Exotic and Invasive Vegetation-Native and non-native species of plants which can form monocultures in wetlands. ' Floodplain -An area adjacent to a lake, stream, ocean, or other body of water lying outside of the ordinary banks of the water body and periodically inundated by flood flows. ' Forested Wetlands-Woody vegetation that provides a canopy over the wetland that is at least 20 feet tall and 50 years old for deciduous trees and 80 years old for evergreens. Ground Water Recharge-The movement of surface water through an unsaturated zone of soil or rock into ' a ground water body. Habitat Structure-The physical complexity within each wetland class. Hydric Soil - A soil that is saturated, flooded, or ponded long enough during the growing season to periodically develop anaerobic conditions. ' Horizon-A distinct layer of soil,more or less parallel with the soil surface,having similar properties such as color, texture, and permeability. The soil profile is subdivided into the following major horizons: (1) A- horizon - characterized by an accumulation of organic material, (2) B-horizon - characterized by relative accumulation of clay, iron, organic matter, or aluminum; and (3) the C-horizon - the undisturbed and unaltered parent material. ' Mitigation Banking — Sites which may be used for restoration, creation and/or mitigation of wetland alternatives from a different piece of property than the property to be altered within the same drainage basin. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan Glossary-2 January 2001 ' IIKIRKLIND_II VOL]IDATAIworking11 7 791554-1 779-0 71MIT BANK PLAN-revise part 11 1-01.doc ' Performance Bond - Usually a financial payment made by project proponent to a local, state, or federal agency. Bonding holds a permitter accountable for implementing the mitigation, monitoring, and contingency plans. Performance Standards-Measurable values of specific variables that establish when mitigation objectives have been met. Performance standards may include values for variables such as dissolved oxygen, nutrient ' levels in water, survival rate of planted vegetation, species diversity, water flows, water depths, and wetland size. Scrub-Shrub Wetland - A scrub-shrub wetland is any area of vegetated wetland where woody vegetation less than 20 ft.tall comprises at least 30 percent of the areal cover. Species Diversity -The number of different plant species within each vegetated wetland class that cover at least 5 percent of the ground within the area covered by that class. Wetland-Wetlands are those lands transitional between terrestrial and aquatic systems that are inundated or ' saturated by ground or surface water at a frequency and duration sufficient to support and, under normal circumstances, do support prevalence of vegetation typically adapted for life in saturated soil conditions(City of Renton 1992). Wetland Buffer - Wetland buffers are designated areas adjacent to a regulated wetland which protect the wetland from surrounding activities and protect adjacent properties from changes .in the location of the ' wetland edge(City of Renton 1992). Wetland Classes - The types of vegetation in wetlands. Emergent, scrub-shrub, and forested wetlands are examples of wetland classes. ' Wetland Classification-The process of identifying and classifying wetlands. Wetland Delineation-A determination that a water body or wetland is subject to interstate commerce, and therefore is a water of the United States. Wetland Functions - Wetland functions are the ecological functions that wetlands perform. Wetland functions include providing flood control, water quality protection shoreline stabilization, contributions to ground water and stream flows, wildlife and fisheries habitat, and aesthetic, recreational, and education opportunities. i City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan Glossary-3 January 2001 IIKIRKLAND_IIVOLIIDATAI"rkingl1 7 791554-1 779-0 7IMIT BANK PLAN-revise part II 1-01.doc 1 1 Appendices should be a separate document and include at a minimum the following(see city edits): 1 1 1. Glacier park mitigation bank agreement 2. Wetland delineation reports 1 3. CORP delineation confirmation 4. Dames and Moore 1 5. Northwest hydrologic 1 6. Hong West 7. Capacity analyzes 8. Crest stage/monitoring well 9. Sample MOA 1 1 1 i 1 i 1 1 1 1 APPENDIX A City of Renton Wetland Management Ordinance APPENDIX B Wetland Functional Evaluation Form and Instructions to Use Form APPENDIX B WETLAND FUNCTIONAL EVALUATION 1 The wetland functional evaluation form is a methodology for determining (1) the functions and relative value of the function a given wetland provides and; the type of compensation in terms of function and value, that should be provided in the form of mitigation. This form is intended to be used after the location and boundaries of a wetland are delineated. The person(s) conducting the functional evaluation should have experience and/or education with wetlands and identifying wetland functions. The more experience the person(s) has with wetlands the quicker and more accurate the results will be. If possible, document the sources of information for making determinations. 1. Fill out the Form Complete the background information. Record the project name,name of wetland(if known), location(e.g., City of Renton, King County), the government jurisdiction, the name of the recorder(s), date, and section, township,and range. 2. Wetland Condition 1 Determine the percent cover of exotic or invasive species within the wetland. A list of exotic and invasive species is in the Washington State Wetlands Rating System, Western Washington (Washington Department of Ecology, 1993). Look for evidence of hydrological alteration including ditching, draining, diversions, darns, etc. A good source of information for identifying hydrologic alterations is historic and current aerial photographs, and topographic maps. Determine the extent of other human or natural impacts such as the presence of debris and garbage, filling, clearing, and grading. If possible, determine when these impacts occurred. Evidence of pollutant inputs can be assessed by reviewing site assessment data for the property and aerial photographs, and by walking through the site. 3. Buffer Condition If available, review a current aerial photograph of the wetland to determine the type and extent of buffer ' associated with the wetland. An on-site inspection of land surrounding the wetland will also provide information on the type and extent of buffer associated with the wetland. 4. Biological Support Determine the size of the wetland (this information should be available from the wetland delineation) and record the value of the buffer condition. ' Identify the number of wetland classes. Examples of wetland classes include open-water area, submerged aquatic bed, emergent, scrub-shrub, and forested vegetation communities. The number of wetland classes City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan B-1 January 2001 IIKIRKLAND_1I VOLT IDATAI worldngl1 7 791554-1 7 79-0 71MIT BANK PLAN-revise part 17 I-OLdoc can be determined by walking through the wetland and either developing a sketch of the distribution of wetland classes or recording the number of classes encountered during the walk-through. ' Count the number of different plant species within each wetland class. Each species found should cover at least five percent of the ground within the area covered by that class. ' Determine whether open-water area occurs within the wetland. An open-water area is any area of standing water that is present in any year for more than one month at a time without emergent, scrub-shrub,or forested vegetation (Washington Department of Ecology 1993). At certain times of the year it may be difficult to ' determine whether open water is present. Use aerial photographs,talk with landowners,and look for dried or muddy areas without vegetation which indicate that open water was present earlier in the year, or in past years(Washington Department of Ecology 1993). Interspersion of vegetation classes is a measure of the complexity of wetland classes. For example, interspersion of vegetation classes would be termed"simple"if the vegetation consisted of a single emergent ' community. Interspersion of vegetation classes would be"moderate"or"complex"if a mixture of vegetation classes was present. 1 Determine whether a part of the wetland boundary has a surface water connection to seasonal or perennial flowing surface water (including floodwater)by way of a channel (man-made or natural) or an area of open water. Look specifically for a wetland inlet and outlet. Habitat features include downed logs, snags,evidence of beaver usage, open water, etc. Identify the number of habitat features and record the types of features present. Determine whether there are any habitat corridors in proximity to the wetland. Habitat corridors can include a natural upland, or wetland areas including parks, rivers, lakes, or other areas that are essentially undisturbed. 5. Water Quality Determine the percentage of vegetation cover(considering all wetland vegetation classes)within the wetland. Estimate the rate at which water moves through the wetland. Determining the rate of water movement may be difficult at certain times of the year. Talk to the landowner and the City of Renton to determine whether there is existing information on water flow near or through the wetland. Estimate the average slope of the area within 200 ft. of the wetland. Record findings for pollution/sediment inputs from the Wetland Condition. 6. Flood and Storm water Desynchronization Estimate the potential storage capacity by determining the depth of the depression in which the wetland occurs and the extent of the wetland in acres. The location of the wetland within the watershed indicates the relative value of the wetland for providing flood and storm water attenuation. The location of the wetland can be determined using aerial photographs and topographic maps. Wetlands associated with rivers and streams have a higher functional value for attenuating flood and storm waters. Determine whether the wetland is isolated or connected to a river or stream. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan B-2 January 2001 IIKIRKLAND_II VOLIIDATAI"rldng11779U54-1779-07WIT BANK PLAN-revue part III-01.tioc Estimate the percentage of emergent and woody vegetation that is dense, moderately dense, or moderate to sparsely dense. Record the size of the wetland. Estimate the length of water inundation in the wetland. A site visit, along with a review of current aerial photographs and the National Wetland Inventory map will, generally provide enough information to Idetermine the length of inundation. 7. Ground Water Exchange ' General methods for measuring groundwater exchange, such as the installation of piezometers and groundwater wells, require that an individual record water levels for at least one year or longer. The functional evaluation methodology evaluates indicators of groundwater exchange. A review of geotechnical information from the site and the Soil Survey of King County, and an on-site soil inspection can provide information on the presence of a confining layer. Using data collected to determine the hydroperiod and hydrologic connectivity, estimate the potential value of the wetland for providing a groundwater recharge ' function. 8. Support of Base Flow If the wetland borders a stream, determine whether the ,stream is intermittent, seasonal, or permanent. Identify what type of habitat occurs downstream.Identify the proximity of the wetland to the stream. 9. Cultural Values Identify any scenic vistas that exist within or on the wetland perimeter. Estimate the aerial coverage of open water present on the wetland. Determine whether the wetland has access, and identify wetland ownership. Identify the number of wetland types or classes. Try to determine whether the wetland has or is being used for scientific or educational proposes. Determine whether the wetland is part of the City of Rentoris Park Plan. 10. Shoreline Stabilization Determining the value of the wetland to provide shoreline stabilization requires the consideration of two parameters: • Identifying whether the wetland is bordering a shoreline with no to long fetches,and • The density of the wetland vegetation. Evaluating Results Total the points for each characteristic/function. With the exception of wetland condition, the higher the number of points, the more valuable the wetland is in providing the specified function. It is possible to have close totals for low, medium, and high ratings. For example, the biological support function of Mitigation I Banking Site 1 was rated as low (6 points), moderate (4 points), and high (3 points). In this situation, best professional judgement is typically applied. The overall value of Mitigation Banking Site 1 to provide biological support was rated as low to moderate because the total number of characteristics that help to define biological support for the site are limited or absent. Interpreting the Results City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan B-3 January 2001 ' IWIRKLAND_II VOL]DATA 1w rkinglI7 791554-1 779-0 7WIT BANK PLAN-revise part H I-01.doc The results of the functional evaluation can be used in three ways. First,the results identify the function(s) a wetland provides and the relative value of that f inction(s). For example, the functional evaluation for ' Mitigation Banking Site 2 under existing conditions indicates that the value of the majority of functions provided by the existing wetland is low. Second, the results of the functional analysis can be used to determine which functions of a given wetland are most valuable and would need to be mitigated for if the wetland were altered. Third, the evaluation form can be used to demonstrate the functions that would be created and/or improved with wetland mitigation. For example, Table 5 indicates that the value of functions to be provided in Mitigation Banking Site 2 including water quality improvements, flood and storm water attenuation, support of base flow to Springbrook Creek,cultural values, and shoreline stabilization would be ' high. City of Renton 553-1779-009 Draft-Wetland Mitigation Banking Plan B-4 January 2001 IIKIRKLAND_11 VOLIIDATAIworldngll7791554-1779-071MIT BANK PLAN-revise part 111-01.doc APPENDIX C Photographs of Soil Tests Locations on Mitigation Banking Site 2 r r r r r r r r r r r rAPPENDIX D rCompleted Wetland Functional Evaluation Forms for Mitigation Banking Sites 1 and 2 r r r r r r 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 C:\My Documents\Renton\revise Part I 3.98.doc ' CITY OF RENTON ' WETLAND MITIGATION BANKING PROGRAM PLAN ' Prepared for ' CITY OF RENTON 200 Mill Avenue Renton, Washington 98055 t Prepared by ' PARAMETRIX, INC. 5808 Lake Washington Blvd. NE Kirkland, Washington 98033 January 2001 1 City of Renton -FINAL DRAFT i 55-1779-07 ' January 1995 1 ' EXECUTIVE SUMMARY ' This Mitigation Banking Plan describes a wetland mitigation banking program and plan for the City of Renton (the City) that is consistent with the City's Wetland Management Ordinance and ' Comprehensive Plan. The City's wetland ordinance defines a policy of no net losses of wetland resources while optimizing ecological benefits and providing a solution for promoting controlled economic growth in compliance with the state of Washington's Growth Management Act. The ' Mitigation Banking Plan is a method by which contiguous, high functioning wetlands are created in the Black River Drainage Basin to offset the loss of isolated, poorly functioning wetlands that may ' occur as a result of private and public development. The City's decision to develop a mitigation banking program and plan results from completion of an ' inventory of wetlands within the City of Renton jurisdiction, adoption of a wetlands ordinance, and discussions with landholders in the Green River Valley about mitigation banking. The City's wetland inventory indicated numerous small wetlands in heavily developed and urbanized area of ' the Valley. In 1992, Renton's City Council passed a Wetlands Ordinance that provided opportunities to establish a wetland mitigation bank. Properties in the Valley with wetlands that met certain criteria could join a mitigation-banking program as long as the result was no net loss of ' wetland area. Two sites are currently planned for mitigation banking: Mitigation Banking Site 1 (Site 1) and ' Mitigation Banking Site 2 (Site 2) total 44.80 acres. Site 1 is north of SW 34th Street, south of Boeing Longacres Park, east of Burlington Northern Railroad, and west of Oakesdale Ave. SW. The site is 30.97 acres. The site is primarily of fill material that includes 12.19 acres of uplands and ' 18.78 acres of emergent, scrub-shrub, and forested wetlands. Site 2 is located south of SW 34th Street,west of Springbrook Creek,north of SW 40th Street and east of Oakesdale Avenue SW. The site is 13.93 acres and consists of 7.24 acres of upland and 6.69 acres of emergent and scrub-shrub wetlands that have developed on fill. The Mitigation Banking Program defines the overall goal, objectives, and policies associated with ' the program. They City's goal is to create a wetland mitigation banking program consistent with the City's Wetland Ordinance, Comprehensive Plan, and Wetland Mitigation Bank Agreement. Objectives were developed to refine the goal and its intentions. Policies, taken primarily from the ' Comprehensive Plan,were appropriate to achieve the objectives were also developed. The Mitigation Banking Program provides background information on wetlands within the Black ' River Drainage Basin whose impacts may potentially be offset at the mitigation banking sites. A total of 34 wetlands (includes Category 1, 2, and 3) ranging in size from less than 1 acre to approximately 65 acres are potentially eligible to use the mitigation banking sites. ' The Mitigation Banking Program also defines the institutional framework for using, managing, and administering the Mitigation Banking Program. Private and public projects that impact wetlands are 1 ' City of Renton-FINAL DRAFT ii 55-1779-07 January 1995 ' considered eligible to use the banking program. Eligibility criteria for use of the banking program were developed, and are based on ecological considerations and regulatory requirements. Project ' proponents would use the eligibility criteria and standards to determine if impacts to wetlands may be compensated at the mitigation banking sites. Specific federal, state, and local regulatory requirements associated with filling wetlands and using the mitigation banking program are also ' identified and discussed in this document. A credit and debit system for valuing the compensation credits produced and for determining the ' type and number of credits needed as compensation for any particular project was developed as part of the Mitigation Banking Program. The system to determine credits and debits is based on both ' wetland acreage and wetland functions. A functional evaluation methodology was developed to promote consistent evaluations wetland function and to determine how well the wetland mitigation banks produce those functions. ' Preliminary costs,from preparation of final construction drawings and specification through the first year of monitoring and maintenance, were estimated. These estimates are considered preliminary ' and must be refined when final site plans are developed. Preliminary cost estimates indicate that the average cost per acre to construct wetlands on the mitigation banking sites is about $25,000 (1995 estimate). The final cost estimate will be used to determine the user fees needed to cover costs ' associated with implementing the Mitigation Banking Program and Plan. The City of Renton Public Works Department will be the agency with primary responsibility for administering the wetland mitigation-banking program. The city will actively pursue opportunities to work with other city agencies, state and tribal agencies, environmental and community organizations, and the private sector to create the wetlands and wetland functions on the mitigation ' banking sites and to assist with monitoring and maintenance. t PART I MITIGATION BANKING PROGRAM ' 1. INTRODUCTION ' The City of Renton is developing a wetland mitigation banking program consistent with the City's Wetland Management Ordinance (Ordinance Number 4346) (City of Renton 1992) and ' Comprehensive Plan (City of Renton 1993a). The mitigation banking program is a method by which relatively large, highly functioning wetlands are created to offset losses of isolated, poorly functioning wetlands (often due to private and public development). The program implements the ' policy of no net loss of wetland resources. It optimizes ecological benefits by siting mitigation near existing wetlands or creek systems and provides an effective solution for maintaining or improving ' City of Renton-FINAL DRAFT iii 55-1779-07 January 1995 1 ' the function of wetland systems while allowing economic growth in compliance with the state of Washington's Growth Management Act. ' The wetland mitigation-banking program would create large, high quality contiguous wetlands in the Black River Drainage Basin. These created wetlands would be used to offset filling of lower quality wetlands following private and public development that may occur in the same drainage basin. ' The concept of developing a mitigation-banking program at the Site 1 resulted from three primary actions: (1)the City undertaking an inventory of its wetlands, (2) the City developing and adopting ' a critical areas ordinance for wetlands (City of Renton 1992) pursuant to the Growth Management Act and, (3) discussions between the City and Glacier Park, a private landholder in the Valley, on the concept of mitigation banking. During the wetlands inventory, the City found that a number of ' wetlands considered "high-value" still located within the Black River Drainage Basin. There were also wetlands of lower quality that had been impacted by previous land-use activities that were relatively small and isolated from other ecological systems. Figure 1 shows the Black River ' Drainage Basin. Figure 2 shows the extent of inventoried wetlands and streams of the Black River Drainage Basin within the City of Renton municipal boundary and sphere of influence. The extent of wetland impact is a direct result of historic activities and conditions in the Green River Valley. ' City of Renton-FINAL DRAFT 4 55-1779-07 January 1995 Originally, the majority Green River Valley (hereafter referred to as the Valley) consisted of slope, ' depressional and riparian wetlands. Figure 3 shows the extent of natural wetlands prior to extensive ' Figure 1. Black River Drainage Basin.. Figure 2. Inventoried Wetlands and Streams, City of Renton ' City of Renton-FINAL DRAFT 5 55-1779-07 January 1995 ' development/fill activities in the Renton Valley in 1972. During the 1960s and 1970s draining and filling activities associated with conversion from agricultural to commercial and industrial use ' resulted in cumulative losses of wetlands within the Valley. Figure 4 shows the extent of filling to 1987. Although many of the filled areas were developed, some filled areas were not, and topographic lows within the fill collected surface runoff. These topographic lows on fill perched ' water and eventually developed into wetlands on fill. Generally these isolated wetlands on fill either lack wetland function or have highly reduced functional capacity. Glacier Park Company, a subsidiary of Burlington Northern Railroad, owned many of these undeveloped parcels in the Valley. City of Renton -FINAL DRAFT 6 55-1779-07 January 1995 In 1992 Renton's City Council passed a Wetlands Ordinance (City of Renton 1992) that provided Figure 4. Approximate Extent of Filling in the Renton Valley to 1987. ' Figure 3. Natural Wetlands in 1972 Prior to Extensive Renton Valley Development/Fill. ' City of Renton -FINAL DRAFT 7 55-1779-07 January 1995 ' opportunities to establish a wetland mitigation bank. Properties within the Valley that met certain criteria could establish and/or join an existing mitigation banking program, as long as the result was ' no net loss of wetland acreage, function, or value. Users of the bank would also realize cost savings from coordinating with other mitigation efforts on a single bank site. Concurrent with the development of the City's ordinance, Burlington Northern (BN) decided to divest some properties ' held by the Glacier Park Company. BN also wanted to improve the market value of some of its Valley properties. After meeting with the City to develop a mitigation banking agreement, Glacier Park donated two large parcels to the City (Figure 5) that contained larger wetlands. In exchange, ' the City allowed Glacier Park to make some smaller parcels containing lower quality wetlands more saleable by agreeing to issue permits for filling a total of 4.11 acres on six different parcels. r City of Renton-FINAL DRAFT 8 55-1779-07 January 1995 r 1 ' Figure 5. Renton Valley Drainage Patterns, Mitigation Banking Sites 1 and 2, and Glacier Park Sites. 1 1 ' City of Renton-FINAL DRAFT 9 55-1779-07 January 1995 ' The City's two mitigation banking sites, Mitigation Banking Site 1 (Site 1) and Mitigation Banking Site 2 (Site 2)total 44.80 acres. These sites are to be used for compensatory wetland mitigation for ' the six parcels originally under Glacier Park ownership (see Figure 5), and for mitigation banking by other public and private developments to offset losses to lower quality wetlands. ' Site 1 is located north of Southwest 34 h Street, south of the Boeing Longacre Park site, east of the Burlington Northern Railroad, and west of Oakesdale Avenue Southwest. The site is 30.97 acres ' and is partially zoned industrial. It is bordered along most of the southern boundary by developed land zoned for industrial development. Undeveloped commercial and industrially zoned land is adjacent to the western half of the southern boundary and to the eastern and western boundaries ' (David Evans and Associates 1991 a). The site consists primarily of revegetated fill material and ranges from 18 to 20 ft. in elevation (placed approximately 20 years ago), consisting of approximately 12.19 acres of relatively undisturbed upland meadow and shrubland, and 18.78 acres of young forested and shrub wetlands. Site 2 is located south of Southwest 34th Street, west of Springbrook Creek, north of Southwest ' 40th Street, and east of Oakesdale Avenue Southwest (Sec 25, T 23N, R 4E) (see Figure 5). The site was filled over the past 20 years; the topography is relatively flat (15 to 18 ft. in elevation) with small depressional areas. It is bordered to the north by undeveloped industrial and commercially zoned land. ' Once the City acquired the two mitigation banking sites, it assembled an interdepartmental team consisting of City representatives from Surface Water Utility,the Mayor's office,the City Attorney's ' office, Planning, and Parks and Recreation. The team will develop and manage a mitigation banking plan(City of Renton 1993b). Once the plan is finalized and approved by the City,the plan and mitigation program will be implemented. The City intends to operate, maintain, and monitor the mitigation banking sites. ' City of Renton -FINAL DRAFT 10 55-1779-07 January 1995 ' 2. GOAL, OBJECTIVES,AND POLICIES OF THE MITIGATION BANKING PROGRAM A primary goal, objectives to meet that goal, and policies that are guiding principles for the ' mitigation banking program are presented below. 2.1 GOAL ' Create a wetland mitigation banking program and plan that are consistent with the City's Wetland g g p t� P tY Management Ordinance (City of Renton 1992), Comprehensive Plan (City of Renton 1993a), and Wetland Mitigation Bank Agreement. ' 2.2 OBJECTIVES Objectives have been developed to refine the goal and its intentions. These objectives, primarily taken from the City of Renton's Comprehensive Plan (City of Renton 1993a) and Wetland Management Ordinance(City of Renton 1992; Section 4,Chapter 32,Renton City Codes),are listed below: Encourage community development patterns and site planning that maintain and enhance natural systems, forms, and open spaces (EN-2.0, Comprehensive Plan). Balance community desires for economic development with the responsibility to retain the City's wetlands base and protect environmental resources(4-32.18,Renton City Code). Protect and enhance water quality of surface water resources (EN-4.0, Comprehensive Plan). Provide for, and work toward, a regional approach to storm water management programs (EN-10.0,Comprehensive Plan). ' Protect and enhance the City's rivers, major and minor creeks and intermittent stream courses(EN-5.0,Comprehensive Plan). ' Maintain and strive to increase surface storage capacity, to decrease surface and flood runoff, and increase groundwater recharge to maintain stream base flow (4.32-1.A., Renton ' City Code and Wetland Mitigation Bank Agreement) Protect the natural functions of 100-year floodplains and floodways (EN-7.0, ' Comprehensive Plan) Preserve and protect wetlands for overall system functioning(EN-6.0,Comprehensive Plan) ' City of Renton -FINAL DRAFT 11 55-1779-07 January 1995 Prevent loss of wetlands and strive for a net gain over present conditions (4.32-1.B, Renton ' City Code) Consolidate wetland mitigation onto the Mitigation Banking Sites for the Black River ' Drainage(Wetland ordinance 4.32-6.F and Wetland Mitigation Banking Agreement) Protect and enhance wildlife habitat(EN-14.0, Comprehensive Plan) Support and sustain educational informational and public involvement programs in the City PP p p t� ' over the long term to optimize the use, preservation, and protection of Renton's water resources(EN-11.0,Comprehensive Plan). 2.3 POLICIES Policies that are considered to be prudent and advantageous to achieving the objectives and goal of the mitigation banking program are presented below. Manage water resources for multiple uses including recreation, fish and wildlife, flood protection, erosion control, water supply, energy production, and open space (EN-4.1, Comprehensive Plan). ' Design new development or land modifications within the 100-year floodplains to maintain natural flood storage functions and minimize hazards (EN 7.4, Comprehensive Plan). ' Preserve natural surface water storage sites that help regulate surface flows and recharge groundwater(EN-8.2, Comprehensive Plan). ' Use, maintain, and enhance the natural storm water storage capacity provided in existing significant wetlands(EN-8.10,Comprehensive Plan). ' Manage cumulative effects of storm water through a combination of engineering and preservation of natural systems(EN-9.4, Comprehensive Plan). Achieve no net loss of the City's remaining wetlands(EN-6.1, Comprehensive Plan). Provide incentives for overall net gain of wetland functions and values for new development (EN-6.7, Comprehensive Plan). Emphasize non-structural methods in planning for flood prevention and damages reduction ' (EN-7.6). ' City of Renton -FINAL DRAFT 12 55-1779-07 January 1995 ' Establish and protect buffers along wetlands to facilitate infiltration and maintain stable water temperatures, provide for the biological regime, reduce the volume and velocity of ' runoff,and provide wildlife habitat(EN-6.2, Comprehensive Plan). Encourage preservation and enlargement of existing habitat areas through development ' incentives(EN-14.3, Comprehensive Plan). Increase the community's understanding of the City's ecosystem and the relationship of the ' ecosystem to water resources(EN-11.2,Comprehensive Plan). ' Encourage public access to wetlands for use when sensitive habitats are protected (EN-6.9, Comprehensive Plan). ' Where appropriate, combine all critical areas and environmentally sensitive areas with recreational facilities to provide public access and trail linkages through separators (EN- 15.7,Comprehensive Plan). ' City of Renton-FINAL DRAFT 13 55-1779-07 January 1995 ' 3. POTENTIALLY ELIGIBLE WETLAND ACREAGE ' Two primary sources were used (Jones and Stokes 1991 and R.W. Beck and Associates 1993) to assess wetlands within the Black River Drainage Basin whose impacts may potentially be offset at the mitigation banking sites. Table 1 was created using wetlands information from these earlier ' documents. Approximately 37 wetlands were identified within the Black River Drainage Basin— the majority occur within the City of Renton limits (see Figure 1). Of all the inventoried wetlands, 34 have been classified as either Category 1, 2, or 3 wetlands, according to the City's Wetland ' Management Ordinance (City of Renton 1992; see Table 1). Of these, 20 wetlands (58 percent) are rated as Category 3 wetlands, 11 (32 percent) are rated as Category 2 wetlands, and 3 (10 percent) ' are rated as Category 1 wetlands. Approximately 7.0 percent of wetlands inventoried in the City of Renton are not categorized. Since the City will consider mitigation proposals for the mitigation banking sites that involve impacts to Category 1, 2, and 3 wetlands, a total of 34 wetlands are potentially eligible to use the mitigation banking sites. The 34 potentially eligible wetlands represent approximately 445 acres. ' Estimates of wetland acreage by wetland category are provided in Table 2. Actual wetland acreage potentially affected will be based on individual findings at specific sites and by specific wetland delineation. Table 1. Inventoried wetlands within City of Renton limits. ' Wetland Code' Wetland Type Size(acres) Category 1 W43 PFO,PSS,PRM 65 ' W-5 PFO 20 W-123 PSS,PEM 41 Total 3 Category 22 ' W-25 PFO 1 or less W40 PEM,PSS W-43 PEM ' W-3 POW,PFO,PEM 5-6 W-38 PFO,PSS,PEM W-7N PEM,PSS 11-12 W-8N PSS,PEM ' W-13C POW,PEM,PSS W-10 PFO,POW 12-13 W-45 PFO,PSS,PEM W-5C PFO,PSS 23 Total 12 Category 3 W-54 PEM 1 or less ' W-31 PFO,PEM W-34 PEM W-35 PEM W-56 PSS,PFO,PEM 1-2 City of Renton-FINAL DRAFT 14 55-1779-07 January 1995 Wetland Code' Wetland Type Size(acres) ' W-9 PFO W-16 PEM,PSS W-36 PEM W-6 PFO,PSS 2-3 ' W-75 PSS,PEM W-15 PFO,PSS W-41 PSS,PEM ' W-14 PSS,PEM 3-4 W-33 PEM,PSS W-85 PSS,PEM 4-5 W-13a PFO,PEM,PSS W-21 PEM,PSS W-32 PFO,PSS 6-7 W-223 PEM,PSS,PFO 18-19 W-13b PEM 20 ' Total 20 Note: A portion of W-22 is Wetland Mitigation Site l;A portion of W-32 is Wetland Mitigation Site 2. From R.W. Beck 1993, Black River Basin Draft Water Quality Management Plan, Volume 3 and Jones, and Stoke 1991, Critical Areas Inventory,City of Renton Wetlands and Stream Corridors. z Category is based on City of Renton wetland ordinance. ' Owned by the City of Renton. PEM=Palustrine emergent POW=Palustrine open water PSS=Palustrine scrub shrub PFO=Palustrine forested Table 2. Approximate total acreage of wetlands in the Black River Drainage Basin by category. Wetland Category Acreage(approximate%) 1 126(28) ' 2 217(48.5) 3 71 (16) Uncategorized 31 (7.5) ' Total 445 ' City of Renton-FINAL DRAFT 15 55-1779-07 January 1995 ' 4. PRIVATE AND PUBLIC USE OF THE MITIGATION BANKING PROGRAM 4.1 ELIGIBILITY CRITERIA ' In general, eligibility criteria for use of the mitigation banking program are based on ecological considerations and regulatory requirements. The eligibility criteria for the City's program would ' determine which wetlands in the Black River Drainage Basin may be altered and subsequently compensated for at a mitigation banking site. A draft list of eligibility criteria and standards for the ' eligibility criteria are presented below. This list of eligibility criteria and associated standards will be used by project proponents and the City to determine whether impacts to wetlands may be compensated for at the mitigation banking sites. Meeting the standards of each criterion will be ' necessary before the City's mitigation banking program can be used. A simplified flow chart of the eligibility criteria is shown in Figure 6. This can be used in conjunction with the standards to determine whether mitigation banking should be considered. ' City of Renton-FINAL DRAFT 16 55-1779-07 January 1995 ELIGIBILITY ' CRITERIA 1: Does the proposed project comply with the City Wetland Management Ordinance (Ordinance Number 4346)? Standard Projects that have unavoidable and necessary impacts to waters of the U.S., including wetlands, ' Figure Flow t n 1'gur 6. o Chart o Determine Eligibility for Use of Mitigation Banking Program. ' City of Renton-FINAL DRAFT 17 55-1779-07 January 1995 ' would be considered for incorporation in the wetland mitigation banking program, provided that they demonstrate compliance with all other standards of the City's ordinance. For example, use of ' the mitigation bank to compensate for wetland impacts would be tied to the mitigation policy of sequential mitigation actions including avoiding adverse impacts, taking affirmative measures to minimize impacts, and compensation for impacts. Mitigation banking is basically a form of ' compensatory mitigation. In addition, the mitigation should be comprised of the same or higher category habitat than the altered habitat, so that similar or greater functions and values in the drainage basin are achieved [see Section 4-32-6 (A)(2) of the Wetland Management Ordinance], ' and the City's standards for wetland creation and/or restoration are met. ' ELIGIBILITY CRITERIA 2: Is the proposed project located within the City of Renton portion of the Black River Drainage Basin? ' Standard ' The altered wetland must be located within the City of Renton portion of the Black River Drainage Basin, including the Green River Valley. ' ELIGIBILITY CRITERIA 3: Has the U.S. Army Corps of Engineers completed a wetland jurisdictional determination on the wetlands to be impacted? ' Standard ' Wetlands classified by the City as Category 1, 2, or 3 that may be altered consistent with the Wetland Management Ordinance (Ordinance Number 4346) are potentially eligible to use the mitigation banking sites. ' A delineation of wetlands may potentially be altered is required by one or more of the following: the U.S. Army Corps of Engineers (Corps),the State of Washington, and City of Renton. The Corps is ' the federal agency responsible for completing a jurisdictional determination on delineated wetlands. A jurisdictional determination includes verification of the wetland delineation and a determination of whether the site is considered to be adjacent, above the headwaters, or isolated. Written ' documentation from the Corps on the jurisdictional status of the wetland to be altered is required. Impacts to wetlands that require an individual permit(Section 404)from the Corps and/or the Corps ' and Ecology may also be compensated for at the mitigation banking sites. A developer would need to provide the City with a copy of the appropriate permit along with written documentation that the state and federal agencies concur on using the mitigation banking sites for compensatory mitigation. ' ELIGIBILITY CRITERIA 4: Has the applicant complied with the sequencing of wetland mitigation? ' City of Renton -FINAL DRAFT 18 55-1779-07 January 1995 Applicants must demonstrate that they have tried to avoid impacts to wetlands, minimize impacts ' where impacts are unavoidable or on-site mitigation is not feasible or practicable, and that off-site mitigation is the only feasible mitigation alternative. ' ELIGIBILITY CRITERIA 5: Is on-site mitigation feasible? Standard The wetland to be altered would be considered eligible for use of the mitigation banking program i when: ' The hydrology and ecosystem of the original wetland and those adjacent lands and/or wetlands which benefit from the hydrology and ecosystem will not be substantially damaged by the on-site loss; and ' On-site mitigation is not feasible (due to problems with hydrology, topography, soils, location or surroundings of the subject property,surrounding land uses); or On-site compensation is not practical due to potentially adverse impacts from surrounding land uses; or ' Existing functional values at the proposed mitigation banking site are significantly greater than lost wetland functional values; or ' Established regional goals for flood storage, flood conveyance, habitat, or other wetland function have been addressed and strongly justify location of compensatory measures at the ' mitigation banking sites(City of Renton 1992). 4.2 REQUIREMENTS TO USE MITIGATION BANKING PROGRAM Some of the federal, state, and local requirements to use the mitigation banking program are described in Section 4.1. Specific permits are required by federal, state, and local agencies to fill ' wetlands;these requirements are identified below. 4.2.1 Federal Requirements ' The most important federal permit required for dredging or placing fill in a wetland is Section 404 of the Clean Water Act (Clean Water Act § 404; 33 USC § 1344; 33 CFR 320 et seq.; 40 CFR Part 230). The Corps' Seattle District Office is the federal agency responsible for implementing Clean Water Act regulations. Appropriate permits must be obtained from the Army Corps of Engineers City of Renton-FINAL DRAFT 19 55-1779-07 January 1995 1 1 4.2.2 State Requirements ' 4.2.2.1 State Environmental Policy Act(SEPA) ' All state and local permits or approvals issued for construction or operation of the facility must comply with the procedural requirements of SEPA. The lead agency reviews the SEPA checklist and issues one of the following threshold determinations: ' A Determination of Nonsi ficance DNS ' Mitigated Determination of Nonsignificance(MNDS) SEPA Environmental Impact Statement ' The City of Renton is typically the lead agency for SEPA determinations. SEPA review must precede the issuance of any state or local permits or approvals by 7 days. An EIS with its associated studies generally takes from 10 months to 1 year to complete, assuming no appeals. As with the ' National Environmental Policy Act, supplemental environmental review is required only if there are: (1) "substantial changes to a proposal so that the proposal is likely to have significant adverse environmental impacts"; or (2) "new information indicating a proposal's probable significant ' adverse environmental impacts." 4.2.2.2 Hydraulic Project Approval(HPA) ' An HPA may be required if a project crosses and/or affects fresh water streams. The Washington Department of Fish and Wildlife is the agency responsible for administering the hydraulic codes ' (Ch. 75.20 RCW; Ch. 220-110 WAC). An HPA application must be processed within 45 calendar days of the submission of a complete application and after issuance of a final EIS. No public hearing is required. Permits must demonstrate "substantial progress on construction on that portion ' of the project relating to hydraulic approval within 2 years of the date of issuance." HPA approvals may be granted for a period of up to 5 years. ' 4.2.2.3 Temporary Modification of Water Quality Criteria This permit is required for construction activities that temporarily violate water quality criteria and ' may be required for stream diversion structures. Ecology's Northwest Regional Office is the lead agency (Ch. 90.48 RCW; WAC 173-201 and 173-222). In general, temporary water quality modification must be sought 30 days prior to any in-water work. Permit terms and conditions ' generally cover duration of work requiring the modification(usually 1 year). 4.2.2.4 Water Quality Certification ' A certification is required from Ecology to conduct activity that may result in any discharge to surface waters (i.e. Section 404 permits; Federal Clean Water Act, Section 401; 173-225 WAC). City of Renton -FINAL DRAFT 20 55-1779-07 January 1995 ' Ecology (Headquarters Central Programs, Environmental Review Section, Olympia) issues water quality certifications. ' 4.2.2.5 Coastal Zone Management Program Consistency Certification ' This certification is required for permits and licenses affecting shoreline areas (16 USC §1451 et seq.; 15 CFR parts 923-930) and is usually considered during the Section 404. Ecology's Shorelines Program(Olympia)is the lead agency. Certification can generally be obtained in 60 days. ' 4.2.3 Local Requirements t4.2.3.1 Shoreline Substantial Development Permit ' A shoreline permit is required for any substantial development within 200 ft of a shoreline area, pursuant to the City of Renton Shoreline Master Program (RCC 4-19). A permit can usually be obtained in 4 to 6 months. Shoreline permits are valid for 2 years,and extensions are possible. ' 4.2.3.2 Sensitive Area Regulation The City of Renton regulates wetlands through a sensitive areas ordinance (City of Renton RCC 4- 32; City of Renton 1992; Appendix A). Activities in regulated wetlands and wetland buffers must comply with the requirements of the ordinance. The extent of regulatory control, replacement ' ratios, and mitigation depends on the category of wetland to be impacted. Compliance with the City's sensitive areas ordinance occurs upon submittal of any building or land use permit application and/or upon obtaining approval of use and/or development of land. This permit is valid for 2 years, ' and extensions are possible. ' City of Renton-FINAL DRAFT 21 55-1779-07 January 1995 5. CREDIT AND DEBIT SYSTEM ' The mitigation banking program requires a system for valuing the compensation credits produced and for determining the type and number of credits needed as compensation for any particular project (Environmental Law Institute 1993). Defining mitigation banking ' credits requires that those features, which allow reasonable approximations of replacement, be identified. ' The assets accrued in the City's mitigation banking program will exist as credits measured in units of both acres and function. The functional evaluation method is intended to be consistently applied by different individuals or by the same individual at different times. It is also intended to be used to compare existing with future conditions at the mitigation banking sites,and to compare existing conditions of wetlands that may be impacted. ' Thus,the functional evaluation methodology will be used by: Applicants or applicants' consultants who are considering use of the mitigation ' banking program to assess potential impacts from private and public projects, The City of Renton to assess potential impacts to wetlands from public projects,and ' The City of Renton to assess those functions and values associated with implementing the mitigation banking plan for the duration of the monitoring ' program. A methodology that recognizes both acreage and function assures consideration of function ' and how well the wetland mitigation banks produces those functions. The acreage and results of the functional evaluation methodology will be translated into a "currency." The methodology to be used to characterize wetland functions is not original; rather, it is adapted from two existing methodologies: Ecology's Washington State Wetlands Rating System for Western Washington(Ecology 1993), and Wetland Values(Reppert et al. 1979). These two methods are commonly used by wetland ecologists to identify and evaluate wetland ' functions, and are relatively easy to use. The intent is to provide a methodology that is understandable. Other existing functional assessment methodologies were not adopted for several reasons, including: Difficulty in understanding the details of the methodology unless the individual has considerable experience with wetlands. Potential difficulties with obtaining and/or accessing computer software. ' No one method is considered more valid or reliable than another. Users of the proposed methodology must understand that the methodology to assess credits and debits is not flawless. For example, although there are no, or limited, evaluation City of Renton-FINAL DRAFT 22 55-1779-07 ' January 1995 methodologies for some wetland functions, general ecological principles can be adapted and best professional judgement can be applied and documented. 5.1 ACREAGE DETERMINATION ' The methodology used to determine the wetland acreage to be impacted is a standard process in wetland evaluations. The process is as follows: l. A project proponent completes a wetland delineation. 2. The project proponent retains surveyors to survey the flagged wetland delineations. 3. The survey company produces a map showing the location and size of the wetland(s). The area that may potentially be impacted is determined and expressed ' in either acre(s),square feet,or both. 5.2 FUNCTIONAL DETERMINATION ' The functional evaluation method measures the ability of the wetland to carry out selected functions. Appendix B includes a functional evaluation form and instructions on using the ' methodology form. A general description of wetland functions evaluated by the proposed methodology is presented below. ' Wetland Conditions The general condition of wetlands provides important information on current and historical impacts to the wetland including alterations to hydrology, evidence of solid and liquid pollutant inputs, and other human-induced impacts. A high wetland condition rating indicates that the wetland has been altered and impacted. ' Buffer Condition ' Wetland buffers are the interface between wetlands and uplands. Buffers protect wetland vegetation and provide key habitat components. Buffers can be native vegetation, open- water areas, roads, industrial, commercial and residential development, conservation areas, ' etc. Narrow buffers and buffers such as paved roads provide minimal protection to wetlands, while wide (e.g., 50 to 100_) native vegetation buffers provide more protection. A high buffer condition rating indicates the presence of natural buffers that provide ' protection. City of Renton -FINAL DRAFT 23 55-1779-07 January 1995 ' Biological Support Wetlands provide habitat and food for many wildlife resources. Some species of waterfowl and fresh and saltwater fish are dependent on wetland habitat for a portion of their life history for breeding,nesting,rearing of young, etc. Wetlands that exhibit high rates of plant ' productivity typically support food webs both within and outside of the wetland. For example, animals eat plant material produced in wetlands during the growing season. In fall and winter, the plant material breaks down into smaller particles and is transported into ' nearby waters providing additional biological support to plants and animals outside of the wetland. A high rating for the biological support function indicates that the wetland provides, or has the capacity to provide, significant biological support to wildlife. Water Quality: Nutrient and Sediment Trapping ' Pollutants washed by rainfall from urban and agricultural lands are carried over land to water bodies. Pollutants include soil particulate matter,fertilizers,pesticides, and grease and oil. Wetlands can improve water quality by trapping and removing nutrients and pollutants ' from surface waters, and by chemical detoxification. Surface runoff flowing through a wetland is slowed by wetland vegetation. When water velocity is reduced, sediment drops out of the water, and roots of wetland plants bind accumulated sediments. Nutrients,usually in the form of nitrogen and phosphorus that enter wetlands accumulate within wetland soils. Microorganisms in wetland soils then convert these nutrients into less harmful forms that are taken up by wetland plants and converted to plant material. A high rating for water quality ' indicates that the wetland provides, or is capable of providing, significant water quality functions. ' Flood and Storm Water Desynchronization In severe storms, the amount of rainfall runoff increases, and flooding may result. Some wetlands have the capacity to accept and store floodwaters. After the flooding, the rate that water re-enters stream channels can reduce downstream flooding and erosion. A high rating for flood and storm water desynchronization indicates that a wetland provides, or is capable ' of providing, significant floodwater attention. ' Groundwater Exchange In many instances groundwater is used for public or private water supply. Some wetlands ' temporarily store water that moves through underlying soil or between soil layers and enters the local groundwater system. Movement of water into the groundwater system is called groundwater recharge. A high rating for groundwater exchange indicates that a wetland ' provides, or is capable of providing,significant groundwater exchange. Support of Base Flow Many wetlands store water during storm or flooding events then release water into surrounding surface waters to augment summer and/or winter base flows in the adjacent City of Renton-FINAL DRAFT 24 55-1779-07 ' January 1995 surface water. A high rating for support of base flow indicates that the wetland does, or is capable of,augmenting base flow. ' Cultural Values ' Many wetlands provide socioeconomic, cultural or aesthetic values. Socioeconomic values, such as supporting commercial fisheries, can be significant. Cultural considerations including recreation, are also important because they represent social perceptions based on an intrinsic appreciation for the natural environment. A high rating for cultural values indicates that the wetland does,or is capable of,providing opportunities for cultural values. ' Shoreline Stabilization Vegetated wetlands along shorelines can protect against shoreline erosion caused by river currents during floods. Wetland vegetation absorbs the energy of the surface water and dampens wave action. A high rating for shoreline stabilization indicates that the wetland does,or is capable of, stabilizing shorelines. ' 5.3 CREDITS ' Credits would be measured in units of both acreage and function. The proposed distribution of credits based on acres and function is presented below. ' 5.3.1 Acre Credits Each acre of created wetland represents one credit. For example, 7.24 acres of created ' wetland on Mitigation Banking Site 2 represents 7.24 acre credits. 5.3.2 Functional Credits The results of the functional evaluation under proposed conditions for Mitigation Banking Site 2 indicates that, with the exception of the shoreline stabilization function, the value of ' all proposed functions would be high. Assigning numerical values to the functions and the low,medium, and high functional values defines the credits available. For example, if all of the targeted functions(e.g.,biological support,water quality improvements, flood and storm ' water attenuation) are achieved and receive a high value rating, 1,000 credits would be assigned to each function. Thus, a total of 7,000 functional credits would potentially be ' available at Mitigation Banking Site 2 (seven functions each assigned 1,000 credit points). 5.4 DEBITS ' Debits are what is withdrawn and subtracted from the available credits. As with credits, the proposed debits are based on acre and function. 5.4.1 Acre Debit City of Renton -FINAL DRAFT 25 55-1779-07 January 1995 ' The City of Renton's Wetland Ordinance established acreage replacement ratios. The ratio required depends on the type (i.e. emergent, scrub-shrub, forested) of wetland impacted. ' These ratios can be adjusted up or down under certain conditions. For example, if 0.5 acres of emergent wetland were impacted, the city would require 0.625 acre be replaced (1.25:1 ratio). As proposed, any required mitigation replacement ratios would be applied to acres that are debited from the bank. 5.4.2 Functional Debits ' The results of the functional evaluation assign a low,medium, or high rating to the value of the function provided by the wetland. The low, medium, and high ratings are assigned ' numerical values. Thus, the numerical value of 1,000 would represent high value, 500 would represent medium value, and 100 would represent low value. An example, of how the credit and debit system would work, is presented below. The total credit acres available ' on Mitigation Banking Site 2 is 7.24 acres and the total functional credits are 7,000 (1,000 credits per function). ' A proposed project will impact 0.50 acres of emergent wetland. The results of the functional evaluation on the wetland to be impacted indicates the existing wetland provides only two functions, and has a low value for providing biological support and flood and ' storm water attenuation. Using the proposed credit and debit system, a total of 0.625 acres would be subtracted from the 7.24 acres of acre credits, leaving 6.62 acres of acre credits for another project. ' The value of the functions to be affected was rated as low for biological support and flood and low for storm water attenuation. Thus, a total of 100 functional debits would need to be subtracted from the 1,000 functional credits available for both the biological support and flood and storm water control functions. Therefore, 900 functional credits would be remaining for biological support and flood and storm water attenuation respectively, and a ' total of 6,800 function credits would be available for another development project. 1 City of Renton -FINAL DRAFT 26 55-1779-07 ' January 1995 ' 6. FEE STRUCTURE The proposed fee structure for implementing the mitigation banking program and plan is ' based primarily on cost per acre. Detailed and final cost estimates to implement the mitigation banking program and plan, including permitting associated with developing the mitigation banking sites, administration of the mitigation banking program, site development, and monitoring and maintenance, are not complete. However, preliminary costs are estimated in Table 3. These costs will be refined when final site plans are developed, using information from the City of Renton and state and federal resource ' agencies. Table 3. Components of wetland mitigation banking program and plan and estimated costs. Cost ' Final construction drawings and specifications $60,000.00 Obtaining permits to develop sites $50,000.00 Mitigation Bank Program Administration $40,000.00 (1 FTE and/or contract with consultant)for one year Site Development Site 1 Grading and clearing $150,000.00 Construction supervision $20,000.00 Plant material and planting $15,000.00 Site 2 Grading and clearing $200,000.00 Construction supervision $20,000.00 Hydraulic changes $20,000.00 Plant material and planting 15,000.00 Monitoring(per year) $10,000.00 Maintenance(per year) $20,000.00 ' Contingencies(per year) $25,000.00 $645000.00 i City of Renton-FINAL DRAFT 27 55-1779-07 January 1995 ' The preliminary estimate indicates that the cost to construct a wetland mitigation bank on Site 1 (12.19 acres) and Site 2 (13.93 acres) is approximately $645,000.00. By dividing the total estimated cost by the acreage to be established (26.12), the cost per acre to construct ' the wetland mitigation banking sites is about $24,693.72. However, of the 13.93 acres to be constructed on Mitigation Banking Site 2, only 7.24 are currently available for private and ' public use.' Therefore, the City will most likely fund the establishment of the remaining 6.69 acres. Therefore, a total of 19.43 acres will be available for wetland mitigation on both mitigation banking sites. ' A steady local revenue source is needed for ongoing program and mitigation plan management, including annual costs associated with program administration, monitoring, and maintenance. For example, administration of the banking program requires commitment of at least one full-time city staff person. The cost to administer the bank for ten years is currently estimated to be $400,000.00. Monitoring will also be required for at ' least ten years; at an average cost of$10,000.00 per year, monitoring costs are estimated to be $100,000.00. Similarly, based on a ten-year period, funds for annual maintenance and to implement contingency actions are estimated to be $200,000.00 and $250,000.00, ' respectively. These annual costs over ten years total $950,000.00, or$95,000.00 per year. The costs to implement the mitigation banking program and plan will be shared by users of ' the banking sites. For example, local costs to mitigate impacts to wetlands from public projects will be paid by the City. Private developers will pay for mitigation associated with private projects. ' Although the "guessestimated" fee of$24,693.72 per acre may appear high, costs associated with doing individual mitigation projects can be as high or even higher. Factors that ' increase costs for individual mitigation projects include permitting costs, consultant fees, property acquisition,years of monitoring,maintenance and contingency costs, and bonding. The City of Renton will apply this estimated cost per acre of created wetland to the existing fee structure for obtaining permits fee structure, to cover the costs associated with implementing the mitigation banking program and plan. As the mitigation banking sites are ' established in advance of anticipated need for mitigation, the benefits (i.e. acreage, and new or increased functions) from this action are the credit. These credits will be tracked in a mitigation bank account from which withdrawals can be made. The proposed mitigation plan(see Part II)includes recreating wetlands on the entire site. Thus, 6.69 acres of existing wetland would be impacted. Preliminary conversations with state and federal ' resource agencies indicate that currently no mitigation banking credit would be allowed for the impacted wetlands. City of Renton -FINAL DRAFT 28 55-1779-07 January 1995 7. ADMINISTRATION OF MITIGATION BANKING PROGRAM ' The City of Renton Public Works Department will manage the wetland mitigation banking program and assume the overall responsibility for administering and monitoring the Wetland Mitigation Banking Program. Other City departments will provide assistance. Through staffing or contractual arrangements the City will gain the expertise to manage the wetland banking program for the life of the mitigation bank. There are also opportunities to work with state agencies, tribal entities, environmental and community organizations, non- profit environmental groups, and the private sector to create and protect the wetland mitigation banking sites, and to assist with monitoring and maintenance. These types of ' coordinated efforts can help reduce the costs of implementing and managing the mitigation banking program and plan. The responsibilities associated with administration of the mitigation banking program include: ' Day-to-day management of the bank sites Ensuring long-term integrity of the bank sites Monitoring and maintenance ' Issuing local permits to allow wetland alterations for which compensation will be made with the mitigation banking program Issuing credits and debits 1 City of Renton-FINAL DRAFT 29 55-1779-07 January 1995