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HomeMy WebLinkAbout03203 - Technical Information Report . 3Za3 CIVIL ENGINEERING LAND SURVEYING PROJECT MANAGEMENT STORMWATER MANAGEMENT TRANSPORTATION LAND PLANNING LANDSCAPE ARCHITEC7URE Y , 1 � • � 0 :� � �- I I I WAT E R B U RY SHORT PLAT Technical Information Report August 17, 2004 Revised October 11, 2004 � Prepared for The Pointe at Talbot Hill H.O.A. 7947 159th Place, Suite 102 Redmond, WA 98052 Submitted by ESM Consulting Engineers, LLC 11714 North Creek Parkway North Bothell, WA 98011 425.415.6144 tel 425.415.0924 fax . _, R�t C c i `�f �: J 0�� � 240� www.esmcivil.com CUS►0lVI��SER y':�'�' , _ WATERBURY SHORT PLAT Technical Information Report Prepared for The Pointe at Talbot Hill H.O.A. - I 7947 159th Place, Suite 102 Redmond, WA 98052 Submitted by ESM Consulting Engineers, LLC 11714 North Creek Parkway North Bothell, WA 98011 Job No: 994-005-004 August 17, 2004 Revised October 11, 2004 ���� G. CU�� Prepared by: QD �p Robert Ludwig, P.E. _'� � � � .p 40847 q Reviewed by: °�, BoIST84� �' Kristal O'Neil, P.E. ��jONAL� �e/" �1RES 1 !27/� ESM Job#:994-00�-004 Waterbury Short Plat TABLE OF CONTENTS Section Page # 1.0 PROJECT OVERVIEW............................................................................................... 1 1.1 Existing Conditions:.................................................................................................. 1 1.3 Developed Conditions:.............................................................................................. 2 Figure1.0—Vicinity Map............................................................................................... 3 Figure1.1 —Location Map.............................................................................................. 4 Figure 1.2—Existing Conditions Map............................................................................ 5 Figure 1.3 —Developed Conditions Map........................................................................ 6 2.0 CONDITIONS AND REQUIREMENTS SLJMMARY............................................... 7 Environmental Review Committee(ERC)Mitigation Measures:.............................. 7 King County Surface Water Design Manual Core and Special Requirements:.......... 7 3.0 FLOW CONTROL ANALYSIS AND DESIGN....................................................... 10 APPENDICES I A—Flow Control from the Sunnybrook TIR dated June 6, 2003 B — Supporting Calculations King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND � Part 2 PROJECT LOCATION AND PROJECT ENGINEER � DESCRIPTION � Project Owner: The Pointe at Talbot Hill Project Name: Waterburv Short Plat H.O.A. Location: Address: 7947 159`h PI. Suite 102 Township: 23 North Redmond,WA 98052 Phone: �425)869-1300 Range: 5 E of W.M. Project Engineer: Rav Miller, P.E. SW 1/4 Section: 29 Company: ESM Consultinq Enqineers LLC Phone/Address: (425)415-6144 . 11714 North Creek Pkwy N. Bothell.WA 98011 Part 3 TYPE OF PERMIT �; Part 4 OTHER REVIEWS AND PERMITS ' APPLICATION ; ❑ Subdivision ❑ DFW HPA ❑ Shoreline Management � Short Subdivision ❑ COE 404 � Rockery ❑ Grading ❑ DOE Dam Safety ❑ Structural Vaults ❑ Commercial ❑ FEMA Floodplain ❑ Other: � ❑ Other: ❑ COE Wetlands LPart 5 SlTE COMMUNITY AND DRAINAGE BASIN , Community: � Soos Creek Drainage Basin: Black River Water Shed: Duwamish-Green River Part 6 SITE CHARACTERISTICS , -- - ❑ River: ❑ Floodplain: ❑ Stream: ❑ Wetlands: ❑ Critical Stream Reach: ❑ Seeps/Springs: ❑ Depressions/Swales: ❑ High Groundwater Table: ❑ Lake: ❑ Groundwater Recharge: ❑ Steep Slopes: ❑ Other: � Part 7 SOILS r----- Soil Type Slopes Erosion Potential Erosive Velocities AqC 6 to 15% Moderate Slow to medium ❑Additional Sheets Attached Part 8 DEVEI.OPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT ' ❑ ❑ ❑ ❑ ❑ ❑ ❑Additional Sheets Attached % Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION ❑ Sedimentation Facilities � Stabilize Exposed Surface ❑ Stabilized Construction Entrance ❑ Remove and Restore Temporary ESC Facilities � Perimeter Runoff Control � Clean and Remove All Silt and Debris ❑ Clearing and Grading Restrictions ❑ Ensure Operation of Permanent Facilities � Cover Practices ❑ Flag Limits of SAO and open space ❑ Construction Sequence preservation areas ❑ Other ❑ Other � I I, . , � � Part 10 SURFACE WATER SYSTEM ❑ Grass Lined ❑ Tank ❑ Infiltration Method of Analysis Channel ❑Vault ❑ Depression 1998 KCSWDM ❑ Pipe System ❑ Energy Dissipater ❑ Flow Dispersal ❑ Open Channel Compensation/ ❑Wetland ❑Waiver Mitigation of ❑ Dry Pond � Stream Eliminated Site ❑ Regional Detention Storage ❑Wet Pond Brief Description of System Operation: House downspout lines will be connected into an existinq catch basin with a 6"diameterpipe. Driveway will run back into the street and runoff flows will enter the same existinq catch basin. Imqervious area added is to be less than 5,000 square feet. Facility Related Site Limitations Reference Facility Limitation ' Part 11 STRUCTURAL ANALYSlS � Part 12 EASEMENTS/TRACTS ❑ Cast in Place Vault ❑ Drainage Easement ❑ Retaining Wall ❑ Access Easement � Rockery> 4' High ❑ Native Growth Protection Easement ❑ Structural on Steep Slope � Tract ❑ Other ❑ Other � Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision my supervision have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. � `K/f> � Signed/Date E � I �.. � I ESM Job#:994-005-004 Waterburv Short Plat 1 .0 PROJECT OVERVIEW The proposed Waterbury Short Plat area, Parcel "A", was previously developed as part of the Plat of Sunnybrook within the last two years. Pazcel "A" was originally thought to be in a coal mine hazard area and was deemed as a non-buildable area. Due to the previous development and more research, the area has been determined to not reside in a coal mine hazard area. Therefore, it is proposed that the Parcel "A" be subdivided up into another single family lot and the remaining area be placed into a Tract "A" area. The proposal is to subdivide the Parcel "A" area (0.43 acres) into a single family lot (0.16 acres) and a Tract "A" area (0.27 acres). The site is located along the northerly edge of the intersection of South 36`� Place and Southeast 174`� Street in the City of Renton, Washington (see Figure 1.0 — Vicinity Map and Figure 1.1 — Location Map). More generally, the site is located within Section 30,Township 23 North, and Range 5 East of the Willamette Meridian. 1.1 Existing Conditions: The existing site topography slopes from east to west at grades of approximately 33%. Due to grading from the previous development, vegetative cover consists mostly of grasses (see Figure 1.2—Existing Conditions Map). Property adjacent to the proposed short plat is as follows. • To the east is a 30 foot power and access easement that originates at South 36th Place and continues to the north. Easterly of this easement is an existing condominiums complex. 5tormwater runoff from the condominium complex is collected and conveyed southerly to Southeast 174th Street. The storm drainage system for Southeast 174`�' Street conveys the stormwater around the site. • To the north is a single family residential development that is currently being developed. Stormwater runoff from the development is being collected and conveyed past the site to a detention facility to the northwest. • To the west is single family lot number 105 of the Plat of Sunnybrook development. There is a rockery separating the higher grade of this site and the lower grade of the lot. This rockery may have a drain that conveys collected stormwater runoff to the storm drainage system in South 36`�' Place. • To the south are South 36`t' Place and the intersection of South 36th Place and Southeast 174�' Street. Stormwater runoff from the site flows into the storm drainage collection system of South 36ch Place via two to three paths. The southerly section of the site sheet flows directly to South 36`� Place. The remainder of the site sheet flows westerly to either be collected by an assumed rockery drain, which would convey runoff to the drainage system in South 36`� Place; or flows over the rockery where the adjacent lot is graded to direct runoffto South 36`h Place. Stormwater runoff entering the South 36`h Place drainage system is conveyed via a closed pipe drainage system to a detention facility located in the northwesterly corner of the Plat of Sunnybrook. � ESM Job#:994-005-004 Waterburv Short Plat 1.3 Developed Conditions: The westerly section of the site (0.16 acres) is to be graded and made into a lot for a single family house with associated utilities (see Figure 1.3 — Developed Conditions Map). A rockery will be potentially placed along the northerly side of the new lot, which may be graded out to match the lower grades of the development to the north. The remainder of the azea to the east (0.27 acres) is to be designated as a new Tract "A" azea. This new Tract "A" azea is to be graded and re-hydroseeded. The driveway and utilities for the new lot will come off of South 36�' Place. Sewer is to be stubbed out to the new lot line and a water meter is to be placed next to the property line. Stormwater runoff from the proposed short plat will either flow directly into South 39`� Place, as it currently does; or continue to flow toward the existing rockery along the westerly property line. Stormwater runoff from the proposed house will be collected by a closed pipe conveyance system, which will be connected to an existing catch basin in South 36`� Place. The maximum impervious area for the new lot is to be 5,000 squaze feet. � . � . . � ' 2 Vicinity Map _ _��.,.� �� ��,���. � n 405: _� � ,� : v` � 1 '^j � � �x'� s �erH sr ��,��' ,,, ,� s � � �B SE 16 PL. tl=�, � S 17TM � TS'� J�` ..�3�' . � S 18TH i. G � � C tn y_�5._1_9tM Si. W p� < ` h 15 �' n��.r � Rauwc r+w�s n ��� DR, +,,..3 (7 j �SW Z��T ST. . � � �.ht.,m. L.,..e. � � .�.:�,�.__.,�._23RD_ST.,._�.,. .� o� ' � � W � y v 5 T �ST. 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WA 980�� fE�ERAL w�Y (253)638-6113 BpTMELL (�35)a13-61�a www.esmcivil.com CLE ELUu (sos> 67�-1905 ����� Engineerinq Lond S�ryaY;�a �a�d Plonninq DEVELOPED CONDITIONS MAP Public Worka I Project Munoqement I Londscope Architecturs �oB NO. G9�-001-00� �„TE: FlGURE 1.3 ORnwN: rttt SHEEi i OF i ESM Job#:994-0OS-004 Waterburv Short Plat I 2.0 CONDITIONS AND REQUIREMENTS SUMMARY Environmental Review Committee (ERC) Mitigation Measures: The Environmental Review Committee of the City of Renton made a Determination of Non- Significance-Mitigated for the Waterbury Short Plat. Below are the mitigation measures from the ERC review. 1. The applicant shall install and maintain temporary erosion control measures subject to the 2001 Department of Ecology's Erosion Control Manual. The satisfaction of this condition shall be subject to the review and approval of the Development Services Division for the duration of the project. 2. The applicant shall comply with the recommendations contained vvithin the Coal 'I Mine Assessment prepared by Icicle Creek Engineers for the Sunnybrook Plat July 31, 2001 except where superseded by the amended Coal Mine Hazard Evaluation conducted by Icicle Creek Engineers, August 9, 2004. 3. The applicant shall place a note on the face of the plat, as well as record a restrictive covenant, which states the following:. COAL M1NE HAZARD NOTICE. The lot created herein may fall within a coalmine hazard area as identified by a Geotechnical Engineer at the time of this subdivision. Presence of such a hazard may trigger mitigation measures at the time of construction. The satisfaction of this requirement shall be subject to the review and approval of the City Attorney and the Property Services Section prior to the recording of the plat. 4. The applicant shall comply with the recommendations contained within the Geotechnical Report prepared by Cornerstone Geotechnical, Inc. dated April 11, 2001 for Sunnybrook plat with regards to site preparation, grading, structural fill, foundations, and drainage. The satisfaction of this requirement shall be subject to the review and approval of the Development Services Division prior to the issuance of building and construction permits for the project. King County Surface Water Design Manual Core and Special Requirements: The City of Renton Code, Chapter 6, Section 4-6-030-E, requires all projects to supply a drainage plan for surface water that flows through and from the proposed site. This plan and corresponding report is to be prepared in conformance to Sections 1.2, 1.3, 3, and 4 of the 1990 King County Surface Water Design Manual (KCSWDM). However, the Plat of Sunn brook was desi ed to meet the 1998 KCSWDM. Therefore this ro'ect is anal ed Y � , P J Yz using the 1998 KCSWDM requirements. >:__I � ESM Job#:994-005-004 Waterburv Short Plat Core Requirements: 1. Discharge at the Natural Location: Stormwater runoff is to be released to the storm drainage conveyance system in South 36�' Place similar to the existing conditions. �,/� _� 2. Offsite Anal� An Offsite Analysis was performed by ESM Consulting Engineers, L.L.C. for the Plat of Sunnybrook. This analysis is found in the Technical Information Report for Sunnybrook, dated June 6, 2003. Since the short plat is in the Sunnybrook development, an offsite analysis will not be performed. 3. Flow Control: Flow control for the Plat of Sunnybrook was designed based on � Level 2 flow control requirement. However, the short plat is proposing a maximum of 5,000 square feet of impervious area. Per Section 1.2.3 of the KCSWDM, this meets the Impervious Surface Exemption. Please see Section 3 -Flow Control Design. 4. Conve_yance S sy tem: The only conveyance system will be for storm water coming from the downspouts of the proposed house. The system will be connected into an existing catch basin in South 36`}' Place. The remainder of the stormwater runoff will sheet flow from the site similar to the existing conditions. 5. Temporarv Erosion and Sediment Control: � Erosion and sediment control will be incorporated into the design plan drawings after preliminary review. Some of the measures to be incorporated are Clearing Limits, Perimeter Protection, and Cover Measures. 6. Maintenance and Operations: There is no drainage facilities required for this project. Therefore, a Maintenance and Operations Manual is not required and is not provided. 7. Financial Guarantees and Liability: A bond quantity worksheet will be provided after the first review. 8. Water Qualit� The project is proposing a maximum of 5,000 square feet of new impervious area. Per Section 1.2.8 of the KCSWDM, this meets the Surface Area Exemption. s ESM Job#:994-0OS-004 Waterburv Short Plat Special Requirements: 1. Other Adopted Area-Specific Requirements: The project is not located in a Critical Drainage Area (CDA), a Master Drainage Plan (MDP), a Basin Plan (BP), or a Lake Management Plan (LMP). Therefore, the project is not subjected to this requirement. 2. Floodplain/Floodway Delineation: The project site is not located within the 100 year floodplain or within a floodway. The project is not located in or adjacent to a lake, a wetland, or a closed depression. Therefore, the project is not subjected to this requirement. 3. Source Control: The project is a short plat subdivision and is not subjected to this requirement. 4. Oil Control: The project is not a high-use site development and is not subjected to this requirement. ^� j � . F- _ � 9 ESM Job#:994-005-004 Waterburv Short Plat 3.0 FLOW CONTROL ANALYSIS AND DESIGN The proposed project is analyzed using the 1998 King County Surface Water Design Manual (KCSWDl�. The proposed short plat will create a maximum impervious area of 5,000 square feet. Per Section 1.2.3 of the KCSWDM, flow control is not required if the new impervious area is less than 5,000 square feet. The project area is currently vegetated as grass and the maximum stormwater runoff flow change from that of the existing condition to that of the developed condition is 0.03cfs for the 100-year storm event. This is a negligible amount of , flow (see Appendix "B"). Therefore, the conveyance system of South 36`h Place should be able to convey the additional flow. The downstream detention pond facility for Basin B of the Plat of Sunnybrook was analyzed using King County Runoff time Series (KCRTS) to find impacts due to the additional maximum impervious area of 5,000 square feet. This was done by using the original design information (see Appendix "A") and moving 5,000 square feet of area from the grass category to the impervious category for only the developed condition. After running the new developed basin through the detention pond and comparing it to the original design,based on a Level 2 analysis, it is found that the required storage volume of 173,320 cubic feet (see Appendix "B") has not changed (see Appendix "A"). Therefore, the detention pond should be able to handle the additional storm water runoff and still function as designed for the Plat of Sunnybrook. �o APPENDIX A Sections of � The Plat of Sunnybrook TIR Dated June 6, 2003 I� � K��� >� �HI-- � 4.3 Desiqn Standards for Flow Control and Water Quality As mentioned previously in this report,this project is vested under the 1990 King County Surface Water Design Manual with 1994 amendments,which is the adopted standard according to the City of Renton Development Regulations Manual. However, a pre-application response from the City's Department of Public Works has required that the site's runoff be controlled to the KCRTS Level Two standard as outlined in the 1998 edition of the King County Surface Water Design Manual. Water quality facilities have also been designed to the requirements outlined in the 1998 King County Surface Water Design manual, basic water quality menu. il .;�'-µ I � � 4 - 5 4.4 Flow Control System Detention calculations were performed using King County's KCRTS Level 2 methodology, which requires that developed outflows must match the existing outflows for all storm events, which generate flows greater than half of the 2-year storm event, and less than the 50-year storm event. The wetlands will be left undisturbed and runoff flows will bypass around the developed areas, so they are not included in the detention calculations. Per KCSWDM, developed lot impervious areas are calculated based on 4,000 square feet per lot or the maximum impervious area for each lot based on the zoning, whichever is smaller. The storm water calculations and all supporting documents are included in Appendix 4-A of this report. A summary of the calculated values follows: Existing Conditions: Basin A Total Area 2.15 Acres Basin A Land Cover Till Forest 1.53 Acres Till Pasture 0.00 Acres Wetlands 0.62 Acres Basin B Total Area 17.82 Acres Basin B Land Cover Till Forest 14.99 Acres Till Pasture 2.83 Acres Wetlands 0.00 Acres Basin B Flow Rates ( Yz)2-yr Peak 0.26 Acres I 50-yr Peak 1.40 Acres i Basin C Total Area 10.46 Acres Basin C Land Cover Till Forest 7.56 Acres Till Pasture 2.90 Acres Wetlands 0.00 Acres Basin C Flow Rates ( %z)2-yr Peak 0.16 Acres 50-yr Peak 0.85 Acres � `;. - ' � :-I;.� -�'., _ . . - . 4 - 6 Developed Conditions: Basin A Total Area 1.53 Acres Basin A Land Cover Till Forest 0.91 Acres Till Pasture 0.00 Acres Till Grass 0.00 Acres Wetlands 0.62 Acres Impervious 0.00 Acres Basin B Total Area 17.82 Acres Basin B Land Cover Till Forest 4.83 Acres Till Pasture 0.00 Acres Till Grass 4.65 Acres Wetlands 0.00 Acres Impervious 8.34 Acres � Basin C Total Area 10.46 Acres Basin C Land Cover Till Forest 1.52 Acres Till Pasture 0.00 Acres Till Grass 2.66 Acres Wetlands 0.00 Acres Impervious 6.28 Acres 4 - 7 4.5 Detention Facility Desiqn: Preliminary detention sizing was determined using KCRTS to the KCSWDM Level Two flow control standard. Sizing was performed as outlined in the KCSWDM, and in the KCRTS Users Manual, Section VI. It was determined that the developed flow rates for Basin 'A'were lower than the pre-developed rates, so no flow control was proposed for that basin. The proposed detention facility for Basin `B'will be a pond. The required live storage volume for the detention pond is determined to be 173,320 cubic feet. This sizing is based on a pond with 2:1 side slopes, 10 foot storage depth, and a dual orifice configuration. The proposed detention facility for Basin `C' is a vault. The required volume for the detention vault is 115,200 cubic feet. The live storage depth is assumed to be 12 feet, andthe outlet control structure is assumed to have a dual orifice configuration. All KCRTS detention sizing calculations are contained within Appendix 4-A. Detention Volume Summary Volume Required Volume Provided Basin B 173,320 C.F. 182,390 C.F. Detention Pond Basin C 115,200 C.F. 118,080 C.F. Detention Vault Safety Factor Basin B = 5.2% (182,390/ 173,320) Basin C =2.5% (118,080/ 115,200) Riser Pipe Sizinq See Figure 5.3.4H Riser Inflow Curves for details. Basin B, Q,00(Developed) =5.27 cfs Basin C, Q,00(Developed) =3.64 cfs 4 - 8 Emerqency SpiilwaV The emergency spillway was sized per KCSWDM Section 5.3.1.2. The required width was obtained from the following equation. L= Q10° —2.4*H or 6 feet minimum 3 3.21*HZ Where: Q,�=peak 100 year flow(cfs)= 5.27 cfs H = height of water over weir(ft)=0.5 ft ' L = length of weir(ft) 5.27 L = 3 —2.4*0.5 =3.4ft �6ft 3.21*0.52 Therefore, L=6 feet. 4 - 9 Basin `B' Detention Facility Desiqn: Basin `B' Pre-Developed Conditions: Total Area = 17.82 Ac. Till Forest Area= 14.99 Ac. Till Pasture Area= 2.83 Ac. Till Grass Area = 0.00 Ac. Outwash Forest Area 0.00 Ac. Outwash Pasture Area 0.00 Ac. Outwash Grass Area 0.00 Ac. Wetland Area = 0.00 Ac. Impervious Area= 0.00 Ac. Scale Factor= 1.0 Basin `B' Pre-developed Flow Frequencies Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates-— ----Flow Frequency i�.-ialysis Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 1.15 2 2/09/O1 18:OD 1.53 1 100.00 0.990 0.320 7 1/06/02 3:00 1.15 2 25.00 0.960 0.883 4 2/28/03 3:00 0.888 3 10.00 �.900 0.040 8 3/24/04 19_00 0.883 4 5.00 0.800 0.518 6 1/O5/OS 8:00 0.776 5 3.00 0.667 0.888 3 1/18/06 20:00 0.518 6 2.00 0.500 0.776 5 11/24/06 4:00 0.320 7 1.30 0.231 1.53 1 1/09/08 9:00 0.040 8 1.10 0.091 Computed Peaks 1.40 50.00 0.980 ��. �� r ,':i Basin `B' Developed Conditions: Total Basin Area = 17.82 Ac. Total Lot Area = 8.58 Ac. Impervious = (65% ) 5.58 Ac. Pervious = (35°/a) 3.00 Ac. Impervious Road Area = 2.20 Ac. Other Impervious Area= 0.56 Ac. Till Forest Area= 4.83 Ac. Till Pasture Area = 0.00 Ac. Till Grass Area = 4.65 Ac. Outwash Forest= 0.00 Ac. Outwash Pasture= 0.00 Ac. Outwash Grass = 0.00 Ac. Wetland Area = 0.00 Ac. Impervious Area= 8.34 Ac. Scale Factor= 1.0 Basin `B' Developed Flow Frequencies Flow Frequency Analysis Tirne Series File:dev3.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 2.63 5 2/09/O1 2:00 5.27 1 100.00 0.990 2.07 8 1/OS/02 16:00 3.15 2 25.00 0.960 3.12 3 2/27/03 7:00 3.12 3 10.00 0.900 2.16 7 8/26/04 2:00 2.80 4 5.00 0.800 2.61 6 10/28/04 16:00 2.63 5 3.00 0.667 2.80 4 1/18/06 16:00 2.61 6 2.OU 0.500 3.15 2 10/26/06 0:00 2.16 7 1.30 0.231 5.27 1 1/09/OB 6:00 2.07 8 1.10 0.091 Computed Peaks 4.56 50.00 0.980 ' ri SITE CHARACTERlSTICS BASIN 'A': (UNDEVELOPED BASIN) WETLAND AREA = 0.62 AC. �"' FOREST AREA = 0.91 AC. (� BASIN TOTAL = 1 .53 AC. O 2 N 8520't9' W 396.57' � - — - ��'` . BASIN 'B': O � � �� - =z DEVELOPED IMPERVIOUS AREA � � I � _ � - � BASIN �A' IMPERVIOUS ROADWAY AREA = 2.20 AC. 0 � � ' � 1.53 AC. o' 2oa' IMPERVIOUS LOT AREA = 5.58 AC. Y � t [ � r�' -: W � �� IMPERVIOUS PONU AREA = 0.56 AC. � _ ` � �- �' � afk�fLE � ` � SUBTOTAL = 8.34 AC. � W ; — �r �� _: �, � � ��I!(i�',r -:-�.�.-_.. . � g�» aB, � � � _ ,,I��;\\, �-:���_..-: � DEVELOPED PERVIOUS AREA � � �1,:, �: ::.. LANDSCAP AREA - 4.65 AC. Z � N BTaS'2g' E 1290.02' — � S 1� �'' �'� �\ ; � �.�,��,,� � �---� - -� 1`1,3 FOREST AREA (UP�DISTURBED) = 4.83 AC. Z '-�' �K � ;j��l�� .�'� �4 - " t�— a� ��-�''."��- -�!--�--' S4 � ;�� ',�z �� ';,,,a °s } � ? SUBTOTAL = 9.48 AC. -G (� ��� �,�; y =a � �-�. � �-�1'���t�!i �Y �� ` 1 � �5 �=7 w9 � � � � � �j�� � € � � � � ��� _ �u'���' `���� ���' � -�`�`h' i !�1 \ ��lli��{ i� }. �p II�II��� � � '\ , �� ` ,� � \ �` �\`�� N — _� I � , i'I ���� . � � ' "�"' � . ' t gE�\� � . �. ;: � . � : � �`��i � DEVELOPED TOTAL 17.82 AC. � � � � ` t �`� �� ` `� � ;�� � ' �2 �°� � � �` ` � `� '� UNDEVELOPED AREA O r � , ry 1 � � a�z . a{ y�; ,y �S ,m � 1V � t�� , ,e� ,� „ ,s,2 ,,�3 , '� • a f � � ,�`�l � � �`- ` ,��,' 1� � � 1 °`C ;' � �� tg �m °° ;�i - .�;`,�` � WETLAND = 2.99 AC. J m —i i � � � -� � y �` �' � ."�� t / � :-�.....'. � � 77 b i f r t�5 �r� � W � �f 55 1 � •.•.•.��� � /f � A : � ` � //�������i� �ft. �� � � -� i I— W ' �.�1� � / ` l ` � � � %5 f� � BASIN TOTAL = 20.81 AC. � o � � � � � . , \ �� � '7 � 6A �0 ,m;, :Z :n � ��.� f� , /� ��tr'{1����//! ��-/ � � � � g, �9 �b ( 1 � ..� o _ —� �,—%� Z � 1f(� 54 �l -_� j�' � � � j ,_��1��\\\������,�����i``���\ tJ 't / Q �.. �3.3TTH ST. � � l 6 � - - # .�=-� ----=� -� ,�.;��\ �• �``�`-.�� �{ t ��ti •�j BASIN �C�. a3. :SI£7�-' ,e��� } �. - _- � � ��`—__ �_-.__ l��Fi �����\;.,��_, J,� ♦ '� � ;- � ,�-� �--_�: :_.:=_ �;.-:�: _:-_\���_i����-- — _ :�:� _:j!);;;-�; `��.` ��'�� �� DEVELOPED IMPERVIOUS AREA o I ; � �� .. � � ': . ��-:�- l,�;,��`�`, ti,�ti�,�1�,\� /� � iMPERV10US ROAGWAY AREA = 1 .94 AC. � ' � ,�-�,� � �. � �� o.�•�:, BASIN__B _ :. ;-,. __�>�_ ��,�` `:�����,,4�,, ; o 3 _ __ _ _- _ _- .�:::::_ :.::_��`i�����ll� IMPERVIOUS LOT AREA = 4.34 AC. � `� � .�1�� � '�sz � �!� - ��.81 /��i. -- _- ���:�_=:�:�. .-. � ?,���!'�f � SUBTOTAL = 6.28 AC. T � � i�` I � �� - ������-�:�:-� - - _ : - _- - i �1,��� ° � I � a �;Z '` - ��:i-- -_ =-- -- "" � ��� - �,�,����� � o f t j--- — �� .,R � -i •F' , � _ � �. l �:'. :.:..:: :.:. .: :.: :``:=`-_`�... �: �;,,, ;, DEVELOPED PERVIOUS AREA v i" { t g �S - "J6 107 iS�3 !0�9 . .'. . .'. . --- - -� ��;�i� !n t _ . . '- -- - �'}'"�� ��• C. _ , � \""�, ;� ,; - " �` ' �` . - - __ ---- �,.;:r,{{,� R e LANDSCAP AR A = 2.66 A _ ��:-:=:-. ��:-:=: .=:=_�::.�.;�.;�::==_ � h E �: � .� i-.•.�.-_ .• �fi;�� }� '- _ == � � � 1 j�.� �` � ,_�. { �} ,-=' _ - ; !��; = FOREST AREA (UNDISTURBED) - 1.52 AC. ,;^ � ! ( rj�, ��, � � �'�� � � . ( j . . . ...... .. . .�=' k-aros•,s e �e..zr � � SUBTOTAL = 4.18 AC. J� - a � � a � �a���� . , �. _ Q ry�n P� � DEVELOPED TOTAL = 10.46 AC. ¢ � > ��o � �.H � ` F �� a�; 4�` �` �, t �� �� �.:;�---�2.10 AC. � � — �a iwGt k ,) � 1 .� 1 1 a � � � o 00 �� . � �� , � ( -�_____ .-. .-.-.�.�_-. .-.-.�.-.�. � i � UNDEVELOPED AREA � �=W << � �, �. 1 � ! �.:::::::.:::. :::::: : : ( m m s� �" `; � 4 i, � -�' i�°jil. �� �„ �, ss �' �3 ��; ` ; s, b .� � :� - - -- / J WETLAND = 1 .64 AC. -— � � �,. � � �;�.�� � , � � � - - - ; � � - ��� � � BASIN TOTAL = 12.10 AC. W '' � _ 1 - � � � 1 3 ��y� � � a � � 4 r � S t ! t' ' '.� 3 c �. � / i n• � � � � t t ! � � : o�o o I � / t � i[�- , � � � \ 1 . ;I� a � �o " � h_ '��1' �3 e4� 'S 5 � '� e��r°, � ca� a�i nb 24 Iz'�5 `26 .Z�e� .__ �- _' ��- r� �_ ___ ---- � Y � � i� � w ��I � � _� Z � ��r . ;�s 1 j ; ` -- a, —� O � � � r � � { P� 1 � U � O �� o v=i j � � " " � LEGEND 3 � � � � _ - oe �� � - N 8650'2 �-86' Z Z�- > �a` m N BY03't W 339.93' �o_� • o -- � �'� DRAINAGE BASIN BOUNDARY o �u3im° E — � � � �, V W � P � 3 o n � � o s Vf �O % FIGURE 4 B ; ;D z ; rc u a' o � o � o � Basin `B' Required Detention Facility Calculations Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 2.00 H:1V Pond Bottom Length: 155.73 ft Pond Bottom Width: 77.87 ft Pond Bottom Area: 12127. sq. ft Top Area at 1 ft. FB: 24341. sq. ft 0.559 acres Effective Storage Depth: 10.00 ft Stage 0 Elevation: 141.50 ft Storage Volume: 173320. cu. ft 3.979 ac-ft Riser Aead: 10.00 ft Riser Diameter: 18.00 inches Caumber of orifices: 2 Full Head Pipe Crifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 2.00 0.343 2 5.20 3.40 0.687 6.0 Top Notch Weir: None Cutflow Rating Curve: None Facility `B' Staqe-Storaqe-Discharge Preformance Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 141.50 0. 0.000 0.000 0.00 12127. 0.02 141.52 . 243. 0.006 0.016 0.00 12145. 0.04 141.54 486. 0.011 0.022 0.00 12164. 0.06 141.56 729. 0.017 0.027 0.00 12183. 0.08 141.58 973. 0.022 0.031 0.00 12202. 0.10 141.60 1217. 0.028 0.035 0.00 12220. 0.13 141.63 1584. 0.036 0.036 0.00 12248. 0.15 241.65 1830. 0.042 0.041 0.00 12267. 0.17 141.67 2075. 0.048 0.044 0.00 12286. 0.19 141.69 2321. 0.053 0.047 0.00 12305. 0.36 141.66 4426. 0.102 O.U65 0.00 12465. 0.53 142.03 6559. 0.151 0.079 0.00 12626. 0.70 142.20 8719. 0.200 0.091 0.00 12789. 0.87 142.37 10907. 0.250 0.101 0.00 12952. 1.03 142.53 12992. 0.298 0.110 0.00 13106. 1.20 142.70 15234. 0.350 0.119 0.00 13271. 1.37 142.87 17504. 0.402 0.127 0.00 13437. 1.54 143.04 19803. 0.455 0.135 0.00 13604. 1.71 143.21 22129. 0.508 0.142 0.00 13771. 1.88 143.38 24485. 0.562 0.149 0.00 13940. 2.05 143.55 26869. 0.617 0.155 0.00 14109. 2.22 143.72 29282. 0.672 0.162 0.00 14280. 2.39 143.89 31724. 0.728 0.168 0.00 14451. 2.56 144.06 34196. 0.785 0.174 0.00 14624. 2.73 144.23 36696. 0.842 0.179 0.00 19797. 2.90 144.40 39227. 0.901 0.185 0.00 14971. 3.07 144.57 41787. 0.959 0.190 0.00 15146. 3.24 144.74 44376. 1.019 0.195 0.00 15322. 3.41 144.91 46996. 1.079 0.200 0.00 15499. 3.58 145.08 49646. 1.140 Q.205 0.00 15677. 3.75 145.25 52326_ 1.201 0.210 0.00 15856. 3.92 145.42 55037. 1.263 0.215 0.00 16035. 4.09 145.59 57778. 1.326 0.219 0.00 16216. 4.26 145_76 60551. 1.390 0.224 0.00 16398. 4.42 145.92 63188. 1.451 0.228 0.00 16569. 4.59 146.09 66020. 1.516 0.233 0.00 16753. ' 4.76 146.26 68884. 1.581 0.237 0.00 15937. i 4.93 146.43 71779. 1.646 0.241 0.00 17122. 5.10 146.60 74706. 1.715 0.245 0.00 17308. 5.20 146.70 76442. 1.755 0.247 0.00 17418. 5.24 146_74 77139. 1.771 0.251 0.00 17462. 5.27 146.77 77664. 1.783 0.261 0.00 17495. 5.31 146.81 78365. 1.799 0.276 0.00 17590. 5.34 146.84 78891. 1.811 0.297 0.00 17573. 5.38 146.68 79595. 1.B27 0.322 0.00 17617. 5.41 146.91 80124. 1.839 0.351 0.00 17650. 5.45 146.95 80831. 1.656 0.386 0.00 17694. 5.48 146.98 81362. 1.868 0.421 0.00 17728. 5.52 147.02 82072. 1.884 0.432 0.00 17772. 5.69 147.19 85110. 1.954 0.478 0.00 17961. 5.86 147.36 88179. 2.024 0.517 0.00 18152. 6.03 147.53 91281. 2.096 0.552 0_00 18343. 6.20 147_70 94416. 2.167 0.583 0.00 18535. _ 6.37 147.87 97583. 2.240 0.612 0.00 18728. 6.54 148.04 100763. 2.314 0.640 0.00 18922. 6.71 148.21 104017. 2.388 0.666 0.00 19117. 6.87 148.37 107090. 2.458 0.690 0.00 19301. � 7.04 148.54 110388. 2.534 0.714 0.00 19498. 7.21 148.71 113719. 2.611 0.736 0.00 19695. 7.38 148.88 117085. 2.688 0.758 0.00 19894. 7.55 149.05 120483. 2.766 0.779 0.00 20093. 7.72 149.22 123916. 2.845 0.799 0.00 20294. 7.89 149.39 127383. 2.924 0.819 0.00 20495. 8.06 149.56 130885. 3.005 0.838 0.00 20697. 8.23 149.73 134421. 3.086 0.857 0.00 20901. 8_40 149.90 137991. 3.168 0.875 0.00 21105. 8.57 150.07 141596. 3.251 0.893 0.00 21310. � 8.74 150.24 145236. 3.334 0.911 0.00 21516. 8.91 150.41 148912. 3.419 0.926 0.00 21722. 9.08 150.58 152622. 3.504 0.944 0.00 21930. 9.25 150.75 156368. 3.590 0.961 0.00 22139. 9.42 150.92 160149. 3.677 0.977 0.00 22349. 9.59 151.09 163966. 3.764 0.993 0.00 22559. 9.76 151.26 167819. 3.853 1.010 0.00 22771. 9.93 151_43 171708. 3.942 1.020 0.00 22983. 10.00 151.50 173320. 3.979 1.030 0.00 23071. 10.10 151.60 175634. 4.032 1.500 0.00 23196. 10.20 151.70 177960. 4.085 2.350 0.00 23322. 10.30 151.80 180298. 4.139 3.460 0.00 23448. 10.40 151.90 182649. 4.193 4.760 0.00 23575. 10.50 152.00 185013. 4.247 6.240 0.00 23702. 10.60 152.10 187390. 4.302 7.670 0.00 23829. 10.70 152.20 189779. 4.357 8.210 0.00 23957. 10.80 152.30 192181. 4.412 8.710 0.00 29084. 10.90 152.40 194596. 4.467 9.180 0.00 24213. '�` 11.00 152.50 197024. 4.523 9.620 0.00 24341. 11.10 152.60 199464. 4.579 10.050 0.00 24470. 11.20 152.70 201918. 4.635 10.450 0.00 24599. 11.30 152.80 204384. 4.692 10.840 0.00 24728. 11.40 152.90 206863. 4.749 11.220 0.00 24858. 11.50 153.00 209356. 4.806 11.580 0.00 24988. 11.60 153.10 211861. 4.864 11.930 D.00 25119. 11.70 153.20 214379. 4.921 12.270 0.00 25249. 11.80 153.30 216911. 4.980 12.590 0.00 25380. 11.90 153.40 219455. 5.038 12.920 0.00 25512. Detention Facility Inflow Stage-Discharge Performance for Siqnificant Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (C�-Ft) (Ac-Ft) 1 5.27 1.53 1.01 9.77 151.27 167989. 3.856 2 2.63 ***'�*** 0.93 6.91 150.41 148990. 3.420 3 3.15 ******* 0.78 7.60 149.10 121512. 2.790 4 3.12 ***"*** 0.73 7.18 148.68 113107. 2.597 5 2.80 ******' 0.69 6.88 148.38 107329. 2.464 6 2.61 **t**** 0.46 5.62 147.12 83915. 1.926 7 2.07 **•;**� 0.24 4.66 146.36. 70623. 1.621 8 2.16 ******* 0.20 3.57 145.07 49459. 1.135 ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev3.tsf Outflow Time Series File:rdout Inflow/Outflow Analysis - Peak Inflow Discharge: 5.27 CFS at 6:00 on Jan 9 in Year 8 ' Peak Outflow Discharge: 1.01 CFS at 15:00 on Jan 9 in Year 8 Peak Reservoir Stage: 9.77 Ft Peak Reservoir Elev: 151.27 Ft Peak Rese r✓oir Storage: 167989. C�-Ft . 3.856 Ac-Ft Flow Duration Comparison z�uration Comparison Anaylsis Base File: predev.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New BChange Probability Base New �Change 0.260 � 0.91E-02 0.81E-02 -11.9 � 0_91E-02 0.260 0.247 -4.9 0.328 � 0.62E-02 0.62E-02 -1.0 I 0.62E-02 0.326 0.325 -0.9 0.397 � 0.49E-02 0.52E-02 7.0 I 0.49E-02 0.397 0.426 7.3 0_465 � 0.37E-02 0.39E-02 4.4 � 0.37E-02 0.465 0.485 4.4 0.533 � 0.28E-02 0.32H-02 12.1 � 0.28E-02 0.533 0.577 8.3 0.601 � 0.22E-02 0.25B-02 16.4 � 0.22E-02 0.601 0.640 6.4 0.669 � O.15H-02 0.18E-02 18.7 � 0.15E-02 0.669 0.684 2.2 0.738 � O.lOF3-02 0.91E-03 -11.1 � O.10E-02 0.738 0.725 -1.7 0.806 � 0.60E-03 0.57E-03 -5.4 I 0.60E-03 0.806 0.791 -1.9 0.874 � 0.36E-03 0.23E-03 -36.4 I 0.36Fs-03 0.874 0.844 -3.4 0.942 ( 0.21E-03 O.00E+00 -100.0 � 0.21E-03 0.942 0.887 -5.9 1.01 � 0.15E-03 O.00E+00 -100.0 I O.15fi-03 1.01 0.902 -10.8 1.08 � 0.82E-04 O.00E+00 -100.0 I 0.62E-04 1.06 0.919 -14.8 Maximum positive excursion = 0.049 cfs ( 9.1�) occurring at 0.539 cfs on the Base Data:predev.tsf and at 0.588 cfs on the New Data:rdout.tsf Maximum negative excursion = 0.216 cfs (-18.9�) occurring at 1.14 cfs on the Base Data:predev.tsf and at 0.928 cfs on the tJew Data:rdout.tsf Basin `B' Flow Duration Performance rdouLCur o terget dur ♦ N R ��0 ti �� �� � � m LL o U 0 rn `m � L U fn �p Q O y R �� 7 0 �� � 00 � N O � �b 1� 5 1� � 1� 3 1Q�� 1Q�� 1Q� Probability Exceedence APPENDIX B Supporting Calculations ���T o F sv�1�l ��l�c�r D�U��D�En S 1 T� ���5 Flow Frequency Analysis Time Series File:dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 2.63 5 2/09/O1 2:00 5.27 1 100.00 0.990 2.07 8 1/05/02 16:00 3.15 2 25.00 0.960 3.12 3 2/27/03 7:00 3.12 3 10.00 0.900 2.16 7 8/26/04 2:00 2.80 4 5.00 0.800 2. 61 6 10/28/04 16:00 2.63 5 3.00 0.667 2.80 4 1/18/06 16:00 2.61 6 2.00 0.500 3.15 2 10/26/06 0:00 2.16 7 1.30 0.231 5.27 1 1/09/08 6:00 2.07 8 1.10 0.091 Computed Peaks 4 .56 50.00 Q. 980 I � , � i �I i i i I i �� �I �L A- T 0 F �i1�11UY B�GYI K I PRE-D�V�LUP�D s�T�F�O�WS Flow Frequency Analysis , Time Series File:predev.tsf I Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS} (CFS) Period 1. 15 2 2/09/O1 18:00 1.53 1 100.00 0.990 0.320 7 1/06/02 3:00 1.15 2 25.00 0.960 0.883 4 2/28/03 3:00 0.888 3 10.00 0.900 0.040 8 3/29/04 19:00 0.883 4 5.00 0.800 0.518 6 1/OS/05 8:00 0.776 5 3.00 0. 667 0.888 3 1/18/06 20:00 0.518 6 2.00 0.500 0.776 S 11/24/06 4:00 0.320 7 1.30 0.231 1.53 1 1/09/08 9:00 0.040 8 1.10 0.091 Computed Peaks 1.40 50.00 0. 980 ��A-T o� Svti�J4�B,��Y � �X�s7i�l G� R��VD ��1�AI Retention/Detention Facility ' Type of Facility: Detention Pond Side Slope: 2.0� H:1V Pond Bottom Length: 155.73 ft Pond Bottom Width: 77.87 ft �-- Pond Bottom Area: 12127. sq. ft Top Area at 1 ft. FB: 24341. sq. ft 0.559 acres Effective Storage Depth: 10.00 ft Stage 0 Elevation: 141.50 ft Storage Volume: 173320. cu. ft 3.979 ac-ft Riser Head: 10.00 ft . Riser Diameter: 18.00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 2.00 0.343 2 5.20 3.40 0.687 6.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 141.50 0. 0.000 0.000 0.00 12127. 0.02 141.52 243. 0.006 0.016 0.00 12145. 0.04 141.54 486. 0.011 0.022 0.00 12164. 0.�6 141.56 729. 0.017 0.027 0.00 12183 . 0.08 141.58 973. 0.022 0.031 0.00 12202. 0.10 141.60 1217. 0.�28 0.035 0.00 12220. 0.12 141.62 1462. 0.034 0.038 0.00 12239. 0.15 141.65 1830. 0.042 0.041 0.00 12267. 0 .17 141.67 2075. 0.048 0.044 0.00 12286. 0 .34 141.84 4177. 0.096 0.063 0.00 12446. 0 .51 142 .01 6307. 0.145 0.077 0.00 12607. 0.68 142 .18 8464. 0.194 0.089 0.00 12769. 0.84 142.34 10519. 0.241 0.100 0.00 12923. 1.01 142.51 12730. 0.292 0.109 0.00 13087. 1.18 142.68 14969. 0.344 0.118 0.00 13252. 1.35 142.85 17236. 0.396 0.126 O.OQ 13417. 1.52 143.02 19531. 0.448 0.134 0.00 13584 . 1.69 143.19 21854. 0.502 0.141 0.00 13752 . 1.86 143.36 24206. 0.556 0.148 0.00 13920. 2 .03 143 .53 26587. 0.610 0.155 0.00 14089. 2 .20 143 .70 28997. 0.666 0.161 0.00 14260. 2 .37 143 .87 31435. 0.722 0.167 0.00 14431. 2 .54 144 .04 33903. 0.778 0.173 0.00 14603 . 2 .71 144.21 36401. 0.836 0.179 0.00 14776. 2.88 144.38 38927. 0.894 0.184 0.00 14950. 3 .05 144.55 41484. 0.952 0.189 0.00 15125. 3 .22 144.72 44070. 1.012 0.195 0.0� 15301. 3 .39 144.89 46686. 1.072 0.200 0.00 15478. 3 .56 145.06 49333. 1.133 0.205 0.00 15656. 3.73 145.23 52009. 1.194 0.209 0.00 15835. 3.90 145.40 54717. 1.256 0.214 O.OQ 16014 . 4.06 145.56 57292. 1.315 0.219 0.00 16184 . 4.23 145.73 60059. 1.379 0.223 0.00 16365. 4.4d 145.90 62857. 1.443 �.228 0.00 16548. 4.57 146.07 65685. 1.508 0.232 0.00 16731. 4.74 146.24 68545. 1.574 0.236 0.00 16915. 4.91 146.41 71437. 1.640 0.240 �.00 17100. 5.08 146.58 74360. 1.707 0.245 0.00 17286. 5.20 146.70 76442. 1.755 0.247 0.00 17418. 5.24 146.74 77139. 1.771 0.251 0.00 17462 . 5.27 146.77 77664. 1.783 0.261 0.00 17495. 5.31 146.81 78364. 1.799 0.276 0.00 17539. 5.34 146.84 78891. 1.811 0.296 0.00 17573 . 5.38 146.88 79595. 1.827 0.322 0.00 - 17617. 5.41 146.91 80124. 1.839 0.351 0.00 17650. 5.45 146.95 60831. 1.856 0.386 0.00 17694. 5.48 146.98 81362. 1.868 �.421 0.00 17728. 5.52 147.02 82072. 1.884 0.432 0.00 177?2. 5.69 147.19 85110. 1.954 0.478 0.00 17961. 5.86 147 .36 88179. 2.024 0.517 0.00 18152 . 6.03 147.53 91281. 2.096 0.551 0.00 18343 . 6.20 147.70 94416. 2.167 0.583 0.00 18535: 6.37 147.87 97583. 2.240 0.612 0.00 18728. 6.54 148.04 100783. 2_314 0.640 0.00 18922 . 6.71 148.2Z 104017. 2 .388 0.666 0.00 19117. 6.87 148.37 107090. 2.458 0.690 0.00 19301. 7.04 148.54 110388. 2.534 0.714 0.00 19498. 7.21 148.71 113719. 2.611 0.736 0.00 19695. 7.38 148.88 117085. 2.688 0.758 0.00 19894 . 7.55 149.05 120483. 2.766 0.779 0.0� 20093 . 7.72 149.22 123916. 2.845 0.799 0.00 20294 . 7.89 149.39 127383 . 2.924 0.819 0.00 20495. 8.06 149.56 130885. 3 .005 0.838 0.00 20697. 8.23 149.73 134421. 3.086 0.857 0.00 20901. 8 .40 149.90 137991. 3.168 O.B75 0.00 21105. 8.57 150.07 141596. 3.251 0.893 0.00 21310. 8.74 150.24 145236. 3 .334 0.911 0.00 21516. 8.91 150.41 148911. 3.419 0.928 0.00 21722. 9.08 150.58 152622. 3.504 0.944 0.00 21930. 9.25 150.75 156368. 3.590 0.961 0.�0 22139. 9.42 150.92 160149. 3 .677 0.977 0.00 22349. 9.59 151.09 163966. 3 .764 0.993 0.00 22559. 9.76 151.26 167819. 3 .853 1.010 0.00 22771. 9.93 151.43 171708. 3.942 1.020 0.00 22983 . 10.00 151.50 173320. 3.979 1.030 0.00 23071. 10.10 151.60 175634. 4.032 1.500 0.00 23196. 10.20 151.70 177960. 4 .085 2.350 0.00 23322 . '' 10.30 151.80 180298. 4.139 3 .460 0.00 23448. 10.40 151.90 182649. 4 .193 4.760 0.00 23575. 10.50 152.00 185013. 4 .247 6.240 0.00 23702. 10.60 152.10 187390. 4 .302 7.670 0.00 23829. 10.70 152.20 189779. 4.357 8.210 0.00 23957. 10 .80 152.30 192181. 4.412 8.710 0.00 24084 . 10.90 152.40 194596. 4.467 9.180 0.00 24213 . 11.00 152.50 197024. 4 .523 9.620 0.00 24341. � 11.10 152 .6a 199464. 4 .579 10.05a 0.00 24470. 11.20 152.70 201918. 4.635 10.450 0.00 24599. 11.30 152 .8Q 204384. 4.692 10.840 0.00 24728. 11.40 152 .90 206863 . 4.749 11.220 0.00 24858. 11.50 153.00 209356. 4.806 11.580 0.00 24988. 11.60 153 .10 211861. 4.864 11.930 0.00 25119. 11.70 153 .20 214379. 4.921 12 .270 0.00 25249. 11.80 153.30 216911. 4.980 12.590 0.00 25380. 11.90 153.40 219455. 5.038 12.920 0.00 25512 . Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 5.27 1.53 1.01 9.77 151.27 167990. 3.857 2 2 .63 ******* 0.93 8.91 150.41 148997. 3.421 3 2.64 ******* 0.78 7.60 149.10 121511. 2.790 4 2.80 ******* 0.69 6.88 148.38 107340. 2.464 � 5 3.12 ******* 0.73 7.18 148.68 113106. 2.597 6 1.67 ******* 0.46 5.62 147.12 83922. 1.927 7 2.07 ******* 0.24 4.86 146.36 70633. 1.622 8 2.16 ******* 0.21 3.57 145 .07 49461. 1.135 ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:rdout Inflow/Outflow Analysis Peak Inflow Discharge: 5.27 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 1.01 CFS at 15:00 on Jan 9 in Year 8 Peak Reservoir Stage: 9.77 Ft Peak Reservoir Elev: 151.27 Ft Peak Reservoir Storage: 167990. Cu-Ft . 3.857 Ac-Ft Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS � � � 0.013 36322 59.234 59.234 40.766 0.4�8E+00 0.039 4617 7.529 66.763 33.237 0.332E+00 0.065 4622 7.538 74.300 25.700 0.257E+00 0.092 4146 6.761 81.062 18.938 0.189E+00 0.118 3376 5.506 86.567 13 .433 0.134E+00 0.144 2693 4.392 90.959 9.041 0.904E-01 0.170 1833 2.989 93.948 6.052 0.605E-01 0.196 1390 2.267 96.215 3 .785 0.379E-01 0.222 956 1.559 97.774 2.226 0.223E-01 0.248 817 1.332 99.106 0.894 0.894E-02 0.274 92 0.150 99.256 0.744 0.744E-02 'I 0.301 40 0.065 99.322 0.678 0.678E-02 0.327 36 0.059 99.380 0.620 Q.620E-02 0.353 23 0.038 99.418 0.582 0.582E-02 0.379 27 0.044 99.462 0.538 0.538E-02 0.405 18 0.029 99.491 0.509 0.509E-02 0.431 27 0.044 99.535 0.465 0.465E-02 0.457 38 0.062 99.597 0.403 0.403E-02 0.483 19 0.031 99.628 0.372 0.372E-02 i �� � 0.510 14 0.023 99.651 0.349 0.349E-02 0.536 20 0.033 99.684 0.316 0.316E-02 0.562 11 0.018 99.702 0.298 0.298E-02 0.588 14 0.023 99.724 0.276 0.276E-02 0.614 20 0.033 99.757 0.243 0.243E-02 0.640 15 0.024 99.781 0.219 0.219E-02 0.666 26 0.042 99.824 0.176 0.176E-02 I 0.692 28 0.046 99.870 0.130 0.130E-02 0.718 13 0.021 99.891 0.109 0.109E-02 0.745 14 0.023 99.914 0.086 0.864E-03 0.771 7 0.011 99.925 0.075 0.750E-03 0.797 10 0.016 99.941 0.059 0.587E-03 0. 823 5 0.0�8 99.949 0.051 0.506E-03 0.849 12 0.020 99.969 0.031 0.310E-03 0.875 5 0.008 99.977 0.�23 0.228E-03 0.901 5 0.008 99.985 0.015 0.147E-03 � 0.927 8 0.013 99.998 0.002 0.163E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance-------� Cutoff Base New �Change Probability Base New �Change 0.260 I 0.91E-02 O.S1E-02 -11.9 � 0.91E-02 0.260 0.247 -4 .9 0.328 � 0.62E-02 0.62E-02 -1.0 � 0.62E-02 0.328 0.326 -0.6 0.397 I 0.49E-02 0.52E-02 7.0 � 0.49E-02 0.397 0.426 7.4 0.465 � 0.37E-02 0.39E-02 4 .4 � 0.37E-02 0.465 0.485 4.4 0.533 � 0.28E-02 0.32E-02 12 .1 � 0.28E-02 0.533 0.577 8.3 0.601 � 0.22E-02 0.25E-02 16.4 � 0.22E-02 0.601 0.640 6.4 0 .669 � 0.15E-02 0.18E-02 18.7 I 0.15E-02 0.669 0.684 2 .2 0 .738 � O.10E-02 0.91E-03 -11.1 � �. 10E-02 0.738 0.725 -1.7 0.806 � 0.60E-03 0.57E-03 -5.4 � 0.60E-03 0.806 0.791 -1.9 0.874 � 0.36E-03 0.23E-03 -36.4 � 0.36E-03 0.874 0.844 -3 .4 0.942 � 0.21E-03 O.00E+00 -100.0 � 0.21E-03 0.942 0.887 -5.9 1.01 I 0.15E-03 O.00E+00 -100.0 � 0.15E-03 1.01 0.902 -10.8 1.08 � 0.82E-04 O.00E+00 -100.� I 0.82E-04 1.08 0.919 -14.8 Maximum positive excursion = 0.049 cfs ( 9.1$) occurring at 0.539 cfs on the Base Data:predev.tsf and at 0.588 cfs on the New Data:rdout.tsf Maximum negative excursion = 0.216 cfs (-18.9�) occurring at 1.14 cfs on the Base Data:predev.tsf and at 0.928 cfs on the New Data:rdout.tsf � X t5 TI A1(n CU�lld 1TlON O� T�-}� 5! 7� �a.✓C�� /�- Flow Frequency Analysis Time Series File:prelot.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS} Period 0.038 4 2/09/O1 2:00 0.091 1 100.00 0.990 0.020 7 1/05/02 16:00 0.049 2 25.00 0.960 0.049 2 2/27/03 7:00 0.039 3 10.00 0.900 0.008 8 3/24/09 19:00 0.038 4 5.00 0.800 0.021 6 1/05/05 8:00 0.035 5 3.00 0.667 0.039 3 1/18/06 16:00 0.021 6 2.00 0.500 0.035 5 11/24/06 3:00 0.020 7 1.30 0.231 0.091 1 1/09/08 6:00 0.008 8 1.10 0.091 � Ccmputed Peaks 0. 077 50.00 0. 980 (��ciS S = O, �"3 a-��YeS ����GOf��p CouD lTrvN o�= Ti�� s � TL �cwC-�� rT Flow Frequency Analysis Time Series File:devlot.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.055 4 2/09/O1 2:00 0.120 1 100.00 0. 990 0.038 7 1/05/02 16:00 0.068 2 25.00 0. 960 0.068 2 2/27/03 7:00 0.058 3 10.00 0.900 0.034 8 8/26/04 2:00 0.055 4 5.00 0.800 0.042 6 10/28/04 16:00 0.054 5 3.00 0.667 0.058 3 1/18/06 16:00 0.092 6 2.00 0.500 0.054 5 11/29/06 3:00 0.038 7 1.30 0.231 0.120 1 1/09/OS 6:00 0.034 8 1.10 0.091 Computed Peaks 0. 102 50.00 0.980 �p = o, 1 � a.��e; 3 z a.�ti�,y ��uss = �• I ,' I .�L,�T OF S U�1�1�YJ3�2�DIt �tv�l,c� �'�l� S i T� W �Tff �-Db ITrU�/�-L 1 M�'E��J��us 1+��� Flow Frequency Analysis Time Series File:devn.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS} (CFS) Period 2. 65 5 2/09/O1 2:00 5.30 1 100.00 0. 990 2.09 8 1/05/02 16:00 3.18 2 25.00 0. 960 3.14 3 2/27/03 7:00 3.14 3 10.00 0. 900 2.19 7 8/26/04 2:00 2.82 4 5.00 0.800 2.63 6 10/28/04 16:00 2.65 5 3.00 0.667 2.82 4 1/18/06 16:OQ 2. 63 6 2.00 0.500 3. 18 2 10/26/06 0:00 2.19 7 1.30 0.231 5.30 1 1/09/08 6:00 2.09 8 1.10 0.091 Computed Peaks 4.59 50.00 0.980 ��,�T OF Svuhl Y8l2cbK �D�D �D�I��1 UJ�TH N��i/ IM �UtvuS /��e�} - Retention/Detention Facility Type of Facility: Detention Pond Side Slope: 2.00 H:1V Pond Bottom Length: 155.73 ft Pond Bottom Width: 77.87 ft Pond Bottom Area: 12127. sq. ft Top Area at 1 ft. FB: 24341. sq. ft 0.559 acres Effective Storage Depth: 10.00 ft Stage 0 Elevation: 141.50 ft Storage Volume: 173320. cu. ft 3.979 ac-ft Riser Head: 10.00 ft . Riser Diameter: 18.00 inches Number of orifices: 2 Full Head Pipe � Orifice # Height Diameter Discharge Diameter I, (ft) (in) (CFS) (in) 1 0.00 2.00 0.343 2 5.20 3.40 0.687 6.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 141.50 0. 0.000 0.000 0.00 12127. 0.02 141.52 243. 0.�06 0.016 0.00 12145. 0.04 141.54 486. 0.011 0.022 0.00 12164. 0.06 141.56 729. 0.017 0.027 0.00 12183_ 0.08 141.58 973. 0.022 0.031 0.00 12202. 0.10 141.60 1217. 0.028 0.035 0.00 12220. 0.12 141.62 1462. 0.034 0.038 0.00 12239. 0 .15 141.65 1830. 0.042 0.041 0.00 12267. 0.17 141.67 2075. 0.048 0.044 0.00 12286. 0.34 141.84 4177. 0.096 0.063 0.00 12446. 0.51 142.01 6307. 0.145 0.077 0.40 12607. 0.68 142.18 8464. 0.194 0.089 0.00 12769. 0.84 142.34 10519. 0.241 0.100 0.00 12923. 1.01 142.51 12730. 0.292 0.109 0.00 13087. 1.18 142 .68 14969. 0.344 0.118 0.00 13252. 1.35 142 .85 17236. 0.396 0.126 0.00 13417. 1.52 143.02 19531. 0.448 0.134 0.00 13584. 1.69 143.19 21854. 0.502 0.141 0.00 13752. 1.86 143.36 24206. 0.556 0.148 0.00 13920. 2 .03 143.53 26587. 0.610 0.155 0.00 14089. 2 .20 143 .70 28997. 0.666 0.161 0.00 14260. 2.37 143 .87 31435. 0.722 0.167 0.00 14431. 2.54 144.04 33903. 0.778 0.173 0.00 14603. 2.71 144.21 36401. 0.836 0.179 0.00 14776. 2 .88 144.38 38927. 0.894 0.184 0.00 14950. 3 .05 144.55 41484. 0.952 0.189 0.00 15125. 3.22 144.72 44070. 1.012 0.195 0.00 15301. 3 .39 144 .89 46686. 1.072 0.200 0.00 15478. 3.56 145.06 49333. 1.133 0.205 0.00 15656. 3.73 145.23 52009. 1.194 0.209 0.00 15835. 3.90 145.40 54717. 1.256 0.214 0.00 16014 . 4.06 145.56 57292. 1.315 0.219 0.00 16184 . 4.23 145.73 60059. 1.379 0.223 �.00 16365. 4.40 145.90 62857. 1.443 0.228 0.00 16548. 4.57 146.07 65685. 1.508 0.232 0.00 16731. 4.74 146.24 68545. 1.574 0.236 0.00 16915. 4.91 146.41 71437. 1.640 0.240 0.00 17100. 5.08 146.58 74360. 1.707 0.245 0.00 17286. 5.20 146.70 76442. 1.755 0.247 0.00 17418. 5.24 146.74 77139. 1.771 0.251 0.00 17462. 5.27 146.77 77664. 1.783 �.261 0.00 17495. 5.31 146.81 78364. 1.799 �.276 0.00 17539. 5.34 146.84 78891. 1.811 0.296 0.00 17573. 5.38 146.88 79595. 1.827 0.322 0.00 . 17617. 5.41 146.91 80124. 1.839 0.351 0.00 17650. 5.45 146.95 80831. 1.856 0.386 0.0a 17694 . 5.48 146.98 81362. 1.868 0.421 0.00 17728. 5.52 147.02 82072. 1.884 0.432 0.00 17772. 5.69 147.19 85110. 1.954 0.478 0.00 17961. 5.86 147.36 88179. 2 .024 0.517 0.00 18152. 6.03 147.53 91281. 2.096 0.551 0.00 18343. 6.20 147.70 94416. 2.167 0.583 0.00 18535. 6.37 147.87 97583. 2.240 0.612 0.00 18726. 6.54 148.04 100783. 2.314 0.640 0.00 18922. 6.71 148.21 104017. 2 .388 0.666 0.00 19117. 6.87 148.37 107090. 2.458 0.690 0.00 19301. 7.04 148.54 110388. 2.534 0.714 0.00 19498. 7.21 148.71 113719. 2.611 0.736 0.00 19695. 7.38 148.88 117085. 2.688 0.758 0.00 19694. 7.55 149.05 120483. 2.766 0.779 0.00 20093. 7 .72 149.22 123916. 2 .845 0.799 0.00 20294. 7.89 149.39 127383. 2 .924 0.819 0.00 20495. 8.06 149.56 130885. 3.005 0.838 0.00 20697. 8.23 149.73 134421. 3.086 0.857 0.00 20901. 8.40 149.90 137991. 3.168 0.875 0.00 21105. 8.57 150.07 141596. 3.251 0.893 0.00 21310. 8.74 150.24 145236. 3.334 0.911 0.00 21516. 8.91 150.41 148911. 3.419 0.928 0.00 21722. 9.08 150.58 152622. 3.504 0.944 0.00 21930. 9.25 150.75 156368. 3 .590 0.961 0.00 22139. 9.42 150.92 160149. 3.677 0.977 �.00 22349. 9.59 151.09 163966. 3.764 0.993 0.00 22559. 9.76 151.26 167819. 3.853 1.010 0.00 22771. 9.93 151.43 171708. 3.942 1.020 0.00 22983. 10.00 151.50 173320. 3.979 1.030 0.00 23071. 10.10 151.60 175634. 4.032 1.500 0.00 23196. 10.20 151.70 177960. 4.085 2.350 0.00 23322 . 10.30 151.80 180298. 4.139 3 .460 0.00 23448. 10.40 151.90 182649. 4 .193 4 .760 0.00 23575. 10.50 152.00 185013. 4.247 6.240 0.00 23702. 10.60 152.10 187390. 4.302 7.670 0.00 23829. 10.70 152.20 189779. 4.357 8.210 0.00 23957. 10.80 152.30 192181. 4.412 8.710 0.00 24084 . 10.90 152.40 194596. 4.467 9.180 0.00 24213 . 11.00 152 .50 197024. 4.523 9.620 0.00 24341. 11.10 152.60 199464. 4.579 10.050 0.00 24470. 11.20 152.70 201918. 4.635 10.450 0.00 24599. 11.30 152.80 204384. 4.692 10.840 0.00 24728. 11.40 152.90 206863. 4.749 11.220 0.00 24858. 11.50 153 .00 209356. 4.806 11.580 0.00 24988. 11.60 153 .10 211861. 4 .864 11.930 0.00 25119. 11.70 153.20 214379. 4.921 12.270 0.00 25249. 11.80 153 .30 216911. 4.980 12.590 0.00 25380. 11.90 153 .40 219455. 5.038 12.920 0.00 25512. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 5.30 1.53 1.01 9.80 151.30 168772. 3.874 2 2 .65 ******* 0.93 8.95 150.45 149801. 3.439 3 2.65 ******* 0.79 7.64 149.14 122343. 2.809 4 2.82 ******* 0.70 6.92 148.42 108077. 2.481 - 5 3.14 ******* 0.73 7.20 148.70 113530. 2.606 6 1.6B ******* 0.47 5.64 147.14 84295. 1.935 7 2.09 ******* 0.24 4 .89 146.39 71123. 1.633 8 2.19 ******* 0.21 3 .62 145.12 50271. 1.154 Route Time Series through Facility Inflow Time Series File:devn.tsf Outflow Time Series File:rdoutn Inflow/Outflow Analysis Peak Inflow Discharge: 5.30 CFS at 6:00 on Jan 9 in Year 8 I Peak Outflow Discharge: 1.01 CFS at 14:00 on Jan 9 in Year 8 Peak Reservoir Stage: 9.80 Ft Peak Reservoir Elev: 151.30 Ft Peak Reservoir Storage: 168772. Cu-Ft . 3.874 Ac-Ft Flow Duration from Time Series File:rdoutn.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS $ $ � 0.013 36273 59.154 59.154 40.846 0.408E+00 0.04a 4651 7.585 66.738 33.262 0.333E+00 0.066 4596 7.495 74.234 25.766 0.258E+00 0.092 4136 6.745 80.978 19.022 0.190E+00 0 .118 3408 5.558 86.536 13 .464 0.135E+00 0.144 2696 4.397 90.933 9.067 0.907E-01 0.171 1851 3.019 93.951 6.049 0.605E-01 0.197 1391 2.268 96.220 3.780 0.378E-01 0.223 976 1.592 97.811 2.189 0.219E-01 0.249 791 1.290 99.101 0.899 0.899E-02 0.275 95 0.155 99.256 0.744 0.744E-02 0.302 36 0.059 99.315 0.685 0.685E-02 0.328 40 0.065 99.380 0 .620 0.620E-02 0.354 20 0.033 99.413 0.587 0.587E-02 0.380 23 0.038 99.450 0.550 0.550E-02 0.407 18 0.029 99.480 0.520 0.520E-02 �.433 28 0.046 99.525 0.475 0.475E-02 0.459 42 0.068 99.594 0.406 0.406E-02 0 .485 21 0.034 99.628 0.372 0.372E-02 0.511 15 0.024 99.653 0.347 0.347E-02 0.538 18 0.029 99.682 0.318 0.318E-02 0.564 12 0.020 99.702 0.298 0.298E-02 0.590 14 0.023 99.724 0.276 0.276E-02 0.616 20 0.033 99.757 0.243 0.243E-02 0.642 15 0.024 99.781 0.219 0.219E-02 0.669 24 0.039 99.821 0.179 0.179E-02 0.695 28 0.046 99.866 0.134 Q.134E-02 0.721 15 0.024 99.891 0.109 0.109E-02 0.747 14 0.023 99.914 0.086 0.864E-03 0.774 8 0.013 99.927 0.073 0.734E-03 0.800 9 0.015 99.941 0.059 0.587E-03 0.826 5 0.008 99.949 0.051 0.506E-03 0.852 12 0.020 99.969 0.031 0.310E-03 0.878 5 0.008 99.977 0.023 0.228E-03 0.905 5 0.008 99.985 0.015 0.147E-03 . 0.931 7 0.011 99.997 0.003 0.326E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: rdoutn.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New $Change Probability Base New �Change 0.260 � 0.91E-02 0.81E-02 -11.4 � 0.91E-02 0.260 0.248 -4.5 0.328 � 0.62E-02 0.62E-02 -0.8 � 0.62E-02 0.328 0.327 -0.5 0.397 � 0.49E-02 0.53E-02 9.1 � 0.49E-02 0.397 0.429 8.1 0.465 � 0.37E-02 0.39E-02 5.3 � 0.37E-02 0.465 0.487 4.8 ' 0.533 � 0.28E-02 0.32E-02 13 .2 � 0.28E-02 0.533 0.580 8 .8 �' 0.601 ( 0.22E-02 0.26E-02 17.9 � 0.22E-02 0.601 0.644 7 .1 0.669 ' 0.15E-02 0.18E-02 19.8 � 0.15E-02 0.669 0.686 2.5 0.738 � O.10E-02 0.93E-03 -9.5 ( O.10E-02 0.738 0.729 -1.2 0.806 � 0.60E-Q3 0.57E-03 -5.4 � 0.60E-03 0.806 0.795 -1.3 0.874 I 0.36E-03 0.26E-03 -27.3 � 0.36E-03 0.874 0.846 -3.2 0.942 � 0.21E-03 O.00E+00 -lOQ .O � 0.21E-03 0.942 0.889 -5.7 ', 1.01 � 0.15E-03 O.00E+00 -100.0 � 0.15E-03 1.01 0.904 -10.5 1.08 � 0.82E-04 O.00E+00 -100.0 � 0.82E-04 1.08 0.922 -14.5 Maximum positive excursion = �.051 cfs ( 9.5�) occurring at 0.539 cfs on the Base Data:predev.tsf and at 0.591 cfs on the New Data:rdoutn.tsf Maximum negative excursion = 0.213 cfs (-18.6�) occurring at 1.14 cfs on the Base Data:predev.tsf and at 0.932 cfs on the New Data:rdoutn.tsf - ' ;, : _. �� � • a: _- �:�. ,