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Home My WebLink About03278 - Technical Information Report Core Desi n,Inc. I �� 9 CORE14711 N.E.29fh Place,Suite 101 � \ � DESIGN Bellevue,Washington98007 v 425.885.7877 Fax425.885.7963 A, www.coredesigninc.com -�c � I � ��I , ,I ' I I � TECHNICAL INFORMATION REPORT FOR WEDGEWOOD LANE DIVISIONS l, 2 AND 3 ��n oF kiVc�D RENTON, WASHINGTON R E C� SEP 2 Q REG'D PLAN REVIEW ,� �'*`?/ , , 6 vP�• T �'v cvO' !.�'. .S5. .�� i � Prepared by: Philip D. Sarandos, E.I.T. �� ' � `'�'., �„ .� t,� Project Manager: Edgar T. Jones, P.E. ,�, ,� ,,�o sz � •� Core Project No.: 01045 ' ,�s�.�'�S:•�';v�� - l4 . Date: July, 2005 � �� • �� w �;.��:�� . .�.�� _ �_ RevisedSepte�nber, 2005 E}�iRES 4—Le—`;i 9-��-05 SEP 2 � 2s�� ; �t�I�DiNC��4�'iv:� ENGINEERING PLANNING SURVEYING �'3278 WEDGEWOOD LANE - ' TABLE OF CONTENTS L Project Overview II. Conditions & Requirements Summary � III. Offsite Analysis A. Upstream Tributary Area � B. Bypass Area C. Downstream Analysis I IV. Flow Control and Water uali Facili Anal sis and Desi Q tY tY Y � � A. Hydrologic Analysis B. Basin A Detention Routing Calculation C. Basin A Water Quality Volume Calculation D. Basin A Emergency Overflow E. Basin B Detention Routing Calculation � F. Basin B Water Quality Volume Calculation G. Basin B Emergency Overflow V. Conveyance System Analysis and Design A. Primary Conveyance System B. Culvert Sizing VI. Special Reports and Studies — N/A VII. Other Permits —N/A VIII. ESC Analysis and Design A. Basin A B. Basin B IX. APPENDIX Core Design. lnc. �1'EllGE��00D LANE Pa�e l I. PROJECT OVERVIEW The Preliminary Plat of Wedgewood Lane is located in the city of Renton, East of 142nd ', Ave. SE and south of N.E. 10`h Street. Please see the Vicinity Map on the next page. , This project site includes multiple parcels that currently have approximately 7 single- , family residences and associated garages and outbuildings. A Type II Wetland runs just �, outside of the eastern property line along the majority of the property. There is a seasonal stream that cuts through the northern portion of the property. The existing ground is covered with tall grass and forestland. The property's eastern boundary borders the proposed plats of Rosemonte and East Renton and other undeveloped parcels, all of which are in King County. On the project's western boundary are two proposed plats, Aspen Woods by Harbour Homes and Cambridge Lane by Cambridge Homes (a.k.a. Rutledge Property). Please see the Existing Conditions Exhibit at the end of this section for a visual depiction of the existing site. The final plat will be developed in three divisions. The adjacent preliminary plat of Cambridge Lane will be developed separately, but the stormwater runoff from it will be tributary to the Wedgewood Lane stormwater system. We are designing the stormwater detention and water quality facilities to serve all three divisions of the Wedgewood Lane project, as well as the Cambridge Lane project that is currently being reviewed by City staff. We feel that constructing one system to handle the stormwater from all of these projects will benefit the residents in the long term with reduced per lot maintenance -' expenses and will improve the overall appearance of these neighborhoods, as compared to the option of having smaller, individual facilities for each of the projects. In order to further enhance these neighborhoods, our client has directed us to design the facilities to have a more natural appearance than traditional ponds. Core Design Inc. has discussed this proposed system with the City of Renton in meetings and with a letter dated December 20, 2004 and received conceptual approval of the concepts presented herein in a response letter dated January 6, 2005. Divisions 1 and 2 of Wedgewood Lane and the Cambridge Lane project are required to satisfy the requirements of the 1998 King County Surface Water Design Manual (KCSWDM), whereas Division 3 is required to satisfy the 2005 KCSWDM. Both manuals have the same requirements for detention and water quality standards for this site, specifically Level 2 Flow Control and Basic Water Quality. The primary difference in the manuals is that the 2005 KCSWDM introduces incentives for low impact development, such as encouraging dispersion of roof runoff in order to more closely match the performance of an undisturbed site. This project proposes to utilizes low impact development features in order to incorporate the latest methodology and to help sustain the health of the wetland complex to the east of the site. Detention for the majority of the site (Basin A) will be provided by the detention pond located in Division 3, hereafter referred to as Pond A. Water quality enhancement for the same tributary area will be provided by a wetpool in Pond A. The outflow of Pond A will be discharged via a slotted drain flow spreader to the onsite Type II Wetland. A separate detention and water quality facility, Pond B, will be designed to serve a much smaller basin in the northeast portion of the site. This area will be referred to as Basin B. This pond similarly will discharge to the on-site wetland through a slotted drain flow spreader. Corc 1)esign. Inc. ��'EDGE1�'OOD L:a1E Pa�c 1 �` Please see the Deve�loped Conditions Exhibit at the end of this section for the locations of �� the proposed stormwater facilities and their respective basins. The roof and footing drains of 10 lots from Basin A, totaling 1.�0 acres, and 6 lots from Basin B, totaling 1.01 acres �vill bypass the respective detention facilities and will be dispersed to the wetlands through multiple dispersion trenches, in accordance with the � "Basic Dispersion" provisions of the 2005 KCSWDM, specifically Section 52.2 and Appendix G In order to mimic the existing conditions and help to maintain the health of f the wetland area, the dispersion trenches will distribute stormwater throughout the ' wetland complex. This lots that will be dispersed are shown in detail on the Developed Conditions Exhibit. Please also see the report by Alder NW that discusses the wetland recharge concept. � I � � ,, � � ' I { C'ore llecign,Inc. ��i�:DGER'OOD 1.:aVE I'age 2 / � i — • :i -i � . / � ,� i� I' � / '; �i �� a� •�• i � , i ` �� .� _ � � �N,��''Ti�`� �` • �; �-'�fj S� ' \�\ �` r � - . \ ; `�1� '� — - � ►� `��:� \ � ` \ ��i� . � — � �� •'\\\�� `� `�``" ► �� 1 �� \ � �� `\ `�, _ ��;�. _,.`�► ► ` ��` � , ,� _ - .' m � �� \� _ _ � �� '►6, �� ` - ,t� . '�L`�`� ►'�!��` \ �'��'`\ . � ��. � � � ` 1 \ t � ` �� i' . . �� •��` ` �� .ir��a``_�` �� •� �� `\ � , '45h��. . , ` � � ♦ � �.,�.; '� �..��. �� ,. � , � , ..-�•.� � \.�� s►*,�. �. . � �� . .,...�,.��..._.�\ �� , . _ �_a�. a _� _ \\ \�� 1��`�;, �,�•i� �`\`__�,'- _ `� "' � � `;�`� � �� P � � ��I�� . � _ `, � '`+� � ' `'`' '�� `'�,•,• � ��. `�� .,�.�� ,�, ,�� ►�� \\ � �+� ��,� > 1 . `�►�. \ . �1\��. �,� � � �� .�- � f ► , :• "►� ♦ �`.�� ,�� , , �t� ♦��;. � � s �� '_ ��t`��••�1. �```��` .\.� ,,�,��►�� :z ' �..� �..��► � , , �j��;.,� �� \ .��`.�� . � r4�a�` �\ . . , . , , . � ,,.,. ��...� ��►��` �� %� - �� `� 1, a`��`��\��`�a�,<��`�` �; � � .�/ .`�'� N . - o � ... .� �� \ �, �,��4 �� ♦ — �,��1/.�,_'\� ,ti`�� .r �, . �� ♦ � � �' .� �` ' ' � ' ' s ' �t � ��`� `�'�:.'a1.�+�``�,� , I . y' � � "•.��. �� • � � �� i , . ♦ `�� ♦ � � �� I��.;:-� � ��♦ .� ! / �` �,��.`� ,\ � �i � �/�� ` ��•�� . - I �� // �I��_�_� � ` � � � ►� � /�% , � ,� � ,,� \ . `� . + z ..�i/ ��_�� ,�, � ` � �� %�� /�-�f�� ` i � ��/.d � �i��`/ � / � : I ( .,��/ � . ��% � �i � � / �/ �/ 'I/ / �� ♦ • � / i iii • ii � �,�-� � �Sf`� �/Ir3: % � I / I ��j ,; �' ,� e , �� / i � . � � , /� , � � � , . . ., , - _�� _. —_ _ ��i/__% , /� / i%/� � ., , . „ �i��--��a,.��' :7a✓� - - ] r��i��i=.11�1�•��.....�-_?1�� _—� —__ — ��_"__' � u:�iiiiiiiiiiii � :'� ':�//� � � � � � __ _ s � � , • //. �� ,. .� �• � �/ � � ` IL CONDITIONS & REQUIREMENTS SUMMARY • Core Requirement#1: Discharge at the Natural Location, Section 1.2.1 There are two detention facilities, as well as 13 lots that will discharge via level spreaders to the wetland buffer east of the project. • Core Requirement#2: Offsite Analysis, Section 1ZZ An offsite analysis was performed for the project and is described in Section IlI of this report. Due to the size and proposed impact of the project, a Level 1 downstream analysis was performed for the Wedgewood site. There is currently 0.23 acres of existing frontage � road that will be routed through the Basin A detention facility. An additiona10.16 acres of existing frontage road will bypass the site and the detention facility. • Core Requirement#3: Flow Control, Section 1.2.3 Level II flow control is proposed for both basins: match durations for 50% of 2-yr through 50-yr peaks. In addition, discharge from both detention facilities will meet level � flow control requirements: 2-year and 10-year pond discharge to match pre-developed flows. • Core Requirement#4: Conveyance 5ystem, Section 1.2.4 The conveyance system will be a pipe and catch basin system. A complete backwater analysis is presented in Section V of this report. • Core Requirement#5: Erosion and Sediment Control, Section 1.2.5 Erosion and sediment control will be provided. Sizing calculations are presented in Section VIII of this report. • Core Requirement#6: Maintenance and Operations, Section 1.2.6 � To be provided following initial review. • Core Requirement#7: Financial Guarantees and Liability, Section 1.2.7 To be provided follo�i in� initial revie��. ('ore Design. Inc. «EDGE��'OOD LANE Ya�e�J IL CONDITIONS & REQUIRE112ENTS SU11�iMARY (CONT.) • Core Requirement#8: `�'ater Quality, Section 1.2.8 Water quality for both basins will be provided through a wet pool within each detention pond. Sizing calculations can be found in Section N of this report. • Special Requirement #1: Other Adopted Area-SpeciGc Requirements, Section 1.3.1 N/A—Not applicable to this project. • Special Requirement#2: Floodplain/Floodway Delineation, Section 1.3.2 ' N/A—Not applicable to this project. • Special Requirement#3: Flood Protection Facilities, Section 1.3.3 N/A—Not applicable to this project. • Special Requirement #4: Source Control, Section 1.3.4 t To be addressed during final design. ti • Special Requirement#5: Oil Control, Section 1.3.5 N/A—Not applicable to this project. � � � Core Desi�n. I��c. ��N�DGE«'OOn L_�\�E Pa�e � III. OFFSITE ANALYSIS tThis offsite analysis was performed on August 29, 2002 and on March 25, 2003. A. UPSTREAM TRIBUTARY AREA 1.70 acres of the offsite Rutledge Property (being platted as Cambridge Lane) in addition to the east half of Hoquiam Ave. NE for the majority of the site's frontage will be detained on site. Stormwater runoff from these areas will be collected in the developed project site's system. B. DOWNSTREAM ANALYSYS Drainage from the Wedgewood Lane property naturally sheet flows across the site to an offsite Type II wetland where it merges with other wetlands to the northeast from the project site to form Honey Dew Creek. This drainage continues offsite under S.E. 116`h Street through a 24" CMP culvert. From here the drainage continues north in a well- defined channel for more than '/4 mile. In the vicinity of the %4 mile downstream point, Honey Creek has a bank-to-bank width of approximately 5' —10' with an intermittent free stone channel approximately 2' — 5'wide. The stream was dry with no evidence of recent surface water flows, when walked in August, 2002. Substantial debris was observed within the stream. A neighbor on the east side of the creek said the creek contains � consistent flows through the winter until around May. Some moist soil was noted in adjacent areas. From the '/4 mile downstream point, Honey Creek drains northerly through a heavily wooded, brushy area for approximately another '/4 mile, where it turns westerly for approximately 800 feet and flows under Hoquiam Avenue NE via a 24" � concrete culvert. 'The creek continues flowing through a heavily forested, brushy area for approximately 1,200 feet, where it enters a 48" concrete storm drainage system in Duvall Avenue NE. At this intake, the creek was approximately 10'— 15'wide with no evidence of recent surface flows. From Duvall Avenue NE, the creek continues flowing westerly via an underground system within a commercial development near the intersection of Duvall Avenue NE and NE Sunset Boulevard. The creek continues northwesterly through established channels and eventually enters May Creek approximately 2 %z miles from the site, which discharges to Lake Washington north of Kennydale. No evidence of erosion or flooding was found during this downstream analysis. See the attached Do«�nstream Tributary Area map for a graphical depiction of this route. � I', ('ore Design. Inc. ��FnGE��`OOD L,a\F. Ya�c t� C. BYPASS AREA ' � The N.E. 10`h Street bypass area includes 0.09 acres of impervious frontage. Since the area of existing impervious to be removed, 0.10 acres, is approximately equal to the area _ of proposed impervious, the peak flows will not increase and therefore, no additional detention is required. Similarly, on Hoquiam Avenue, 0.02 acres of new impervious that lies south of the project entrance will not be tributary to the project's stormwater i facilities. However, this area is less than the 0.12 acres of existing impervious surface to the north of the entrance road that will no�� be detained and treated for water quality enhancement. As previously stated, the roof and footing drains of 10 lots from Basin A, totaling 1.50 � acres, and 6 lots from Basin B, totaling 1.01 acres will bypass the respective detention - facilities and will be dispersed to the wetlands through multiple dispersion trenches. The 2005 KCSWDM encourages the implementation of best management practices (BMP) for flow control and provides credits for their use in Section 5.2.2 of the manual. The "Basic Dispersion" BMP will be utilized, which will help to maintain the health of the wetland to the east. The impervious area of each of the dispersed lots will be modeled as 50% impervious and 50% grass in the sizing of the detention ponds for their respective basins. � The dispersion trenches have been designed and sited to satisfy the criteria of Section C.2.4.4 of the KCSWDM. This section of the manual dictates that 10 LF of trench is required for every 700 SF of impervious area that is tributary to it, up to a maximum of � 50 feet. It also specifies that a vegetated flowpath length of 25 feet is required and that the "outer edge of the vegetated flowpath segment for the dispersion trench must not overlap with other flowpath segments". These criteria and the others specified in the manual have all been satisfied. The impervious areas used to determine each dispersion trench length are summarized in the table below. �, � � ;.� -.,.i � ;; �,,,. �� , ; , Lots to be Lot area Max.Impervious Add'1. Impervious Area Total dispersed (Net S� Area(SF; incL Driveway for Pond Sizing Dispersion (Basi�A lots house,driveway Area(SF� (S� Trench are listed first and atio Len th Feet Div.2-Lot 16 7,058 3,050'' N/A 1,525 37,581 Div.2-Lot 17 6,996 3,950 N/A 1,525 26,265 Div.2-Lot 18 4,950 3,050 N!A 1,525 26,265 i f Div. 3-Lot 1 13,652 3,050 2,400 2,725 2,725 Div.3-Lot 2 8,301 3,050 N/A 1,525 26,265 I' ,� Div.3-Lot 36 4,503 2,600 N/A 1,300 26,265 ' Div. 3-Lot 37 5,003 2,600 N/A 1,300 26,265 Div. 3-Lot 38 5,003 2,600 N/A 1,300 26,265 I Div. 3-Lot 39 5,003 2,600 N/A 1,300 26,265 Div. 3-Lot 40 4,876 2,600 N/A 1,300 26,265 Div. 3-Lot 18 9,081 3,050 N/A 1,525 26,265 Div.3-Lot 20 9,630 3,050 N/A 1,525 26,265 � Div. 3-Lot 21 9,400 3,050 2,400 2,725 26,265 Div. 3-Lot 27 5,500 2,850 N/A 1,425 26,265 Div.3-Lot 28 5,400 2,850 N/A 1,425 26,265 Div. 3-Lot 29 5,000 2,600 N,/A 1,300 26,265 Core nesign, Inc. ��F.DGE��'QOD L�1VN; Page ? IV. FLO`V CONTROL AND `�'ATER QUALITY FACILITY ANALYSIS AND DESIGN � A. HYDROLOGIC ANALYSIS ; The drainage analysis for the ponds was performed using the King County Runoff Time Series sof�ware. The site's soils are Alden�vood (AgC & AgD), KCRTS group Till. Please see the Appendix for the Soils Map and Rainfall Regions and Regional Scale Factors map. The site is located in the Landsburg rainfall region with a location scale factor of 0.85. Sce following tables for area breakdowns for each division. Using the pre-developed impervious and pervious areas shown in the following tables, pre-developed and developed time series were generated for each basin. The developed impervious areas were measured from the plans for the proposed infrastructure and estimated for the lots based on their sizes. Three options were used for the maximum � impervious area allowed on each lot. For the smallest lots, 2,600 SF was used to account for the houses, driveways, patios and walkways that will be constructed on them. For the medium size lots, 2,850 SF will be allowed and for the largest lots, 3,050 was used. The number of lots in each category are summarized in the tables that follow for each basin. � An additional table is included in the Appendix, which lists each lot, its allowable impervious area and the impervious area of its access driveway for those lots accessed by a longer than normal driveway such as through an access tract or panhandle. BASIN A AREA BREAKDOWN Division 1 Basin A-Div. 1 Basin A-Div. 1 Pre-Developed Developed Area (Acres Area (Acres) Till—Forest 2.70 - Till—Pasture 0.12 - Till— Grass - 1.17 Impervious- 0.01 - Existin structures Impervious- - 039 ri ht of wa Impervious- - 0.14 Access tracts Impervious-Lots - 1.13 � (9@2600sf, 8@2850sf, 1 3050s� Total 2.83 2.83 Core Design. Inc. ��'FDGE��001) I,ANl�: Nage 8 Division 2 Basin A-Div. 2 Basin A-Div. 2 � Pre-Developed Developed Area (Acres) Area (Acres) Till— Forest 5.43 - Till—Pasture 1.82 - Till—Grass - 2.98 Impervious- 0.14 - Existin structures Impervious- - 1.39 ri ht of wa Impervious- - 0.09 Access tracts Impervious-Lots - 2.61 (28@2600sf, 10 2850sf,4 3050s Lots to be Dispersed - 0.11 h (50% Impervious & 50% Pervious) 3 OSOs ; Impervious- - 0.21 t Fronta e Total 7.39 7.39 Core Design. Inc. ��EnGE��)(>1) I,.a!�H: Page 9 Division 3 II Basin A-Div. 3 Basin A-Div. 3 Pre-Developed Developed Area (Acres) Area (Acres) Till— Forest 5.35 - Till— Pasture - - ' ;' Till—Grass - 1.58 Impervious- 0.02 - Existin structures Impervious- - 1.28 ri ht of wa Impervious- - 0.06 '� Access tracts Impervious-Lots - 1.32 (11@2600sf, 9@2850sf, 1 a�3050sf Lots to be Dispersed - 022 (50% Impervious & 50% Pervious) 5 2600sf, 2 3050s� Impervious- - 0.91 Pond/access road Total 5.37 5.37 Offsite Rutledge Property Basin A-Offsite Basin A-Offsite �- Pre-Developed Developed Area (Acres) Area(Acres) y. Till—Forest 1.51 - � Till—Pasture 0.08 - � Till—Grass - 0.32 � I Imper�ious- 0.11 - Existin structures ` Impervious- - 0.79 75% of site Impervious- - 0.59 Fronta e Total 1.70 1.70 Core 1)ctiign. 1nc. ��}:DGF:��OOD I„aNE Page 10 BASIN A TOTAL DETAINED AREAS Basin A Basin A Pre-Developed Developed Area (Acres) Area (Acres) '� Till- Forest 14.99 - ' Till - Pasture 2.02 - Till- Grass - 6.05 Impervious- 0.28 11.24 Streets, SW, Roofs,etc. Total 17.29 17.29 BASIN B AREA BREAKDOWN Division 3 Basin B-Div. 3 Basin B-Div. 3 Pre-Developed Developed Area (Acres Area (Acres) Till—Forest 2.08 - Till—Pasture - - Till—Grass - 0.86 Impervious- 0.05 - Existing roads, structures Impervious- - 0.06 Roadwa � Impervious- - 0.16 ` Fronta e �� Impervious- - 0.06 Access Drivewa Impervious-Lots - 0.37 (5 2600sf, 1 a�3050s� Lots to be Dispersed - 0.20 (50% Impervious & � 50% Pervious) (1@2600sf, 23@2850sf, 3 3050s Impervious- - 0.42 Pond/access road Total 2.13 2.13 C��re Design. inc. ��EDGE«'OOD LANE Page 11 BASIN B TOTAL DETAINED AREAS � Basin B Basin B Pre-Developed Developed Area (Acres) Area(Acres) Till - Forest 2.08 - Till- Pasture - - Till- Grass - 0.86 Impervious- 0.05 1.27 Streets, SVV, Roofs, etc. Total 2.13 2.13 � Cnre Design. Inc. ��'EDGE��'OOD l..a\'E Page 1 Z B. BASIN A DETENTION ROUTING CALCULATION The detention routing calculation, a continuation of the hydrologic analysis, uses KCRTS to match the pre-developed outflow to the developed outflow by providing a site-specific amount of detention. Basin A includes offsite tributary from the proposed Cambridge Lane Development (Rutledge Property) as well as some frontage improvements. The following printout shows a 212,108 cf pond in conjunction with the documented control structure will provide enough live storage (detention) to satisfy this requirement. As designed the detention pond is 10' deep and provides 223,001 cf of live storage. 4 ti. I � ; �_, f - (`ore Design.Inc. WED(;E��'OOD l...aNE Page l3 I Basin A Retention/Detention Facility 'I Type of Facility: Detention Pond Side Slope: 2.75 H:1V Pond Bottom Length: 175.00 ft Pond Bottom Width: 76. 00 ft , Pond Bottom Area: 13300. sq. ft Top Area at 1 ft. FB: 32146. sq. ft 0.738 acres Effective Storage Depth: 10.00 ft Stage 0 Elevation: 427.50 ft ' Storage Volume: 212108_ cu. ft il 4.869 ac-ft Riser Head: 10.00 ft Riser Diameter: 24.00 inches �� Number of orifices: 2 ', Full Head Pipe ' Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 2.19 0.411 � 2 6.20 3.38 0.602 6.0 ', Top Notch Weir: None j Outflow Rating Curve: None 5tage Elevation Storage Discharge Percolation Surf Area (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) (sq. ft) 0.00 427.50 0. 0.000 0.000 0.00 13300. 0.02 427.52 266. 0.006 0.020 0_00 13328. 0.05 427.55 667. 0.015 0.028 0.00 13369. + 0.07 427.57 934. 0.021 0.034 0.00 13397. 0.09 427.59 1203. 0.028 0.039 0.00 13424 . 0.11 427.61 1471. 0.034 0.044 0.00 13452. 0.14 427.64 1876. 0.043 0.048 0.00 13494. 0. 16 427_66 2146. 0.049 0.052 0.00 13522. 0.18 427.68 2416. 0.055 0.055 0.00 13549. 0.35 427.85 4740. 0. 109 0.077 0.00 13787. 0.52 428.02 7104. 0.163 0. 094 0.00 14026. 0.69 428.19 9509. 0.218 0.108 0.00 14267. 0.86 428.36 11955. 0.274 0.120 0.00 14510. 1.03 428.53 14442. 0.332 0.132 0.00 14754. 1.20 428.70 16971. 0.390 0.142 0.00 15000. 1.37 428.87 19542. 0.449 0.152 0.00 15248. 1.54 429.04 22156. 0.509 0.161 0.00 15498. 1.71 429.21 24812. 0.570 0.170 0.00 15749. 1.88 429.38 27511. 0.632 0.178 0.00 16002 . 2.05 429.55 30253 . 0.695 0.186 0.00 16257. 2.22 429.72 33038. 0.758 0.193 0.00 16514. 2.39 429.89 35867. 0.823 0.201 0.00 16772. 2.56 430.06 38741. 0.889 0.208 0.00 17032 . 2.72 430.22 41486. 0.952 0.214 0.00 17279. 2 .89 430.39 44445. 1.020 0.221 0.00 17542 . 3 .06 430.56 47450. 1.089 0.227 0.00 17808. 3.23 430.73 50500. 1.159 0.233 0.00 18075. 3 .40 430.90 53596. 1.230 0.240 0.00 18343 . 3 . 57 431.07 56737. 1.303 0.245 0.00 18614. 3 .74 431.24 59924. 1.376 0.251 0.00 18886. 3 . 91 431.41 63158 . 1.450 0.257 0.00 19160. 4 . 08 431.58 66439. 1.525 0.262 0.00 19436. 4 .25 431.75 69767. 1 .602 0 .268 0 .00 19714 . ('nre De�i�n. Inc. �FEDGE�V�(�OT) L�NI�: Page l� 4 .42 431.92 73142. 1 .679 0.273 0. 00 19993 . 4.59 432.09 76564. 1 .758 0.278 0.00 20274 . 4 .76 432.26 80035. 1.837 0.283 0.00 20557 . 4_93 432.43 83554. 1.918 0.288 0.00 20841 . 5.10 432.60 87121. 2 .000 0.293 0.00 21127 . 5.27 432.77 90737. 2 .083 0.298 0.00 21415 . 5.44 432.94 94402. 2 .167 0.303 0.00 21705 . 5 .61 433.11 98117. 2.252 0.307 0.00 21997 . 5.78 433.28 101881. 2 .339 0.312 0.00 22290 . 5 .95 433.45 105696. 2 .426 0.317 0.00 22585 . 6.11 433.61 109331. 2.510 0.321 0.00 22864 . 6.20 433.70 111396. 2 .557 0.323 0_00 23022 . 6.24 433.74 112319. 2 .5�8 0.327 0.00 23092 . 6.27 433.77 113012. 2.594 0.337 0.00 23145. 6.31 433.81 113939. 2 .616 0.352 0.00 23215 . 6.34 433.84 114637. 2.632 0.372 0.00 23268 . 6.38 433.88 115569. 2.653 �.398 0.00 23339. 6.41 433.91 116270. 2 .669 0.428 0.00 23392 . 6.45 433.95 117207. 2.691 0.461 0.00 23463 . 6.48 433 .98 117912. 2.707 0.494 0.00 23516. 6.65 434.15 121935. 2.799 0.542 0.00 23818 . 6.82 434 .32 126010. 2 .893 0.582 0.00 24122 . 6.99 434 .49 130136. 2 .988 0.618 0.00 24428 . 7.16 434.66 134315. 3 .083 0.650 0.00 24735 . 7.33 434.83 138547. 3.181 0.680 0 .00 25044. 7.50 435.00 142830. 3.279 0.708 0.00 25355 . 7.67 435.17 147167. 3 .378 0.734 0.00 25668 . 7.84 435.34 151558. 3 .479 0.759 0.00 25982 . 8.01 435.51 156002. 3 .581 0.783 0.00 26299. 8.18 435.68 160499. 3 .685 0.806 0.00 26617 . 8.35 435.85 165051. 3 .789 0.828 0.00 26936. 8.52 436.02 169658. 3 .895 0.849 0.00 27258 . 8.68 436.18 174043. 3 .995 0.870 0.00 27562 . 8.85 436.35 178756. 4 .104 0.890 0.00 27887 . 9.02 436.52 183525. 4.213 0.909 0.00 28213 . 9.19 436.69 188349. 4.324 0.928 0.00 28542 . 9.36 436.86 193229. 4 .436 0. 947 0.00 28872 . 9.53 437.03 198165. 4 .549 0.965 0.00 29203 . 9.70 437.20 203158. 4.664 0.983 0.00 29537 . 9.87 437.37 208208. 4.780 1.000 0.00 29872 . 10.00 437.50 212108. 4.869 1.010 0.00 30130 . 10.10 437.60 215131. 4.939 1.640 0.00 30329. 10.20 437.70 218174. 5.009 2.770 0.00 30528 . 10.30 437.80 221237. 5.079 4.240 0.00 30728 . 10.40 437.90 224320. 5 .150 5.980 0.00 30929. 10.50 438.00 227423. 5.221 7.950 0.00 31130. 10.60 438.10 230546. 5.293 10.120 0.00 31332 . 10.70 438.20 233689. 5.365 12 .490 0.00 31535 . 10.80 438.30 236853. 5.437 14.620 0.00 31738. 10.90 438.40 240037. 5.510 15.450 0.00 31941 . 11_00 438.50 243241. 5.584 16.240 0.00 32146 . I � 11.10 438.60 246466. 5.658 16.980 0.00 32351. 11.20 438.70 249711. 5 .733 17.700 0.00 32556. 11.30 438.80 252977. 5 .808 18.380 0.00 32762 . 11.40 438.90 256264. 5.883 19. 040 0.00 32969. 11.50 439.00 259571. 5.959 19.680 0.00 33176 . 11.60 439.10 262899. 6.035 20.300 0.00 33384 . 11.70 439.20 266248. 6.112 20.890 0.00 33593 . � 11.80 439.30 269618. 6.190 21.470 0.00 33802 . 11.90 439.40 273008. 6.267 22 .040 0_00 34012 . 1 � ('�n-e 1)csign. Inc. ��EDGE«OOD 1,=�`'E P:��e 15 Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 6. 90 ******* 5.38 10.37 437.87 223260. 5. 125 2 4.64 ******* 1.37 10.06 437.56 213838. 4.909 3 3 .84 ******* 1.08 10.01 437.51 212444 . 4 .877 4 2 .32 ******* 0.70 7.42 434.92 140905. 3 .235 5 2 .68 ******* 0.67 7.29 434 .79 137513 . 3.157 6 3 .94 ******* 0.37 6.34 433 .84 114560. 2 .630 7 4 .58 ******* 0.29 4.96 432.46 84184. 1.933 8 2 .16 ******* 0.25 3 .65 431.15 58159. 1.335 Route Time Series through Facility Inflow Time Series File:adev.tsf Outflow Time Series File:ardout Inflow/Outflow Analysis Peak Inflow Discharge: 6.90 CFS at 7:00 on Jan 9 in Year 8 Peak Outflow Discharge: 5.38 CFS at 9:00 on Jan 9 in Year 8 Peak Reservoir Stage: 10.37 Ft Peak Reservoir Elev: 437.87 Ft Peak Reservoir Storage: 223260. Cu-Ft . 5.125 Ac-Ft Flow Frequency Analysis Time Series File:ardout.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 1.08 3 2/09/O1 20:00 5.38 10.37 1 100.00 0.990 0.248 S 11/05/O1 3 :00 1.37 10.06 2 25.00 0.960 0.673 5 3/O1/03 7:00 1.08 10.01 3 10.00 0.900 0.289 7 8/26/04 6:00 0.695 7.42 4 5.00 0.800 0.695 4 1/05/05 15:00 0.673 7.29 5 3 .00 0.667 0.370 6 10/28/05 2:00 0.370 6.34 6 2_00 0_500 1.37 2 11/24/06 8:00 0.289 4 .96 7 1_30 0.231 5.38 1 1/09/08 9:00 0.248 3.64 8 1.10 0.091 Computed Peaks 4.04 10.29 50.00 0.980 Flow Duration from Time Series File:ardout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS � � � 0.019 30271 49.366 49.366 50.634 0.506E+00 0.058 6315 10.298 59.664 40.336 0.403E+00 0.096 6730 10.975 70.639 29.361 0 .294E+00 0.134 5973 9.741 80.380 19.620 0.196E+00 0.173 4640 7.567 87.947 12.053 0.121E+00 0.211 3024 4.932 92.878 7.122 0.712E-01 0.249 1952 3.183 96.062 3 .938 0.394E-01 0.287 1135 1.851 97.913 2.087 0.209E-01 0.326 838 1.367 99.279 0.721 0.721E-02 0.364 47 0.077 99.356 0.644 0.644E-02 0.402 26 0.042 99.398 0.602 0 .602E-02 0.441 22 0.036 99.434 0.566 0.566E-02 0.479 16 0.026 99.460 0.540 0.540E-02 0.517 47 0.077 99.537 0.463 0.463E-02 0.555 54 0.088 99.625 0 .375 0.375E-02 0.594 30 0.049 99.674 0 .326 0. 326E-02 � 0.632 33 0.054 99.728 0 .272 0 .272E-02 Core Design. Inc. ��'EI)GE��'O011 L.4nF: Page ib 0.670 40 0.065 99.793 0.207 0.207E-02 0.709 18 0.029 99.822 0.178 0.178E-02 0.747 10 0.016 99.839 0.161 0.161E-02 0.785 7 0.011 99.850 0.150 0 .150E-02 0. 824 13 0.021 99.871 0.129 0 .129E-02 0.862 11 0.018 99.889 0.111 0.111E-02 0.900 14 0.023 99.912 0_088 0 .881E-03 0.938 20 0.033 99.945 0.055 0_554E-03 0.977 15 0.024 99.969 0.031 0.310E-03 1.01 15 0.024 99.993 0.007 0.652E-04 1.05 0 0.000 99.993 0_007 0.652E-04 1.09 2 0.003 99.997 0.003 0.326E-04 1.13 0 0.000 99.997 0.003 0.326E-04 1.17 0 0.000 99.997 0.003 0.326E-04 1.21 0 0_000 99.997 0.003 0.326E-04 1.24 0 0.000 99.997 0.003 0.326E-04 ' 1.28 1 0.002 99.998 0.002 0.163E-04 1.32 0 0.000 99.998 0.002 0.163E-04 � 1.36 0 0.000 99.998 0.002 0 .163E-04 � Duration Comparison Anaylsis Base File: apredev.tsf New File: ardout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New �Change Probability Base New $Change ti 0.33a � O.10E-01 0.71E-02 -30.0 � O.10E-01 0.330 0.315 -4.4 Y 0.411 � 0.68E-02 0.59E-02 -13.8 � 0.68E-02 0.411 0.338 -17.7 0.493 � 0.46E-02 0.53E-02 14 .5 � 0.46E-02 0.493 0.518 5.1 0.575 I 0.30E-02 0.36E-02 19.5 � 0.30E-02 0.575 0.606 5.5 0.656 I 0.19E-02 0.23E-02 22.2 � 0.19E-02 0.656 0.687 4 .7 0.738 � 0_14E-02 0.17E-02 18.6 I 0.14E-02 0.738 0.802 8.7 0.820 � 0.99E-03 0.13E-02 29.5 � 0.99E-03 0.820 0_888 8_3 0.902 � 0.78E-03 0.88E-03 12.5 � 0.78E-03 0.902 0_912 1.1 0. 983 � 0.54E-03 0.26E-03 -51.5 I 0.54E-03 0.983 0.941 -4 .3 1.07 � 0 .33E-03 0.65E-04 -50.0 � 0.33E-03 1.07 0. 976 -8.4 � 1.15 � 0.20E-03 0.33E-04 -83.3 � 0.20E-03 1.15 0.996 -13 .1 � 1.23 I 0.13E-03 0.33E-04 -75.0 I 0.13E-03 1.23 1.00 -18 .2 1.31 I 0.65E-04 0.16E-04 -75.0 I 0.65E-04 1.31 1.08 -17.7 , 1.39 I 0.16E-04 O.00E+00 -100.0 I 0.16E-04 1.39 1.37 -1.7 Maximum positive excursion = 0.069 cfs ( 9.6�) V occuring at 0.720 cfs on the Base Data:apredev.tsf and at 0.789 cfs on the New Data:ardout.tsf Maximum negative excursion = 0.299 cfs {-22 . 9%) , occuring at 1.31 cfs on the Base Data:apredev.tsf I and at 1.01 cfs on the New Data:ardout.tsf l I � ��re ncsign. Inc. ��'I�:l�(:E��C)OD LA1�E Page 17 Comparing 10-year and 2-year peak flows for level 1 compliance, the 10-year and 2-year peak flows from the pond discharge are less than or equal to the pre-developed peak flows for those return periods. Flow Frequency Analysis-Basin A Pre,ieveloped Discharge Time Series File:apredev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----F low Frequency Analysis------- Flow Rate Rank Time of Peak - -:'eaks - - Rank Return Prob (CFS) (CFS) Period 1.39 2 2I09/0118:00 1.84 1 100.00 0.990 0.275 7 1/OS/0216:00 a.39 2 25.00 0.960 0.913 4 2/28/0316:00 1.18 3 10.00 0.900 0.194 8 8/26/04 1:00 C�.913 4 5.00 0.800 0.842 5 1/OS/0510:00 C.842 5 3.00 0.667 0.677 6 1/18/06 21:00 G.677 6 2.00 0.500 1.18 3 11/24/06 5:00 C.275 7 1.30 0.231 1.84 1 1/09/08 7:00 0.194 8 1.10 0.091 Computed Peaks 1.69 50.00 0.980 Flow Frequency Analysis-Basin A Pond Discharge Time Series File:ardout.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----F low Frequency Analysis------- Flow Rate Rank Time of Peak - -Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 1.08 3 2/09/0120:00 5.:38 10.37 1 100.00 0.990 0.248 8 11/OS/O1 3:00 1.;i7 10.06 2 25.00 0.960 0.673 5 3/O 1/03 7:00 1.�)8 10.01 3 10.00 0.900 0.289 7 8/26/04 6:00 0.�'i95 7.42 4 5.00 0.800 0.695 4 1/OS/0515:00 0.�.�73 7.29 5 3.00 0.667 0.370 6 10/28/OS 2:00 0.370 6.34 6 2.00 0.500 1.37 2 11/24/06 8:00 0.:?89 4.96 7 1.30 0.231 5.38 1 1/09/08 9:00 0.:�48 3.64 8 1.10 0.091 Computed Peaks 4.�)4 10.29 50.00 0.980 10 vear peak flows Predeveloped Discharge -1.180 CFS Pond Discharge -1.080 CFS 2 vear peak flows Predeveloped Discharge -0.677 CFS Pond Discharge -0.370 CFS ('nre I)esigri. Inc. 1V�{•�I)r:l�;��OOI) I ��`,I�. Pa�e IZ3 BASII� A POND BERI�4 438.5 VOLUME CALCULATIONS MWS 437.5 01045 L/D 427.5 WEDGE�VOOD BOT 419.5 SED 418.5 ELEVATIO I:�CREMENTAL TOTAL LIVE VOLUME VOLUME VOLUM � SF C�F CF CF 419.5 1,290 0 0 702 ��=�� 420A 1,517 702 0 4,116 S 422.0 2,599 _. 4,818 0 CELL#1 6,464� , 424.0 3,865 � �_ 11,282 0 9,172 426.0 5,307 20,454 0 2,752 426.5 5,699 23,205 0 0 ��'� 419.5 2,586 �"�` -� . 23,205 0 �; � 1,360 j 420.0 2,855 24,566 0 6,925 422.0 4,070 31,491 0 CELL#2 9,�38 :.', 424.0 5,468 _ � 41,029 0 12,�0� ',=r , 426.0 7,037 53,534 0 3,625 , 426.5 7,464 57,159 0 � 0 TOP OF 426.5 13,566 57,159 0 BERM TO 14,236 L/D INT. 427.5 14,906 71,395 0 0 427.5 14,906 71,395 0 ' 7,629 428.0 15,609 79,024 7,629 34,137 � 430.0 18,528 113,161 41,766 _ LNE 40,248 STORAGE 432.0 21,720 153,409 82,014 f ' 44,190 ! 434.0 22,470 197,599 126,204 51,308 '�, ;�-�, 436A � 28,838 248,907 177,512 45,489 - 437.5 31,814 � � 294,396 223,001 Stage areas measured in AutoCAD. C. BASIN A WATER QUALITY VOLU'�1E CALCULATION The �vater quality calculated using the King County Surface Water Design Manual (KCSWDM), 1998 Edition, pages 6-68 to 6-71. �'� Ve = f*(09A; + 0.25A,� + O.lOAtf+ O.lOA�,)*(R'12) ' V�'here, Vb =wetpool volume (c� f=volume factor A; =area of impervious surface(s fl ' A�g=area of till soil covered with grass (s� Atf=area of till soil covered with forest(s fl Ao=area of outwash soil covered with grass or forest R=rainfall from mean annual storm(inches) (Refer to the attached precipitation graph) Thus, I Vb =3[(0.9(489,614) +0.25(263,538))(0.041)] Vb= 62,304 cf As designed, the proposed wet pond is 8ft deep and will provide 71,395 cf of water quality volume as«�ell as lft of sediment storage. ('ore De�ign, lnc. �1'ED(:F\\OOD L.•��E Pa�e 19 D. BASI1� A E��IERGENC�' O�'ERFLO�V � Emergencv Overflow Riser � The 12"-diameter FROP tee structure will allow ��ater to be stored in the proposed ponds above the normal water surface to provide some detention storage, though this volume wasn't included in the previous calculations, since this volume is relatively insignificant compared to the volume provide by the off-site wetlands. The structure diameter was checked for adequacy per the KCSWDM Figure 5.3.4.H, Riser Inflow Curves, and the accompanying equations to verify its adequacy for conveying the developed conditions 100-year peak storm event of 6.83 cfs, as calculated with the KCRTS computer program. Qweir=9.739 DH3�2, Qweir=6.83 cfs, D = 12 inches= 1.0 foot(acting as a weir) .'. H = [Qweir/9.739 D]'�3 = [6.83 /(9.739*1.0)]z�3 =0.79 feet Therefore, the overflow riser structure can convey the 100-year design storm event with 0.79 feet of head above the top of the riser. The riser has been designed to have a top elevation of 437.50 and the minimum top of berm elevation sunounding the pond is 438.50. Therefore, approximately 0.2 feet of freeboard will be provided. Emer�y Overflow Spillway The width and depth of the emergency overflow spillway was designed based on the 1998 KCSWDM, Section 5.3.1.2. ��z L= [Qloo / (3.21Hy' )] —2.4H or 6 feet minimum Where, Qioo=peak flow for the unmitigated 100-year runoff event(6.83cfs) H =height of water over weir(0.3ft) Therefore, L = [6.83/(3.21*0.33�2)] —2.4* 03 = 12.23ft L = 13ft Cnre Dcsign. Inc. ��'F:11(:1�:��OOD I.A1H: 1':��e ZO E. BASII�` B DETENTION ROUTING CALCULATION The detention routing calculation, a continuation of the hydrologic analysis, uses KCRTS to match the pre-developed outflow to the developed outflow by providing a site-specific amount of detention. Basin A includes offsite tributary from the proposed Rutledge Property as well as some frontage improvements. The following printout shows a 25,421 cf pond in conjunction with the documented control structure will provide enough live storage (detention) to satisfy this requirement. As designed the detention pond is 4' deep and provides 27,402 cf of live storage. ('��re Design.Inc. ��EI)(:E��OOD LA�F: Pa�e 21 Basin B Retention/Detention Facility Type of Facility: Detent�on Pond Side Slope: 2 .75 H:1V Pond Bottom Length: 111.00 ft Pond Bottom Width: 33 _00 ft Pond Bottom Area: 3663 . sq. ft Top Area at 1 ft. FB: 8934 . sq. ft 0_205 acres Effective Storage Depth: 4 .50 ft Stage 0 Elevation: 419.20 ft Storage Volume: 25421. cu. ft 0_584 ac-ft Riser Head: 4 .50 ft Riser Diameter: 12 .00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.94 0.051 2 2.70 1.31 0.063 4.0 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) 0.00 419.20 0. 0. 000 0.000 0.00 3663 . 0 .01 419.21 37. 0. 001 0.002 0.00 3671. 0 .02 419.22 73. 0.002 0.003 0.00 3679. 0.03 419.23 110. 0.003 0.004 0.00 3687. 0 .04 419.24 147 . 0.003 0.005 0.00 3695. 0 .05 419.25 184 . 0.004 0.005 0.00 3703 . 0.06 419.26 221. 0.005 0.006 0. 00 3711. 0.07 419.27 258. 0.006 0.006 0.00 3719. 0 .08 419.28 296. 0 .007 0.007 0.00 3727. 0 .18 419.38 672 . 0.015 0.010 0.00 3807. 0.28 419.48 1057. 0.024 0.013 0.00 3887. 0.38 419.58 1450. 0.033 0.015 0. 00 3968. 0.48 419.68 1851. 0.042 0.017 0.00 4050. 0.58 419.78 2260. 0.052 0.018 0.00 4133 . 0.68 419.86 2677. 0.061 0.020 0.00 4216. 0.78 419.98 3103 . 0.071 0.021 0.00 4299. 0. 88 420.08 3537. 0.081 0.022 0.00 4383. 0. 98 420.18 3980. 0.091 0.024 0.00 4468. 1.08 420.26 4431. 0.102 0.025 0.00 4554. 1.18 420.38 4890. 0.112 0.026 0.00 4640. 1.28 420.48 5359. 0 .123 0.027 0.00 4726. 1.38 420.58 5836. 0 .134 0.028 0.00 4814. 1.48 420.68 6321. 0.145 0.029 0.00 4901. 1.58 420.78 6816. 0.156 0.030 0.00 4990. 1.68 420 .88 7319. 0.168 0.031 0.00 5079. 1.78 420 .96 7832. 0_160 0.032 0.00 5169. 1.88 421.08 8353. 0 .192 0.033 0.00 5259. 1. 98 421.18 8884. 0 .204 0.034 0.00 5350. 2 .08 421.28 9423. 0.216 0.034 0.00 5441. 2 . 18 421.38 9972. 0.229 0.035 0.00 5533. 2 .28 421.48 10530. 0 .242 0.036 0.00 5626. 2 .38 421.58 11097. 0 .255 0.037 0. 00 5719. 2 .48 421.68 11674 . 0 .268 0. 038 0. 00 5813 . Core Design.Inc. ��'F:l:?GE��OOD L.aNF: Pagc 2Z . 2 .58 421 .78 12260. 0 .281 0.038 0 .00 5908 . 2 .68 421.88 12855. 0.295 0.039 0.00 6003 . 2.70 421.90 12975. 0.298 0_039 0.00 6022 . 2.71 421.91 13036. 0.299 0.040 0.00 6031. 2.73 421.93 13156. 0.302 �.041 0.00 6051. 2.74 421.94 13217. 0. 303 0.043 0.00 6060 . 2.75 421.95 13278. 0. 305 0.045 0.00 6070. ' 2.77 421.97 13399. 0.308 0.049 0.00 6089. � 2.78 421.98 13460. 0.309 0.053 0.00 6099. t, 2.80 422.00 13582. 0.312 0.054 0.00 6118 . ' 2.81 422.01 13644. 0.313 0.055 0.00 6127. 2.91 422.11 14261. 0.327 0.062 0.00 6224 . 3.01 422.21 14888. 0_342 0.067 0.00 6321. 3.11 422.31 15525. 0.356 0.072 0.00 6419. 3.21 422 .41 16172. 0.371 0.076 0.00 6517. 3.31 422.51 16829. 0.386 0.080 0.00 6616. � 3.41 422.61 17495. 0.402 0.083 0.00 6715. 3.51 422.71 18172. 0.417 0.087 0.00 6816. 3.61 422.81 18859. 0.433 0.090 0.00 6916. ! 3.71 422.91 19555. 0.449 0.093 0.00 7018. ' 3.81 423.01 20262. 0.465 0.096 0.00 7120. 3. 91 423.11 20979. 0.482 0.099 0.00 7222 . 4.01 423.21 21707. 0 .498 0.101 0. 00 7325. 4.11 423 .31 22444. 0.515 0.104 0.00 7429. 4.21 423 .41 23192. 0.532 a.106 0.00 7533 . 4.31 423.51 23951. 0 .550 0.109 0.00 7638. 4.41 423.61 24720. 0 .567 0.111 0.00 7744 . 4.50 423.70 25421. 0 .584 0.113 0.00 7840 . I 4 4.60 423.80 26211. 0.602 0.424 0.00 7946. 4.70 423.90 27011. 0.620 0.989 0.00 8054 . 4.80 424.00 27821. 0.639 1.720 0.00 8162 . 4.90 424.10 28643. 0.658 2.510 0.00 8270. 5.00 424 .20 29475. 0 .677 2 .800 0.00 8379. 5. 10 424 .30 30319. 0 .696 3 .060 0.00 8489. 5.20 424 .40 31173. 0.716 3.290 0.00 8599. 5.30 424.50 32039. 0.736 3.510 0.00 8710 . 5.40 424.60 32915. 0.756 3.720 0.00 8822 . 5.50 424 .70 33803. 0 .776 3.920 0.00 8934 . , 5.60 424 .80 34702. 0.797 4.100 0.00 9047. - 5.70 424 .90 35613. 0. 818 4.280 0.00 9160. 5.80 425.00 36534. 0. 839 4.450 0.00 9274 . 5. 90 425.10 37467. 0 .860 4.620 0.00 9389. � 6.00 425.20 38412. 0.882 4.780 0.00 9504 . � 6.10 425 .30 39368. 0.904 4.930 0.00 9620. 6.20 425 .40 40336. 0. 926 5.080 0.00 9736. ; 6.30 425 .50 41315. 0. 948 5.220 0.00 9853 . 6.40 425.60 42307. 0. 971 5.360 0.00 9971. 6.50 425.70 43310. 0.994 5.500 0. 00 10089. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.83 ******* 0.69 4.65 423 .85 26551. 0.610 2 0.55 ******* 0.17 4.52 423.72 25560. 0.587 3 0.46 ******* 0.14 4 .51 423.71 25495. 0.585 4 0.27 ******* 0.08 3.28 422 .48 16635. 0.382 5 0.31 ******* 0.08 3 .27 422 .47 16578. 0.381 6 0.46 ******* 0.05 2 .77 421.97 13372. 0.307 7 0.53 ******* 0.03 2.10 421.30 9556. 0.219 8 0.25 ******* 0.03 1.56 420.76 6709. 0.154 -------------------------------- ('ore 1)esign.Inc. ��'El)C;E��O011 L��N}: Page 23 Route Time Series through Facility Inflow Time Series File:bdev_tsf ' Outflow Time Series File:brdout Inflow/Outflow Analysis Peak Inflow Discharge: 0.831 CFS at 7:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.685 CFS at 8 :00 on Jan 9 in Year 8 Peak Reservoir Stage: 4.65 Ft Peak Reservoir Elev: 423 .85 Ft ' Peak Reservoir Storage: 26581. Cu-Ft . 0.610 Ac-Ft ' Flow Frequency Analysis Time Series File:brdout.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis----- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.142 3 2/09/O1 20:00 0.685 4 .65 1 100.00 0.990 0.030 8 11/05/O1 3:00 0.168 4.52 2 25.00 0.960 0.078 5 3/O1/03 7:00 0.142 4 .51 3 10.00 0.900 0.034 7 8/26/04 7:00 0.079 3 .28 4 5.00 0.800 0.079 4 1/05/05 16:00 0.078 3.27 5 3.00 0.667 0.048 6 10/28/05 2 :00 0.048 2.77 6 2.00 0.500 0.168 2 11/24/06 8:00 0.034 2 .10 7 1.30 0.231 0.685 1 1/09/OS 8:00 0.030 1.56 8 1.10 0.091 Computed Peaks 0.513 4.62 50.00 0.980 Flow Duration from Time Series File:brdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % � � 0.003 31122 50.753 50.753 49.247 0.492E+00 0.007 5891 9.607 60.360 39.640 0.396E+00 0.012 7014 11.438 71.799 28.201 0.282E+00 0.017 5635 9.189 80.988 19.012 0.190E+00 0.021 5054 8.242 89.230 10.770 0.108E+00 0.026 2538 4.139 93.369 6.631 0.663E-01 0.031 1774 2.893 96.262 3.738 0.374E-01 0.035 1102 1.797 98.059 1.941 0.194E-01 0.040 710 1.158 99.217 0.783 0.783E-02 0.045 42 0.068 99.286 0.714 0.714E-02 0.050 21 0.034 99.320 0.680 0.680E-02 0.054 21 0.034 99.354 0.646 0.646E-02 0.059 42 0.068 99.423 0.577 0.577E-02 0.064 79 0.129 99.552 0.448 0.448E-02 0.068 45 0.073 99.625 0.375 0.375E-02 0.073 46 0.075 99.700 0.300 0.300E-02 0.078 44 0.072 99.772 0.228 0.228E-02 0. 082 21 0.034 99.806 0.194 0.194E-02 0.087 12 0.020 99.826 0.174 0.174E-02 0.092 13 0.021 99.847 0.153 0.153E-02 0.096 14 0.023 99.870 0.130 0.130E-02 0.101 16 0.026 99.896 0.104 0.104E-02 0.106 25 0.041 99.936 0.064 0.636E-03 0.110 20 0.033 99.969 0.031 0.310E-03 0 .115 14 0.023 99.992 0.008 0.815E-04 0.120 0 Q.000 99.992 0.008 0.815E-04 0.125 2 0.003 99.995 0.005 0.489E-04 0.129 0 0.000 99.995 0.005 0.459E-04 0 .134 0 0.000 99.995 0.005 0.489E-04 Ci�re Design.Inc. ��'EUGE��OOD L��;VE Page ZJ � 0.139 0 0.000 99.995 0.005 0.489E-04 0.143 2 0.003 99.998 0.002 0.163E-04 0.148 0 0.000 99.998 0.002 0 .163E-04 0.153 0 0_000 99.998 0.002 0 .163E-04 0.157 0 0_000 99.998 0.002 0.163E-04 0.162 0 0.000 99.998 0.002 0.163E-04 0.167 0 0 .000 99.998 0.0�2 0.163E-04 Duration Comparison Anaylsis Base File: bpredev.tsf New File: brdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New �Change Probability Base New $Change 0.041 ( 0.97E-02 0.75E-02 -22.5 � 0.97E-02 0.041 0.038 -6.2 y 0.051 � 0.65E-02 0.68E-02 4.0 � 0.65E-02 0.051 0.054 5.5 0.061 � 0.43E-02 0.52E-02 19.2 � 0.43E-02 0.061 0.065 6.9 0.071 � 0.28E-02 0.33E-02 17.8 � 0.28E-02 0.071 0.074 4.2 0.081 I 0.18E-02 0.20E-02 9.8 � 0.18E-02 0.081 0.085 4 .3 0.091 I 0.14E-02 0.16E-02 15.7 � 0.14E-02 0.091 0.096 4.8 0.102 � 0.96E-03 0.99E-03 3.4 � 0.96E-03 0.102 0.102 0.9 0.112 � 0.75E-03 0.21E-03 -71.7 � 0.75E-03 0.112 0.105 -6.1 0.122 I 0.52E-03 0.65E-04 -87.5 � 0.52E-03 0.122 0.107 -12.0 0.132 I 0.33E-03 0.49E-04 -85.0 � 0.33E-03 0.132 0.110 -16.5 0.142 I 0.18E-03 0.49E-04 -72.7 � 0.18E-03 0.142 0.112 -21.0 0.152 I 0.11E-03 0.16E-04 -85.7 I 0.11E-03 0.152 0.113 -25.9 0.162 � 0.65E-04 0.16E-04 -75.0 � 0.65E-04 0.162 0.124 -23.5 Maximum positive excursion = 0.004 cfs ( 8.1$) Y occuring at 0.054 cfs on the Base Data:bpredev.tsf and at 0.059 cfs on the New Data:brdout.tsf Maximum negative excursion = 0.045 cfs (-28.4�) occuring at 0.157 cfs on the Base Data:bpredev.tsf and at 0.113 cfs on the New Data:brdout.tsf ('��re Desi�;n.Inc. ��'EllGE�1�00D L:�NE Page Z� �� Comparing 10-year and 2-year peak flo��s for level 1 compliance, the 10-year and 2-year peak flows from the pond discharge are less than or equal to the pre-developed peak flows for those '' return periods. Flow Freyuency Analysis-Basin B Predeveloped Discharge Time Series File:bpredev.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - -Peaks - - Rank Return Prob (CFS) (CFS) Period 0.171 2 2/09/Ol 18:00 0.216 1 100.00 0.990 0.034 7 1/OS/0216:00 0.171 2 25.00 0.960 0.112 4 2/28/0316:00 0.143 3 10.00 0.900 0.022 8 3/03/04 2:00 0.112 4 5.00 0.800 0.103 5 1/OS/0510:00 0.103 5 3.00 0.667 0.083 6 1/18/06 21:00 0.083 6 2.00 0.500 0.143 3 11/24/06 5:00 0.034 7 1.30 0.231 0216 1 1/09/08 7:00 0.022 8 1.10 0.091 Computed Peaks 0.201 50.00 0.980 Flow Frequency Analysis-Basin B Pond Discharge Time Series File:brdout.tsf Project Location:Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.142 3 2/09/0120:00 0.685 4.65 1 100.00 0.990 0.030 8 11/O5/Ol 3:00 0.168 4.52 2 25.00 0.960 0.078 5 3/O1/03 7:00 0.142 4.51 3 10.00 0.900 0.034 7 8/26/04 7:00 0.079 3.28 4 5.00 0.800 0.079 4 1/OS/0516:00 0.078 3.27 5 3.00 0.667 0.048 6 10/28/OS 2:00 0.048 2.77 6 Z.00 0.500 0.168 2 11/24/06 8:00 0.034 2.10 7 1.30 0.231 0.685 1 1/09/08 8:00 0.030 1.56 8 1.10 0.091 Computed Peaks 0.513 4.62 50.00 0.980 10 .�}ear peak flows Predeveloped Discharge -0.143 CFS Pond Discharge -0142 CFS 2 year peak flows Predeveloped Discharge -0.083 CFS Pond Discharge -0.048 CFS ('nre 1)esign.lnc. �1 ET)(:E�1OOI) 1..-��F Page?6 BASIN B PO'�1D BERI�9 424.� VOLUME CALCULATIONS M�'VS 423.2 01045 L/D 4192 ��'EDGEWOOD BOT 415.2 SED �31=�.2 ELEVATIO INCREMENTAL TOTAL LIVE VOLUME VOLliME VOLUM SF CF CF CF 415.2 1133 _ 0 0 1,153 416.0 1749 1,153 0 DEAD 5,198 STORAGE 418.0 3449 6,351 0 �� 4,799 419.2 4549 11,150 0 0 419.2 4549 11,150 0 4,000 LIVE 420.0 5450 15,149 4,000 STORAGE 13,180 422.0 7730 28,329 17,180 10,222 423.2 9307 38,551 27,402 Stage areas measured in Cadd. F. BASIN B VVATER QUALITY VOLUME CALCULATION The water quality calculated using the King County Surface Water Design Manual (KCSWDM), 1998 Edition, pages 6-68 to 6-71. Vb=f*(0.9A; + 025A��+O.lOAtf+ O.lOAa)*(R/12) Where, Vb =wetpool volume (c fl f=volume factor , A; = area of impervious surface (s fl A�g=area of till soil covered with grass(s fl A�f=area of till soil covered with forest (s fl i A,o=area of outwash soil covered with grass or forest R=rainfall from mean annual storm (inches) (Refer to the attached precipitation graph) Thus, Vb = 3[(0.9(55,321) + 0.25(37,462))(0.041)] Vb= 7,276cf As designed, the proposed wet pond is 4ft deep and will provide 11,150cf of water quality volume as well as 1 ft of sediment storage. ('��rc Desi;�n, iiac. «'F:1)C:E��OUll 1.:11'H: Page 27 G. BASIN B EMERGENCY OVERFLOVV Emer�encv Overflo« Riser The 12"-diameter FROP tee structure will allo«� «�ater to be stored in the proposed ponds above the normal water surface to provide some detention storage, though this volume wasn't included in the previous calculations, since this volume is relatively insignificant compared to the volume provide by the off-site wetlands. The structure diameter was checked for adequacy per the KCSWDM Figure 5.3.4.H, Riser Inflow Curves, and the accompanying equations to verify its adequacy for conveying the developed conditions 100-year peak storm event of 0.79 cfs, as calculated with the KCRTS computer program. Qweir=9.739 DH3�2, Qweir= 0.79 cfs, D= 12 inches = 1.0 foot(acting as a weir) .'. H= [Qweir/9.739 D]2�3 = [0.79/(9.739*1.0)]zi3 =0.19 feet Therefore, the overflow riser structure can convey the 100-year design storm event with 0.19 feet of head above the top of the riser. The riser has been designed to have a top elevation of 423.00 and the minimum top of berm elevation surrounding the pond is 424.50. Therefore, approximately 1.3 feet of freeboard will be provided. Emergencv Overflow Spilh�vay The width and depth of the emergency overflow spillway was designed based on the 1998 KCSWDM, Section 5.3.1.2. L= [Qt�/(3.21H3�2)] -2.4H or 6 feet minimum Where, Q�� =peak flow for the unmitigated 100-year runoff event (0.79cfs) H=height of water over weir(0.3 ft) Therefore, L = [0.79/(3.21*0.33�)] - 2.4* 0.3 = 0.78ft L = 6ft ('�ire I)e�i�n. Inc. ��'EDGF;�\�OOD l.:�l�N: Page 28 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN A. PRINIARY CONVEYANCE SYSTENI The flow for the conveyance and backwater pipe sizing was attained using the rational formula as � follows: Q�oa=C* IR *A Where, Qioo=peak flow (cfs) for a 100-year storm event ' C=estimated runoff coefficient=0.51 for land cover density of 4.5 DU/AC) IR=peak rainfall intensity(inches/hour) for a 100-year storm event A=drainage subbasin area(acres) The value of IR is attained through the following formula: IR=PR*aR*�Tc��-bR) Where, , IR=peak rainfall intensity(inches/hour) for a 100-year storm event , PR=total precipitation from a 100-year, 24-hour storm event=3.95in. aR=coefficient from Table 3.2.1.B (KCSWDM)=2.61 bR=coefficient from Table 3.2.1.B (KCSWDM) =0.63 Tc=time of concentration(minutes)=10 (assumed) Therefore, IR=(3.95)*(2.61)*�1 O��-0.63) =2.41 in/hour Core Design,Inc. ��EDGE�VOOD L.�NE Page 29 l For Basin A, the subbasin area(A) is 12.72Ac, therefore: Qioo=(0.51)*(2.41)*(12.72) Qioo= 15.63 cfs For Basin B, the subbasin area(A) is 0.94 Ac, therefore: Q 1�=(0.51)*(2.41)*(0.94) Qioo= 1.16 cfs `�I � i ' , ' I i ('ore Design. Inc. ��'EDGE�VOOD LANE Page?0 3.2.1 RATION,�L ME"I'HOD I FIGURE 3.2.1.D 100-YEAR 24-HOUR ISOPLUVIALS i . 3��-� - -� *-- � �__ _-_- '�- _— —_ w _ eouurv '� . `•�.: _ ..: �wo ut .`r''.. Ot1NTY 2 • M � 3 + K. 4� ' N C : � _. . 3 ,�_ u?' :� A - �� ' �- � g — _ \•: :..::. �? ,. , _� ,, � ; _ 3 j�''_ � ,:? �� _ � S � �`� �� KA 1\4r� _ .-� _ .'�: � . � Wn�o ' 9 , .,... � J , . .. , -�} ��- f � �• o,� � 4 O �:°�. .. Y�- s,. ,� , �� 2 °� �, ��, �..�•,�. �—. � �.� "�� .` �,W"F'm _- � �•v--�a`_ `.�`- ` .x '\ ,�, "" �f - 4 t� �., ' X""..-.-�j -- . " ..a m. � .:.i.. �`� , ��._ � �.f. - � �� - � rt �' i. ,:�, a€,�q y.*� ��utbr� _ `. ��: �� _ � r �a�� ' - c w�r, :.f~ ` --�-' � �tx f'_ � p i.,.� �- �r '� % ` tS� s.-. ', ��, ,� _ ; �. % ,� '� �x� � i ��....,�;^ �a. ' �� i -�. J _ Fc`� _ 'S"Y y 1 � � �� ` � ' �� ' �Y � .._./ � \� . w� �T ' _ �� . -� �� ^ �'...' �' �-�: � �-°`� ,.,... � h� � � - �t::- � � v. . . ..c; �:�� i^ � �' . � Y� �..., t .� ,. _ ��.� . .. . . t _ _ r - . � i� ��,�� —' � - ,. , � ,-. . ..� �. .. ., :.:� . .. . : . , �� . ,_ u; an.i '�� -._ �t � .' ' ��'� . . . K .� $ � ;�YQ ..,.� .. �_ ,__.... � • �� "�_�� -� , ,,r�. � �, µ ,� ` t � �J � .,�, � i �` �� ,,, . � S.r. .-{_'. ' � - � o..r _ ,� `�1 �` _;-�M �. Y.-,s`+4 _ � [� - _ "'!� . \ b / _ �� E1 �� - �' \ ` �-'. .t ` i'.... ;�yy_ \ F' - Q) \� �!^ t -' !. � � � �� _..,._,,,_, � '� n . . , .. " � . �. ...... �. _ � �, .. �_/ ._.. . , �.; ,� . ,. _. . -=--w �^'�'d` �_, � �; G ��, _ „^'i— e � - ' ,' �.aor � �� R ��._�..�„ ____ --c a touwrv:• � .. `viE ce couwrr A `'; i WESTERN �° '�`-` �- � "�' ,�1 6.5 KING COUNTY N �o� .r -_-_',.�. .. s.o ry , ._. �, s.s � 100-Year 24-Hour � - O�• p�`� '�.,� �f....� Precipitation °`'�,y ! '-�� : , � �--.:� in Inches °�� h� ��"� hh I998 Surface Water Design Manual 9/1/98 3-17 J I (� �..c'�:��arex< at.cc�.a rto�s � OR\.4�tE: �Vedgewood Lane PREP,1REll BT: PDS I ' ' OB NI;�iBER: 01095 DES[G�STOR11t: 100 Y'EAR ENTILaNCE ENTRANCE EXIT OI;TLET IVLET APPROAC}I BEND JU\CTION PIPE P[PE MANNING'S OUTLET I\LET PIPE FLOW VELOCITY TAILW'ATER FRICTiO� HGL HEAD HEAD CONTROL CONTROL VELOCITY HEAD HEAD HEADR'ATER DEPTH FR0�1 TO FLOVF' LENGTH DIA. n ELEVATIOV ELEVAT[OIY AREA VELOCITY HEAU ELEVATIO\ LOSS ELEVATION LOSS LOSS ELEVATIO\ ELEVATION HEAD LOSS LOSS ELEVATIO\ BELOW RI!�i � CB CB (CFS) (FEET) ([ti) VALUE (FEET) (EEET) (SQ F7') (FTISEC) (FEET) (FEET) (FEET (FEE ) 'I) (FEE"1� (FEET) (FEET) (FEET) (FEET) (FEET) (FEEi') (FEET) RIM EL (EEET) BASIN A ' POND CB2 15.6 70 24 0.012 416.88 429.00 3.14 4.98 0.38 437.50 0.28 437.78 O.19 0.38 438.36 431.1� 0.36 0.3� 0.00 438.32 438.55 0.23 B 2 CB 3 15.6 122 24 OAl2 429.00 439.35 3.14 4.98 0.38 4383? 0.49 44135 O.19 0.38 441.93 �341.59 0.16 0.50 0.04 442.30 447.42 5.12 B 3 CB 4 10.1 155 24 OAl2 439.3� 440.43 3.14 3.22 0.16 442.30 0.26 442.57 0.08 0.16 442.81 442.43 0.13 0.00 OA2 442J0 44533 2.63 � B 4 CB 5 9A 159 24 OAl2 440.43 443.45 3.14 2.86 0.13 442.70 0.21 445.45 0.06 0.13 445.fr4 445.45 0.12 0.16 0.00 445.68 448.2 2.58 B 5 CB 6 8.9 30 24 OAl2 443.45 443.75 3.14 2.82 0.12 445.68 0.04 445.75 0.06 0.12 445.94 445J5 0.38 0.07 OA1 445.ti5 448.27 2.62 B 6 CB 7 8.7 41 18 0.012 44425 444.66 1.77 4.92 0.38 445.65 024 446.16 0.19 0.38 446.73 446.62 0.37 0.19 0.00 446.54 449.9 3.45 B 7 CB 8 8.6 82 18 OAl2 444.66 445.07 1.77 4.89 0.37 446.54 0.47 447AI 0.19 037 447.57 447.02 0.00 0.45 0.00 448A1 452.65 4.64 ' B 8 CB 9 8.6 284 l8 0.012 445.07 446.49 1.77 4.89 0.37 448.01 1.62 449.64 0.19 0.37 450.19 448.44 0.3� 0.48 0.00 45030 451.8 1.50 B 9 CB 10 8.6 122 18 0.012 446.49 447.10 1.77 4.89 0.37 450.30 0.70 451.00 0.19 0.37 451.56 449.05 0.3? 0.48 0.00 451.67 453.0 1.42 B l0 CB 11 8.6 51 l8 OAl2 447.10 447.36 1.77 4.89 0.37 451.67 0.29 451.96 0.19 037 452.52 44931 0.21 0.00 0.07 452.39 452.64 0.25 ' B 11 CB 12 6.4 146 IS OAl2 447.36 448.09 1.77 3.64 0.21 45239 0.46 452.85 0.10 0.21 453.16 449.59 0.16 0.00 0.02 453.02 455A 1.98 B 12 CB 13 5.6 134 18 0.012 448.09 448.76 1.77 3.17 0.16 453.02 Q.32 453.34 0.08 0.16 453.58 450.26 0.58 0.20 0.02 453.21 457.7 4.49 B 13 CB 14 4.8 30 12 0.012 449.26 454.06 0.79 6.13 0.58 453.21 0.46 455.06 0.29 0.58 455.94 456.15 0.50 0.70 0.06 456.41 457.70 1.29 B 14 CB 15 4.4 63 12 0.012 454.06 455.70 0.79 5.65 0.50 456.4] 0.82 457.24 0.25 0.50 457.98 457.63 0.40 0.45 0.05 458.08 459.2 1.18 � B 15 CB 16 4.0 140 l2 0.012 455.70 459.34 0.79 5.05 0.40 458.08 1.47 460.34 0.20 0.40 460.94 461.01 0.21 0.00 0.04 460.84 462.93 2.09 B 16 CB 17 2.9 148 12 0.012 459.34 462.30 0.79 3.66 0.21 460.84 0.81 463.30 0.10 0.21 463.61 463.49 015 0.02 0.02 463.50 466.2 2.77 B 17 CB 18 2.4 87 12 OAl2 46230 462.74 0.79 ?.11 0.15 463.50 0.35 463.85 0.08 0.15 464.08 463.74 0.12 0.15 0.02 464.12 467.95 3.83 B 18 CB 19 2.2 37 12 0.012 462.74 463.11 0.79 2J4 0.12 464.12 0.11 464.24 0.06 0.12 464.41 4fr3.11 0.08 0.05 OA2 464.40 4681 3.75 I B 19 CB 20 1.8 24 12 0.012 463.11 463.35 0.79 2.32 0.08 464.40 0.05 464.45 0.04 0.08 464.58 464.35 0.02 0.03 0.01 464.60 466.8 2.29 B 20 CB 21 0.8 114 l2 0.012 463.35 465.63 0.79 1.06 0.02 464.60 C.OS 466.63 0.01 0.02 466.66 466.63 0.00 0.00 0.00 466.66 46911 2.45 I B 3 CB 27 4.7 229 l2 0.012 430.35 445.62 0.79 6.04 0.57 442.30 3.42 446.62 0.28 0.57 447.47 447.73 0.0? 0.00 0.11 447.82 449.92 2.10 B 27 CB 28 1.0 152 12 0.012 445.62 448.20 0.79 1.22 0.02 447.8Z 0.09 449.20 0.01 0.02 449.23 449.20 0.02 0.03 0.00 449.25 452.0 2.81 B 28 CB 29 0.8 30 12 0.012 448.20 448.50 0.79 1.08 0.02 449.25 0.01 449.50 0.01 0.02 449.53 449.50 0.01 0.02 0.00 449.54 452.0 2.52 I B 29 CB 30 0.7 200 12 0.012 448.50 450.90 0.79 0.94 0.01 449.54 0.07 451.90 0.01 0.01 451.92 451.90 0.00 0.00 0.00 451.92 454.88 2.96 B 30 CB 31 0.0 96 12 0.012 450.90 453.78 0.79 0.00 0.00 451.92 0.00 454.78 0.00 0.00 454.78 454.78 0.00 0.00 0.00 454.78 457.08 2.30 B 31 CAP 0.0 112 l2 0.012 453.78 454.34 0.79 0.00 0.00 4�4.78 0.00 45534 0.00 0.00 455.34 45534 0.00 0.00 0.00 45534 CAP CAP I B 27 CB 32 3.7 30 l2 OAl2 445.62 445.92 0.79 4.71 0.34 447.82 0.27 448.09 0.17 0.34 448.61 447.47 0.34 0.14 0.00 448A1 449.9 1.51 B 32 CB 33 3.7 28 12 OAl2 445.92 446.20 0.79 4.69 0.34 448A1 0.25 448.66 0.17 034 449.17 447.74 0.13 0.14 0.03 449.21 449.92 0.71 B 33 CB 34 23 230 12 0.012 d�36.20 457.24 0.79 2.93 0.13 449.21 0.81 458.24 0.07 0.13 458.44 458.24 0.0(i 0.05 0.01 458.45 46i.0 2.63 B 34 CB 35 1.5 41 12 0.012 457.24 458.06 0.79 191 0.06 458.45 0.06 459.06 0.03 0.06 459.14 459.06 0.02 0.02 0.01 459.15 461.91 2.76 IB 35 CB 36 0.9 68 12 0.012 458.06 459.42 0.79 1.17 0.02 459.15 0.04 460.42 0.01 0.02 460.45 460.42 0.00 0.00 0.00 460.45 463.2 2.80 B 19 CB 22 0.3 97 12 0.012 463.t 1 466.41 0.79 034 0.00 464.40 U.00 467.41 0.00 0.00 467.41 467.41 0.00 0.00 0.00 467.41 469.8 2.39 I B 22 CB 23 0.1 162 12 0.012 466.41 468.84 0.79 0.16 0.00 467.41 0.00 469.84 0.00 0.00 469.84 469.84 0.00 0.00 0.00 469.84 472.4 2.56 B 11 CB 24 2.1 30 12 0.012 447.86 448.46 0.79 2.68 0.11 452.39 0.09 452.48 0.06 0.11 452.64 449.46 0.10 0.10 0.00 452.64 452. 0.00 B 24 CB 25 2.0 37 12 0.012 448.46 448.83 0.79 2.60 0.10 452.64 0.10 452.74 0.05 0.10 452.90 449.83 0.03 0.09 0.01 452.97 452.37 -0.60 ( B 25 CB 26 1.1 163 l2 0.012 448.83 462.72 0.79 136 0.03 452.97 0.12 463.72 0.01 0.03 463.76 463.72 0.00 0.00 0.00 463.77 466.5 2.73 BASIN B I POND CB 38 1.2 I5� 12 0.012 416.88 420.02 0.79 1.48 0.03 423.20 Q.14 42334 0.02 0.03 423.39 421.02 0.03 0.03 0.00 42339 423.6 0.23 B 38 CB 39 1.1 96 12 0.012 420.02 432.50 0.79 138 0.03 423.39 U-08 433.50 0.01 0.03 433.54 433.50 0.03 0.04 0.01 433.56 436.03 2.47 B 39 CB 40 1.0 60 l2 0.012 432.50 433.70 0.79 1.27 0.03 433.56 0.04 434.70 0.01 0.03 434.74 434.70 0.00 0.00 0.00 434.74 437.71 2.97 I _R 39 CR 41 0.4 117 12 0.012 432.50 446.78 0.79 0.50 0.00 433.56 0.01 447.78 0.00 0.00 447.79 447.78 0.00 0.00 0.00 447.79 450.38 2.59 I 9/12/OS CORE DESIG\T PAGE 1 B. CULVERT SIZING A culvert is proposed under Jericho Avenue N.E. in order to convey the existing seasonal creek under the road. The culvert is proposed to be an 86 foot long 24"-diameter CPEP. In order to determine the adequacy of this culvert size, the upstream tributary basin of this culvert was ', determined, as shown on the Culvert Tributary Area Exhibit that follows this section. The I tributary basin was found to be 11.0 acres in size with a 1.0 acre wetland. A buffer will be ' required around the wetland as the adjacent properties area developed, and the area of a 50' wide buffer would be 2.0 acres in addition to the wetland itself. Therefore, approximately 8.0 acres of the basin would be developable. Any development on this 8.0 acres would be required to construct stormwater detention facilities to release their stormwater at the existing peak flow ' rates. However, if these detention facilities were to overtop during a 100-year storm event, the proposed downstream culvert would receive the full, un-detained flow. This severe, worst-case scenario, was used for the sizing of this culvert. The property within this basin is zoned R-8, allowing 8 units per acre. Table 3.2.2.D of the KCSWDM was used to determine that once this property was developed, it would have an impervious coverage of approximately 60%. Therefore, the basin was modeled with the land coverage areas summarized in the following table. CULVERT TRIBUTARY BASIN AREAS �� Culvert Basin �I Area (Acres !�i Wetland 1.0 I Till- Pasture 2.0 II� Till- Grass 3.2 Impervious- 4.8 Streets, SW, Roofs, etc. Total 11.0 Flow Frequency Analysis I Time Series File:01045culv.tsf Project Location: Landsburg ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 2 .52 7 2/09/O1 3 :00 8.85 1 100.00 0.990 2 .40 8 5/06/02 7:15 5.44 2 25.00 0.960 4 .97 4 9/10/03 13 :45 5.20 3 10.00 0. 900 � 5 .20 3 8/25/04 23 :30 4.97 4 5.00 0.800 3 .38 6 9/10/OS 16:45 3 .76 5 3.00 0.667 5 .44 2 10/22/OS 16:15 3 .38 6 2.00 0.500 3 .76 5 11/21/06 8:00 2.52 7 1.30 0.231 � 8 . 85 1 1/09/08 7:30 2 .40 8 1. 10 0.091 I Computed Peaks 7. 71 50.00 0 . 980 ('��re llesi�n, lnc. ��'F:I)(;F'��OO[) L:1:�k: Page 31 01\0 :xhib �ert 1 y ArE ,9/1! 9:42 I,srb , .. y�� ./ %� 2 nJF, � � � ��' /IL iL'�i'�!` �p' � � -i.,_j��'...'�.�..�� .� ...�� .r�.` ,. .. ,f"Z. �� 3 �i � � ^,. , __ .l F .., .r��i...�►��_ �� ---� - � . :..,-�,_ � .. *= -=� *�==� �r= . �. - �"s-�� , r; � �,,,. -- , . . _�- �- -: • � .,, . _ . _____.��.-�, --�� . . � � ' _:..., �, .. � .� � , " � � �� n, 1 4 � . �+ ' �� .. . 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HEADWALL gq � 2. 2_ pi+: 600 '' / • 500 / 2 I �. . . 72 � � � I � � = 300 �y,Pj/ = 1.5 1.5 I �f. Zgp V 200 �/ W 1.5 .;.+ PLAN �2� — ? � W GROOVE END � 54 O � Q PROJECTING F- /" 1� —p � 48 W � Z . J / � ' . . .' . V � S 60 a 1.0 1.0 � j LL ej'2 N � W / O G HW SCALE ENTRANCE o � p � � 40 p TYPE � '9 •9 (3) � 36 30 (�) Squ�r��dys with Q W n.aawa�� 3 •9 Q 33 Q � (2) Groov��nd with W � � 30 M�dwall S .8 .8 (3) Groov��nd '8 27 proj�cting 10 .� .� .,. H�n,�p� t�,�y ' s To wa sals (2) or(3) proj�ct 21 $ horizontally to sql� (1), th�n 4 us�str�ipht inclin�d line through D and � acal�s, or nv�rs� as •6 .s 3 fllustrated. ,s 18 2 15 .5 .5 1.0 .5 12 2005 Surface Water Design Manual 1/24/2005 4-45 VIII. ESC ANALYSIS AND DESIGN A. BASIN A The drainage analysis for the pond was modeled using the King County Runoff Time Series software. The temporary sediment trap needs to have a minimum surface area based on the following equation(per KCSWDM, 1998 edition,pages D-28 to D-31): SA=FS(Qlo/Vs) FS (Factor of Safety) =2 (recommended value) Qlo (Dev 10-yr flow)=4.47cfs VS=0.00096ft1s(recommended value) SA= 9,313 sf ; As designed, the temporary sediment trap will pro�ide a surface area of 20,595sf at a surface elevation of 432. Core Desi�n. lnc. ��'ED(;E��'OOI) 1,AVE Pa��c 33 DE`'�'ATERING ORIFICE CALCULATION The size of the dewatering orifice was designed based on the 1998 KCS��"DM, Section D.4.5. Ao = �A��h� o.s� 1 [(0.6)(3600)T�� Where, Ao =orifice area(SF) AS=pond surface area(SF)= 20,400 h=head of water above orifice (height of riser in feet)=4.5 ft. T=dewatering time (24 hours) g=acceleration of gravity(32.2 feet/secondz) Therefore, Ao = [(20,400)(2)(4.5) o.s] \ [(0.6)(3600)(24)(32.2)0�5] Ao=0.29sf Orifice diameter, D = 13.54 �Aa =(13.54} �(0.29) D = 7.29 in ('��re Design, Inc. ��EI)GE��OQD I..��E: Page?-4 B. BASIN B � The drainage analysis for the pond «as modeled using the King County Runoff Time Series software. The temporary sediment trap needs to have a minimum surface area based on the following equation (per KCSWDM, 1998 edition,pages D-28 to D-31): SA=FS(Q�o/Vs) FS (Factor of Safety) =2 (recommended value) Qlo (Dev 10-yr flow)=0.47cfs VS=0.00096ft/s (recommended value) SA= 979 sf As designed, the temporary sediment trap will provide a surface area of 5040 sf at a surface elevation of 421. ('ore Design. Inc. ��E1)(;E��OOD L.-�NF Paoc 35 ' DEWATERYNG ORIFICE CALCULATION The size of the dewatering orifice was designed based on the 1998 KCSWDM, Section D.4.5. Ao_ �AS�2�� o.s� \ [(0.6)(3600)Tg°.s� Where, Ao = orifice area(SF) AS=pond surface area(SF) = 5,040sf h =head of water above orifice (height of riser in feet) =2.Sft T =dewatering time(24 hours) g= acceleration of gravity(32.2 feet/secondz) Therefore, Ao= [(5040)(2)(2.5) o.s] \ [(0.6)(3600)(24)(32.2)os� Aa =O.OSsf Orifice diameter, D = 13.54 �Ao = (13.54) �(0.05) D =3.03 in. (��re Design, Inc. A��H:(1l:E�1�OOp L.4NF: Fa�e 3h IX. APPENDIX ('ore Design, ]nc. ��:DGE�1'OOD I..-�\E SECITON 3.2 RUNOFF COMPUI'ATION AND ANALYSIS IviETHODS FIGURE 3.2.2.A RAINFALL REGIONS AND REGIONAL SCALE FACTORS ST 1.0/ . ST 1.0 �q p,g LA 0.9 LA 1.0 LA 1.2 ST1�� SwOwOY15M COYNi♦ .,^�'�:j jQ`ti y . . n KIMOCOUNiY Y�F `` ',� �h��.l� 4 1 .�� 4.. \ .:ic�� _ ' i�¢ yLkJs• _ Tp-Ff � i `�_ ' e •s - S ,� 1 . ��e/. -�,;{ "m"a'{° , - t �.. •.,r - a .' � � � � $`, = 1 i � ,1'� �l.' �� ~ �_ / _ ,v` . � 1 ' �-+.oAE �OW � � � .� �,� ��f.. �� .� rt_� _ � �. - r a ,� t�� -,• � e �. 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U� f � .^ �� :_ ��. �ii �� . ��\�� AkF _ � ` � �g . ua�{acrey'�� I Pu � �� . � �n \v . ,I AgC ;; Park � 1,� py � , .�M. �� Pu L•• o.�� 51S`�� .aovE \\c�\\ i i.� ��91'. � ;;�� Py � ai' � �,BeC� ' �� Z�"�d �t,o EvC �C ' ' WEDGEWOOD LANE Ur � �� I Wo eD �u .u . ♦ �>. � n _ .0 u ��_ ; � ' „• ..;;:� , (�° '�1r� . 7��,� M , g Ago �F SOILS MAP ��k ;� •�� o , . . � _,�,� -- -- — — — — — ��o e -��-- ---- =�,, ----- z6 --- -- _--- -- 2� � - - _ — - -- ------- SEPTEMBER 2005 . . . : . � - Ur � ➢ t �,� � � b- --- �--- ---•---- - ---�- - - -o BMO --- �BM,' �� ' '. I _ _ ( ❑ R s rvoir p0 C ' �A B -,_ "49Er_ � � � ,,. ; �__ __ - 2 CORE JOB NO. 01045 � ■ Sa T� m Z � � � I � �C a ` AgD SCALL' . 1��=20�� i I j Pu m Sk . AgC AgD . - ` � AkF � � � R � w� i „ M_ . �G n� . • ._ \ i // r� , � a a� !F \`,, �. /�l� � i 3.2_2 KCRTS/RUNOFF FILES METHOD—GENERATING TIME SERIES ' TABLE 3.??B EQUIVALENCE BETWEEN SCS SQIL TYPES AND KCRTS SOIL TYPES SCS Soil Type SCS KCRTS Soil Notes Hydrologic Group Soil Group � Alderwood (AgB,AgC,AgD) C Till Arents, Alderwood Material (Am6,AmC) C Till Arents, Everett Material (An) B Outwash 1 Beausite (BeC, BeD, BeF7 . C Till 2 Bellingham (Bh) D Till 3 Briscot (Br) D Till 3 Buckley (Bu) D Till 4 Earlmont(Ea) D Till 3 Edgewick (Ed) C Till 3 Everett (EvB, EvC, EvD, EwC) A/B Outwash 1 lndianola (InC, InA, InD) A Outwash 1 Kitsap (KpB, KpC, KpD) C Till Klaus (KsC) C Outwash y Neifton (NeC) A Outwash 1 Newberg (Ng) B Till 3 Nooksack (Nk) C Till 3 Norma (No) D Till 3 Orcas (Or) D Wetland Oridia (Os) D Till 3 Ovall (OvC, OvD, OvF) C Till 2 Pilchuck(Pc) C Till 3 ' Puget (Pu) D Till 3 ', Puyallup (Py) B Till 3 Ragnar(RaC, RaD, RaC, RaE) B Ou'twash 1 Renton (Re) D Till 3 I Salal (Sa) C Till 3 Sammamish (Sh) D Till 3 Seattle (Sk) D Wetland Shalcar(Sm) D Till 3 Si (Sn) C Till 3 Snohomish (So, Sr) D Till 3 Sultan (Su) C Till 3 Tukwila (Tu) D Till 3 Woodinville (Wo) D Till 3 Notes: 1. Where outwash soils are saturated or underlain at shallow depth (<5 feet) by glacial till,they should be treated as till soils. 2. These are bedrock soils, but calibration of NSPF by King County DNR shows bedrock soils to have similar hydrologic response to till soils. 3. These are alluvial soils,some of which are underlain by glaaal till or have a seasonally high water table. In the absence of detailed study,these soils should be treated as till soils. . 4. Buckley soits are formed on the low-permeability Osceola mudflow. Hydrologic response is assumed to be similar to that of till soiis. 1998 Surface luater Design Manual 9/1/98 3-25 Permeability is moderately rapid in the surface Arents, Alderwood Material layer and subsoil and very slow in the substratum. Roots penetrate easily to the consolidated substra- tum where they tend to mat on the surface. Some Arents, Alderwood material consists of Alde n•roo� roots enter the substratum through cracks. Water soils that have been so disturbed through urban- moves on top of the substratum in winter. Available ization that they no longer can be classified with water capacity is lox�. Runoff is slow to medium, the Alderwood series, These soils, however, have and the hazard of erosion is moderate. many similar features. The upper part of the soil, This soil is used for timber, pasture, berries, to a depth of 20 to 40 inches, is brown to dark- and row crops, and for urban development. Capability brown gravelly sandy loam. Below this is a grayish unit IVe-2; woodland group 3d1. � brown, consolidated and impervious substratum. .�( Alderwood gra�elly sandy loam, 0 to 6 percent � Slopes generally range from 0 to 15 percent. (T1 slopes (AgB) .--This soil is nearly level and These soils are used for urban development. undulating. It is similar to Aldezwood gravelly sandy loam, 6 to 15 percent slopes, but in places ' its surface layer is 2 to 3 inches thicker. Areas ATents, Alderwood material, 0 to 6 percent slope are irregular in shape and range from 10 acres to ��B� •--In many areas this soil is level, as a slightly more than 600 acres in size. result of shaping during construction for urban facilities. Areas are rectangular in shape and Some areas are as much as 15 percent included range from 5 acres to about 400 acres in size. Norma, Bellingham, Tukwila, and Shalcar soils, all of which are poorly drained; and some areas in the Representative profile of Arents, Aiderwood vicinity of Enumclaw are as much as 10 percent material, 0 to 6 percent slopes, in an urban area, Buckley soils. 1,300 feet west and 350 feet south of the northeast Runoff is slow, and the erosion hazard is corner of sec. 23, T. 25 N., R. 5 E. : slight. 0 to 26 inches, dark-brown (lOYR 4/3) gravelly This Alderwood soil is used for timber, pasture, berries, and row crops, and for urban development. sandy loam, pale brown (lOYR 6/3) dry; Capability unit IVe-2; woodland group 3d2. massive; slightly hard, very friable, non- . sticky, nonplastic; many roots; medium acid; � Alderi.00d gravelly sandy loam, 15 to 30 percent abrupt, smooth boundary. 23 to 29 inches II slopes (AgD) .--Depth to the substratum in this soil thick. varies within short distances, but is commonly 26 to 60 inches, grayish-brown (2.5Y S/2) weakly about 4U inches. Areas are elongated and range consolidated to strongly consolidated glacial from 7 to about 250 acres in size. till, light brownish gray (2.5Y 6/2) dry; Soils included with this soil in mapping make common, medium, prominent mottles of yellowis up no more than 30 percent of the total acreage. brown (lOYR S/6) moist; massive; no roots; Some areas are up to 25 percent Everett soils that medium acid. Many feet thick. have slopes of 15 to 30 percent, and some areas are up to 2 percent Bellingham, Norma, and Seattle soils, The upper, Very friable part of the soil extends which are in depressions. Some areas, .especially to a depth of 20 to 40 inches and ranges from dark on Squak Mountain, in Newcastle Hills, and north of grayish brown to dark yellowish brown. Tiger Mountain, are 25 percent Beausite and Ovall � Some areas are up to 30 percent included soils soils. Beausite soils are underlain by sandstone, that are similar to this soil material, but either and Ovall soils by andesite. shallower or deeper over the compact substratum; Runoff is medium, and the erosion hazard is and some areas are 5 to 10 percent very gra�relly severe. The slippage potential is moderate. Everett soils and sandy Indianola soils. This Alderwood soil is used mostly for timber. This Arents, Alderwood soil is moderately weil Some areas on the lower parts of slopes are used drained. Permeability in the upper, disturbed soil for pasture. Capability unit VIe-2; woodland group material is moderately rapid to moderately slow, 3d1. � depending on its compaction during construction. The substratum is very slowly permeable. Roots ' Alderwood and Kitsap soils, very steep (AkF) .-- penetrate to and tend to mat on the surfaee of the This mapping unit is about 50 percent Alderwood gravelly sandy loam and 25 percent Kitsap silt consolidated substratum. Some roots enter the substratim through cracks. Water moves on top of loam. Slopes are 25 to 70 percent. Distribution the substratwn in winter. Available water capacity of the soils varies greatly within short distances. is low. Runoff is slow, and the erosion hazard is About 15 percent of some mappsd areas is an slight. included, unnamed, very deep," moderately coarse This soil is used for urban development. Ca- textured soil; and about 10 percent of some areas Pability unit IVe-2; woodland group 3d2. is a very deep, coarse-textured Indianola soil. Drainage"and permeability vary. Runoff is rapid , to very rapid, and the erosion hazard is severe to Arents, Alderwood material, 6 to 15 percent very. severe. The slippage potential is severe. slopes (AmC) .--This soil has convex slopes. Areas These soils are used for timber. Capability are rectangular in shape and range from 10 acres to unit VIIe-1; woodland group 2d1. about 450 acres in size. 10 WEDGEWOOD LANE - Maximum Impervious Area per Lot Core Design Project No. 01045 MAX. IMPERVIOUS AREA ADD'L. TOTAL LOT LOT AREA (S.F., includes house, DRIVEWAY IMPERVIOUS TO LOT NO. (NET S.F.) driveway and patio) (S.F.) POND {S.F.) DIVISION 1 1 4,534 2,600 2,600 ' 2 4,607 2,600 2,600 3 4,719 2,600 2,600 4 5,559 2,600 2,600 5 4,802 2,600 2,600 6 4,802 2,600 2,600 7 12,243 3,050 3,300 6,350 ' 8 7,186 2,850 2,850 9 5,058 2,850 2,850 , 10 6,046 2,850 700 3,550 11 4,881 2,850 2,850 12 4,824 2,850 2,850 13 5,383 2,850 2,850 14 5,464 2,850 2,850 , 15 6,649 2,850 2,300 5,150 ' 16 4,500 2,600 2,600 ' 17 4,500 2,600 2,600 � 18 5,060 2,600 2,600 DIVISION 2 1 5,975 3,050 3,050 2 6,520 2,850 1,200 4,050 3 4,831 2,600 2,600 ' 4 4,500 2,600 2,600 ' 5 4,500 2,600 2,600 I 6 4,500 2,600 2,600 �I 7 4,500 2,600 2,600 �'I 8 4,500 2,600 2,600 ! 9 4,518 2,600 2,600 10 5,385 2,600 2,600 I 11 5,784 2,600 900 3,500 I 12 8,700 2,850 2,850 ' 13 6,890 3,050 3,050 14 6,663 3,050 3,050 15 7,154 3,050 3,050 16* 7,058 3,050 1,525 i ' 17* 6,996 3,050 1,525 ' 18* 4,950 3,050 1,525 I 19 6,647 2,600 2,600 20 4,500 2,600 2,600 21 4,500 2,600 2,600 22 4,500 2,600 2,600 ' 23 4,500 2,600 2,600 ' 24 4,518 2,600 2,600 25 4,793 2,600 2,600 26 5,784 2,600 1,720 4,320 27 4,501 2,600 2,600 28 5,383 2,600 2,600 29 5,001 2,600 2,600 30 4,927 2,600 2,600 31 6,230 2,600 2,600 32 4,697 2,600 2,600 33 4,516 2,600 2,600 34 4,516 2,600 2,600 35 5,171 2,600 2,600 36 6,050 2,850 2,850 37 6,716 2,850 2,850 38 4,971 2,850 2,850 39 4,804 2,850 2,850 40 4,804 2,850 2,850 41 4,888 2,850 2,850 42 5,270 2,600 2,600 43 5,039 2,850 2,850 44 5,039 2,850 2,850 45 5,429 2,600 2,600 DIVISION 3 1* 13,652 3,050 Z,400 '2',725 2" , 8,301 3,050 1,525 3 5,451 2,850 2.850 4 5,304 2,850 2,850 5 5,406 2,850 2,850 6 5,003 2,600 2,600 7 5,613 2,850 2,850 8 5,702 2,850 2,850 9 5,804 2,850 2,850 10 5,906 2,850 2,850 11 6,007 2,850 2,850 12 5,314 2,850 2,850 13 4,500 2,600 2,600 14 7,453 3,050 3,050 15 5,500 2,600 2,600 16 5,500 2,600 2,600 17 6,555 2,600 2,600 30 5,000 2,600 2,600 31 5,000 2,600 2,600 32 5,000 2,600 2,600 33 5,003 2,600 2,600 34 5,003 2,600 2,600 35 4,503 2,600 2,600 36* 4,503 2,600 1,300 37* 5,003 2,600 1,300 38* 5,003 2,600 1,300 39* 5,003 2,600 1,300 40'` 4,876 2,600 1,300 Total Lots: 91 Total: 245,495 DIVISION 3 18' 9,081 3,050 1,525 19 6,627 3,050 3,050 20* 9,630 3,050 1,525 21* 9,400 3,050 2,400 2,725 22 5,497 2,600 2,600 23 5,650 2,600 2,600 24 7,170 2,600 2,600 25 6,082 2,600 2,600 26 5,000 2,600 2,600 27* 5,500 2,850 1,425 28* 5,400 2,850 1,425 29' 5,000 2,600 1,300 Total Lots: 28 Total: 25,975 * Roof and footing drains from this lot will discharge to the wetland and therefore will be modeled as 50% impervious surface/50%grass in the sizing of the detention ponds, in accordance with Table 5.2.2.A"Fiow Control BMP Facility Sizing Credits" in the 2005 KCSWDM.