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Home My WebLink About03280 - Technical Information Report - Preliminary�----- � .1AECER ��IGINEERIIti[C 9419 S. 204 Pu►CE - KENT, WASH[NGTON 9803� �I • PHONE (253) 850-0934 Fau (253) 850-0 i 55 , 0 ll� July 18, 2004 � � � PRELIMINARY DRAINAGE REPORT MAGn'USON 3 LOT SHORT PLAT 12151VI4NROE AVE. NE 'i PREPARED FOR: O��ner: Jim Magnuscn 523 Union Ave. NE Renton, Wa. 98059 � (425) 254-0687 � ��S �• d�� r�� ' �J t.��`.�' � �� 5.Vf � +� `N' � ��::�sr� '�±�� `� ��`., r � PREPARED BY: �µ°-�..�b��.�, ' ��"`�' P��.c._�,�. Qs__y James J. Jaeger, P.E. �.��i-�� DEVELOPMENT PLANIVING C�TI'OF RENTON DEC 1 6 2004 RECEIVED .�'3280 i . I. OVERVIEW The proposed project is a 3 lot short plat located along the west side of Monroe Ave. NE, between NE 12m St. and Sunset Blvd. The site oddress is 1215 Monroe Ave. NE. The existing lot is a 0.51 ocre parcel that has an existing house with an attached garage. The proposed shorf plat would I divide the existing lot to create 2 additional single family residential lots. The existing lofi is generalfy covered with lawn and typiccrl residential londscaping. The lot slopes down to the west, down and away from Monroe Ave. NE. at an average slope of 11%. The slope across the properfy is foirly constant with o maximum slope of 20�. There are a few significant trees on the property, which are shown on the plan. The existing frontage road, Monroe Ave. NE, is an aspholt paved road with gravel shoulders. There are no curbs, gutters or sidewalks. The applicanfi will submit a request to the public works committee that any requmement for curb, gutter and sidewalk improvements be waived. The access to the proposed lots wil! be from a private road located in the center of the short plafi. The City has recommended fihat all three lofs gain access from this private road/driveway. The existing lot has a lon�}. gravel driveway from Monroe Ave. NE to the back of the house and a�.�, a pull-through driveway in front of the house. There are no drainage improvements on the existing site. Addifiionafly there is no drainage system within the Monroe Ave. NE. The proposed deveioped sifie will utilize on-sifie infiltration for the individual lots and fc. the private road. There is an existing sanitary sewer main along the frontage of the site. Thi� sewer main is approx. 15' deep. The house on {ot 2 will need to be rais�� several feet to allow gravity side sewer flow. There is a 4" water main i Monroe Ave NE. This water main will be tapped for 2 new services witf the meters being placed near #he private road entrance. A new 8" w main and fire hydranfi will be consfiructed along the wesfi shoulder of Monroe Ave. NE., for approx. 130' north of NE 12ih St. This will allow the new hydrant to service the lots within this short plat. � � . _ _ _. . . 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Project Owner lYY1 r� �1 Project Name �1 ��YtV.SiN� S�.c�r'�"� 1'fa.t'�' � Address Z 2 N''- Localion Phone�42�5�=0(�'e7 �' � ' Township � Projeci Engineer �d7t.N�eS .�0.Q,�`--'r Range �— Section i Company 4�-�-�' � +'� �r. � ,� Project Size ��.a I AC i Address Phone. � � r� �- . 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King County Building and �and Development Divfston �� TECHNICAL INFORMATION REPORT (TIR} WORKSHEET , I � a . • �;ia l��I • REFERENCE L(MITATIOWSITE CONSTRAII�tT � Ch.4-Downstream Analysis �� ,��Ct,�Y\b-Q-2- � 1 S C�T�C4-��. � GCT(��f l Q�"�cN\ t�O�Y�"� � � � � 0 AdditionaJ Sheels Attatched � -�_• • �� i� MIMF�fUM ESC REQUTAEM,ct�tTS MINlMU�,�ESC REQUIRE�,�Et�ITS + DURING CONSTRUCTION FOIlOWING CONSTRUCTION �. 0 Sedimenta:ion Faaliiies �" St2bil¢e Exposed Surface � 0 Stabilized Construction Entrance f,� Remove and Reslore Temporary ESC Faa(ities � �Perimeter Runoff Control � Clean and Remove All Silt and Debris � 0 Clearing and Grading Resirictions 0 Ensure Operation oi Permanent Faalities , � Cover Prac;ices � Rag Limits of NGPES , Cor,struciicn Sequence 0 Oiher i � Other � « �, � Grass Lired C��znnel �� Tank �Ir,il;ra;ion F.�thod of Analysis � Pi�.�e System � Vault C] Depression � �l� }—i � O�r Channel J Enercy Diss�tor 0 Flow Disaersal Compensa:;on;T.li;iga;ion L� Dry Pond �J �^Jeila�d O �'�a�ver ot Eliminated Site Siorage � �ti'et Pond � Stream I� Regiona!Detention � �-�Q-- ' � ,I I r i Enef Descrip'ion c;System O�ration V ��' UC�� W t ' t�l ► . � ��Y �� ; t' � i �t V l C7'v a-� 10�1 1� t (i—rt�=�'i -'h FaciGty Rela'ed S:te Limitations � Addil;onal Shee?s Attatched Fefe;ence Fa�l:;y Lini,aticn , . •",:i�" - ;i�',�, �„ �y-�' Y? �a ��1 � _��_' � �v� '. � ' •� - —� `� :«i ' �i��=��. I Drainage Easement � � Cast in Place Vault � Oi�er �Access Easement � Ret�ining G'dali � Native Growth Protection E2sement � Rockery>4'High I � Tract ' , � S;ruclur�J on S:eep S1oF� '� O,��er I — --- _ -- ----- __ -- _ _-- --- i r * _. � �.�_r:� .� _� �i� 1-� � ,� -�'� •. '� r I� � ��`�"`" �,�:'�y'r^+*- �':'� .ej;_�.,��' �: �?"� ��' � �s.x`�-� I i or a eivil engineer undc� my supervision havo visited ihe site. �C,u�; .� � ; site condiUons as observed were incorporated into this woricsheet and the ��-,,,(O� ; atiatchments. To the best cf my knov.fedge the informa;ion provided � � ' � � �� Lhere is accurate. ��•�• ' II. PRELIMINARY CONDITiONS CORE DRAINAGE REQUIREMENTS 1. Discharge a# Natural Location: Ths site will use infiltration for all of the new impervious surfoces. There will not be any drainage leaving the site. 2. Off-Site Analysis: An upstream and downstream drainage analysis has been performed and is detailed in section III of this report. 3. Runoff Control: This project is exempt irom peak rate runoff control because the 100 year peak developed runoff is less than 0.5 CFS greater than the peak pre- developed runoff rate. The actval difference is 0.09 CFS. 4. Conveyance System: There are no existing drainage improvements on the site and none are proposed for this project. The downspouts for the new houses will be piped to individual infiltration systems within the lots. 5. Erosion and Sedimentation Control Plan: An erosion control plan will be prepared for this site. No significant grading is being proposed for this project. The construction for the new private road wi(I require some fill to be placed at the end of the road for a driveway connec#ion to lot 2. 6. Maintenance and Operation: Any necessary maintenance wil! be the responsibility of the individual home owner. There are no proposed public improvements. 7. Bonds and Liability: All required bonds and insurance wil! be provided prior to the pre- construction meeting. The bonding amount will be determined during p�an preparation and reviewed by the City. SPECIAL DRAINAGE REQUIREMENTS There are 12 special drainage req�irements that may apply to any project. ln this case, none of them are applicable or triggered. CITY OF RENTON MEMORANDUM DATE: October 13, 2003 TO: Kristina Catlin FROM: Ameta Henninger X7298 �� SUBJECT: MAGNUSON 3 LOTS SHORT PLAT PREAPPLICATION 03- 108 . 1215 MONROE AVE NE rOTE ON PRELIlI�'ARY RE«W C011Il�fE;�TS CONTAII�`ED IN THIS REPORT: The folloR-ing comments on de��elopment and permitting issues are based on the pre- application submittals made to the City of Renton by the applicant The applicant is cautioned that information contained in this summary may be subject to modification and,'or concurrence by official decision makers(e.g. Hearing Examiner,Boards of Adjustment,Board � of Public Works and City Council). Re�-iew comments may also need to be re�-ised based on site plannin� and other desi�❑ chan�es required bv the City or made b}•the applicant. I have reviewed the preapplication for this 3 lot shert plat for town homes located in Section 4-23-5 and have the follo�ving comments: WATER: • This site is located in the 565 Water Pressure Zone. The static pressure at the street is approximately 65 psi. Pressure reducing valves are required to be installed on domestic water meters exceeding 75 psi. • All plats are required by City code to provide a fire hydrant with a minimum fire flo�v requirement of 1,000 GPPJI within 300 feet of any proposed single-family structure. If the proposed single-family structures exceed 3,600 square feet, the minimum fire flow increases to 1,500 GPM and requires two hydrants within 300 feet of the structure. This distance is measured along a travel route. Additional fire hydrants will be required as a part of this project to meet this criteria. • There is an existing 4 inch water main located in Monroe Ave NE. • In order to serve this new short plat the applicant shall extend a new 8" water main and new fire hydrant in Monroe Ave NE to get the fire hydrant within 300 feet to meet the above criteria. The applicanYs engineer will need to evaluate the differences betvreen extending a nevr main from NE 12th St or extending a new main from the north to the s;te to meet the dist�nce criteria. Mag�x+son ShPI Preapplication � ' - 1Z15 Monroe Ave ME . This site is located in the Aquifer Protection Zone 2. . Water System Development Charges of $1105 per each new unit wili be required for this project (the Mutti-family unit rate is �665). The Development Charges are collected as part of the construction permit. SANITARY SEWER: • This project is located in the Aquifer Protection Zone 2. • A sanitary sewer main extension is not required for this project. • There is an existing 8' sanitary sewer main located in Monroe Ave NE. See City of Renton sanitary sewer drawing S0045 for detailed engineering plans. • The existing sidesewer may need to be relocated and or upsized to meet current City code. • The City does not have any side sewer drawings or sketches for this address. �I • Individual side sewers need to be installed to serve the new individual lots. Dual sidesewers are not allowed. � The applicant is responsible for securing all necessary private sanitary sewer easements prior to the recording of the short plat. • System Development Charges are required. If the applicant proposes to construct one townhouse on one lot the System Development Charge is �760 for the lot. The key to the SDC fee is the number of units. If the applicant proposes rivo units on one lot the SDC is assessed at the Multi-family rate, which is 5455 per unit. The Development Charges are collected as part of the construction permit. STORM DRAfNAGE: • There are storm facilities fo the north in Monroe Ave NE. • A storm drainage report shall be submitted. A storm drainage content list is attached. The storm drainage report for fhe site and both street frontages shall be addressed in compliance with the 1990 King County Surface Water drainage manual. • The Surface Water Sysfem Development Charges of �525 per each new lot applies to the proposed project. The Development Charges are collected as part of the construction permit. STREET IMPROVEMENTS: • Per City of Renton code projects that are 2-4 residential lots in size are required to install half pavement�vidth per standard plus a minimum 10 feet along the full frontage cf tne parcel being developed. 11sg�wson ShPI Preapplication _ ' 1Z15 Monroe Ave NE • The project shall install also install curb, gutter and sidewalk on the project side. • Street lighting is not required to be installed for a 3 lot short plat. • A shared driveway is permitted for access to two lots. Per Fire comments the access does need to be paved a minimum of 20 feet in width. • All new electrical, phone and cable services to the plat must be undergrounded. Construction of these franchise utilities must be inspected and approved by a Cit�+ of Renton public works inspector prior to recording of the short plat. • The single family rate for the Traffic Mitigation Fee is approximatefy $750 per each new lot. This fee shall be paid prior to the recording of the short plat. AQUIFER: • The site is located in Aquifer Protection Zone 2 and may be subject to additional requirements per City code. Constructed secondary containment may be required if more than 20 gallons of regulated hazardous materials will be present at the new facility (RMC 4-3-050H2d(i)). A fill source statement (RMC 4-4-060L4) is required if more than 100 cubic yards of fill material will be imported to the project site. Construction Activity Standards (RMC 4-4-03007) shall be followed if during construction, more than 20 gallons of hazardous materials will be stored on site or vehicles will be fueled on site. Surface Water Management Standards (RMC 4-G-030E2 and 3)—Biofilters, stormwater conveyance, and water quality ponds may require a groundwater protection liner. Impervious surfaces shall be provided for areas subject to vehicular use or storage of chemicals. This is not intended to be a complete list of the APA requirements nor does this information substitute for the full ordinance, it is only intended to guide the applicant to the City of Renton code book. GENERAL: I • Submit a conceptual utility plan vrith the formal application. If you have any questions call me at 430-7298. • All projects need to be tied to a minimum of two of the City of Renton current Horizontal and Vertical Control network. • All required utility, drainage and street improvements will require separate plan submittals prepared according to City of Renton drafting standards by a licensed Civil Engineer. • Permit application must include an itemized cost estimate for these improvements. The fee for review and inspection of these improvements is 5% of the first $100,000 of the estimated construction costs; 4% of anything over $100,000 but less than 5200,000, and 3% of anything over $200,000. Half of the fee must be paid upon application for building and construction permits, and the remainder when the permits are issued. There may be additional fees for water service related expenses. See Dratting Standards. cir�r oF RErvTON PlanninglBuilding/Public Works MEMORANDUM DATE: October 23, 2003 TO: Pre-Appfication Fife No. 03-108 FROM: Kristina Catlin, Associate Planner, x7270 SUBJECT: Magnuson Short Plat General: We have completed a preliminary review of the pre-application for the above- referenced development proposal. The follotiving comments on development and permitting issues are based on the pre-application submittals made to the City of Renton by the applicant and the codes in effect on the date of review. The applicant is cautioned that information contained in this summary may be subject to modification and/or concurrence by official decision-makers (e.g., Hearing Examiner, Zoning Administrator, Board of Adjustment, Board of Public Works, and City Council). Revie�v comments may also need to be revised based on site planning and other design changes required by City staff or made by the applicant. The applicant is encouraged fo review all applicable sections of the Renton Municipal Code. The Development Regulations are available for purchase for �50.00 plus tax, from the Finance Division on the first floor of City Hall. Project Proposal: The subject property is addressed as 1215 Monroe Avenue NE. The proposal is to subdivide an approximately 22,350 square foot lot (approx. 0.51- acre) into 3 lots. The applicant is proposing to build rivo townhouses on the proposed additional lots (Lots 1 8� 2). The site is currently developed with an approximately 910 square foot single-family house. As proposed, Lots 1 and 3 have street frontage on Monroe Avenue NE, Lot 2 is served by a 20-foot wide private access easement. Zoning/Density Requirements: The subject property is located within the Residential - I, 10 dwelling units per acre (R-10) zoning designation. The R-10 zone allows attached ' d��ellings, limited to no more than four (4) attached dwellings per building. The minimum density in the R-10 zone is 7 units per net acre. The maximum density in the R-10 zone for developmenfs that include attached dwellings is 10 units per net acre. In order to calculate net density, private access easements serving three or more units, as vrell as critical areas must be deducted from the gross area of the property. The followinq density calculations assume no deductions for protected (>40%) slopes on fhe sife. The density of the proposed short plat would depend upon the number of units planned far the additional lots. Three units (i.e. one single-family home on each lot) results in a density of 5.88 du/ac, which is less than the minimum density required. A total of four units would result in a density of 7.84 du/ac (4 dwelling units/0.51 acre = 7.84 du/ac). A total of five units would result in a density of 9.80 du/ac (5 dwelling unitsl0.51 acre = 9.80 du/ac). Six,units results in a density of 11,7 dulac, which exceeds the maximum density allo�ved. Due to density limitations, the subject properfy v✓ould most fikefy suppor� a minimum of 4 and a maximum of 5 dwelling units. " Magnuson Short Plat Pre-Appiicatia.,��eeting October 23,2003 • Page 2 of 3 Development Standards: The R-10 zone permits both attached and detached dwellings. The R-10 zone permits a maximum of one residential building with a maximum of 4 residential units per lot. The R-10 zone allows a maximum of two 720 square foot detached accessory structures, or one 1,000 square foot detached accessory structure. Minimum Lot Size, Width and Depth —A copy of the R-10 development standards (including lot size requirements) are included with this memo. The minimum lot size requirements of the R-10 zone vary based on the proposed unit type. However, the applicant has noted that a restrictive covenant exists on the subject property that precludes lots smailer than 6,000 square feet. As proposed, Lot 1 is 6,001 square feet; Lot 2 is 6,023 square feet; Lot 3 is 10,307 square feet. As proposed, all three lofs meet the minimum lot size requirements of the R-10 zone as well as the restrictive covenant requiring a minimum lot size of 6,000 square feet. The minimum lot width for detached dwellings is 30 feet for interior lots; the minimum width for townhouses is 20 feet; the minimum lot width for flats is 50 feet. The minimum lot depth for all lots in the R-10 zone is 55 feet. As proposed, Lot 1 is approximately 75 feet wide and 80 feet deep. Lot 2 is proposed to be approximately 87 feet wide and 69 feet deep. Lot 3 is proposed to be approximately 62 feet �vide at the narrowest portion and approximately 149 feet deep. As proposed, the lots meet the minimum lot width and depth requirements, regardless of the unit type the applicant �vishes to build. Buildinq Standards —The R-10 zone allo�vs a maximum building coverage of 70% for detached units and a maximum of 50°/o for flafs or totivnhouses. In addition, the R-10 zone limits the impervious surface area on a lot to a maximum of 75% for detached units and a maximum of 60°/a for flats or townhouses. If the single-family structure remains on Lot 3, it �vill comply �a�ith the building and impervious surface requirements of the zone. Compliance with building and impervious surface restrictions �vould be verified for Lots 1 and 2 at the time of building permit submittal. Building height is restricted to 30 feet and 2-stories. Detached accessory structures must remain below a height of 15 feet and one-story �vith a gross floor area th�t is less than the primary structure. Accessory structures are included in lot coverage calculations. Setbacks — Setbacks are measured from the pro�erty lines to the nearest point of the structure. The required setbacks for inferior lots in the R-10 zone are 20 feet in the front, 15 feet in the rear, and 5 feet on the sides. The existing d�velling appears to comply with the setbacks of the zone, based on the location of the proposed ne�v lot lines. Any future development on Lots 1 and 2 would be required to meet setbacks. Access — In order to create three separate lots on the subject property, fhe applicant must creafe an access easement for Lot 2 across Lot 1. The easement must be a minimum of 20 feet wide with at least 12 feet paved. As a condition of short plat approval, staff will likely recommend that all three lots be required to access from the proposed private access easement. Parking: Each lot is required fo accommodate off sfreet parking for a minimum of two vehicles for each detached d�velling unit. Aftached dwelling units with surface parking require a 1.75 parking spaces per d�velling units �vhere tandem spaces are not provided and/or 2.25 parking paces per d�,�elling unit where tandem parking is provided. !.":�gnus�n Shor,PI:,;(?-Ict R-10}-doc�� Magnuson ShoA Plat Pre-Applicatio�,..�eeting October 23,2003 ' Page 3 of 3 . Critical Areas: The subject site is located in the Aquifer Protection Zone 2. The subject site contains sensitive (25%-40%) slopes along the western property boundary and is within 50 feet of a protected (40%+) slope. According to Renton Municipal Code (RMC) Section 4-3-050.6.4b.1, the boundaries of a regulated steep, sensitive, or protected slope are in the location identified on the City of Renton's Steep Slope Atlas. A copy of the Steep Slope Atlas page applicable to the subject property is enclosed. RMC Section 4-3-050.J.2 requires a geotechnical study by a qualified professional ' whenever a proposed development site contains or is within fifty feet (50') of a geologic hazard (i.e. sensitive or protected slopes). Therefore, a geotechnical � study will be required for the proposed short plat. Environmental Review: Short plats that have critical as defined by the City of Renton's Municipal Code (RMC 4-3-050) require Environmental (SEPA) Review. Permit Requirements: Due to the presence and proximity of sensitive and protected slopes, the proposed short plat will require Environmental (SEPA) Review. Short Plafs less than four lots are processed administratively within an estimated time frame of 6 to 8 weeks for preliminary approval. The Environmental (SEPA) Review will be processed concurrently with the Short Plat. Please see attached determination rega�ding the exemption from Site Plan Review for short plats with four units or less. The application is �1,000 for the Short Plat and �500 (1/2 price) for the Environmental Revie�v, plus first class postage (currently S0.37) for each mailing label required for notification to surrounding property owners within 300 feet of the site. The appl;cant will be required to install a public information sign on the property made and installed to specific standards. Detailed information regarding the land use application submittal is provided in the attached handouts. Once preliminary short plat approvGl is received, the applicant must complete the required improvements and satisfy any conditions of the preliminary approval before the plat can be recorded. The newly creafed lot may be sold only after the short plat has been recorded. Fees: In addition to the applicable building and construction permit fees, a Transportation, Parks, and Fire tvlitigation fee `vill be required prior to the recording of the plat (the project �vill be credited for the existing home). A handout listing all of the City's Development Fees is Gttached for your revie�v. Expiration: Upon preliminary short plat approval, the preliminary short plat approval is valid for two years with a possible one-year extension. !�",::�nuson Short P:zt(?-lot R-10).d�c`, III. OFFSITE DRAINAGE A. UPSTREAM DRAINAGE j The upstream drainage contribution to this site is negligible. The only up- ' gradient property is along the east property line, ond this is the Monroe Ave. NE. frontage. Monroe Ave. NE. is perved and has a slope to the north. The street pavement is crowned along the centerline, so all of fihe . runoff is directed fio the sides of the road. The runoff from the half road drains onto the site and also to the north within shallow swale ruts along � the road shoulder. B. DOWNSTREAM DRAINAGE The existing runoff from this property sheet flows to the west and onto the � adjacent property. There are no storm drainage improvements on this ; site. There are no existing storm drainage improvements within the � firontage rood. All of the runoff from this lot and the adjacent lots sheet flow across the surface, towards the west. The lot fio the west has an ; ecology block wall along the common property line with fhe subject 'I properfy. This block wall intercepts the flow from the site. It is assumed ' that there is drainage collection pipe along the back of the wall that would pick up this flow and channel it into the drainage system within the lot. This lot is a commercial site with frontage along Sunset Blvd. The drainage system within this commercial site fiows approx. 300 ff. and into the drainage sysfiem within the sovtheast shoulder of Sunset Blvd. The drainage then runs to the southwest, within the Sunset Blvd. The drainage system within Sunset flows to the southwest, within the edge of the road, and through a series of type 2 catch basins. After approx. 200', afi fihe intersection of Sunset and 12th Ave. NE, the drainage turns to the west and runs along the NE 12th St. There are a series of #ype 2 catch basins and piping near fihe center of the road. The drainage within NE 12th St. runs for approx. 1900', to fhe intersection of Edmonds Ave. NE. At this point, the drainage runs to the south along Edmonds Ave NE. There does not appear to be any problem with the downstream draincrge system. However, the sifie will utilize infiltration as d means to discharge at! of the developed drainage. As a result, there should be no runoff from this site into the downstream drainage system. I � � g � , �- � � C.� � _ � li i � - � i \ __��`\`.�.�.�� \ _ - ..'��`�.;`� `�`\�� •� ~/ �• � 1 � . � ..� � / ' , �� `��.�� `�� fs � � I � �,� � �� ` � \` �. Y ��\ � �`�� ` � � . 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PREDEVELOPED DRAiNAGE The drainage from the existing site sheet flows to the west across the ewsting lawn area and onfio the adjacent lot to the west. There are no drainage improvements on the site or along the frontage road. The existing drainage analysis was performed �sing the "Waterworks" hydrology sofiware and its summary tables and charts are attached for reference. The methods outlined in the King County Surface Water Design Manvcal were used as guidelines. Following this page are the data sheets used for the computer input dato. The computer summary sheets for peak flow and time of concenfiration calcu(ations are also attached. Below is a brief description of the ewsting drainage characteristics: Time of concentration: 12.61 minutes 2 year peak flow: 0.05 CFS 10 year peak flow: 0.11 CFS 100 year peok flow: 0.21 CFS � total area: 0.53 acres pervious area: 0.41 acres curve number: 78 impervio�s area: 0.12 acres curve number: 88.30 t[ _ ------_ ---- __-- -_ .. -- � --- . ,f � , -T . � (..-• - -. ... . ._._ - - -- --��-�- ------------------------- - -------------- -- 't k�,.a�--- �a �J `fJ,�J 2a� _ � ' j� -- '` •� � -S- f� s�.�-�--S�a�"a� m �- ', � da -�-5 l m�� ` - _ _ � 4 -- ,, , �,�, i--- �� t' -.�----��_ �I �-. -� �- �� ..�� t `' I � �S' �(f i �'Z��- �� I� �. i i. ' -�-- �•y___��.1� � V.S�'1 � 1.\ j;i J i �./ �:. � --- ' —_ �� + ' :�C2�-�� J O C'�:3:?�"3' �S ,;I � � 'v � j„ �-��-h O = �'oG� O - �S ' Q� . i ; - �:� •.Sc�o� n�a �;; .�. � � j ; i --- '��-�I��t� - --r� - ( -_ ; --- . . � O� _ � � ',y-X� �� '��,C'� 1', �c-�� s C'�-�—= `��z �. Z!1�.'r''��,2'J `��.1�4 � � i - --------- -------- - _ -- -------------- --- - - - �� -�, __ _ __--�r. L.� 'i�i�Zn�-��;� �311�T�' b'.T��5--�—— .. ------ �`-b=t� �� a—�-s� ` �rt�r��- II ------ -- --- -- , C�C t . .- �--�u�-'_�5-�._.7 -� -.- , -------- --- --------- - - � ' `/ .� -- � --- �S�s✓1�,J c-�� I 1�1 G��r.�� — : - I t� ��w -- ��U L � I @a� �`a�' S �� s �-- T , ��S ' �-- - � � � � '� ; I �S � �Z� Z = �' � `. � ; . � � � � i - -- - ��v�-�-7p, "� T - ��- o� i � -7�''��'� ,��, 1 I;; ."�c.�1�. _ � �^2T c� �� J..s ��2Z , 7 '� ;� �� a �; � c� � ;� z' -�oa a�'S -�-� ;, �� ; �: l� - -- i -. �-��Q - ��1�� -��a ;� - ;� ;� . i� �� I , . _ I I j i � � � � � � I t I I � iI � � � i � I h `�'1 l� I� � � ! �n O ,� � oo � ; '� � II I� i► q I a � i ( � � I � � _ ___.._ .� _ _ _ _.__ . ____ .__ __._.�, _ _ _. - -- - - -- --- - i i I ' ' � , � ' ; , I , � � - Jaeger Engineering . MAGNUSON SHORT PLAT PRELIMINARY DRAINAGE CALCS PRE-DEVELOPED HYDROGRAPH SUMMARIES --------------------------------------------------------------------- --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A10 NAME: PRE-DEVELOPED, 10 YEAR SBUH METHODOLOGY , TOTAL AREA. . . . . . . : 0 .53 Acres BASEFLOWS : 0 . 00 cfs R.AINFALL TYPE. . . . : TYPElA PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 .41 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 78 . 00 TIME OF CONC. . . . . : 12 . 61 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 .20 AREA. . : 0 . 12 Acres CN. . . . . 88 . 30 TcReach - Sheet L: 150 . 00 ns : 0 . 2400 p2yr: 2 . 05 s : 0 . 1070 PEAK RATE : 0 . 11 cfs VOL : 0 . 05 Ac-ft TIME : 480 min BASIN ID: A100 NT-�ME : PRE-DEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 53 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : TYPElA PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .41 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 78 . 00 TIME OF CONC. . . . . : 12 . 61 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 12 Acres CN. . . . . 88 . 30 TcReach - Sheet L: 150 . 00 ns : 0 .2400 p2yr: 2 . 05 s : 0 . 1070 PEAK RATE: 0 . 21 cfs VOL: 0 . 09 Ac-ft TIME: 480 min BASIN ID: A2 NAME: PRE-DEVELOPED, 2 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 .53 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : TYPElA PERVIOUS AREA PRECIPITATION. . . . : 2 . 05 inches AREA. . : 0 . 41 Acres TIME II3TERVAL. . . . : 10 . 00 min CN. . . . : 78 . 00 TIME OF CONC. . . . . : 12 . 61 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 12 Acres CN. . . . . 88 . 30 TcReach - Sheet L: 150 . 00 ns : 0 . 2400 p2yr: 2 . 05 s : 0 . 1070 PEAK RATE : 0 . 05 cfs VOL: 0 . 03 Ac-ft TIME : 480 min File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee;eeeeeeeeee; ° ° SHEET FLOW CALCULATOR - INITIAL 300 FEET ° o 0 0 0 0 °DES°Mannings Sheet Flow. . . . . : 0 . 2400 ° o °ARE°Flow Length (ft) . . . . . . . . : 150 .00 °HOICES ° �RAI°2 yr 24 hr rainfall (in) : 2 . 05 ° ° °TIM°Land Slope (ft/ft) . . . . . . . 0 . 1070 ° o °TIM° COMPUTED TR.AVEL TIME (min) 12 . 61 ° ° o�pjo TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° I °ABS° o 0 °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° ° °STO°Fallow Fields of Loose Soil Surface. . . . . . . . . . . . . . : 0 . 05 °y o ° °Cultivated Soil with residue cover (s<=0 .2 ft/ft) : 0 . 06 ° ° °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 ° ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° o 0 oBermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 .41 � o 0 oRange (natural) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 13 � o °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 .40 ° ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 ° ° °TOTo 0 0 °OF10Key: QUIT FSKey: CLEAR °ete ° ° Pgaeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° aeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ��- DL��.o�� r�E. c-�F C-C>N GE��Tt2�n�`'� B. DEVELOPED DRAINAGE The developed project will not include detention storage due to the minimal peak flow exemption allowed by the drainage code. Since ther8 are no existing connection points for a drainage system on this site, it is proposed to use individucal infiltration trenches for the roof gutfier/downspouts for the new houses. Infiltration is also proposed to be used for the runoff from the private road. Similar to the existing condition, the SBUH hydrograph method was used to determine the peak flows for the various storm events. The computer data sheets for the developed flows follow this page as well as the work sheets and the time of concentration calculations. A brief summary of the developed drainage characteristics are: time of concentration: 5.0 minutes 2 year peak flow: 0.11 CFS 10 year peak flow: 0.20 CFS 100 year peak fiow: 0.30 CFS total area: 0.53 acres pervious area: 0.33 acres ', curve number: 80 ' impervious area: 0.20 acres curve number. 98 --- - — - ---- _-- ----- ��i — ; �� `'C-� Q _ � - ,� ; - ,'i - - ��J �,Z 'G� = �� I� -- I S ) 1 `O = �a � ' I , s��,�� --�,��---��-�a�t--- ` � — _ ' � �a�;� � ,,,;-ac' �;� s � , � sa�n � iw► Q �, ' � -as � � �� , � -�wi � ' � - �g� _ .��, �--c�� -as - ; ,_ � zr �o = �z c� - �� '� - �. 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HYDROLOGIC ANALYSIS The site is exempt from the peak rate runoff control due to the negligible peak rate runoff rate increose exemption. This is specified in section 12_3- 5 of the drainage manual. The developed peak 100 year runoff flow is 0.30 CFS. The 100 yecrr pre-developed flow is 0.21 CFS. This is v 0.09 CFS difference, which is much less than the 0.5 CFS maximum al{owed for fihis exemption. D. DETENTION ANALYSIS AND DESIGN Detention Storage is not required for this project as stated above. E. BIO�ILTRATION Biofiltra#ion is also not required for this site. It is exempt from this reqliirement because it is adding less than 50�0 SF of new impervious surface that will subject to vehicular traffic. I