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HomeMy WebLinkAboutSWP272727(2) W7 HNI(AL I t3F1V1Al( NEP( t ' ; . ... .::::.>::>::>::::>::::> % t .:::............ . p . >. :... OUR JOB NO. 6116 R 'x.',,a Ell V E D JANUARY 15, 1998 JAN 3 0 1998 8llL6f ,jIIION �. LU Prepared By: �Q-�Of wAsy, BARGHAUSEN CONSULTING ENGINEERS, INC.\ 1` 1 821 5 72ND AVENUE SOUTH \'1, \ 28148 E� �Q KENT, WASHINGTON 98032 ,� c/s�a (425) 251 -6222 ass/°NAI.EN� i-15�� r( of Q GHAV L mT .n� S�2 o "-' CIVIL ENGINEERING LAND PLANNING SURVEYING, ENVIRONMENTAL SERVICES ,� ,�� w��pg, G, EN RONMEN 1 r"' :N."--- I. INTRODUCTION/GENERAL INFORMATION 1.0 INTRODUCTION/GENERAL INFORMATION The proposed Highland Marketplace is a shopping center consisting of several retail stores and a fast- food restaurant. The site is located in the northeast quadrant of the intersection of Duvall Avenue N.E. (138th Avenue S.E.) and N.E. 4th Street (S.E. 128th Street) in Renton, Washington. This location is in the Southeast quarter of the Southwest quarter of Section 10, Township 23 North, Range 5 East, Willamette Meridian, King County, Washington. The square-shaped site consists of approximately 8.4 acres. With the exception of a small area in the northeast corner of the site, the topography across the existing project is relatively flat. The site generally slopes from northeast to southwest at approximately 1 percent or less. The northeast corner of the site contains a slope from basically east to west which is approximately 15 percent. The site primarily contains moderate to dense brush and tree coverage, with the exception of a small cleared portion in the southwest corner which has approximately 0.5 acre of paved impervious area. Portions of two wetlands exist on the east half of the site, one of which will be filled and one of which will be enhanced as mitigation. The site receives no significant upstream drainage from off-site areas. On-site flows generally sheetflow from northeast to southwest toward the intersection of Duvall Avenue N.E. and N.E. 4th Street. The flows in the southeast corner of the site tend to flow toward the southeast corner and wetland "A," which is located straddling the east property line. Overflows from this wetland enter the storm drainage system in N.E. 4th Street. A complete Level 1 downstream drainage analysis is contained in Section 3 of this report. 6116.011 [KL/sm] ✓ s xE TN 67N NI PL N_ = 1 1qHT 24TH ST ys Q 6M NE > ' ._ ST F"• vixos �> �' 's LTHPIA 61H< <'ST ti_ II).SIN_ SI N NE M z AV HE < NE ST ST << ST .tE. y. RFRfN O TECCALsr YfNADSGQ `""°,LL xE HE m coLL E 4TH SE 128TH ST !TH = S7 •" s 2500 4300 U000 1300 = r r Y oppp <' h SE 129TH NE 3RD CT PL $ 1 _ NE L_NE_ ^�ND H 2 L-r .`^. SE _ 2No < ST 00 Dl t CTH ISTt .Fg .r9D sr 17 SITE Lff6URE c d I 5t 39x ESTATES T PL I 135TH € SE 0 T A OLIVE .PARK JT R1vER-:� < J CEMETERY SE ND a , ST —R Sr .... o P SE 136TH ST PAKK 2 �4. IN PAW --,--- s 13M STSE NVt4MY _ 6 AlF 4WD �< Q K', •n ,xW. of �q 1 SE 4 ►tH 1 <NtS9Tx It 6 �• • ♦x����� RD 5TN SE Marx SE 140M n tFN\ ` Sr Sr L-- �, Sf 'SE t12xD sr': PARK - 4 112ND ST <a y_ <' S SM srz N, 6 TR :. .. .. i Mr Y 1 E,, tt p� sE€I4zxD _ar ' SF S SE x Ins J F CEMR.' 1 te•\. 144 'f� 5 ARADLO `..6/. 0SN g /�PL�WQ 03 r�i C�D 10 z PARK `. E RJ A may'' Lb PSE tmv e I CEOAR 22 UVER 7 20 q o `�_< 27PAM zoHE `r'aa fNTpy A 1M ```,� A` �a lf'JT ^{ •, (.....•WP O,y '^ x G SE`,� f9y 161t'h'�• 's.I,� T xzs mY, $1 A�(.....fR J', 4 ti16TNGi O0. F - lX, C1N ST ` fAOJ. - EV g •' �e ST p� - .n� ,s y ,},y:<yl• ,y h ,t- 4'Sr !•3' ;8 ca _ a cf. _ sF ciRr l cT xv I �k... v,� < s4 r x ISM S1 N` ""' 3 'iPh r�rr ►ARK 'rr"ra•W St N}'$E, $ IR ?�a 1' N p mn rnxsr Iscrx I t� 'UGET `u lserx 21ST - N� ,��'q„ 9� ,s9r S, ...--i SE IN Rn^xl sE 15T Sr - 60T � i`St 1.Au• -�- I 15..1 R �j S, 121LP1 Sl-O SL 1697" Pl -- -- 160Tx SSA' �'SE �1 ST ST �6' tST SAP' 159T-N_.- n_.._._.. ._.. ..._ _.. SE x 16l T 5r SE 16mx n yI�SE j59 SE ST a� lblsrn '<5 ?'� �84'P sLt r "VS�Jf Q SE I67R0 ST a O �h> ►Aar Yn'KI � � °f .�tK SE 162ND PLI S 2TTH ST SE 1 TN .. S7 _ SE 164TH ST =�< .�iTM.� 21f R I H 10900 11100 ,)ri 117005 165Tx ST � c ix SE 64TH $ s1 Sr 6J,a3`� "'<IM 3' r�i,� s xlx- r � SE 16srx s_ E q• s< '� l SEt � x'`� -26 _�" 'F's=�s�,' 6 " 4r•k u Il6rxsr .EMI erx s > nrx sr < DE Sr Y ,� ,�1. y,s, r�g g q RWDOD sE i 66T"$ 17M ` sE.t66T`.� _tr ri y, / 16rrx Sr g 6 tea < r r a i6s`rN sr <' CI MSES N ;• >TN� LfMXE11GM NS K'I�l�6Tx PL < ea3FTc s •'x-i g, Ln A' 1 � 27 ..\� 4 1y s•F 160TH >e ST `1I- _ la SITE LOCATION MAP 1" = 2400' Reference: The Thomas Guide,King/Pierce/Snohomish Counties, 1997 Edition Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PROJECTPART 1 OWNER AND PART 2 PROJECT • • PROJECT • Project Owner Project Name HIGHLAND MARKET PLACE Address Location Phone Township 23 Project Engineer KARL W. LUNDBERG Range 5 Section 10 Company BARGHAUSRN CONSULTING ENGIN R Project Size 8.3 AC Address Phone 1 R21 5 72ND AVE. S0, KENT W Upstream Drainage Basin Size 0 AC 42 251-6222 98032 OF • OTHER 0 Subdivision 0 DOF/G HPA Shoreline Management 0 Short Subdivision 0 COE 404 Rockery 0 Grading 0 DOE Dam Safety 0 Structural Vaults FX] Commercial 0 FEMA Floodplain 0 Other E] Other 0 COE Wetlands HPA COMMUNITYPART 5 SITE DRAINAGE Community CEDAR RIVER Drainage Basin MAPLEWOOD CREEK PART'16 SITE CHARACTERISTICS 0 River Floodplain 0 Stream EX Wetlands 0 Critical Stream Reach 0 Seeps/Springs EO Depressions/Swales 0 High Groundwater Table 0 Lake 0 Groundwater Recharge 0 Steep Slopes 0 Other 0 Lakeside/Erosion Hazard PART 7 SOILS Soil Type Slopes Erosion Potential Erosive Velocities EVERETT, GRAVELLY SANDY LOAM 0-67 LOW LOW 0 Additional Sheets Attatched 1/90 Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT , F-1 Ch.4-Downstream Analysis 0 0 0 a 0 Additional Sheets Attatched PART 9 ESC REOUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION X� Sedimentation Facilities Stabilize Exposed Surface ® Stabilized Construction Entrance XD Remove and Restore Temporary ESC Facilities ® Perimeter Runoff Control ® Clean and Remove All Silt and Debris Clearing and Grading Restrictions ® Ensure Operation of Permanent Facilities ® Cover Practices E:1 Flag Limits of NGPES © Construction Sequence Other 0 Other PART 10 SURFACE WATER SYSTEM 0 Grass Lined Channel Tank Infiltration Method'of Analysis ® Pipe System Vault Depression SBUH Open Channel 0 Energy Dissapator 0 Flow Dispersal Compensation/Mitigation 0. Dry Pond Wetland 0 Waiver of Eliminated Site Storage ® Wet Pond 0 Stream 0 Regional Detention Brief Description of System Operation STORM DRAINAGE RUNOFF CONVEYED TO WET / DETENTION POND PROVIDING WATER QUALITY TREATMENT AND STORAGE Facility Related Site Limitations 0 Additional Sheets Attatched Reference Facility Limitation PART 11 STRUCTURAL ANALYSIS PART 12 EASEMENTS/TRACTS (May require special structural review) � Drainage Easement Cast in Place Vault 0 Other 0 Access Easement ® Retaining Wall 0 Native Growth Protection Easement 0 Rockery>4'High Tract EJ Structural on Steep Slope Other PART 14 SIGNATURE OF - • • I or a civil engineer under my supervision have visited the site.Actual site conditions as observed were incorporated into this worksheet and the attatchments. To the best of my knowledge the information provided here is accurate. Sigr,*".r• 1/90 II. PRELIMINARY CONDITION SUMMARY CITY OF RENTON tf PLANNING/BUILDING/PUBLIC WORKS DEPARTMENT MEMORANDUM DATE: DECEMBER 24, 1997 TO: PETER ROSEN FROM: NEIL WATTS SUBJECT: HIGHLAND MARKET PLACE SEPA CONDITION FOR DRAINAGE IMPACTS The proposed Highland Market Place development on the northeast corner of Duvall Ave NE and NE 4th St is located within the drainage basin for the Maplewood Creek. There are ongoing erosion problems in downstream portions of this creek. . Therefore, additional detention requirements are recommended as a SEPA condition to address this adverse impact. The recommended detention requirement for this project is as follows: The release rate for the developed site shall be limited to 50% of the predeveloped 2 year 24 hour storm event through the 2 year storm event, with a safety factor of 10% in the detention volume. The release rates for the developed site shall be limited for the 5 year, 10 year and 100 year storm event to the predeveloped rates for those events, with a 30% safety factor for the 100 year storm event. Conveyance requirements and water quality issues are satisfactorily addressed by existing City Code, which uses the standards of the King County Surface Water Manual. cc: Kayren Kittrick Ron Straka Ia s Re FOUND MONUMENT IN CASE W. 1/4 COR. SEC. 10 399.43 RAn- 'J2 4-17-95 ' 1 J #6zlt LE-JYJ 72(181N) L LE.-JPB 01(!B QFJ T FOUND 1 1/4'A Q L CA II SURFACE AION. ST. 7.54 4-17-95 i E,olrfhy ! 399.39 Rhr-ILY7 to 397.63 •398.38 LE-JAl I9( j / '9 rLE-3f9J59 B n 397.10 /L LE�JWT9 /T / "J99.50 397.04 ,11 11 401.19 •F• =396.80 •395.55 •796.5I $l G I YAPS F&cm •atJ 25 RE_ (-V.* /!/�� 39 36 4 SET REBAR Yk' .397.]e -W BB• 7,07 - PROP.COO,ER I 7*+39e 95 N BBb�1T �{' w 400.80 �/ n 404.11 11 Y��{ •3961,.. 96.23 5.976T- , �- ". r 3 i 4 06 I ( •396.0e395.96 - 11 •L I .S.N .}%94 LS fl AR kga? 1 � .93 .j96.79 11 lq• � 1 "3%.30 •397.19 \ •396.51 •399.02 •106.93 i 1 •19e_72 •39675 \ =197.79 l --w 7 39 •196.17 nl • 'Y 96.05 +;396.01 •397 25 02 .397.17 +407.20 :A?'f• •396/9 a1�39fi 91 �0� •196.36 397.03 ' ,396.44 j •409.36409.21 o 397.00 .396.66 •3%.95 w]95.72, •39e.54 SJ - •J97.21 396.95a 398.14 •395.77 •397.91 C Y, a 39648 , 4 .06.33 •408.91 I cGAL DESCRIPTIONc �3r .3%.15 .J9733 •396.es •397.02 THE SOUTHEAST OUARTER OF THE SOUTHEAST , „ •396.36 =39863 •39713 w 39&02 QUARTER OF THE SOUTHWEST QUARTER OF S, >' SECTION 10, TOWNSHIP 23 NORTH, RANGE 5 =39e.e9 `b 11 ,401. 6 •4042e EAST, W.M., IN KING COUNTY, WASHINGTON; ,19737 •S9aa9 a�] •3%72 .396z5 •404 35 m EXCEPT THOSE PORTIONS THEREOF LYING - •396 38 _ •396.59 .396.95 WITHIN S.E. 1287H STREET AND 138TH AVENUE S.E. I ';�,,-E - o •3%.9z f - .397.14 \ N 196.75 •196.41 396.06 0 $ .34669 •395.56 ;\ \ +40.05 +396.89 •3%.02 / y •na 6,4 +403.15 ' •396.54 - •.396.85 / •396.73 "39658 U M 396.05 +395.98 '396.87 1 397.58 +396.60 •395.80 / y / •�98.5, "s01.61 •403.15 w 396.29 % _ n 597.12 .397.25 397.99 ,39J.00 ; W�VI IIh f��2pp r P y ?_ MN .J9fi.01 ..W�JJ�9 5\1.9 1 Ij!' • N�y�,/V//.�,. . •3 I.303�° • 397.65/_396.51 Rbn 39750 • • 396.72 ZE- 397.98_ ' • 'I_I yL .m/LF�•am L VW I 11_I, ,1 91.44,IIu92 97 � .402 56 /A •396 12FuoM 397 J9].JB CL 397.22 in VERTICAL DATUM: }98.57 396.7 .0.75 CITY Uh N._NTUN 397.76 396.00 js ; Nti',Z m 1 �lJo}I N 396.00 4 II �r ,iY 0 a 596.447` a}97.•4 =39].16 +J9].91 V• / 1j C +399.15 �•' J d/ BRASS CAP AT INTERSECTION OF NE 4TH I r g o \`� (128TH S.E.) k 1401H SE /. ELEV_ - 398.5491' x •395 397.21.50 1 397.49 -98.02 •39130 I •396.15 / . , \ � � 39762 O1 (' BAnS OF BEARINGS: o / .397.72 ,� d -494.12 `7. •39s.73 W 3 - SOUTH LINE OF-TAE-SW 1/4 OF SEC. 10, c3 1 .J / k 39e.73 `L' .J94.96 03 4�„ TWN. 23N. RNG. ISE. W.M. v>i , .395.55 ( +494 .59767 `'.� l 0. `o N 88'02'58' W- K.C.A.S. ; 1 1 397Al y39].07 •397.44 n 398.23 4,,, W ,:3935 W A > E+•J5UJ7 •396.29 •397.05 "397.26 +J \ O U .q Z _�t 1• '. -- - a 397.63 _ I •395 30 a 395.73 O 2 GRAPHIC SCALE I 1 \ J -J'W 7D•39 9 • LL 197.79 M 397.85w 31.91 •J%.1] W y W O .} N •39e.00 \ \ (111 fS6T) Sx 'S7 •795.05 J98.a7 .,ueJ \y •j W W _ 1 Imh- 40 ft. 397A5 T ..� 1 595.92 Z 394.94 FFFM ] .397.85 397.23 396.07 t _ LEGEND r �-' `39�16 (,LU t ; .396.43 y 39 09 f9 - 5 = .,i€. n 397.14 a 397.07 UTILITY {1TY POLE E'- GUY ANCHOR I 1 /3(/(/ C/�I �,y�1. a 396.69 / V• `Y W O W O CATCH BASIN El _ r(� -* •396.93 1 •]95.51 • {! 1 F4 +396.1e \ ® STORM MANHOLE ASPHALT PAVEMENT 395.27 \ S t -.. •397.5e 39a +39776 Ldew •]95.93 y W y y y _POST1 W Z O MAILBOXJ SEWER MANHOLEoy GUARD RE HYDRANT -tl 75 Y e# .J96.29 •395.38 4 396 00 tx f;Y v-. "394.59 396 0 a 39833 a O 395 85 JZ STREET 9Q1 �- Erbf SSIA/ I i n :¢ _ JC 337.1:l 396 0, MOW.BI CASE • SET REBAR!CAP LS/12582 F,m 15 P .y N, j J L. x .397]4 .39sz0 W Y TU ND 'Ay L / U Is fi7.w Q &-f ,Z� Ls/1958z TYP =s95,a9 ^A t .� OYndOt A. WATER METER VARE FENCE f,.19 0/Aurs- 7 39553 ,g `} q *1 r� `� N D4 WATER VALVE -o- BOARD FENCE �w.N1" 'a�,; /* h R- JA00- 39s.n .al p r1'. .+ ,J97.93 I .J94.79 W .y y .l• •1( \` 0 ♦� D1 GAS VALVE -• WATER LINE I 9 %'V� _ x,�J.�B!' - ' 3 +399.15 O' 1 `�' W ♦J V/ ® TRAFFIC SIGNAL BOX -9- GAS UNE �, .� a T aA�� ,393.65 �F/58�1 ,7 a'i•g n a 398.31 �Q' `Y V� �L 41 V' Z � ,11 O t /Y]( Q rtpp9E9C00a1pm�r}pa{rw �81 rtt �1 a '` • 1 r TWO WAY TURN LANE SEMEII LINE C9'... { (J 45^r•1__ ++` °. 4�,�� s Iw]96.37 {3, V• V• W r Ll. LEFT TURN LANE TRAFFIC STRIPING s j y' � TRi,C11pN TIUTY EASEIALNT '1J 'ir e-rim.;: .397_J9 µ, �i f,r1 i Z �L �L S � r � N BB�3'1B' RE?�KR t 1 � F'•1j11 �* •.�.>. PATER INFORMATION RECEIVED 9 0 S a .."` '. �i ~� !` 'a r:.i, .>,y _ - - OM CITY OF RENTON r_ yps:. .�`2h4• ti,l. ,...ti a`^.:`�'J( .'F?.'s'- {^�0 T....P'i', " -., � r`�i Fr ?7_� J'r, y. -;^Q ✓p� '-tFP. s9B.4PrJ9- --- - - .. -- r-� Q 5/10/95 tm1 _ .Y •i s,r _'-.>?._ ,_.._ aL �.$L.., ..} .�. _ 7sT9� ~ H err ,_ +. ::� X,4y -ii,. LE�52(ia*N!IE4 1r FOUND MONUMENT It, CASE _ r- '.. �' - U'"7 • •g 5t5.q z • -GAS INFORMATION RECEIVED FROM SW CDR. SECTION 10 ( J WASHINGTON NATURAL GAS 'k. "t•. �:• .t` J:..t Ys : e' '.. '..s riF--!sv._.,,.� ,:,-r-:.x39a •39929 LOCATION APPROXIMATE 4-17-95 f�, ,.s..,r.; d y3a�„s!kT, mot" A,y_.., ,.�.i�.,� ,.�c'w...,Jd _+k� « i .i6 Et SHM S OUND �t s 5/10/95 4 r _- � !s? - § _ '"y _a"xi D08t�',S6C7a-101� 52 :wn(reYl• -SEWER INFORMATION TAKEN FROM L J9BJ7 SHEET DESIGN PLANS BY DODDS ENGINEERS, INC. DATED 4/01/94 1� 1 of 1 AgD Afc AgC 413 AgC 9 � •1• •9i5 AgB • Trader •• ii: it EvB a ark;• i n IIBM B i• r'.---•� �• II 424 Greenwood Cep • S'tE '• / i F 406 AgC An N \ I • ' C 14 kF AkF n � •it BM EvS klTi�,h, Py w° Golf I ItEvB / o`r •AkF I e• Rh I o o } a ry Ma AkF •� •r Py I h •• Pc r \'' •\ ', Ii C 41 A \ o Ma > \h\ 01 q ••1\Z ut' •u a Elio FC• •Rh W Ur ter u ;C �\ AkF I f I �I AkF Park Ng t py AgC n I 669 KING COUNTY SOIL SURVEY MAP 1" = 2000' KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL (2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20 CN points). However, high CN areas should not be combined with low CN areas (unless the low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be generated and summed to form one hydrograph. FIGURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN KING COUNTY � HYDROLOGIC HYDROLOGIC SOIL GROUP GROUP* SOIL GROUP GROUP* Alderwood C Orcas Peat D Arents, Alderwood Material C Oridia D Arents, Everett Material B Ovall C I! Beausite C Pilchuck C Bellingham D Puget D Briscot D Puyallup B Buckley D Ragnar B Coastal Beaches Variable Renton D Earlmont Silt Loam D Riverwash Variable Edgewick C Sala[ C —� Everett A/B 'Sammamish D Indianola A Seattle D Kitsap C Shacar D Klaus C Si Silt C Mixed Alluvial Land Variable Snohomish D Nelton A Sultan C Newberg B Tukwla D Nooksack C Urban Variable Normal Sandy Loam D Woodinville D HYDROLOGIC SOIL GROUP CLASSIFICATIONS A. (Low runoff potential). Soils having high infiltration rates, even when thoroughly wetted, and consisting j chiefly of deep,well-to-excessively drained sands or gravels. These soils have a high rate of water i transmissson. 1 B. (Moderately low runoff potential). Soils having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C. (Moderately high runoff potential. Sols having slow infiltration rates when thoroughly wetted, and consisting chiefly of soils with a layer that impedes downward movement of water, or sols with moderately fine to fine textures. These soils have a slow rate of water transmission. D. (High runoff potential). Soils having very slow infiltration rates when thoroughly wetted and consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a hardpan or clay layer at or near the surface, and shallow soils over nearly impervious material. These soils have a very slow rate of water transmission. From SCS, TR-55, Second Edition, June 1986, Exhibit A-1. Revisions made from SCS, Sol Interpretation Record, Form #5, September 1988. 3_5.2-2 11/92 EKING COUNTY, \VASII 1 NGTON, SURFACE WATER DESIGN MANUAL TABLE 3.5.2B SCS WESTERN NVASIIINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type to rainfall distribution, 24-hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP LAND USE DESCRIPTION A B C D Cultivated land(1): winter condition 86 91 94 95 Mountain open areas: low growing brush and grasslands 74 82 89 92 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed or older second growth 42 76 81 Wood or forest land: young second growth or brush 55 72 81 86 Orchard: with cover crop 81 92 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 O 66 90 fair.condition: grass cover on 50% to 75% of the area 77 85 90 92 Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89 t Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 0 100 100 Single Family Residential (2) Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 2.0 DU/GA 25 for pervious and 2.5 DU/GA 30 impervious portion 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 Planned unit developments, % impervious condominiums, apartments, must be computed commerdial business and industrial areas. (1) For a more detailed description of agricultural land use curve numbers refer to National En,-': •^•eering Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. . 3.5.2-3 111192 III. OFF SITE ANALYSIS