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HomeMy WebLinkAbout20020296 Landmark ENGINEERING Ltd. July 30,2001 Project No. SCHU-9F1I-01-321A1 Mr. Drew Scheltinga, P.E. Weld County Public Works Department 1111 H Street,P.O. Box 758 Greeley, CO 80632 RE: Drainage Report and Plan for the Schultz 1"Subdivision Dear Mr. Scheltinga: We are submitting the Conceptual Drainage Report for the Schultz 1" Subdivision for your review and approval. The 32-acre subdivision contains five residential lots varying in size from 4.21 to 10.02 acres. _ Improvements involve a graveled private drive entry ending in a cul-de-sac,water main and service lines, individual subsurface wastewater disposal systems and homes. The Drainage Report was prepared using the City of Loveland Storm Drainage Design Criteria (May 1986), and in accordance with the Weld County Subdivision Ordinance 173-E (10/97). Please feel free to call if you have questions or comments. Respectfully, Landmark Engineering Ltd. Prepared by: Reid W. Bond Project Engineer, Colorado P.E. 29647 RWB/ej 2002-0296 EXHIBIT 1 24 3521 West Eisenhower Blvd. Dale Olhausen, P.E. &L.S. Loveland,Colorado 80537 President ENGINEERS • ARCHITECTS • PLANNERS • SURVEYORS Loveland(970)667-6286 FAX (970)667-6298 Denver(303)629-7124 .�. CERTIFICATION I hereby certify that this Conceptual Drainage Study for the Schultz 1"Subdivision was prepared by me or under my direct supervision in accordance with the provisions of Weld County for the Owners thereof. Reid W. Bond ProjectEngineer, Colorado P.E. 29647 TABLE OF CONTENTS Page No. SECTION 1 - EXECUTIVE SUMMARY Project Objective I - 1 Site Summary 1 - 1 Analysis Summary 1 -2 Design Summary 1 -2 SECTION 2 -GENERAL PROJECT LOCATION AND DESCRIPTION r Project Location 2 - 1 Proposed Development 2- 1 Location Map 2 - 2 SECTION 3 -DRAINAGE BASINS AND SUB-BASINS Development Master Plan 3 - 1 Hydrologic Criteria 3 - I Runoff Routing 3 - 1 SECTION 4-DRAINAGE DESIGN CRITERIA Major Drainage Basin 4- 1 Contributory Drainage Areas 4- 1 SECTION 5 -DRAINAGE FACILITY DESIGN Proposed Drainage Concept 5 - 1 Proposed Drainage 5 - 1 Onsite Detention 5 -2 Summary of Developed Subbasin Discharge 5 -2 ., SECTION 6 -EROSION AND SEDIMENT CONTROL Design Conformance 6 - 1 Storm Sewer System&Culverts 6 - 1 Open Channel 6 - 1 Flow Dispersion 6 - 2 SECTION 7- EROSION AND SEDIMENT CONTROL _ General Control 7 - 1 Minimizing Soil Exposures 7 - 1 Controlling Runoff Across Exposed Areas 7 - 1 ATTACHMENTS —. Travel Time Velocity For Rational Method Runoff Coefficient and Percent Impervious Roadside Ditch Sections Roadside Ditch Capacities Worksheet-Trapezoidal Channel Cross Section-Trapezoidal Channel APPENDIX Exhibit"A" - Historic Runoff Exhibit"B" - Developed Runoff SECTION 1 EXECUTIVE SUMMARY 1.1 Project Objective This drainage report identifies existing and proposed drainage features and determines impacts that may result from the proposed Schultz 1"Subdivision, located in Weld County,near Berthoud, Colorado. This study is performed on behalf of Mr. Harlen J. Schultz (Owner). Impacts and mitigation measures are presented. Because Weld County does not publish technical data, or storm drainage design manuals, information developed in this report is based on the City of Loveland Storm Drainage Criteria Manual dated March 1986, and are in conformance with Weld County storm drainage regulations. 1.2 Site Summary _ The proposed Schultz 1St Subdivision(Project)is located in Western Weld County at the intersection ofWeld County Roads 1 and 46, approximately 1.8 miles Northeast of the Town of Berthoud. Specifically, the project is located in the Southwest Quarter of Township 4, Section 7, Range 69W, and contains approximately 32.5 acres. Runoff from the proposed project has historically drained as overland flow from North to South toward Newell Lake. Drainage received at Newell Lake flowed further South and drained into the Little Thompson River. Current agricultural activities have redirected historic flows such that a portion directly drains to Newell Lake, while the remaining area drains to MacIntyre Ditch. Ultimately all drainage from the site flows via the two conveyance elements to the historic outfall,the Little Thompson River. Inspection of the Flood Insurance Rate Map for Weld County (Panel No. 080266 0725 C) indicates that the project is not within the floodway of the Little Thompson River,nor is it within the 100-Year flood inundation area of Newell Lake. The subdivision will include five individual lots varying in size from 4.81 to 10.34 acres. A 550-foot private drive off County Road I will end in a 100-foot diameter cul-de-sac that provides common access to all lots. Drainage improvements will be minor,involving a road ditch collector that will be direct flows South to a graded spreader on the South end of the property. In addition,negotiations with County government and 1 - I irrigation ditch entities resulted in an agreement to relocate the irrigation ditch approximately 35 feet East to allow for future road improvements. 1.3 Analysis Summary Hydrologic analyses conducted for the Schultz 1"Subdivision Project is based on requirements mandated under the Weld County Subdivision Ordinance 173-E,and stormwater management criteria included in the City of Loveland Storm Drainage Criteria Manual. Stormwater runoff analyses are based on the Rational Method. Area II rainfall zone was used for precipitation - frequency data in the analysis. Analyses of stormwater conveyance elements from the site to the ultimate outfall is provided to ensure adequacy,- 1.4 Design Summary The Schultz 15`Subdivision seeks to subdivide five lots for residential development in Western Weld County at the intersection of County Roads 1 and 46. As such,the Owner will provide adequate onsite stormwater management infrastructure in order to mitigate potential drainage concerns associated with such developments. Proposed stormwater conveyance improvements include the installation of a 36-inch irrigation ditch culvert and a 15-inch road ditch culvert at the project entrance off County Road 1; two 18-inch drainage culverts under Schultz Lane and one driveway onsite; and a 10-foot by 1-foot deep drainage ditch ending in a level spreader at the South edge of the subdivision. 1 -2 SECTION 2 GENERAL PROJECT LOCATION AND DESCRIPTION 2.1 Project Location This site is described as a parcel of land located in the Southwest Quarter of Section 7,Township 4 North, Range 68 West of the 6ih Principal Meridian, Weld County, Colorado. More generally, the site is located approximately 1/3 mile North of the intersection of County Roads 1 and 46. The site is bordered on the East and North by land currently used for agriculture. The total contributing basin area is approximately 77 acres, which includes the project area and adjacent lands. The project area slopes to the South toward County Road 46 at an average slope of about 1.8 percent. See map in this Section. 2.2 Proposed Development Proposed development will include 5 single family homes on lots varying in size from 4.81 to 10.34 acres; a 550-foot gravel private drive ending in a 100-foot diameter graveled cul-de-sac; 5 individual wastewater _ disposal systems; 640 feet of 8-inch water main ending in a fire hydrant;water service lines; and drainage facilities. 2 - 1 4 . 11P- _i_) 2) ) /; \iiii --\ ri\ .___:• ) („...,_.,) i ly,„„ _I__ _„ ,_ .... 4 / --- •. _,. , _ .. ir__ 4 )__ ISinr.rg;lopc --,77--< 7 t� -°• ICJ 1, I 8�J Sl ----__/-1-. u.l _ i 4 __..__,„„=„. • _ __,_--" , ,, • Jo, : . -3, i--7----1:----- --. (--\. •i;';'99.1 Hummel', • a Y of \ / I ( `_!_`� \%/ .. 9 ,.._,•- :___::......„,„\_ •„..\., ),I -__ , 1, Lhcan 8 ^ <,e 4, -,.....„..:, , Lake _I Seas-rr_�) \\ HtLIhLjc± c . I f ,/ ` — / i ;;,, I .. ao° ( / ; \ / 19 I , \H _yjx.,..._ /i . /�Ilf/ �i`11r/� r-\_Itt� �\. �V ‘ / 1 j✓/ vrcr-����_-.__- ) a- -=-..-- ctc { j1 SIB r \ 4237 _- _ __ ro:tl �� 2,-ate=f �I`/ Irk11 //I _ II \ r ii ',1.1U LU TITLE: ,SCi-/ut_2 / 'r J�,nrv/lit:-/..,A.,/ - DRAW'45 rc.oJ77,,✓& -rl �UUUu1 �a®9a���ecx��cm. NEERS�ARCHITECTS/PLANNERS/SURVEYORS CLIENT: /JA/ tt.7/ v -521 West Eisenhower Blvd., Loveland, Colorado 80537-- ) 667-6286 Denver (303) 629-7124 Fax (970) 667-6298 SC:AI F-I Pt', 7Goo r I OAT.`-: 7�/2/27 I PROD. s ,Jv - 9.2.--//4../-92 / - SECTION 3 HYDROLOGIC ANALYSIS 3.1 Development Master Plan Policies and guidelines outlined in the Weld County's Subdivision Ordinance 173-E and the City of Loveland Storm Drainage Criteria Manual have been utilized for planning drainage facilities for the project. The site has been designed to convey runoff from minor and major storm events. Portions of site runoff will be divided,directed by onsite improvements,and discharged into historic drainage corridors to the ultimate outfall at the Little Thompson River. No adverse impacts resulting from the proposed development plan are anticipated. 3.2 Hydrologic Criteria This development is situated within Hydrologic Area II as defined in the City of Loveland Storm Drainage Criteria Manual. Weld County design storm frequency requirements are, a 5-year design storm period for residential and open space,and 10 years for local road crossings conducting drainage. (Table 24.2, Section 24-7-130, Storm Drainage Design and Technical Criteria). These storms are used as basis for planning and system design. The peak flow rate for the design point is calculated based on the rational method as described in the Storm Drainage Criteria Manual, with storm duration set equal to the time of concentration for the basin. Hydrologic analysis for the design of storm sewer facilities for the project made use of the Rational Method. Runoff estimation was performed for the 10 and 100-Year storm events. Runoff analysis considered that under the changes in the existing subdivision (buildings and roads), contributing runoff estimations were performed for the area to the North, the project site, and the offsite area to the South that flows to the intersection of County Roads 1 and 46. 3.3 Runoff Routing Historic runoff routing will be slightly modified by site improvements. The new private drive and cul-de-sac will intercept South trending flows which will be directed West to MacIntyre Ditch or through ditches and culverts to a level spreader located at the subdivision's South boundary. Diverted flows will eventually go 3 - 1 to the McIntyre Ditch at the intersection of Weld County Roads 1 and 46,and will be ultimately discharged to the Little Thompson River. — 3 -2 SECTION 4 EXISTING DRAINAGE 4.1 Major Drainage Basin The site lies in an unidentified major drainage basin that contributes runoff South to the Little Thompson River. Existing drainage features within the major basin and local to the project include Bacon Lake,Newell Lake,and irrigation ditches(including MacIntyre Ditch). Additional storage and conveyance elements exist upstream and downstream of the site,but should not influence or be adversely impacted by the project. 4.2 Contributory Drainage Basins Drainage on or through the subdivision site ultimately flows to the MacIntyre Ditch, which flows South along County Road 1 to the Little Thompson River or to Newell Lake located approximately 1/2 mile southeast of the subdivision. These two subbasin areas have been broken down into offsite and onsite designations to better define the impact from subdivision improvements. (See Drainage Map No. 1). Subbasin 1 includes drainage going to Newell Lake and consists of 5.47 onsite acres and 6.17 offsite acres to the North of the proposed subdivision(Total 11.64 acres). No proposed improvements will occur in this area and subbasin discharge will occur as sheet flow across the 250 foot eastern portion of the subdivisions South boundary. Subbasin 2 consists of two areas that drain to the same location-MacIntyre Ditch,located at the intersection of Weld County Roads 1 and 46. The Eastern area starts North of the proposed subdivision, flows South across the middle 1/3 of the subdivision, and offsite toward the intersection of the County roads. The Western area flows either parallel to or into the MacIntyre Ditch which flows South to the County road intersection. Summary of Existing Subbasin Discharge Subbasin Area `C,oyr Qiooyr ID (acres) (cfs) (cfs) O1 6.2 2.3 7.3 1 5.5 3.4 10.7 4 - 1 Subbasin Area `210yr (2100yr ID (acres) (cfs) (cfs) 02 East 17.95 6.4 20.1 2 East 21.6 11 34.5 02 West 9.5 2.3 7.3 2 West Subd. 4.4 2.5 7.9 02 West/South 1.95 2.7 8.5 4 2 _ 1 9.17 Peo2I if)ano3 PL°M r I U P. A3 I 5 R U i- a V I a _= s �to r, I § O 7-13 , R 4 z ° x oa W Rte. L4 O C4 2 (y c O Q W z 0905 w w C7 A Q N ... I 4 OLOS _ J A O E, 080C o C E C f Vf Ca CCS f�l W 1�1 N -- O 0605 SECTION 5 - PROPOSED IMPROVEMENTS&DRAINAGE 5.1 Proposed Drainage Concept The proposed drainage concept for the Schultz 1" Subdivision will utilize existing and proposed drainage features,which include culverts,grading and drainage ditches. Drainage improvements will be installed to mitigate potential problem areas. 5.2 Proposed Drainage Site work will not change water runoff differences between subbasins. No work will occur on the East portion of the subdivision that has runoff flows going to Newell Lake. However,changes in flow direction will occur in the middle and Western portions of the subdivision, due to the private drive and cul-de-sac —. construction. Historic flows interrupted by these improvements will be directed by means of culverts and ditches to either MacIntyre Irrigation Ditch (West area) or to the South border of the subdivision. As a result,the historic subbasin areas have been divided to better define post development runoff patterns. See Drainage Map 2 for subbasin layouts. Subbasin 1 will not change from its original condition, containing 5.5 onsite areas and 6.2 offsite acres. Runoff will be as sheet flow over the Southern subdivision boundary. Subbasin 2 consists of components that either drain directly to the South subdivision boundary,to MacIntyre Ditch,or will become concentrated and drain to the middle South boundary because of the new road,cul-de- - sac and home construction. Description of the subbasin components follow. 2a consists of 8.1 onsite acres and 0.75 offsite acres that ultimately sheet flow South across 320 feet of the South subdivision boundary. 2b consists of 1.5 onsite acres and 9.5 offsite acres that flow to the South and Southwest. Flows are diverted West into MacIntyre Ditch just North or Schultz Lane. 2c consists of 4.3 onsite acres which sheet flow South and Southwest over a 460-foot width of the subdivision's South boundary. 5 - 1 2d consists of Weld County Road 1 ditch and Maclntyre irrigation ditch. The irrigation ditch and road are being realigned and will consist of 1.05 acres adjacent to the subdivision and 1.95 offsite acres extending South to Weld County Road 46. All flows are collected by the MacIntyre Ditch. 2e consists of 5.2 onsite acres and 3.3 offsite acres. Runoff flows South-Southwest around the proposed cul- de-sac,and enters either the new ditch extending South from the cul-de-sac or is intercepted by the proposed level spreader. 2f consists of 5.85 onsite acres and 13.9 offsite acres. Runoff flows are intercepted by Schultz Lane,diverted to a drainage culvert under Schultz Lane, around the South side of the cul-de-sac to a new ditch extending to the level spreader on the South subdivision boundary. Runoff collected in the level spreader will eventually rise and uniformly overtop the 20-foot long spreader to sheet flow toward MacInyre Ditch at the intersection of Weld County Roads 1 and 46. 5.3 Onsite Detention No onsite detention is proposed for this development. Historic flows will not be significantly increased because of the large subdivision lot sizes(4.81 to 10.08 acres),and small impact of the single graveled access drive and cul-de-sac. Most runoff flows will be sheet flows exiting the South subdivision boundary. Historic flows diverted by the drive and cul-de-sac will flow through culverts and ditches to a level spreader that will serve to disperse collected waters into a sheet flow condition. 5.4 Summary of Developed Subbasin Discharge Subbasm Area ll1on L►iooyr ID (acres) (cfs) (cfs) 01 6.2 2.3 7.3 1 5.5 3.4 10.6 02a 0.75 0.4 1.2 2a 8.1 3.1 9.7 02b 9.50 3.2 10.1 2b 1.5 3.7 11.7 2c 4.3 4.2 12.6 2d Subd. 1.05 3.7 11.8 5 -2 Subbasin Area `G,oyr (hooyr ID (acres) (cfs) (cfs) 2d 1.95 4.8 15.2 02e 3.30 1.6 4.7 2e 5.20 3.1 9.0 _ 02f 13.9 4.3 13.5 2f 5.85 5.6 17.8 5 -3 9ti Pe02I kitinop PI0M 63 — � In, c4 4 111 Cal U• 6 .b a � c a N o y U CK U � 1 � O r c20 FO C] ^ - ZWQ ,6 C!� y ry p., a Mu .6 N 3 SWW — X �\ v ¢a w 3 / . 4..ce Z 0 • I \ ....,.OQ a a0 asn ( •-I N N 'b Ce O " a v . — . = �1 (ID u, / N N W A 1' tu N • 4, N C - N N al p .6 O DI O r, SECTION 6 DRAINAGE FACILITY DESIGN 6.1 Design Conformance Design of onsite drainage facilities was performed in accordance with the City of Loveland Stormwater Drainage Criteria Manual (May, 1986). Design analysis incorporated the Rational Method,with results of runoff estimation for various return intervals used to size storm drainage facilities. 6.2 Storm Sewer System& Culverts This project's drainage infrastructure is designed to collect,convey and disperse flows based on the County required 10-Year design storm frequency. All onsite storm line sizes are 18-inches or greater Class II reinforced concrete pipe materials. Minimum cover over culverts will be no less than 1 foot under Schultz Lane. A minimum of 18 inches of clearance will occur where storm lines cross sanitary lines. Flow velocities have been designed to be between 2 and 7 feet per second(fps). Culvert design is in accordance with the City of Loveland's design criteria. Culvert design conforms to — design requirements associated with design storms,minimum culvert size and allowable cross street flow. Outlet velocities are maintained at or below 7 fps. Structural design is also in conformance with criteria, with a minimum H-20 loading. 6.3 Open Channel Design of onsite open channel facilities was performed using the City of Loveland's Drainage Criteria Manual. Onsite open channel conveyances include roadside ditches and drainage swales. The roadside ditch slope is 0.5%,allowing for flows up to 6 cubic feet per second(cfs). The drainage swale going South from the cul-de-sac has a 1.9% slope and can carry up to 15 cfs. Offsite open channel facilities include the road ditch and irrigation ditch paralleling County Road 1. The realigned road ditch will have a 1%slope,will collect and carry flows from the road and the ditch areas only, and can carry flows up to 14 cfs. The irrigation ditch will have 3 to 1 sidewall slopes and a 2-foot horizontal base. Its slope will be maintained at 0.5%and will have a discharge capability of 42 cfs. All open channel flows should conservatively handle anticipated 10-Year design storm frequencies. 6 - 1 6.4 Flow Dispersion Runoff flows in the middle one-third of the subdivision must be collected and diverted because of the construction of Schultz Lane. Flows ultimately end up at the South boundary of the subdivision reaching anticipated 10-Year flows of 8.7 cfs. Construction of a level spreader is intended to receive the diverted flows and spread the flow over a 20-foot berm width, creating non-erosive sheet flows at the South subdivision boundary. At 10-Year storm frequency flows, water flowing over the spreader will have an anticipated velocity of 0.5 feet per second. 6 -2 SECTION 7 EROSION AND SEDIMENT CONTROL This section describes methods, which are recommended to control surface erosion by wind and surface water runoff during and after site grading improvements. 7.1 General Control Clearing and stripping of this site for overlot grading may cause localized erosion with subsequent deposition of sediment offsite. Uncontrolled, erosion and sediment deposition could create undesirable conditions to downstream properties. Generally,erosion and sediment control will consist of minimizing soil exposure,controlling runoff across exposed areas, and capturing sediment. These measures are described below, and should be implemented by the developer during construction activities for the site. 7.2 Minimizing Soil Exposures Where practical, the construction area and soil exposure will be kept to a minimum. Grading activity will be completed as soon as possible. Permanent vegetative cover and landscaping will be established in the disturbed area. In place of or with revegetation, decorative rock, gardens or shrubs may be used in final landscaping to reduce soil exposure. Reseeded areas should be mulched with straw or hay to protect exposed soil until vegetative cover is established. 7.3 Controlling Runoff Across Exposed Areas Where practical,construction of temporary swales to intercept,control and direct storm water runoff around exposed areas is recommended. Straw bales, silt fences,and other temporary erosion control devices may be installed to control storm water velocities across exposed areas. 7 - 1 LIST OF REFERENCES City of Loveland, Storm Water Criteria Manual,March 1986, WRC Engineering, Inc. Colorado Department of Transportation, Erosion Control and Stormwater Quality Guide, June 1995. r ATTACHMENTS • LOVELAND FIGURE 902 STORM DRAINAGE CRITERIA MANUAL -- TRAVEL TIME VELOCITY FOR RATIONAL METHOD 50 30 /// J 20 Z o `1 U WLig . r JA. D `T A. J W a J. h V a 10 �! £ 3r I Z t A. S .r 0 A. O . IL 0. =ov eW 4-.4' 04/ 4 fr y2r J . O L. pJ 5 v 4. , W * v N 4 ¢ it 0 Iv J O Z.W rWr = N v ' 4 - cc 3 4� (S a C A. 4 et O S O i y4 eelO 2 y .1 yr �, w � t. )- 0 AlIT < 4 3 p — 1 ct .5 Y I I .1 .2 .3 .5 1. 2 3 5 10 20 - VELOCITY IN FEET PER SECOND WRC ENG. REFERENCE: 'Urban Hydrology. For Small Watersheds" Technical Release Ho. 55, USDA, SCS Jan. 1975. LOVELAND ELAN D STORM DRAINAGE CRITERIA MANUAL TABLE 601 RUNOFF COEFFICIENTS AND PERCENT IMPERVIOUS RUNOFF COEFFICIENTS LAND USE OR PERCENT FREQUENCY SURFACE CHARACTERISTICS IMPERVIOUS 2 5 10 100 Business: — Curtmercial Areas 95 .87 .87 .88 .89 Neighborhood Areas 70 .60 .65 .70 .80 _ Residential : Single-Family Figure-603 .40 .45 .50 .60 `Multi-Unit (detached) 50 .45 .50 .60 .70 Multi-Unit (attached) 70 .60 .65 .70 .80 1/2 Acre Lot or Larger Figure-603 .30 .35 .40 .60 Apartments 70 .65 .70 .70 .80 — Industrial : Light Areas 80 .71 .72 .76 .82 Heavy Areas 90 .80 .80 .85 .90 Parks, Cemetaries 7 . 10 .10 .35 .60 Playgrounds 13 .15 .25 .35 .65 — Schools 50 .45 .50 .60 .70 - Railroad Yard Areas 40 .40 .45 .50 .60 Undeveloped Areas: - Historic Flow Analysis 2 ( see "Lawns") Greenbelts, Agricultural Offsite Flow Analysis 45 .43 .47 .55 .65 (when land use not defined) Streets: avid 100 .87 .88 .90 .93 Gravel 13 .15 .25 .35 .65 - Drives and Walks 96 .87 .87 .88 .89 Roofs 90 .80 .85 .90 .90 - Lawns , Sandy Soil 0 .00 .01 .05 .20 Lawns, Clayey Soil 0 .05 .10 .20 .40 NOTE: The Rational Formula coefficients do not apply for larger basins where the time-of-concentration exceeds 60 minutes. WRC ENG REFERENCE: USDCM DRCOG Rev. May 1, 1984 -629- LOVELAND STORM DRAINAGE CRITERIA MANUAL FIGURE 708 ROADSIDE DITCH SECTIONS - DITCH TYPE I Shoulder, width voriti Property line e Note 3 12 Min. fMaximum depth for 5year flood (Typ.) s'. °.: :4-:yam• ':.[.. / ,� (..i... . Pavement l 5 _Li l — 4 Allowable slope from Grassed slopes (Typ.) 0.5 % to 2.5% - DITCH TYPE II Shoulder, width varies Property line See Note 3 12 Min. '� • ~ _ Pavement q r 4/ L1.1Allowable slope from 0.5 % to 2.5 % 66"---36 layer of rip-rap with D50=3, and — _ 4' filter material DITCH TYPE DI . Shoulder, width varies Property line111 See Note 3 '"4 12' Min. .,—./d 'Li JJ 4 l m 5/ Pavement 5 Allowable slope from b'' e' Concrete trickle — 0.5 % to 1.5 % �� _.�'� C channel 4„ 2' NOTE: 1. See Table-705 for capacity of roadside ditch. 2. For street slopes greater than maximum allowable, ,- rcheck drops (2' maximum height) will' be required. L., 3. Street cross section may include concrete curb and gutter. — WRC ENG. REFERENCE Prepared by WRC Engineering, Inc. .=%5L- STORM uRAINAGE CRITERIA MANUAL I TABLE 706 ROADSIDE DITCH CAPACITIES SLOPE DITCH TYPE I DITCH TYPE II DITCH TYPE III _ (%) VEL. Q VEL. Q VEL. (fps) (cfs) ( fps) (cfs) (fps) (cfs) 0.5 0.7 6 0.7 6 2.5 22 1.0 1.6 ' 14 1.6 14 3.5 31 1.5 2.4 22 2.4 22 4,4 39 2.0 3.2 29 3.2 29 Not Permitted 2.5 (3) 4.0 36 4.0 36 Not Permitted — NOTES: 1. See Figure-708 for geometry of roadside ditch. 2. Velocity and capacity are based upon the SCS Retardance Curve "C". 3. Maximum permissible slope for roadside ditch is 2.5%. Slope limitation is based on a maximum Froude number of 0.8 for Type I & II and 0.9 for Type III ditch. • 4. Linearly interpolate for intermediate slopes. L y✓' WRC ENG. REFERENCE: Caculations by WRC Engineering, Inc. -740- Worksheet Worksheet for Trapezoidal Channel Project Description Lam, Worksheet Trapezoidal Channel-1 Flow Element Trapezoidal Channel Method Manning's Formula — Solve For Discharge Input Data Mannings Coefficient 0.022 r Slope 0.005000 ft/ft Z O•'/ , S G°P* Depth 1.50 ft _ Left Side Slope 3.00 H:V Right Side Slope 3.00 H:V Bottom Width 2.00 ft Results Discharge 41.74 cfs Flow Area 9.8 ft2 Wetted Perimeter 11.49 ft r^d 1 Ft oW Wi I> 771 Top Width 11.00 ft ��' Top A4• Critical Depth 1.35 ft Critical Slope 0.008009 ft/ft Velocity 4.28 ft/s Velocity Head 0.28 ft Specific Energy 1.78 ft rt° V n� / / �/ Froude Number 0.80 K r0 V 12D 6103 C R Ire"C t Flow Type Subcritical L • ... I Project Engineer:Landmark Engineering Ltd. c:lhaestadVmwlschultz.fm2 Landmark Engineering Ltd FlowMaster v6.0(614ej 04/13/01 10:23:34 AM ®Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06706 LISA (203)755-1666 Page 1 of 1 Cross Section Cross Section for Trapezoidal Channel Project Description Worksheet Trapezoidal Channel-1 Flow Element Trapezoidal Channel Method Manning's Formula Solve For Discharge Section Data Mannings Coefficient 0.022 Slope 0.005000 ft/ft Depth 2.50 ft Left Side Slope 3.00 H:V Right Side Slope 3.00 H:V Bottom Width 2.00 ft Discharge ' 137.41 cfs — w L K ris/CAN PIA, vJ 2.50 ft 2.00 ft- V:5.0\ H:1 NTS Cl{�irN111 F_L W/FgcC iMZD Sc/w& F, c7o11 S: I Project Engineer:Landmark Engineering Ltd. c:thaestadHmvAschultz.fm2 Landmark Engineering Ltd FlowMaster v6.0[614o) 04/1301 10:24:16 AM 0 Haestad Methods,Inc. 37 Brookside Road Waterbury,CT 06706 USA (203)755.1666 Page 1 of 1 - APPENDIX EXHIBIT A HISTORIC RUNOFF w --1 i1 w 1. 9b puoI i tmo3 proM •� fx A � — � ti° o . fi o r o v 0 w / _ _. u. 7 O�.c '6 G 8 Ni H c 667,...1_ .•.� _ ..... Z,'" "� M - `~ O C4 W I _ o � Q z 090S j W 4 A Q = N I 4 Q E- ()LOS ! J Q p up cn N O 080S c F-, N H O v a� 0 cl 415 W c'-1 — Q O 0605 . - �. 0 N N w 0 0 0 0 0 0 0 I- 0 �U v er er -4- er — = 3 y 0 wowet0cow 7 N r w co r- I- — U76 N h co •M T O ;10 0 0 0 0 0 0 7 V V V V V Tr 0 0 0 0 0 0 Cl) CU U Q (O to r N W of V 2 0 0 0 0 0 0 0 al V 0 0 0 0 0 0 0 C , 0 0 0 0 0 0 0 - O r a try C U (coo co coccoo ccoo co ccoo coM 0 j o 0 0 0 0 0 0 U cU d moo o o o o o O N E 0 0 0 0 0 0 0 N a Q o 0 0 0 0 0 .)C W a o 0 0 0 0 0 0 L Q .$ 0 0 0 0 0 0 0 03 U j 0 0 0 0 0 0 C) } 4 0 0 0 0 0 0 0 O (J O M o O) O) O) O) N 0 0 0 0 0 0 0 m 0 0 0 0 0 0 0 ` 0 0 0 0 0 0 0 l c 0 0 0 0 0 0 0 Ul m 0 0 up 0 0 to N C cp N to to co o Q co to T- N Oi V T- - c m z m �'p _ N N co N in i y CO 0 0 Or M LLI co — po ON P) Q o) N t 0 0 0 0 0 0 0 J al0 N N N N N N N 'd O O O C C C O N d V 0 0) N 0 O a) N r N M 6) 0) CO M 'Q r 00 611• 0000000 j O o 0 0 0 0 0 yy N d o to O) Q CO LO . 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LL J O rn ▪ (2144V0I e .4 .4 � CO V co .Y in < N el v-i c (MW) 31 o n N n ci .4 .4 r (.0 (Sd0) a m ri " 1 0 N N v. N q ill d N 10 N N O in . 01 O O .4 !1 O N (LFUM) 1 63 m 2 e $2 2 2i n m o m it N .4 .4 N M T .4 p N .4 N .4 .4 N O 0 0 M 0 N O 1Y N N tO NO LL O D es • O no NNp N p. O N P ¢1 tO Ni R' (.o.b) v.O r M M F ..4O O 6 O O O O - N .4 O W IC O 0 0 0 ry 0 0 N O N M 0 O 'dd3OO ddONf121 `52.. 0 0 0 0 0 o 0 o 0 0 0 0 0 (sand yaw 2 2 in .O. 1 p 1!1 2 in O m 2 p0`. in u'0 , o ei t 0: .4 .4 .4 c u: u; c 0 NOIlVNOIS3O V32N 5 ''4 NO N N N- O N a 'RIO Al p ;1,1 y 1NIOd NOIS3O- r cii tN titN N N 9 4 N 1 N S o N t N 9 c n F z U' Y m in Y Y 'Q v Y a I\ W _ 4,' Z a 0 m •?. V Y u Y ytj Y 2 Y 2 _ 2 a cc v zg u •• 3 » ti 2^ p 4 p 'e a o w' 8 w 3 O w 3 a' 0 B x z a' Ein 3 2Hu 10 W O ^ s Ai n _ no o - J 0 J tp y 2 Y a LaN atI M 5 N q N .� x C Z P Y P. a Y L E Y ~C a 5 al Eie S . E;= I0o Y Y _ LL A LL ,st° LL 8 .A 'E LL ~ LL U W W i W g O '"- LL IL A 0 N N n O N Q a A OOY (MW) 11 E ry n ^ ^ .- 6 'o a O i F E W (Sold) AL0013A CS o 0 0 0 o N o 0 t in M s g a o.N ("lol) H1ON3l v n N �X • a -Yia`8 v ;ZS&did _ w n (%J 3dO1S _.. (Sd0) MO1d NOIS30 `g — 1 sd0) MOId 1332LLS _', cc- F- (%J 3dO15 b N N e N o e M M ml OiNY a) u- 0 j ZS in(0V1 Itl.o)runs `v til a M '& h M SN' p Y LL a N n to P IA rnON R Ni" 13 O (ato ~Mi) I N N N N N Ni R F - 13 6 tY '0 V1 V N .4 ..- C (NW �l a m N N 6 .4 .4 .. N N ID N b N on 03 0 MN N 0 0 "' Cl N in N w in Cl (Solo) O ri b .i .Ni .Ni w a .i N e IC w m — M In 06 M N N .N4 'Y N N VD In IY (NHMI) I ?,, m o o e d M v In N M V Yf N N N Cr; M M M N M co O O M O t0 o t0 N N CO N O ('No) of - Di IA m a - a 2 m e 2 a n 2 — LL m p p i bew y.0 a < N m N N 0 m Q N N N N N N N O M M O O O N Yf 0 — w rc ° 'old&oo ddoNna 6 6 6 S a 6 6 a * a G a a C C C 6 6 6 a O 6 a 6 (sWaV1 tl321tl N_. 9i n o2 m E In o 0 m n m m 6 Oi O W T P .-i ti .4 M N H 01 to X _ Nco NOIIVNOIS30 tl32N ^.. O - N N N N.O N ry N N N rca o oN 0 0 N 1NIOd NOIS30 a B NL N L {N� N V )i LyN arn„ N Ii F Z ^ o Y a C Y V a 9 t W 8 Z Y C ZO Y \ L O V Z OI Ill N G K fr u P. 0 . N 0 Ill O a w w ww 8 Iu U z Y a u 0 0 0OU Hello