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Home My Public Portal AboutSMFRO&M_excluding calculationsAPPROVED FOR CONSTRUCTION M.S.D. PERMITS REQUIRED IN CONFORMANCE WITH THE MSD STANDARD DETAILS AND SPECIFICATIONS AND SUBJECT TO INSPECTION, FINAL ACCEPTANCE AND SUBMISSION OF FINAL PLANS CORRECTED FOR ACTUAL CONSTRUCTION, THE METRO. ST. LOUIS SEWER DISTRICT BY: ENG. MANAGER PLAN REVIEW BY: PLAN REVIEW ENGINEER DATE: 110 THE MEADOWS OF WILDWOOD CITY OF WILDWOOD ST. LOUIS COUNTY, MISSOURI STORMWATER MANAGEMENT PLAN WIND ENGINEERING JOB # 03084 +4311401411.11111 01' of MISsfr ?tom? •• .''� *�'�• DANIEL C. WIND, J . -.7.N NUMBER tin : E-19364 4 0,0 ...........•7 APR 0 4 2008 Prepared By: EN G I N E E R 1• N G C O M P A N Y 122 North Kirkwood Road Kirkwood, MO 63122-4302 Phone: (314) 965-8286 Fax: (314) 965-7592 February 20, 2004 REV: April, 4 2008 (MSD Submittal) 0 co MSD Submittal Note: The Stormwater Management Plan Report has been revised and updated for MSD submittal. Annexation and extension offsite public sewers has allowed the Meadows of Wildwood to connect and utilize sanitary facilities formerly stored on site a hauled off. The resulting revisions to plan and report have been prepared post sewer construction as approved per The City of Wildwood and have been revised to accommodate MSD requirements for stormwater detention. Specific revision includes calculation of the 100 - year low flow blocked model. Results have been attached to this report and low sill elevation requirements have been added to site plan. Introduction: The Meadows of Wildwood is a proposed residential development consisting of 53 attached homes together with an approximately 44,000 square foot clubhouse and tbd mid -rise building situated on a 19.30 -acre tract. The site is located near the intersection of Turkey Track Road and Highway 109, in the City of Wildwood, in St. Louis County. The following report has been prepared as a summary of the attached storm water management calculations. Existing Conditions: The site contains three separate one-story frame residences with a gravel/asphalt drive. The site has a combination of mostly open grass areas with some closely planted tree lines along the main drive. The west and south property lines border along a heavily wooded area. The site consists of three drainage areas, with water draining to the north, west and south. Drainage Area "A" contains 4.30acres and drains to a defined ditch at the western edge of the site. Drainage area "B" contains 3.80 acres, which includes a small portion of contributing off -site area, and drains to a defined ditch at the southern end of the site. Drainage Area "C" contains 8.50 acres, including the contributing off -site area to the east, and drains to the northern edge of the site. The following table summarizes the data and results for the drainage areas. All calculations and more detailed data can be found in the attached calculations. The methodology used for calculating all flows was the SCS methodology. The software package used for all analysis was PondPack v8.0, Haestad Methods. Drainage Area Area (acres) Curve Number Time of Conc. (hrs) 2 -Year Peak Runoff (cfs) 100 -Year Peak Runoff (cfs) A 2.90 63 0.3322 2.41 @ 12.150 hr 13.93 @ 12.100 hr B 3.80 63 0.5943 1.48 @ 12.300 hr 8.62 @ 12.250 hr C 8.50 63 0.5401 3.44 @ 12.250 hr 20.16 @ 12.250 hr Developed (Proposed) Conditions: The proposed development will include 53 attached residential homes, a clubhouse and associated roadway and sewer construction. A centrally located lake, having a surface area of approximately 46,000 square feet, is to provide the storm water detention for the site. The site will still have three drainage areas that drain to Outfalls "A", "B" and "C". A watershed break will occur ultimately decreasing runoff to Bonhomme Watershed (Lower Missouri). Drainage Area "A" will consist of three subareas. The "Overland" portion contains 3.27 acres and drains to the lake via overland flow. The "Piped" portion contains 7.76 acres and is sent to the lake through a system of storm sewers. The "Developed" portion contains 1.14 acres and is not detained draining directly to Outfall "A". Drainage Area "B" contains 1.52 acres and drains directly to Outfall "B". Drainage Area "C" contains 2.91 acres and drains directly to Outfall "C". The following table summarizes the data and results for the drainage areas. Drainage Area Area (acres) Curve Number Time of Conc. (hrs) 2 -Year Peak Runoff (cfs) 100 -Year Peak Runoff (cfs) Dev. A 1.14 73 0.1950 1.69 @ 12.000 hr 6.12 @ 12.000 hr Overland A 3.27 89 0.1096 8.68 @ 11.950 hr 24.13 @ 11.950 hr Piped A 7.76 89 0.0833 24.55 @ 11.900 hr 63.39 @ 11.900 hr B 1.52 72 0.4351 1.56@12.150hr 5.74 @ 12.150 hr C 2.91 70 0.5536 2.11 @ 12.250 hr 8.66 @ 12.250 hr Detention Analysis: The goal of the storm water management plan is to ensure that the peak runoff for the developed conditions does not exceed the existing peak runoff for a particular drainage area and watershed, for both the 2 -year, 24 -hour storm and the 100 -year, 24 -hour storm. A comparison of the developed and existing peak runoff values for Drainage Areas "B" and "C" show that the developed peak runoff is less than the existing peak runoff for both the 2 -year and 100 -year storm events. Drainage Area and Watershed Existing 2 -Year Peak Runoff (cfs) Developed 2 -Year Peak Runoff (cfs) Existing 100 -Year Peak Runoff (cfs) Dev eloped 100 -Year Peak Runoff (cfs) A Bonhomme Watershed 2.41 2.06 13.93 10.97 13 Hamilton Watershed 1.46 1.56 8.62 5.74 C Hamilton Watershed 3.44 2.11 20.16 8.66 Storm water detention will be provided for Drainage Area "A" by utilizing the proposed fake. A maximum of 3.89 feet of fluctuation in the surface elevation of the lake will be utilized to provide a storage volume. The normal water surface elevation will be 779.00, with the 100 -year high water level reaching 782.02. The lowest basement floor elevations of the surrounding homes and of the clubhouse has been set to 784.89, which provides a minimum of two feet above this highest water level. An outfall structure will be used to control the outflow of the lake to maintain a total peak outflow rate that is below the existing peak outflow rate for Outfall "A". The proposed structure will have a 4 -inch circular opening at an elevation of 779, and a weir at an elevation of 780.60 with a 1.25 -foot wide opening. The following table summarizes the detention basin inflow and outflow and lake elevations for both the pre and post -development conditions. Storm Event Basin Peak inflow (cfs) Basin Peak Outflow (cfs) Basin Elev. 2-yr, 24 -hr 32.79 @ 11.950 hr 0.49 @ 780.48 18.800 hr 100-yr, 24 -hr 85.98 @ 11.900 hr 7.09 @ 782.02 12.550 hr 100-yr, 24 -hr Low Flow Blocked 85.98 @ 11.900 hr 22.37 @ 782.89 12.100 hr Page 1 of 1 joevie1 c�res�� http://ims.missouri.edu/output/watershed319 dagobah4016532037.1pg 3/17/2008 Outfa ll B 5 7- - ,o_v /7 /e/Py1/7on/ ' Outfall A ♦ Existing A 2.94 Acres • ♦ *♦ Existing B ♦• 3.86 Acres ♦♦ ♦ Outfall C r I' 2 l',"4-3< 2 //7/,s -so 4 I'Z 0/1/l70% /t?7 \�` Outfall B Existing C 8.21 A cres • •. • 4. • • I I r I I I I I I TABU' . __SC .... .'ND F" FEA 5 ;The aerinitions of "floodi ng" and "wat er table " in the Gloss ary expl ain terms such as "rare," "brief," "apparent, " and "p erched ." The symbol < me ans less than; > means more than. Absence of an entry indicates that the feature is not a concern] Soil name and ) ;Hydro - map symbol ) logic ;gr oup 1B, 1C, 1D---,---- Winfield I B 2B, 2C, 2D, 2E, 2F Menfro B 3D, 3F ; B Cla rksville 4D Union 5A Iva 6A*, 7B*. Urban lan d 8E Go ss 10D*, 10F*: Ga sconade Ro ck outc rop. 12 Nevin 13D, 13F Go ss 14C, 14E Menfro 16C*, 16b*: Urba n land. Harve ster 17D*, 17F*: Crider Menfro 18A*, 18C*, 18D* : Urban la nd. Ha rv ester Flooding Fr equency I Durati on None N one N one C (None C (None 1 B 4 None 1 D ;None ) B ;No ne No ne B ;None B 'None 1 B (No ne B B B None None None See footnote at end of table. Ws in ; High wat er table r (Months I Depth I Kind ;Months I Depth 1 1 -1 Ft I ; I In i I 1 I -�- 12.5-4.0 Perched (N ov -Apr; >60 1 1 I I ; - ; >6.0 1 >60 I I I >6.0 , __- i >60 I i I I1.5-3.0:P erch ed Dec -Marl >60 ; I 1.0-3 .0;Apparent Jan-AprI 1 >6 .0 ) I I I >6 .0 1 12.0-4.0 1 >6.0 ) >6.0 I � 1 >6.0 I ; I >6.0 I ; >6.0 >6.0 >60 >60 I - 1 10-20 1 I I 3 Apparent; No v -Jul! >60 I ; --- 1 >50 >60 >60 >60 >60 Bedrock I I Risk of 1 IPote ntial; (Hardne ss; fro st Un coated ste el Hard >60 1 -_ ;High ;High IHigh 1 I a cti on ;High High ;Moderate Moderate ) High High c orr osion ;Concrete • Mod erate ;Moderate, L ow ;Moderate. Low !High. 'High. High Moderat e. Moderate ;Moderate Moderate ;High {High M oderate IHigh r I M oderate. ;Lo w. 1 !High ;Low. M oderate Moderate. ;Low ;M oderate. I I I 1 1 ; High )L ow ;Low. I , 1 1 ;Moderate ;Moderat e. I !Lo w ;M ode rate. 1 1 I I I , 1 , r ;Low ;Low . , 1 1 1 Outfall Ci•iiii N/F THE JUNIOR CO11i6E OIS TRJCT OF 51. LOIJ15 2411 ZONING= NU TNLCT A IESI1t LOT 7 NTdLEY ma DOWER OF jT. I-04116 11651,661 24613 ZONING, ZONING, NU T9T • 111 N Deve I Acres: I I 1 Tc Tc, • 1 r THIS SHEET IS FOR DRAINAGE AREA INFORMATION ONLY NOT FOR CONSTRUCTION YV: 6 y.T ay,g�I �g3� g�6.�'� 1, ya 41! /iigi f YL *4 REVISIONS WIND ENGINEERING C014PANT CD?Ulpol1T ►004 Ta mams am caws Art rimp atr.0 NUM PispLAL .,w 01/29/04 MWE RAW 03084 C,14 PAP P- THIS SHEET IS FOR DRAINAGE AREA INFORMATION ONLY NOT FOR CONSTRUCTION Existing A .33 Aeries I REVISIONS WIND ENGINEERING COMPANY COrTIIQNT 1004 v.(cowM wu wY4OM ur ry !MO IP�wi M M rt Oik N & 110�11L911(t� ri4,11! Mlles CGllfllt. R 01/29/04 a..,, of 'AWE '-Is foluribm RAW 03084 LOW FLOW WORKING Add lin k 30 0, C .0 Add link 20 w x Add link 10 w U 03 >� Add lin k 80 ❑ O m co Add lin k 70 1111 a 1 0 d 0