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## EXAMPLE PROBLEM 378 & 410 GSS

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**TRAINING OBJECTIVES**• Be able to flood route a 378 pond and design a pond without and with a pipe.**AUX. SPLWY.**PERM, POOL INLET CHANNEL CREST AUX.. TOP DAM EXIT CHANNEL TAILWATER ELEV TOP DAM-FBH +Freeboard DESIGN FLOW (SDH) CREST AUX. FBH SDH PSH PERM. POOL CONDUIT TAIL- WATER TAIL- WATER CREST PS**SITES 378 PROBLEM**A. GIVEN: Drainage Area = 103 acres. Hazard Class = A1 RCN = 72 W/S length = 987’ with a slope of 2% Auxiliary Spillway Crest=Permanent Pool @ Elev. 103.6feet. No principal spillway Valley Floor Elevation - 88 feet**Structure Data**Elev. (ft)Surface Area (Ac.) 85.5 0 89.5 0.3 96.4 1.2 100 4.8 104.3 10.8 106 11.8 107 12.4**Rainfall: Design FBH = 8.95”**Rain distribution: Read in a 24-hr duration, rain table No Principal Spillway Auxiliary Spillway located at 103.6 EL.**T = Total Hydraulic Stress – lb/ft2**T = Vegetal Stress + Effective Soil Stress T = Tve +Te Auxiliary Spillway has a CL material with PI=15 Allowable effective soil stress=0.05 lb/ft2**DAM CENTERLINE**Centerline Dam Valley Profile Data: Station (ft.) /Elev. (ft.) 0/107 26/106 69/104.3 99/103 133/100.8 163/99.6 193/98.4 223/96.9 253/96.4 283/93.6 321/89.5 371/94 401/95.2 421/95.8 451/96.9 491/103.3 521/107**Embankment Data:**Top Width = 12’ Upstream side slope = 4:1 Downstream side slope = 4:1 No Wave Berm Width No Stability Berms Crown = 0**Auxiliary Spillway Data:**We want to do a Stability & Integrity Analysis of the Spillway. You set the crest at 103.6 Station at DS end of Crest = 620 Inlet length of the auxiliary spillway is about 230 ft. Profile or spillway inlet template data (x,y) (distance, drop): 50’/0’; 280’/3.0’ Bottom Width: 30 feet Spillway sideslope = 3:1 Spillway slope 3% (constructed exit channel)**280’**Tie-in Station 6+20 50’ 3’ Inlet Spillway Template Z = 3:1 BW = 30’**Spillway Geology and Vegetation Data:**Material in spillway - Clay (CL) PI or (lw) = 18 The representative soil particle size D75 = 0.0024 inches Percent Clay = 28% (in material in spillway) Dry Density of the clay = 92 pcf Headcut Erodability Index = 0.1 Vegetative Retardance Curve Index = 5.6 (Inlet) Vegetative Retardance Curve Index = 5.6 (Outlet)**Assume 2 foot (2’) of rooting depth in spillway**One foot (1’) of topsoil will be installed in the constructed channel. CL-PI=15 The topsoil D75 is 0.02”. Cover Factor (assume good) bromegrass = 0.7 - 0.8 Maintenance Code (assume good in constructed ) = 1 Maintenance Code (assume minor irr. in natural ) = 2**Coordinates of top of material: Sta. (ft.)/ Elev. (ft.)**100/85; 310/95; 410/106; 500/107; 700/106; 750/100; 930/95; 960/90; 1000/84**Erosion resistant soil @ 3% exit slope.**Allowable velocity = 7.0 fps.**Smooth Bromegrass is a cool-season grass introduced into**the United States from Hungary in 1884 -This leafy and sod-forming perennial spreads aggressively through both seeds and rhizomes. It grows 15 to 30 inches high and flowers during late spring and early summer in an open panicle.**T = Total Hydraulic Stress – lb/ft2**T = Vegetal Stress + Effective Soil Stress T = Tve +Te Allowable Vegetal Stress=Tva = 0.75 Ci Ci = Retardance Index @ Ci = 5.6 Tva = 4.2 lbs/ft2 - Allowable vegetal stress Ta= Allowable Total Hydraulic Stress=4.2 + .05= 4.25 lb/ft2**PART A**FIND: Save Separate Files 1. Is this an acceptable pond design without a pipe? Y / N A. Top of Dam= _________ EL. B. Settled Volume= ____________ CY 2. Remove all vegetation. (HINT-n=.0156. For fine-grained, cohesive soils, the value of n is taken as 0.0156) Is this an acceptable pond design without a pipe? Y / N**PART B: Use PART A input as a start.**This pond has gullies in the upstream area of the pool. Need to design a GSS for this site. Permanent Pool @ Elev. 100.0 ft. This will cover headcuts with 2.0 ft. of water. Crest of principal spillway = 100.0 ft EL. Volume of sediment between principal and aux spw = 0.0 AF. Rainfall: PSH=1 day = 7.5” Principal Spillway Data: (Single Stage Circular Conduit) Number of Conduits = 1 Length of Conduit = 114 feet Diameter of Conduit = 12” Conduit “n” = 0.013 Ke = 1.0 HGL at outlet of conduit = 89.5 feet. Riser weir length = 6.28 feet. (24 inch dia.)**No Wave Berm Width**• No stability Berms • Crown = 1.0’ • Auxiliary Spillway Data: • We want to do a Stability & Integrity Analysis of the Spillway. Let the program set the crest of the auxiliary spillway. • What is the Auxiliary Spillway Crest (ASC) _________EL. • What is the Top of Dam (TOD) ____________EL. • What is estimated construction volume ________CY. • What is effective soil stress_____________lb/ft2. • What is the integrity distance for the spillway analyzed.**Part C Use Part B file as a start**• Rainfall: PSH=1 day = 7.5” • Use a Hood Inlet with same diameter and pipe length as the pipe drop. • Distance to bend 100’ and bend to outlet 14’. • The elevation of the bend is 90 and the outlet is 89. • Say the Mannings “n” = 0.013 • Circular weir coeff. -- 0.6 • Entrance coeff. -- 1.0 • What is the Auxiliary Spillway Crest (ASC) _________EL. • What is the Top of Dam (TOD) ____________EL. • What is estimated construction volume ________CY.**Part D Use Part B input file as a start**Add stability berm on the down stream side at 5’ with 25’ top width. Add a wave berm width =20’ on the front slope. 1. What is estimated construction CY?.**Management of files**FOLLOW ALONG Right Click on the Start button, and Select Explore.**1. Type “SITESWorkshop” and enter**2. Exit Explore**1. Left Click the Start button/All Programs/Engineering**Applications/SITES/SITES 2005**File / New Project**Locate SITESWorkshop and Double Click**File / New Project**TYPE EX1 Click OK**File / New File**File/New File**File / Save As**File/Save As Click Save**Navigating in SITES**• Home Screen • Schematic • Input Screens**Schematic**• Editing File • Dbl-click element to edit**Input Screen -Typical**• Editing data element on schematic**File / Continue**File/Continue**Enter Data /Next Screen**4. Class (a) dams that have a product of storage times the effective height of the dam of 3,000 or more, those more than 35 ft in effective height, and all class (b) and class (c) dams shall meet or exceed the requirements specified in Technical Release No. 60 (TR-60).**Watershed Schematic**Click to Add Structure**Watershed Schematic**Double Click to Add Data For This Structure**Watershed Information**Input Data and Click**Structure Data Table**InPut Data and Click**Watershed Data**NRCS Curve Number Method Input Data and Click**Rainfall Data**Input Data and Click**Rainfall Distribution Table**Click Open**Rainfall Distribution Table**Input Data and Click