storm analysis and design prepared for riverton city 4/13/14 cgm consultants
TRANSCRIPT
Storm Analysis and Design
Prepared for Riverton City
4/13/14
CGM Consultants
Problem Statement
• Riverton City is a rapidly growing city in Salt Lake County.
• Many new subdivisions are projected for development in the upcoming years.
• To minimize construction costs, an
alternative storm water design has been requested by the city.
Scope
The results of this project are a preliminary analysis and design for typical subdivisions in Riverton City
Royal Farms is a representative subdivision found in Riverton City, and was used for the analysis in this project.
Royal Farms Subdivision
Royal Farms Subdivision is a 29.8 acre subdivision located East of Bangerter Highway.
Pre-Development Runoff
Time of Concentration: 10 minutesRunoff Volume: 5,500 ft3
Post-Development Runoff
Time of Concentration: 18 minutesRunoff Volume: 23,280 ft3
• Pre- and post-development runoff volumes from the 10 year
storm were analyzed using Watershed Modeling Systems (WMS).
• According to NOAA, The 10 year storm precipitation was estimated to be 1.24 inches of rainfall.
• From WMS, the pre-development runoff volume was found to be about 5,500 cubic feet.
• The post-development runoff volume was found to be 23,280 cubic feet.
• The low impact design (LID) for the representative subdivision must hold the difference of these volumes, or 17,780 cubic feet.
Runoff Comparison
Runoff Comparison
0 10 min
18 min
1 hr 2 hr 23 hr 24 hr 24 hr 10
min
24 hr 18
min
0
500
1000
1500
2000
2500
Pre-Development Post Development
Ru
no
ff [
cfs]
Pre-Development Runoff: 23,280 ft3
Post-Development Runoff: 5,500 ft3
Difference: 17,780 ft3
The DesignAutoCAD
Template
Used a file provided by Riverton City as our template
Parameters
Swale design◦Width◦Location◦Swale entry
Roadway design◦Traveled way◦Dividing side treatment
Swale
The design called for a swale with a width of 5.5 feet along the sidewalk
Swales are not to intersect with driveways
Meant for the roadway runoffHave inlets between driveways
Roadway
Between property lines are 54’29’ of designated roadway
◦2% grade on the normal crown and sidewalks12.5’ of side treatment on each side
◦Includes: Sidewalk 6ft Swales 5.5 ft Curbs 1ft
CAD Drawings
Ideal Lot
Typical driveway of 30ft width◦70% of properties have 30ft width, vs 16ft
Sidewalk adjacent to and leading to the house
Close up of Swale
Dimensions are in feet
5.50006.0000
Swale
Development
Swales added to every roadside
Before and After
Before and After
Cost Benefit Analysis
Cost Benefit Analysis
Simulated Development AgreementStorm Drain and Irrigation Cost Savings of 17% Non-Conservative
Limitations and Assumptions
Arbitrary Runoff Coefficient ◦Pre- versus Post- Land Use Criteria
1.8% Grade Sloping EastwardRational Method Verified
◦Approximated Using NRCS Curve Method Hydraulic Radius
◦0.375 ft for 18” pipe Cost-Benefit Analysis Errors
Evaluating Product Quality & Deliverables
Property/Easement IssuesHOA RegulationsPublic Nuisance Sand Filters
CGM Consultants
4.3.1 Graduate Student Advisor Adam Eccles, 713.838.5051, [email protected] 4.3.2 Faculty Supervisor Dr. Gus Williams, 801.208.3137, [email protected] 4.3.3 Project Manager Mason Adamson, 509.551.1565,
[email protected] 4.3.4 Design Team Leader Carter Livingston, 760.458.6449,
[email protected] 4.3.5 Engineer 1 Greg Sanchez, 609.865.5282, [email protected]