Presentation on theme: "Stormwater Systems ARCH-433. Attendance This water closet, installed in Pullman, Washington, flushes in a counterclockwise rotation. In what direction."— Presentation transcript:
Stormwater Systems ARCH-433
Attendance This water closet, installed in Pullman, Washington, flushes in a counterclockwise rotation. In what direction would the water rotate if it is installed in Sydney, Australia?
What You Need To Know Understand how and why stormwater systems operate Know the differences between stormwater and sanitary systems Strategies available for reducing potable water use LEED credit points associated with a reduction in potable water use
What You Need To Be Able To Do Predict stormwater drainage problems Be able to sketch a stormwater riser diagram Correctly size a stormwater system Calculate the amount of stormwater available for non-potable uses Make management decisions on the use and implementation of stormwater systems
Terms Stormwater systems Roof drain (RD) Overflow system (OFL) Leader Flow control roof drain Downspout nozzle (DSN) Imperviousness Stormwater Harvesting Area Drain
Purpose of Stormwater Systems Collect stormwater from the roof and move it to a point of disposal away from the foundation Collect stormwater from the site and move it to an approved point of disposal
Difference Between Sanitary and Stormwater Systems Absence of volatile gases No traps required No venting required Point of disposal varies
Stormwater Discharge Points Grade Municipal storm sewer system Street Stream, river, lake, ocean or other suitable point Yes BUT, is this really what we want! New Code Requirements
Stormwater Systems Roof drain systems Flat roofs Pitched roofs Site systems Q flow = Area (acres) x C R x I R = Ft 3 /Sec
Roof Drain Systems Pitched Roofs Gutters and leaders Flat Roofs Roof drains Overflow drains Flow control systems
Flat Roofs Advantages? Disadvantages?
Strategies - Roof Design
Strategies – Roof Design
Sizing Stormwater Systems Variables for commercial roof drain systems Area of the roof Rainfall rate Number of roof drains Slope of piping Variables for residential gutter systems Area of the roof Rainfall rate Number of gutters Slope of gutter
What about Parking Structures Floor Drains Poor Design Consideration Designed by an Architect Designed by an Engineer Concrete rot Repairs
Roof Drains in a Flat Roof
Rainfall Rate (Table 8-15)
Pipe Capacity (Table 8-16)
Overflow Drain Systems OFL RD 2” DSN Beware of shortcuts!
Overflow Drain Systems Required by virtually every code Prevents overloading of the structure
Overflows Can also use scupper drains Advantages Disadvantages
Strategies - Flow Control Roof Drain System
Siphonic Drain Systems Air Baffle
LEED SS Credit 6.1 Credit 6.1 Option 1 – Existing Imperviousness is ≤ 50% (undeveloped sites) Implement a stormwater management plan that prevents the post development discharge rate and quantity from exceeding the pre- development levels or: Implement a stormwater management plan that protects receiving stream channels
LEED SS Credit 6.1 Credit 6.1 Option 1 – Existing Imperviousness is ≤ 50% (undeveloped sites) Protect stream channels from excessive velocity
LEED SS Credit 6.1 Credit 6.1 Option 2 – Existing Imperviousness is ≥ 50% Implement a stormwater management plan that results in a 25% decrease in volume of stormwater runoff from the two-year, 24 hour storm
LEED SS Credit 6.1 Credit 6.1 Option 2 – Existing Imperviousness is ≥ 50% Bioswales Cisterns, holding ponds Green roofs Rainwater harvesting
LEED SS Credit 6.2 Credit 6.2 Implement a stormwater management plan that reduces impervious cover, promotes infiltration and captures and treats stormwater runoff from 90% of the average annual rainfall using acceptable best management practices (BMP) Remove 80% of the average annual post Total Suspended Solids (TSS)
LEED WE Credit 2 Credit 2 Reduce the use of municipally provided potable water for building sewage conveyance by at least 50% or Treat 100% of wastewater on site to tertiary standards
Water Reduction Strategies Use of Stormwater/Grey water to: Flush water closets and urinals Water landscape Avoid non-native plants Reduce the amount of water flowing across site
Carpenter How much stormwater (clear water) do we need? ? gals per day to flush low flow water closets How many work days per year?
How Much Rainwater is Available? Based upon.62 gallons/inch/sq. ft. Efficiency varies between 75% and 90% V collected = Rainfall x Area x Efficiency x.62 gals/inch/sq. ft. Source: Texas Manual on Rainwater Harvesting, 3 rd Edition, 2005
Rainwater Harvesting Capacity Source: National Oceanic and Atmospheric Administration, Department of Commerce
Calculating Water Storage
What is Wrong with this Picture?
Strategies Two 7,500 gal tanks installed to capture rainwater Rainwater is filtered with a recirculation system and used to flush water closets Capture system reduces stormwater discharge