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Rain Garden
Rain Grove
Circular Depression
Planted Storm Water Buffer
Infiltration Trench
Sand Filter
Bio-swale
Porous Paving
Above Ground Cistern
Underground Storm Water Chamber
Preserved Wetland
Tree Protection Area
Habitat Protection Area
Riparian Buffer
Constructed Wetland
Parking Lot Detention
Grassed Swale
Vegetated Ditch
 
 
 

 

Underground Cistern & Storm Water Chambers

Underground storm water chambers are manufactured to be effective long-term storm water management systems. They are primarily used for landscape irrigation with gray water or to temporarily store and release at a predictable rate storm water flow. They are viable, low cost, low tech solutions to decentralized storm water drainage capture that has been approved by the EPA since 1997. If they are planned, designed, installed and maintained properly they become a very useful method of storing storm water on site. Nyloplast, ADS, Contech, Lane, Prinsco, Invisible Structures, Cultech, Storm Tech and Storm Trap are just a few of the manufacturer’s that build underground chambers out of pvc, polyethylene, corrugated steel or concrete. In many instances, underground chambers have been installed under parking lots to detain, filter and clean sheet flow from concrete, asphalt roof lines and other impervious surfaces. They can be adapted with special storm water treatment chambers to soak up oils and other human made petrochemical pollutants that are commonly associated with automobile parking areas of horticultural maintained turf grasses. A very simple system of storing water underground is an old fashioned farm drain system that uses perforated pipe in an underground pattern to dissipate and infiltrate storm water.

Ex-filtration beds of sand and gravel are used to soak up and filter any storm flows not leached back into the ground directly under the chamber line or bed. The filter medium is typically sand, but it can consist of sand, soil, gravel, peat, compost, or a combination of these materials. The purpose of the filter bed is to remove smaller sediments and other pollutants from the storm water as it percolates through the filter medium. Finally, treated flow exits the sediment filter system via an outflow mechanism to return to a storm water conveyance system or a permanent retention pond. Surface storage with sun light systems takes precedence over underground storage where possible.

 

Calculations

Watershed Area

The one (1) inch design storm watershed area includes the root top surface of the building.

Square Feet x One Twelfth (1/12) Foot = Cubic Feet

9605 Sq Ft x 1/12 Foot = 800 Cubic Ft

Cubic Feet ÷ Twenty-seven (27) = Cubic Yards

800 Cubic Ft ÷ 27 = 29.6 Cubic Yards

Cubic Yards x Two Hundred Two (202) = Gallons

29.6 Cubic Yards x 202 = 5988.3 Gallons

Watershed Area = 5988.3 Gallons in a 1” Design Storm

Underground Cistern (BMP) Capacity

Tank Capacity 10,000 Gallon Fiberglass Tank

Divided by total Gallons of One (1) Inch Design Storm

BMP Capacity ÷ Watershed Area = BMP Percentage

10000 ÷ 5988.3 = 166% BMP Capacity for 1” Deign Storm

1” BMP watershed design storm Gal ÷ 1” storm total property = 5988 ÷ 40736 =  14.7% BMP Management Factor

 

 

General Design Standards for Underground Cistern & Storm Water Chambers

Underground storm water chambers may be designed of any material including galvanized metal, reinforced concrete or synthetic compounds or any pre-manufactured containers adaptable to ground contact. This Facility shall be calculated based upon the size of the drainage basin in which water is collected to be stored or filtered prior to use or disposal. Individual storage vessels must be provided to allow collection of the design storm volume. Collect storm water for this facility from rooftops, parking lots, or other areas that can supply water that can be filtered to be used for landscape irrigation.

Maintain facility from time to time by removing solid waste that may collect within the individual storm water chambers, replace filters and pumps as necessary.

Click Here for more Technical Standards

 

 

Buck Abbey

309 Design Building
Baton Rouge, LA 70803
(O) 225.578.1475
(F) 225.578.1445
LSUGreenLaws@aol.com