Introduction
Storm Water Management
Storm Water Design Components
Landscape Design Components
Specimen Code Picture Gallery Links
References & Resources

 
 
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
 
 
 

 

Infiltration Trench

Infiltration trenches are excavated into the ground either horizontally or vertically and filled with stone aggregate used to capture and allow exfiltration of storm water run off into the surrounding soils from the bottom and sides of the trench or well.  Infiltration temporarily store storm water runoff and discharges (exfiltrate) it into the surrounding soil according to the percolation capacity of the soil horizons. This type of infiltration structure is used to remove pollutants and to infiltrate storm water back into the underground water table or aquifer.  The exfiltration also helps to reduce increases in both the peak rate and total volume of run off caused by land development. Pollutant removal is achieved through filtration of the run off through the stone aggregate and soil as well as biological and chemical activity within the soil. This type of BMP called a French drain in Louisiana can be fitted with an outflow is soil types warrant such treatment.

  

Calculations

Watershed Area

The one (1) inch design storm watershed area includes the building roof runoff drains to trench.

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

9605 Sq Ft x 1/12 Foot = 800.4 Cubic Ft

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

800.4 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

Infiltration Trench (BMP) Capacity

Square Feet x One (1) Foot = Cubic Feet

1350 Sq Ft x 1 FT = 1350 Cubic Feet

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

1350 Cubic Ft ÷ 27 = 50 Cubic Yards

Cubic Yards x Two Hundred Two (202) = Gallons

50 Cubic Yards x 202 = 10100 Gallons

Infiltration Trench Capacity = Gallons x 1/3 (assumption of space for water) = 3366.6 Gallons

BMP Capacity ÷ Watershed Area = BMP Percentage

3366.6 ÷ 5988.3 = 56% BMP Capacity for 1” Design Storm

1” BMP capacity design storm Gal ÷ 1” storm total property =

3366.6 ÷ 40736 =  8.2% BMP Management Factor

 

 

  

 

General Design Standards for Infiltration Trenches

Infiltration trenches or drilled columns can be used in extremely narrow spaces to soak up storm water flows at the flows at a proscribed capture rate (CR) determined by the Director of Landscape & Forestry. French drains constructed to a defined depth, width, and length can infiltrate water from a defined drainage basin such as a roof top, parking lot or grassed lawn.

Native soils are excavated and replaced with an improved soil mixture column composed of three (3) parts medium aggregate, four (4) parts coarse sand, three (3) parts fine aggregate and two (2) parts of coarse stone over an existing subsoil base, backfilled exactly in reverse order. A growing medium of sandy loaming soil can cap the top of the trench to a level of six (6) to twelve (12) inches for the purpose of planting turf grass or shrubs. Minimum width of the infiltration trench shall be thirty-six (36) inches and maximum depth shall be thirty-six (36) inches. The top of the drain may be surfaced with decorative river rock or one (1) inch of garden loam topped with on and one half  (1 1/2) inch layer of turf grass sod.

 

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