French drain

Reduce Head on Liner and/or in Leachate Collection System Inspect Leachate Collection/Removal System or French Drain Repair Leachate Collection/Removal System or French Drain Temporary Cap... 

The French drain (also called a channel drain or floating slab) is a construction feature that appears to provoke strong reaction from its defenders and detractors alike. French drains are only a concern in basement foundations. This slab detail is a standard feature in new houses in parts of the country as varied as New York and Colorado, but in other places it is virtually unknown. French drains are used in areas with expansive soils, such as parts of Colorado, to protect the slab from damage if the wall moves. In central New York State, the main function of the French drain is to drain away water that may seep down the walls. One national builder has discontinued and now prohibits the use of French drains in houses because of the potential for radon problems. This builder states that French drains also have been found to significantly increase indoor moisture levels. 

It is recommended that French drains be avoided if possible because of the difficulty in sealing them at the time of construction and the expense and difficulty of sealing them after construction. 

FIGURE 31.14 Sealing a French drain. (Adapted from U.S. EPA. Radon-Resistant Construction Techniques for New Residential Construction—Technical Guidance, EPA/625/2-91/032, U.S. Environmental Protection Agency, Washington, DC, February 1991.)... 

The term passive interception is used to describe recovery systems that rely upon natural groundwater flow to deliver free-phase NAPLs to the collection facility without the addition of external energy (such as pumping). These systems often include linear interception-type systems such as trenches (or French drains), subsurface dams ( funnel-and-gate structures), combined hydraulic underflow with skimming, and density skimming units. 

Construction of a subsurface structure that penetrates the water table only a short distance can be an effective LNAPL retention technique. Most underflow structures function in the same way as a surface baffle in an oil water separator or a septic tank. The structure must be carefully installed perpendicular to groundwater flow, and have some arrangement to collect the free-phase LNAPL. Often, a simple French drain (constructed parallel to the retaining wall) leading to a recovery well (with skimmer) is effective. A schematic diagram of a hydraulic underflow structure with a skimming unit is presented in Figure 7.3. 

Variations of linear interceptors include closed trenches that are backfilled with highly permeable material or contain a conduit pipe (classic French drain). When set slightly below the yearly low water table elevation, a French drain can serve as an effective interception device (Figure 7.6). 

The large crushed rock from the crane pad was pushed into the Lagoon to provide the porous drainage area of the french drain. In order to ensure absolutely free drainage to the monitoring/recovery well, a 24-inch wide perimeter trench was excavated in the crane pad... 

N (1106-N) Chemical unloading facility Unloading area for trucks and tank cars containing sulfuric acid or sodium hydroxide. Three abovegrour d sulfuric acid tanks, one aboveground sodium hydroxide tank and six french drains. 

N chemical unloading facility 120-N-7 unloading station french drain 120-N-6 sulfuric acid tank french drains 108-N neutralization pit UN-lOO-N-15 unplanned release UN-lOO-N-33 unplanned release December 26, 1987 unplanned release 120-N-5 acid/caustic trench and neutralization unit UN-lOO-N-34 unplanned release August 7, 1987 unplanned release September 2, 1987 unplanned release November 9, 1987 unplanned release 120-N-3 neutralization pit and french drain 120-N-8 sulfuric acid day tank french drain Regeneration waste transport system June 14, 1986 unplanned release June 30, 1986 unplanned release 124-N-l septic tank. 

N Chemical Unloading Facility. The 108-N chemical unloading facility was used for storage and transfer of 93 percent sulfuric acid and 50 percent sodium hydroxide solutions received by railroad tank car or tank truck. The unloading station french drain (120-H-7) was used for neutralization of small releases from the overhead transfer boom. The french drain was used from 1963 until March 1987 (DOE-RL 1990). The french drain was 0.9 m (3 ft) in diameter by 1.2 m (4 ft) deep and consisted of a clay pipe filled with lime (DOE-RL 1990). 

March 20, 1981 (UN-lOO-N-15) - Sulfuric acid and rinsewater were spilled inside the 108-N building. The unknown amount of liquid was transferred to the acid tank french drains for neutralization. The transfer line developed a leak and released acid solution to the ground. The affected area was estimated to be less than 4.6 m ... 

N-3 (163-N) Neutralization Pit and French Drain. The unit is a french drain and vault located immediately west of the 163-N demineralization plant. The unit was constructed in 1963 and is still in place (DOE-RL 1990). It serves as a spill containment unit for the two 38,000-L (10,000-gal) acid and caustic day tanks located immediately inside the 163-N building. A drain in the tank area leads to the unit. The vault is approximately 2.4 m by 7.6 m (8 ft by 25 ft) in size and approximately 2.4 m (8 ft) deep. The walls of the vault are constructed of concrete and the floor is unlined earthen material. Located in the vault is a 1.2- to 1.8-m (4- to 6-ft)-diameter french drain made of clay. The depth of the french drain is unknown. No liquid is currently present in the pit and french drain. 

N-8 Day Tank Vent French Drain. The unit is a french drain used to receive overflow of sulfuric acid from the 163-N demineralization plant sulfuric acid day tank. The unit is 1.2 to 1.8 m (4 to 6 ft) in diameter and consists of a clay pipe filled with lime to neutralize any sulfuric acid releases. It is located on the north side of the 163-N building. The unit was installed in 1963 and taken out of service on Hay Id, 1988 (DOE-RL 1990). 

N-7 Unloading Station French Drain 93 percent sulfuric acid and 50 percent sodiim hydroxide. French drain for receiving incidental spills during railcar or tank truck unloading. 

N-6 Sulfuric Acid Tank French Drains (5) 93 percent sulfuric acid. French drains surrounding acid tanks for containment of incidental spills. 

N-3 163-N Neutralization Pit and French Drain Sulfuric acid aixi sodium hydroxide. French drain and vault receiving drainage from 163-N acid and caustic day tank area. 

N-8 163-N Sulfuric Acid Day Tank Vent French Drain Sulfuric acid. Tank overflows are vented to the french drain. 

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