Drainage Solutions

Once you know what is causing your drainage problem, you can start looking at solutions to resolve the issue. It is possible that you will need several solutions because a jobsite may have multiple drainage issues, especially if the project is on a large plot of land. The goal is to design a solution that will prevent issues anywhere on the jobsite, and then to implement the solution to minimize disruption or damage. 

As mentioned in our Drainage Design article, nearly all drainage solutions require a combination of surface and subsurface systems.

This type of pipe provides the benefits that are lacking in corrugated pipe. They are easier to clean and help establish a more consistent slope on bumpier surfaces. Since they need to be welded or glued together, this type of pipe offers a watertight solution if it is needed at a particular jobsite. 

However, it takes more time to install and is more difficult to work with than corrugated pipe.

Surface Drainage

As covered in the Drainage Design article, there are a number of considerations that must be made prior to installation.

Trench drains effectively collect excess surface water from non-porous surfaces such as parking lots, sidewalks and pavements. These carefully designed structures provide a continuous path of surface drainage, directing gathered storm water to a collection basin for treatment and an outfall.

For many years, concrete contractors had to meet these design requirements by hand-forming trench drains. This is a labor-intensive process requiring great layout skill and construction experience. Contractors must be knowledgeable in selecting the proper grate size and setting, designing the structure for its anticipated loading, and plan for all the hook-ups to adjacent drainage devices.

Hand-formed trench drains can also present service life issues. When ordinary concrete is exposed to ponded storm water containing deicing, the surface can experience spalling. Hand-formed trench drains can be difficult to construct on sites with small footprints.

And hand-formed trenches lack a finished architectural look. The trench’s grates can be uneven and cumbersome.

Modular Trench Drains

To address these site and operational concerns, architects often specify modular trench drains. A modular trench drain is a factory-made assembly.  The system includes: the channel with grate through which the storm water is directed to a catch basin or outfall. Modular trench drain assemblies come in a wide array of channel shapes and sizes, grate materials, and connection devices allowing the design professional to meet the drainage requirement on all types of projects.

Modular trench drains are factory cast with polymer concrete, which is a mixture of synthetic resin, mineral aggregates, and curing agents. This hardened material is very durable, providing long service life. The polymer concrete is also easily cut on the job site using standard powered hand tools.

Catch Basins & Outlets

Building a complete drainpipe system goes beyond just channels and grates. You also need to properly route all outlets to the correct plumbing pipework, either through direct pipe connections or through catch basins. In fact, a complete drainage system often includes:


A catch basin's main job is to capture water from trenches on properties and streets, and channel it to local waterways through a system of underground pipes. Catch basins are usually positioned at the end to a trench, but depending on the location of the underground pipe, and land topography, they can also be positioned anywhere along a trench run to channel water underground.

Sub-Surfaces

The traditional definition of subsurface drainage is the use of gravity to remove liquids in the soil. The most common causes of subsurface water are precipitation and irrigation. 

Sediment, sand, and other particles create the biggest challenge as they can clog the system. With reduced water movement, leaks could form, reducing the lifespan of the system. Another problem is the oversaturation of soil, which will reduce water flow to the water table.

 

French Drains

A French drain, (aka: a curtain drain, perimeter drain, weeping tile, or agricultural drain) serves to direct surface water away from specified areas, such as a structure’s foundation. French drains are trenches filled with gravel that direct surface water to the lowest point where it can exit through a perforated or slotted pipe. The gravel also catches any excess debris.

These drains are unique, in that they collect water along the entire length of the drain, as opposed to one spot. They are also effective in preventing surface pooling as they can direct water to dry wells or other more suitable discharge points. Drain pipes are usually corrugated or perforated and made of PVC or HDPE. 

A French drain is useful in solving drainage problems for:

 

Sheet/Composite Drainage

Composite drains are prefabricated drain systems. The sheets are then directly attached to more traditional pipes. The primary purpose of this type of drain is to create a barrier to groundwater.

A single-sided sheet drain is a geospacer drainage solution consisting of a formed, polymeric core and a laminated geotextile on one side. 

Applications include vertical and horizontal installations requiring full or discrete coverage. These drains are a cost effective, engineered solution for subsurface water management from one primary direction. Rolls are typically available in 4-ft, 6-ft, and 8-ft widths.

A double-sided sheet drain serves a similar purpose, with a laminated geotextile on both sides. They have the added benefit of managing subsurface water from one primary direction and one secondary direction. Rolls are typically available in a 4-ft width.