Traditional storm water systems are made up of structures used to collect runoff and convey that water to a nearby river or lake. The following elements that make up the City of Orem’s storm drainage system.

Catch Basins or Drain Inlets

These structures are where water goes from the surface to the underground pipes. The most common elements of these structures are the curbface inlet which is an opening cut into the curb with a grated inlet in the gutter. Catch basins are designed to have a depression below where the water enters the pipe. This allows for sediment to accumulate here.

Pre-Treatment Inlets or Oil/Water Separators

Pre-treatment inlets are drain inlets that are designed to separate water from some of the most common pollutants. Sediment and heavier particles settle to the bottom. Oils and other floating debris stay on the top while water from the mid section is discharged into the storm water drainage pipes or into a sump. You can use the following links to learn more about these structures.


These structures are 5-10 ft. deep concrete or corrugated metal cylinders with holes drilled into the sides. Sumps are designed to allow water to drain out into the subsurface soils. They are an effective way to disburse water.


Manholes are placed at regular intervals along storm drainage pipes to allow access for cleaning, maintenance and monitoring. They are also placed at location where two or more pipes come together. They are generally made of concrete or corrugated metal. Some manholes also have pre-treatment devices as discussed in the section about pre-treatment inlets.

Diversion Structures

There are some locations in our storm drainage system where it would be beneficial to choose which direction the water is going to flow. In these cases, we use diversion structures to affect the direction of flow. This is accomplished by opening and closing head gates. These structures can also be used to regulate the volume of flow passing the structure.


The storm water system has nearly 90 miles of underground pipes. They range in size from 12″ to 96″ in diameter and made of concrete, corrugated metal and high density polyethylene.

Channels or Ditches

The City makes use of a few ditches and channels to help aid storm drainage. The largest channel that takes Orem storm water is the Provo River on the east side of town and Lindon Hollow is the largest on the west side of town. Most of the channels and ditches in the main part of town are owned and operated by irrigation companies to supply water to orchards and gardens. These irrigation ditches usually carry very little storm water.


The end of the pipe or channel where water discharges into Utah Lake or a another water body that the City does not maintain like Provo River is called an outfall. Outfalls are important because they mark the transfer of responsibility from one governing agency to another. They also provide locations for water sampling that allow us to evaluate the quality of the runoff we discharge. If things are not they way we expect them to be, outfalls provide starting points to do investigation and find out why.

Detention Basins

Detention basins are depressed areas designed to take large amounts of water in and let the water out at a controlled rate. This allows the City to make use of smaller pipes downstream of the basins saving the City money on installation and maintenance of systems. Examples of detention basins can be found at the Skate Park at 400 North and 1200 West and Bonneville Park at 800 North 1600 West.

Drainage Swales

A swale is a vegetated, sloped depression that allows water to flow through, but at a slower pace than in other channels. the sub surface is constructed in such a way that it encourages infiltration to ground water.

Green Roofs

These specially designed roofs are meant to grow vegetation and allow water to be filtered by plants and soils before being discharged. There are not many of these in the City but we hope see some in the future.

Rain Gardens

A rain garden is a depression planted to take the runoff from a parking lot, road, driveway or roof top so that the runoff has a chance to be absorbed.