Standard Drain

The city has a set of standards it provides to engineers designing capital improvement in the City. The street and drainage improvements are usually combine with the water and sanitary sewer improvements to result in minimal pavement replacements. The specific purpose is to provide information required to prepare construction plans for the City’s capital projects. The design standards cannot separate street design from the drainage design because the street is a significant part of the drainage system.

The closed underground drainage system of a street is generally designed to a storm frequency based on rainfall intensity and flow concentration. The design varies based on peak runoff conditions and infrastructure type being built, but ultimately the goal is for the total right of way to be designed to handle the 100 year storm. The design of the street should have the edge of the right of way below the first floor elevation of the buildings along the street. The sidewalk and tree lawn should have a grade that runs towards the street. The curb allows the flow off the tree lawn and into the gutters which deliver the water to the closed underground system. The street pavement is also designed to move the water to the gutter and to the closed underground system. If the storm intensity and concentration exceeds the closed underground system, the right of way, the area from property line to property line will hold up to sixteen inches of water at the streets low point.

The design generally has an overland swale in the low area that will deliver water exceeding the right of way capacity to an open drainage system. The open systems in the City are generally detention ponds, ditches, the creek or lake.