Description: A variety of above and below ground devices designed to improve the quantity and/or quality of stormwater exiting a site and entering the stormwater drainage system. Facility types found in Durham include level spreaders, sand filters, bio-retention areas, underground storage, Filteras, detention basins, constructed and pocket wetland, and wet and dry ponds.
Description: Inlets, outlets, and junctions designed to control the flow of stormwater runoff. Structure types include combination, curb, drop or slab inlets, headwall and end sections, junction boxes, and manholes. Some structures, such as weir boxes and riser pipes are predominantly associated with stormwater control facilities. Pipe transitions represent locations where a pipe connects directly into another pipe or into a larger open structure, such as an underground storage SCM.
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Value: COMBO INLET Label: Combination Inlet Description: Also referred to as a Catch Basin or Combo Box, this structure is an inlet that includes a grate and is built into the curb and gutter section of a street. Symbol:
Value: CURB INLET Label: Curb Inlet Description: An inlet built into the curb of a street. It does not include a grate, but may have a very long throat. Symbol:
Value: DROP INLET Label: Drop Inlet Description: Also referred to as a Yard Inlet, this structure is an inlet that is flush with the ground and consists of a large grate. Symbol:
Value: END SECTION Label: End Section Description: Locations where the stormwater system “daylights.” End sections may be at either the top or bottom of a stormwater network. End sections may just represent the terminal end of a pipe or they may be a specifically designed structure, such as a flared end section. Symbol:
Value: FILTERRA Label: Fil-Terra Description: Essentially a large curb inlet with a precast box which contains engineered soil material to filter incoming stormwater. Filtered water is piped to a nearby catch basin (the downstream catch basin also serves as an overflow device). An explanation of how a filterra functions can be found here: https://durhamnc.gov/DocumentCenter/ Symbol:
Value: HATCH Label: Hatch Description: Often referred to as a Bilco hatch or Bilco door, is a structure associated specifically with underground SCMs. A hatch allows access to the SCM and is a large, metal door flush with the ground. The image below shows two hatches associated with an underground storage SCM at the North Carolina State Employees Credit Union at 3872 Guess Road. Historically we have used “Manhole” to capture this type of structure and will at some point need to manually review manholes associated with SCMs to see if they should be recoded as hatches. Symbol:
Value: HEADWALL Label: Headwall Description: Also referred to as End Walls, these structures are locations where the stormwater system “daylights.” Headwalls may be at either the top or bottom of a stormwater network. Headwalls come in several designs including the wingwall and L-wall. Headwalls are often, but not always, associated with culverts and SCMs. Symbol:
Value: JUNCTION BOX Label: Junction Box Description: Structure where two or more pipes meet. Junction boxes are not accessible and new construction will not include any “true” junction boxes. Any junction box that is accessible through a manhole should be coded as a manhole. Symbol:
Value: MANHOLE Label: Manhole Description: Junction boxes that can be accessed through a manhole where two or more pipes connect. If the digital submittal data indicates that they have installed “junction boxes” check the imagery and the construction drawing details if these are actually manholes and, if so, set the Type to Manhole. Symbol:
Value: MINOR DRAIN Label: Minor Drain Description: Minor drains will typically be connected to “minor pipes.” Attribution of minor drains is minimal and minor drains are only included in the stormwater system if (a) the data is provided by the engineer as part of the digital submittal or (b) there is a special request within the Public Works Department to include this infrastructure based existing drawings or field work. Symbol:
Value: PIPE JUNCTION Label: Pipe Transition Description: This is an implied junction where two pipes are connected without a standard structure. Symbol:
Value: POSSIBLE Label: Possbile Junction Description: This type only used when the nature of the connection between two pipes is truly unknowable. In other words, when even a field visit to the site does not allow the editor to determine the nature of the connection. Possible junctions should only be created on occasions where the editor is conducting investigation regarding, or is otherwise notified by Public Works staff about, potential unrecorded infrastructure. Symbol:
Value: RISER PIPE Label: Riser Pipe Description: An inlet pipe that is designed to remove water from a stormwater control measure. Typically, a riser pipe has a small diameter opening near the base so that during lower flows water leaves the SCM slowly, but during higher volumes more water can leave the SCM. Riser Pipes are typically connected to a 15 or 18 inch reinforced concrete pipe that terminates with an end section. Riser pipes can be found in dry ponds, wet ponds, constructed wetlands, and bio-retention ponds. Symbol:
Value: SLAB INLET Label: Slab Inlet Description: Also referred to as an Open Throat Catch Basin (OTCB), this feature consists of a large inlet covered by a, typically concrete, slab elevated above the surface by several inches. Stormwater flows across the ground and enters the inlet through the gap, a.k.a. throat, between the slab and the ground. Access into the slab inlet may be possible through a manhole set into the concrete top. The below-ground structure may be made of brick, concrete block, or concrete and may be round or rectangular. A slab inlet may be at the top of a system or it may have upstream pipes that carry stormwater into the structure and then continues downstream. Symbol:
Value: WEIR BOX Label: Weir Box Description: A structure designed to control the speed at which stormwater leaves the structure. Weirs have an interior wall. If the water level is lower than the wall, then the stormwater exits slowly through a small opening at the bottom of the wall. If the volume of water is in excess of the interior wall, then the excess volume flows over the wall and exits the system more rapidly. Symbol:
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Description: Drainage areas for the principal named streams in Durham County that have been modified to take into account the effect of the stormwater system on drainage boundaries. Similar, but not identical to, the watershed layer that is part of the USGS Hydrography group layer.