“Complete identification, locations of and mapping of
stormwater drainage system components. At a minimum, mapping components
include outfalls, drainage areas and receiving streams.”
The purpose of the storm sewer system map is to give
the Phase II communities a basic awareness of their storm sewer systems.
Once the map is established, it can help Phase II communities determine
the possible sources of dry weather flows and identify which waterbodies
these flows may be affecting. The storm sewer base map could be an
existing map, such as a topographical map, which clearly shows the
locations of major pipes and outfalls.
As you begin working on your storm sewer base map,
you should audit the coverage and quality of mapping resources available
to support the IDDE program. You should see if a Geographic Information
System (GIS) exists and what digital mapping layers it contains.
If your community does not have a GIS, you have three
- Establish one (which can be quite expensive),
- See if a nearby larger local government will share
their GIS capabilities with you, or
- Rely on available hardcopy maps.
GIS and hardcopy maps are frequently available from
the following local agencies:
- Tax assessment
- Public works
- Parks and recreation
- Emergency response
Your initial storm sewer map should include all
existing information on outfall locations as available from the agencies
listed above. Then as you conduct stormwater outfall inspections (see
Measure 3d), you will field verify the locations of the outfalls and make
corrections to your storm sewer map as needed.
For an example of a mapping project in a Phase I
community, see the
City of Greensboro’s Stormwater Infrastructure
Greensboro is working on a big upgrade from its current hand-marked storm
sewer maps. The Stormwater Infrastructure Inventory will include: (1)
determination of the location of each structure; (2) collection of
structure attributes; and (3) development of a Geographical Information
System (GIS) database that includes all of the information on the storm
water conveyance system.