Volume 2-05, Chapter 3 - City of Wichita

Section 3.3.3 - Alum Treatment
• Total Nitrogen – 60%
• Heavy Metals – 75%
• Fecal Coliform – 90%
3.3.3.3 Design Criteria and Specifications
Alum treatment systems are fairly complex, and design details are beyond the scope of this
manual. However, further information can be obtained by contacting local municipalities and
engineers who have designed and implemented successful systems. The following are
general guidelines for alum treatment systems:
• Injection points should be 100 feet upstream of discharge points;
• Alum concentration is typically 10 μg/l;
• Alum treatment systems may need to control pH;
• For pond design, the required size is approximately 1% of the drainage basin size, as
opposed to 2-5% of the drainage basin area for a standard detention pond;
• The local jurisdiction may require that the facility be placed in a reserve and/or
establishment of a drainage easement the facility, which is accessible from a public road
or other accessible easement. When required, the drainage easement should be at least
20 feet wide, provide a minimum traversable width of 15 feet, have a maximum slope of no
more than 10%, and be appropriately stabilized to withstand maintenance equipment and
vehicles.
3.3.3.4 Inspection and Maintenance Requirements
Regular inspection and maintenance is critical to the effective operation of stormwater
management facilities. An operation and maintenance plan is required and shall include:
1. “Covenants for Permanent Maintenance of Stormwater Management Facilities” (also
called the “Maintenance Covenants”). An example covenants document can be found in
Volume 3.
2. “Inspection Checklist and Maintenance Guidance” for each type of stormwater facility that
is located on the property. Templates for each stormwater management facility can be
found in Volume 3 of this manual. These templates can be amended slightly for use in
more customized O&M plans.
3. As-built drawings must accurately identify the location and layout of the facility, and also
clearly identify reserves and access easements.
All stormwater management facilities must be maintained in accordance with the O&M Plan.
Volume 2, Technical Guidance Page 3 - 159