For the Contractor/Designer

Stormwater Design/Post Construction BMP Design Requirements

The City of Hays has an adopted BMP Post Construction Manual to assist in the design and implementation of Post Construction BMPs when required.  We also provide a design document to assist in the design of storm drainage systems.  Use the links below to view the documents.

Post Construction BMP Manual

Design Criteria Storm Drainage Systems and Facilities

Post Construction Controls. Post construction stormwater controls include water quality treatment and flood control. Post construction stormwater controls are required in the following circumstances:

For properties in the major system as defined in Sec. 9.2.301, Stormwater Runoff Management System, Subsection B, Major System. The major system shall be composed of the regulatory floodplain as shown on the National Flood Insurance Program (NFIP) maps developed for the City by the Federal Emergency Management Agency (FEMA).

  1. When any property or larger common plan of development will add 10,000 square feet of impervious area, it shall meet requirements of the Post Construction Storm Water Best Management Practices Manual. Redevelopment shall be required to control the 85 percent storm for water quality purposes. New development shall be required to control the 90 percent storm for water quality purposes.
  2. When any property or larger common plan of development disturbs more than one acre of land, it shall meet the requirements of the Post Construction Storm Water Best Management Practices Manual. Redevelopment shall be required to control the 85 percent storm for water quality purposes. New development shall be required to control the 90 percent storm for water quality purposes.

For properties in the minor system as defined in Sec. 9.2.301,Stormwater Runoff Management System, Subsection C, Minor System.  The minor system shall consist of storm drainage facilities including, but not necessarily limited to, roadway curb and gutter, open channels, gullies, streams, creeks, swales, and enclosed and open conveyance systems which transport storm runoff to the major system.

  1. When any property or larger common plan of development will add 10,000 square feet of impervious area, it shall meet requirements of the Post Construction Storm Water Best Management Practices Manual and ensure that post-development runoff from the five-year, 25-year, and 100-year storm event results in no increase in peak flow rates from the entire site, in accordance with the most recently adopted "Design Criteria Storm Drainage Systems and Facilities."
  2. When any property or larger common plan of development disturbs more than one acre of land, it shall meet the requirements of the Post Construction Storm Water Best Management Practices Manual. Redevelopment shall be required to control the 85 percent storm for water quality purposes. New development shall be required to control the 90 percent storm for water quality purposes.