7-20-30 Water Courses and Drainage

7-20-30: WATER COURSES AND DRAINAGE

(a) Applicability

• The water resources standards in this Sec. 7-20-30 are applicable to all development.

(b) Encroachment or Channeling

• Encroachment or channeling activities in a river, stream (including intermittent streams), pond, wet meadow, or wetland are also subject to the requirements of Secs. 7-20-40 and 7-20-80 of this Land Use Code, as well as all other applicable state and federal statutes and regulations (including, but not limited to the U.S. Army Corps of Engineers permitting requirements of Section 404 of the Federal Clean Water Act).

(c) Drainage

1. All Activities and development shall provide for:

(a) The unimpeded flow of natural water courses and ditches;

(b) Adequate drainage for all low points; and

(c) Maintenance of drainage systems

2. Activities and development that disturb more than 1,500 square feet, are located in a Constrained Area or a deemed necessary by the County Planning Engineer, shall be required to submit engineering documents for stormwater detention facilities designed by a professional engineer licensed in the State of Colorado that shall:

(a) Detain flows to historical peak discharge rates and provide water quality benefits; and

(b) Ensure the post-development peak discharge rate does not exceed the undeveloped peak discharge rate for the 25-year return frequency, 24-hour duration storm. The drainage system shall account for an entire drainage basin capable of accommodating runoff from a proposed development and, the runoff from contributing areas adjacent and upstream;

(c) Provide safe passage of the 100-year storm event, minimizing the threat of major property damage and loss of life;

(d) Be maintained to ensure function; and

(e) Provide on-site treatment of stormwater by use of best management practices designed to detain and allow infiltration of runoff prior to discharge to any water body.

d) Groundwater

• Activities and development shall not result in the introduction of any contaminants to groundwater, or interfere with any recharge area or aquifer.

(e) Irrigated Areas

• Activities and development shall:
  1. Not adversely affect the adequacy of water supplies available for the irrigation of agricultural lands; and
  2. Not adversely affect the exercise of any existing and decreed irrigation water right.

(f) Irrigation Ditches

• Activities and development shall:
  1. Access
     • Provide for access to irrigation ditches by ditch owners and to the public if a ditch is to be, or is part of the Pitkin County Open Space and Trails System or other public property.
  2. Preventing Leakage
     • Ensure that no building shall be constructed immediately downhill of a ditch unless the ditch can be placed in a culvert, lined, or otherwise treated to avoid leakage of water downhill towards the building.
  3. Avoid Flooding
     • Design land uses to avoid flooding problems from flood irrigation.
  4. Avoid Seepage
     • Place basements and soil absorption on-site wastewater treatment systems in locations where they will not be impacted by flood irrigation or seepage from irrigation ditches.