Chapter 39.36
STORMWATER
Sections:
39.36.020 Stormwater discharge.
39.36.030 Preparing for disaster.
39.36.040 2010 Comprehensive Plan goals and policies.
39.36.050 Orchard Mesa stormwater.
39.36.010 Background.
The 2010 Comprehensive Plan discusses Natural Hazards, which include drainage and stormwater management. Drainage for Orchard Mesa is managed by the City of Grand Junction, Mesa County, the Orchard Mesa Irrigation District, and the 5-2-1 Drainage Authority. Although the average annual precipitation for the Grand Junction vicinity is only about nine inches, flooding can and does occur. Because large storms are infrequent, drainage issues were overlooked in the past. Our native clay soils do not absorb water well. Vegetation is sparse in many areas and this encourages erosion. Finally, development increases the amount of impervious surfaces in the form of roofs, driveways, and parking lots, reducing the amount of open ground. These past practices and environmental conditions collectively promote little infiltration, rapid runoff, more debris in the runoff, and flash flooding.
In addition to flooding concerns, water quality is also important. There are many entities that are involved in stormwater quality in the Grand Valley, including Mesa County, City of Grand Junction, Town of Palisade, Grand Valley Drainage District, Orchard Mesa Irrigation District, Grand Valley Water Users’ Association, and School District No. 51. The Grand Valley Stormwater Unification Feasibility Study was conducted in 2003 and the 5-2-1 Drainage Authority was created to help monitor and manage the quality of water as it returns to local washes, creeks and rivers.
(Ord. 4629, 5-7-14)
39.36.020 Stormwater discharge.
To aid in returning runoff to water sources safely, the U.S. Environmental Protection Agency (EPA) has developed a National Pollutant Discharge Elimination System (NPDES) stormwater permitting program. As part of the NPDES guidelines, employees in the Orchard Mesa Irrigation District (OMID) and the Grand Valley Water Users Association have the authority to monitor and report violations to the City of Grand Junction or Mesa County. (http://www.irrigationprovidersgv.org/stormwater_discharge.php) Generally, urban runoff will be treated as a pollutant, while agricultural drainage is exempt from NPDES regulation. Increased stormwater drainage in OMID’s system may add to the district’s permitting and treatment requirements.
(Ord. 4629, 5-7-14)
39.36.030 Preparing for disaster.
The 5-2-1 Drainage Authority received a pre-disaster mitigation grant from the Federal Emergency Management Agency (FEMA) in 2009 to address several known problems on Orchard Mesa. A comprehensive drainage study, from 30 Road to the west, was completed as part of the grant project, resulting in the following map (Figure 9; Appendix Map 22). It identifies the area that would be inundated by a one percent chance (100-year) event, which is two inches of rainfall in a 24-hour timeframe. There are approximately 400 acres and 700 structures in the floodplain. The study found that spending over $4,000,000 (2009 dollars) to perform improvements would remove approximately 100 acres from the floodplain.
Figure 9: Orchard Mesa Flood Inundation Study
Although FEMA has not created a Flood Insurance Rate Map (FIRM) from this study, the City is using it as the “best available information” to govern development in the area and to ensure all new structures are built high enough they will not flood in the one percent chance event. Because this is not yet a FIRM, lending agencies probably won’t require flood insurance to issue a loan. Affected landowners should consider obtaining flood insurance because basic homeowner’s policies do not cover flooding. A composite of the study area plus the FEMA-regulatory floodplain is shown in Appendix Map 23.
(Ord. 4629, 5-7-14)
39.36.040 2010 Comprehensive Plan goals and policies.
(a) Goal 11. Public facilities and services for our citizens will be a priority in planning for growth.
(b) Policies. The City and County will plan for the locations and construct new public facilities to serve the public health, safety and welfare, and to meet the needs of existing and future growth.
(Ord. 4629, 5-7-14)
39.36.050 Orchard Mesa stormwater.
(a) Goal 1. Pre-disaster mitigation is performed to limit potential property damage.
(1) Actions.
(i) Support regional retention and detention facilities.
(ii) Assist in the study of regional drainage needs.
(iii) Create partnerships between local entities responsible for stormwater.
(b) Goal 2. Improve and maintain drainage facilities collectively among drainage partners.
(1) Actions.
(i) Support the vision of the 5-2-1 Drainage Authority.
(ii) Create partnerships between local entities responsible for stormwater to establish regional drainage facilities.
(Ord. 4629, 5-7-14)