At their Regular Board meeting, the Coconino County Board of Supervisors listened to presentations by County staff on current Schultz Flood mitigation efforts. The development of the Drainage Master Plan, specifically for the Schultz Flood area, continues to be a top priority, along with the development of a supporting funding plan and an update of the existing emergency response plan for the affected area.
On February 3, engineers and scientists gathered in Flagstaff to analyze and discuss flood mitigation design concepts proposed by six engineering firms. Hosted by Coconino County, the second Ridgeline to Rio Summit included representatives from the U.S. Forest Service, Arizona Department of Transportation, Natural Resources Conservation Service (NRCS), U.S. Geological Survey (USGS), Arizona Division of Emergency Management, U.S. Army Corps of Engineers, Coconino County, City of Flagstaff, National Park Service and the Black Bill Park Neighborhood Association. The engineering firms presenting design concepts included Natural Channel Design, Inc., CivilTec Engineering, J.E. Fuller, Kimley-Horn and Associates, Shephard Wesnitzer, and Turner Engineering.
The engineering firms presented various options using a 24-hour, five-year storm event scenario, with a 20% probability of occurrence each year. The options included non-structural measures, natural channels, hardened channels and large retention basins. Shared themes among the group included common channelization routes through private property and/or on Forest Service property, berms, detention and sediment basins, roadside channel improvements along N. Hwy. 89, and the potential need for additional crossings at the highway.
Some of the firms provided very preliminary construction cost estimates in excess of $15 million to implement their design concepts, with an estimated timeline of several years. They pointed out that the design concepts are meant to assist in flood mitigation; however, the risk of flooding will remain for an undetermined period of time.
Additional considerations and evaluation criteria discussed by the participants included:
• Protection of the City of Flagstaff Landfill and N. Hwy. 89
• Cinder Lake capacity – unsure how much water it can hold
• Secondary access – may be necessary with channelization
• Impact on Doney Park from upstream measures
Environmental and cultural resources impacts • Community asset/aesthetic value – opportunity to provide “value added” asset to thecommunity • Capital costs – including cost/benefit analyses required by funding agencies • Maintenance – requirements and costs • Funding availability • Failure analysis/minimize impact – a greater storm event may occur than what is designed for, do not want to impact homes not already in harms way • Utility conflicts
The engineers reiterated the importance of completing the Sediment Transport Study, Hydraulics Study and Cinder Lake Capacity Study in order to complete the draft Drainage Master Plan. All three studies are critical to the design and success of potential flood mitigation measures.
The Sediment Transport Study will account for the amount of debris (bulking) expected with flood flows. Sediment and debris will increase the volume of flows discussed in the Hydrology Study, which reflected clear flows, estimated the depth of the water, and indicated where the flood water is expected to flow. The results of the Hydraulics Study, showing the level of potential flooding at individual properties, is critical to understanding the severity and risks associated with potential future flooding. Both studies are expected to be completed in mid-March.
The County is also working with USGS on the Cinder Lake Capacity Study to determine the amount of water Cinder Lake can hold, and where the water drains once it flows into Cinder Lake.
Another key focus area is the development of a funding plan related to mitigation efforts. County officials recently submitted an application to NRCS, written by Natural Channel Design, Inc., requesting approximately $6 million under the Emergency Watershed Protection Program for flood mitigation measures on private property. The application included the consideration of flood mitigation throughout the entire flood area (including Sunset Crater Estates in Doney Park) and specifically assessed over 100 properties that experienced serious erosion and impacts from flooding. The application approval is contingent on federal funding and requires a 25% local match (approximately $1.5 million). If approved, the funding must be spent within 220 days from the date the funds are obligated.
The key challenges with implementing any mitigation projects are finding a funding source for the local match, and obtaining rights-of-way on private properties. The County is working with partner agencies to explore funding options, while informing Congressional representatives of the mitigation needs and potential flood risks.
Kristin Bail, Deputy Forest Supervisor with the Coconino National Forest, provided a brief update on Coconino National Forest efforts. The Burned Area Emergency Response team has invested over $4 million toward seeding, mulching and routing water off roads within the Forest. Currently, public comment is being sought on additional long-term forest restoration efforts, including safety hazard mitigation along roads and trails, salvage of dead and dying trees along the roadways and trails in severely burned areas, and reconstruction of roads and trails. In addition, the National Forest is considering the need for more mulching, a fence along the Copeland channel, opportunities for volunteer efforts and aspen regeneration. Bail, along with the Supervisors, emphasized the importance of the County and Forest Service working together in developing the Drainage Master Plan for the area.
The presentation to the Board of Supervisors today concluded with staff identifying the “next steps,” which includes informational sessions regarding the results of the various studies and then a formal public participation process that will provide for input from the property owners in the affected area regarding the draft Drainage Master Plan. Simultaneously, County staff is reviewing the emergency response plan for the area and identifying actions needed to prepare for the upcoming monsoon season.
For more information, call Coconino County Information Coordinator Lindsay Daley at (928)679- 8300. Flood information is also available at www.coconino.az.gov/schultzfloodinformation.aspx.