Tenmile Wash

To provide comments on this watershed for consideration in the Floodplain Management Plan, contact Greg Saxe
Planning Manager
(520) 724-4633.
The Tenmile Wash watershed includes Gibson Arroyo within the community of Ajo and extends from the Pozo Redondo and Batamote mountains in the east across the basin floor to the Little Ajo and Childs mountains in the west. From these head-waters, this watershed then drains northward into Maricopa County. The District has documented numerous flooded homes in Ajo and Why, Arizona. Floods in these areas arrive with little warning and extreme caution is warranted during inclement weather. Flood insurance is highly recommended. This water-shed is comprised of 207,127 acres and contains 11,763 acres of SFHA, 182 acres of locally identified floodplain and 13,409 acres of Pima County Regulated Riparian Habitat.

Flood Hazards

Maps

Click HERE to view the watershed map
Click HERE to view the outreach brochure

Floodplain Studies

Floodplain Study FP-052-2004 - Emergency Evaluation Study Report on the July 29, 2003, Flooding in Ajo, Arizona, TetraTech, April 2004. Ajo Flood depth map, PCRFCD, 2010.

Drainage Study for the Curley School Detention Basin, Ajo, Arizona, DMJM Harris, January 2006.

Erosion Studies

There are currently no erosion studies in this watershed.

Areas of Interest (Known Issues, Gaps, Problems and Needs)

Issues Provided by Public and Stakeholder Input

No issues have been identified to date.

Issues from the District Flood Response Manual

 8.2.1 Data Gathering Needs
• No site specific issues identified.

8.2.2 Frequently Flooded Structures and Properties Subject to Damage
• 701 W. Rocalla (401-24-0880) There is a culvert that goes under the house and outlets right next to the house. Flooding source is Gibson Arroyo (T12S R06W Sec. 22)
• 530 W. Morondo Ave. (401-24-0150) Flooding source is a tributary to the Gibson Arroyo (T12S R06W Sec. 22)
• 400 W. Morondo Ave. (401-23-2520) Water backs up behind bridge and floods property. Flooding source is a tributary to the Gibson Arroyo (T12S R06W Sec. 22)
• 401 W. Rocalla Ave. (401-23-2610) Water backs up behind bridge and floods property. Flooding source is a tributary to the Gibson Arroyo Sewer pipe broke in July 2003 event and flooded basement. (T12S R06W Sec. 22)
• 201 W. Solana Ave. (401-23-1410) A fully lined channel goes underneath the home. Flooding source is a tributary to the Gibson Arroyo (T12S R06W Sec. 22)
• 341 W. Arroyo Ave. (401-55-2440) Flooding source is the Gibson Arroyo (T12S R06W Sec. 15)
• 140 W. Arroyo Ave. (401-55-2420) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)
• 130 W. Arroyo Ave. (401-55-2430) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)
• 131 W. First Ave. (401-55-2210) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)
• 120 W. First Ave. (401-55-1960) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)
• 111 W. Second Ave. (401-55-1830) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)
• 100 W. Second Ave. (401-55-1690) Flooding source is the Gibson Arroyo (T12S R06W Sec. 14)

8.2.3 Infrastructure
• Water may come up out of the storm drain on the south side of Esperanza Avenue, east of Montecito Street, due to head created by water backing up behind the headwall located at the southwest corner of Esperanza and Montecito. (T12S R06W Sec. 22)
• The Curly School Detention Basin near Esperanza Ave. and Orilla Ave. The old high school football field has been transformed into a storm detention basin. Inspect the conditions of the inlet spillways and note if slope erosion has occurred along the basin walls. The culvert outlet should also be inspected for debris blockage. (T12S R06W Sec. 22)
• The drainage ditch along the south side of the Ajo Community Health Center. Inspect for damage to or blockage of the drainage ditch south of the Community Health Center. County maintenance responsibilities stop at the north side of Solana Avenue. The culvert at Solana Ave. belongs to the Arizona Department of Transportation and the drainage upstream (south) of Solana is private. (T12S R06W Sec. 14)
• The County maintains the Gibson Arroyo upstream of 2nd Avenue to Cedar Street via a maintenance easement granted by Phelps Dodge. This area is subject to deposition. Bank erosion can occur in upstream and downstream of Cedar Street. Upstream of Cedar street there are no construction plans for the channel. Utilities crossing to the channel are shallow and in some locations exposed. The channel lacks capacity for moderate to strong storm events and widespread flooding is likely. Flood damage reports should address channel conditions. (T12S R06W Sec. 15)
• The County maintains that portion of the drainage ditch north of Ocatillo Avenue that lies within the road right-of-way from Sahuaro Street east to a point approximately 170 feet east of Tecolote Street, at which point the channel leaves the road right-of-way. It is unknown if we maintain the foot bridges across the channel. Flood damage reports should address the condition of the channel. (T12S R06W Sec. 15)

8.2.4 Safety Concerns
• No site specific issues identified.

 

Recommendation of Actions and Floodplain Management Strategy

This section to be completed based on feedback received through the planning process.