Report by Ben Lomeli 

The Nogales Wash channel is very old, in bad condition and way under capacity to safely convey increasingly bigger floods and sediments flows due to upstream development, expected to continue.

  • Detention basins constructed in Mexico are too few, too small and have quickly filled up with sediments.
  • Watershed improvements are also needed to reduce stormwater peak flows and excessive sediment flows
  • Climate change predictions are for warmer and drier conditions overall, with:
    • Less frequent but more intense storms,
    • Increased drought,
    • Increased threat of wildland fire,
    • Changes in vegetation types
    • Less vegetative cover to protect undeveloped portions of the contributing watershed
    • Increased storm intensities can be expected to cause more erosion, more sediment production and higher peak flows.

Groundwater recharge to the aquifer that we all depend on for all our water needs is reduced by impervious and flashy watershed conditions.

  • Our lives and the long-term economic sustainability depend directly on the available quantity and quality of groundwater; it is our only source of potable water supply.

The IOI is located underneath Nogales Wash and is threatened by flooding.

  • Proposed CIPP (cure-in-place pipe) lining will only address leaking problems (infiltration of groundwater into the IOI and exfiltration of raw sewage into the aquifer occurring at several locations),
  • CIPP will not address or reduce the threat of flood-induced ruptures.
  • The capacity of the Nogales Wash channel must be upgraded to relieve flooding in Nogales and to eliminate threats of bursting the IOI.
  • As long as the contributing watershed in Mexico continues to produce abrasive sediment-laden peak flows that far exceed the conveyance capacities of Nogales Wash, all our local stormwater infrastructure remains at risk.
  • As long as the IOI remains underneath the deteriorated unstable and undersized Nogales Wash, the threat of IOI ruptures remains a reality that will most likely be increased by climate change.
  • We were lucky this time. It was a single and only partial rupture, it was detected in reasonable time, the flows were not as large or as long-lasting as they can be, and the rains did not continue to produce subsequent flows that would have further delayed the temporary repairs that were undertaken.

Next Steps:

  • Enact International legislation that will bring Inter-National funding for permanent solution.
  • Examine available GIS layers and other useful data sets to begin conceptual planning of possible permanent comprehensive solutions for the Nogales Wash/IOI/railroad problems.
  • CIPP should be used immediately, but only on section(s) known to be leaking (exfiltrating) raw sewage into the aquifer.
  • Install real-time transmitting transducer sensors that can detect flow levels and water quality changes for breach monitoring.
  • This is a matter of true national security; if we don’t have clean drinking water and are not protected from public health threats, how secure are we?
  • The IBWC must take responsibility and secure funding for this border crisis and first, repair the IOI leaks. But second and more importantly, they must get the IOI out of the Nogales Wash, keeping it at same elevation profile to accommodate all existing lateral connections.
  • “Business Friendly” approaches.

The Union Pacific Railroad (UPRR)

  • Is aligned next to Nogales Wash,
  • Bisects the City of Nogales,
  • Often causes traffic delays and emergency response concerns.
  • Relocating UPRR east to river is a terrible idea!!
    • Excessive costs,
    • Environmental impacts and consequences,
    • Potential riverine contaminations,
    • Lost economic opportunity for downtown passenger trains.

A holistic integrated engineering approach and sufficient funding to comprehensively address all comingled stormwater infrastructural, water resource and environmental issues facing Ambos Nogales and Southeastern Arizona communities along Nogales Wash and the Santa Cruz River are desperately needed.

  • A grant for the U of A (Colleges of Engineering and of Landscape Architecture) is recommended to evaluate conceptual integrated solutions.
  • Coordination with UPRR is critical,
    • Should begin ASAP,
    • May offer best possible solutions and outcomes. (e.g., possible IOI & additional wash capacity under UPRR).