Instant Underflow Dam


Prevent spills from spreading with the quickest way to dam up ditches and small streams. The Instant Underflow Dam installs in minutes, with only 2 or 3 people.

Available sizes online:

  • DAM2125:   21”H x 25’L
  • DAM2825: 28”H x 25’L

Other available sizes: DAM3930: 39”H x 30’L.
Call 814-822-2004 to order or request pricing for DAM3930.



Spills spread 100 times faster when they reach a body of water.

Traditional underflow dams are not a quick solution.

  • A lot of sandbags, dirt and pipe.
  • A lot of manpower or machines.
  • A lot of time.

By the time traditional methods are implemented, the impact of the spill will cost you big bucks.

The Instant Underflow Dam:

  • Installs in minutes, with only 2 or 3 people.
  • Flexible material allows it to adapt to most stream and ditch bottoms.
  • No special equipment needed. No filling with water or inflating with air needed. Simply unroll the dam, unfold the upstream flap and let the flow of the stream fill it.
  • No anchoring needed. Just uses the weight of the water to weigh it down to the stream bottom.
  • Underflow holes built into the downstream side, so that you can regulate the flow on the upstream side and keep the spill contained.
  • Multiple units can be attached together to make whatever length you need.
  • Wash and reuse dozens of times.

Learn More:

Blog: Stop Sandbagging! Create Underflow Dams in Less than 10 Minutes

Case Study: Fast Daming Oil Spills in Hard-to-Reach Streams

Article: Ensure Rapid Response Time for Effective Spill Control

Training: Underflow Dam Instructions Videos (includes step-by-step instructions for deployment, removal, and storage)

On-Demand Webinar: JAN 2022 Instant Underflow Dam Webinar

White Paper: Underflow Dams in Less than 10 Minutes

On-Demand Webinar

On-Demand Webinar

Learn how to quickly stop oil spills on water with the Instant Underflow Dam — presented by HalenHardy partner and trainer Troy Beaver with special guest Bill Dennis from Ardent Environmental Services.

Watch Now →



Stop Sandbagging! Create Underflow Dams in less than 10 minutes

Instant Underflow Dams weigh less than 60 lbs and are easy to deploy

How it Works - Instant Underflow Dam

How to Deploy Instant Underflow Dam

How to Remove Instant Underflow Dam

How to Connect Instant Underflow Dams

How to Clean and Store Instant Underflow Dam

Product Specifications

Product Specifications

Download Product Specs →

DAM2125 DAM2825 DAM3930
Water Retention Height 21” 28” 39”
Product Length 25 feet 25 feet 30 feet
Product Width
(Stream Bottom Skirt)
72” 97.5” 158”
Product Weight 37.4 lbs 59.5 lbs 150 lbs
Rolled Up Dimensions 16”W x 16”L x 20”H 16.5”W x 16.5”L x 25”H 21”W x 15”L x 37”H
Underflow Holes 13 14 19
Carrying Case YES YES YES

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