Science

Dry Hydrants in Rivers and Lakes

Historically, our rivers and lakes have been used for fishing, water power for mills making lumber and woolens, and moving commercial goods, etc.  Today, our rivers and lakes are used and valued for aquatic ecosystems, swimming, fishing, boating, water supplies, hydropower, and fire protection by means of dry hydrants installed for town fire departments.  The days of the old “bucket brigades” passing water by hand to the fire scene from rivers and lakes are gone.

A dry hydrant or riser standpipe is a non-pressurized fire suppression tool used to draw non-potable water for firefighting in towns where no municipal water system serves rural areas in town.  From 1998 to 2014, the Watershed Management Division has worked with towns and the Vermont Rural Fire Protection Task Force to permit the installation of dry hydrants in 212 towns funded by federal programs at a cost on the order of $3,000 to $10,000 each.  Another 25 hydrants are planned for 2015.

Dry Hydrant on Pinney Hollow Brook off a road in Bridgewater, Vermont

Dry Hydrant on Pinney Hollow Brook off a road in Bridgewater, Vermont

Dry hydrants are a post or pillar type active fire protection measure you see along road sides and parking lots for fire fighters to tap into a water supply.  Fire hydrants can be a combination of a valve at the top and hose outlet(s) and dry hydrants are just a hose attachment for the fire engine or pumper truck, and can deliver in the range of 500 to 1,500 gallons per minute.  The centrifugal pump on the fire truck draws water from the river or lake through a permanent strainer and minimizes the number of firefighting crew members needed to draw water in comparison to a direct draft from a water body.  Dry hydrants are simple and require minimal inspection and maintenance, and annual maintenance requires back flushing sediments out of the water line and strainer to optimize pump draw rates.

20150803DualTearDropInlets

Dual Tear Drop Inlets in the Ottauquechee River in Bridgewater, Vermont

The 3 types of dry hydrants include a strainer inlet suspended in the water of a river or lake, a screen (slotted) pipe buried in the stream gravel or a concrete well tile (perforated cistern) buried in the stream gravel.  The strategic siting of the hydrant location requires a site visit to review the constraints and opportunities for the hydrant to serve a particular geographic region of the town and includes an assessment of the access and maneuverability of the fire truck as well as addressing the risks and vulnerability of the water resource to be used for drafting water for fire protection.

As always, the cost of dry hydrants drives the site selection to an existing road side, bridge locale, or parking lot to reduce the economic impacts.  These sites also represent an area where infrastructure has already encroached on riparian buffers and shore lands, thereby limiting the amount of new encroachment represented by the dry hydrant.  The Stream Alteration General Permit encourages the use of these areas because new bank and shoreline revetments or disturbance, other than that needed to protect the nearby road or bridge, would be minimal. Very frequently, the amount of disturbance to vegetation and soil earthwork in riparian buffers is minimal along rivers, streams, lakes and ponds.  The inlet strainers are designed to avoid pulling aquatic life and debris into the truck that might damage the centrifugal pump and/or block the fire hose nozzle.

Well Screen Inlet on Ball Mountain Brook off a parking lot in Jamaica, Vermont

Well Screen Inlet on Ball Mountain Brook off a parking lot in Jamaica, Vermont

Many towns have multiple dry hydrants serving the various hamlets in town to eliminate the inefficiency and complexity of long-distance water hauling that can delay a firefighting effort.  The multiple dry hydrants reduce the travel time in delivering water to the fire scene to improve the fire fighters response and allow the fire fighters to keep a safe distance while dousing the fire and reduces the risk to the fire department crew.  Town fire department dry hydrants are a win-win-win: they provide fire protection, reduce use of potable water, and minimize impacts on our fish, wildlife and water resources.  Please contact the Rivers Program at ANR.WSMDRivers@state.vt.us with any questions.