Surface Water Topics

Rain Storms!
The weather in the Pacific Northwest during November has been described as an "atmospheric river".  We have already seen pictures and even ourselves witnessed rivers flooding or nearly flooding nearby areas, streets full of water, and roadways actually being washed away.  All of this, and we further hear this is only the beginning of what may prove a very wet winter.

Runoff is surface water that flows from one area to another.  During rain storms, that runoff starts from where the rain lands and flows downhill however it can.

When it starts raining, even a small city of Mill Creek's size can produce and accumulate a lot of runoff water quickly.  The city is about 4.7 square miles in area (nearly 3,000 acres or nearly 130 million square feet!).  Even the grassy and other vegetated areas in Mill Creek do not absorb all the rain right where it lands. 

All that runoff that needs to be controlled and helped to flow down to North Creek.  Our combination of public and private stormwater pipes and facilities help with that, along with our natural streams like Penny Creek.

Even with nearly 3,600 street storm drains in the city to collect runoff, and nearly that same number of additional drains located in parking lots similar areas, it is common for water to pond up and not drain away quickly.  Hard surfaces like streets and driveways are particularly prone to this ponding.

What can I do?

Before the next storm?
1. City crews continue to sweeping our streets as the leaves continue to fall.  However, as storms become longer and more frequent, those same crews are called upon to address emergency storm response activities.  It gets more and more difficult to keep streets swept. 

Continue to check street and other storm drains near your home or business.  Use a rake to keep them free of leaves, broken branches, and other debris.  Dispose of the debris with your yard waste.  Sweep debris safely from the sidewalk or street shoulder and do not stand in the street!

2.  Check any drainage structures, including your roof gutters, on your property.  Make sure no leaves or debris are blocking and water can flow as freely as possible.

3.  Leaves, broken branches, and other debris clump up when wet, and can really slow runoff water flow down (especially in street gutters and parking lots!).  This happens even if the clumps seem small when dry. 

Watch for clumps. Use a rake to scoop up the clumps and debris and dispose with your yard waste.  Sweep debris safely from the sidewalk or street shoulder and do not stand in the street!

4.  Check your basement and yard sump pumps, if you have them, and make sure they are working.  If they run on electricity, consider a battery backup power supply.  Avoid using generators!

5.  Move chemicals such as paint, cleaners, or fertilizers to storage locations off the floor.  Store in waterproof containers when possible.

6.  Move cloth items such as blankets, towels, or lawn furniture cushions off floor areas where they may get wet.  If they do get wet, move them to a dry location to dry out as soon as possible. Both of these are important for avoiding mold or rot that may be unhealthy.

7.  Prepare for power outages! Have a home emergency kit (flashlights, batteries, etc.). Have a plan for recharging cell phones and similar electronic devices in case case the power is out.  Make sure you have (and can find in the dark) the needed chargers and cords.  Avoid using generators!

During a storm?
1.  Watch for ponding water in your street and yard.  Avoid walking or driving in areas of ponding.

2.  If you must drive through ponded water, avoid driving through deep-looking areas and slow down.

3.  If water does get into your home or building, unplug electric appliances that may end up in the water.  Do no attempt to unplug electric appliances already in flood water.

4.  As much as possible, stay indoors and avoid walking or driving (especially at night).

After the next storm?
1. Inspect your home and yard.  Look for downed or damaged trees.  Look for signs of roof damage.  If you have above-ground electrical or similar utility lines, look for damaged or disconnected lines.

2.  Look for eroded or ground disturbance sliding, particularly on slopes in or adjacent to your property.

3.  Clean up and dispose of all storm debris promptly.

4.  Mop and dry building interiors as soon as possible.  Put cloth items that get wet, including towels used to mop up water, in areas where they can dry promptly.

What About Snow and Ice!
We typically see snow only a few days each winter, so snow close to our homes and workplaces can catch us by surprise.  Freezing and icy temperatures are more common, but can also surprise us.  Even though we do not have the more constant snowy or icy conditions of other parts of the U.S., it is important to be prepared!

Using de-icing salts on sidewalks and pavements
Salts and similar de-icing chemicals can be used to excess.  In addition to being wastefully expensive when over-used, these salts and chemicals tend to remain in snow and melt water alike, and can be hazardous to children, pets, and fish or other wildlife exposed to the snow or runoff (particularly either drinking the water or swallowing the snow).

1.  Do not use de-icing salts or chemicals on the paved surfaces while the snow is still falling.  Keep clearing paved surfaces with shovels until the snow fall has stopped.

2.  Only use de-icing salts and chemicals to the minimum needed to melt the surface and make your priority walkways and driveways safe to use.  Once those surfaces are melted, remove excess salts or other de-icers and dispose properly as you would similar materials.

3.  Follow the guidance and advice below for encouraging water from melting snow to run off and drain as promptly as possible.  This will both reduce the continuing risks of these areas refreezing back into ice and reduce the amount of pollutants in the stormwater system.

4.  Snow and slush are good insulators of icy conditions under them, and can protect ice below the snow/slush layer from being melted by de-icing salts and chemicals.  Make sure areas are as well-shoveled as possible before using de-icing salts or chemicals

Shoveling snow guidance
1.  Purchase a snow shovel early, if you don't already own one.  They sell out fast once snow starts falling!

2.  Pick a snow shovel you can use comfortably.  Bigger is not necessarily better, particularly when the snow to be shoveled is wet.

3.  Locate all your property drains, as well as the nearby street drains.  Once covered by snow and ice (especially if further covered by a snow plow), drains are very difficult to find.  It is important to keep drains uncovered to drain off water from melting snow.  Always avoid piling snow over drains!

4.  Identify areas in advance to pile snow from your shoveling and/or plowing.  Pick areas where you do not normally see ponding during rainy weather.  Avoid areas that will not drain runoff surface water from melting snow.  Avoid picking areas that will drain runoff surface water from melting snow onto your paved areas.  Avoid piling snow over drains!

5.  Street plows typically cannot plow curbs and gutters in streets well.  Plowed snow from the street (as well as from sidewalks, driveways, and other paved areas) can cover street drains.  If you see a covered street drain, shovel the snow off to reveal the drain grate.  Remember:  shovel from the sidewalk or behind the curb; do not work in the street!

6.  Try to clear a couple feet on all sides of drains and, when possible, shovel corridors to drains from various areas.  Both of these will help runoff from melting snow to drain away as promptly as possible.

7.  Clear your downspouts to make sure water melting from your roof flows away from your building.  Avoid allowing snow sliding off your roof to accumulate right at the base of your building walls, as melting water from this snow may make it into a basement or crawlspace.

8.  Snow and ice almost always melt fastest when the paved surfaces are all or partially/thinly exposed to any sun or warmer air temperatures during the day.  Once melted, runoff water should be encouraged to drain off paved areas as quickly as possible before it can refreeze.

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Frank Reinart
City Engineer
Phone: 425-921-5745
Report a Spill!