How Storm Water Systems Work
Storm water runoff management is an intricate system that many of us take for granted on a daily basis. It exists throughout our communities to maneuver rainfall and other collected water to collection basins and away from our residences and often mini ROVs like the Deep Trekker DTG2 are used to inspect these systems. There are many reasons why this water must be transported away, the main reason is to avoid flooding.
For a brief moment, let's look at the basics of the water cycle:
As you may notice in this diagram, this is a completely natural environment. Regular surface runoff cannot occur once buildings, roads and other impermeable surfaces are constructed. This disrupts the water cycle and causes a variety of issues. The solution is to transfer the water in a similar pattern mechanically. Here is a diagram of a storm water system:
An important note to make from this is that the storm water and sewer lines are separate. The storm water falls as precipitation, flows over buildings and roads into the manholes where it then travels through pipe networks to storage basins and into natural or man made ponds or lakes. These man made lakes should not be mistaken for natural recreation areas; though wildlife may flourish around an open storm water basin, the water is often contaminated with oil from car drippings, pesticides from residential lawns and sediments of heavy metals especially around industrial areas (USEPA 2001). This water is not treated or used for drinking purposes generally because of these contaminants.
There are many precautionary measures besides the drainage network to prevent storm water from mixing with our drinking water resources, especially where our cities and roads are located directly adjacent to reservoirs. Here are some additional features throughout our cities that you may not realize are for storm water management:
Minimizing Directly Connected Impervious Areas - City planners will try to include a grassed area between a road and a water source. Grass lawns or other permeable, biological surfaces naturally filter some of the contaminants through the soil before the water finds its way into the aquifer.
Concrete Grid pavement - Voids in pavement allows the storm water to percolate through to permeable materials and then be filtered naturally.
Grassed Swales - Shallow, vegetated ditches directly beside roads that reduce the speed and volume of the runoff. Filtering can occur but the swales must shallow enough that they do not collect water to a point of being a small basin themselves.
Buffer Strips - Combinations of trees, shrubs and grasses planted along a stream. These strips should consistent of three zones: four to five rows of trees, then two rows of shrubs and finally 20 to 24 feet of wide grass. This reduces the velocity of the runoff and removes a good portion of solids before mixing with drinking water.
Filter Strips - Gently sloping vegetated areas surrounding a surface body of water. These hold the soil in place and act as a filter before storm water reaches the body of water.
Storm Water Ponds or Wetlands - Permanent ponds where solids settle between storms are created to collect the water. Storm water drainage efforts in surrounding areas are directed to the pond. These ponds often are used as visual features in communities or parks. The damage to the environment is minimal if managed properly and if the sediment is removed every seven to ten years.
Infiltration Practices - Narrow, stone-filled excavated trenches. These are deeper than grassed swales, the three to twelve feet deep trenches store runoff between the stones and slowly infiltrate the soil. When combined with other pre-treatment practices such as a swale, this method has been found to filter up to 98% of contaminants.
Swirl-type Concentrators - Underground vaults that are designed to create circular motion, creating sedimentation and oil and grease removal. The currents rapidly separate out settleable grit and floatable matter.
The cumulative effects of runoff being left unchecked can be dangerous. Inspection of each part of the storm water management system is key to maintaining the water cycle balance over the long term. Deep Trekker ROVs are used to inspect these networks. If do you have a system that's overdue for an inspection, contact us to hear how we can help you.
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