Even though many climate models hint that the coming El Niño may rival or even surpass the El Niño of 1997-98, the forecasted rainfall may still be unpredictable. However, what remains true is that the past decade of catastrophic wildfires and drought have left a parched landscape ill prepared for torrential rainfall, which can quickly create significant problems for solar and wind projects across the globe. This means site assessments and maintenance practices are a crucial aspect of El Niño preparation.
In order to minimize the damage from these sudden torrential rains, we need to think ahead and consider how heavy rain might impact the land. Even though El Niño is already upon us, during the last two El Niños on record, the heaviest rainfall did not come until February and March. Are we ready for it? While this winter could bring major drought relief, predicted torrential downpours and heavy rainstorms can also have an adverse effect if we are not prepared.
Following years of drought, as El Niño begins, many facilities are already facing drainage plans that are not fully equipped to accommodate the storm water moving through. Solar and wind facility owners, operators and contractors need to prepare now for the upcoming El Niño season. During El Niño of 1997-98, seven inches of rain fell in a single day, overflowing rivers and costing more than $400 million in damage in California.
Water always behaves the same way. It seeks its own level. What does change is the topography and elevation in the settling points. As soil is deposited, it diminishes the volume of a drainage route or a retention basin. Therefore, drainage routes and basins must be cleared of obstructions, dirt and debris that may have accumulated. Flow channels, swales, riprap beds and culverts need to be cleaned out to allow unrestricted water passage. In addition to removing debris, trash and silt buildup, contractors in operations and maintenance should make any repairs necessary to drain grates, catch basins, inlets, channels and roadways, to ensure storm water flows freely. Pay close attention to culverts under roadways using adequate lighting to inspect and ensure unobstructed water passage can occur. Maintain a channel cleaning and maintenance program that addresses vegetation trimming, debris, sediment, and trash in those flood channels.
On a smaller scale, blockage in culverts can lead to similar damage, causing water to flow over roadways and also erode or destroy site access infrastructure. To help prevent this, swales or drainages leading into basins must be intact and capable of carrying storm water at a controlled rate. A breach in a drainage route or flow path negates the design capabilities to move water across the property or into an appropriate catch basin.
A good rule of thumb to follow is “inspect what you expect” by looking at the “story marks” on the property from the last wet weather event. Many utility-scale solar and wind fields are constructed on or around dry lakebeds where land is inherently flat and where soil peculation is minimal. Typically, this means that even a minimal amount of rain can create storm water movement as designed by the grading plan.
For wind projects, mudslides are a looming danger that can come with heavy rains especially after a severe drought, as we have experienced in California. Since water flows and ends at the lowest point by diverting around or destroying any mitigation measures, operators need to ensure that Best Management Practices are in place and allowing water to flow. One way to protect a wind substation in a low-lying area is by placing a diversion (dirt berm) that will train the water to flow around the area rather than through it. This approach can help to minimize the extensive work and cost involved with cleaning a substation damaged by a mudslide.
Another great tool to minimize damage to renewable energy projects is a Tiger Dam — a quick, versatile and reusable system for extreme conditions that helps provide added flood protection to projects in areas where storm water can rise rapidly during rain events. A Tiger Dam section spanning 50-feet can be installed in only a few minutes and can perform the same function as 500 sandbags. The system involves 50-foot sections of water-filled bladders that can be used individually or linked together to form a continuous protective barrier over longer distances.
Tiger Dams can be re-used from year to year and storm to storm to provide added efficiency, and can be installed within very quick timeframes to provide added flood protection where storm water levels may rise. This additional tool can be used at projects that experienced “over-topping” during rain events in 2010 where storm water rose slightly above the flood channel walls and onto adjacent roadways and property.
In addition to facility preparation steps, it is just as essential to develop an equipment and materials checklist for the wet weather season. This checklist should include materials on hand, such as sand bags, shovels, plastic five gallon buckets, plastic sheeting and tarps. Equipment needs include portable water pumps with the appropriate suction hoses/strainer and discharge hoses, a generator, lights and extension cords with GFCI protection.
Here are some additional preparation steps to include in your plan:
- Slopes are best stabilized with riprap, vegetation or by other means, such as mulch, straw waddle or applied soil stabilizers. Hopefully, hydro seeding has already been completed, but it’s never too late. El Niño usually starts around Christmas and finishes by the end of March.
- Roadways that provide critical sight access should be constructed above grade and of a road base type material. To maintain or prepare non-paved roads for wet conditions, soil stabilizers can be added periodically to bind the base material preventing wet weather deterioration, which also helps to minimize dust in the dryer months.
- Fencing can restrict water flow as floating debris builds up, creating a beaver dam effect. Look for areas where water flow passes under fencing and remove any accumulated debris.
- Develop a checklist to inspect all electrical equipment enclosures to ensure cabinets and doors are not only closed but also secured with a good weather seal.
- Inspect conduit openings to ensure they are weather tight. In some applications high quality expanding foam or UV resistant RTV can aid in filling gaps or addressing areas of concern.
- Pay close attention to the position of solar panels during significant rains to capitalize on the cleaning effect. If the panels are stowed in a position to allow rain run off they will be more efficient when the storm clouds clear.
Last but certainly not least, facilities must review the regulatory requirements as dictated by their site specific Storm Water Pollution Prevention Plan (SWPPP) to gain a detailed understanding of expectations for water retention and pass-through, sampling frequencies, testing and record retention. With this knowledge, the next step is to create a Standard Operating Procedure (SOP) for wet weather events, and develop personnel training so that adherence to the SOP becomes procedure driven companywide. Implementing this plan allows contractors in operations and maintenance time to set up vendor support agreements to assist if the water intrusion is more evasive than the site and staff can effectively manage.
We may not be able to predict exactly how much rain El Niño will bring, nor how it will affect us, but what we do know beyond a doubt is preparation now will reduce potential damage. At the very least El Niño will bring more vegetation this spring so long term vegetation management plans should also be in the works.
Original Post: Harvey Stephens
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