By Roy L Hales
The last four years of drought have left many Californian renewable site unprepared for the return of wet weather. Dry lake beds, which can be vulnerable to flooding once the rains come, are often used for renewable sites. Wind turbines are built into terraces on mountain passes, that are vulnerable to erosion. According to Harvey Stephens, Vice President of Operations at World Wind & Solar, there are ways of preparing renewable sites for El Nino and other weather events.
Preparing Renewable Sites For El Nino
“Back in the 1980’s, the weather used to take us by surprise almost every year. We’d get an inch of rain in one day and it would grind the whole facility to a halt,” said Stephens.
The worst he’s seen was in 1997 – 98, when:
“We’d get El Nino events of three to four inches on a facility that was about 1,200 acres, but those at 1,200 acres only had about a sixty foot vertical drop. These large solar fields become collection points. As the water fell on them, it did not seep into the ground. It began to sheet and gets into water passages, washing them out. We were standing on a roadway in the Mojave desert watching foam six to seven feet above what is normally dry ground.”
Ensure that Water Drains Off
“You can spend your money preparing for this kind of event, or spend it making repairs,” he said.
The first step in preparing a site against the weather is making a careful analysis of the site and its’ potential weaknesses.
One of the keys is to ensure that water can drain off without damaging the site. That entails an annual inspection and cleaning up of drain grates, catch basins, inlets, channels and roadways. Low spots, breaches and breakage points need to be fixed so the system remains intact. Use good lighting when inspecting culverts under roadways because obstructions can act “like a beaver dams” and flood sites during a weather event.
“If you have had a storm before, make an inspection to see where the build-ups occur,” suggests Stephens.
Divert the Water
Another tool in the site’s arsenal is to divert water, so that it flows around the site rather than through it. Sometimes a well placed diversion (dirt berm) may be all that is needed to avert damage from a mudslide.
Alternately, a Tiger Dam section spans 50-feet and can be installed in a few minutes. These water-filled bladders can be used individually, or linked together to form a continuous barrier to protect larger areas. After the need is over, Tiger Dams can be put into storage until the next time they are needed.
A Protective Blanket
Grasses, windflowers and other materials can be deployed as a protective blanket to stabilize areas disturbed by grading operations,as well as reduce loss of soil due to the action of water or wind,1 and prevent water pollution.
“These are practices that have been proven to be effective for managing erosion. Our best maintenance for stormwater pollution prevention plans are the installation of straw waddle, where you have movement of water, to help stop silt. We have hydroseeding on slopes and the use of acrylic co-polymers or other dust palliatives in areas where you have water sheeting to prevent erosion of the soil,” said Stephens.
Hydroseeding, or drill seeding, a native species is an effective way to apply seeds. This should be applied prior to expected rainfall, which generally means between October and March. (Seed planted after that will remain dormant until the next moisture cycle.)Some facilities that Stephens hydroseeded last December are now ready to be mowed.
Some Additional Preparation Steps
- 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.
“Most people don’t realize that they need to maintain these systems. Every time water flows through your site, it is bringing silt. filling it up and diminishing its ability to operate as it was designed. Then when you have a big event like this El Nino, or even a one or two inch event in a couple of days and it is too late,” said Stephens.
“If you don’t have the manpower to maintain your site, set up a contract or a work relationship with a local service provider who will do that for you.”
For more information, please go to www.worldwindsolar.com.