Westmoreland County received 72 inches of precipitation in 2018 — nearly double the 40 inches the area normally receives.
What happens to all that water?
Some of it gets absorbed into the ground. Some of it evaporates with the help of plants and trees. And some of it just runs off.
Where the water goes is one of the major concerns of the Westmoreland Conservation District, which saw a record level of activity in 2018 and is expecting more of the same this year.
“We’re seeing the same thing — lots of flooding, stream bank erosion and even delays in construction projects,” said Gregory Phillips, district manager and CEO. “We’re on pace to maybe not quite do the 72 inches, but it’s going to be above normal.”
Westmoreland County has had 32.4 inches of precipitation so far this year, although individual weather stations show local variations, according to the National Weather Service’s Pittsburgh office in Moon.
The New Stanton station recorded 28.8 inches as of Wednesday, compared to 32.69 inches by the same date (July 10) last year. This year’s rainfall has been 9.3 inches above average, according to NWS.
That has led to a host of water-related problems, including flooding, stormwater runoff, sedimentation buildup and streambank erosion, Phillips said.
“The rain impacted each and every one of our technical program areas, and our staff spent much of their time responding to the record number of phone calls from landowners who were experiencing problems,” the WCD 2018 annual report said.
Among the annual report’s findings:
• So much water collected underground in abandoned coal mines that it came shooting out in at least five places in Irwin.
• Linn Run exceeded its banks and damaged several buildings of the Valley School of Ligonier.
• A floodwall collapsed in South Greensburg.
• Farmers lost crops because the fields were too wet to harvest.
• Timber harvesters and commercial developers delayed their project schedules.
• The almost continuous presence of standing water increased mosquito populations in the county.
The Latrobe/Derry site of the Pennsylvania State Climatologist recorded 14 days when the amount of precipitation set a record in 2018.
The conservation district is tasked with reviewing plans so that new development does not exacerbate stormwater runoff. Two hundred such plans were reviewed in 2018.
“A developer is required to store runoff to ensure it doesn’t do damage downstream … through the use of retention ponds and storage tanks,” Phillips said.
The district reviews plans for projects exceeding one acre in size by comparing runoff levels before and after construction. Things such as buildings, roofs and parking lots can lead to higher runoff levels.
Now in its 70th year, the district has reviewed an estimated 10,000 stormwater plans over its lifespan, Phillips said.
About 5% of the land in Westmoreland County sits in a 100-year floodplain, meaning it will flood after extended periods of rain. Whether communities have floodplain management regulations can affect the availability of things such as flood insurance and home mortgages.
“Municipalities can protect their communities from flooding by adopting and enforcing regulations … that provide a standard for how the land in floodplain areas is used and developed,” according to the annual report.
Most stormwater controls are built to handle average amounts of rainfall, plus the occasional big storm. Because of Westmoreland County’s silty clay soil, only 10-12 inches of precipitation sinks into the ground. Another 20 inches is handled through “evapotranspiration” from trees and plants.
In 2018, that still left 40-plus inches with nowhere to go except to run off “down streets, across yards, into storm sewers and already swollen streams. Much of it found nowhere to go except places where it wasn’t wanted, like basements,” the report said.
The fact that Westmoreland County is still heavily agricultural and 50% forested helps reduce the incidence of flooding, Phillips said.
“Those forests are sponges — they absorb a lot more water. Without that, you’d see a lot more flooding,” he said. “I like to say that we’re 65 communities in Westmoreland County that are surrounded by forests and farmland. That helps us a lot.”
The conservation district is hoping that Westmoreland County commissioners will adopt its Integrated Water Resources Plan later this month. The plan assists in the management of the county’s water resources and includes a model stormwater ordinance for municipalities.
Phillips noted that the district has had an “enormous” impact on excess runoff and flooding through the development of municipal stormwater ponds; residential rain gardens; permeable parking lots, plazas and sidewalks; vegetated buffers along streams; and gutters and downspouts on farms.