Project aims to slow streams, reduce pollution
Effort seeks to stem water cutting into land in York County
Just a few yards past the culvert where Larkin Run emerges, water is flowing so far that it has undercut one of the banks by more than a foot.
Which is why the small York County stream is the latest to be added to the county’s stepped up stream restoration push.
Like other Peninsula localities where former farms have over the past few decades sprouted houses, stores and parking lots, faster-moving water has become a problem.
In York County, for instance, streams that once meandered easily at the edges of fields or woods now scour away their banks — at the county’s first major restoration project, on the Greenspring stream behind Waller Miller Bible Church, it had exposed a Newport News Waterworks water main, said Richard Sutton, chief of operations for the county’s utilities and stormwater division.
At the latest project to go out for bid, to slow down water along 2,000 feet of two branches of the nameless stream behind Bypass Road, erosion is cutting into the path of a sanitary sewer. The low bid on it came in at just under $1 million.
At the same time as erosion worries mount, York, like other Tidewater cities and counties, is under pressure to cut the amount of sediment, nitrogen, phosphorous and other pollutants that rainwater sends into Chesapeake Bay.
Slowing down streams is a big help, Sutton said. It cuts the amount of sediment flowing into the bay, since less soil is eroded. Slower flows mean more time for nitrogen and phosphorous to sink into the ground, too.
Rainwater moves fast, especially since so much suburban and city acreage these days is covered by hard surfaces that shed water, rather than letting it soak into the ground.
Larkin Run, which drains about 50 acres, usually is a trickle of water on a sunny day. Last week, it was already 2 to 3 inches deep and on the move after just a quarter-inch of rain a few days before, said Travis Rhodes, an engineer with the county public works department.
“It’s worse than it was the last time we were here,” he told Sutton.
Sutton is about to launch the multi-month process of designing an answer to Larkin Run.
It’ll involve some complicated math after consulting engineers Brown and Caldwell complete a
detailed survey of some 800 feet of the stream’s upper reaches and to come up with a design.
It’ll likely involve trying to raise the level of the stream and cutting some “S” shaped curves, Rhodes said.
Lowering the banks to create a wider floodplain is also likely, while installing pairings of cobblestone riffles in the stream bed with small pools immediately downstream, should also help.
That’s a large part of what the county’s contractor did along 1,000 feet of the stream that runs through Charles Brown Park.
That work also included installing log riffles in the newly-built pools, as well as planting root wads and boulders along the inside curves of the new S-curves.
The log riffles, like the cobblestones slow the water; the root wads and boulders protect stream banks just where the current of the stream would flow at its fastest.
As the consulting engineers come up with ideas for Larkin Run, Sutton and Rhodes will bring those suggestions back to the several dozen homeowners whose lots border the stream.
The neighbors’ feedback and their concerns about how the work might affect their property.
“We’ll probably go back and forth several times,” Sutton said.
Issues such as trees that might have to come down, land that might be needed for a new S curve or to lower a bank and the logistics of getting construction equipment down to the stream all have to be tackled.
Over by the Greenspring stream, one property owner’s reluctance to lose land to a settling pool meant the county and its consulting engineers decided to install some yard-high rocks to wall in a small section of the creek.
A few yards downstream, where the stream’s eroding force had exposed the water main the county had its contractor install a series of cobblestoned beds, steps and pools. The space there was too tight to try for S curves and widening the floodplain.
A few yards farther on, where the stream had cut its own small S-curve and where one property owner was reluctant to give up on his plantings on the steeply rising stream bank, a single cobblestone riffle and pool slowed things down.
But just downstream from that, a large culver dumped a major storm drain in.
With the recent rain, water raced out of the culvert at a pace not too far off the flow when homeowners water their lawns or their kids fill a glass of water from a faucet.
But the water hit a large cobblestone bed, at which point its surface riffles disappeared and the deep pool beyond looked black and motionless.
It wasn’t completely still, though — for a few yards beyond, it was moving slowly through the new S-curves cut where there had been more space to work.
“It’s been about a year since we finished,” Sutton said. “I think it looks pretty much healed.”