Construction Update: Perry Homes Adding Storm Sewers, Berm to Woodridge Village
Here’s a construction update for Perry Homes’ Woodridge Village, the stalled development implicated in flooding Elm Grove and North Kingwood Forest twice last year.
On January 25, 2020, I flew over Woodridge Village. Not much had changed since my December flyover. However, Perry Homes, had concreted about 280 feet of Taylor Gully on the east side of the development facing North Kingwood Forest. And they started to build a berm between Woodridge Village and Elm Grove. Finally, they have started prep work for building more streets. See images below.
Overview of Construction Activity
Slanting Berm Between Elm Grove and Woodridge
Since the January flyover, Perry Homes has continued to build up a berm south of the S2 detention pond. The height of the berm is about 3-4 feet immediately west of Taylor Gulley (grassy channel in lower right). It tapers down to nothing before you get to Fair Grove Drive, one long block to the west (out of frame to the left in picture above).
Whether Perry intends to build up the western portion of the berm is unclear. If they intend to go west beyond the point above and continue the berm south of the S1 pond, they have not yet done so.
The Strange Case of the Elevated Swale
Originally, I thought the berm might be the missing maintenance road that Montgomery County regulations specify around detention ponds. However, yesterday, Perry Homes’ contractor etched a ditch in the middle of the berm. I guess this ditch will act as the backslope interceptor swale, another requirement of detention ponds in Montgomery County.
Such swales channel water into ponds through pipes installed at low points. Their purpose: to prevent runoff from surrounding areas from flowing over the edge of ditches and causing erosion.
Except in this case, water from the surrounding areas would have to flow uphill several feet to get to the swale. So the swale will only channel water that falls directly on it.
No New Detention Ponds
No new detention ponds have been created since last August.
Prep Work for New Streets
However, Perry Homes is starting to add new storm drains to areas where roads have not yet reached on the north side of the S2 detention pond.
Perry Had Promised No New Streets Until All Detention Ponds In
Point #1 in Perry Homes’ letter to the City Attorney about remediation efforts promised that Perry would delay additional street construction until three detention ponds on the northern part of Woodridge Village were complete. But as you can see from the first photo above, no additional detention ponds have even been started on the northern portion of the site.
Possible Impact of Changes on Flooding
The concrete channel will reduce erosion, but will do nothing to reduce flooding. As you can see from the video below, taken by Jeff Miller after a minor rain, Perry Homes needs the three additional detention ponds they promised in 2017, two and a half years ago, to reduce flooding.
The berm may redirect flooding. The berm has the potential to change the location of flooding. As floodwaters build up in the S2 pond shown above, they will eventually rise above the overflow channel between the concrete portion of Taylor Gulley and the pond. When that happens, the water will go around the berm. It could happen on two sides. On the west at Fair Grove (above) and on the east at Taylor Gulley (below).
On the east side of the concrete portion of Taylor Gulley, notice how the edge slants down toward North Kingwood Forest (out of frame on the right).
Once floodwater gets into North Kingwood Forest, experience has shown that it will flow through streets into Elm Grove, bypassing Taylor Gulley.
Storm sewers, once connected to the detention ponds, will simply shorten the time of accumulation after heavy rains and fill the ponds even faster. That usually results in higher peaks. Again, without additional detention, there is no flood-reduction benefit for downstream residents.
Posted by Bob Rehak with help from Jeff Miller on 2/9/2020
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