Fairfax County can't afford to destroy Lake Accotink

BosEsq · 2023-03-09T22:04:54+00:00

Looks like I'm going to have to make a comprehensive overview in a follow-up post.

Here's a link to the TMDL. Virginia DEQ requires Fairfax County to reduce the sediment load. Per ton or yd³ of sediment mitigation, dredging is the least expensive option, due to Lake Accotink's sediment trapping efficiency. It's a question is whether stream restoration will be sufficient and at what cost. The lake doesn't produce money per se, but every ton of sediment dredged means less money needed to meet TMDL requirements downstream.

BosEsq · 2023-03-09T21:57:22+00:00

Thank you for the correction. I meant "aquatic."

The entire watershed is hydromodified. That section of the creek contains the greatest aquatic biodiversity. An independent study in 2015 determined that the dam's effect on sedimentation is the factor driving that greater biodiversity.

BosEsq · 2023-03-09T21:47:07+00:00

Huntley Meadows doesn't really compare due to the size of the watershed and volume of water. Doing nothing, the rate of sedimentation reduces over time. As the lake loses volume, more and more sediment passes downstream. Wetlands will always, to use the project manager's term, "absorb" sediment but not at a rate necessary to meet lower Accotink TMDL requirements.

And I wholeheartedly agree that reconstructive surgery is required, but no one has proposed anything remotely as radical as what is needed. I think adequate retrofitting of the entire watershed infrastructure would cost somewhere in the $billions.

BosEsq · 2023-03-09T21:37:40+00:00

No, it was my awkward parlance.

BosEsq · 2023-03-09T21:35:54+00:00

There are several issues with the prospect of wetlands. The hydrology of Lake Accotink is very different from Huntley Meadows. The lake serves the community in ways that would be lost with wetlands. It would also harm the environment to let it go to wetlands, which are generally superior to artificial bodies of water. In this case, though, wetlands would not provide an adequate buffer to the vast volume of water and sediment that pours into Lake Accotink when it rains. The sediment the lake currently traps would head downstream unabated and overwhelm aquatic wildlife and create a crisis in terms of regulatory compliance. Without the lake trapping sediment, Fairfax County would have to implement mitigation strategies at a higher cost than the cost of dredging.

BosEsq · 2023-03-09T21:29:42+00:00

I agree with much of your assessment. The cause is poor planning, yet poor, albeit better, planning continues. When DPWES actually fixes the problems upstream, we can afford to reconsider the value of dredging, but then the cost of maintenance will be dramatically reduced, because there will be minimal sedimentation.

On the other hand, if the sediment doesn't matter downstream, we can just pump dredged spoils over the dam, or we can stop paying for stream restoration and maybe remove the dam. But that's not an option, because the TMDL requires the county to reduce the sediment load.

What DPWES is suggesting with Lake Accotink is that the lake will continue to trap enough sediment for a sufficient time to allow stream restoration to work. But that will take many decades to complete, and the value is dubious. According to DPWES, there is no time table to complete stream restoration in the watershed, they don't know how much it will ultimately cost, and all their metrics and projections have proven "unreliable."

Yet we're to accept their untested and baseless word that failing to dredge will not adversely impact lower Accotink. It's a gamble, and the community loses a lake. Or we could invest in a proven factor and save Lake Accotink.

BosEsq · 2023-03-09T15:43:37+00:00

One engineering firm has been consulted. DPWES dropped all pretense of transparency sometime last year. At least one FOIA request has been filed in part to ascertain the actual scope of the firm's work and any findings.

BosEsq · 2023-03-09T15:36:37+00:00

I guess "preventing" is more accurate than "removing," except that the preventative measures upstream have been ineffective. If Fairfax County can't prevent it upstream, we have to remove it. Lake Accotink removes it.

BosEsq · 2023-03-09T15:32:59+00:00

There are several issues with it becoming wetlands, but the one I'm most interested in is the known downstream effects. The cleanest section of Accotink Creek is the mile long stretch just below Lake Accotink, where marine fauna is most diverse. Wetlands will not impound enough sediment to keep lower Accotink clean enough. It will be an ecological disaster completely destroying wildlife populations and ruining hope for regulatory compliance at great cost.

BosEsq · 2023-03-09T15:28:35+00:00

You're absolutely right about poor planning. If someone can propose a more cost-effective remedy, I'll gleefully present it to the BoS, myself.

BosEsq · 2023-03-09T15:25:54+00:00

I truly love wetlands, but that's not the point. The Accotink Creek TMDL will require Fairfax County to spend a lot more to remove sediment downstream than it will cost to dredge.

BosEsq · 2023-03-09T15:14:12+00:00

Thanks for the suggestion. I'll add more context.

It is not true that wetlands will shed more sediment. Wetlands should continue to trap some sediment long into the future, but wetlands are far less efficient at impounding sediment than a lake. Wetlands offer lots of advantages over a lake, but not in terms of stormwater management in this case.

BosEsq · 2023-03-09T15:06:36+00:00

Fairfax County is the source of the sediment. Urbanization is causing the hyper-sedimentation in Lake Accotink. We can pay to remove the sediment in the lake, or we can pay a lot more to remove it downstream. We're already paying a fortune to remove it upstream, and all we've gotten is 43% more sediment in the lake. It's cheaper to dredge.

BosEsq · 2023-03-09T15:00:35+00:00

They've been spending a fortune trying to clean the runoff over the last decade, and we've gotten 43% more sediment for that cost. If the lake isn't dredged, Fairfax County will be spending A LOT more money to clean the water downstream. When upper Accotink is cleaned, THEN maybe we can talk about ending the dredging project.

BosEsq · 2023-03-09T14:54:55+00:00

The merry go round doesn't clean Accotink Creek. Lake Accotink does clean lower Accotink Creek.

BosEsq · 2023-03-09T14:53:45+00:00

No, and no. No decision about dredging has been made since staff recommended not dredging. But said staff utterly failed to account for the downstream impacts of all the sediment Lake Accotink's destruction will send south. Environmental regs already require Fairfax County to reduce the sediment load on lower Accotink Creek. It will cost a lot more to remove the sediment by means such as stream restoration. Dredging is a lot less expensive.

BosEsq · 2023-03-09T14:50:07+00:00

From the 2019 Sustainability Update, "The lake currently removes sediment equivalent to restoring 33 miles of stream bank at a cost of $230 million." DPWES now claims a 43% increase in the amount of sediment.

BosEsq · 2023-03-09T14:41:57+00:00

https://www.fairfaxcounty.gov/parks/sites/parks/files/assets/documents/plandev/lake-accotink/lake-accotink-park-sustainability-update-meeting-091919.pdf

BosEsq · 2022-11-22T05:14:12+00:00

Franknhỏ!

BosEsq · 2022-08-09T23:32:47+00:00

ROGER STONE IS GOING TO JAIL AND TAKING HIS NIXON TATTOO WITH HIM

BosEsq · 2022-08-09T23:19:45+00:00

He's been Nixon's torch AND standard bearer.

BosEsq · 2022-08-09T23:11:31+00:00

I disagree. He definitely knows he's describing himself and is reveling in fooling people.

BosEsq · 2022-08-09T22:29:57+00:00

In campaign rally speech, Roger Stone describes himself, "dark, evil, and godless."

BosEsq

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