Truesdale Lake  

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: Both 12″ siphons shut down: the west 12” on Tuesday night 11/5/19 and the east 12” on Wednesday night 11/6/19. The 6” siphon was the only one flowing most of this week and it was able maintain the lake level following 0.3″ rainfall with a 2 ½” lake level rise. Lake Gauge started at -3.0′ target depth and ended the week rising to -2.8′. 

The intake head of the west siphon is 9” below target depth and the east siphon intake head is 17” below target depth. Both developed widening whirlpools above the intakes and this is likely what shut them down. We need to figure out something that eliminates the whirlpools over the intakes. Internal baffles and external fins are two ideas to reduce or eliminate the whirlpools above the intake heads. External fins in second diagram would be easier to construct and less restrictive to the flow. Experiment with this design first.

External fins with the fin “trailing edges” leading out from the siphon intake head.Experimentation will determine minimum number of fins necessary to eliminate a whirlpool – i.e. eight or fewer fins.
Daily Observations:

TUE     11/05        LG -2.9’        All siphons operating with west whirlpool widening. West siphon shuts down that night.
WED    11/06        LG -3.0′        Target depth achieved once again after the October 10th departure from our last target depth achieved.
THU     11/07        LG -3.0’        Both 12″ siphons have shut down. Scot took measurements of these siphons to provide to Cliff Munz, who is working on a large construction project and cannot convert the siphon design to CAD at this time.

FRI       11/08        LG -2.9’        LLR begins with 0.3″ rainfall. 6″ siphon operating at 125 CFM. 
SAT      11/09        LG -2.8’        Inflow continues to exceed outflow 
SUN     11/10        LG -2.8’        Outflow matches inflow with 6″ siphon flowing

MON    11/11        LG -2.8’         As above. Sue Enos schedules Lake Planning Group Meeting for 11/20/19.
Scot

Email from Michael Lombardi, South Salem Fire District Commissioner, regarding the dry well on the north end of Lake Truesdale near Indian Lane and the Dam.

Dear Skip, 

The board of fire commissioners is weighing options to repair and extend the dry hydrant pipe in Lake Truesdale. We have the following questions.1. Will the lake draining program be an annual process or is this the only year it will be done. 2. Is the lake going to be drawn down further. 3. When will the lake be refilled. 

Thank you in advance for your assistance feel free to contact me. 

Michael J Lombardi                                                                                                       Fire Commissioner (914) 588-8270

Thank you for contacting us Michael. We will be planning to do the lake drawdown annually as a way to better control weed growth and overall health of the lake. 

The drawdown is at the expected level at this time with only one smaller siphon running to maintain the target depth with expected normal rainfall. 
The drawdown will last until February 1, 2020 – that’s when we will turn off the maintenance pipe. This is the smaller 6″ pipe which we will use to try to keep the lake level 2.5 – 3 feet below the spillway level. 

After then the lake will fill up with winter snowmelt and spring rain. We anticipate it will be back to regular height by May 1, 2020 and likely well before then.

More information on the drawdown is published on the Truesdale Lake web site - http://truesdalelake.com

Thanks for your support,
Skip Jahn

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

Summary: Harold Ossher’s conclusion, following his evaluation of watershed research and flow data collected, was to use two 12” siphons plus the one prototype 6” siphon. This proved sufficient to stay ahead of this year’s wet October 8.2” rainfall total. (Average rainfall for October over the last three years is 7.7″ where OCT 2018 was 4.6” and OCT 2017 was 10.3″.)

When drawdown depth is achieved once again, I will gather the measurements of the siphons constructed on scene so that Cliff Munz can revise and convert my design drawing to CAD. 

Thursday 10/31/19 brought us a wicked double cold front for Halloween, delivering 1.01” of rain over 28 hours with strong wind gusts. In advance of the storm, James Gorman of P&LC restarted the west 12” siphon at 0930 EDT ~ providing a well timed response before the rain accumulated, before inflow exceeded outflow and before the two cold fronts passed with freezing temps. All three are flowing again at 1,100 CFM and the cause of the 12” shutdown was not identified. The lake gauge reading at restart was 2.2 feet below the spillway. 

Following the last report, the lake gauge was -2.0’ and ended the week nearly one foot lower at -2.9’ with siphon flow exceeding inflow after the 1.15“ of rainfall we received for the week.

Daily observations: 
TUE   10/29      LG -2.0’     Rob Cummings consolidates all reports, photos & responses to the lake’s website: http://truesdalelake.com/tag/drawdownreport/ in order to keep everything out in front of the inevitable questions.

WED  10/30      LG -2.1’     A steep pressure, temperature, & humidity gradient cold front approaches from the west.  THU   10/31      LG -2.2’     James Gorman restarts the west 12″ siphon ahead of the storm.. All siphons flowing.

FRI      11/1       LG -2.1’     LLR from 1.01” rain received. Inflow exceeds outflow. 

SAT     11/2.      LG -2.2’    30° F with first frost of the season. Outflow exceeds inflow for remainder of the week. 

SUN    11/3.      LG -2.4’     A long stick is caught in the east 12″ siphon intake, but it is still drawing water.

MON   11/4.      LG -2.7’     Whirlpool increases in diameter over west 12″ siphon intake which is shallower than the east siphon. This is still flowing but will shut down first.

Good morning Harold,

Here is my precip report for this year which includes JAN through SEP for a total of 37” (plus the 8” we received in OCT).

The report also shows the 30-year average for each month. (The thirty year average for OCT is 4.6” and we received 8.2” this past OCT, making your siphon determination of two 12” + one 6” right on target!)

I listed the links in preference order with your favorite format first.

–Scot

Many thanks, Scot, great to have this data.
BTW, I was wondering whether fins at and extending a bit beyond siphon intakes, like the bottoms of rockets, would help with the whirlpools? On the other hand, I think we reached target depth with the large siphons still running, so we might not want to keep them going longer.
– Harold

Hi Harold, 
This would very likely work to prevent whirlpools from forming above the perfect circle at the intake heads. I wonder if there exists such an attachment for PVC pipes. Maybe James will fabricate and patent his invention! Here are the baffle diagrams for rocket engine nozzles:

[. images did not download for me 🙁 .]

And you’re right, this would be a future consideration for James to consider for siphon improvements to our next drawdown attempt. 

He luckily installed the 12” intakes deeply enough so that the whirlpools shut them down right at target depth. The deep 6” siphon is still running and will help to keep up with the winter inflow and possibly enough to maintain the lake level close to target depth. 

If we get a lot of NOV rain and if inflow exceeds the effectiveness of the 6” siphon, I’ll ask James to restart the two 12 inchers. 
–Scot

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

October 29, 2019

Summary: Sunday 10/27/19 brought us the remnants of Tropical Storm OLGA, where we received 1.34 inches of rain in the twelve hours between 4 am and 4 pm.

During the 24 hours after the storm ended, the lake level rose 5″ even with all three siphons discharging a total of 1,100 CFM. Monday 10/28/19, the west 12″ siphon was observed to have stopped flowing; James Gorman was notified.

Mark Vibert of Main St recommended on the NextDoor site that we try to obtain aerial photos of the exposed lakebed during the drawdown target depth of three feet below the spillway deck. Rob Cummings responded and on Tuesday 10/15/19, he brought a borrowed drone over to my place, where we got some impressive aerial shots and video from several altitudes over the lake.

Ideal weather was enjoyed by the drone on this day before the bomb cyclone nor’easter dumped 3.34″ of rain and the lake level rose 17 inches over the next 3 days. Rob remarked that this demonstrates we’ll have no problem quickly refilling the lake this spring.

Daily Observations: 
TUE 10/22/19   LG -2.0 feet     Harold Ossher observes 6″ siphon not flowing (cause unknown) and one 12″ siphon still flowing at 500 CFM
WED 10/23/19   LG -2.0 feet    0.45″ rainfall received from weak coastal low
THU 10/24/19    LG -2.0 feet    one 12″ siphon matching the inflow rate
FRI 10/25/19     LG -2.1 feet     James restarts two more siphons and all three are flowing by 0845 EDT at 1,100 CFM
SAT 10/26/19    LG -2.3 feet     Siphon discharge exceeds inflow    
SUN 10/27/19   LG -2.4 feet     TS OLGA delivers 1.34″ rain and inflow exceeds siphon discharge
MON 10/28/19   LG -2.0 feet    LLR 4.8 inches as inflow continued to exceed siphon discharge. Equilibrium achieved about 1700 EDT. West 12″ siphon stopped flowing (cause unknown).

Aerial shots of exposed lakebed:: 
The three islands named on the interactive map are WAXWING (north), ANT (center) and PIRATE (south).

A new set of islands became visible during the drawdown. I propose that this set be named BOAT PRANG ARCHIPELAGO or LARA’S GALAPAGOS.

Here are a few aerial photos of the lake from the many taken. I’ll post more this week on a NextDoor thread.

Thanks Scot for this update

Really interesting to watch how this all unfolds

Thanks again

David

Yes, thank you, and to you and Rob for the really interesting photos.
I’m not surprised the lake level rose after significant rain despite the siphons. The watershed is so big that there’s no way they can keep pace during periods of peak inflow. But once all of them are running again, the level should go down fairly quickly again.

– Harold

Love the photos! The “Galapagos” is an inspiring bird sanctuary attracting all manner of feathered friends – picture attached. 

-Lara

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

October 21, 2019

Rain from the strong nor’easter bombogenesis (at least 24 millibar drop within 24 hours) began at 2 pm Wednesday 10/16/19 and ended just after midnight where we received 3.34”of rain. On Thursday 10/17/19, we received a small amount of wrap-around moisture with an additional 0.04” or rain.

At the beginning of the storm, the lake gauge (LG) was 2.9 feet below the spillway deck where it had remained for the past seven days. Rob Cummings also took excellent video and still shots with his drone of the exposed lakebed at this drawdown target level before the storm arrived. Will send some of his choice photos later this week.

Lake Level Rising (LLR) occurred rapidly and rose 17 inches in the 40 hours during and after the storm. This is a multiplier of 5+ times the rainfall.

Keeping in mind that the lake contour is a cone, it would take some severe calculus to convert the rise to the vertical contour of a cylinder.

James Gorman with P&LC arrived early on Friday 10/18/19 and restarted one 12” siphon and the 6” siphon at 8:30 am, which began Lake Level Lowering (LLL) as the inflow from the storm steadily decreased.

Here are the readings taken at the beginning and end of the storm, then every four, eight or sixteen hours thereafter.

10/16      1400 LG -2.9 feet datum (before rain began and followed by 3.38” rainfall from the storm)

              2400   LG  -2.5 feet or LLR     4.8 inches (Immediate Rise)

10/17      0800   LG  -2.2 feet or LLR     8.4 inches

              1200    LG  -2.0 feet or LLR  10.8 inches

              1600    LG  -1.8 feet or LLR  13.2 inches

               2400   LG  -1.6 feet or LLR  15.6 inches

10/18       0800   LG  -1.5 feet or LLR  16.8 inches (Peak Rise &
siphons energized – flowing 617 CFM)

               2400   LG  -1.5 feet or LLR  16.8 inches (remains peak
as siphons match inflow)

10/19       0800   LG  -1.6 feet or LLL  15.6 inches

               2400   LG  -1.6 feet or LLL  15.6 inches

10/20       0800   LG  -1.7 feet or LLL  14.4 inches

               2400   LG  -1.8 feet or LLL  13.2 inches (received
0.33” rain from a weak offshore nor’easter)

10/21       0800   LG  -1.8 feet or LLL  13.2 inches

Thanks Scot! This tells me we won’t have a problem refilling the lake is the spring!

-Rob

Good point, Rob! Meanwhile, it’s good to see the (reduced) siphons doing their job again. Thanks for the detailed measurements, Scot, it’s very helpful to have this tracking of what is happening.
– Harold

These are some of the email reports and communications from Scot Evans from Truesdale Lake, James Gorman from Pond & Lake Connection, and others involved with the project. Putting selected parts up here for all to see what some of the discussion and learning is looking like.

October 15, 2019

Good afternoon James, 

Starting the 6” siphon remains at your convenience. We are maintaining the target depth, where evaporation is nearly keeping up with the inflow. 

During the last 9 days, we received 1.03 inches of rain which was mostly absorbed by the dry ground of West Mountain and surrounding area with little inflow from the Boway Stream:

Summary: over the past two weeks with no siphons operating, we received 1.5 inches of rain with a lake level rise of 3 inches. This is a multiplier of 2 times the rainfall amount. 

We remain in drought conditions with ground absorption and evaporation the overriding factors beyond inflow. When the ground becomes saturated, we will see the multiplier rise rapidly. 

Great. Thanks for the update. I keep driving by every time I am in the area. I am scheduled to hook up the 6″ pipe on Friday. I will probably also fire up a 12″ due to the fact that we will probably get a good rain here today and tomorrow. 

In a perfect world when is the “end date” of the draw down. 

-James

James –

We finally have some impressive storm results to give you after the 3.34” of rain we received last night.

When the storm ended at midnight the lake rose 5.5 inches. 

Eight hours later, my reading just now shows a rise of 9.0 inches. 

So your plan to hook up the 6” and fire up the 6” and one 12” tomorrow is excellent. 

Your plan is great timing too, since by the time you get them flowing, I will have had four full eight hour periods after rainfall ended to report to Harold. 

-Scot

(more detail on this storm is in next report)