John C Daley

If the plan still involves removing the leaf matter at the bottom of the pond, its possible to make a mechanical device to do so.
The image shows a traditional dragline bucket, but I am suggesting a much smaller one built with a steel frame and steel mesh with say a 4 inch , 100mm holes.
With a pulley system set up it could be drawn across and back the pond floor scooping out the muck in one direction only for simplicity.
Ground stakes can be used to hold the pulleys and as the pond is cleaned the pulley system is moved sideways to the next stake.
A petrol motor with a pulley and a clutch would be the tractive power.
BUT here is an easier unit.
And this is a place to purchase this equipment
www.muck-n-weeds.com

Craig, very clever arrangement, well done!

Cecile, What are CAFOs please?

From;A study in Iowa
"Results
Detection rates for individual herbicides ranged from 0% for metribuzin and cyanazine to 95% for 2,4-D (Table 1).
One or more of the six agricultural herbicides were detected in 28% of homes, whereas the four long-term–use herbicides were detected in 43% of homes.
A few herbicides with high use (e.g., atrazine) were not detected frequently. Metolachlor was the most frequently detected herbicide in the agricultural herbicide group, whereas dicamba was the most frequently detected among the long-term–use herbicides.
All homes with detections of one or more of the agricultural and long-term–use herbicides also had detections of 2,4-D.
The concentration of 2,4-D was > 2-fold higher than any other herbicide. Herbicides with the highest geometric mean concentrations were 2,4-D, dicamba, pendimethalin, and acetochlor......."

In another topic Benefits of rainfall collection
questions about overspray from cropping and its potential effect on rainfall collection was raised.
From; water tank health
I found this "Pesticides – agricultural pollution
Use of pesticides and potential drift from agricultural areas has been the subject of increasing public concern, and one of the issues commonly raised has been potential contamination of roofs used as catchments for rainwater tanks. There have been complaint investigations but pesticides are rarely detected and, where they are, concentrations are well below health-related guideline values (South Australian
Department of Human Services, unpublished results).
In surveys of rainwater quality in rural areas, most samples did not contain detectable concentrations of pesticides (Victorian Department of Natural Resources and Environment 1997; Fuller et al. 1981; Paskevich 1992; New South Wales Environment Protection Authority and Northern Districts Public Health Unit 1996; Chapman et al. 2008). Endosulfan, profenofos, chlorpyrifos and dieldrin were detected in some samples, but all at concentrations well below health-related guideline values cited in the ADWG.
If in doubt about the use of pesticides in a particular area, advice should be sought from the relevant agriculture, environmental health or environment protection agency.
Slow-combustion heaters
Concerns have been expressed about the potential impact of emissions from slow combustion wood fires on rainwater collected in domestic tanks. Public complaints have ranged from reports of a slight burnt wood taste to tainting with creosote. However, in a survey of rainwater collected from roofs incorporating wood heater flues, polyaromatic hydrocarbon (found in combustion products) concentrations did not exceed guideline values in the ADWG (Victorian Department of Natural Resources and Environment 1997).

Thats Ok Dave, I see opportunities for action everywhere compared with others.

You seem to be creating logs in you path to ensure nothing will work.
I realise farming over spray is a major issue, and in terms of rainfall collection I am baffled about what to do to create good result with water at this stage.

Other farmers lament the loss of good arable land to a solar farm, of course

I am with the farmers on this point, its wasting a great resource.
Have you moved into this farm area, not understanding what goes on in them?
In Australia I have seen city folk buy a small block in farm zones and complain about farming operations, cows mooing etc and actually shut the operations down.
I hope this does not apply to your goodself.
Bird poop and dust are all handled with diverters and large volume tanks.
If you have a basement tanks can be installed there to prevent freezing, I have helped a few people create such items, it is very economical.
The chemicals are the obvious issue. I will follow up the issue. https://permies.com/t/173913/Farming-overspray-rainfall-collection
Water can be hand pumped or use a backup battery system, even a generator which may be good for lighting as well!

I do not agree with your pessimism David.

When you modify it you will need to get an engineer involved to size out any extra reinforcing required as well as the cement beams for the now suspended slab above the coldroom. To do it you would excavate the room, pour footings, form up the walls, pour them, strip it out, insulate, moisture proof it then backfill and compact ,then form the ceiling and beams, then move on to the slab tying in all the rebar from the walls.

None of these issues are a major issue, moisture proofing is not needed, any additional reinforcement and tying can be easily handled, additional design work will be minimal.

I am surprised by the comment

Seems like it would eliminate one of the great tensions of beekeeping - how often to open a hive to ensure things aren't running away, vs how often you really want to upset the bees.

I did not know about the "Society for the Preservation of Calm Bees [SOPCB] ", nor did I realise that opening the hive caused sufficient issues for the Society to exist!

Have you done any research on the matter?
What area are you planning to build so the trees can be investigated.
Do they rot?
From Uses of Balsam fir timber
"What are balsam trees good for?
It has good pulping properties and is used principally in the manufacture of pulp.
Balsam fir is also widely used for interior knotty paneling, fish box construction, crates, cooperage, millwork, and similar products not requiring high structural strength."
https://wildadirondacks.org/adirondack-tree-list.html
HEMLOCK from; /white-pine-hemlock-mill-run
Is hemlock wood durable?
Hemlock is locally widely used for raised garden beds, fencing, and barn construction and repair. There is no guarantee as to how long the wood will last in the ground, but in the right conditions, some people report that it lasts 5 to 7 years.
USES OF RED MAPLE
https://www.ehow.com/list_7257748_uses-red-maple-trees.html
CHERRY
uses of cherry wood
SPRUCE used here for a log cabin https://ownwoodenhouse.com