Well, interesting.....based soley on the info provided I'll come down in agreement with Azreal. Quercus raises some very interesting and valid points to which I'll adress in a bit.
We (should) all know that where ever we might be the importance of bigger older trees is clearly recognised and acknowledged by the various planning controls that provide direction and guidelines as to what is seen to be best practice re trees and development. (This is as true here in QLD as it is in the USA or in Europe) Balancing how we can achieve these seemingly contradictory desires is a big part of what we do as consulting Arborists.
Azreal is so right when he says remember who the reader is.....with trees lkike these I'd be going out of my way to ensure that the client understands what value these have and why, prolonged interaction/communication site visits etc...
Coming in after all the plans are approved for the driveway or turnaround area would be a pain but not insumountable. There are a great number of closed cell containment systems that permit the construction of at grade road base with dramatically reduced compaction impacts...they are part of the best practice specs in the UK for works within the critical root zone, and when the traffic load is to be limited to domestic single lane they are a useful option. Suspended roadways are very expensive and always face big opposition on the part of the developer/builder.
Always remember that these trees have a definable dollar value, and more they have a significant real ongoing cumulative economic value (think temp/water cylce/carbon cycle) to the locals in the street/suburb the council even the state government....if the client (tree owner) is to bear the cost of retention and the local community and beyond are to gain the benefits this places the client in an advantageous position re the LGA.
How these trees fit into the larger ecology of the area is critical are they part of a definable corridor, or are they islands...do they represent local provinance, just what are the species at all trophic levels that utilise the trees as habitat,and what are they're significance. All these elements assist other players in recognising the value of the trees (again reiterating what Azreal said part of our role) and raise the profile of the trees.
Quercus poses a number of questions that need to be adressed I think...
1. The situation will worsen...I'm thinking he means that over time the visible defects within the structure of the tree will become more problematic...
Well it really is not that difficult nor expensive to reduce the wieght of severely compromised limbs...though I would be presenting the arguement to retain as much living biomass in these trees as possible and practicable. Dynamic fall arrest systems are being used in suignificant trees in our State, and they should be used more often. Branches will always fail on all trees, if moving the target is impossible (which I doubt!) then having a dynamic cabling system that will prevent identified branches and limbs from hitting the ground is a good solution.
Protecting the soil and roots is the key to protecting all trees and yes this will impose greater costs on the client than any restorative canopy works!
are the trees worth it? Based only the pics we've seen hard to say, but for the sake of developing the example lets say yes.
2.The ability and willingness of the owner to pay future costs of maintenance and management....
Always a tricky one since we have no say over what future tree owners/property owners amy or may not do...al we can do is provide them with the best advice in relation to our assessment of the trees they own, help them to see through our eyes and understand the tree through us....if we are successful we will ingender in them a appreciation of the huge importance and $$$ value they have in their living assets....beyond that we can do no more...the trees are theirs to do with as they want (within the controls of relevant legislation!!!)
If you spend the time (yes always with the time how much!!!
we never get those hours back!!!!!) and make a connectrion with the client on some level Environmental $$$'s community/cultural/historical/etc.... there is a muchgreater chance that they will make a commitment to future management.
3. Area too great to minimise the threat...
Well there is always a threat from every tree...even cut doen on the ground (trip hazard..chip and dust hazard!)
The tree owner has to weigh up what they gain from their trees against the real...not percieved...risk of significant harm.
I would suggest Quercus that you are thinking the tree is liable to fail at the base to feel removal is the only reasonable option in this case...now that might be the case (failure at the base that is!) but I don't see enough evidence from the info we have to make that call.
Retaining and managing older trees (and these
Euc tereticornis are not that old!!) does not mean that you don't plan for the future succession planting should be part of the consultation for sure.
Also older trees require regular monitoring, fall arrest systems require annual checks, we need to loose the mind set that we write the report submit get the $$$'s and walk away..never to be seen on site again till the trees are to be removed!!!
Becoming the solution to the the clients tree issues will always be long term since the darn things want to live soo long!
I don't believe its too expensive, and given the opportunity will happily spend good drinking hours trying to show clients why I think that, both in reports and in person.