Am I missing something because I fail to see why this project needs to take so long, in fact it seems do-able by staff from within Network Rail itself.
An extra track at Dore and Totley and a passing loop doesn't seem like too much of a stretch from just general day to day track maintenance?
Okay, a footbridge and platform at Dore and Totley probably needs some contractors, but that shouldn't take till 2023 right?
If we can't get simple stuff like this done within 6 months to a year in a reasonable budget, what "Hope" is there for the rest of the railway?
Sorry, you just haven't got how much planning goes into schemes like this. Planned and planned again, it creates masses of work with nothing actually being seen to be done. Planning started in the days of Railtrack and has been updated and revised many, many times. Various budgets have been allocated, withdrawn, revised and kicked back. Construction standards have been changed, future electrification now allowed for, and most recently possibly dovetailing with HS2. It still won't be good enough at about £145M, minimum.
A loop at Chinley was in, then taken out. 4 fast trains an hour were in the original specification, but there's no room for them into Piccadilly (or Sheffield) so that got reduced to 3.
To ease the way into Sheffield the Heeley loop is to be lengthened and that should be extended further up to Dore as part of HS2. (With slewing it will just fit between Tesco's and Sainsbury's at Millhouses.) There is to be a new freight loop at Bamford requiring considerable earth moving. The extended Dore chord also requires a lot of earth shifting and that is done in the spring-autumn period to avoid bad weather disruption - it gets quite bleak in the Hope Valley in winter.
The Dore platform gets extended back up to the signal*, where it used to be until 1985 when the three other platforms were removed and the one that survived was shortened. The new platform gets a bridge with lifts.
But you're quite right. If relatively modest schemes like this can take so long it's no wonder that HS2 is going to take so long - and Piccadilly Platforms 15/16 hasn't a prayer!
Bats, newts, badgers, birds, plants archaeology, local community consultation, public inquiries, changes of government, priority, new regulations - you name it there's always something to add a new delay.
2005 is when Network Rail can be seen to have consulted Sheffield City Council about reinstatement of the second platform. In 2013 Network Rail spoke of a 56%* increase in passenger numbers from Sheffield by 2029. Since 2013 Dore & Totley has seen that increase in 6 years with over 10 years still to go!
* TPE are soon to operate 6 coaches and and Dore won't be able to take them without SDO methods until 2023. At the present passenger growth rate 9 would be needed by then, but the third fast train will certainly be needed with 6.