How to structure a 70 mile week for a 1:15 half?

I think there's a book coming out with exactly the information you're looking for.

https://www.letsrun.com/forum/flat_read.php?thread=12130781

I'd get up most days in the morning and run 30-40 minutes and then in the afternoon 60-90 minutes. On the days I felt good, I'd pick the pace up a bit (to the barn, etc). Additionally, I'd throw in regular 5-10k races where I ran hard, but not peaking or tapering for them.

If I needed rest or was feeling terrible, I may skip the morning run once in awhile.

Alot depends on your background and where you are in your recent training. In my experience what you have not done is what will help you the most. For example if you rarely do strides you should get those into your program. The half marathon is mainly developing stamina so you cannot really ever do too many miles. 70 is on he low side if you have been running at that level for many years.

Mileage Phase:

*Warmup well before each run: 1 mile jog, drills, 6 x 50 strides. Stretch afterwards.* Run at least 10 miles per day hard-easy. Build your long run up from 11-16 gradually. Of course you want to have days where you run less than 10 miles.
Most half‑marathon runners spend about 4–6 weeks in a base mileage phase before moving into more race‑specific training. Beginners often extend this to 8+ weeks, while experienced runners may shorten it to 3–4 weeks if they already have a solid running foundation

Race Preparation Phase:

Add variety but cut back a little bit on mileage. Sunday - 8K Fartlek (Hills if you can find them.) Monday- AM 5K jog PM 5k jog Tuesday-14 - 16 Mile run Wednesday 3-6 x Mile or 2-4 X 2 miles Thursday AM 5K jog PM 5k jog Friday 8 - 12 Mile Run Saturday 8 x 400 @ mile pace or Hill Repeats *Warmups can be a bit easier every other day, you do not have to do strides every day* If you feel sick, tired, or sore take the day off or do a long walk. You cannot be too careful. Three weeks is a safe amount of time for a cutdown before a half marathon race. During that time, here is what you want to concentrate on:
Mileage Reduction: Gradually cut weekly mileage by ~30–50% compared to peak weeks. Long runs shrink from 10–12 miles down to 6–8 miles.
Keep Intensity: Maintain interval workouts (e.g., 1000m at 5K pace, 400m at mile pace) but reduce the number of reps. This keeps legs sharp without adding fatigue.
Recovery & Rest: Prioritize sleep, stretching, and light cross‑training. Avoid adding new workouts.

Simple approach from a non expert -

Mon-Tue-Thu-Fri AM 4 miles easy, PM 8 miles easy

Wed Alternate 6 mile tempo -or- interval session. For the interval session, alternate 6 x mile with 3 x 2 mile. 3-6 fast strides after the tempo/interval session.

Sat 16 mile long run (progression run: 5 mi easy, 5 mi MP, 5mi goal pace, 1 mi hard)

Sunday off or very easy recovery cross-training

Every 5-6 weeks, replace the long run with a 10K and recalculate training paces based on that.

16 mile long run is completely unnecessary for a half marathon. You will get more benefit from making that two sessions.

70 in 7 days and 60 in 6 days the alternate week. Makes for an average of 10 per day with a day off every other Sunday, etc.—2 workouts in a non-race week, 3-4 week blocks for adaptation/periodization purposes. Sets you up nicely for 1:15. Or faster.

16 mile LR structured “5 easy, 5 MP, 5 goal pace, 1 hard” every week as suggested above is pretty insane. That is a HARD run. A simple 5 easy, 5 at goal pace is a more reasonable load IMO.

And I agree, at 70 mpw I don’t think a 16 mile LR is worth the opportunity cost. As long as you’re routinely doing 10-13 mile sessions (continuous easy runs plus all the 3mi. w/u, 3x2mi. @ race pace, 2mi. c/d type days) you’re set for the distance and are probably better off focusing on the quality of those sessions.

OP - I feel like the first step in providing some recommendation is reviewing the training you’re doing now and have been doing recently. Related to that, there’s a million ways to divvy up 70 miles, so give us some ballpark notion of how you intend to log it (doubles or all singles, rest day or not, depending on your schedule and what you’ve found works for you).

Yes, that might be true for the faster individual who has been running for ten years. Rojo or Wojo had schedules where they ran twice a day and didn't bother to time the runs. He improved significantly that way, but that was just for one year and obviously was after high school and college training.

You can run with air forever, running without air is limited! That is why most high school coaches step immediately into hard interval training for 14 weeks with their kids and still manage to be successful.

Ha, yeah I wondered if that session was a bit aggressive. I wasn't assuming it could be done literally every week, the runner would have to build up to it. Sort of like, if someone hadn't done more than 40 mpw then they would have to build up to the 70mpw, not just start out with it right away. Having said that, that session still might be too hard. Was going for a progression run with a warmup, one pickup at slower than RP, one at RP, with a faster finish.

Generally, 4 days/week is ~1hr easy (8-9 miles), 1 mid-week workout (10+ miles), 1 mid-week easy medium long (10+ miles), 1 long run (13-16 miles). Strides 2x/week. 2 workouts/week works well with this structure -- 10k+ mid-week threshold workout then alternate tempo work in your long run every other week. Weeks without long run quality do a leg speed workout later in the week. That could just be strides or a short stack of 200-400s. Could be more like 2-3 weekends with long run quality to 1 week leg speed. Depends what you need as a runner.

M - 8

T - short interval

W - 8

Th - 8

F - long interval/tempo

Sa - 8

Su - 16 moderate or progressive

I agree with this.

I was in your shoes last season. I ran between 60-70 miles and broke 1:15. After having adopted Norwegian singles, I am confident I would have achieved the time more efficiently and exceeded my goal.

good luck