For this week if you are preparing for a fall marathon you should do 7-8 repeats at just below your marathon pace.
If you you are training for shorter distances 5-6 should suffice at a little quicker pace.
the repeats are 800 meters up the custis trail, from the corner of Oak street and Lee Highway, to the Highway 66 overpass, and obviously 800 meters back down. This workout becomes really long really fast, so be careful not to overdoit at the beginning.
Let's meet at Gateway park, corner of Lee Highway and Lynn street at 6:30. We will go for a 10-15 minute warmup, and then begin the repeats.