I present the motivation, design, and latest results of the
Observations of Redshift Evolution in Large Scale Environments
(ORELSE) Survey, a systematic search for structure on scales greater
than 10 Mpc around 20 known galaxy clusters at redshifts of z >
0.6. When complete, the survey will cover nearly 5 square degrees, all
targeted at high-density regions, making it complementary and
comparable to field surveys such as DEEP2 and COSMOS. I describe the
large scale structures that have been photometrically and
spectroscopically confirmed so far through this program. In
particular, I focus on the multi-wavelength studies of the Cl 1604
supercluster at z = 0.9, which contains at least eight clusters and
spans 10 Mpc by 100 Mpc. I will describe the filamentary structure of
this supercluster, the galaxy properties as a function of environment,
and the large population of (optically-innocuous) active galaxies
detected through radio, mid-IR, and X-ray observations. The physical
processes responsible for star-formation, starbursts, and nuclear
activity in these intermediate-density regimes and the implications
for galaxy evolution will be discussed.