Astro Park is located where two major drainage basins drain to Lake Merritt. Historically, this area has been a swamp. A few years back the City Council made an effort to improve the land by adding more sandier material on top. However, they did nothing we can find any evidence of to dig and put in any underground drains to take the water elsewhere.
So when there's rain, the water doesn't leave the area very quickly. Soccer players and volleyballers flee as the land becomes unplayable.
Standing water is dangerous for dogs and people in contact with them. It encourages the growth of giardia (see CDC information here), which can quickly spread from dog to dog when dogs drink water contaminated with feces. Unfortunately "Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection." (source:CDC) which makes it difficult to clean and treat infections once in the population. For this reason, those who give guidance on how to site dog parks (we have examples here and here), and we've also heard this from an Animal Control officer) recommend land with good drainage.
We don't know exactly what would happen if the field were to be covered in inches of brown wood chips when the rains come. It would probably become very muddy and brown wherever people and dogs went. But we did go and see what the land is like right now while it has green grass covering the surface. With the proper boots on, and nobody else using the area, this was great fun.
This video was taken towards the end of March 2011. Proponents seem to think this wasn't taken at the proposed site of the dog run, but they are mistaken.
Longer version, with music!