Here are some pictures to go along with my original question:

Front yard with grass installed (doesn't look quite this good anymore)
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View of front curb chase and looking down swale that runs through my yard. The wet area is the last 10-15' before the curb chase drain. You can really see the wet area good in this picture. It's been wetter than this picture would indicate, because I wasn't irrigation my yard when this was taken. My neighbor was (a little), so this water is from his back yard irrigation. In the winter, this area get very wet after snow melts.
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View of curb chase from same direction as the first picture, but prior to yard install:
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This is the cobble lined swale in the back yard, it's also a catch basin, as its 2' deep and the front swale is only 1' deep.
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The water flows under my fence and the fence is raised up about 8" to allow for the 100 year flood, in the even the underground pipes don't work for some reason.

The swale is a backup drainage system, the main one being underground here. It's all within a 30' drainage easement across my property. The inlet (and feeding swales for the hillside) is located on the lot behind mine.

So if I can't resolve the problem, I either leave it as grass or go to rock, or try something different (like this).

I don't think any dry well or grade adjustment is going to fix the problem. A powered sump pump would probably work, but no idea how to do that and have it be reliable and run only when needed.

The problem with rock is that when its left wet like this, it grows weeds and becomes a maintenance nightmare.

So I was thinking -- instead of killing and pulling weeds all the time, or trying to mow (and grow grass) in a bog, maybe growing water loving plants here would make more sense.

It would be nice to turn this problem into something nice looking and like something I INTENDED as apposed to something I have to deal with.

Since Colorado is pretty dry, I have no idea if it would work or what to plant. It's just that xeriscaping is common, but this kind of thing, very uncommon.

Hi Scott,

Nice pictures. They really document your situation.

What you have is a rain garden, not a bog. There's a big difference. Rain gardens receive runoff after storm events (also after lawn watering). Rain gardens get fertilizer runoff from the lawns and can be nutrient rich. Bogs are nutrient poor.

See if your Colorado University has a horticultural extension program or if they support a Master Gardeners group. If so, your extension or Master Gardeners should have a list of rain garden plants that grow in your area. You also need to check with your City (if Castle Rock is a big city) or County zoning office to see what you are allowed to do on an easement. My guess is that the zoning office won't care as long as your don't build a structure or change the runoff grade. But it's better to ask before you plant. Also, bringing in a recommended plant list from the university extension carries a lot of weight.

With that said, my guess is that you can grow sedges, swamp milkweed (they attract butterflies), joe-pye-weed, coneflowers, little bluestem grass, and many more. Try to stick with native wet prairie plants. Native plants will require less maintenance. But you will still need to pull weeds. Weeds will be less troublesome the more that you pull them, but you will always need to patrol the rain garden.

Hope this helps.

Tom

I now an offer from the developer that was submitted and approved by the town -- that I can pretty much take or leave. They want to install a concrete "trickle pan" and then surround it with landscaping to make it more attractive. I'm leaning toward accepting it, but wonder if (A) I should have it done now, or in the spring ... (B) What we be the best choices for the ornamental grasses ... and (C) What would be good choices for the perennials? Also, would bulbs makes any sense here?

Here are is the plan I am looking at:
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And also
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Hi Scott,

You have an excellent plan!

It's likely that your plan is going to set a standard for similar sized gardens in your town. It's a real quality design. The developer did a great job.

As for plants, I'll give you a few native plant ideas.

Native Grasses:

Little Bluestem, Schizachyrium scoparium. Nice clump forming grass that grows to 3 feet tall. Pretty orange gold cast to the stems in fall. Good winter interest.

Prairie Dropseed, Sporobolus heterolepis. Short round clump forming grass, maybe 1 foot tall. The tiny grass flowers smell like pop corn when they bloom in summer. Attractive low grow grass.

Native Forbs:

Swamp Milkweed, Asclepias incarnata. Showy reddish pink blooms that attract Monarch butterflies. Can be challenging to establish. It loves wet soil.

Blue Wild Indigo, Baptisia australis. Showy bluish purple spikes in late spring. Creates a round bushy 3 to 4 foot tall planting (after 3 years). Attractive leaves.

Eastern Purple Coneflower, Echinacea purpurea. Excellent flower color and upright habit. Attracts American Goldfinches to eat the seeds. Maybe 3 feet tall.

Prairie Smoke, Geum triflorum. Early spring blooming plant. The attraction is the seed heads, not the flowers. The seed heads produce a wispy pinkish tuft that dances in the wind and resembles fire and smoke on a prairie (well, it kind of looks like smoke). Very short plant that goes well with Prairie Dropseed grass.

Hope this helps.

Tom