Lee's Summit

The plans show a lack of detail concerning the construction of the detention pits. Although the overall concept appears acceptable, detailed design drawings were missing. Missing items include the following: 1) a 12 inch drain pipe is shown entering the pit, without any reference to minimum slope, connection to the downspout header, pipe type, and bedding, 2) the 1 inch outlet pipe is shown without any concrete flared section at the end, which we feel is required due to the fragile nature of this small pipe, and overall longevity of the pipe where it daylights, 3) inconsistent material call-outs for the rock (i.e., the report specifies 1.5 inch to 2.5 inch clean rock, but the plan calls for 1 foot of 6 inch river rock, which does not appear to make sense), 4) a 12 inch round grate top is specified, but no other information is provided (we recommend a cast iron grate for this application), 5) plantings are specified, but no further information is supplied concerning the type of plantings, 6) 12 inch drain pipe appears to be installed near the surface, 7) the elevation view shows 12 inches (i.e., 1 foot) of topsoil, but this does not scale properly when examining the elevation view (i.e., when adding up the thickness of 1 foot of topsoil, this would force the 1 inch outlet pipe to be placed immediately beneath the topsoil, thus rendering it useless in terms of draining the clean rock within the detention pit).

It would appear the 1 inch outlet pipe will need to be placed at a much lower elevation than shown on the elevation view. This will increase the distance needed to reach a daylight condition.

A plan and profile view is required for the outlet pipe.

A plan and profile view is required for the 12 inch drain pipe.

The 12 inch drain pipe material must be specified, along with the slope.

the 1 inch outlet pipe must show the slope and daylight location.

Shouldn't the detention pit outlet pipe located on the extreme southwest lot be directed more toward the right of way?

Shouldn't the detention pit outlet pipe located on the lot immediately north of the lot previously discussed, be directed more northerly to align with the existing swale?

Sheet C.201: It was our understanding that the detention pits were going to be placed in a sump condition. It does not appear any information in the form of contours or finish elevations were provided showing how this will be accomplished.

Sheet C.201: Existing elevations were provided for the lot corners, but finish elevations are also required, even if the existing elevation will not change.

The Engineer's Estimate of Probable Construction Costs appeared low for the following unit prices: 1) detention pit and grading. The unit price of $1,200 appears extremely low based on the fact that these pits will consist of 12 inch stormwater pipe, grate, tees, rock, filter fabric, outlet pipe, plantings, and end of outlet pipe treatment.

The Master Drainage Plan was submitted in conjunction with the sanitary sewer extension plans. The Master Drainage Plan should be a separate, standalone plan. As discussed in previous phone calls, construction of the detention pits shall be performed during individual home construction, and as such, a standalone plan is required.

No detail whatsoever was provided concerning the construction of the detention pits. Dimensions were missing, materials, depth, etc.

No further review is being conducted at this time, due to the incomplete nature of these plans. Detention pits are not even called-out, nor are there any notes concerning the deferred construction during the construction of individual homes.