Lee's Summit

Sheet C2.17: The upper right hand inset detail does not make sense. The 100%clogged/zero available storage condition HGL which appears to be below the emergency spillway crest elevation callout. The clogged condition/zero available storage should be higher than the emergency spillway crest elevation, not below the crest elevation. Please evaluate and revise as appropriate, and if applicable, please update and revise the stormwater report as appropriate.

Perforated riser did not appear to be included in the routing calculatons. Why was this done? In addition, the 4.5 inch orifice is shown after the perforated riser, and thus would not be valid as shown in the stormwater report? Please evaluate and revise as appropriate.

Hyrograph 18 contained within the appendix appears to show a 100 year water surface elevation for the 100 year event as 920.88. This elevation differs from what is shown on the plans (i.e., 921.00). Please evaluate and revise as appropriate, including any revision necessary to the stormwater report and plans.

Storage shown on the same hydrograph appears to differ from what is shown on the detention basin plan Sheet C2.17. Plan Sheet C2.17 appears to show 187,600 cubic feet of storage, but the hydrograph appears to show 182,059 for the 100 year event. Please review and revise as appropriate.

Please title Sheet C2.17 as "BMP and Detention Basin Plan". This will enable our GIS technicians to enter the information to our GIS system.

Sheet C2.17: The detail view of the outlet structure does not make sense in regard to the 2.2 foot weir shown in the outlet structure. Recommend an additional section view to show the dimensions of this weir and where it is located in relation to all other features within the outlet structure.

Perforated riser is shown with attachment points, but no specific details are provided. Please provide specific details for support of the perforated riser to ensure this feature is adequately supported. Please revise as appropriate.

It does not appear any stormwater will enter the top of the box based on the discrepancies listed above. Please evaluate and revise as appropriate. No further review of the detention basin was conducted based on the discrepancies listed above.

The "Hydraulic Report" Feb. 16, 2024 (hereinafter referred to as the stormwater study) did not appear to show a logical methodology for waiving stormwater detention. For instance, the report starts by the statement "the purpose of this report is to demonstrate compliance with the City of Lee's Summit storm water requirements." It was my understanding the purpose of the report is to demonstrate a waiver to the peak attenuation of stormwater. Since you are showing only extended detention for the 90% mean annual event, I am assuming this is the case.

Table 7 of the stormwater study appears to show peak attenuation of stormwater for the 2, 10, and 100 year event will not create an adverse situation downstream. Therefore, it appears a detention basin meeting the Comprehensive Control Strategy shall be required, and no waiver necessary. Please revise the report as appropriate, and please revise the plans for the detention basin to include peak attenuation for the 2, 10, and 100 year events.

As discussed in the above comment, please revise the design for the detention basin to include peak attenuation for the 2, 10, and 100 year events based on the Comprehensive Control Strategy.

In the "Hydraulic Report" dated Nov. 28, 2023 (hereinafter referred to as "the stormwater report"), Page 1 in the introduction states that a detention basin will be constructed, and Phase III will include Wilshire Hills Phase III and future projects. Please clean this up, as it doesn't appear to make sense. It is our understanding this stormwater report addresses Wilshire Hills Phase III, and future improvements. However, Wilshire Hills Phase III is one (1) project, but does not include future projects. Please clarify.

Page 2 of the the stormwater report states "The City of Lee's Summit has requested for detention to not be designed for the site". This is not the case. During our phone conversation, I requested that you look into how detention might lead to worsening of flooding issues downstream, as well as timing of the peaks associated with this watershed, and that if detention using the Comprehensive Control Strategy showed adverse impact to the downstream system, detention to decrease the peaks might be waived if supported by evidence. Any conclusions, recommendations, or findings shall be the responsibility of the Engineer-of-Record, not the City of Lee's Summit. Please revise.

The stormwater report is missing key elements within the text of the report, including the following: 1) analysis of the downstream peak flows as a function of time if Comprehensive Control Strategy is utilized, 2) where the downstream analysis was conducted, 3) assumptions made for the analysis, 4) discussion of upstream detention basins, and 5) other factors related to watershed analysis. Please provide a comprehensive document that discusses all aspects of the watershed.

Exhibit C2.21 and C2.22 in the stormwater report do not show sufficient detail. For instance, no road references are shown, nor existing detention basins such as the large one between Jones Industrial and Strother Rd., or the large basin south of Jones Industrial Dr., or the underground detention basin at Wilshire Hills Phase 1 to the north, or the one at the corner of Meadowview Dr. and Akin Blvd. Airport is not shown, nor the downstream receiving floodplain to the north of this development. It is difficult to determine whether valid assumptions were made without this information shown on the exhibits. Please revise these exhibits as necessary.

Considerable work needs to be done to evaluate the stormwater report. As presented, the report is incomplete. Please be aware that while appendices are required for a complete report, it is not the City's job to review these appendices to support one conclusion over the other. A thorough analysis shall be required within the text of the report, and this analyis shall be based on the findings of the study. No further review was conducted.

Please see comments related to the plat. Since the plat cannot be approved as shown in the non-contiguous manner, revisions shall be needed on the plans. Please revise as appropriate on the engineering plans.

Please see previous comment letter. The skimmer design was shown, but I could not find the sizing information for the skimmer. Please provide the sizing for the skimmer.

Please see comment #8 in previous applicant letter. Instead of an 8 inch orifice, a smaller orifce is shown. However, there does not appear to be any method shown to prevent clogging on the 4.55 inch orifice. There are various methods that have been used to prevent clogging, and this shall be required. Please be aware a simple screen has been proven ineffective since it is prone to clogging and frequent cleaning by the owner. A more robust method is needed than a simple screen across the small orifice. Please evaluate and revise as appropriate.

Sheet C2.10: There are still issues with the storm lines shown toward the north side of the project. Please see GIS markup for a pictorial representation of what I had in mind. It would appear a curb inlet could be installed where the private 24 inch line on the west side of Wilshire Dr. enters public right of way, and this would denote the extent of public versus private in terms of the storm line. This will enable the corner to be cleaned-up in terms of storm lines, and will better serve the entire subdivision. Please evaluate the existing 24 inch public storm line to beneath Wilshire Dr. to ensure it has sufficient capacity, and ensure the downstream system after this point has sufficient capacity.

The stormwater report did not appear to analyze the downstream peak flows within the receiving stream after construction of the detention basin. Given the location within the watershed immediately upstream of a FEMA floodplain, and given the proximity of existing upstream detention basins, it would appear the construction of the detention basin as shown on the plans will likely increase the peak flows due to timing of the peaks and slow release of stormwater from the detention tract over an extended time period. Please address this issue within the stormwater study. It is possible that peak attenuation of the 2, 10, and 100 year events will not be necessary and could be detrimental to the downstream receiving system. If this is the case, water quality could be provided on-site or off-site without the need for peak attenuation of the 2, 10, and 100 year events. Please analyze and revise the stormwater study as appropriate.

It is difficult to determine from the plan view, but it appears the 100 year clogged condition/zero available storage within the detention basin does not meet the 20.0 feet setback requirement from the tract line. A minimum setback of 20.0 feet is required from the tract line, property line, and all buildings.

Although not shown on the plat, a stream buffer easement is required for the portion of the stream exiting the large concrete box culvert. The buffer is measured as a minimum distance from the ordinary high water mark of 100 feet (i.e., not the centerline of the stream). It appears the detention basin is shown partially within this stream buffer, which is not allowed. Please revise or see previous comments. It is possible this detention basin and tract may not be desirable for the development.

It appears PCC is being shown as an alternate for the asphaltic concrete pavement. Please specify KCMMB mix for the concrete. KCMMB mix has granite aggregate and is the only mix allowed in the City of Lee's Summit.

Please refer to comments on the Final Plat. The two (2) short easements shown extending from curb inlets along Wilshire Dr. and extending to the east should be removed. The storm lines extending from these two (2) curb inlets shall be considered private.

It does not appear the skimmer was shown with the sizing information. Please provide a site-specific design including sizing for the skimmer.

Sheet C2.17: The pond setup table included within the appendix of the stormwater report shows a flowline elevation of 911.15 for the 8 inch orifice. The plans on Sheet C2.17 show 911.50. Please reconcile.

Sheet C2.17: It does not appear any method for anti-clogging of the 8 inch orifice was shown. Please provide a method to prevent clogging of the 8 inch orifice.

Sheet C2.17: The emergency spillway crest detail shows "Design Stage=923.30". Shouldn't this read "Clogged Condition/Zero Available Storage = 923.30"? Please revise as appropriate.

Please see previous comment letter about what is expected on Sheet C2.17. We need the following added to the sheet: 1) 100 year nominal (i.e., design) storage volume.

Please be aware if KCMMB concrete option is selected, a site-specific jointing plan shall be required. The generic plan is not sufficient.

Site-specific ADA-ramp details are required at Strother Rd. intersection. This includes: 1) slope callouts, 2) elevations at corners, 3) cross-slopes, 4) width of the ADA-accessible route across the intersection, 5) and elmination of the wings on the ends of the ADA-accessible ramp. Simple grading to the edge of the ramp should be used rather than the wings shown on the ramps. Please submit a site-specific plan for the ADA-accessible ramps at Strother Rd.

The same comments above related to the ADA-accessible ramps apply to both commercial entrances on Wilshire Dr. Please provide site-specific designs for the ADA-accessible ramps at both commercial entrances. In addition, ensure the ADA-accessible route across the commercial entrances are shown with slope callouts and dimensions and elevations.

It may be better to defer the ADA-accessible ramps shown at the two (2) commercial entrances until the Final Development Plan is approved. If so, please provide notes stating "see separate Final Development Plan" or equivalent language for these ADA-accessible ramps. Please be aware the ADA-accessible routes, however, will need to be constructed across the commercial entrances along with the street improvements.

The short extension of sidewalk to the north to tie into the existing sidewalk on Wilshire Dr. should be completed along with these improvements. However, it appears from the GIS that the plans are several feet short of where the existing sidewalk is located. Please extend the sidewalk until it meets the existing sidewalk to the north, and provide notes to that effect. Otherwise, there will be a gap.

All sidewalk related to this project including ADA-accessible ramps and ADA-accessible routes should be clearly labeled with instructions regarding when they are to be constructed (i.e., during the street and stormwater project or during the Final Development Plan). This can take the form of a legend, notes, or a combination of both.

It appears there is a private 24 inch storm line towards the north portion of the project that is shown beneath the new road. This should be addressed by eliminating this private storm line and re-configuring the geometry of the public storm system in the northern portion of the project. Although private storm lines are acceptable, we cannot approve of private storm lines beneath public streets. Please evaluate and revise as appropriate.

Please review Section 5600 of the Design and Construction Manual related to detention basin design. A minimum freeboard of 1.0 feet is required from the 100 year clogged condition/zero available storage and the top of dam. It appears this criteria is not met.

Detention pond setup table was not included within the appendix of the stormwater report. Please include within the appendix of the stormwater study.

Please review Section 5600 of the Design and Construction Manual related to emergency spillway freeboard and the 100 year nominal water surface elevation. A minimum of 0.5 feet from the nominal (i.e., the design) 100 year water surface elevation and the emergency spillway is required. It does not appear this condition was met. Please revise as appropriate.

Title of the plans is Phas III, but this appears to be the 4th Plat of Wilshire Hills. To avoid confusion, please rename the plans as "Street and Stormwater for Wilshire Hills 4th Plat" or equivalent language.

Why are there two (2) cover sheets for this project?

Asphaltic concrete section shown in the plans is incorrect and does not follow the Design and Construction Manual. Please review the Design and Construction Manual, and ensure the subgrade either includes geogrid, or chemically-stabilized subgrade. Please review and revise as appropriate.

A separate sheet should be developed for the detention basin/retention basin showing the following information: 1. Top of dam elevation. 2. Emergency spillway elevation. 3. All weir and orifice elevations that are part of the outlet structure. 4. 100 year nominal (i.e., design) storage volume. 5. Bottom of basin elevation. 6. 100 year nominal (i.e., design) water surface elevation (WSE). 8. 100 year clogged/zero available storage WSE. 9. Graphical limits of the 100 year clogged/zero available storage WSE (i.e., shown on the plan view with callouts), along with dimensional callouts from property lines and buildings to ensure a minimum 20 foot setback. 10. Typical section view of the outlet works and dam, along with elevation callouts for the 100 year nominal and 100 year clogged/zero available storage to ensure there is a minimum 0.5 feet freeboard between the nominal condition and the crest of the emergency spillway, and a minimum 1.0 feet from the clogged condition/zero available storage and the top of dam. 11. Location and callouts showing the emergency spillway, and a clear path that is not directed towards buildings or other other vulnerable features.

The reason for the above is an as-built Record Drawing of the detention basin and outlet works shall be required prior to occupancy. The single sheet shall make the process of review easier when occupancy permits are being sought.

Sidewalk was missing from the plans. In addition, site-specific ADA-accessible ramps and ADA-accessible routes across intersections were also missing. No further review can be conducted until these are shown on the plans.

The pavement width as measured from back of curb to back of curb does not appear correct. Commercial roads shall be 36 feet back of curb to back of curb. Residential local, which does not appear relevant to this development, shall be 28 feet as measured from back of curb to back of curb. Please revise as appropriate.

Type M curb inlets are called-out, but the City of Lee's Summit does not have any such detail. Please clarify that the City of Lee's Summit standard curb inlet shall be used by referencing the appropriate standard drawing.

Hydraulic grade line for the design storm shall be shown on all storm line profiles. Typical practice in City of Lee's Summit is to show the 10 year at or below the crown of pipe, with the 100 year contained within the pipe and no less than 6 inches from any throat opening. Please update on the profile view.

Pipe calculations should be shown within the plans in the form of a table(s) for each storm event. The stormwater report presents these, but in addition, the City of Lee's Summit requires these to be placed in the plans. Please update as appropriate.

The 60 inch pipe exiting the detention basin shall be designated private. As shown, it is public. Please revise.

The 60 inch pipe exiting the detention basin is shown with an excessive slope which will lead to supercritical flow conditions and excess erosive ability. Recommend lessening the slope. Please evaluate and revise as appropriate.

The outfall structure of the detention basin is shown as public. This shall be private. The City of Lee's Summit does not maintain public stormwater detention basins, outlet works, or discharge pipes. Please revise as appropriate.

Sheet C2.12 shows an "existing detention basin". Where is this existing detention basin?

Rip rap calculations were not provided, nor were there any dimensions, thickness, geofabric, rip rap sizing, etc. shown for the rip rap. Please show this information on all sheets related to rip rap.

A trenching and backfill detail was missing from the plans. Please ensure the most up-to-date detail is provided with 12 inches aggregate over the top of pipe which was adopted in Jul. 2020. The City does not have a standard detail for trenching and backfill, so it will need to be a customized detail.

Plans reference "The City of Locust Grove" throughout the plan set. Please revise. Many of the references relate to concrete, and the City of Lee's Summit requires KCMMB mix for all stormwater structures, pavement, curb and gutter, etc. Please review and revise as appropriate.

TMIs are called-out, but the City does not recognize a "TMI". What is a TMI? Is this a curb inlet?

Has the plat been reviewed in terms of right of way width for street classification? A minimum 60 feet right of way is required for commercial streets with a 36 foot back of curb to back of curb street width. Please review and revise the plat and the plans as appropriate.

Informational Comment: It is probable that additional comments shall be forthcoming on future submittals due to the incomplete nature of the plans.

Sidewalk will be required with these improvements. Sidewalk will need to extend past this plat and connect to the existing sidewalk on Wilshire Drive.