Lee's Summit

Please provide a revised Master Drainage Plan for the lots affected by this revision. Since the diversion berm is designed to manage the 100 year event with a minimum of 2.0 feet of freeboard, it will no longer be necessary to assign an MBOE that is 2.0 feet higher than the 100 year WSE behind the diversion berm. In fact, elimination of MBOEs might be considered if in the opinion of the engineer they are no longer necessary. It is recommended that the lot adjacent to the detention basin, however, be assigned an MBOE based on the clogged condition/zero available storage elevation within the basin for the 100 year event.

Slope of swale is less than 2.0% in the vicinity of sta 6+50. This area also appears to be a very critical portion of the swale. Upstream slope appears

End of swale abruptly ends near the emergency spillway for the detentioin basin with no further existing contours or proposed contours presented. Additional extension of the swale is needed. It should be extended far enough to ensure the flows carried by the swale do not jeopardize the intergrity of the dam.

What is the plan for the existing field inlets in the rear yards of the east lots? Are the throats going to be sealed with concrete and rebar?

What is the plan for the existing field inlets in terms of adjustment to grade? Are the field inlet tops going to remain above grade?

Cross-sections are warranted for the diversion berm. A typical section is not sufficient. Recommend one (1) cross-section at 50 foot intervals or less. HGL for the 100 year event should be shown for each cross-section. Finally, the area in the northeast corner of Lot 12 does not appear to show a berm. Ensure there is a cross-section in this location showing the berm.

Sheet 33: What is the purpose of the swale detail shown in the upper right? Shouldn't it be removed?

Plan view contours show diversion berm top that is not flat. Diversion berm tops should be flat. Recommend showing flat top diversion berm throughout, with a top width to be determined by engineer. Recommend a minimum 3 feet width to ensure long-term integrity of the berm.

General Comment: Wouldn't it be simpler to install an underground pipe system rather than a diversion berm to manage the stormwater? At least in the area downsream of where the slope is not sufficient for a swale?

MBOE tables for the lots along the entire length of the diversion berm do not appear realistic for home construction. For instance, if using the MBOE table for Lot 8, the driveway is going to be 25%+/-, and perhaps even higher when placing other openings such as egress wells, daylight basement windows, etc. This appears to be the case for all lots abutting the diversion berm. Recommend a re-evaluation of all MBOEs along the diversion berm.

Recommend re-evaluation and re-design of the diversion berm. If 2.0 feet of freeboard can be maintained between the 100 year WSE from off-site drainage area and the top of the diversion berm in all instances along the diversion berm, no MBOEs are needed for these lots unless adjacent to or affected by the 100% clogged condition zero available storage elevation within the north detention basin (lots 30 and 12?), or surcharging out of inlets during the 100 year event. Plot plans may be reviewed according to “good lot grading practice” in these instances, unless adjacent to the north detention basin or affected by surcharging as described above. A redundant emergency overflow swale would not be specifically required if the 100 year HGL in the 60 inch pipe does not surcharge out of the top of field inlets, unless desired by the engineer and developer. See comment #9 below for specific citation concerning emergency overflow route.

Recent field visit on Apr. 12, 2021 showed field inlet weirs in the rear of the lots to the east of Corbin Dr. were installed higher than the emergency overflow swale by approximately 1.75 feet. What is the purpose of these weirs if stormwater cannot enter the structure?

There were 14 separate meassurements on the as-builts obtained along the 730 foot long diversion berm. All were designed with a specific shape (i.e., trapezoidal with a 3 foot flat bottom). None of the as-built contours show a flat bottom channel, but rather, a v-bottom swale. Visual inspection confirmed the v-bottom swale.

Of the 14 separate measurements along the diversion berm, 8 of them showed low spots that were less than the 2.0 feet design height. The as-built has been marked-up and is attached showing their locations.

Recommend additional elevation shots along this critical drainage structure (i.e., the diversion berm draining a large off-site area). As shown, it appears they were collected at 50 foot intervals, which appears excessive for a critical structure such as a diversion berm. Without a functioning diversion berm with minimum elevations as designed, the potential for overtopping is high along with yard flooding or structure flooding concerns.

None of the diversion berm tops were constructed per plan. A 3 foot flat spot (i.e. with 2% slope from the c/l) on top of the berm was shown on the construction drawings, but a rounded top was provided as per the as-builts. Recent field visit confirmed the rounded top. This will affect the long-term integrity of the diversion berm.

No elevation shots were provided on the extreme north portion of the diversion berm after it discharges to the receiving area beyond the last field inlet O1-B. Stormwater from the drainage area upstream of the diversion berm was specifically designed by the engineer to bypass the north detention basin, and the as-builts shall provide evidence this is occurring as planned. Recent site visit suggested the diversion berm was too low beyond O1-B, which would introduce stormwater into the basin which was not planned by the engineer.

It may be beneficial to re-evaluate your emergency overflow swale along the 60 inch pipe in terms of applicability to Section 5601.5.A.(3)(a). A spot check of your calculations of 100 year flow within the 60 inch pipe would suggest a misinterpretation on the part of the engineer concerning the requirements contained therein. The following excerpt is provided for reference: 5601.5.A.3 Overflow Systems: Overflow systems shall: a. Be designed to route downstream any amount of the 1% storm exceeding the in-system design capacity specified in Section 5601.8.

Recommend resubmittal of the Master Drainage Plan after a re-evaluation discussed in comments above.

The original as-built dated Feb. 19, 2021 was missing the backside of the north detention basin dam elevations and contours. The most recent as-built included this information. The backside of the dam was built steeper than the design slope of 3:1. Slopes from 2.2:1 in the most critical location (i.e., the highest point of the dam in terms of relief between the pre-existing ground elevation in the northeast corner, extending all the way around this area), to 2.7:1 over the other areas along the east backside of the north detention basin are shown. Re-grading would appear warranted to eliminate dam failure concerns, along with a new as-built following completion of grading.

The City would consider your recommendation to raise the north basin outlet structure top weir elevation to achieve compliance with the 2, 10 and 100 year storm events (i.e., within 3% of the allowable release rate for the 2 year event as stated in the “As-Builts Storm Report” dated Apr. 6, 2021), as well as re-grading of the emergency spillway to achieve the required 0.5 feet of freeboard between the nominal 100 year WSE and the crest of the emergency spillway. However, this will require an analysis of the upstream storm line calculation table on Sheet 20 to account for the increased HGL within the detention basin. Two (2) storm lines near the discharge point are flowing under outlet control for the majority of storm events, and changes to the WSE within the basin will have a significant effect on the HGL of the pipe. The 10 year event should be contained at or below the crown of the pipe(s) as shown on your approved design (unless waived by the City Engineer), with an overflow route established for the excess above and beyond the 10 year event that might surcharge out of the top of inlets up to and including the 100 year event. Please see Section 5601.5.A.(3)(a) of the KCAPWA manual (adopted by reference by City of Lee’s Summit) for the specific reference.

“As-Built Storm Report” dated Apr. 6, 2021 was missing the following items: 1) quantifiable analysis of the impacts to the designed water quality storage and release due to unapproved changes to the outlet structure during construction, and 2) quantifiable analysis of the freeboard requirements between the 100 year WSE (clogged/zero available storage) and the top of the dam (low point of top of dam) for the proposed condition with the 7 inch riser installed and spillway re-grading.

Recommend a meeting with engineer, contractor, and developer to discuss issues related to all of the above comments. Some of the comments above relate to construction issues (i.e., grading not completed per the plan), while others relate to design issues discussed in the above comments.

Please see the previous comment letter. The "Storm Water Report" dated Oct. 2020 appears to be a collection of addendums that are not discussed within the body of the report. As requested, the stormwater report must be a standalone document, and at a minimum if using addendums within the appendix, must discuss the relevance of these addendums within the text of the report. As presented, there is no context to these addendums, but merely the inclusion of them within the appendix. The final report must be a standalone document, and must follow a logical sequence. Please revise the report as appropriate.

Only one (1) pond setup sheet (i.e., summary of the orifice sizing, weir sizing, location, etc.) was shown for the south detention basins. The north detention basin pond setup sheet was missing.

Please see previous comment letter. Sheet 15 was apparently changed without any City approval? Was this change related to a field change?

The "Final Storm Report" dated July 21, 2020 (hereinafter referred to as "the stormwater report") was not a standalone report. Given the various revisions that have occurred with this project, a complete standalone report is required, along with all calculations for the south detention basins. Addendums will not suffice in this instance, due to the level of revisions submitted for this project.

The stormwater report discusses a 5 by 15 foot cast in place box. Using normal naming nomenclature, shouldn't this call-out the inside dimensions of the box? The outside dimension appear to be 5 by 15 feet, but shouldn't the interior dimensions be called-out?

Page 10 of 26 within the appendix for the stormwater report appears to show only one (1) weir structure (i.e., the riser structure) on the pondpack setup page. Is this correct? Shouldn't there be two (2) weirs included?

These plans have been revised three (3) times since the original approval. In the interest of clarity, a complete set of plans must be submitted for this project. We will not accept revision sheets, given the number of revisions since the original approval.

Sheet 43: The following items were missing from the "Energy Dissipator Detail": 1) dimensions of the long axis of each component of the Contra Costa energy dissipator, to be shown on the plan view, 2) dimensions to each corner of the above design element based on the 15 degree call-out, shown on the plan view, 3) the location of the A-A section line to coincide with the section view shown below the plan view, 4) slope of the energy dissipator in the long axis, to be shown on the section view, 5) a section view along the front end of the energy dissipator, along with appropriate notation of the section line shown on the plan view.

The frontal view discussed above must also show the slopes across the structure, including any changes in grade at the edges, etc. Sufficient dimensions must be provided at all changes in slope, etc.

The energy dissipator elements do not include any material call-outs, including any reinforcing steel, to be used for the project.

The energy dissipator elements do not appear to be sufficiently anchored. Six inches of embedment within rip rap would indicate a predicted failure during the first rain event. Why are these energy dissipator elements not sufficiently anchored into the earth, below the frost line? Shouldn't these elements be tied-together with an underslab beneath the frost line, with all elements tied to the underslab?

The Engineer's Estimate appeared to be missing the Contra Costa energy dissipator.

There is still concern about the size and quantity of the orifices used to comply with the 40 hour extended detention requirement on the north detention basin. If it is demonstrated after construction, that drawdown of the detention basin is not occurring within two (2) days after rain events, modifications and redesign shall be required prior to issuance of a Certificate of Substantial Completion and/or Certificate of Final Acceptance.

Within the plans or report, perhaps on the detail sheet showing the north detention basin, please call-out the "effective height" of the dam. Please refer to TR-60 for a definition in relation to the centerline of the dam, the existing grade elevation, auxilliary spillway, etc. It appears the effective height is less than 10 feet, but a statement should be made either on the plans, or within the body of the stormwater report.

As discussed in the previous comment letter, additional energy dissipation measures are required at the discharge end at the north detention basin. For the minimal cost associated with this potential liability issue, the City continues to maintain the necessity of this requirement. It has been our experience on past projects, with drainage areas significantly lower than this project, that the City's Design and Construction Manual, and MoDOT standard designs, are not adequate to protect adjacent property, when discharging stormwater directly onto adjacent property. In general, a design is required which creates a hydraulic jump fully-contained within the off-site drainage easement, up to and including the 100 year event.

The following items were missing from the Engineer's Estimate of Probable Construction Costs dated Apr. 1, 2019: 1) paving as per the detail shown on Sheet 41, upper detail for the commercial local street with upgraded pavement thickness, and upgraded aggregate thickness, 2) stilling basin for north detention basin (see comments concerning this required feature), 3) erosion and sediment control devices, and measures, 4) final restoration, including seeding, fertilizer, mulch, and topsoil.

The Final Drainage Report - Phase 1 dated Mar. 29, 2019 (hereinafter referred to the drainage report) contained a discrepancy in the quoted flowline elevation of the 4x21 inch orifices in the north detention basin elevation when compared to the plans. The elevation called-out on the plans is 970.45 versus 970.30 in the report.

Shouldn't there be a setup summary provided by PondPack which shows the pond setup, such as the orifices used, the elevations of the orifices used, weirs used, weir elevations, timestep or time interval used, hydrograph used, the outlet pipe used including the diameter, length, etc.? This appears to be missing from the appendix. The only information provided in the appendices were summaries of results, with no corresponding assumptions provided.

The north detention basin will be providing 40 hour extended detention. Please ensure that the 2-8 inch diameter orifices shown at the bottom of the structure were eliminated from the model run (i.e., removed from the routing procedure) during the routing calculations. According to the plans, these orifices are to be sealed-off after the skimmer is disconnected, and with such a large volume of stormwater, it appears this orifice was included in the routing calculations? We are concerned that 4x2 inch openings and 8x1 inch openings will be insufficient to act as a 40 hour extended detention basin for such a large volume of stormwater (i.e., the basin would appear to act more like a week long extended basin, which is not the intent of the 40 hour extended detention requirement). The basin should be drained within 40 hours to ensure there is adequate storage volume for subsequent storm events.

Within the body of the drainage report, there is a very brief discussion of the orifices included in the outlet structure serving the north detention basin. However, there is no discussion of the weir at the top. There is only a statement that "the top of the risers were set at an elevation of 973.00". Was this included as part of the routing calculations in the form of a circular weir that also acts as an orifice? Is the 48 inch outlet pipe serving each outlet structure going to be sufficient to manage the 100 year peak flows? If so, where is this shown in the PondPack setup? There are concerns that these 48 inch RCP outlet pipes will be insufficient to manage the 100 year flows, which is a requirement of the Design and Construction Manual.

The drainage report briefly discusses the "Post-Development 100 year Spillway" in Section 8. Do you mean the emergency spillway? This section also states that 1 foot of freeboard is provided. What is the clogged condition/zero available storage 100 year water surface elevation, and where in the appendix is this found? We found a reference in the appendix under "PondPack Spillway Output", and are assuming this is the emergency spillway. If so, please make appropriate changes to the report. Finally, the emergency spillway does not appear to comply with TR-60. TR-60 requires that emergency spillways be located away from the dam. As designed, the emergency spillway IS the dam. TR-60 allows for the following: 1) dams with drainage areas less than 10 square miles may be served by an emergency spillway (i.e., specified as "auxiliary spillway" in TR-60) with a closed conduit, with a cross-sectional area of 20 square feet or more, with an inlet that "will not clog", an "elbow designed to facilitate the passage of trash and large enough to pass the routed freeboard hydrograph peak discharge without overtopping the dam". This design alternative appears to be the only way to provide a an emergency spillway for this basin. It will require a complete re-design of the outlet structures for the north detention basin.

The drainage report discusses rip rap design for the north detention basin outlet. Additional measures should be designed and constructed for this discharge point. A stilling basin, or other structure to create a hydraulic jump at the discharge point is warranted given the sizing, and numerous field-tested designs are available from the Federal Highway Administration. This issue has been discussed with management, including the Department Director, who is seriously concerned about the potential for adverse impact to the adjacent property owner(s), as well as impact to the stream.

Section 11 of the drainage report discusses "various openings" in the outlet structure serving detention pond 3, with no sizing, elevations, or references within the appendix showing how this was set up in PondPack (see previous comments about the lack of the PondPack set up summaries that are normally supplied). In addition, this section states that the detention basins were "designed per APWA 5600 standards". However, according to Table 6.5 on Page 5 of the drainage report, it appears the allowables at this point will be exceeded by a high margin. According to Table 6.5, the allowable at EX1 is 15, 43, and 68 cfs for the 2, 10, and 100 year events respectively. Table 7.1 on the same page appears to show the post-development discharge at P1 to be 29, 59, and 85 cfs respectively for the 2, 10, and 100 year events. All of these are significantly higher than the allowables presented on Table 6.5.

Wet retention basins are subject to different design standards. In particular, the ponds are too shallow. Although the Design and Construction Manual states that four (4) feet is the minimum depth, the manual also requires a sedimentation allowance. It appears no allowance was given for sedimentation.

The drainage report discusses a waiver to the Design and Construction Manual for the freeboard requirement on the southern detention basin. What is the rationale for this waiver request? Are these basins mainly "cut" rather than a "dam" being constructed? It appears this is the case, and as such, no waiver would be required since there is no "dam". Please discuss within the report, and provide justification in the body of the report.

South Wet Retention Basins: Please discuss why emergency drawdown (i.e., drain, etc.) was omitted from the design. Please see above comment concerning "cut", and discuss why this may or may not be necessary based on your opinion.

Sheet 43 of 50: The south detention release structure section view should be revised to show the normal pool elevation upstream of the structure. As shown, it appears to be at ground level, not the normal pool elevation.

Sheet 43 of 50: How will 6x12 inch openings set at the normal pool elevation act to provide 40 hour extended detention? It would appear this will not provide 40 hour extended detention for the 1.37 inch event.

Sheet 43 of 50: Manholes are specified for the riser structures, but no details are provided. Where are the steel reinforcement details? Finally, the concrete base for the south outlet structure and the north outlet structure was missing the details for construction (e.g., similar to the details provided for the temporary PVC riser structure).

Will the outlet structures be in a region of pressure flow for the 100 year event? If so, an anti-vortex device must be installed as per TR-60.

The last "response to comments" letter (i.e., response #52) received on Mar. 29, 2019 states that "...water line plans have been resubmitted". We have not received the resubmittal for the water line plans. Also, we have not received a resubmittal on the sanitary sewer plans, which were apparently altered in response to the re-design?

Why is silt fence being used in the middle of the sedimentation basin? Wouldn’t this prevent the basin from doing its job? It would also appear to create adverse impacts to adjacent property owners, by diverting sediment-laden stormwater to adjacent properties. The note states that it will also be used to "stabilize the slope". If slope stabilization is desired or necessary, then provide a different mechanism for this to occur without preventing sediment-laden stormwater from the entering the basin.

In the pre-clearing phase of erosion and sediment control, please add silt fencing along the south side, south of where the 3 drainage basins are going to be located. This needs to remain in-place and be maintained until final restoration.

Consistency should be maintained in the contour intervals shown for the sedimentation basin. Currently, there are 1’ contours in some areas and 2’ in others. The detention basin detail would appear to need 1 foot contours throughout. Also, the 978 contour along the berm on the east side of the basin stops, and branches off in two separate directions, which does not appear valid. Should the 978 contour continue around the pond and tie in on the NW side of the pond? Please clarify and adjust, because as shown, it does not appear to make sense.

It is impossible to read the existing contour elevation call-outs and slope percentages on sheets 36-39. Adjust line weights throughout the plan set to make the elevation call-outs legible.

Revise all the end of road signage from Barricades w/Road Closed (a temporary traffic control device) to a typical end of road treatment using 4 evenly spaced object markers.

End of road signage is needed at all stubs, and at the end of all road construction.

A speed limit sign was missing along Cobey Creek Dr., between M-150 and Gillette St.

At station 10+30 on Cobey Creek Dr., it appears the sag k value is too low. The minimum k value for a commercial local street is 30.

The SWPPP is incomplete. Please update so that it is in alignment with the plan set.

The plans show only one phase of land disturbance. Is this correct? Should it be separated into multiple phases? Where is the final restoration plan?

The legend is missing silt fence on sheet 37. There are line types that are identical on sheet 38 (silt line & diversion berm). Please clean up each legend and show a difference in linetypes.

Please provide KCAPWA standard details for all erosion and sediment control devices and measures used on this project.

The "Final Drainage Report - Phase 1" dated Mar. 7, 2019 (hereinafter referred to as the drainage study) is lacking a presentation within the discussion section, as well as the appendices showing the details concerning the orifice/weir configuration of the outlet structure(s). These details should specifiy the diameter of any orifices, and length of any weirs used in the outlet structure. As discussed in the report, only the orifices for the 40 hour extended detention are discussed.

The MARC manual requires either a perforated riser or v-notch weir in the case where the calculated orifice diameter is less than 4 inches. It appears that four (4) x 2 inch orifices are proposed, which does not comply with MARC manual requirements.

Where in the drainage study are the MARC manual worksheets for calculation of the method to be used for 40 hour extended detention?

Discussion within the drainage report shouuld match what is shown in the appendices concerning identification of each detention basin. There are references in the appendices to "detention pond", "pond 1", "pond 2", and "pond 3". Plan sheet 3 of 49 is vague, since it only refers to "south detention basins" (although it does refer to Sheet 31 later in the plan set). Please be specific in the discussion section concerning these features.

Is 40 hour extended detention within the "south detention basins" being ignored? If so, why? This would appear to contradict page 5 of the drainage study where it states "...the detention facility will release the water quality event over a 40 hour period".

Page 27 of the appendix presents the results of the "detention pond" (we are assuming the north detention basin). Please provide specific labels on this graph showing which detention basin this graph represents. Finally, it does not appear that 40 hour extended detention is being achieved as shown on the elevation versus time graph. Isn't this more like 34 hours?

The same comment above would apply to all graphs and tables shown in the appendix. Please clarify which table or graph corresponds to each basin (i.e., north detention basin, detention basin 1, etc.).

Sheet 39 and 42 appear to be duplicate sheets.

Sheet 39 (and 42): This sheet is insufficient for purposes of construction and inspection. While we feel this is a good first step, typical installations of this type utilize the manhole as a "protection element" (i.e., to protect an interior riser structure with weirs and orifices) from damage due to vandalism. We have typically seen weir slots provided in the manhole to allow entry of stormwater, but the actual control riser assembly being installed within the mahole.

Sheet 39 (and 42): Placement of filter fabric across the orifices as shown is not an adequate anti-clogging measure. If constructed in this manner, it is likely the basins will clog during the first significant storm event. There are numerous methods that are available for anti-clogging, but this is not one of them. Even if the filter fabric were never to experience clogging by fines and silts, the placement of a semi-permeable barrier across the orifices will have a significant impact on the routing calculations.

In accordance with TR-60, RCP should be specified for the outlet pipe past the riser. As shown, HDPE is specified.

Additional Comments Concerning the Outlet Structure: Not only a section view is needed, but also a plan view. Any grated tops should also include details concerning the grate type. All details necessary for construction and inspection are required.

Sheet 40 of 49: It is our understanding that Cobey Creek Dr. from M-150 to Gillette is classified as a "Commercial Local"? Please add this to the typical section view for "Commercial Local".

Sheet 46 of 49: Signage Plan is missing "end of road" locations and details for both ends of Gillette St., Jud Rd., Cobey Creek Ln, Corbin Dr., and Cobey Creek Dr. In addition, Cobey Creek Ln., and Jud Rd. were not labeled.

General Comment Concerning Sidewalk Construction: The plans are vague in terms of what sidewalks will be constructed during Phase 1. We could not identify any notation within the plans showing the locations where sidewalks and ADA-accessible ramps will be constructed. As shown, it appears all of the sidewalks will be constructed with the development. This is acceptable, but not necessarily required.

Sidewalks must be constructed along all platted tracts. It appears sidewalk construction must be included within Phase 1 along the north end of the future Corbin Dr., along Tract H. The same would apply to sidewalk along Tract D, along the future extension of Cobey Creek Dr.

It appears the emergency spillway for the north detention basin is approximately 550 feet in length. This appears excessive. The drainage study also discusses lining this emergency spillway with rip rap, which does not appear to be shown on the plans. The emergency spillway also appears to be shown extending along the eastern side of the north detention basin, and extending around the north side of the detention basin. Is this appropriate for an emergency spillway design? Will a large emergency spillway in terms of length jeopardize the integrity of the dam? It would appear this emergency spillway length represents around 40% of the perimeter of the dam.

Sheet 30 of 49: The 18 inch HDPE discharge pipe at the end of storm line 2 is shown with zero slope. How is this going to work?

Sheet 30 of 49: Rip rap is specified at the end of storm line 2 (i.e., the discharge point for the north detention basin). However, it is not called-out correctly in terms of sizing, filter fabric, approximate cubic yards (i.e., it specifies D50 size rip rap, width, length and depth). Please specify the D50 sizing so there is no confusion, interpretation, or additional information needed during construction. In general, the following notation is the minimum amount of information required for rip rap placement: "Install xx.x cubic yards (xxW by xx L by xxT) stone rip rap using a minimum xx inch stone. Place filter fabric prior to installation of rip rap."

Sheet 30 of 49: Rip rap notes, in accordance with the above comments, were missing for the other two (2) entry points on the south end of the detention basin.

Sheet 13 of 49: Our calculations show the rip rap at the north end of storm line 5 would be better suited with a 16 ft long, by 8 foot wide, by 1.5 foot thick layer of 12 inch rip rap over filter fabric. This would correspond to approximately 7 cubic yards. Please re-check your figures, and provide the minimum notation concerning the placement of this rip rap.

Sheet 1: The index of sheets appears to show Sheet 39 as corresponding to a "sedimentation pond detail". This sheet is actually a redundant detention basin outlet structure detail sheet.

Sheet 2 of 49: Sidewalks should be extended along all platted tracts (i.e., Tract D and Tract H) to the end of the future road extensions. Please see previous comments concerning this issue.

Sheet 2 of 49: The note at the bottom should be updated to reflect the curb and gutter type for Cobey Ln.

Sheet 2 of 49: Please consider naming each detention basin in accordance to the naming convention used in the revised drainage study. Please see previous comments related to the requirement that a revised drainage study be submitted.

Sheet 3 of 49: Please add a street name label for Jud Rd.

Sheet 4 of 49: Aspen Dr. is called-out on one of the notes. Please update since it does not appear Aspen Dr. is part of these plans.

Sheet 4 of 49: Do the MoDOT plans include the ADA-accessible ramp details at the intersection of M-150 and Cobey Creek Dr.? If not, these should be included in the MoDOT plans.

Sheet 5 of 49: Sidewalk should be shown extending along Tract D along the future extension of Cobey Creek Dr. It must be extended the entire length of Tract D.

Sheet 5 of 49: The street profile view of David Rd. does not appear to include the ADA-accessible route across the intersection. As shown, there is a constant 2.8% slope called-out, with no provision for the 1.5% cross-slope, 5 feet wide across the stop-controlled intersection.

Sheet 6 of 49: The ADA-accessible ramp on the northwest corner of Gillette St. is still shown without a receiver ramp (i.e., it is shown as a uni-directional ramp). This should be shown similar to the ADA-accessible ramp on the southwest side of Gillette St. to function as a receiver for pedestrian traffic.

Sheet 6 of 49: It does not appear the street profile view for Gillette St. shows the ADA-accessible route across Gillette St. near station 16+00. It appears 2.0% is called-out, but 1.5% is the maximum design cross-slope.

Sheet 7 of 49: Sidewalk must be constructed along Tract H, along the future extension of Corbin Dr.

Sheet 8 of 49: The ADA-accessible route across Carter Rd. does not appear to be shown on the profile view. It appears it shows 2.0% cross-slope, but the maximum design cross-slope for ADA-accessbile routes across stop-controlled intersections is 1.5%.

Sheet 8 of 49: Ensure sufficient notes are provided to ensure the sidewalk is constructed along Tract E with the other subdivision improvements. As shown on the plans, ALL sidewalks must be constructed (i.e., we could find no notes specifying otherwise). However, this is not necessarily required. Please see previous comments concerning this issue. Only ADA-accessible ramps, and sidewalks along platted common areas must be constructed with the other subdivision improvements. If you desire to construct all the sidewalks, this is also acceptable, but not required.

Sheet 9 of 49: The street profile for Cobey Ln. does not appear to show the ADA-accessible route across the stop-controlled intersection. It appears to show 2.0% cross-slope at that location.

Stormwater General Comment: Was the water surface elevation within the detention basin for the 10 year event taken into account for the calculation of the hydraulic grade line?

Sheet 21 of 49: If only installing the ADA-accessible ramps, where is the start and end of construction? The details are vague.

Sheet 21 of 49: Dimension call-outs are needed for: 1) the distance between the end of the tactile warning and the back of curb, 2) width of the ADA-accessible route across the intersection.

Sheet 21 of 49: a 2% maximum running slope is shown on typical section A-A. What does this represent? Within right of way, running slope is not limited to 2%.

Sheet 21 of 49: The northwest corner ramp is not shown with a receiver ramp to accept pedestrian traffic from the southwest corner. Why was this omitted?

Sheet 22, 23, 24, 25, 26, 27, 28, and 29 of 42: The same comments concerning dimensioning and Section A-A should be addressed on these sheets.

Sheet 30 of 49: A note shows a 500 foot spillway. We measured a distance which is considerably longer than 500 feet. The bigger question, however, is whether this is a good idea (i.e., to install an emergency spillway which covers a significant percentage of the available perimeter of the dam).

Sheet 33 of 49: The MBOE table should be relabeled as "Lot Corner Elevations and MBOEs", or equivalent language. These tables present more information than MBOEs, and as such, should be titled differently.

Sheet 34 of 49: The same comment above pertains to this sheet.

Sheet 33 and 34 of 49: The note concerning the construction of swales needs revision. All swales shown on the Master Drainage Plan should be constructed during Phase 1. The City will not allow for piecemeal construction of swales during the plot plan review process. This has created issues in the past, and does not follow the Design and Construction Manual.

Although these plans do not include the water line, the placement of the storm sewer in relation to the water line will create a potential issue. We had originally looked at the possibility of allowing the construction of an insulation layer around the pipe, provided the depth of cover was not too shallow. It appears there are instances where the cover is very shallow, and in at least one case, less than 2 feet of cover is provided for the water line. It is unclear why storm lines and/or sanitary sewer lines were placed so shallow as to prevent the installation of water lines to meet the 42 inch cover requirement in the three (3) shallow locations shown on the water line plans. We realize that there may be sanitary sewer conflicts, but our analysis shows that the sanitary sewer can be lowered to make room for the storm sewer lowering, and in at least one condition at curb inlet O5-A, it appears no other adjustment is needed other than lowering the storm lines/curb inlets/boxes. This appears to be the case for curb inlet 12-D, curb inlet O1-F, and curb inlet O5-A. A combination of lowering the storm line and lowering the sanitary sewer line should enable the placement of the water line to the required depth.

Concerning the above comment, we had originally stated that consideration would be given to allowing for substandard depth of cover over the water lines at selected locations contingent upon no other engineering solution being available. It appears there are other alternatives available to achieve compliance with the depth of cover rule. By far the biggest potential issue is the northernmost crossing, where the depth of cover is less than 2 feet, and the line is at a dead end, with no flow. This line will likely freeze.

The sag vertical curve on Cobey Creek Drive, K=23.18, does not meet the minimum design standard.

The sag vertical curve on Aspen Drive, K=22.59, does not meet the minimum design standard.

Provide a signing plan and standard details.

It is recommended that the Master Drainage Plan be incorporated into a standalone Street, Stormwater, Master Drainage Plan, and Land Disturbance Plan. If, however, it is desired to make the Master Drainage Plan a standalone set of plans, then an index of sheets along with a cover sheet, vicinity map, and all other information required on a typical cover sheet should be included. In any case, the Master Drainage Plan must be constructed during the other subdivision improvements, and the Street and Stormwater plans shall not be approved until the Master Drainage Plan is also approved.

Sheet 3 of 4: The City requires a minimum of 2.0 feet from the 100 year water surface elevation, and any location of the lowest opening. It is not clear what procedure was used to develop the table on the bottom of this sheet, because two (2) random spot checks of Lots 8 and 10 showed errors. There may be addtional instances where the 2 foot rule is not met. It appears the MBOEs do not comply with the 2.0 foot requirement. To be clear on what we require, it is acceptable to call out an MBOE for each side of the lot, and provide a note on the Master Drainage Plan which allows for interpolation between the two MBOEs shown on the side lot lines. This allows for interpolation between the 100 year water surface elevation within the rear yard swale for varying water surface elevations. Please re-review this table, and revise as appropriate.

Sheet 3 of 4: The City does not recognize a "WU" (i.e., walkup) basement type. The City only recognizes a standard basement, a daylight basement, and a walkout basement. For purposes of walkout when used in context as shown, this would be considered a walkout basement.

Sheet 2 of 4: Note 7 and Note 8 are incorrect. The City requires a 2.0 foot freeboard rather than 1 foot freeboard shown on the notes. Please be aware that we will also require this be called out as 2.0 feet, not 2 feet.

The rear of Lots 140 to 150 are served by a swale, with no underground routing and conveyance of stormwater. It appears additional underground routing of stormwater is required. Although this was discussed during the Prleliminary Development Plan phase of this project, it was our understanding the drainage area discharging into this swale was less than 2.0 acres. It appears the drainage area shown on Sheet 17 of 33 is greater than 2.0 acres draining to this swale.

Grading shown on Sheet 3 of 33 is no longer needed in the southwest corner, to facilitate installation of the water main loop. Please see the water line plan comments for further information.

Will land disturbance take place prior to approval of these plans? The reason for this question is that the land disturbance plans were submitted as a standalone set. We usually recommend that the land disturbance plans be incorporated into the steet, stormwater, Master Drainage Plan, and land disturbance plan set, but this may or may not be necessary based on the answer to this question.

A stormwater pollution prevention plan (SWPPP) is required prior to approval of the plans.

Sheet 3 of 6 of the land disturbance plans: There are no details concerning the construction of an outlet structure for the temporary sediment basin. Detailed plans must be provided showing how this temporary sediment basin will be constructed, along with sufficient notes or plans showing how the sediment basin will be converted to a permanent detention facility after completion of the project.

In general, the land disturbance plan is seriously lacking in terms of function. Silt fence appears to be the primary method for erosion and sediment control as shown on Sheet 4 of 6, and the silt fence is not placed properly. In order for silt fence to have any chance of limiting the off-site migration of silt and sediment, it must be placed along contours, not parallel to contours as proposed. Substantial revisions to this plan are required.

It is recommended that alternative forms of erosion and sediment control be shown rather than relying solely on silt fence, and a temporary sediment basin which has no construction details.

Land Disturbance Plan General Comment: The plan appears incomplete and lacking in required detail, and lacking in terms of what items will be constructed by a contractor when performing erosion and sediment control on this site.

Street and Stormwater Plans General Comment: All ADA-accessible ramps and ADA-accessible routes across intersections must be thoroughly detailed in the plans. The details shown on Sheets 19, 20, 21, 22, 23, 24, 25, 26 and 27 are insufficient for construction or review purposes. Please see the bullet point items included in Section 5304.8 (i.e., 11 bullet point items) for a complete list of required items necessary for the plans. When providing the required details, please be cognizant of the design requirements contained in Table LS-5 of Sectiion 5305. The City of Lee's Summit design standards are more stringent than shown in PROWAG, and in general, we require no more than a 1.5% cross-slope, and no more than a 7.5% running slope. Finally, "transitions" at the top of the ramp are called-out, but not desired or required unless there is a compelling reason.

Street and Stormwater Plan General Comment: All ADA-accessible ramps, and all sidewalks adjacent to common area tracts, and finally all sidewalks adjacent to unplatted property must be constructed during sudvision construction. Identify each of these items in a clear and concise way, so there is no confusion on where and when these improvements are made. The only sidewalk allowed to be constructed during the building permit process (i.e., during individual home construction), are sidewalks along platted lots. All other sidewalk and ADA-accessible ramps, and ADA-accessible routes across intersections where stop control is present must be constructed along with the improvements shown in these plans.

The 8 foot asphaltic concrete path shown along M-150 should be specified as a 6 inch thick KCMMB concrete sidewalk with a width of 10 feet.

Underdrains must be installed from inlet to inlet at all sag points on the roads. Please identify their location, and provide clear and concise notes, along with a reference to the details shown elsewhere in the plan set, for their construction.

No calculations were provided for the rip rap sizing or rip rap design. Please provide calculations showing how the rip rap was sized, and provide adequate notes in the plans specifying the size of rip rap, the dimensions of the rip rap, the thickness of the rip rap, the length of the rip rap, and the width of the rip rap. The calculations may be shown in the stormwater report, but the plans must show exactly what is being installed without requiring the contractor or inspector to perform any field calculations based on a generic table.

Sheet 13 of 33: Please indicate the future phase between the 2 temporary end sections will be installed during a future phase. Perhaps placing General Note 2 on the profile view?

Please review the plans, and grey-out any future phase activity, along with sufficient notes indicating what the greyed-out features represent.

Sheet 13 of 33: Please grey-out the future lots. It is confusing, and appears to show these lots being part of the 1st phase.

Sheet 31: Please remove these details. These are generic details, and since the plans must include site-specific details for ADA-accessible ramps, the details will contradict them. For future reference, these details are intended for retrofit projects, and provide the minimum standards for construction. The City has adopted more stringent standards discussed elsewhere in these comments, and therefore, the standard details must be removed.

An underdrain details was missing.

A trenching and backfill detail was missing.

A signage plan was missing from the plans. Standard details were also missing concerning signage.

The locations of all ADA-routes across intersections in a "stop-control" configuration was missing from the plans. Where an intersection is under stop control, or under yield control, no more than 1.5% cross-slope with a minimum width of 5 feet must be provided across the intersection at all ADA-accessible ramps. Details must be provided on the plans, along with updated profiles on the street plans to reflect these changes.

Where an ADA-accessible ramp is installed at an interseciton without stop control, then the cross-slope is limited to no more than 5.0% across the street. Mid-block crossings are limited to street grade.

It appears the underground storm lines were sized for the 10 year event, with the hydraulic grade line at the crown of the pipe. There appear to be instances where the 100 year event has no suitable overflow route, other than the street gutter. Will this be sufficient for all aspects of the drainage system? Are there situations where the 100 year event will cause structure flooding?

Sheet 28 of 33: Provide slope call-outs for the longitudinal (i.e., north/south), and the transverse (i.e., east/west) directions within the detention basin bottom.

Sheet 28 of 33: By design, it appears the basin will hold water since there is zero slope in the transverse (i.e., east/west) direction. This is not acceptable. A minimum 2.0% slope should be provided in any direction within the basin.

Sheet 28 of 33: Where is the emergency spillway? Why was it omitted from the plans? Please see specific requirements for the emergency spillway, including the requirement that the emergency spillway be designed to manage all events assuming the primary outlet works are 100% clogged, and zero available storage, with a minimum of 1.0 feet of freeboard from the lowest point of the dam top, to the highest water level in basin during this event.

Sheet 28 of 33: Are you really proposing to use a 48 inch PVC "standpipe" as your primary outlet structure? For a basin this size, this seems highly inappropriate. Typical materials for an important outlet structure managing a basin of this size would be reinforced concrete, with orifices or a perforated riser to manage the 40 hour extended detention requirements, along with suitable orifices and weirs to manage the attnenuation events. There appear to be no provisions for anti-clogging, and it is highly likely this outlet structure will topple-over during the first year of operation. It is also shown directly-connected to the 48 inch pipe, with no junction other than a tee.

The "Final Drainage Report - Phase 1" dated Dec. 11, 2018 contradicts the plans in the following ways: 1) a 475 foot long spillway is discussed, but not shown in the plans, 2) no calculations of the 90% mean annual event storm and associated volumes were presented in the report to support the smaller openings in the outlet structure to provide 40 hour extended detention, 3) no table of contents was presented in the report, including appendices, 4) detention basins on the south end of the project were shown in the report, with no discussion when these are to be constructed, and no indication on the plans when they will be constructed.

Detention Basin Design General Comments: The design shown on Sheet 28 of 33 is lacking in terms of detail, lack of an emergency spillway, and quality of materials. Please review and provide a re-design.

Stormwater Report: Should't the existing condition diagram "points of interest" match the "points of interest" shown on the proposed condition diagram? Also, the existing condition diagram is vague in terms of these points of interest, with no clear indication on the diagram where these points exist (i.e., labels are provided with no leader line or clear indication of where the point is located). Only a label is provided. The points of interest should coincide with the region of convergence between sheet flow and shallow concentrated flow.

Plans are provided in the stormwater report for the south detention basins, with no clear indication when these will be constructed.

A waiver to the Design and Construction Manual shall be required for the release rates specified in the report. In general, a waiver can only be granted in those instances on the "fringe" areas where the post-development peak flow rates are less than the pre-development peak flow rates. We typically grant these waivers when a 20% or more reduction in peak flows can be demonstrated. A specific form shall be provided to you following submission of a revised report.

One sheet is provided in the appendix for "Water Quality Event Extended Release". It is in the form of a graph of elevation, volume, and flow versus time, with no other information concerning the design of the orifices. The body of the report did not appear to discuss the 40 hour extended detention requirement, and how this would be achieved.

As indicated above, a revised stormwater study and detention study is required. A waiver is also required on a form provided by the City, but will need to be submitted when the revised stormwater report has been accepted. This revised report should be referenced in the waiver request, which shall be reviewed by the City Engineer. A template form for this waiver shall be provided when a revised stormwater report has been submitted and accepted by the City.

Sheet 29 of 33: Surface asphaltic concrete type must be called-out. It should be either type 5 or 6. The base course shall be called-out as Type 5.

Sheet 29 of 33: All of the typical sections are incorrect. There are options showing biaxial grid, but the other option shown to the right shows no subgrade stabilization. It only shows compacted subgrade. Revise the typical sections to meet our standard. Also, where biaxial grid is used, either 10 inches or 12 inches of MoDOT Type 5 aggregate is required, not 7 inches, and not 6 inches. If using chemically-stabilized subgrade, then 6 inches MoDOT Type 5 is acceptable. Finally, a dimension call-out must be provided for the area one (1) foot beyond the back of curb. As shown, it is not clear.

Sheet 30 of 33: Curb and gutter replacement details should be removed from the plans. Where on this project will curb and gutter be removed and replaced? If none, please remove this detail.

Stationing must be provided on all typical street section views (i.e., from sta to sta). In addtion, why is CG-1 curb and gutter called-out when CG-2 is appropriate? Finally, there is an instance where the street near M-150 should be classified as a commercial collector, and the pavement design standards are different than residential street design. Provide a typical section view for this commercial collector, and provde a design which matches the requirements shown in Table LS-2 of Section 5200. The base course of asphalt and the chemically-stabilized subgrade requirements differ from the residential street standards for this segment of Cobey Creek Dr.

Please see the most recent update to Table LS-2. Although surface course thickness has not changed since the last revision, the base course has been increased for residential collector streets.

On the section views for the roadway, please indicate whether each segment is a residential local,residential collector street, or commercial collector street.

Sheet 28 of 33: Show the maximum water level in the detention basin for the nominal (i.e., unclogged, system functioning normally) event. Also, show the maximum water level for the 100% clogged, zero available storage event.

Please be aware that as-built Record Drawings of the detention basin shall be required prior to issuance of a Certificate of Substantial Completion.

Sheet 2 of 33: Provide revisions to the general layout sheet to reflect changes to the water main discussed in the water main plan comments.

Master Drainage Plan Comments: Corner elevations were missing. At a minimum, existing and proposed corner elevations are required to the tenth of a foot.

Master Drainage Plan Comments: Contours should be labeled with elevations for not only the existing condition, but the proposed condition.

Master Drainage Plan and General Storm Comment: Addtional storm structures are required in the rear lots of along Riley Way and Carter Rd. Our general rule of thumb is no more than 4 upstream lots without installing an underground storm system to manage stormwater. The same comment applies to the lots on the west side of Corbin Dr. Finally, see previous comments about the lots on the east side of Corbin Dr. The same comment applies to these lots. Without an underground system, downstream lots will be subject to yard flooding.

Master Drainage Plan: Sheet 2 of 4 is missing street name labels.

Master Drainage Plan: The maximum water surface elevation within the basin must be shown for the nominal condition. Also, the clogged condition, zero available storage elevation must also be shown. This can be in the form of a note.

Master Drainage Plan: MBOEs must be called-out for all lots within the development. It appears several are missing. Please be aware of the previous comment which allows for the establishment of sideyard MBOEs, and subsequent interpolation between the two in the instance of a rear yard swale. Sufficient notes should be provided on the Master Drainage Plan which indicate to the plot plan reviewer, that interpolation is allowable if appropriate.

Master Drainage Plan: Swale typical section views are provided for only one (1) swale along the east end of the development. Is it appropriate to provide additional section views for the temporary swale shown? Also, it would appear additional overflow swales are necessary along the rear yards along Riley Way and Carter Rd., after installation of underground stormwater conveyance systems. Swale details should also be provided for these features.

The Roadway Segments Classified as a Commercial or Residential Collector: A minimum of 60 feet right of way is required for collector streets. Sidewalks are required on both sides of the collector, whether it is residential or commercial collector. Pavement width should be wider than shown, with a proposal from the engineer on the width. Typical widths for these collector streets have been from 36 to 40 feet back of curb to back of curb, but this should be confirmed with the City Traffic Engineer. Typical section views should also be provided for these segments, with pavement design details matching Table LS-2 in Section 5200 of the Design and Construction Manual. Finally, HDPE pipe is specifically prohibited in cross-pipe installation beneath collector streets. Please see Section 2602.2D(5) of the KCAPWA for this prohibition.

Other Detention Basin Comments: There is no provision or design for a sediment forebay. With the relatively flat slope on the bottom of this basin, it would appear that a sediment forebay could be designed with a minimum of effort.

Emergency Spillway Design and Placement: The location and discharge for the emergency spillway serving the dry detention basin must be placed in an area which will have no adverse impact on dowstream property owners.

Sheet 10 of 33: Is there a particular reason O1-D junction box and associated storm line is so deep? This will be a potential maintenance issue for the City. It is shown at a depth of 18 feet.

General Comment Related to the 60 inch HDPE Line at O1-D: It appears the calculations are very tight concerning the 10 year event. Given the fact that rainfall data has been recently updated with Atlas 14, wouldn't it be prudent to provide a better margin of error? As designed, the pipe is flowing at capacity for the 10 year event, with no allowance for error.

The same comment above would apply to Storm Line 15 and 16 shown on Sheet 16 of 33. There appears to be no margin for error, and it appears the old rainfall data was used.