Lee's Summit

The document entitled "Base Flood Determination in Unnumbered A Zone at Summit Point Apartments Phase II" dated July 1, 2021 states the highest base flood elevation of 1000.9 as the highest base flood elevation for the site. This higher number shall be used for the site.

City staff has discussed with the City Floodplain Adminstrator, and the higher elevation described above shall be used rather than the base flood elevation reported to FEMA and contained within the LOMA.

Please provide the Special Warranty Deed recorded at Jackson County, Missouri for which this LOMA is based. Document is 2017E0081290. We cannot provide any further review until this document has been submitted for review. It must also include a graphic format exhibit showing the boundaries of the property described in the Special Warranty Deed, along with suitable references to property lines, right of way, adjacent property, etc.

DE C&O #01 Eng Plans – FDP/PDP

Floodplain delineation at 11086 does not agree with the report. It appears the delineation at this location was based on the lower mannings n values shown in the sensitivity analysis. Text of the report recommended 0.045 for the channel, and 0.10 for the overbank area, with a corresponding WSE 100 of 1003.71 at that location.

DE C&O #03 Eng & Insp Fees

Using the mannings n values shown in the text of the report, the base flood elevation in the vicinity of 11086 is too close to determine. It lies very close to the property line, and as such, that area could be interpreted as being either in the floodplain or outside the floodplain.

DE C&O #04 Cert FA or Escrow

Using the "ineffective flow area" tool in HEC-RAS requires that a real world assessment be made upstream of the "ineffective flow area". In this case, the stream goes out of its banks at 11086 where the levy does not exist, and travels northward into this "ineffective flow area". According to the report, the only flows shown within this side channel behind the levy (i.e., the "ineffective flow area") were from the on-site drainage area. It did not include the 100 year flows that are outside the stream bank at 11086. The limits of the floodplain, therefore, will be larger than shown.

DE C&O #06 Land Disturbance

In lieu of providing a 1D manual calculation of the floodplain limits described in the above comment, it may be necessary to perform more advanced modeling (e.g., partial 2D connected to 1D) to account for the stream leaving its banks upstream of the levy.

DE C&O #07 Easements

Modeling in the northeast corner of the site show a small hydraulic jump occurring. Recommend using the highest value for the base flood elevation in the subcritical region (i.e., 995.00) rather than the elevation at this transient hydraulic jump. Reliance on a transient hydraulic jump to occur to determine a base flood elevation is not a conservative practice, and not recommended.

DE C&O #09 FDP Reviews

A Letter of Map Revision (LOMR) shall be obtained by the applicant prior to approval of the Final Development Plan.

DE C&O #11 Pavement Thickness

All required engineering plans and studies, including water lines, sanitary sewers, storm drainage, streets and erosion and sediment control shall be submitted along with the final development plan. All public infrastructure must be substantially complete, prior to the issuance of any certificates of occupancy.

DE C&O #01 Eng Plans – FDP/PDP

Floodplain delineation at 11086 does not agree with the report. It appears the delineation at this location was based on the lower mannings n values shown in the sensitivity analysis. Text of the report recommended 0.045 for the channel, and 0.10 for the overbank area, with a corresponding WSE 100 of 1003.71 at that location.

DE C&O #03 Eng & Insp Fees

Using the mannings n values shown in the text of the report, the base flood elevation in the vicinity of 11086 is too close to determine. It lies very close to the property line, and as such, that area could be interpreted as being either in the floodplain or outside the floodplain.

DE C&O #04 Cert FA or Escrow

Using the "ineffective flow area" tool in HEC-RAS requires that a real world assessment be made upstream of the "ineffective flow area". In this case, the stream goes out of its banks at 11086 where the levy does not exist, and travels northward into this "ineffective flow area". According to the report, the only flows shown within this side channel behind the levy (i.e., the "ineffective flow area") were from the on-site drainage area. It did not include the 100 year flows that are outside the stream bank at 11086. The limits of the floodplain, therefore, will be larger than shown.

DE C&O #06 Land Disturbance

In lieu of providing a 1D manual calculation of the floodplain limits described in the above comment, it may be necessary to perform more advanced modeling (e.g., partial 2D connected to 1D) to account for the stream leaving its banks upstream of the levy.

DE C&O #07 Easements

Modeling in the northeast corner of the site show a small hydraulic jump occurring. Recommend using the highest value for the base flood elevation in the subcritical region (i.e., 995.00) rather than the elevation at this transient hydraulic jump. Reliance on a transient hydraulic jump to occur to determine a base flood elevation is not a conservative practice, and not recommended.

DE C&O #09 FDP Reviews

A Letter of Map Revision (LOMR) shall be obtained by the applicant prior to approval of the Final Development Plan.

DE C&O #11 Pavement Thickness

All required engineering plans and studies, including water lines, sanitary sewers, storm drainage, streets and erosion and sediment control shall be submitted along with the final development plan. All public infrastructure must be substantially complete, prior to the issuance of any certificates of occupancy.

Floodplain delineation at 11086 does not agree with the report. It appears the delineation at this location was based on the lower mannings n values shown in the sensitivity analysis. Text of the report recommended 0.045 for the channel, and 0.10 for the overbank area, with a corresponding WSE 100 of 1003.71 at that location.

Using the mannings n values shown in the text of the report, the base flood elevation in the vicinity of 11086 is too close to determine. It lies very close to the property line, and as such, that area could be interpreted as being either in the floodplain or outside the floodplain.

Using the "ineffective flow area" tool in HEC-RAS requires that a real world assessment be made upstream of the "ineffective flow area". In this case, the stream goes out of its banks at 11086 where the levy does not exist, and travels northward into this "ineffective flow area". According to the report, the only flows shown within this side channel behind the levy (i.e., the "ineffective flow area") were from the on-site drainage area. It did not include the 100 year flows that are outside the stream bank at 11086. The limits of the floodplain, therefore, will be larger than shown.

In lieu of providing a 1D manual calculation of the floodplain limits described in the above comment, it may be necessary to perform more advanced modeling (e.g., partial 2D connected to 1D) to account for the stream leaving its banks upstream of the levy.

Modeling in the northeast corner of the site show a small hydraulic jump occurring. Recommend using the highest value for the base flood elevation in the subcritical region (i.e., 995.00) rather than the elevation at this transient hydraulic jump. Reliance on a transient hydraulic jump to occur to determine a base flood elevation is not a conservative practice, and not recommended.

A Letter of Map Revision (LOMR) shall be obtained by the applicant prior to approval of the Final Development Plan.

DE C&O #01 Eng Plans – FDP/PDP

All required engineering plans and studies, including water lines, sanitary sewers, storm drainage, streets and erosion and sediment control shall be submitted along with the final development plan. All public infrastructure must be substantially complete, prior to the issuance of any certificates of occupancy.

DE C&O #03 Eng & Insp Fees

All Engineering Plan Review and Inspection Fees shall be paid prior to approval of the associated engineering plans and prior to the issuance of any site development permits or the start of construction (excluding land disturbance permit).

DE C&O #04 Cert FA or Escrow

All subdivision-related public improvements must have a Certificate of Final Acceptance prior to approval of the final plat, unless security is provided in the manner set forth in the City's Unified Development Ordinance (UDO) Section 7.340. If security is provided, building permits may be issued upon issuance of a Certificate of Substantial Completion of the public infrastructure as outlined in Article 3, Division V, Sections 3.540 and 3.550 and Article 3, Division IV, Section 3.475 of the UDO, respectively.

DE C&O #06 Land Disturbance

A Land Disturbance Permit shall be obtained from the City if groundbreaking will take place prior to the issuance of a site development permit, building permit, or prior to the approval of the Final Development Plan / Engineering Plans.

DE C&O #07 Easements

All permanent off-site easements, in a form acceptable to the City, shall be executed and recorded with the Jackson County Recorder of Deeds prior to the issuance of a Certificate of Substantial Completion or approval of the final plat. A document number shall be submitted to the City for verification.

DE C&O #09 FDP Reviews

Certain aspects of the development plan will be further reviewed during the Final Development Plan phase of the project. This includes detailed aspects of the design to help ensure that the plan meets the design criteria and specifications contained in the Design and Construction Manual.

DE C&O #11 Pavement Thickness

Private parking lots shall follow the Unified Development Ordinance for pavement thickness and base requirements.

DE C&O #12 Cut & Fill

Any cut and / or fill operations, which cause public infrastructure to exceed the maximum / minimum depths of cover shall be mitigated by relocating the infrastructure vertically and / or horizontally to meet the specifications contained within the City’s Design and Construction Manual.

Code Statement

All issues pertaining to life safety and property protection from the hazards of fire, explosion or dangerous conditions in new and existing buildings, structures and premises, and to the safety to fire fighters and emergency responders during emergency operations, shall be in accordance with the 2018 International Fire Code.

FDC

IFC 903.3.7 - Fire department connections. The location of fire department connections shall be approved by the fire code official. Connections shall be a 4 inch Storz type fitting and located within 100 feet of a fire hydrant, or as approved by the code official. Several of the buildings do not meet this requirement and will need to be corrected on the Final Development Plan.

Imposed Loads

IFC 503.2.3 - Fire apparatus access roads shall be designed and maintained to support the imposed loads of fire apparatus and shall be surfaced so as to provide all-weather driving capabilities.

Misc.

All hydrants and the asphalt base of the parking lot shall be installed and hydrants operational before going vertical with combustible construction materials.

Please refer to comment #6 in the applicant letter dated Mar. 29, 2021. The "Preliminary Stormwater Drainage Study" dated Apr. 5, 2021 (hereinafter referred to as the preliminary stormwater study) still contains the statement "The City requires that no construction be allowed within the stream setback, with the exception of stormwater detention basins" on page 2. While this may be partially correct, the City will consider grading within the stream buffer for detention basins on a case-by-case basis. Please correct the report as appropriate.

The figure on page 3 of the preliminary stormwater study is illegible due to pixelation of the diagram. No review was performed.

Page 4 of the preliminary report states that City personnel participated in the determination of the OHWM. The City only observed the delineation of the OHWM by Frank Norman, so this statement is not accurate. Please revise.

Page 8 of the preliminary stormwater study included a diagram which is illegible due to pixelation. No further review was performed.

Page 10 of the preliminary stormwater study included a diagram which is illegible due to pixelation. No further review was provided.

Page 11 of the preliminary stormwater study included a diagram which is illegible due to pixelation. No further review was performed.

Page 14 of the preliminary stormwater study included a diagram which is illegible due to pixelation. No further review was performed.

Page 14 of the preliminary stormwater study states in the second paragraph "...results of the HEC-RAS model showed the 100 year flood elevations...ranging from 994.3 to 1005.1." The report goes on to state that buildings were set above this level. This does not reconcile with the finish floor elevations shown for A2-2 and C1-2, which show the finish floor elevations at 1005.00, which is below the calculated base flood elevation. The City requires 2.00 feet of freeboard (preferably higher) between the calculated 100 year water surface elevation and the the lowest floor elevation.

HEC-RAS study has not been formally reviewed as of this date. Final results of an accepted study will affect the lowest floor elevations of the buildings, the bottom of the detention basin, and the location of the detention basin.

Energy dissipation at the end of the discharge point does not appear sufficient for this project, and will likely have a negative impact on the adjacent property owner to the north. Rip rap appears to be shown, but extends approximately one pipe diameter into the floodplain. Preliminary calculations shall be provided for the dimensions of the energy dissipation measure. Other alternatives for energy dissipation should be considered, such as field-tested designs by the Federal Highway Administration to induce a hydraulic jump within the energy dissipation device over a wide range of flow regimes.

Off-site easements or off-site acquisition of property is required for the energy dissipation device shown on the preliminary development plan. This shall be required prior to approval of the Final Development Plan.

Geometry shown for outlet structure in the text of the report and within contradictory diagrams within the preliminary stormwater study appendix will bypass the water quality aspects of the basin. Short-circuiting effect of outlet structures constructed in this fashion negate the residence time in the basin. Traditional design should be shown rather than the off-line structure.

The 100 year water surface elevation was shown graphically for the detention basin, but the incorrect condition was shown. The 100% clogged/zero available storage elevation shall be shown, and shall be a minimum of 20 feet from any building and any property line. This is a requirement of Section 5600 of the KCAPWA stormwater requirements, which have been adopted by reference by the City of Lee's Summit. Rough calculations by City show this will not be met for the northeast basin if showing the above condition. It will be too close to Building C1-2 and the east property line.

A concrete "trickle channel" is shown in the bottom of the detention basin. Construction of these low flow channels tend to negate the water quality aspects of detention basins. Recommend soliciting input from a design professional at the final plan phase for appropriate plantings, soil amendments, or other measures to help drain the area of low slope.

There appear to be areas behind building A2-2 with slopes in excess of 3:1. These areas will either need a geotechnical report to assess the global stability of the slope, or retaining walls installed.

Commentary within the preliminary stormwater study appears to discuss an off-line outlet structure, as well as the illegible diagram contained below the commentary. Appendix within the report contradicts this discussion and the illegible diagram. Grading plan and utility plan in the appendix of the study show a more traditional outlet structure location. Please see previous comment concerning the off-line outlet structure.

DAM-2 shown within the appendix of the preliminary stormwater report appears to show the off-line outlet structure, contradicting the previous grading plan and utility plan.

Sheet C3 Site Plan and C4 Grading Plan: A sidewalk is shown along building A2-2 and C1-2. These are shown in areas where grading is shown, some over the 3:1 max slope discussed in previous comments. Sidewalks cannot be installed over 3:1 slope without grading to max. 2.0% slope for the sidewalk cross-slope, and it is unclear how this will work without grading within the floodplain or stream buffer.

Code Statement

All issues pertaining to life safety and property protection from the hazards of fire, explosion or dangerous conditions in new and existing buildings, structures and premises, and to the safety to fire fighters and emergency responders during emergency operations, shall be in accordance with the 2018 International Fire Code.

FDC

IFC 903.3.7 - Fire department connections. The location of fire department connections shall be approved by the fire code official. Connections shall be a 4 inch Storz type fitting and located within 100 feet of a fire hydrant, or as approved by the code official. Several of the buildings do not meet this requirement and will need to be corrected on the Final Development Plan.

Imposed Loads

IFC 503.2.3 - Fire apparatus access roads shall be designed and maintained to support the imposed loads of fire apparatus and shall be surfaced so as to provide all-weather driving capabilities.

Misc.

All hydrants and the asphalt base of the parking lot shall be installed and hydrants operational before going vertical with combustible construction materials.

The standard parking space dimensions shall not be less than nine feet wide by 19 feet long. Where the head of the parking space abuts a six-foot wide sidewalk or curbed landscaped area, the length of the parking space may be reduced by two feet to allow for vehicle overhang. Such overhang shall be measured from the face of the curb. As proposed the parking stall are 17’ & 17.5’. To ensure compliance with the UDO requirements please label the depth of adjacent sidewalks where the parking stalls are less than 19’.

The requested discussion and analysis of the ordinary high water mark (OHWM) and stream buffer delineation was incomplete. The preliminary stormwater study mentioned the stream buffer, but did not discuss the rationale behind the selection of the OHWM along stream channel. A note was provided on the PDP plan stating the OHWM locations were established "by field survey", with no explanation given within the preliminary stormwater study concerning the criteria used to establish the OHWM locations along the stream channel.

The Public Works - Environmental Group conducted a review of the proposed stream buffer in relation to the OHWM. According to their field investigation, it appears the stream buffer should be located further away from the alignment of the stream than shown.

The requested floodplain delineation appeared to be incomplete. The northeast corner of the site appeared to lack a CFS-calculated BFE line. It would appear the line will be located in a portion of the northeast detention basin dam. Any fill within the flood zone calculated by CFS would require a Floodplain Development Permit, and any fill would require compensatory storage to be provided elsewhere within the flood zone. It is not clear how compensatory storage could be provided for this site, therefore, the floodplain delineation using the CFS-calculated BFEs shall be better-defined in the northeast portion of the project prior to approval of the PDP.

The latest submittal shows Apartment building A2-2 with rear access walks at 3:1 slope. A retaining wall is likely needed, similar to that shown for C1-2.

The requeted HEC-RAS base flood study included within the preliminary stormwater study shall be considered "prelliminary" at this time. We are concerned, however, that no analysis of the frequent storm event was presented within the report, which might help establish the location of the OHWM.

The preliminary stormater study states that "detention basins are allowed within stream buffers". While this statement may be partially correct, detention basins may be allowed on a case-by-case basis. Previous submittal of northwest detention basin included a proposal which would de-stablize an existing channel, and would likely create a new fork in the channel. Therefore, this basin location was rejected. Please revise the report to reflect the case-by-case allowance of detention basins within stream buffers, which this particular detention basin would qualify based on the fact that fill for the dam will encroach into the buffer rather than the entire basin.

Final review and approval of the calculated BFEs within the unnumbered A zone shall be performed by the Floodplain Administrator for the City of Lee's Summit, (i.e., the City Engineer). As previously discussed in this comment letter, the HEC-RAS analysis is considered preliminary, pending submittal of a final standalone report. We would recommend this report be submitted well in advance of the Final Development Plan.

Alternatively, the applicant may request a formal review of the BFE study prior to approval of the PDP.

Any formal review by the City Floodplain Administrator of the BFEs within this unnumbered A zone shall require the preparation of a separate standalone document, including HEC-RAS report, appendices, and an upload of digital HEC-RAS model files. Final report shall include recommendations for the proposed BFEs along selected cross-sections of the stream.

Fill is shown in within the stream buffer behind building C1-2 and A2-2. This is not allowed.

Grading Plan: It appears the CFS-calculated BFE layer was turned-off on this drawing. It is difficult to determine whether fill is shown within the floodplain. Please turn this layer on.

Grading Plan: Bldg. A2-2 proposes fill within the stream buffer, especially within the side channel buffer. This is not allowed. The bigger question is whether a buffer is needed on the side channel. Drainage area is less than 40 acres for the side channel?

As previously requested, the emergency spillway location was not shown. Only the detail was provided.

Previous submittal included general location of interior storm lines, field inlets, junction boxes and curb inlets to properly drain the project. Latest submittal does not appear to show all of these features. In particular, where are the proposed discharge points to the basin? What inlets will direct stormwater to this basin? Although this is a preliminary plan, a preliminary concept for the storm system is required.

Previously-requested emergency spillway detail on Sheet C8 Details in the PDP shows the clogged condtion will overtop the dam. The prelimnary stormwater study appears to contradict this drawing, however. A minimum of 1 foot freeboard is required. It would appear the freeboard is achieved as per the preliminary stormwater study, but drawing on Sheet C8 contradicts the report.

Previously-requested location of detention basin outlet structure and discharge method was not shown on the grading plan. General location is shown on the utility plan, but omitted from the grading plan. It is difficult to determine whether this layout will work with the proposed grading, but it appears the pipe will be aerial toward the creek, which is not allowed. It would appear the outlet might be better suited to placement within the dam fill, similar to a culvert being installed within a roadway embankment, with appropriate energy dissipation measures installed at the end of pipe.

Previously-requested energy dissipation at the end of the discharge pipe was not shown.

Water quality orifice was shown within the baffle wall of the outlet structure detail. We have seen designs where the water quality orifii are installed outside the outlet structure or with a perforated riser concept, with anti-clogging measures designed. As shown, this outlet structure would likely be a high-maintenance item within a confined space, with frequent unclogging necessary to drain the pond after frequent storm events.

The preliminary stormwater study was missing the PondPack output for the 10 and 100 year events. Only a summary was provided within the text of the report, but the associated appendices (as were provided for the 2 year event) were missing.

The elevations of the water quality orifice and the 34 inch orifice on Sheet C8 Details do not match what is shown in the preliminary stormwater report.

Sheet C8: The outlet structure configuration does not appear to be designed for the 100 year event. A 34 inch orifice is shown within what appears to be a baffle wall, which is connected to a 42 inch outlet pipe. It is our understanding the 42 inch discharge pipe is designed for the 100 year event, but the 34 inch orifice will limit the outflow to that of a 34 inch equivalent pipe (plus the minor effects of adding the 2.25 inch water quality orifice).

Emergency Spillway: Emergency spillways do not necessarily need to be installed along the dam fill. They may be incorporated into the primary outlet works. If this option is desired, the primary outlet works for the clogged condition/zero available storage would include the weir/orifice combinations prior to the 42 inch exit pipe. The top of the outlet structure could be left open, as long as stormwater can enter the top without clogging of the primary outlet works. A domed grate or other anti-clogging measure would be required on the top of this open structure. Regardless of the method for providing emergency release of stormwater, this emergency spillway shall be designed to only function in the event of primary outlet structure (i.e., the weir/orifii combination within the outlet structure) clogging. It should not be designed to manage the 100 year "unclogged" event, which appears this was the case for the proposed geometry of the outlet structure.

Elevation Certificates shall be required for each habitable structure constructed with this project (to be submitted prior to building permits and post-construction). These certificates shall be based on the BFEs established for the unnumbered A zone.

As requested in the previous applicant letter, please provide elevations at selected intervals on the grading plan. It is difficult to ascertain the contour interval and elevations without making assumptions. We assumed a one foot contour interval, and made some assumptions based on what appeared to be correct. However, it would be beneficial to provide key elevations to ensure there are no misunderstandings.

As previously discussed, the downstream triple culvert at Swann Cir. is acting as the outlet structure for a detention basin and should have been discussed within the preliminary stormwater study in the context of a detention basin.

Code Statement

All issues pertaining to life safety and property protection from the hazards of fire, explosion or dangerous conditions in new and existing buildings, structures and premises, and to the safety to fire fighters and emergency responders during emergency operations, shall be in accordance with the 2018 International Fire Code.

FDC

IFC 903.3.7 - Fire department connections. The location of fire department connections shall be approved by the fire code official. Connections shall be a 4 inch Storz type fitting and located within 100 feet of a fire hydrant, or as approved by the code official. Several of the buildings do not meet this requirement and will need to be corrected on the Final Development Plan.

Imposed Loads

IFC 503.2.3 - Fire apparatus access roads shall be designed and maintained to support the imposed loads of fire apparatus and shall be surfaced so as to provide all-weather driving capabilities.

Misc.

All hydrants and the asphalt base of the parking lot shall be installed and hydrants operational before going vertical with combustible construction materials.

Please show the location of all oil and gas wells, whether active, inactive, or capped. A visual inspection of the property will not provide adequate assurance a well or former well is not present on the property. Please cite an official source to ensure no wells are present.

Please provide building elevations with the proposed exterior materials and the building height labeled. Please provide this information for each building type you are proposing.

Please provide a narrative statement that requests and explains the justification for modifications of the applicable zoning district regulations (parking reduction & density).

The preliminary plat show lot lines that would appear to go through proposed buildings (A2-3, B1-1 & A2-2). This will not be allowed.

Buildings must be setback from a lot line a minimum of 10’. Building B1-1 appears to have a 0’ setback from the property line on the south side of the building. Please update the plat boundaries to meet the UDO required setback. If you wish to seek a modification for this please provide a written request and justification for such.

CG-1 concrete curbing required around all parking areas and access drives in office, commercial and industrial districts. Temporary asphalt curbs may be used in areas to be expanded only as shown and approved on the development plan. Please label the propose curb type and provide standard details for the curbing.

Please provide details for the proposed ADA parking signs, stalls and aisles. Additionally, as proposed it does not appear you are proposing to provide any van accessible stalls. Please ensure all accessible parking comply with the requirements of the federal Americans with Disabilities Act.

The elevation sheets depicting the trash enclosure seems to shoe wooden gates. Wood in not an approved material. Sheet A108 has the gates labeled as metal. Please update the sheets to be consistent with what is being proposed.

Please provide a north arrow with the vicinity map.

If any signs are proposed they must comply with the sign requirements as outlined in the sign section of the ordinance and will be reviewed under separate application.

Will the entrances into the shared breezeways be gated/secured for access by the residents only or will they be open to the public?

The preliminary stormwater study states the backwater from the stream will have minimal impact on the discharge from the detention basins. If placing detention basins within the stream buffer, they need to be placed such that the storage volume is calculated from the 100 year water surface elevation or higher. That volume should be subtracted from the available storage to account for the stream backing up within the basins.

Manual calculations of the base flood elevations along the rear of the property are required. Although it appears 100 year water surface elevation calculations are discussed within the stormwater report, it must be discussed in the context of an official manual calculation of the base flood elevations to comply with FEMA and the City Floodplain Ordinance. In all instances where base flood elevations are missing from the FIRM, the engineer is responsible for making an official determination of the base flood elevations along selected points, with concurrence from the City. This should be specifically discussed within the stormwater report. Finally, a map should be prepared showing these limits in relation to a topgraphic survey. This becomes the horizontal areal limit of the floodplain with concurrence from the City.

The limits of the floodplain are shown in an approximate basis (appear to be based on the FEMA floodmap), but do not make sense when comparing to existing contours. It will be necessary to determine the base flood elevations along selected points using a manual calculation method discussed above, and then superimpose the limits of the floodplain onto the plan view with elevations of the existing grade, with the existing contours controlling the limits of the floodplain.

The results of the above floodplain delineation will determine whether a floodplain development permit is required for grading work within the floodplain. If grading is performed within the limits of the actual floodplain (i.e. based on the as-surveyed limits), it will be necessary to demonstrate "no net gain" in fill, due to the lack of an estalbished floodway.

The stormwater report states that a 1 inch orifice will be used to regulate the 40 hour extended detention. Our experience shows that reliance on a 1 inch orifice is not a practical solution to providing extended detention. Clogging will be a issue after every rain event. A more elaborate design is required to manage the 40 hour extended detention requirement, and prevent clogging.

The stormwater report states that the FEMA floodplain boundaries shown on the FIRM are accurate when compared to the actual topography. We respectfully disagree. Although the FIRM map is somewhat accurate, the results of the topographic survey should be superimposed upon the base flood elevation map (i.e., to be created by the engineer) described earlier. This will define the limits of the 100 year floodplain.

The stormwater report states that the development will not negatively impact any downstream drainage system. This is not completely accurate since adherence to our stormwater requirements in terms of detention will result in a greater volume of stormwater discharged from the site, although released at a lower rate. In other words, total energy will increase, but at a lower power level at the point of discharge. The purpose of the stormwater report is to demonstrate compliance with City requirements for floodplain development, detention, impact to downstream systems, etc. The purpose is not to demonstrate "no impact", because that is not an accurate statement. This issue has come up in prior public hearings, so this should be clear.

A pre-development (i.e., existing conditions) drainage map is required, showing the points of interest (i.e., the points where sheet flow converge to concentrated flow).

The proposed conditions drainage map does not show any points of interest described above, where sheet flow drainage converges to concentrated flow. It should be shown with the points of interest so a comparison can be made with the existing conditions drainage area map. Allowables should be calculated for each point of interest. If intervening land (i.e., land owned by someone other than the developer) exists between one point of interest and another, an increase in the allowable for one point of interest with a subsequent decrease in the next point of interest may be prohibited.

None of the allowable release rates will be achieved as evidenced by the allowable versus proposed conditions table. Waivers to our allowable release rates will not be supported by staff due to downstream flooding concerns.

Please label all existing interior water lines as "to be designated private". This would include the water lines that are contained within easements to be vacated under separate application.

Please label all existing interior sanitary lines as "to be designated private". This would include the sanitary lines that are contained within easements to be vacated under separate application.

The 100 year water surface elevation within the detention basins must be shown in numeric format and graphic format on the plan view. A minimum of 20 feet is required between this water surface elevation, and any property line or building. A min. 2.0 feet of freeboard between this elevation and the lowest opening in the buildings (i.e., the lowest floor in this case). This should be based on the clogged condition, zero available storage elevation within the basins.

The plan views for the detention basins are missing the location of the outlet structures, emergency spillways, and points of discharge presumably towards the creek. The locations of the discharge points into the creek must not adversely affect downstream or adjacent property owners (i.e., the discharge points must be pulled-back sufficiently far from any property lines allow for the installation of energy dissipation measures wholly within the limits of the applicants property).

On the grading plan, please show the existing elevations for the contours. It is difficult to determine what is being proposed near the detention basins, and to what extent these basins are being constructed in a cut situation as opposed to a fill situation. This may have a bearing on the requirements for an emergency spillway if the basins are constructed solely in a cut situation.

A separate plan sheet should be provided showing the stream buffer limits for the entire project (including the west buffer along the smaller tributary), along with all buildings, parking lots, detention basins, and amenities superimposed upon the background. The stream buffer sheet must show: 1) the ordinary high water mark, 2) the dimensions of the buffer in relation to the ordinary high water mark, and 3) the stream buffer.

The west detention basin appears to show a bottom elevation well below the existing receiving elevation within the creek, with essentially no dam other than a short 3 foot berm to protect it from the stream channel. Although the City can consider placement of these basins within stream buffers, the basin should have a positive benefit to the creek rather than a negative impact. As shown and in consideration of the grading shown with very little protection from the existing stream, this will require a waiver to the Design and Construction Manual. A stream assessment would be required to obtain this waiver. In addition, the placement of this basin in the location shown will in our opinion lead to rechannelization of the stream, and will likely require the acquisition of a USACE permit for rechannelization of a jurisdictional stream.

Wouldn't the triple 48 inch culvert at Swann Circle be the controlling factor for determination of the 100 year base flood elevation for this site? It appears this was not taken into account, but unclear since the results of the HEC-RAS setup were not included in the preliminary stormwater report. If using HEC-RAS to make the estimate for base flood elevation within this flood zone with no base flood elevations determined, the results of the HEC-RAS model run and setup sheets must be included within the report. It would also be beneficial for the City to obtain the raw data files.

Page 8 of the preliminary stormwater report states that the northeast corner of the site has a flowline elevation within the creek of 998.35. This does not appear to make sense when comparing to GIS, the computed 100 year water surface elevation at this location, or the grading plan. Was this a typographical error?

It appears the lowest floor elevations for the north buildings might be too low if comparing to the 100 year clogged condition/zero available storage (these were not provided since no discussion of the emergency spillway was provided). Please check to confirm. This requirement also applies to the base flood elevations within the regulatory floodplain, so the higher elevation would govern if higher.

The west basin appears to be a large depression within the buffer zone. It will actually act as a catalyst to changing the existing creek channel. Staff cannot support such a basin, with no provision for drainage, and an increased likelihood of stream re-channelization. As we discussed during the pre-application meeting, we can support basins within the buffer zone, provided they have a positive effect on the stream. In our opinion, this basin (as designed) will have a severe negative impact on the stream in terms of stability of the existing channel, and will also increase the likelihood of long-term property damage to the apartment building immediately adjacent to this depression.

A field inspection revealed what would appear to be the development of a secondary channel split in the process of developing in the vicinity of the west basin. This is evidence the ordinary high water mark is further south than calculated. There may be the need to re-evaluate the locaton of the stream buffer in this area.

If the stream buffer was measured from the wrong point, this may affect the feasibility of bldg. A2-2. From our calculations, the stream buffer limits would be well into the footprint of Bldg. A2-2.

Code Statement

All issues pertaining to life safety and property protection from the hazards of fire, explosion or dangerous conditions in new and existing buildings, structures and premises, and to the safety to fire fighters and emergency responders during emergency operations, shall be in accordance with the 2018 International Fire Code.

FDC

IFC 903.3.7 - Fire department connections. The location of fire department connections shall be approved by the fire code official. Connections shall be a 4 inch Storz type fitting and located within 100 feet of a fire hydrant, or as approved by the code official. Action required: Show the location of the FDC and the fire hydrant within 100 feet.

Imposed Loads

IFC 503.2.3 - Fire apparatus access roads shall be designed and maintained to support the imposed loads of fire apparatus and shall be surfaced so as to provide all-weather driving capabilities.

Misc.

All hydrants and the asphalt base of the parking lot shall be installed and hydrants operational before going vertical with combustible construction materials.