23.100 Floodplain Development Memo.pdf

hdrinc.com 1670 Broadway, Suite 3400, Denver, CO, Suite 3400, Denver, CO 80202-4824

(303) 764-1520

Memo Date: Friday, January 23, 2026

Project: SD FLAP SDGFP North Point – RTE 900

To: Matt Steiner, PM, CFLHD

From: Amy Finseth, HDR

Subject: North Point Boat Ramp Parking Lot - Floodplain Development Permit

Matt, The North Point Boat Ramp Parking Lot will not need a Floodplain Development Permit based on conversations with Micheal Kotab, Floodplain Administer for Charles Mix County, South

Dakata. The information contained in this memo is the pertinent design drawings and background data that was sent to the County along with the correspondence that provides the

County’s determination that a permit is not required.

The proposed pavement work of the North Point Boat Ramp Parking Lot is located entirely within a Federal Emergency Management Agency (FEMA) regulated Special Flood Hazard Area

(SFHA), Zone A. An SFHA designated as Zone A does not have a detailed study of determined base flood elevation (BFE).

The FEMA Flood Insurance Rate Map (FIRM) for Charles Mix County, South Dakota Map

Number 46023C0575C, effective date June 2, 2004/Yankton Sioux Tribe 461204.

The Charles Mix County Floodplain Administrator, Michael Kotab, was contacted on 11/5/25. A description of work, site map, typical section, plan layout and FEMA FIRMETTE were provided for review.

Mr. Kotab confirmed on 11/6/25 that as the project is primarily a replacement of existing pavement and no significant fill is being added, there are no permits or County approvals required.

Attached is the information provided to Mr. Kotab and correspondence.

The proposed parking lot reconstruction will not impact base flood elevations because the project consists of removing material and repaving the surface, which will not change ground elevations from existing conditions. Therefore, the project complies with Federal Lands Highway

PDDM and 44 CFR 60.3 criteria for an approximate FEMA Zone A - Special Flood Hazard Area.

MISSOURI RIVER

297th St

CHARLES MIX COUNTY

s t A v e

150 300075150

Scale in feet

N

906+

907+

908+00

909+00

910+00

Schedule A

SD FLAP SDGFP PARKING(1)

900+00.00

BEGIN PROJECT

Schedule A

SD FLAP SDGFP PARKING(1)

908+40.90

END PROJECT

To Pickstown

3 miles

T o L a k e A n d e s m ile s

S it e M a p

S h e e t] c p w w o r k in g \c e n tr a l0

\d

\S

T E

S

D G

F P

.d g n

:5

P

M

A u g u s t

5 SITE MAP

PROJECT

NUMBER

SHEET

NORTH POINT PARKING LOT

SD FLAP SDGFP PARKING(1)

A5

LC

16'-19' (match existing width)31'14'14'36'16'-19' (match existing width)5' 5' top asphalt lift)

Fog seal (applied to

(placed in two lifts)

3.5" Asphalt concrete pavement

6" Roadway aggregate, method 2 asphalt lifts)

Tack coat (between to first asphalt lift)

Prime coat (applied prior

Limit

Stake

Slope

Existing Ground

Limit

Stake

Slope

LC

varies from 3" to 4"

Existing aggregate base depth varies from 0.5" to 3"

Existing asphalt pavement depth

9.5" Roadway excavation

(placed in two lifts)

3.5" Asphalt concrete pavement

6" Roadway aggregate, method 2 for structural section details

See mainline typical section

Shoulder up with aggregate base

(safety edge)

Construct 30° pavement edge

See Detail A

9.5" Roadway Excavation

Stabilization geotextile

Stabilization geotextile

Construction Limits

Drive Lane Parking Spaces Drive Lane Drive Lane Parking Spaces Drive Lane

Match existing Match existing Match existing

Match existing Match existing

Match existing

900+00.00 to 908+40.90

RTE 900 NORTH POINT PARKING

TYPICAL SECTION

127'

Average existing width

900+00.00 to 908+40.90

RTE 900 NORTH POINT PARKING

EXISTING TYPICAL SECTION

906+46.09 to 907+22.33

ABA PARKING PAD

RTE 900 NORTH POINT PARKING

TYPICAL SECTION

1.75%

4. Roadway excavation work includes removal of existing asphalt, aggregate, and subgrade.

slopes during final grading. Paid as placing conserved topsoil.

concrete pavement surfacing, grade the windrowed topsoil material onto the final roadway fill edge. Incidental to clearing and grubbing, not paid separately. After completion of final asphalt

3. During clearing and grubbing, windrow existing topsoil material outside of the existing roadway

1:3, to match existing slopes.

Construct a 1:4 or flatter foreslope. Steepen the foreslopes as necessary, but not steeper than 2.

Dimensions shown are approximate and may be varied by the CO.1.

Note:

DETAIL A

1:3 MAX

:1

1' limits and Topsoil

Seeding

Clearing, limits and Topsoil

Seeding

Clearing, 0.16TOTALS (mi)

840.9TOTALS (ft)

840.9900+00.00 to 908+40.90

(ft)

Roadway Station to Station

LENGTH OF PROJECT

R e m o v e a n d

R e p la c e P a v e m e n t p w w o r k in g

\c e n tr a l0

\d

\T

Y P

S

D G

F P

.d g n

:2

N o v e m b e r

TYPICAL SECTION

PROJECT

NUMBER

SHEET

NORTH POINT PARKING LOT

A6

C P -3

C P -3

JB

S W -0

T P

JB

E M

S W -0

S W -0

JB

T

T

Edge of pavement

Edge of pavement

Protect in place

Existing light pole and junction box box, Protect in place

Existing light pole and junction and pave

Remove grass island

4" solid white stripe (typ.)

and pave

Remove grass island

Missouri River

Curve BL_900-02

Protect in place

Existing trail

Curve BL_900-01

4" solid white stripe (typ.)

Limits of construction

Remove tree root ball prior to construction

Tree to be removed by others and pave

Remove grass island

Limits of construction

(t yp

' (ty p

V a r ie s

V a r ie s ty p

V a r ie s and pave

Remove grass island

Verify prior to beginning work

Estimated location of underground power

Protect in place

Underground power, Existing culvert, do not disturb

Edge of pavement

Edge of pavement

Protect in place

Existing light pole and junction box box, Protect in place

Existing light pole and junction and pave

Remove grass island

4" solid white stripe (typ.)

and pave

Remove grass island

Missouri River

Curve BL_900-02

Protect in place

Existing trail

Curve BL_900-01

4" solid white stripe (typ.)

Limits of construction

Remove tree root ball prior to construction

Tree to be removed by others and pave

Remove grass island

Limits of construction

(t yp

' (ty p

V a r ie s

V a r ie s ty p

V a r ie s and pave

Remove grass island

Verify prior to beginning work

Estimated location of underground power

Protect in place

Underground power, Existing culvert, do not disturb

3. Tree root ball removal is incidental to roadway excavation and not paid separately.

2. See sheets D3-D6 for points and point tables.

floodplain and is designed to a 0-inch raise.

1. Verify horizontal and vertical alignment prior to the start of construction. Parking area is in a Zone A

NOTES:

N

25 50012.525

Scale in feet

P T

.3

Curve Data:

Curve BL_900-01 Curve BL_900-02

PI 902+68.42

Δ = 05°16'17" (RT)

R = 1,000.00' T = 46.03' L = 92.00'

PI 905+12.15

Δ = 03°30'01" (RT)

R = 1,000.00' T = 30.56' L = 61.09'

P C

.6

P T

.6

P O

B

.0

N46°50'37"W N46°50'37"W N41°34'19"W

H P I

.0

BEGIN PROJECT

BEGIN ROADWAY CONSTRUCTION

SD FLAP SDGFP PARKING(1)

900+00.00 "BL_900"

N= 278509.1658 E= 2439775.8301 El.= 1368.62

BEGIN PROJECT

BEGIN ROADWAY CONSTRUCTION

SD FLAP SDGFP PARKING(1)

900+00.00 "BL_900"

N= 278509.1658 E= 2439775.8301 El.= 1368.62

B

L

P la n

-5 s c a le

S h e p w w o rk in g \c e n tr a l0

\d

\P

L N

(9 )S

D G

F P

.d g n

:4

N o v e m b e r

900+00 to 905+20

LOT PLAN SHEET

RTE 900 NORTH POINT PARKING

PROJECT

NUMBER

SHEET

NORTH POINT PARKING LOT

D1

C

JB

JB

C P -3

JB

P K

S W -0

P L U

G

IN

P L U

G O

U T

4" solid white stripe (typ.)

existing handrail

Remove and reset

Protect in place

Existing concrete boat ramp

Edge of pavement

Missouri River

Limits of construction

Curve BL_900-02

Curve BL_900-03

Protect in place

Existing gravel apron

Protect in place

Existing light pole and junction box

Protect in place

Existing junction box

Protect in place

Existing delineator

Remove and Install R7-1L

907+42

Remove and Install R7-1R

906+76

See Special 634-A

"Plug Out" Pavement Marking

907+50

See Special 634-A

"Plug In" Pavement Marking

907+50

V a r ie s

' (ty p ty p

(t yp

(t yp construction

Limits of

V a r ie s pavement

Edge of

See Special 634-A

Accessible Pavement marking (typ.)

spaces (2) for boat ramp

Existing accessible parking concrete pad, Protect in place

Existing vault toilet and

See Special 610-A

Install 8'x8' concrete dumpster pad

Verify prior to beginning work

Estimated location of underground power sidewalk existing

Tie in to

4" solid white stripe (typ.)

existing handrail

Remove and reset

Protect in place

Existing concrete boat ramp

Edge of pavement

Missouri River

Limits of construction

Curve BL_900-02

Curve BL_900-03

Protect in place

Existing gravel apron

Protect in place

Existing light pole and junction box

Protect in place

Existing junction box

Protect in place

Existing delineator

Remove and Install R7-1L

907+42

Remove and Install R7-1R

906+76

See Special 634-A

"Plug Out" Pavement Marking

907+50

See Special 634-A

"Plug In" Pavement Marking

907+50

V a r ie s

' (ty p ty p

(t yp

(t yp construction

Limits of

V a r ie s pavement

Edge of

See Special 634-A

Accessible Pavement marking (typ.)

spaces (2) for boat ramp

Existing accessible parking concrete pad, Protect in place

Existing vault toilet and

See Special 610-A

Install 8'x8' concrete dumpster pad

Verify prior to beginning work

Estimated location of underground power sidewalk existing

Tie in to

N

25 50012.525

Scale in feet

2. See sheets D3-D6 for points and point tables.

Parking area is in a Zone A floodplain and is designed to a 0-inch raise.

1. Verify horizontal and vertical alignment prior to the start of construction.

NOTES:

NO

PARKING

ANY

TIME

NO

PARKING

ANY

TIME

P O

E

.7

Curve Data:

Curve BL_900-03

PI 905+12.15

Δ = 03°30'01" (RT)

R = 1,000.00' T = 30.56' L = 61.09'

Curve BL_900-02

PI 907+70.49

Δ = 20°51'30" (RT)

R = 500.00' T = 92.03' L = 182.02'

P T

.6

P C

.4

N38°04'18"W

N17°12'48"W

H P I

.0

NO

PARKING

ANY

TIME

NO

PARKING

ANY

TIME

END PROJECT

END ROADWAY CONSTRUCTION

SD FLAP SDGP PARKING (1)

908+40.90 "BL_900"

N= 279147.8608 E= 2439237.8576 El.= 1366.03

END PROJECT

END ROADWAY CONSTRUCTION

SD FLAP SDGP PARKING (1)

908+40.90 "BL_900"

N= 279147.8608 E= 2439237.8576 El.= 1366.03

B

L

P la n

-5 s c a le

S h e p w w o rk in g \c e n tr a l0

\d

\P

L N

(9 )S

D G

F P

.d g n

:4

N o v e m b e r

905+20 to 908+40.90

LOT PLAN SHEET

RTE 900 NORTH POINT PARKING

PROJECT

NUMBER

SHEET

NORTH POINT PARKING LOT

D2

National Flood Hazard Layer FIRMette

0 500 1,000 1,500 2,000250 Feet

Ü

SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT

SPECIAL FLOOD

HAZARD AREAS

Without Base Flood Elevation (BFE) Zone A, V, A99

With BFE or Depth Zone AE, AO, AH, VE, AR

Regulatory Floodway

0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mile Zone X

Future Conditions 1% Annual Chance Flood Hazard Zone X

Area with Reduced Flood Risk due to Levee. See Notes. Zone X

Area with Flood Risk due to Levee Zone D

NO SCREEN Area of Minimal Flood Hazard Zone X

Area of Undetermined Flood Hazard Zone D

Channel, Culvert, or Storm Sewer

Levee, Dike, or Floodwall

Cross Sections with 1% Annual Chance

17.5 Water Surface Elevation

Coastal Transect

Coastal Transect Baseline Profile Baseline Hydrographic Feature

Base Flood Elevation Line (BFE)

Effective LOMRs

Limit of Study Jurisdiction Boundary

Digital Data Available

No Digital Data Available

Unmapped

This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.

The basemap shown complies with FEMA's basemap accuracy standards

The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 11/5/2025 at 11:00 PM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time.

This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes.

Legend

OTHER AREAS OF

FLOOD HAZARD

OTHER AREAS

GENERAL

STRUCTURES

OTHER

FEATURES

MAP PANELS

B 20.2

The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location.

1:6,000

98°34'30"W 43°5'17"N

98°33'53"W 43°4'51"N

Basemap Imagery Source: USGS National Map 2023

Project

Finseth, Amy

From: Kotab, Michael <Miko@tntwagner.com>

Sent: Thursday, November 6, 2025 2:59 PM

To: Finseth, Amy

Cc: Flick, Mike; matthew.steiner@dot.gov

Subject: RE: Proposed parking lot work at North Point Boat Ramp

CAUTION: [EXTERNAL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Amy, Since it’s primarily a replacement of existing surfacing and no significant fill is being added, there are no permits or county approval required.

Mike Kotab EM Director Charles Mix County 605.491.3134 mkotab@charlesmixcounty.gov miko@tntwagner.com

Confidentiality Notice: This email message, including any attachments, is for the sole use of the intended recipients and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message and any attachment(s). Thank you.

From: Finseth, Amy <Amy.Finseth@hdrinc.com>

Sent: Wednesday, November 5, 2025 5:56 PM

To: Kotab, Michael <Miko@tntwagner.com>

Cc: Flick, Mike <mike.flick@hdrinc.com>; matthew.steiner@dot.gov

Subject: RE: Proposed parking lot work at North Point Boat Ramp

Great! Thanks for the quick response.

Project description:

• The project proposes to replace the pavement in the North Point Boat Ramp Parking Lot and will remove the pavement and base in the parking area and replace both with new aggregate and asphalt.

• One ADA parking space will be added and striped accordingly, the ADA spot will not be on a concrete pad.

• Four existing grass median areas in the parking lot, currently function as overflow parking when the parking area is full. Pavement will be extend through these areas.

• New signs and pavement markings will be added.

• There are no existing culverts and the parking area surface drains.

I have attached a site map, typical section where you will see the paving will match existing grade, proposed layout plans and a firmette of the floodplain limits.

Could you provide us with any requirements you have for your local floodplain management or if you need any additional documentation of the work.

Let me know if you have any questions – thank you again for your help.

Amy Finseth

O [303.323.9800] M [720.226.5554]

From: Kotab, Michael <Miko@tntwagner.com>

Sent: Wednesday, November 5, 2025 4:09 PM

To: Finseth, Amy <Amy.Finseth@hdrinc.com>

Subject: RE: Proposed parking lot work at North Point Boat Ramp

CAUTION: [EXTERNAL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Hello Amy, I am the flood Plain Manager for Charles Mix County so you have the right person.

Mike Kotab EM Director Charles Mix County 605.491.3134 mkotab@charlesmixcounty.gov miko@tntwagner.com

Confidentiality Notice: This email message, including any attachments, is for the sole use of the intended recipients and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message and any attachment(s). Thank you.

From: Finseth, Amy <Amy.Finseth@hdrinc.com>

Sent: Wednesday, November 5, 2025 5:08 PM

To: Kotab, Michael <Miko@tntwagner.com>

Subject: Proposed parking lot work at North Point Boat Ramp

Hello Mike, I am with HDR, an engineering consultant on behalf of the Federal Highway Administration. We are working with the park at North Point Recreational Area on plans to replace the parking lot pavement. The work area is located within a Zone A floodplain and I am trying to contact the local floodplain administrator to identify any local requirements you may have regarding working in a Zone A. Can you help me connect with the correct person and I can provide more information on the work.

Appreciate your help.

Sincerely, Amy Finseth

Transportation Hydraulics Senior Designer/Project Manager

HDR

1670 Broadway, Suite 3400 Denver, CO 80202 O [303.323.9800] M [720.226.5554] Amy.Finseth@hdrinc.com hdrinc.com/follow-us