Memorandum - Nixa

Memorandum

Neighbors committed to an exceptional quality of life

www.nixa.com

To: Mayor

City Council

From: Travis Cossey

Re: Wasson Commercial Ph. 4 Preliminary Plat

Date: September 28, 2020

Mr. Jay Wasson, on behalf of the Wasson Family Limited Partnership, has submitted a

Preliminary Plat for Wasson Commercial Development Phase 4. The subject property is a

continuation of the commercial development currently under construction adjacent to

Hwy. 160. Phase 4 is an 11.31-acre tract of land located on Old Wilderness Road, South

of Northview Road and North of Aven Road. The Preliminary Plat has 6 total lots, 5 are

buildable lots. Lot 10 is common area that is dedicated to the property owner’s

association for the commercial development.

Page 1 of 2

RESOLUTION NO. 2020-093

A RESOLUTION OF THE COUNCIL OF THE CITY OF NIXA APPROVING THE PRELIMINARY PLAT FOR WASSON COMMERCIAL DEVELOPMENT, PHASE 4.

_________________________

WHEREAS, an application has been received requesting the City’s approval of a Preliminary Plat for Wasson Commercial Development, Phase 4; and

WHEREAS, after public hearing and review of said Preliminary Plat the City Council finds that the application is in conformance with all applicable review criteria; and

WHEREAS, having found that the application for approval of a Preliminary Plat

for Wasson Commercial Development, Phase 4, is in conformance with all applicable review criteria, the City Council desires to approve of said application.

NOW THEREFORE, BE IT RESOLVED BY THE COUNCIL OF THE CITY OF NIXA, AS FOLLOWS, THAT:

SECTION 1: The City Council hereby finds that the proposed Preliminary Plat for Wasson Commercial Development, Phase 4, is in conformance with the City’s adopted review criteria. Therefore, the City Council approves the application for approval of a preliminary plat, subject to the conditions identified in the Planning and Zoning Commission’s Resolution, attached hereto and incorporated herein as “Exhibit A.”

SECTION 2: This Ordinance shall be in full force and effect from and after its final passage by the City Council and after its approval by the Mayor, subject to the provisions of section 3.11(g) of the City Charter.

ADOPTED BY THE COUNCIL OF THE CITY OF NIXA THIS 28TH DAY OF SEPTEMBER 2020.

__________________________ PRESIDING OFFICER

ATTEST: _______________________ CITY CLERK

Page 2 of 2

APPROVED BY THE MAYOR THIS _____ DAY OF ________________ 2020. __________________________ MAYOR ATTEST: _______________________ CITY CLERK APPROVED AS TO FORM: _______________________ CITY ATTORNEY

nwoodman

Text Box

Exhibit A

SINKHOLE EVALUATION

WITH LIMITED SUBSURFACE INVESTIGATION

FOR

WASSON COMMERCIAL PHASE 2 DEVELOPMENT SE CORNER NORTHVIEW RD. & OLD WILDERNESS RD.

NIXA, MISSOURI

Prepared for:

Wasson Family Limited Partnership 7002 Calabash St. Nixa, MO 65714

Prepared by:

• Geotechnical Services

• Environmental Services

• Material Testing Services

Springfield, MO 4168 W. Kearney Springfield, MO 65803

Call 417.864.6000 Fax 417.864.6004 www.ppimo.com

PPI PROJECT NUMBER: 259692

November 26, 2019

Page ii

TABLE OF CONTENTS

1.0 INTRODUCTION .................................................................................................. 3 2.0 SITE INVESTIGATION ......................................................................................... 3 3.0 SITE DESCRIPTION ............................................................................................ 4

3.1 General Geology and Soils ............................................................................. 4 3.2 General Hydrogeology .................................................................................... 5

3.3 Site Geomorphology ....................................................................................... 6 3.4 Land Cover ...................................................................................................... 6

4.0 FLOODING EVALUATION ................................................................................... 8 5.0 CONCLUSIONS & RECOMMENDATIONS .......................................................... 8

APPENDICES APPENDIX I – FIGURES APPENDIX II – PHOTOGRAPHS APPENDIX III – BORING LOGS APPENDIX IV – SECTION 90 FROM NIXA TECHNICAL SPECIFICATION

MANUAL

Sinkhole Evaluation Wasson Commercial Phase 2 Development

November 26, 2019 Page 3 PPI Project No. 259692

1.0 INTRODUCTION

Palmerton & Parrish, Inc. (PPI) was retained to perform a sinkhole evaluation for the

vacant property known as Wasson Commercial Phase 2 Development located at the

southeast corner of Northview Road and N. Old Wilderness Road in Nixa, Missouri. The

results of that evaluation are presented in the following pages. The subject property is

generally located in the SW ¼ of the SE ¼ of section 11 and the NW ¼ of the NE ¼ of

section 14, township 27 north, range 22 west in Nixa, Christian County, Missouri. This

sinkhole evaluation was performed according to Section 90 - Sinkholes and Karst

Features from the City of Nixa Technical Specification Manual (Section 90). See Figure

1 in Appendix I for the general location of the subject property on the Nixa 7.5 Minute

Topographic Quadrangle. The property is currently covered with grass and some light

woodland. According to the Christian County public GIS map viewer, no sinkholes have

been identified on the subject property by the County.

An initial Sinkhole Evaluation was performed for the subject property with a report issued

on July 29, 2019.

2.0 INITIAL SITE INVESTIGATION

The following public records were reviewed in the course of this evaluation:

• Nixa 7.5 Minute Topographic Quadrangle, 1975, United States Geological Survey

• Soil Survey of Christian County, Missouri, 1985, United States Department of

Agriculture

• Porter, J., Thomson, K.C., 1975, Geology, Geomorphology, and Karst

Development in the Nixa Karst Area, Southwestern Missouri, Southwest Missouri

State University, Department of Geography and Geology, Springfield, MO

• Geologic Map of Missouri, 2003, Missouri Department of Natural Resources,

Geological Survey Program

• Miller D. E. and Vandike, J. E., 1997, Groundwater Resources of Missouri:

Missouri Department of Natural Resources State Water Plan Series, Volume II,

Missouri Department of Natural Resources, Rolla, Missouri



• GeoSTRAT Sinkhole Points, GIS Data Layer for Google Earth, 2014, Missouri

Department of Natural Resources, Missouri Geological Survey, Rolla, Missouri

• Christian County Assessor, Public GIS Map Viewer

• U.S. Geological Survey, 1959 & 1979 Historical Aerial Photographs

None of these public records identified sinkholes on the subject property. Mr. Travis

Cossey, the Director of Planning and Development for the City of Nixa, was contacted to

see if the City had any records of sinkholes on the subject property. Mr. Cossey was not

aware of any previous studies on the property. Mr. Cossey was aware of the presence of

two (2) collapse sinkholes on the property (S2 and S3), which are discussed below.

A topographic map of the subject property, prepared by Shaffer & Hines, Inc., was

provided to PPI. Additionally, a topographic map was generated using LiDAR elevation

data collected in Christian County. These topographic maps were used to assist in

identifying potential sinkhole areas.

The subject property was initially visited on July 17, 2019 to visually observe any

sinkholes or other karst features that may exist on the site. At that time four (4) collapse

sinkholes, one (1) possible sinkhole, and one (1) suspect area were observed on the

subject property. The location of these features can be viewed on Figure 2 in Appendix I.

A subsurface investigation was performed on October 1, 2019 to determine methods to

stabilize the collapse sinkholes and to determine the nature of the possible sinkhole.

Additional subsurface investigation was performed on November 20, 2019 to determine

the nature of the suspect area in the southeast portion of the project area. Details of the

subsurface investigation are presented in Section 5.0 of this report.

3.0 SITE DESCRIPTION

3.1 General Geology and Soils

Bedrock underlying the subject property consists of the Mississippian age Burlington-

Keokuk formation, a coarsely crystalline limestone containing minor amounts of

interbedded chert. The Burlington-Keokuk limestone crops out extensively in the

general area of the site property. Weathering of the formation produces a rough,



irregular, and broken surface. Deep weathering along vertical fractures creates

features described as cutters and pinnacles, a highly irregular interface between the

soil horizon and the bedrock. The Burlington-Keokuk limestone is extremely

susceptible to dissolution and development of karst features. Numerous sinkholes

are present in the uplands underlain by the formation. The nearest known fault to the

subject property is Sac River fault located approximately 0.25 mile to the southwest.

Fracture trends in the area of the subject property generally trend northeast-southwest

and northwest-southeast. No known caves or springs are located within a mile of the

subject property.

According to the Missouri Department of Natural Resources, Geological Survey

Program, Environmental Geology Section, no dye traces have been performed in the

area of the subject property. Water entering sinkholes on the property will likely

eventually discharge at springs along the James and Finley Rivers.

Soils overlying the Burlington-Keokuk formation consist of cherty residuum typically

classified as CL or CH according to the Unified Soil Classification System.

3.2 General Hydrogeology

The site is located in the Springfield Plateau groundwater province. Hydrogeologic

units in the site area from the uppermost to lowermost include the Springfield Plateau

aquifer, Ozark confining unit, and the Ozark aquifer. In the site area the Springfield

Plateau aquifer consists of the Mississippian age Burlington-Keokuk formation, Elsey-

Reeds Spring formations, and Pierson limestone. The Springfield Plateau aquifer is

an unconfined aquifer recharged by precipitation. Underlying the Springfield Plateau

aquifer is the Ozark confining unit, a series of Mississippian age low-permeability

formations that greatly restrict the vertical movement of water. The Ozark confining

unit consists of the Northview formation, the Compton limestone, and locally the

Pierson limestone. Underlying the Ozark confining unit is the Ozark aquifer, which is

a confined aquifer consisting of Cambrian and Ordovician age dolomites and

sandstones. This aquifer is the most prolific aquifer in southwest Missouri and is the

source of potable groundwater for most domestic and public water supplies outside of

the City of Springfield, including the City of Nixa. Because of the sensitivity of the



Springfield Plateau aquifer to surface contamination sources, the State of Missouri

has prohibited the construction of water wells into the aquifer in Greene and northern

Christian counties. According to 10 CSR 23-3.100 water wells constructed in Sensitive

Area C shall be drilled and cased through the Springfield Plateau aquifer and Ozark

confining unit and be completed in the Ozark aquifer. No water wells were observed

at the subject property.

3.3 Site Geomorphology

The subject property is located within the Springfield Plateau subprovince of the Ozark

Plateaus physiographic province. The landscape is characterized by rolling hills,

meandering streams, and karst features such as sinkholes, caves, and springs.

The surveyed area on the subject property has a total relief of approximately 25 feet,

with the lowest elevation of approximately 1262 feet in the floor of sinkhole S5 and the

highest elevation of approximately 1287 feet in the extreme southwest corner of the

property. Runoff on the subject property generally flows to the west central portion of

the property where it exits onto the west adjacent property.

3.4 Land Cover

Currently the ground surface of the property is covered with grasses with some light

woodland. Two of the woodland areas have grown up on piles of soil fill.

4.0 LIMITED SUBSURFACE INVESTIGATION

Five (5) subsurface borings were drilled at the subject property to determine the soil

characteristics and to collect data for use in developing a conceptual plan to stabilize the

collapse sinkholes. The approximate soil boring locations can be viewed on Figures 3

and 4 in Appendix I. Prior to drill-rig mobilization, the Missouri One-Call System was

notified by PPI to assist in locating buried public utilities. All soil borings were drilled using

4.5-inch O.D. continuous flight augers powered by a CME 55 track-mounted drill-rig. Soil

sample locations were collected at the discretion of a geologist in the field. Soil samples

were collected using a split spoon sampler while performing the Standard Penetration

Test (SPT) in general accordance with ASTM D1586.



Soil boring 1 was drilled 6 feet south of collapse sinkhole S1. Soils encountered in the

boring consisted of a thick layer of brown to reddish brown lean clay overlying cherty red

clay residuum. From approximately 30 feet to auger refusal on bedrock at 34.8 feet, was

a lean brown clay. Within this interval above the bedrock the boring likely intersected the

soil piping conduit that produced the collapse sinkhole.

Soil boring 2 was drilled near the center of a suspected large solution sinkhole and near

two (2) collapse sinkholes. Soils encountered in the boring generally consisted of lean

clays with very little chert with mixed colors of brown, gray, and reddish brown to a depth

of approximately 31.8 feet. From approximately 31.8 feet to 37.5 feet, where auger refusal

on bedrock occurred, was cherty red clay residuum. Groundwater was observed at 25

feet in depth during drilling. The soils from the surface to approximately 31.8 feet are

indicative of soils found in the floor of solution sinkholes.

Soil boring 3 was drilled 5 feet north of collapse sinkhole S3. Soils encountered in the

boring consisted of a thin layer of brown lean clay overlying cherty red clay residuum.

Auger refusal on bedrock occurred at 21.3 feet.

Soil borings 4 and 5 were drilled on the south and north sides of a depression located on

the eastern property boundary. At this location is a depression that is open on the east

side. Due to reports of past land disturbance in this area it is impossible from surface

observation alone to determine if this depression occurs from natural processes or the

activities of man. Soils encountered in the borings generally consisted of approximately

3 feet of lean clay fill overlying cherty red clay residuum. Auger refusal on bedrock

occurred at depths of 40.5 feet and 35.5 feet for borings 4 and 5, respectively. No

evidence of a karst feature was observed in the soil borings and it is likely that this open

depression is man-made.

Auger refusal is defined as the depth below the ground surface at which a boring can no

longer be advanced with the soil drilling technique being used. Auger refusal is subjective

and is based upon the type of drilling equipment and types of augers being used, as well

as the effort exerted by the driller. Several different auger refusal conditions are possible

in the general site area. These conditions are represented graphically in the adjacent

figure: (A) on the upper surface of continuous bedrock, (B) on rock “pinnacles”, (C) in



widened joints that may extend well below the

surrounding bedrock surface, (D) slabs of

unweathered rock suspended in the residual

soil matrix, or “floaters”, or (E) on the upper

surface of discontinuous bedrock.

Boring logs with stratum depths and

descriptions along with general notes

regarding boring logs are presented in

Appendix III.

5.0 FLOODING EVALUATION

A quantitative analysis of the potential for sinkhole flooding was not performed during this

evaluation. The collapse sinkholes on the site have very little stormwater storage

capacity. Sinkhole S5 is open to the drainage channel running along its south edge.

Stormwater analysis of the entire site will be performed by the project civil engineer at a

later date.

6.0 FINDINGS & CONCLUSIONS

Collapse sinkhole S1 is generally located in the northwest portion of the subject property.

At the surface this sinkhole is approximately 7 feet long, 4 feet wide, and 2 feet deep. A

review of historical aerial photographs on Google Earth indicate that the ground surface

collapse at this sinkhole occurred between February 2017 and March 2019. Boring 1,

performed to the south of the collapse, indicates that the soil piping conduit that produced

the sinkhole is to the south of the surface collapse. Bedrock was encountered in the boring

relatively deep at 35.3 feet.



Collapse sinkhole S2 is generally located in the west central portion of the subject

property. At the surface this sinkhole is approximately 5 feet in diameter and 5 feet deep.

A review of historical aerial photographs on Google Earth indicate that the ground surface

collapse at this sinkhole occurred between April 2013 and March 2015. This collapse

sinkhole formed in the floor of solution sinkhole S5 described below.

Collapse sinkhole S3 is generally located in the west central portion of the subject

property. At the surface this sinkhole is approximately 30 feet long, 20 feet wide, and 6

feet deep. A review of historical aerial photographs on Google Earth indicate that the

ground surface collapse at this sinkhole occurred between October 2011 and March

2013. This collapse sinkhole formed in the floor of solution sinkhole S5 described below.

Collapse sinkhole S4 is generally located in the center of the subject property. At the

surface this sinkhole is approximately 14 feet long, 5 feet wide, and 3 feet deep. A review

of historical aerial photographs on Google Earth indicate that the ground surface collapse

at this sinkhole occurred between September 2010 and October 2011. Soil boring 3,

performed to the north of the collapse, encountered bedrock at 21.3’.

Collapse sinkholes form through a process called raveling erosion dome progression and

roof collapse. Soil is transported through an opening in the underlying bedrock producing

a dome shaped cavity. Progressively this cavity moves upward as soil in the upper part

of the dome falls into the cavity and soil continues to be piped into the bedrock. When the

cavity reaches the surface the roof collapses forming a steep sided or bell-shaped hole.

This is illustrated in the following figure.

From Sowers G. F., Building on Sinkholes, ASCE Press, 1996



Sinkhole S5 is a solution sinkhole that encompasses collapse sinkholes S2 and S3.

Collapse sinkholes often occur in the floor of large solution sinkholes. PPIs initial

observations identified this area as a possible sinkhole. However, observations made

during the subsurface investigation described in Section 5.0 of this report indicate that

this area is a large solution sinkhole.

The open depression on the east boundary of the subject property is likely man-made.

No other karst features were observed on the subject property.

See Figure 2 in Appendix I for a topographic map of the site with sinkhole locations.

Figures 3 and 4 show the sinkholes and soil boring locations on a topographic map and

aerial photograph, respectively. Photographs of sinkholes S2 and S3 can be viewed in

Appendix II.

Based on the topographic map and visual observations, the sinkhole rim and sinkhole rim

setback for sinkhole S5 was defined and can be viewed in Figures 3 and 4.

There are two (2) areas where soil fill covers the natural ground surface. The location and

approximate extents of these soil piles is shown on Figure 4. Should future grading

uncover suspect soils or other suspect features underneath these soil piles, these areas

may need to be evaluated.

Construction of commercial structures within sinkholes and sinkhole closure are

conditionally permitted in Section 90. For construction of structures within sinkholes or

closed sinkholes a foundation design by an engineer is required. A copy of Section 90 is

included in Appendix IV of this report.

Water quality considerations were evaluated according to Section 90 - Sinkholes and

Karst Features from the City of Nixa Technical Specification Manual. Based on the

definitions in the section, commercial development of this property will likely pose a

moderate hazard for groundwater contamination depending on the amount of directly

connected impervious area discharging to sinkhole S5. Please review Section 90 for

water quality considerations and development requirements around sinkholes. A copy of

Section 90 in included in Appendix IV of this report.



Water infiltrating through the sinkholes will enter the Burlington-Keokuk formation and

upper part of the Springfield Plateau aquifer. It is unlikely, but possible that older water

wells completed in the Springfield Plateau aquifer are still actively being utilized. Current

and future wells are cased through the Springfield Plateau aquifer and completed in the

Ozark aquifer; the potential for contamination of area potable groundwater supplies is

low.

7.0 RECOMMENDATIONS

PPI recommends that collapse sinkholes S1 and S4 be stabilized using techniques

approved by the City of Nixa. These collapse sinkholes appeared relatively recently and

are likely to experience additional soil subsidence in the future. Specific recommendations

for collapse sinkhole stabilization are presented below.

Because collapse sinkholes S2 and S3 are in the floor of solution sinkhole S5 it may not

be technically or economically feasible to remediate due to depth to bedrock. Because no

structures should be constructed within sinkhole S5, collapse sinkholes S2 and S3 can

be filled in with soil to remove the immediate hazard they pose. Please note that after

filling these collapse sinkholes they may continue to be active in the future. Additionally,

new collapse sinkholes may form that will require filling. Filling and refilling of collapses

in the floor of this solution sinkhole may be required indefinitely.

7.1 Collapse Sinkhole Stabilization

Collapse sinkholes S1 and S4 can likely be stabilized by excavating the loose soils to

bedrock and installing a graded filter according to common practice in the Nixa and

Christian County area. While the depth to bedrock is relatively deep, especially at S1,

there are no existing structures or underground utilities nearby that would prevent the

excavation of a ramp or bench to reach bedrock. The following diagram is a schematic

section showing the construction of a graded filter.



Please note that the actual construction of the graded filter may be modified based on the

conditions encountered. The most common modification is using larger stone in and on

top of the bedrock.

Should excavation and construction of a graded filter become impractical, a reinforced

concrete mat bearing on stable soils can be constructed over the collapse area. This

generally consists of the following:

• Proper excavation and backfilling of the sinkhole affected area using rock fill;

• Excavating around the sinkhole affected area a minimum of 4 ft. beyond the edge

of sinkhole in-wash soils;

• Construction of a structural, reinforced concrete mat, spanning the extents of the

collapsed shaft, with a minimum of 4 horizontal feet of adequate bearing on all

sides;



• Installation of PVC pipes within the structural mat (within the area of the collapse)

to provide drainage through the mat (both downward and upward), and installation

of filter fabric squares on top of the pipes; and

• Construction of a graded rock filter on top of the structural mat, with proper

placement and compaction of the rock backfill, and installation of filter fabric as

specified.

Should a reinforced concrete mat bearing on stable soils become the necessary

stabilization method for either collapse sinkhole, PPI can provide specific plans to allow

the Client to seek cost estimates.

8.0 CLOSURE

This evaluation was performed using visual observation, a site topographic survey, five

(5) soil borings, and the government and public records summarized in Section 2.0. No

geophysical methods, or other methods were employed to characterize the subsurface

conditions at the site property. We have employed accepted engineering geologic and

hydrogeologic procedures, and our opinions and conclusions are made in accordance

with generally accepted principles and practices of these professions. The contents of

this report are valid as of the date of preparation. However, changes in the condition of

the site property can occur over time as a result of either natural processes or human

activity. Should such changes occur, it might be necessary to re-evaluate some of the

opinions and conclusions of this report.

11/26/19

Donald Nowack, P.E., R.G. Date

APPENDIX I

FIGURES

PALMERTON & PARRISH, INC. FIGURE 1

DATE: November 26, 2019 Project Number: 259692

Site Location on USGS Topographic Map

Project: Wasson Commercial Phase 2 Development, Nixa, MO

Client: Wasson Family Limited Partnership

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GEOTECHNICAL AND MATERIALS ENGINEERS/MATERIALS TESTING LABORATORIES/ENVIRONMENTAL SERVICES

AutoCAD SHX Text

SITE LOCATION



Site Topographic Map of Site with Sinkholes



1" = 250'

SCALE

S1

S2

S3

S4

Sinkhole S5

AutoCAD SHX Text


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Sinkhole Areas & Borings on Topographic Map



1" = 120'

LEGEND

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S2

S3

10' Building Setback

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APPENDIX II

PHOTOGRAPHS

Photograph #1

Taken By: D. Nowack

Date: July 17, 2019

Collapse sinkhole S2.

Photograph #2

Taken By: D. Nowack

Date: July 17, 2019

Collapse sinkhole S3.

Wasson Commercial Phase 2 Development, Nixa, MO

APPENDIX III

BORING LOGS

SPT1

SPT2

SPT3

SPT4

SPT5

0.5 ft

6.0 ft

20.0 ft

30.0 ft

34.8 ft35.3 ft

CF

A -

4.5

" O

.D.

4-4-3(7)

3-4-3(7)

7-10-12(22)

4-1-12(13)

74/1"

SURFACE ELEVATIONDATE STARTED 10/1/19 COMPLETED 10/1/19

DRILL RIG 2005 CME 55

HAMMER TYPE Auto

LOGGED BY CS CHECKED BY TA

DRILLER CW

AT END OF DRILLING

NOTES

GROUND WATER LEVELS

AT TIME OF DRILLING None

BENCHMARK EL.

DR

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H(f

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DRY UNIT WT (pcf) 20 40 60 80 100

N VALUE 20 40 60 80

SHEAR STRENGTH (ksf) 1 2 3 4

20 40 60 80

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GEOTECHNICALBORING LOG

PAGE 1 OF 1

BORING NUMBER

1

PROJECT LOCATION Nixa, Missouri

PROJECT NAME Sinkhole InvestigationCLIENT Wasson Family Limited Partnership

PROJECT NO. 259692

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4168 W. Kearney St.Springfield, Missouri 65803Telephone: (417) 864-6000Fax: (417) 864-6004

TOPSOIL, Grass Covered (6")

LEAN CLAY, Brown, Medium Stiff, Moist (CL)

LEAN CLAY, Trace Chert, Reddish Brown, MediumStiff, Moist (CL)

FAT CLAY, Trace Chert, Red, Stiff, Moist (CH)

LEAN CLAY, Trace Chert, Brown, Stiff, Moist (CL)

LIMESTONE, Weathered, Medium Hard

Refusal at 35.3 feet.Bottom of borehole at 35.3 feet.

MATERIAL DESCRIPTION

Unified Soil Classification System

SPT1

SPT2

SPT3

SPT4

SPT5

SPT6

SPT7

SPT8

0.5 ft

2.5 ft

11.8 ft

16.8 ft

24.1 ft

31.8 ft

37.5 ft38.0 ft

CF

A -

4.5

" O

.D.

1-4-3(7)

9-19-18(37)

6-7-7(14)

4-6-6(12)

7-9-10(19)

9-10-12(22)

4-7-19(26)

1-1-1(2)



HAMMER TYPE Auto

LOGGED BY TA CHECKED BY TA

DRILLER CW

AT END OF DRILLING

NOTES

GROUND WATER LEVELS

AT TIME OF DRILLING 25 ft

BENCHMARK EL.

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DRY UNIT WT (pcf) 20 40 60 80 100

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PAGE 1 OF 1

BORING NUMBER

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PROJECT NO. 259692

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TOPSOIL, Grass Covered (6")

LEAN CLAY, Brown, Medium Stiff, Moist (CL)

LEAN CLAY, Grayish Brown, Very Stiff, Moist, Silty(CL)

LEAN CLAY, Trace to No Chert Gravel, ReddishBrown, Stiff, Moist (CL)

LEAN CLAY, Trace to No Chert Gravel, Brown, Gray& Tan, Stiff, Moist, Silty (CL)

- Very Moist Below 24.8'

LEAN CLAY, Scattered Chert, Reddish Brown &Black, Very Stiff, Moist (CL)

- Reddish Brown & w/ Chert Below 28.5'

FAT CLAY, Trace Chert, Red, Soft, Very Moist (CH)





SPT1

SPT2

6.0 ft

21.3 ft

22.3 ft

CF

A -

4.5

" O

.D.

3-9-6(15)

3-4-4(8)



HAMMER TYPE Auto

LOGGED BY CS CHECKED BY TA

DRILLER CW

AT END OF DRILLING

NOTES

GROUND WATER LEVELS


BENCHMARK EL.

DR

ILLI

NG

ME

TH

OD

DE

PT

H(f

t)

0

5

10

15

20

ELE

VA

TIO

N(f

t)

ST

RA

TA

SY

MB

OL

DRY UNIT WT (pcf) 20 40 60 80 100

N VALUE 20 40 60 80


20 40 60 80

PL LLMC

PO

CK

ET

PE

N.

(tsf

)

SA

MP

LE T

YP

EN

UM

BE

R

CO

RR

EC

TE

DB

LOW

CO

UN

TS

(N V

ALU

E)

RE

CO

VE

RY

%(R

QD

%)


PAGE 1 OF 1

BORING NUMBER

3



PROJECT NO. 259692

BO

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LEAN CLAY, w/ Chert, Brown, Stiff, Moist, GrassCovered (CL)

FAT CLAY, Trace to Scattered Chert, Red, MediumStiff, Moist (CH)





SPT1

SPT2

SPT3

3.0 ft

40.5 ft40.6 ft

CF

A -

4.5

" O

.D.

4-4-4(8)

4-6-13(19)

6-4-8(12)


DRILL RIG D-50

HAMMER TYPE Auto

LOGGED BY RD CHECKED BY DN

DRILLER EP

AT END OF DRILLING

NOTES

GROUND WATER LEVELS


BENCHMARK EL.

DR

ILLI

NG

ME

TH

OD

DE

PT

H(f

t)

0

5

10

15

20

25

30

35

40

ELE

VA

TIO

N(f

t)

ST

RA

TA

SY

MB

OL

DRY UNIT WT (pcf) 20 40 60 80 100

N VALUE 20 40 60 80


20 40 60 80

PL LLMC

PO

CK

ET

PE

N.

(tsf

)

SA

MP

LE T

YP

EN

UM

BE

R

CO

RR

EC

TE

DB

LOW

CO

UN

TS

(N V

ALU

E)

RE

CO

VE

RY

%(R

QD

%)




PROJECT NO. 259692

BO

RIN

G L

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- P

PI -

PP

I ST

D T

EM

PLA

TE

.GD

T -

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5969

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LEAN CLAY, Trace Chert, Brown, Medium Stiff, Moist(CL)

FAT CLAY, Scattered Chert, Red, Stiff, Moist (CH)

- Wet Below 30'

LIMESTONE, Weathered, Medium HardRefusal at 40.6 feet.

Bottom of borehole at 40.6 feet.



PAGE 1 OF 1

4BORING NUMBER

SPT1

SPT2

3.0 ft

35.5 ft35.6 ft

CF

A -

4.5

" O

.D.

5-6-9(15)

6-6-10(16)


DRILL RIG D-50

HAMMER TYPE Auto

LOGGED BY RD CHECKED BY DN

DRILLER EP

AT END OF DRILLING

NOTES

GROUND WATER LEVELS


BENCHMARK EL.

DR

ILLI

NG

ME

TH

OD

DE

PT

H(f

t)

0

5

10

15

20

25

30

35

ELE

VA

TIO

N(f

t)

ST

RA

TA

SY

MB

OL

DRY UNIT WT (pcf) 20 40 60 80 100

N VALUE 20 40 60 80


20 40 60 80

PL LLMC

PO

CK

ET

PE

N.

(tsf

)

SA

MP

LE T

YP

EN

UM

BE

R

CO

RR

EC

TE

DB

LOW

CO

UN

TS

(N V

ALU

E)

RE

CO

VE

RY

%(R

QD

%)


PAGE 1 OF 1

BORING NUMBER

5



PROJECT NO. 259692

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G L

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FILL - LEAN CLAY, Trace Chert, Brown, Medium Stiff,Moist (CL)

FAT CLAY, Scattered Chert, Red, Stiff, Moist (CH)

- Wet Below 30'

LIMESTONE, Weathered, Medium HardRefusal at 35.6 feet.

Bottom of borehole at 35.6 feet.




PROJECT NO. 259692

ABBREVIATIONSTVPIDUCppm

----

TORVANEPHOTOIONIZATION DETECTORUNCONFINED COMPRESSIONPARTS PER MILLION

LIQUID LIMIT (%)PLASTIC INDEX (%)MOISTURE CONTENT (%)DRY DENSITY (PCF)NON PLASTICPERCENT PASSING NO. 200 SIEVEPOCKET PENETROMETER (TSF)

LLPIWDDNP-200PP

-------

Standard Penetration Test

SAMPLER SYMBOLSLITHOLOGIC SYMBOLS(Unified Soil Classification System)

CH: USCS High Plasticity Clay

CL: USCS Low Plasticity Clay

CL-CH: USCS Low to High PlasticityClay

FILL: Fill (made ground)

TOPSOIL: Topsoil

WEATHERED LIMESTONE: WeatheredLimestone

WELL CONSTRUCTION SYMBOLS

KEY TO SYMBOLS

Water Level at TimeDrilling, or as Shown

Water Level After 24Hours, or as Shown

Water Level at End ofDrilling, or as Shown


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J4168 W. Kearney St.Springfield, Missouri 65803Telephone: (417) 864-6000Fax: (417) 864-6004

APPENDIX IV

SECTION 90 FROM NIXA TECHNICAL SPECIFICATION MANUAL

123

PART II - EFFECTS OF DRAINAGE ON NATURAL FEATURES

Section-90. Sinkholes and Karst Features

A. GENERAL: The City of Nixa is located on the Springfield Plateau of the Ozarks

physiographic region. This area is underlain by Mississippian Age limestone which is highly susceptible to solution weathering. As a result, sinkholes, springs and caves are common.

Nixa sets on a broad upland area that serves as the drainage divide between the

James and Finely Rivers. A karst plain has developed on the relatively flat surface of the upland area within which surface runoff is drained internally to sinkholes; swallow holes, and losing streams. The sinkholes swallow holes, and losing streams feed a shallow subsurface drainage system which discharges at springs along the James and Finley Rivers.

In many areas of the City special consideration must be given to flood hazards and potential for ground water contamination due to the presence of sinkholes, caves, losing streams, springs, and other features associated with karst geology. The requirements set forth herein are intended to provide specific criteria for design and construction for any site upon which sinkholes or other karst features are located.

Interpretations of these requirements shall be made and appeals may be made according to the procedures set forth in Article VI of the Land Development Code.

B. DEFINITIONS: The following are terms used to interpret this portion of the Technical Specifications. The following definitions are related specifically to sink holes and sinkhole development.

Altered Sinkhole: A sinkhole which has been filled, excavated or otherwise disturbed. Collapse Sinkhole: A collapse sinkhole is a sinkhole that forms suddenly when surface soil collapses into a subsurface cavity. Collapse sinkholes typically originate at the bedrock surface and propagate upward to the ground surface. Heavy Equipment: Motorized equipment having a gross weight of more than 6 tons. Light Equipment: Motorized equipment weighing 6 tons or less. Losing Stream: A losing stream is a surface stream that loses a significant portion of its flow to an underground drainage system. Piracy Sinkhole: a piracy sinkhole is a sinkhole that has captured the normal flow

124

of a surface stream and diverted it to an underground drainage system. Qualified Geologist: A person who is licensed to practice geology in the State of Missouri; who has met or exceeded the minimum geological education requirements and who can interpret and apply geologic principles; and who by reason of experience and education has an understanding of local karst geology. Qualified Professional Engineer: A person who is licensed to practice engineering in the State of Missouri; who has met or exceeded the minimum engineering education requirements and can interpret and apply the fundamentals of storm drainage, soils engineering, and karst geology; and who by reason of experience and education has an understanding of local karst geology. Side Slope Sinkhole: A side slope sinkhole is a type of solution sinkhole which has formed on a sloped surface, but which has not subsided to the degree that a closed depression is formed. Side slope sinkholes are characterized by a localized flattening of the topography. Storm water drains naturally thru the open (downslope) side of the sinkhole. Sinkhole: A sinkhole, also known as a sink or doline, is a natural depression or hole in the surface topography caused by the removal of soil or bedrock by water. Sinkholes may vary in side from a few feet to several hundred feet both in diameter and depth, and vary in form from shallow bowl-shaped depressions to deep chasms. They may be formed gradually or suddenly, and are found around the world. Sinkhole Cluster Area: An area containing 2 or more sinkholes located in close proximity, generally interconnected by ground water conduits. 125 Sinkhole Eye: A sinkhole eye consists of a discrete hole, or shaft, within the floor or slope of a solution sinkhole that provides a conduit for drainage of storm water to the subsurface drainage system. Sinkhole Flooding Area: The area inundated by runoff from a storm with an annual exceedance probability of 1% and duration of 6 hours. Sinkhole Floor: The sinkhole floor consists of the flat or slightly convex surface at the bottom of a solution sinkhole. Sinkhole floors are typically covered with an accumulation of sediment or organic material. The edge, or limit, of the sinkhole floor is defined by the topographic break between the relatively flat floor and the sloped side wall of the sinkhole. Sinkhole Rim: The sinkhole rim constitutes the lateral limit of a sinkhole and is defined by the topographic break, or transition, between the natural ground surface and the sloped sinkhole wall. Sinkhole Slope: The sinkhole slope, or wall, consists of the inclined surface

125

between the sinkhole rim and the sinkhole floor. The sinkhole slope may be convex in its upper reaches and concave in its lower reaches. Sinkhole Watershed: The ground surface area that provides drainage to the sinkhole. This area extends beyond the sinkhole depression, and generally crosses property boundaries. Solution Sinkholes: A solution sinkhole is a sinkhole that forms by dissolution of soluble bedrock, such as limestone, dolomite, or gypsum Solution sinkholes typically occur as bowl-shaped depressions. Subsidence Sinkhole: A subsidence sinkhole is a sinkhole that occurs in areas of sandy, non-cohesive soils, and forms when surface soils migrate into subsurface cavities within the bedrock. Subsidence sinkholes are common in other parts of the nation, such as Florida. Swallow Hole: A swallow hole is a discrete sinkhole that forms in the floor of a stream channel and which captures a portion, or all, of the stream flow. Swallow holes are related to losing streams, but losing streams lack an identifiable point of water loss. Terminal Sinkhole: The lowest sinkholes in a sinkhole cluster to which any surface water overflowing from other sinkholes in the cluster will flow. Unaltered Sinkhole: A sinkhole which has never been altered or disturbed.

C. POLICY: In keeping with the intent of the Land Development Code the following policy is set forth for development in areas containing sinkholes:

Development in sinkhole areas will be based upon the following axioms:

1. Avoidance 2. Minimization 3. Mitigation

Construction in sinkholes should be avoided. Exceptions will be made only in situations where it can be conclusively demonstrated that there are no practical alternative to such construction.

These situations are most likely to arise where:

1. An underground cavity has caused a collapsed sinkhole to form, after

subdivision approval or building construction. 2. A sinkhole has been altered or filled either unknowingly or prior to passage of these regulations.

3. Maintenance and operation is required for existing roads and utilities. 4. Location of existing streets or utilities would render access or utility

126

service to property impractical or cost prohibitive. 5. It is demonstrated, subject to city approval, that sinkhole location renders the site undevelopable and economically unaffordable.

6. For road construction when it is demonstrated to the City’s satisfaction that movement of the roadway to avoid a sinkhole would conflict with the City’s traffic circulation plan and conflict with city adopted street standards.

In these types of cases, measures which will have minimal impact on the sinkhole or receiving water may be proposed. In circumstances where sinkhole closure is deemed necessary and appropriate to the site development plan sinkhole closure (filling) will be allowed with proper site investigation and design. Clean, engineered soil fill can satisfy the goals of development in sinkhole areas, in that it can actually improve the structural integrity of the site, simplify storm water management, and enhance groundwater quality protection, while opening up additional areas for development. Proposals for sinkhole closure shall be reviewed on case-by-case basis, with the burden of proof on the applicant.

D. GOALS FOR DEVELOPMENT IN SINKHOLE AREAS: There are four basic goals for development in sinkhole areas; assurance of structural integrity, maintenance of the storm water drainage system, protection of groundwater quality, and

sustainability. Each of these goals is discussed in the following: 1. Structural Integrity: Structures that are constructed in proximity to sinkholes should be required to have properly designed foundations. Lightly Loaded (residential) structures must maintain a 10’ setback from the sinkhole rim as determined by a qualified geologist. Heavier structures (commercial or industrial) may encroach into the sinkhole provided it has been filled in accordance with the regulations. In these circumstances construction of the building may require piers to bedrock. Foundation shall be designed by qualified professional engineer and the design documented to the City’s satisfaction.

2. Storm Water Management: There are two primary storm water concerns with respect to development in karst areas. The first concern is that the development does not cause a concentration of storm water in sinkholes (depth or duration of storage) beyond what would be expected in the pre-development condition, because increased saturation of soils can induce sinkhole collapses. This can be accomplished by diverting storm water inflow away from the sinkhole or draining storm water from the sinkhole more quickly, and ensuring that the natural permeability of the sinkhole floor is not compromised by construction equipment traffic. Diversion of storm water away from individual sinkholes does not have a significant impact on groundwater recharge since the diverted water typically flows to a losing stream or to another sinkhole. The second

127

concern is that the development does not cause an increase in flood elevations in post-development condition. This can be accomplished by excavation of additional storm water storage capacity within the sinkhole bowl or construction of external storm water detention basins.

3. Groundwater Protection: Much of the potential impact on groundwater quality occurs during construction. Best management practices (BMPs) must be instituted and maintained to prevent sediment or other deleterious materials from entering the sinkhole during the construction phase. Construction equipment should not be allowed within the sinkhole floor, since the inadvertent soil compaction caused by this equipment can reduce the natural permeability of the soil and reduce the ability of the sinkhole to drain. Developments should be designed to route urban runoff around or away from, sinkholes to the degree possible. This can be accomplished by construction of surface drainage swales or hard-piped storm water conveyance systems. Where storm water drainage to sinkholes concentrated bio-filtrations swales and bio-filtration strips may be bused to protect groundwater quality. Institutional controls (subdivision covenants, city ordinances) may also be required to preclude the introduction of pesticides, fertilizers, and other deleterious chemicals into sinkholes. Sinkhole eyes are very critical features for groundwater protection, since the sinkholes collect the storm water that falls within their drainage areas and the eyes allow unrestricted transfer of storm water to the karst drainage system. Sinkhole eyes can be modified to provide a measure of treatment by incorporating layer of sand (for filtrations) and peat moss (for absorption) into the design of a graded filter. 4. Sustainability: Development in sinkhole areas must provide permanent solutions to the issues of structural integrity, storm water management, and groundwater protection, and cannot create an ongoing maintenance issue or a source of liability for the developer, the homeowners association, or the City. E. PERMITS REQUIRED:

1. Grading Permit: A grading permit must be obtained prior to any alteration of

sinkholes associated with new subdivision construction in accordance with the Land Development Code. Procedures and requirements for grading permits are set forth in the “Design Standards and Criteria” Section (page 166).

F. GENERAL PLAN REQUIREMENTS: General requirements for grading and

drainage plans are set forth in the “Guidelines and Design” Section.

G. IDENTIFICATIONS AND INVESTIGATION OF SINKHOLES: Sinkholes can typically be identified on the basis of visual observation by qualified geologist. More detailed information on sinkhole structure can be obtained by soil borings, seismic surveys, and resistivity surveys. Ground penetrating radar (GPR) surveys are also useful but are somewhat limited by the clay soils in the area. Borehole

128

data is also useful in determining depth to bedrock, but can be misleading due to the highly variable nature of the bedrock surface. Light truck-and trailer-mounted drilling rigs can provide misleading data on depth to bedrock due to the presence of chert boulders in the soil column. In all cases, site investigation data should be evaluated and interpreted by a geologist registered in the State of Missouri.

Excavated farm ponds can often be mistaken for sinkholes, but can usually be

differentiated from sinkholes on the basis of soil borings. Soil cross sections through sinkholes will typically exhibit a sag in the soil profile resulting from subsidence, while soil cross sections through excavated farm ponds will not. Other conditions which can potentially form surface depressions that may be mistaken for sinkholes include:

1. Improper compactions of backfill 2. Buried compressible material 3. Decomposing organic material (such as a tree stump) 4. A failed septic tank, lateral field, or utility trench H. SINKHOLE EVALUATION: An evaluation including the following information

shall be made for all sites upon which sinkholes are fully or partially located.

The site plan for the proposed development must show the following items with respect to location of proposed construction, proposed or existing property lines; and existing structures

1. Sinkholes

a. Location and limits of the area of the sinkhole depression as determined by field surveys or other reliable sources as may be approved. Location of sinkholes based solely upon USGS 7-1/2 Minute Series Quadrangle Maps will not be considered sufficient unless field verified.

b. Location and elevation of the sinkhole eye where visible or known. c. Topographic contours at maximum intervals of one foot, and spot

elevations sufficient to determine the low point on the sinkhole rim and the profile of the potential overflow area.

d. Minimum entry elevations of any existing structures located within the

sinkhole rim. e. Elevation of any roadway located within or adjacent to the sinkhole.

2. Water Supply Sources

a. The approximate location of public or private water supply sources such

129

as springs or wells, as determined from information available from the City Planner and Missouri Department of Natural Resources.

b. Boundaries of any known recharge areas to wells or springs as determined

from information available from the City Planner and Missouri Department of Natural Resources.

3. Other Geologic Features

Locations of caves, springs, faults and fracture trends, geologic mapping units based upon information from the City Planning Department or other reliable sources.

4. Flooding Limits for the sinkholes determined as set forth in this section.

a. A drainage area map showing the sinkhole watershed area. b. Where the site is located in a sinkhole cluster area, this map shall be

extended to include the watershed area and any sinkholes located downstream of the site which may receive overflow drainage from the site.

c. Assessment of potential impacts on ground water quality and proposed

water quality management measures as provided in this section.

I. FLOODING CONSIDERATIONS:

1. Minimum Flooding Analysis: Maximum estimated flooding elevations shall be determined for each sinkhole for both pre-development and post development conditions, assuming no subsurface outflow from the sinkhole. Where the estimated volume of runoff exceeds the volume of the sinkhole depression, the depth, spread, and path of overflow shall be estimated using methods set forth in “Stormwater Runoff Calculations” (page 127) and shown on the map. The overflow volume shall be included, determining the maximum estimated flooding elevations in the next downstream sinkhole. This analysis shall continue downstream until the lowest sinkhole of the sinkhole cluster is reached or overflow reaches a surface watercourse. The volume of runoff considered shall be that which results from a rainstorm with an annual probability of 1 percent (100-year storm) and a duration of 6 hours (5.8 inches for Nixa). The runoff volume shall be determined by the method set forth in Chapter 2 of the SCS TR-55 Manual (Reference 11).

130

No further flooding analysis will be required, provided that:

a. The post-development flooding area of any sinkhole which receives drainage from the site is located entirely on the site.

b. A drainage easement covering the post-development flooding area is

provided for any off-site sinkhole or portion of a sinkhole which receives increased peak rates of runoff from the site. If the sinkhole is not contiguous to the site, an easement must also be provided for the waterway which connects the site to the sinkhole.

c. The minimum entry elevation of any existing structure is at least 1 foot

higher than the estimated flooding elevation from the 1 percent annual probability 6-hour storm.

d. The flooding depth on any existing public road does not exceed the

maximum depths set forth in Drainage of Street and Roadways.

2. Detailed Flooding Analysis. In cases where the conditions set forth in “Minimum Flooding Analysis” (above) cannot be met, a detailed flooding analysis will be required if any increase in runoff volume is proposed. For detailed flooding analysis a runoff model must be made for the sinkhole watershed and reservoir routing analysis performed using hydrographic techniques as set froth in Stormwater Runoff Calculations.

The following alternative methods may be used singularly or in combination to keep flooding levels at pre-development levels:

a. Diversion of Excess Runoff to Surface Watercourses Where feasible, increased post-development runoff may be diverted to

a surface watercourse, provided that:

1). Any increase in peak runoff rate in the receiving watercourse does not crater or worsen existing flooding problems downstream, and

2). The diverted storm water remains in the same surface

watershed.

Storm sewers, open channels and other appurtenances provided for diversions shall be designed in accordance with the applicable sections of these Design Criteria.

The effect of diverted water on downstream watercourses and

131

developments, and requirements for additional detention facilities prior to release of runoff to the surface watercourse shall be determined as set forth in “Detention Facilities” (page 173).

Effects of the diversion shall be shown by reservoir routing analysis. Routing of excess runoff shall be considered satisfactory when it can be demonstrated that the post-development flooding elevation in the sinkhole does not exceed the pre-development flooding elevation within reasonable tolerance (generally 0.1 ft.).

b. Determination of Outflow Capacity of Sinkhole

The stage-discharge characteristics of the sinkhole shall be estimated by monitoring the sinkhole during at least two storm events exceeding 1 inch of runoff in a 6 hour period.

In sinkhole complexes, receiving or terminal sinkholes must also be analyzed if they receive overflow from upstream sinkholes.

Input rainfall hydrographic shall be determined either by a recording rain gage or readings from an approved rain gage at 15 minute intervals. The outflow rate shall be estimated by adjusting the stage-discharge relationship of the reservoir routing model until the maximum reservoir stage in the model correlates with the maximum observed stage in the sinkhole. The maximum stage shall be determined to the nearest 0.1 foot by field survey.

Stages may be determined by field instrumentation at the consultant's option. Information regarding the instrument used shall be submitted with the report.

Where debris lines are used as evidence of maximum stage, photographs shall be provided.

If by accounting for the outflow from the sinkhole, the conditions set forth in this section can be met, no further flooding analysis is necessary.

The volume of runoff storage in the sinkhole(s) can be counted toward storm water detention requirements, provided that proper sediment and erosion control measures are provided as set forth in “Sediment and Erosion Control” and water quality considerations as set forth in this section can be met.

132

If in the opinion of the City Planner, the outflow capacity of the sinkhole may be adversely affected by ground water conditions, the effects of which may not be adequately determined by observing surface water stages, the City Planner may require installation of a monitoring well in each sinkhole, for the purpose of monitoring ground water levels in comparison with surface water levels.

c. Storage of Excess Runoff within the Sinkhole Watershed

Where feasible, detention facilities may be constructed within the sinkhole watershed or in perimeter areas of the sinkhole. These detention facilities must be located outside the sinkhole flooding area determined for post-development conditions.

The flooding considerations set forth in this Section will be met if it can be demonstrated that:

1). Inflow rates to the sinkhole can be reduced to a degree

that, in conjunction with the observed outflow rate, the post-development flooding elevation in the sinkhole does not exceed the pre-development flooding elevation within reasonable tolerance (generally 0.1ft).

2). Sediment & erosion control and water quality

considerations as set forth elsewhere in this section can be satisfied.

J. WATER QUALITY CONSIDERATION: Sinkholes provide direct recharge routes to ground water. As a result water quality in wells, caves and springs may be affected by discharge of runoff from developed areas.

The Sinkhole Evaluation must consider potential impacts of the proposed construction of receiving ground waters and propose measures to mitigate such impacts.

Four primary factors must be considered: (1) Receiving Ground water Use; (2) Relative ground water contamination hazard associated with the proposed development; (3) Ability to capture pollutants; (4) Management measures to be provided to reduce pollutant levels.

1. Receiving Ground Water Use: The Sinkhole Evaluation Report shall

identify whether the site lies within a critical area based upon information available from the City Planning Department.

Where disagreements may arise over whether a site is located within a particular recharge area, dye tracing may be required for confirmation of the destination of water discharges through a sinkhole.

133

a. Critical Areas: The following areas are classified as critically sensitive to

contamination from urban runoff:

Recharge areas of domestic water supply wells Recharge areas of springs used for public or private water supply Recharge areas of caves provide habitat to endangered species such as

the Ozark cave fish

b. Sensitive Areas: All other sinkhole areas will be classified as sensitive to contamination from urban runoff.

2. Ground Water Contamination Hazard: The relative potential for ground

water contamination will be classified as low, moderate, or high depending upon the type of land use, development density and amount of directly connected impervious area. The Sinkhole Evaluation shall identify whether the proposed development poses a low, moderate, or high hazard to ground water uses, as defined below. a. Low Hazard: The following land uses are classified as posing a relatively

low hazard to ground water contamination: 1). Wooded areas and lawns. 2). Parks and recreation areas. 3). Residential developments on sewer, provided directly connected

impervious areas discharging to the sinkhole are less than 1 acre. 4). Low density commercial and office developments provided directly

connected impervious areas discharging to the sinkhole and less than 1 acre.

5). Discharge from graded areas less than 1 acre having required sediment

controls per “Sediment and Erosion Control” Section.

b. Moderate Hazard:

1). Concentrated discharge from streets and parking lots and roofs and other directly connected impervious areas having an area greater than 1 acre and less than 5 acres.

2). Multifamily residential developments and higher intensity office

developments provided the directly connected impervious areas discharging to the sinkhole are less than 5 acres.

3). Discharge from graded areas greater than 1 acre and less than 5 acres

134

having required sediment controls per “Sediment and Erosion Control” Section.

c. High Hazard:

1). Collector and arterial streets and highways used for commercial

transport of toxic materials. 2). Railroads 3). Concentrated discharge from streets and parking lots and roofs and

other directly connected impervious areas having an area greater than 5 acres.

4). Commercial, industrial and manufacturing areas. 5). Individual waste water treatment systems. 6). Commercial feedlots or poultry operations. 7). Discharge from graded areas greater than 5 acres having required

sediment controls per “Sediment and Erosion Control“ Section.

3. Capturing and Filtering Pollutants: The majority of sinkholes drain a limited watershed area. For sinkholes where the surrounding drainage area is small enough that the area draining to the sinkhole flows predominantly as "sheet flow", potential impacts on water quality can be addressed by erecting silt control barriers around the sinkhole during construction and providing a vegetative buffer area around the sinkhole to filter out potential contaminants. When the volume of runoff into the sinkhole increases to the point where flow becomes concentrated, the degree of effort required capturing and filtering out contaminants increases significantly.

Concentration inflow occurs naturally when the sinkhole watershed area reaches a sufficient size for watercourses leading into the sinkhole to form. Concentrated surface flows result as urbanization occurs due to construction of roads, storm sewers, and drainage channels. Subsurface flows can become concentrated through utility trenches.

The Sinkhole Evaluation shall include maps showing any existing watercourse which flows into the sinkhole and location of any proposed concentrated storm water discharges into the sinkhole.

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4. Water Quality Management Measures:

a. Sediment and Erosion Control:

1). Non-Concentrated Flow (sheet flow)

In critical areas, existing ground cover shall not be removed within 25 feet of the sinkhole rim and a silt barrier shall be provided around the outer perimeter of the buffer area.

2). Concentrated Flow

A sediment basin will be required at each point where concentration flows are discharged into the sinkhole.

Sediment basins shall be designed according to the procedures per “Sediments and Erosion Control” Section.

b. Minimizing Directly Connected Impervious Area:

The ground water contamination hazard category for impervious areas may be reduced by reducing the amount of Directly Connected Impervious Area. This is the area of roofs, drives, streets, parking lots, etc. which are connected via paved gutters, channels, or storm sewers.

Directly Connected Impervious Areas can be reduced by providing properly sized grass swales, vegetative filter strips or other Best Management Practices to separate paved areas.

c. Diversion of Runoff:

Concentrated discharges to sinkholes can be reduced to manageable levels or avoided by diverting runoff from impervious areas away from sinkholes where possible.

Diversions shall be done in a manner that does not increase flooding hazards on downstream properties and, generally, shall not be directed out of the surface watershed in which the sinkhole is located.

d. Filtration Areas:

For areas having a low or moderate ground water contamination hazard and where flow into the sinkhole occurs as sheet flow, water quality requirements can be satisfied by maintaining a permanent vegetative buffer area with a minimum width of 30 feet around the sinkhole.

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Use of pesticides and fertilizers will not be permitted within the buffer area. Animal wastes will not be permitted to accumulate in the buffer area.

e. Grassed Swales and Channels:

For areas having a low ground water contamination hazard concentrated flows from directly connected impervious areas of less than one acre may be discharged into the sinkhole through grassed swales and channels.

Swales and channels shall be designed for non-erosion velocities and appropriate temporary erosion control measures such as sodding or erosion control blankets provided.

f. Storage and Infiltration:

Storage and infiltration will be required in the following cases:

1). All areas having a high ground water contamination hazard. 2). Areas having a moderate ground water contamination hazard

where concentrated inflow occurs.

Storage and infiltration basins shall be designed to capture the runoff from storms up to 1 inch in 6 hours and release runoff over a minimum period of 24 hours. Standard outlet structures for sedimentation and infiltration basins are shown in Appendix F.

K. PERFORMANCE STANDARDS/CONSIDERATIONS FOR DEVELOPMENT: Performance standards and considerations for various types of development in sinkhole areas are discussed in the following: 1. Roadways: Subdivision streets should be laid out to avoid sinkholes to the degree possible. Major arterials and highways, however, require specific alignments and, in many cases, it is not possible to create an alignment that avoids all sinkholes. Long term performance is usually the best indicator of future performance. Roadways produce a relatively light loading on soils and, if designed and constructed properly, should provide suitable structural stability. Any collapse sinkholes or solution sinkhole eyes should be stabilized prior to roadway construction. BMPs should be maintained during construction to prevent transport of sediment or other deleterious materials into sinkholes. Storm water conveyance structures should be designed to remove storm water from sinkholes as quickly as possible, and roadways should be designed to route roadway surface runoff away from, rather than into, sinkholes to the degree possible. If the storm water storage capacity (sinkhole volume) of the sinkhole is diminished as a result of roadway construction and post- construction flood routing shows an adverse effect on downstream landowners, additional storm water storage should be provided by either enlargement of the

137

sinkhole by lateral excavation or construction of supplementary detention basins. 2. Utilities: Utilities that are constructed within twenty feet of sinkhole rims must be bedded in flowable fill rather than granular fill. At no time shall a structure be placed over utility lines. The installation of utilities within a sinkhole shall be limited to the sinkhole slope, since the sinkhole floor may be subject to subsidence, collapse, or prolonged ponding of storm water. 3. Residential Construction: Residential structures shall maintain a 10 foot setback from the rim of the sinkhole as identified by a qualified geologist. Residential construction should incorporate drainage swales to divert storm water runoff around sinkholes to the degree possible. Introduction of pesticides and fertilizers is problematic from the standpoint of groundwater quality. 4. Commercial and Industrial Construction: Larger structures that are supported by piers to bedrock can be constructed to the sinkhole rim, or even onto the sinkhole slope, Special considerations will be required, however, to address storm water management and groundwater protection. 5. Recreational use and Green Space: Solutional sinkholes are very appropriate for recreational use and preservation of green space. Sinkholes may be developed with benches, walking trails, playgrounds and plantings, provided they are done so with the understanding that flooding may periodically occur. Recreational uses that would not be appropriate include those that may introduce hazardous materials to the sinkhole or that may cause excessive erosion (BBQ grills, gasoline-powered vehicles, etc) Recreational use will be considered and approved on a case-by-case basis. 6. Sinkhole Closure: Sinkhole closure will be considered an acceptable means of increasing the amount of useable land for development within the City of Nixa provided certain requirements are satisfied. An appropriate site investigation and development plan must be submitted to the City of approval which addresses structural integrity, storm water management, protection of groundwater quality, impact on groundwater recharge, and sustainability. In all cases, the owner/developer should retain the liability for private property and structures within the closed sinkhole, and must provide a bond to the City for maintenance and repair of any infrastructure that the City accepts. All closed sinkholes must be surveyed and legal descriptions submitted to the Christian County Recorder’s Office.

L. DEVELOPMENT REQUIREMENTS:

1. Storm Water Detention in Sinkholes: Where flooding considerations set fort in Stormwater Management Goals and water quality considerations, as set

138

forth in Sediment and Erosion Control, can be met, the volume of runoff storage in sinkholes can be counted toward storm water detention requirements, provided that proper sediment an erosion control measures are provided as set forth in Sediment and Erosion Control.

The volume of required detention storage shall be determined as set forth in Detention.

Excavation within the sinkhole flooding area to provide additional detention storage will not be allowed.

2. Modification of Sinkholes to Increase Outflow Rates: Increasing outflow

rates in sinkholes by excavating the sinkhole eye or installing disposal wells for diverting surface runoff to the ground water system is prohibited, unless clear and imminent danger to the public health and safety can be demonstrated.

3. Setbacks and Use Restrictions:

a. No new construction of any of the following shall be permitted within 10

feet of the sinkhole rim:

Residential, commercial or industrial structures within 10 feet of the rim of a sinkhole that has not been closed a s provided in the regulations.

Swimming Pools. Streets, highways, or parking lots within 10 feet of the rim of a

sinkhole that has not been closed as provided in the regulations. Storage yards for materials, vehicles and equipment.

b. Use of pesticides and fertilizers within 30 feet of the sinkhole rim is

prohibited. c. Use of heavy construction equipment in unaltered sinkholes is prohibited. d. Construction of underground utilities is prohibited within the sinkhole rim

except as provided for in the regulations.

e. Recreational facilities such as hiking, jogging, and bicycle trails, playgrounds, exercise courses, and grass playing fields are permitted within the sinkhole area, provided they are not located within the eye of the sinkhole.

f. Golf courses are permitted subject to approval of a Management Plan for

use of pesticides and fertilizers. g. Clearing and pruning of trees and undergrowth, and limited grubbing of

139

roots is permitted.

h. Landscaping and minor gardening is permitted outside of the sinkhole eye provided erosion and sediment discharge is limited through the use of minimum tillage and mulch.

i. Construction of light incidental landscaping and recreational structures

such as gazebos, playground equipment, etc. is permitted except in the sinkhole eye.

4. Collapsed Sinkholes: Collapsed sinkholes may be stabilized and filled using

approved techniques. A Grading Permit must be issued prior to performing the construction.

The probable cause of the collapse and potential adverse impacts of filling the collapse shall be investigated and information submitted with the Grading Permit Application.

5. Altered Sinkholes: Filling or altering of sinkholes without a Grading Permit

constitutes a violation of this ordinance. In such cases corrective measures must be proposed within the time period specified in the Land Development Code for enforcement of such violations. No corrective or remedial measures shall be undertaken until the proposed remediation plan has been reviewed by the City Planner and a Grading Permit issued.

No Building Permits will be issued, or zoning or subdivision approvals granted until the remedial measures specified in the Grading Permit have been completed.

M. SINKHOLE CLOSURE REGULATIONS: An exemption may be granted to the policy of sinkhole avoidance, minimization, and mitigation upon approval of sinkhole closure application and acquisition of a sinkhole closure permit. The sinkhole closure application shall include the following information:

Reason for the sinkhole closure, Location and description of the sinkhole, including dimensions, depth, and

a description of the sinkhole eye, and one-foot contour interval topographic map of the sinkhole and sinkhole drainage area.

Geotechnical report describing the fill plan, source of clean soil fill, soil

testing data, and specifications for compaction. Foundation design report detailing the design of any structures to be

constructed on the closed sinkhole.

140

Storm water management report that included pre-development and post-

development flooding analysis and describes how storm water will be managed onsite.

Groundwater report that assesses the impact of sinkhole closure on

groundwater quality and goundwater recharge.

Side development report that details site grading, roadway construction,

utility construction, and erosion control (best management practices). The sinkhole closure application must be signed and sealed by a Missouri

Registered Geologist, as appropriate, and must be accompained by a $250.00 review fee and performance bond in the amount of 110% of the cost of improvements. A maintenance agreement must also be provided detailing the continued maintenance of all infrastructure improvements.

The sinkhole closure design must provide for engineered fill with a

permeability of at least 1.0 X l0-6 cm/sec. bearing capacity. Any sinkhole eyes that exist must be stabilized by construction of a graded filter. A survey of the closed sinkhole must be recorded with Christian County Recorder or Deeds.

Reserved-91 thru-94

LOCATION MAP: SW1 / 4, SE1 / 4, SEC. 11, TOWNSHIP 27 NORTH, RANGE 22 WEST

SCALE: 1" • 2000'

LEGEND:

II II

e • EXISTING 5/8" IRON PIN, CAPPED "LC 383" (EXCEPT AS NOTED)

0 • 5/8" IRON PIN SET, CAPPED "LC 383" (EXCEPT AS NOTED)

■ • EXISTING PERMANENT MON. FOUND (EXCEPT AS NOTED)

CONC. DRIVE

l!l • PERMANENT MON. SET (5/8" X 24" REBAR W/ ALUM. CAP.) STAMPED "LC 383"

<n. • POWER POLE ESt.lT. • EASEMENT

EIP • EXISTING IRON PIN N • NORTH S • SOUTH E • EAST W • WEST

lJTIL • lJTIUTY m • CURB INLET

::.: • ARE HYDRANT $ • SEWER MANHOLE

-SS- • SANITARY SEWER LINE --W- • WATER LINE --STM- • STORMWATER PIPE

EX. • EXISTING (M) • MEASURED DATA

BSL • BUILDING SETBACK LINE TYP. • TYPICAL U&D • UTIUTY AND DRAINAGE R/W • RIGHT-OF-WAY U/E • UTIUTY EASEMENT

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PRELIMINARY PLAT WASSONCOMMERC~LDEVELOPMENTPHASE4

A PART OF THE SW1/4,SE1/4,SEC. 11 T27N, R22W

NIXA, CHRISTIAN COUNTY, MISSOURI

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LEGAL DESCRIPTION SOURCE OF DESCRIPTION: DEED BOOK 282 AT PAGE 1268 IN THE CHRISTIAN COUNTY RECORDER'S OFFICE.

THAT CERTAIN PARCEL OR TRACT OF LAND BEING A PART OF THE SOUTHWEST QUARTER (SW1/4) OF THE SOUTHEAST QUARTER (SE1/4) IN SECTION 11, TOWNSHIP 27 NORTH, RANGE 22 WEST, IN THE CITY OF NIXA, CHRISTIAN COUNTY, MISSOURI, BEING MORE PARTICULARLY DESCRIBED AS FOLLOWS:

COMMENCING AT AN EXISTING IRON PIN AT THE NORTHWEST CORNER OF LOT 4A OF THE REPLAT OF LOTS 4 & 5 WASSON COMMERCIAL DEVELOPMENT, A SUBDIVISION IN THE CITY OF NIXA, CHRISTIAN COUNTY, MISSOURI; THENCE N89'40'57"W, A DISTANCE OF 188.03 FEET TO THE SOUTHEAST CORNER OF LOT 14 IN WASSON PLACE PHASE VI, A SUBDIVISION IN NIXA, CHRISTIAN COUNTY, MISSOURI; THENCE N01'22'55"E, ALONG THE EAST LINE OF LOTS 5-14 IN SAID WASSON PLACE PHASE VI, A DISTANCE OF 832.99 FEET TO AN EXISTING IRON PIN AT THE NORTHEAST CORNER OF SAID LOT 5 FOR A POINT OF BEGINNING; THENCE N01'22'55"E, ALONG THE EAST LINE OF LOT 4 IN SAID WASSON PLACE PHASE VI, A DISTANCE OF 49.58 FEET TO AN EXISTING "X" IN CONCRETE AT THE NORTHEAST CORNER OF SAID LOT 4; THENCE N49'28'40"W, ALONG THE NORTH LINE OF LOTS 2-4 IN SAID WASSON PLACE PHASE VI, A DISTANCE OF 203.82 FEET; THENCE N55'44'52"W, ALONG THE NORTH LINE OF LOTS 1-2 IN SAID WASSON PLACE PHASE VI, A DISTANCE OF 78.53 FEET TO AN EXISTING "X" IN CONCRETE; THENCE N68'42'25"W, ALONG THE NORTH LINE OF SAID LOT 1, A DISTANCE OF 79.31 FEET TO AN EXISTING "X" IN CONCRETE AT THE NORTHWEST CORNER OF SAID LOT 1; THENCE N89'11 '22"W, A DISTANCE OF 8.44 FEET TO AN EXISTING IRON PIN AT THE SOUTHEAST CORNER OF LOT 4 IN WASSON PLACE PHASE IX, A SUBDIVISION IN THE CITY OF NIXA, CHRISTIAN COUNTY, MISSOURI; THENCE N01'18'04"E, ALONG THE EAST LINE OF LOTS 1-4 IN SAID WASSON PLACE PHASE IX, A DISTANCE OF 390.87 FEET TO AN EXISTING IRON PIN AT THE NORTHEAST CORNER OF SAID LOT 1; THENCE S88'38'44"E, A DISTANCE OF 60.00 FEET TO AN EXISTING IRON PIN ON THE EAST RIGHT-OF-WAY LINE OF OLD WILDERNESS ROAD; THENCE N01'19'21"E, ALONG SAID EAST RIGHT-OF-WAY LINE A DISTANCE OF 374.33 FEET TO AN EXISTING IRON PIN; THENCE NORTHEASTERLY ALONG A CURVE TO THE RIGHT HAVING A RADIUS OF 30.00 FEET, A CENTRAL ANGLE OF 88'52'26", A CHORD BEARING OF N46"00'22"E, A CHORD LENGTH OF 42.01 FEET, AN ARC LENGTH OF 46,53 FEET TO A POINT ON THE SOUTH RIGHT-OF-WAY LINE OF NORTHVIEW ROAD; THENCE S89'33'25"E, ALONG SAID SOUTH RIGHT-OF-WAY LINE, A DISTANCE OF 181.95 FEET; THENCE S00'26'08"W, ALONG SAID SOUTH RIGHT-OF-WAY LINE, A DISTANCE OF 9.92 FEET; THENCE S89"33'52"E, ALONG SAID SOUTH RIGHT-OF-WAY LINE, A DISTANCE OF 74.74 FEET TO A POINT ON THE WEST LINE OF A TRACT OF LAND DESCRIBED IN BOOK 116 AT PAGE 528, BOOK 208 AT PAGE 356, AND BOOK 291 AT PAGE 158 IN THE CHRISTIAN COUNTY RECORDER'S OFFICE; THENCE S01'39'49"W, ALONG THE WEST LINE OF SAID TRACT OF LAND, A DISTANCE OF 638.78 FEET TO AN EXISTING IRON PIN AT THE SOUTHWEST CORNER OF SAID TRACT OF LAND; THENCE S89'55'44"E, ALONG THE SOUTH LINE OF SAID TRACT OF LAND A DISTANCE OF 517.68 FEET TO AN EXISTING IRON PIN ON THE WEST RIGHT-OF-WAY LINE OF U.S. HIGHWAY N0.160; THENCE S01"37'28"W, ALONG SAID WEST RIGHT-OF-WAY LINE, A DISTANCE OF 82.92 FEET TO A EXISTING STEEL RIGHT-OF-WAY MARKER; THENCE SOUTHERLY ALONG A CURVE TO THE LEFT HAVING A RADIUS OF 11584.20 FEET, A CENTRAL ANGLE OF 01"31'17", A CHORD BEARING OF S00'53'13"W, A CHORD LENGTH OF 307.57 FEET, AN ARC LENGTH OF 307.58 FEET; THENCE S45'02'34"W, A DISTANCE OF 21.23 FEET: THENCE S89"59'47"W, A DISTANCE OF 212.85 FEET; THENCE NORTHWESTERLY ALONG A CURVE TO THE RIGHT HAVING A RADIUS OF 66.00 FEET, A CENTRAL ANGLE OF 52"41 '25", A CHORD BEARING OF N63"39'31 "W, A CHORD LENGTH OF 58.58 FEET, AN ARC LENGTH OF 60.70 FEET; THENCE WESTERLY ALONG A NON-TANGENT CURVE TO THE LEFT HAVING A RADIUS OF 68.50 FEET, A CENTRAL ANGLE OF 104"14'52", A CHORD BEARING OF S79"45'34"W, A CHORD LENGTH OF 108.14 FEET, AN ARC LENGTH OF 124.63 FEET; THENCE S52"28'09"W, A DISTANCE OF 87.32 FEET; THENCE N61"00'48"W, A DISTANCE OF 113.55 FEET TO THE POINT OF BEGINNING. SAID TRACT CONTAINS 1 1.305 ACRES (MORE OR LESS) AND IS SUBJECT TO ANY EASEMENTS, RIGHTS-OF-WAY, AND RESTRICTIONS OF RECORD.

CURVE TABLE

CURVE RADIUS LENGTH TANGENT CHORD DELTA CHORD BEARING

C20 250.00' 302.08' 172.56' 284.03' 6913'52" S3318'52"E

C21 250.00' 302.43' 172.82' 284.32' 6918'43" N3316'26"W

C22 220.00' 265.83' 151.86' 249.95' 6913'52" S3318'52"E

C23 280.00' 338.33' 193.27' 318.12' 6913'52" S3318'52"E

C24 280.00' 214.05' 112.56' 208.87' 43•47•59• N46"01 '49"W

C25 220.00' 266.14' 152.09' 250.20' 6918'43" N3316'26"W

C26 280.00' 124.68' 63.39' 123.65' 25°30'44" N11"22'27"W

C28 68.50'(M) 17.13' 8.61' 17.09' 1419'49" S40"08'15"W

C29 58.00' 46.49' 24.57' 45.25' 45°55'15" N24'20'32"E

C30 66.00' 44.57' 23.17' 43.73' 38"41'44"' S17"57'57"E

C31 66.00' 60.69' 32.68' 58.58' 52"41'25" S63"39'31"E

C32 68.50' 23.51' 11.87' 23.40' 19"40'02" S37'28'09"W

C33 68.50' 101.12' 62.31' 92.19' 84"34'50" S89"35'35"W

C34 30.00' 46.53' 29.42' 42.01' 88'52'26" S46"00'22"W

C35 11584.20' 307.57' 153.80' 307.57' 1"31'17" S00"53'13"W

C36 250.00' 302.43' 172.82' 284.32' 6918'43" N3316'26"W

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1. THE PROPERTY SHOWN HEREON LIES WITHIN AN F.E.M.A. IDENTIRED FLOOD HAZARD AREA DESIGNATED AS ZONE X, AN AREA OF MINIMAL FLOODING, ACCORDING TO THE FLOOD INSURANCE RATE MAP COMMUNllY MAP PANELS NO. 29043C0070C, WHICH BEARS AN EFFECTIVE DATE OF DECEMBER 17, 2010. 2, NO INTERNAL FENCES WERE LOCATED DURING THE COURSE OF THIS SURVEY, AND ARE NOT SHOWN HEREON. 3. LOTS 8-13 ARE ZONED AS HC. 4. HC BUILDING SETBACKS: FRONT 60', SIDEYARD 20', SIDEYARD WITH STREET FRONTAGE 20', REAR 20'. 5. SIDEWALKS WILL BE PROVIDED ON ONE SIDE OF ALL INTERNAL STREETS EXCEPT AVEN ROAD. 6. ALL STREETS, SANITARY SEWER, WATER, AND STORM WATER IMPROVEMENTS WILL BE PROVIDED PER CllY OF NIXA SPECIRCATIONS. 7. THERE SHALL BE A 12 FEET WIDE lJTIUTY EASEMENT PARALLEL AND ADJACENT TO ALL STREET RIGHT-OF-WAY LINES EXCEPT AS NOTED. 8. STREET RIGHT-OF-WAY LINES ARE PARALLEL WITH THE CENTERLINE DATA, EXCEPT AS NOTED. 9. LARGEST LOT: LOT 10 (2.78 ac.) 10. SMALLEST LOT: LOT 13 (1.28 ac.) 11. LOT 10 IS COMMON GROUND & SHALL BE DEDICATED TO THE PROPERTY OWERNERS ASSOCLo\TION.

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SHAFFER~ ~INES WASSON COlvIMERCIAL

DEVELOPMENT PHASE 4 CONSULTING ENGINEERS - REGISTERED LAND SURVEYORS

P.O. Box 493, Nixo, Missouri, 65714 Tel: (417) 725-4663 - Fax: (417) 725-5230

Email: chines@shafferhines .com

. : ~ . . -._:"lllilnlllll!II!~·

J. CLAYTON M. HINES E-29799

A SUBDIVISION IN THE CITY OF NIXA, CHRISTIAN COUNTY, MISSOURI

OWNERS/DEVELOPERS: WASSON FAMILY LIMITED PARTNERSHIP

Documents

Memorandum - Nixa