1998-05-14 Work Session
NEW HANOVER COUNTY BOARD OF COMMISSIONERS BOOK 26
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
ASSEMBLY
The New Hanover County Board of Commissioners held a Work Session on Thursday, May
14, 1998, at 6:15 p.m. in Conference Room 501 of the New Hanover County Administration
Building, 320 Chestnut Street, Wilmington, North Carolina.
Members present were: Commissioners Buzz Birzenieks; Ted Davis, Jr.; Charles R. Howell;
Vice-Chairman Robert G. Greer; Chairman William A. Caster; County Manager, Allen O'Neal;
County Attorney, Wanda M. Copley; and Deputy Clerk to the Board, Teresa P. Elmore.
Chairman Caster called the meeting to order and reported the purpose of the Work Session
was to hear a presentation by Mr. Dan Dawson, of W. K. Dickson & Company, Inc. on the status of
the stormwater management study performed on the Pages Creek Watershed.
Mr. Dawson introduced those assisting in the presentation as H. Rooney Malcom, Ph. D.E.,
Everett Knight, and David Holdstock. The presentation would be an overview of stormwater
management issues in New Hanover County based on the findings from the Pages Creek Study.
Topics to be discussed are: stormwater management tools, the need for policies and ordinances,
proposed EPA regulations on stormwater management, and suggestions on how the Board should
proceed.
Dr. Malcom, former professor at North Carolina State University, spoke of his years of
teaching and working with jurisdictions in formulating stormwater management programs and
systems. As New Hanover County makes a rapid transition to an urbanized county, watersheds will
be changing very radically unless special provisions are in place to preserve the drainage patterns.
He discussed the essential elements of a stormwater management program as follow:
Ordinances and Policies
The Commissioners can set the level and flavor of the program for New
Hanover County through ordinances and policies. He recommended the Commissioners consider the
local situation and not depend heavily on programs that work in other areas. An interactive
relationship between the Commissioners and the consultants will be important in establishing the best
program for the County.
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Watercourse Development Policy
A watershed is a large drainage area of small springs
forming the pattern of the drainage system. In order for a drainage system to work properly
throughout development, the backbone drainage system of the watershed will need
protection. A watercourse development policy will specify the building of features to provide
protection of streams.
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System Maintenance Policy
Maintenance of a stormwater system is the most difficult to
provide adequately. If detention ponds are built on public space, the County will need to
budget for the maintenance of numerous basins. Other jurisdictions have regulations that
require stormwater detention basins to be built on private property. Dr. Malcom cautioned
the Commissioners to consider the extent of work that should be performed on private
property. If drainage problems occur on privately owned basins, a system may become
fragmented with no controls over the drainage system. Other areas have developed policies
that allow a drainage group to maintain streams on a regular schedule. Others participate by
installing pipe that the property owners have purchased. The main concern for the
Commissioners is to maintain the integrity of the drainage patterns that exist or the desired
drainage patterns of the future. These programs will need to be developed in parallel, not a
sequential process.
System Identification and Database
A database of detailed information on a watershed will allow
the County to know how a particular watershed functions. Concepts for a drainage system can be
tested by using the database. Mr. Holdstock will speak on how the technical information received
on the Pages Creek Watershed can be applied.
Drainage Master Plan
Ultimately, the County will need to have a drainage master plan that
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
illustrates how the backbone drainage system will be developed. As situations in the watershed
change, the document will need to be updated.
Storm Drainage Manual
The Board will need to approve a reference document of various
principles and needs of stormwater management facilities, which will be used by developmental
engineers and staff. The manual should be maintained by staff and will not require approval by the
Board for most changes.
Financial Management Strategy
The watershed is interconnected with old and new developments,
as well as commercial and private properties that fit together to make the whole drainage system.
The financial management strategy will need to address maintenance of old parts of the watershed
as well as provide a strategy for new developments. Everyone in the watershed must participate in
the production and change in the stormwater patterns.
Training and Public Education Program
As the County develops the stormwater management
program, it will be important for the public to understand how the drainage system works and what
the stormwater management program will achieve.
Mr. Dawson briefly discussed the results of the study on Pages Creek. Details of the study
were presented to the Commissioners several months ago showing the need for a stormwater
management program. Regulations are needed to better protect water quality and to better manage
flash flooding. Mitigation, channelization, and culvert replacement can manage some of the
stormwater. Other ways can be very expensive and will not please everybody. As the consultant, he
will work with the Commissioners to determine how far the County will need to go in a stormwater
management program.
In discussion on the occurrence of flooding in Pages Creek, Dr. Malcom explained flooding
in the floodplain is a very natural event. People do not realize that a natural stream floods out of its
banks every other year on average. The Commissioners’ main responsibility will be to provide a
waterway that will not injure anyone.
Mr. Dawson stated the County’s floodplain ordinance and FEMA regulations limit
development in designated floodplain areas, but not necessarily isolated areas that are not mapped
on the floodplain maps. With the completion of the study, the watershed area of Pages Creek is fully
understood. Since the area is almost built out, future development will not significantly change the
stormwater conditions that occur in the watershed. Using the current rules and regulations, a 20%
increase in flow in volume could be expected. There may be an opportunity to protect some receding
water, but that will be a public policy decision. The purpose of the Pages Creek Study was to look
at the drainage and see how these findings can be applied across the County in a comprehensive
drainage program.
Mr. Dawson noted several tools can be used for managing stormwater and watersheds. Mr.
Holdstock, who has worked with most cities and counties in North Carolina in establishing GIS
systems, will brief the Board on using the latest technology to implement a stormwater management
program. New Hanover County is ahead of other counties because the GIS system has been a work
in progress for several years.
Mr. Holdstock explained GIS is used with the data engine to monitor stormwater management
programs or systems. Using digital information, a three-dimensional terrain model can be generated.
The desktop GIS system can be linked with the hydrologic and hydraulic models to produce a graphic
image. Graphic output depicting flood-prone areas can show what needs to be done in a particular
drainage area. He presented the stages of Flood Prediction Mapping as follow:
1.Characteristics of the landscape are calculated and input into hydraulic model.
2.Runoff information is combined with a stream cross section information in a hydraulic model
to determine how deep the water would be at any location.
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
3.Water surface elevations are passed back to GIS and overlaid on a terrain surface to
determine areas prone to flooding.
He further explained the GIS information can be extracted and fed into the model. When the
land use and vegetation information is combined with hydraulic model data, the water depth can be
determined for any location. Once the modeling has been formed, the zones of impact (vulnerability
analysis) can be predicted. Much of the State- and County-based data is accessible and can be
interfaced for querying or browsing. New Hanover County has cadastral (parcel information), land
use, zoning, land cover, hydrography, and Q3 Flood digital information that can be implemented into
the stormwater management program. The collection of data is the most expensive part of building
digital information and the County has begun this investment.
A field assessment is performed to obtain the GPS Inventory of a catch basin. Some areas
have a complete digital inventory of catch basins, location of pipes, swells, and other infrastructures.
Information is gathered by paper records and field notes, digitizing from paper maps, scanning,
photogrammetry, and remote sensing. Topographical mapping is very important in getting the
complete picture of a stormwater management system.
Chairman Caster asked Planning Director Hayes about the County’s GIS maps. Director
Hayes responded the County received the original mapping in 1974, an Ortho photography and
ground control mapping was completed in 1994. In February 1998, the County was reflown for an
update to the mapping to give more accurate data. The County can layer mappings of NCDOT and
other State agencies with the County’s data almost perfectly.
Assistant County Manager Weaver explained the first digitalized data did not line up
accurately with the cadastral mapping; however, the Ortho photography was a better quality job. He
commented on the County’s GIS system as one of the best in the State because of the funding
commitment made by the Commissioners.
Mr. Dawson spoke of the advancement in technology during the last two years that will be
used as management tools. Culvert and channel inventories that were taken at Pages Creek were by
field crews using traditional survey techniques and pattern benchmarks. Eventually, the County will
want an inventory of all watersheds and will need to decide the thresholds of that inventory.
Dr. Malcom commented on the new mapping systems that can depict the topography in a very
exaggerated vertical scale to show drainage patterns which would be difficult to determine through
aerial views.
Mr. Everett Knight presented sample slides of Watershed Model Systems. The WMS is the
preferred model because it is being developed with the Arc Information System. A watershed can
be automatically delineated thereby reducing field work drastically. Once the watershed is delineated,
parameters, such as area, slopes, longest flow, and stream length, can develop the flood data for
hydraulic analysis of the floodplain.
After the Pages Creek basin project had begun, the ARCVIEW spatial analyst program was
developed. The software program allows the spatial data of grids, TINs (triangular integrated nodes),
and shapes to be formatted in the HEC-1 and HEC-2 hydrologic perimeter models. These
mathematical lines interpret or create the topography on the maps. This data incorporated in a GIS
photographic form can be used to develop the discharge data used for the estuary analysis. The
models can be interfaced with other engineering programs such as TR-20, Q3 Data, National Flood
Frequency, as well as perform water quality analysis.
Once the GIS system is using information on land use, zoning, soils, regulatory boundaries,
wetland boundaries, and city/county limits, the County will have the tools to make decisions about
stormwater management.
Mr. Knight specified certain engineering and planning work that will need to be performed:
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
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Prepare a Detailed System Inventory
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Develop a Stormwater Master Plan
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Develop Technical Support Data
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Determine Floodplain Limits
He explained the County will need to know the location of every major structure or culvert
crossing and watershed boundaries because of EPA regulations. EPA Phase II Regulations will be
effective in two years and will require governments to participate in the following components:
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Public Education
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Public Involvement in Local Program Development
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Elimination of Illicit Connections
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Controls on Construction Activities
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Post Construction Management
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Implementation of Good Housekeeping Measures
The EPA will require local governments to inform property owners of their responsibility in
storm drainage concerns, such as cleaning ditches, prohibiting the dumping of grass clippings into
drainage inlets, and proper use of fertilizers. EPA will require the governmental entities to inventory
and describe their drainage systems. Illicit connections from a home or industry that discharges
drainage from a subsurface drainage, such as the floor of a manufacturing facility or a washing
machine drain, will need to be corrected.
Mr. Knight commented that the main purpose of the EPA regulations is to address water
quality issues. Urbanized densities of populated areas, and not political boundaries, define the
boundary areas for EPA. The City of Wilmington and New Hanover County have been grouped
together.
Chairman Caster commented that the Wilmington City Council should have been invited to
this work session and will need to be included in future discussions of stormwater management.
In further discussion of EPA regulations, Mr. Knight explained the County will need a good
erosion control review process to check new construction. Updating inventory databases and
maintenance of existing facilities will need to be performed regularly. Flooding problems associated
with hurricane damage, such as clogged drains and debris in channeled areas, will need to be routinely
inspected.
Vice Chairman Greer asked how most communities addressed post-construction management
of detention ponds and who verifies that a drainage area is functioning properly.
Dr. Malcom responded a system maintenance policy will need to be a part of the County’s
ordinances. The Board will need to decide how the program will operate. Another major concern
that needs to be addressed in the ordinance is stream-bank deterioration. Although Pages Creek
showed no serious stream-bank deterioration, large slumping banks along the stream can be very
difficult to repair.
Vice Chairman Greer asked how other concentrated areas provided cooperation between city
and county governments.
Dr. Malcom replied the Charlotte-Mecklenburg area has combined water and sewer into a
city/county stormwater services department. Several places have joint drainage manuals and land use
regulations that are applied to both city and county areas.
Mr. Dawson noted water and sewer inter-local agreements have been used in the past;
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
however, stormwater will require another kind of arrangement. Phase II regulations will most likely
address this concern.
Mr. Knight addressed how the County should develop and implement a stormwater
management program. A stormwater ordinance is a mechanism to manage the urban drainage flood
control and water quality for the County. Besides being technically and financially feasible, the
ordinance must be realistic. The Commissioners must play an active role in determining what will
work in New Hanover County. Along with a vision of what needs to be done, resources will need
to be in place to implement the policies. Some tools are available and can be used wisely to gradually
evolve the program.
The first step in developing ordinances and policies is to identify the problems and issues, such
as water quality or erosion and sedimentation control issues. The Board may want to approve
engineering design and analysis concepts in developments within floodplain areas. Or the Board may
allow development based on a flood study. The Board will need to decide who will do the
maintenance of stormwater facilities, how many employees will be needed to implement the program,
and how much a stormwater management program will cost.
After the problems and issues are determined, a mission statement can be developed to give
the program direction. Eventually, specific goals will need to be reviewed and updated because of
changes in technology and Federal programs, such as the EPA’s Phase I and Phase II regulations.
As the County’s consultant, W. K. Dickson can formulate a set of objectives and develop policies.
The ordinances may define how to deal with a ten-year flood versus a 100-year flood, the size of a
drainage area, and if stormwater detention will be required. However, some engineers are discussing
the effectiveness of detention basins.
In conclusion, the consultant can develop policies and ordinances and present them to the
Board for its decision. Stormwater management problems can be identified and solutions
recommended. Goals can be established and provisions placed in the ordinances. The
Commissioners, staff and citizens will need to review and react to the proposals. County staff will
need to draft the documents, legally review the contents, and implement the ordinances.
The program priorities were noted as the following:
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Develop a Stormwater Mission Statement
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Establish Objectives, Program and Budget
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Develop a Financial Management Strategy (Utility Fee or Tax)
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Evaluate Inter-local Agreements
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Utilize Technological Advances in GIS, GPS, and Hydrologic/Hydraulic Models
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Develop Program Elements
Chairman Caster asked how the County can handle problems in post-construction drainage
systems.
Mr. Dawson responded the design standards manual can specify that an engineer must certify
completion of a project and that the project was constructed in accordance with the permit. Water
and sewer projects, as well as stormwater projects approved by the State, require similar
certifications. The Commissioners will need to decide who will enforce the regulations, whether an
independent inspector files a report to the County or whether County staff performs an inspection and
charges an administrative fee or user fee to those who benefit from the service. The drainage problem
at the Crosswind Subdivision is a watershed management situation that can occur in future
subdivisions because the State does not regulate erosion control matters beyond the property line.
If the County wants some control of erosion control problems and post-development runoff, an
overall watershed management plan will need to be established. A master drainage plan will evaluate
the cumulative effects of drainage.
Mr. Dawson spoke on the law that allows establishing drainage outlets in areas where there
are no outlets. The County will need to decide who will pay for this benefit in a
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
development. The County will need to buy and receive permission to cross property to form outlets
that will discharge water in a particular direction. Or a drainage district can be established to build
the outlets.
Chairman Caster spoke of a problem where a house was being flooded from the flow of water
from drainage ditches.
Mr. Dawson responded the County’s policies can require a development to demonstrate or
prove that the property will drain properly. The original property owner may accept a drainage
problem; however, the next owner may want the County to solve the problem.
Commissioner Birzenieks asked how much of the flooding that naturally occurs can be
prevented by establishing a stormwater management program.
Mr. Dawson replied based on the findings in Pages Creek, $30 million could be spent to
resolve its flooding problems. However, significant improvements can be made by replacing
undersized culverts at a cost of $390,000, which is more economically feasible. After the County has
an inventory of all culverts, the Board will know how much money will be needed to replace all
culverts in the county.
Chairman Caster asked how many houses in the Pages Creek area could be charged an
assessment fee similar to the proposed fee in the City.
Mr. Dawson responded the City will have a monthly fee for single family homes, but
commercial development will be based on other elements. In looking at a cost analysis to cover most
of the improvement project, each home would need to be assessed several hundred dollars per year.
The Board will need to decide if the improvements will be a direct benefit to the people in the
watershed or to the entire county. The County can have two funding mechanisms: 1.) All property
owners can pay an assessment to provide protection to water quality since the program will need a
base level of funding. 2.) A variable cost can depend on complications in the watershed and the
benefit to those living beside the creek or a particular view, etc. Some watersheds will cost more to
improve and the County can charge different rates for each watershed.
Assistant County Manager Weaver explained the City’s program was established several years
ago and has established funds. Before significant improvements can be made in Pages Creek or any
watershed, the County will need a capital funds account. An assessment could be made on every
home, plus a monthly user fee could be established to pay for the operation and maintenance of a
facility.
Mr. Dawson spoke on how the County can work on several projects to achieve a management
program. FEMA grants or other funds may be available for topography survey or mapping. Direct
benefits, such as the GIS system, can be received without allocating local funds.
In discussion of NCDOT’s role in culvert replacement, Mr. Dawson reported the local
division was interested in working with the County, but had limited funds. The criterion for road
improvement projects is the frequency of a road being overtopped by water. If resources were
available, NCDOT would replace undersized culverts to prevent roads from being overtopped often.
If the County inventories the culverts and identifies particular road hazards, DOT will want to correct
the problem.
In other discussions, Assistant County Manager Weaver asked if the County should enact
controls on new developments to prevent existing problems from getting worse, since this would be
a relatively low cost to the County. He asked if that part of the program should be implemented
before developing data and plans?
Mr. Dawson responded that the County can go in several directions to achieve the goal,
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
but the first phase is to set up the framework. After a comprehensive stormwater management
program is established, solutions can be implemented in a formal structure.
Mr. Knight noted FEMA has offered the National Flood Insurance Program to some rural
coastal counties. A 20% discount is given on insurance premium rates if the area has a
comprehensive drainage program.
Dr. Malcom explained when an area is set aside for drainage, the usefulness and salability of
property become limited. Environmental controls can be attractive and should not look like open
sewers. Improving water quality in watersheds near estuarine areas is important. Generally, smaller
storms cause more water to flow out of watershed areas. An approach the County can consider is
to slow the water flow by promoting infiltration with outlet buffers. Several methods can be used,
however, Dr. Malcom warned against controls that may be too costly and ineffective. Currently,
Raleigh’s detention ponds are not maintained and are filled with vegetative growth. He recommended
the County’s plan should grow incrementally and responsibly and not to expect a
Charlotte/Mecklenburg program in a short period.
Vice Chairman Greer asked if the County should be more concerned with protecting water
quality in the creeks or protecting property from flooding caused by storm surge during hurricanes
or tropical storms.
Dr. Malcom responded culverts are very important features in watershed management. Some
culverts serve as detention ponds, although not intended for that purpose. Culverts should be used
to control peak rate runoff, if the County can install the culverts inexpensively and without causing
upstream damage. The Board will need to make a very complex and interactive decision using the
modeling approach. If culverts have plates on the front that constrict water flow, the model can
predict the results downstream. If the GIS systems are not used, the Board will be making difficult
decisions.
Mr. Dawson reported potential sites in the Pages Creek area have been identified for detention
ponds. Because of the flat terrain and expensive property values, managing upstream storage will be
difficult. Culvert size is not an issue when water is on top of the roads. Nonetheless, roads can form
temporary barriers until the surge is at a certain level. There may be some benefit in sending the
water flow to the wetland areas to protect the downstream estuarine waters. An effective treatment
would be to purchase some wetland areas for the purpose of flooding.
Mr. Knight noted another alternative for a hazard mitigation program is to purchase flood-
prone properties instead of replacing culverts or other improvements. Hurricane Fran made people
realize to repair the same property repeatedly because of flood damage was not solving the problem.
Dr. Malcom pointed out that while economically, the best solution may be to purchase flood-
prone property, sometimes the owner may not want to move; thereby, raising the house three to four
feet to prevent flood damage may be an alternative.
County Manager O’Neal informed the Board that FEMA will soon require local governments
to have mitigation plans for either hurricane areas or earthquake zones to receive funding.
Vice Chairman Greer asked for a definition on the degrees of storms as in a 10-year or 100-
year flood or rain event.
Dr. Malcom explained a 100-year flood is equaled or exceeded on the average once every 100
years. The probability of being exceeded in a given year is 1%. It is a statement of probability
whether flooding will occur in a given year. A 10-year flood means there is one over 10 or a 10%
chance of a 10-year flood. A 2-year flood equals a 50% probability. The joint probability estimates
of getting at least one 100-year flood in the next 50 years is quite high
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WORK SESSION ON PAGES CREEK WATERSHED STUDY, MAY 14, 1998
at 35%. The probability of getting one 10-year storm in the next 25 years is 93%. Local drainage
systems are usually designed using the 10-year storm criteria. There is a risk of 93% that by the end
of a 25-year period, an area will have at least one event that will overtop the system.
Vice Chairman Greer stated he recently heard that the flood of a 100-year event is 11 feet
above sea level at the shoreline. At one time, the figure was 13 feet. He asked who performed the
study in New Hanover County and how was the figure determined?
Dr. Malcom explained revised figures are based on using better estimating and computational
methodologies. Good gauging stations have been used since 1928; and good statistical computational
methods have been used since 1960. Because of computers, longer database information, and better
methodologies and modeling, the engineers can predict more accurately. FEMA and/or the Corps
of Engineers are responsible for getting the data. Often, they hire engineering firms to run the
analysis.
In conclusion, Mr. Dawson summarized as a result of the Pages Creek Study, it is obvious
the County needs a stormwater management program. The Board will need to decide how much the
County can afford to do in a program and if the County will need a new department or a new division
in Engineering. With the immense water and sewer activity in the County, a new group or
department may be needed. The Planning Department will need to be a part of the process because
elements from Planning and Engineering will be used to develop a comprehensive stormwater
management program.
Commissioner Birzenieks expressed concern that people’s expectation in the results from the
study will far exceed reality. Many will think a stormwater management program will solve all
drainage problems. Consequently, the Commissioners and the Engineering Department will receive
many calls from home owners who have built in gullies thinking the County can solve their drainage
problems. The public will need to be realistic about their expectations.
Mr. Dawson commented it will be a tough decision to know how much funding will be needed
to start the program. It will place a strain on the County to provide the higher levels of service.
Dr. Malcom added that most places develop a stormwater program with a lot of public
participation and education. It is important for the homeowners to know if a stream is in the
backyard, flooding will naturally occur every other year on the average. Charlotte and Denver are
doing exceptional jobs of public participation and public education with local newsletters. Although
water management rules are different in the West, the Denver area has an urban drainage district with
a quasi-government entity.
Chairman Caster commented that New Hanover County and the City of Wilmington should
have a joint program because of the small size of the county. The governments will need to cooperate
to provide a joint program.
Dr. Malcom recommended the County explore joint programs like Jacksonville, Florida,
where tough negotiations were made between the city and county governments.
Mr. Dawson pointed out the scope of work for the project consisted of hydrology and
hydraulic analysis of Pages Creek, as well as making an outline of ordinances, drainage manual, etc.
Because of the limits placed on the scope of work, he hoped the Commissioners were satisfied with
the work performed and wished he could have provided more answers. He said the final report will
be presented to the Board at a Regular Board Meeting. He offered the services of W. K. Dixon for
future development of the program.
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ADJOURNMENT
Chairman Caster expressed appreciation for the informative presentation. He adjourned the
meeting at 8:00 p.m.
Respectfully submitted,
Teresa P. Elmore
Deputy Clerk to the Board