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NATURAL ENVIRONMENT PLAN

INTRODUCTION

Natural environment areas are of prime importance to the community. Besides serving as aesthetic amenities which enhance the total quality of life in the area, they perform important ecological roles. Natural areas often act as buffers or barriers in determining the extent and direction of development and growth. Therefore, it is necessary that special consideration be given to these areas in formulating North Liberty’s Comprehensive Plan. Environmentally sensitive areas include those characterized by prime farming soils, steep slopes, forested areas, soil limitations, floodplains and rivers/creeks. The City has expressed concerns with regards to the preservation and enhancement of these features within the City limits, as well as the extra territorial jurisdiction area.

SOIL SUITABILITY FOR URBAN DEVELOPMENT

A variety of soil types and suitability levels exist in the North Liberty area. There is a narrow band of soils with only slight limitations located east of North Liberty. The soils with moderate limitations are most prevalent in the region, however, their limitations are caused by two different factors. The moderate soils along the river corridor have a number of areas with limitations primarily due to steep slopes. The soils encompassing the City of North Liberty also have moderate limitations, but these limitations are primarily due to sub-soil wetness, and the effects this has on dwellings with basements. The area of severe limitations is located northwest of North Liberty and these limitations are caused by flooding and soil wetness.

Careful consideration must be given to the limiting soil factors present on a site prior to approval of development requests. Due to the prevalence of moderate soils within the City limits and the extra territorial jurisdiction area, each development request should be subject to specific review by the City Engineer. At any time during the review process, or during actual construction, if a site under study is found to contain soils presenting development limitations, methods to correct or overcome these limitations should be done in accordance with Uniform Building Code standards and state regulations.

Another requirement that the City enforces in response to the prevalence of sub-soil wetness, is the requirement of all buildings constructed with basements to provide adequate sump pumps and a sump pump collection system for the new subdivision to remove moisture from the building. The City must continue to review and update its existing requirements in respect to site drainage, to help eliminate future flooding concerns.

WATER QUALITY

A central feature within the North Liberty area is the Iowa River, and the reservoirs which have been created along the river. Coralville Lake and Lake MacBride were created in part to control flooding downstream on the Iowa River. Secondary benefits of the lakes include recreation, wildlife habitat, and improved water quality. These amenities have served to increase urban development in the area and enhance North Liberty’s quality of life. As such, protection of these resources is an important goal.

A substantial amount of residential development has occurred within the Iowa river corridor, particularly within Iowa City and Coralville’s jurisdiction areas consistent with the County’s Comprehensive Plan. Urban services are not provided to these developments, as such private wells and on-site septic systems are used to service the development. On-site septic systems within the river and creek corridors present concerns with regards to their potentially harmful effects on water quality. The County has adopted polices and standards regarding such development. The City should also review all development requests within its extra territorial jurisdictional area to ensure adequate provisions for on-site septic systems are being implemented. In addition, the City should take an active role in subsequent inspections and pumping requirements for these developments. These reviews and inspections are in the best interest of North Liberty, as they will serve to protect the area’s natural amenities and safeguards against massive septic system failure in the North Liberty area. Such a failure may result in the costly extension of utilities to service failed developments.

New industrial development also raises concerns with water quality in the North Liberty area. City representatives have expressed concern over the potential that new industrial development should pose pollution and/or environmental concerns. This is particularly important with regards to water quality because of the valuable ecological and recreational aspects of these features within the North Liberty area. The City must carefully review industrial development requests within the City to ensure protection of the region’s water quality. In addition, site development of industrial uses should consider drainage patterns, ground water elevation, and other features which may impact water quality.

EROSION CONTROL/STEEP SLOPES

The Iowa River corridor in the North Liberty region contains a number of areas where slopes exceed 12 percent. Access and development in these areas is difficult and must be sensitive to the preservation of the natural vegetation and stabilization of slopes to prevent erosion.


Despite lacking significant slopes within the City limits, North Liberty must address the issues associated with steep slopes located within the extra territorial jurisdiction area. Although the County has adopted policies regarding such development, the City may wish to also review these proposals.

As development continues throughout the region, it is important that appropriate erosion control measures are undertaken. Within natural drainageways, the preservation of natural vegetation should be encouraged. This is of utmost importance in that vegetation protects the soil from erosion.

To the extent possible, the placement of houses and roads upon steep slopes should be avoided. Generally, the steeper the slopes, the greater the erosion hazard. Because of gravity and reduced friction between soil particles, it takes less energy to dislodge and transport soil. Grading plans for residential subdivisions must be carefully reviewed to eliminate excessive grading practices and if necessary, reduce the amount of allowed units to preserve slopes and vegetation.

As a means of minimizing the environmental impact of development requests in these areas, the City should include an evaluation of slopes on subject properties. Factors to be considered are: 1) percentage of grade, and 2) surficial soil type. Generally, slopes exceeding 12 percent should be examined for any potential environmental impact which might occur as a result of a proposed development. However, depending on the soil types involved, lesser slopes may also require attention.

Any development on land containing slopes in excess of 12 percent grade should be required to supply soil tests for review by the City Engineer. Furthermore, as current City standards require, applicable developments should submit an “erosion control plan” which would detail intended specific methods of erosion control.

VEGETATION

With the exception of the hilly areas within the Iowa River and Muddy Creek corridor, the North Liberty area is void of significant tree massings. Because wooded and natural area provide a unique character and a highly desirable amenity for both residential and recreational development, efforts should be made to retain, to the extent possible, all existing vegetation. Additionally, the City should continue its efforts promoting tree planting and preservation programs as well as efforts to require mandatory tree planting within all new subdivisions, both within the City limits and the extra territorial jurisdiction area. This could be accommodated through amending the Subdivision Ordinance.

FLOODPLAIN/STORM WATER MANAGEMENT

The Muddy Creek drainageway is utilized to accommodate storm water runoff from the City’s urban development. As development has increased within the City, the number and severity of high water situations along this drainageway has also increased. This raises concern with regard to potential flooding within North Liberty and in downstream communities. Additionally, some drainage problems exist within the older portions of the community as a result of surface water runoff and sump pump discharge.

As a means of protecting the public health and safety, and to minimize property damage and pollution from flood waters, the City and Johnson County have established Floodplain Overlay Districts. As a result, all development proposals which lie within the designated floodplain district should conform to a specific set of regulations and should be subject to additional review by the Iowa Department of Natural Resources, in the event of any proposed alteration of a watercourse. Failure to comply with state and federal standards for floodplain management will result in North Liberty area residents being unable to obtain Federal Flood Insurance.

In response to increased runoff resulting from urban development, the City has adopted a Comprehensive Storm Water Management Plan. This plan addresses storm water retention practices for new developments, the utilization of natural drainageways, and drainage issues related to existing development.

AIR AND NOISE POLLUTION

Transportation and industry are typically the major contributors to air and noise pollution in a community. Interstate 380 and Highway 965 are the greatest contributors to noise and air pollution in the City and the surrounding area. No air quality or noise problems exist at present with these roads, nor are they anticipated in the foreseeable future. Similarly, no air or noise pollution problems with regard to industrial activity have been identified in the City. A primary reason for this is the lack of heavy industrial/manufacturing facilities in the area.

Highway 965 was identified by many persons in the community survey as a source of noise pollution. This was mostly due to the rumble strips used to warn motorists of oncoming stop signs, as well as vehicular starting and stopping. New plans for the redesign of Highway 965 should address these concerns and attempt to facilitate speed reduction and other traffic calming devices.

City representatives have expressed concern over the potential that new industrial development could pose pollution and/or other environmental concerns. In order to alleviate sch concerns, careful consideration should be given in allocating land zoned for heavy industrial development. In addition, all new commercial and industrial development, including expansions, should comply with existing state and federal pollution emission standards. Careful review of such proposals, including an analysis of the pollution potential, should be conducted if concerns are present.

PRIME FARMLANDS

Prime farmlands cover almost the entire North Liberty area, with the exception of the Iowa river corridor. The prevalence of prime farmland suggests that agriculture will continue to been an important land use within the City and throughout the region. The rate of development and the demand for land make the preservation of agriculture land an unrealistic objective within the City boundaries. With this under consideration, an important aspect of the Comprehensive Plan is the concentration and staging of urban development to avoid premature elimination of these lands. Concentrating urban activities and focusing on infill development will aid in preserving contiguous farming operations within prime farmlands. This will result in minimizing land use conflicts and maintaining the economic viability of farming operations.

Another effort to protect prime farmlands is to limit residential development opportunities within agricultural zoning districts. Residential development should be limited to one dwelling unit per 40 acres. While the density of one per 40 should be observed, the minimum lot size of residential properties in agricultural zoned areas should allow parcels that are a minimum of one acre in size and a maximum of ten acres, with the balance of the property preserved as open space or protected agricultural activities. In addition, a deed restriction should be placed over parcels which have exercised these division rights. This will ensure that further development will not take place on the property unless it is rezoned.
 

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