Home>Economic Development>Comprehensive Plan Update>Full Text of the Comprehensive Plan>Dev. Framework: Natural Environment

JUNE 2005

2. NATURAL RESOURCES AND ENVIRONMENT

Natural environment areas are of prime importance to the community. Besides serving as aesthetic amenities that enhance the 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 as defined in the City’s Sensitive Areas Subdivision Design Standards resolution. Residents have expressed concerns with the preservation and enhancement of these features within the City limits, as well as the extra-territorial jurisdiction area.

In addition, the City Inventory document defines specific areas of concern with soil suitability, steep slopes, floodplains, significant mass vegetation, and prime farmland in and around North Liberty. The City should utilize the Inventory when updating specific land use tools, such as the Zoning, Subdivision and Environmentally Sensitive Areas Ordinances, as well as the Capital Improvement Plan.

2.1 Soil Suitability
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 changing 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 the 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.

2.2 Water Quality
A central feature within the North Liberty area is the Iowa River, and the reservoirs that 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 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 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 safeguard against massive septic system failure in the North Liberty area. Such a failure may result in the costly extension of utilities to service failed infrastructure.

New industrial development also raises concerns with water quality in the North Liberty area. Residents have expressed concern over the potential that new industrial development could pose pollution and/or environmental concerns. This is particularly important with 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 that may impact water quality.

2.3 Erosion Control and Steep Slopes
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 also wish to 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, with steeper slopes, there is a greater possibility of 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) surface soil type. Generally, slopes exceeding 12 percent should be examined for any potential environmental impact that 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.

2.4 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 areas 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, 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.

2.5 Floodplain and Stormwater Management
The Muddy Creek drainageway is utilized to accommodate storm water runoff from the City’s urban development. As the City has grown, the number and severity of high water situations along this drainageway has also increased. This raises concern with 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 floodwaters, 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 stormwater retention practices for new developments, the utilization of natural drainageways, and drainage issues related to existing development.

In addition, the City should prepare a floodplain study to establish a new 100-year floodplain for the community.

2.6 Air and Noise Pollution
Residents have expressed concern over the potential that new industrial development could pose pollution and/or other environmental concerns. In order to alleviate such 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.

2.7 Prime Farmland
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 be 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 actual City boundaries and future growth areas of the City. However, prime farmland outside of established future growth areas should be protected and preserved.

An important aspect of the Comprehensive Plan is the concentration and staging of urban development to avoid premature elimination of prime farmland. Concentrating urban activities and focusing on infill development will aid in preserving contiguous farming operations on prime farmland. 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 that 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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