Jonathan Edwards, Director
Planning@HanoverNH.org

Residential Zoning Project
Rural Study Group 2007

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Downtown Hanover Vision
Guiding Growth in Rural Hanover
'Something for Everyone' Scenic Locales Report
Class VI Roads In Hanover

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Zoning Board of Adjustment
Zoning Ordinance


Conservation
Conservation Commission
Open Space Priorities Plan
Trails
Flora and Fauna
Protected Lands

Affordable Housing
Affordable Housing Commission
Affordable Housing Study
Gile Tract Housing

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RPG Steep Slopes

 DRAFT July 27, 2005

OVERLAY RECOMMENDATION -
STEEP SLOPES

MASTER PLAN MANDATES
Core Principles (p.3-5)
1. Protect and preserve our natural resources: These include both urban and rural open space, wildlife habitat, water and wetlands, agricultural and forestry lands and associated recreational resources.

Chapter 3: Land Use and Community Vision (p. 3-5)
An important consideration in land use planning is using the concept of land capability to direct development to lands suitable for development and to recognize that structures are but one of several competing uses of land; other uses include groundwater recharge, habitat, open space, recreation, protection of steep slope stability and scenic vistas.  Not all land is suitable for building. Constrained land, such as wetlands which have low development value, and lands with important natural values, such as heavily-vegetated steep slopes, which control runoff and erosion and absorb pollutants, should be carefully considered as to whether they should be counted in density calculations.  To count these lands in density calculations based on acreage alone, without consideration of the suitability of that acreage to actually support development can result in granting to the development densities that may be quite inappropriate to the site.  Further, to drive up market value of inappropriate (undevelopable) lands leads to design challenges and land use quite unrelated to the nature of the site, and devaluation of the important environmental functions served by the ≥constrained≈ lands.  Degradation of the downstream habitats and decreased flow in streams are some secondary effects of ignoring these constraints.  For these reasons, environmentally sensitive lands of high resource value may be excluded in whole or in part from the calculation of development density.

Map 3-4:  Land Use Concept Map
Development should be excluded from environmentally sensitive lands of high resource value:  floodplains, wetlands (including hydric soils), headwaters of major streams, perennial stream courses and adjacent natural buffers, and steep slopes.  These lands may be excluded in whole or in part from the calculation of development density; Ó

 Chapter 4: Natural resources (p. 8)
* Steep Slopes can be defined by a grade or by a combination of grade and soil
type.   The combination of even a moderate (8 to 15%)  slope and a highly erodible soil, such as Hitchcock soil (which occurs in abundance in Hanover) is seen as a moderate to severe erosion hazard by the Natural Resources Conservation Service . . .

Chapter 5: Policies and Recommendations (p. 11)
* Protect fragile environmental areas, such as wetlands, aquifers, areas subject to flooding, steep slopes, and important wildlife habitats, from inappropriate types of land uses.
* Exclude from development sensitive lands of high resource value: (including) steep slopes. These lands can be excluded in whole or in part from the calculation of development density. This exclusion may be applied differently in areas served by the existing water and sewer infrastructure from those that are not (i.e. urban vs. rural areas)

    Steep Slopes
* Define steep slopes based on grade/soil characteristics explained in the Grafton County Soils Survey.
* Permit uses only of the sort recommended for these slopes and soils as outlined in the Grafton County Soils Survey.
* Prohibit development or disturbance of steep slopes where soils will not support such development.
* Establish planting standards for steep slopes requiring re-vegetation when grass is not sufficient to hold steep banks; shrubs and trees should be planted for long-term stability.
* Require retention of existing forest cover for steep slopes.
* Discourage lawns and encourage meadows and woody vegetation on sloping lands to help recharge groundwater on moderate slopes.
* Educate Hanover citizens about value of forest cover and meadows, and their value in groundwater recharge and watershed protection.
* Protect the tops of steep slope banks with a vegetative buffer.
* Require that any forest disturbance for development in rural areas to be kept to a minimum; aim for a goal of 65% forest cover in these areas. 

DENSITY CALCULATIONS PRACTICED IN OTHER NEW HAMPSHIRE TOWNS, AND RECOMMENDATIONS FROM RANDALL ARENDT
Steep Slope Definition >25%
        Omit 100% of steep slopes : (Plainfield,  Newbury, Thetford [for PRDs], New
          London, Hollis  & Lebanon)
        Omit 80% of steep slopes: (Grantham)
        Omit 75% of steep slopes (Randall Arendt)

Steep Slope Definition >20%
        Omit 100% of steep slopes: Bennington 
        Omit 80% of steep slopes:  (Lyme) 
       
From New London, NH
D. Special Exceptions: A Special Exception may be granted by the Zoning Board of Adjustment after proper public notice and hearing for Development in the Steep Slope Overlay District to avoid or minimize Development in the Wetland Conservation Overlay District. Such applications shall be referred to the Conservation Commission for review and comment prior to the hearing. In addition to the usual criteria used by the Zoning Board of Adjustment in evaluating an application for a Special Exception, the applicant must demonstrate to the Zoning Board of Adjustment that:
1) no reasonable alternative exists which affects neither the Steep Slope Overlay District nor the Wetlands Conservation Overlay District;
        2) the encroachment into the Steep Slope Overlay District is the least amount
         needed to avoid or minimize Development in the Wetlands Conservation Overlay
         District; and
        3) by encroaching into the Steep Slope Overlay District, the proposed
         Development would impact the environment less adversely than if the
         Development avoids the Steep Slope Overlay District and encroaches only into
         the Wetlands Conservation Overlay District, as otherwise required by this
         provision.

From Hollis, NH
2. Standards pertaining to construction on slopes, hillsides and/or ridgeline situations.
a. Place building sites (structures plus the lawn area cleared of trees) and aboveground utilities downgrade of the ridge line whenever possible, and locate them so they do not interfere with the identified characteristic or view or vista identified in the course of Planning Board review. The recommended minimum setback from a ridgeline is 50 feet: however, the Planning Board can modify this requirement when doing so does not detract from the purpose of this ordinance, and mitigation measures, such as plantings or topographical features, effectively screen the building site from public view.

RECOMMENDATIONS FOR HANOVER
2. Steep Slopes Conservation District:  The purpose is to limit the intensity of development of steep slopes so to prevent adverse soil erosion during and after construction; to protect surface waters from increased sedimentation, storm water runoff, and contamination from sewage disposal systems, to protect the Town≠s infrastructure from runoff and flood damage; to protect wildlife, natural habitat and ecological balance; to preserve tree and vegetative cover; to protect scenic views; and to avoid subsequent escalating cost to the public of private or institutional development.

a) Definition: The Steep Slopes Conservation District is defined as comprising all areas where slopes exceed 20% (defined as any reach where there is a rise of 20-feet, and the average slope is 20% or greater). For Hitchock soils (and similar sensitive soils), steep slopes are slopes that exceed 15%
b) Density Calculation: 100% of steep slopes over 25% are excluded from area available for density calculations. 100% of steep slopes over 15% in Hitchcock and similar sensitive soils are excluded. 50% of steep slopes over 20% grade in other less sensitive soils are excluded .
c) Building Envelope: No buildings allowed on slopes greater than 25%. Building on slopes between 20% and 25% limited by special exception.
d) Rules for special exceptions: A Special Exception may be granted by the Zoning Board of Adjustment if the applicant demonstrates that:
1) no reasonable alternative exists which affects neither the Steep Slope Overlay District nor any other Overlay Districts. Applicant must show minimization of impact on slopes between 20% and 25% through location of structures and the amount of area disturbed;
2) the encroachment into the Steep Slope Overlay District is the least amount needed to avoid or minimize Development in the Wetlands Conservation Overlay District; [Note: This argument may be extended later to other overlay districts deemed of high priority]
3) by encroaching into the Steep Slope Overlay District, the proposed
          Development would impact the environment less adversely than if the
Development avoids the Steep Slope Overlay District and encroaches only into the Wetlands Conservation Overlay District, as otherwise required by this provision; ; [Note: This argument may be extended later to other overlay districts deemed of high priority]
4) the impact on the Forest cover is minimized in the steep slope area. No trees are to be removed to provide for lawns, gardens, scenic views in the steep slope district;
5) disturbance of natural terrain is minimized in the steep slope area, excepting for controlling surface storm water flow
6) surface storm water flow is to be directed to recharge ground water, and there is no net increase in flow and flow rates off site;
7)  the building sites are located so they do not interfere with the scenic views.

Ed Chamberlain
Anne Morris