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Calcimator

Heritage Impact Assessment Calculator

Impact scoring for changes to historic properties.

Inputs

Results

Impact score (0-5)

2.2

Impact %44
Risk (0=Minor, 3=Severe)1
Mitigation level (0-3)1
How to Use This Calculator
  1. Score Architectural impact (0=none, 5=severe) based on how much the proposed work alters character-defining exterior features.
  2. Rate Historical significance impact and Visual/setting impact for effects on the property's historic context and setting.
  3. Enter Archaeological impact if subsurface disturbance is planned near potential archaeological resources.
  4. Score Reversibility (0=fully reversible, 5=permanent) to reflect how easily the changes could be undone in the future.
  5. Review the weighted Impact score (0–5) and Risk level (0=Minor to 3=Severe) to determine SHPO consultation needs.
  6. Use the Mitigation level output to identify what avoidance, minimization, or mitigation measures are required.

How the result changes with Historical significance (0-5)

Historical significance (0-5)Impact score (0-5)
0.51.58
1.751.89
3.252.26
4.52.58

What each input means

Architectural impact (0-5)
Impact on architectural character (0=none, 5=severe).
Historical significance (0-5)
Impact on historic significance and integrity.
Archaeological impact (0-5)
Potential impact on archaeological resources.
Visual/setting impact (0-5)
Impact on the visual setting and context.
Reversibility (0-5)
Irreversibility of proposed changes (0=fully reversible, 5=permanent).

What each result means

Impact score (0-5)
Weighted heritage impact score.
Impact %
Impact score as percentage of maximum.
Risk (0=Minor, 3=Severe)
0=Minor, 1=Moderate, 2=Major, 3=Severe.
Mitigation level (0-3)
0=None, 1=Standard, 2=Enhanced, 3=Maximum.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Architectural impact (0-5) = 2, Historical significance (0-5) = 3, Archaeological impact (0-5) = 1, Visual/setting impact (0-5) = 2 = 5 input(s) provided
  2. Calculate Impact score
    Impact score = round(weightedScore * 100) / 100
    2.2 = 2.2
  3. Calculate Impact %
    Impact % = round((totalScore / maxScore) * 10000) / 100
    44 = 44
  4. Calculate Risk
    1 = 1

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