cv300x block 3 key terms and lesson objs

What is an exposure pathway?

The complete physical connection between a contaminant sources and a human receptor, through a,

(release mechanism : physical or chemiscal process where contaminant leaves source and enters envrionment

transport medium : envrionmental material that carries relased contaminant away from source

exposure point : specific place of area where organisms come into contact with contaminant

exposure route : biological pathway that contaminant enters receptors body)

All four elements must exist for exposure to be calculated through the pathway.

What is Chronic daily intake (CDI)

The body weight normalized daily intake used for the chronic exposure calculation. Intake is averaged across lifetime and expressed as units of mg/kg per day

What is slope factor?

A toxicity value used to estimate an upper-bound lifetime probability of developing cancer per unit of lifetime-average daily intake. Oral slope factors have units of (mg/kg per day)^-1

What is excessive lifetime cancer risk?

The estimated probability of cancer attributable to the modeled exposure above the background probability that already exists in the population. Calculated by multiplying the CDI by the oral slope factor.

What is the NCP Risk range:

the 10^-6 to 10^-4 excess upper-bound lifetime cancer-risk range generally used in CERCLA remedy settings for known or suspected carcinogens. the lower bound (10^-6) serves as a point of departure for remediation goals when applicable requirements are unavailable or insufficiently protective.

What is expected failure frequency / number of disrupted events E[N']?

The expected number of times a services is expected to be disrupted

represented by the equation : λ * P fail

λ = initiating cause frequency. Rate or probability that a specific threat, hazard, or initiating event happens.

P fail = probability that a system or its engineered safeguards fail to perform their intended function in the case of an initiated event.

What is expected total downtime E[H]?

Expected total duration of service disruptions over a period.
Equation: E'[N'] * d

E[N] =λ*P fail

d= duration

What are spatial boundaries?

The geographic extent dependent on the infrastructure service.

For example, if a water treatment plant stopped working, it could impact the entire city downstream.

What are temporal boundaries

The time horizon and operational windows under analysis. It accounts for the peak and off peak demand cycles, seasonal vulnerability, and time required for system restoration.

Cover lesson obective 1

Failure modes and effects analysis (FEMA)

Structured, proactive reliability tool used to identify:

• potential failure modes (how system can fail)

• effects of failure (what happens to public/system when it fails)

• causes of failure (what triggers the failure). Allows engineers to rank risks.

How to justify design responses?

When expected total downtime is too high, engineers implement design responses:

Redundancy: adding backups to lower P fail

Hardening: strengthening components to lower λ (probability of failure)

capacity / buffer adjustments: shorten d (duration) with faster repair times

Risk acceptance: authorities explicitly decide to accept residual risk.

What is Value of Statistical Life (VSL)

The monetary tradeoff between reducing a mortality risk and money. It is not a dollar value for saving a life, instead, it measures how willing society is to pay for safety features that would statistically save one life

What is cost of illness (COI)

Total economic burden imposed by a disease, injury, or health condition.
comprised of, direct costs (medical care) + indirect costs (lost wages).

What is net social cost

The total negative impact (cost) subtracted against the positive impacts (benefits) that society expereinces when projects or policies are expressed monetarily.

What is the break even threshold.

The tipping point or value of an uncertain value , where the preferred design alternative flips to a different one.

What is cost recovery?

The practice and degree where an infrastructure system generates enough revenue to offset all its associated costs. Full cost recovery includes day-to-day operations / routine maintenance, as well as debt service, emergency reserves, depreciation, upgrades, and decommissioning.

What is a revenue mechanism?

The formal institutional way to capture money flows to an asset:

E.g., tariffs, tolls, tax appropriations.

What is willingness to pay?

The max amount of money an individual is willing to sacrifice to receive or continue using a specific infrastructure capability. WTP reflects perceived utility , fairness, quality of life, and available substitutes.

What is Ability to pay

The socioeconomic capacity or financial ability of a household or consumer to afford infrastructure rates without compromising their needs.