diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/00-document-info.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/00-document-info.mdx
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+---
+title: Document Info
+reportDate: October 2026
+reportType: Technical Reference
+reportTitle: Backward Erosion Piping Screening Technical Reference Manual
+reportSubTitle: System Response Library
+reportAuthors: ['Adam Gohs, P.E.']
+reportAbstract: Technical reference documenting the Backward Erosion Piping (BEP) screening model in the System Response library. The model computes a system response probability (SRP) for backward erosion piping at each headwater level using a seven-node event tree. The probability of a continuous foundation flaw is estimated by Bayesian updating of a geology-based prior with subsurface and seepage-observation evidence. Unfiltered-exit and initiation probabilities are computed from blanket theory with a companion defect-survival model for the downstream confining layer, and progression is evaluated with the Schmertmann critical-gradient method. The model applies simplifications appropriate for screening-level risk analysis.
+reportSubjectTerms: ['BEP', 'Backward Erosion Piping', 'Screening', 'Event Tree', 'System Response Probability', 'System Response Curve', 'Blanket Theory', 'Bayesian Updating', 'Schmertmann Method', 'Monte Carlo']
+citationGuide: 'U.S. Army Corps of Engineers, Risk Management Center, Backward Erosion Piping Screening Technical Reference Manual, Lakewood, CO: U.S. Army Corps of Engineers, Risk Management Center, 2026.'
+---
+
+import Link from '@docusaurus/Link';
+import DocumentMetadata from '@site/src/components/DocumentMetadata';
+import NavContainer from '@site/src/components/NavContainer';
+
+
+
+# Document Information
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/00-version-history.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/00-version-history.mdx
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+---
+title: Version History
+---
+
+import NavContainer from '@site/src/components/NavContainer';
+import TableVersionHistory from '@site/src/components/TableVersionHistory';
+
+
+
+# Version History
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/01-preface.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/01-preface.mdx
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@@ -0,0 +1,47 @@
+---
+title: Preface
+---
+
+import NavContainer from '@site/src/components/NavContainer';
+
+
+
+# Preface
+
+This document provides a technical reference for the Backward Erosion Piping (BEP) screening model in the System Response library. The model
+computes a system response probability (SRP) as a function of headwater elevation for the backward erosion piping failure mode. It is a screening-level
+model: it applies simplifications intended to reduce input burden while avoiding false negatives, and any application that performs screening-level
+risk analysis can use it.
+
+The intended audience includes dam and levee safety engineers evaluating whether the model is appropriate for their assessment, and peer reviewers
+checking the technical basis of screening-level results. Readers are assumed to have a general background in internal-erosion risk analysis —
+event trees, seepage mechanics, and probability concepts — but no familiarity with the software implementation is required.
+
+The document covers the model's complete execution pathway: the evidence-based assessment of a continuous foundation flaw, the resolution of
+hydraulic loading and seepage-path geometry from the site inputs, the assembly of the seven-node event tree at each pool level, the assumptions
+made along the way with their engineering bases, the inputs the user provides and the options available, and the results the model produces.
+
+## Document Organization
+
+- **[Model Overview](./02-model-overview.mdx)** — The model's purpose and intended use, a summary of its execution pathway from inputs to
+ results, its physics basis, a comparison with the full toolbox models, the exit pathways evaluated and when each exists, and its relationship
+ to the toolbox models.
+- **[Input Parameters](./03-input-parameters.mdx)** — Every user input: hydraulic loading, embankment geometry, upstream blanket, downstream
+ seepage berm, flaw-evidence selections, confining-layer characterization, observed-seepage refinements, embankment materials, foundation sand
+ properties, unit weights, and the intervention and breach probabilities, with units, valid ranges, defaults, and the choices available for
+ each selection.
+- **[Flaw Assessment](./04-flaw-assessment.mdx)** — The Bayesian assessment of the probability that a continuous path of fine to medium, uniform
+ sand exists in the foundation: the geology-based prior, the subsurface-data and seepage-observation evidence updates, and the uncertainty
+ quantification.
+- **[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)** — The downstream reference elevations, the treatment of
+ tailwater, the net driving head, the resolution of the upstream, embankment, and downstream seepage path lengths, and the selection between the
+ two blanket-theory configurations.
+- **[Event Tree](./06-event-tree.mdx)** — The seven event-tree nodes, how each probability is populated at each pool level (including the
+ composition of the unfiltered-exit node from the defect and blowout pathways), and how the SRP and the governing system response curve are
+ computed.
+- **[Delegated Methods](./07-delegated-methods.mdx)** — For blanket theory and the Schmertmann progression method: the event-tree node each
+ serves and the question it answers there, the chapter of the dedicated manual that documents it, and each screening-level adjustment.
+- **[Assumptions and Limitations](./08-assumptions-and-limitations.mdx)** — Each modeling assumption with its engineering basis, its effect on
+ results, and the conditions under which it may not hold.
+- **[Output and Interpretation](./09-output-and-interpretation.mdx)** — The results the model produces, how to read the system response curve,
+ how the governing pathway is determined, how key inputs affect the SRP, and the role of screening results relative to detailed analysis.
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/02-model-overview.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/02-model-overview.mdx
new file mode 100644
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+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/02-model-overview.mdx
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+---
+title: Model Overview
+---
+
+import Citation from '@site/src/components/Citation';
+import CitationFootnote from '@site/src/components/CitationFootnote';
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Model Overview
+
+## Purpose
+
+The BEP screening model computes a system response curve for the backward erosion piping failure mode as a function of headwater elevation.
+The system response probability (SRP) at each headwater level represents the conditional probability of dam or levee breach due to backward
+erosion piping, given that pool level. The model produces a curve of SRP values across a range of headwater elevations that
+characterizes the structure's vulnerability to this failure mode.
+
+Backward erosion piping is the progressive removal of cohesionless foundation soil by seepage, beginning at an unfiltered downstream exit and
+eroding backward (upstream) beneath the embankment until a continuous pipe connects the impounded water to the exit. The failure mode requires a
+continuous path of erodible material, an unfiltered exit, sufficient gradient to initiate erosion, a soil roof that keeps the developing pipe
+open, and sufficient gradient to advance the pipe to the reservoir.
+
+## Intended Use
+
+The model is a screening-level assessment of backward erosion piping risk. It makes simplifying and generally conservative assumptions with two
+goals:
+
+- **Preventing false negatives** — The model is designed to avoid underestimating risk at the screening level, so that structures with
+ potential BEP concerns are flagged for further analysis.
+- **Reducing input burden** — The model requires fewer inputs than the full BEP toolbox models. Qualitative selections (confining-layer
+ thickness category, relative density category, geologic environment) substitute for site-specific distributions, and default distributions
+ cover material properties that are typically unavailable at the screening stage. Where a site characteristic is genuinely unknown — the
+ presence of a confining layer, or the extent of that layer beyond the embankment — the model accepts Unknown as an answer and substitutes a
+ deliberately wide characterization rather than requiring the user to guess.
+
+The model is not intended for detailed or semi-quantitative risk assessments. For higher-level analyses, the full BEP Initiation and BEP
+Progression toolbox models provide the complete methodologies with full parameterization (see
+[Comparison with Detailed Models](#comparison-with-detailed-models)).
+
+## How the Model Works
+
+The screening model executes three stages:
+
+1. **Flaw assessment** — A Bayesian analysis estimates the probability that a continuous path of fine to medium, uniform sand exists in the
+ foundation. A prior probability based on the geologic depositional environment is updated with subsurface-data evidence and observed-seepage
+ evidence when available. The mean posterior probability populates the first event-tree node and is independent of pool level
+ (see [Flaw Assessment](./04-flaw-assessment.mdx)).
+
+2. **Hydraulic and seepage-geometry resolution** — The model resolves the downstream reference elevations that control net driving head, the
+ upstream seepage path length $L_1$, the embankment base width $L_2$, and the downstream seepage path length $L_3$ from the site inputs, and
+ selects the blanket-theory configuration — Case 2 when an upstream seepage barrier is credited with an upstream path length, Case 4
+ otherwise
+ (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+
+3. **Event-tree assembly** — At each headwater level, the model composes seven node probabilities and multiplies them to produce the SRP. Blanket
+ theory computes the blowout and heave probabilities feeding the unfiltered-exit and initiation nodes, a defect-survival relationship gives the
+ probability that a pre-existing defect already penetrates the confining layer, and the Schmertmann critical-gradient method computes the
+ probability of pipe progression. The blanket-theory and Schmertmann analyses are evaluated by Monte Carlo simulation over the uncertain
+ material and geometric inputs (see [Event Tree](./06-event-tree.mdx) and [Delegated Methods](./07-delegated-methods.mdx)).
+
+## Physics Basis
+
+The model combines the following engineering methods:
+
+- **Bayesian updating in log-odds form** for the probability of a continuous foundation flaw, combining a geology-based prior with likelihood
+ ratios for the site evidence (see [Flaw Assessment](./04-flaw-assessment.mdx); the source of the formulation is requested at marker IN-18)
+- **Blanket theory** for the excess head beneath the downstream confining layer and the vertical exit gradient through it, from which the
+ blowout and heave probabilities follow
+- **A Weibull defect-survival relationship** for the probability that a pre-existing defect fully penetrates the confining layer (see
+ [Event Tree](./06-event-tree.mdx))
+- **Roof-support probabilities by soil classification** for the mechanical condition of pipe progression
+- **The Schmertmann critical-gradient method** for the hydraulic condition of pipe progression , with
+ an exit-geometry factor that distinguishes concentrated from distributed exits
+
+## Comparison with Detailed Models
+
+The detailed counterparts of the screening model are the full BEP Initiation and BEP Progression toolbox models. The BEP Initiation manual
+covers all eight blanket-theory configurations (see its [General Overview](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/general-overview)), of which the screening model uses
+[Blanket Theory Case 2](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-2) and [Blanket Theory Case 4](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-4). The BEP Progression manual covers the
+[Schmertmann](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann) method used by the screening model and the alternative [Sellmeijer](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/sellmeijer) method.
+ summarizes the differences.
+
+
+
+## Exit Pathways
+
+The model evaluates up to two seepage exit pathways:
+
+- **Toe pathway** — Seepage exits at the downstream toe of the embankment, or at the toe of the downstream seepage berm when one is present.
+ This pathway is always evaluated. When a confining layer may be present and the toe exit remains beneath it — no berm, or a berm ending
+ within the layer's known extent — the unfiltered-exit probability at the toe is composed from two mechanisms (a pre-existing defect through
+ the layer, and hydraulic blowout of the layer), and the initiation probability is the blanket-theory heave probability. Where a berm instead
+ places the exit at or beyond the layer's downstream termination, the exit daylights at the berm toe and the unfiltered-exit and initiation
+ probabilities are certain there.
+
+- **Daylight pathway** — Seepage exits at the downstream termination of the confining layer, where the underlying sand daylights at the ground
+ surface. This pathway is evaluated whenever a confining layer may be present (its presence is confirmed or unknown) *and* the daylighting
+ exit is distinct from the toe exit. At the daylight exit there is no confining layer to penetrate, so the unfiltered exit is certain, and
+ initiation is certain whenever the pool stands above the exit level and drives seepage out of the sand. With no berm, or with a berm inside a
+ confirmed layer's known extent, the daylight pathway is also distinguished by its longer seepage path to the exit. When a berm reaches or
+ clears a confirmed layer's downstream extent, overlies a confirmed layer whose extent is unknown, or overlies a layer of unknown presence,
+ the berm toe is itself the daylighting exit: the toe pathway then represents that exit directly, and no separate daylight pathway is
+ evaluated (see [Event Tree](./06-event-tree.mdx)).
+
+The governing SRP at each headwater level is the larger of the two pathway SRPs, so the more critical exit condition controls the screening
+result. When only the toe pathway is evaluated, it governs directly.
+
+## Relationship to Toolbox Models
+
+The screening model uses the same blanket-theory and Schmertmann methods as the standalone toolbox models for its blowout, heave, and
+progression computations. The screening model differs only in what it supplies to
+them: it builds their geometry and material inputs from the screening selections and fixes several choices that the toolbox models leave to
+the analyst (). [Delegated Methods](./07-delegated-methods.mdx) documents each fixed choice
+and its basis.
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/03-input-parameters.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/03-input-parameters.mdx
new file mode 100644
index 000000000..5f8b8f6af
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/03-input-parameters.mdx
@@ -0,0 +1,494 @@
+---
+title: Input Parameters
+---
+
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Input Parameters
+
+This chapter documents every user input to the BEP screening model. Inputs are organized into eleven groups: hydraulic loading, embankment geometry,
+upstream blanket, downstream seepage berm, foundation flaw evidence, confining-layer characterization, observed-seepage refinements, embankment
+materials, foundation sand properties, unit weights, and the intervention and breach probabilities. Each group gives the short facts for its
+quantities in a table, followed by a description of each input and, for selections, a list of the available choices and what each implies.
+
+Several inputs are statistical distributions that characterize uncertainty in a physical quantity. A distribution input may take any of five
+forms: a deterministic (single) value, a uniform distribution between a low and high bound, a normal distribution (mean and standard deviation),
+a triangular distribution (low, mode, high), or a PERT distribution (low, mode, high). Any distribution may also carry a lower limit, an upper
+limit, or both; a sampled value beyond a limit is set to that limit. The Monte Carlo analyses described in
+[Delegated Methods](./07-delegated-methods.mdx) sample these distributions. Geometric seepage-path lengths — the upstream blanket length, the berm
+length, and the confining-layer extents — are the exception: a known length is a site measurement entered as a single value. The blanket
+length, berm length, and upstream extent are required where they apply. Only the downstream extent may be left blank when it is unknown, and
+the model then substitutes the wide default characterization documented in
+[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx).
+
+## Hydraulic Loading
+
+The hydraulic loading is defined by a headwater series and an optional companion tailwater series
+(). The model evaluates the event tree at every supplied headwater value and at additional
+pool levels distributed between them, with the tailwater at each additional level interpolated linearly between the supplied pairs.
+
+
+
+- **Headwater elevation series** — The pool elevations that define the range of hydraulic loading to be evaluated. A headwater value supplied
+ more than once is evaluated once, with its first paired tailwater.
+- **Tailwater elevation series** — Tailwater elevations paired one-to-one with the headwater series. The entire series may be omitted (no
+ tailwater at any pool level), or individual stages may be left blank (no tailwater at that pool level). Wherever no tailwater exists, the
+ downstream ground surface controls the net head, as described in
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx).
+
+## Embankment Geometry
+
+The embankment cross-section is described by its crest and by slope-segment tables for the upstream and downstream faces
+(). Each face is a sequence of one or more segments ordered from the crest down to the toe;
+each segment is defined by its bottom elevation and its slope, expressed as horizontal run per unit of vertical rise (H:V). Multiple segments
+accommodate compound slopes and intermediate benches.
+
+c', 'Wc', '—', '—', 'Eday'],
+ ['ft', 'ft', 'ft, H:V', 'ft, H:V', 'ft'],
+ [
+ 'Above the downstream toe',
+ '> 0',
+ 'One or more segments; slopes > 0',
+ 'One or more segments; slopes > 0',
+ 'Any elevation',
+ ],
+ ['None (required)', 'None (required)', 'None (required)', 'None (required)', 'Toe reference elevation'],
+ ]}
+/>
+
+- **Crest elevation** $E_c$ — Elevation of the embankment crest.
+- **Crest width** $W_c$ — Width of the embankment crest.
+- **Upstream face slope segments** — Bottom elevation and slope of each upstream face segment, ordered from the crest to the toe.
+- **Downstream face slope segments** — Bottom elevation and slope of each downstream face segment, ordered from the crest to the toe. The
+ lowest segment elevation defines the downstream toe, which must lie below the crest.
+- **Daylight ground-surface elevation** $E_{day}$ — Ground-surface elevation at the downstream termination of the confining layer, where the
+ foundation sand daylights. It may lie above or below the embankment toe. When it is left blank, the daylight exit is assumed to share the toe
+ reference elevation (the berm toe when a berm with a specified toe elevation is present, otherwise the downstream embankment toe). It sets the
+ exit level that controls the driving head for the blowout, heave, and daylight progression analyses; the blowout and heave net head is still
+ measured against the water standing on the layer at the toe or berm toe. When the daylighting exit is the berm toe itself, a supplied value
+ is not used, because the berm-toe reference elevation is then the exit datum (see
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+
+Three geometric quantities are derived from the cross-section rather than entered directly:
+
+- **Downstream toe elevation** $E_{toe}$ — the lowest bottom elevation among the downstream face segments.
+- **Embankment base width** $L_2$ — the crest width plus the horizontal projections of the upstream and downstream faces from the crest to
+ their respective toes. This is the embankment component of the seepage path. A downstream seepage berm is *not* part of $L_2$; it extends the
+ downstream seepage path beyond the toe instead (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+- **Embankment height** $H_d = E_c - E_{toe}$ — used to scale the downstream seepage path when no berm is present and the confining-layer extent or presence is unknown.
+
+## Upstream Blanket
+
+An engineered impervious blanket extending upstream of the embankment lengthens the seepage path and reduces gradients at the downstream exit
+(). When an upstream blanket is present, the blowout and heave analyses use Blanket
+Theory Case 2, which represents impervious strata on both sides of the embankment (see
+[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+
+1'],
+ ['—', 'ft'],
+ ['—', '> 0'],
+ ['No', 'None (required when present)'],
+ ]}
+/>
+
+- **Upstream blanket present** (Yes or No) — Whether an engineered impervious blanket extends upstream of the embankment toe.
+- **Upstream blanket length** $L_1$ — Length of the blanket measured from the upstream embankment toe, entered as a single value. It serves
+ directly as the upstream seepage path length $L_1$.
+
+## Downstream Seepage Berm
+
+A downstream seepage or stability berm moves the seepage exit beyond the berm. The model credits no berm weight in the blowout and heave
+factors of safety, which depend on the confining-layer thickness alone
+(). Its effect on the event tree depends on where the berm ends relative to the confining
+layer: a berm ending within a confirmed layer's known extent retains the through-layer exit mechanisms, evaluated at the berm toe, while a
+berm that reaches or clears the layer's extent — or overlies a confirmed layer of unknown extent, or a layer of unknown presence — is assumed to produce a daylighting
+exit at the berm toe, where the unfiltered exit is certain. Every berm lengthens the toe progression path. The full rules are documented in
+[Event Tree](./06-event-tree.mdx) and [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx).
+
+b', 'Ebt'],
+ ['—', 'ft', 'ft'],
+ ['—', '> 0', 'Any elevation'],
+ ['No', 'None (required when present)', 'Downstream embankment toe elevation'],
+ ]}
+/>
+
+- **Berm present** (Yes or No) — Whether a downstream seepage or stability berm is present.
+- **Berm length** $L_b$ — Length of the berm measured from the downstream embankment toe.
+- **Berm-toe ground-surface elevation** $E_{bt}$ — Ground-surface elevation at the downstream toe of the berm. When provided, it becomes the toe
+ reference elevation for the net head on the toe progression pathway. When it is left blank, the ground beneath the berm is assumed flat and
+ the berm toe shares the downstream embankment toe elevation. It is ignored when no berm is present.
+
+## Foundation Flaw Evidence
+
+The probability that a continuous path of fine to medium, uniform sand exists in the foundation is assessed from three categories of evidence:
+the geologic setting, subsurface data, and seepage observations. The way the evidence combines, and the probability range behind each
+choice, are documented in [Flaw Assessment](./04-flaw-assessment.mdx).
+
+**Geologic depositional environment** (required) — The depositional setting of the foundation soils. It selects the prior probability range for
+the continuous-flaw assessment; environments that deposit laterally continuous, uniform fine sands carry higher priors. The choices are:
+
+- Glacial outwash
+- High-energy fluvial systems
+- Coastal shoreface and barrier systems
+- Aeolian dune systems
+- Delta deposits
+- Alluvial fans
+- Shallow marine shelf
+- Low-energy deltaic and coastal mud systems
+- Residual soils
+- Unknown — the depositional setting has not been established; a moderate, deliberately broad prior applies
+
+**Subsurface data available** (Yes or No) — Whether borings, cone soundings, geophysics, or comparable subsurface information inform the flaw
+judgment. When no subsurface data is available, the two selections below are not used.
+
+**Strength of evidence** (required when subsurface data is available) — The degree to which the subsurface data supports or refutes the presence
+of a continuous fine sand layer. The choices are:
+
+- Very strong — the data strongly indicates a continuous layer; the flaw probability increases most
+- Strong — the data indicates a continuous layer
+- Moderate — the data modestly indicates a continuous layer
+- Neutral — the data neither supports nor refutes a continuous layer; the flaw probability is unchanged
+- Weak — the data tends to indicate that no continuous layer exists; the flaw probability decreases
+- Very weak — the data strongly indicates that no continuous layer exists; the flaw probability decreases most
+
+**Subsurface data quality** (required when subsurface data is available) — The quality of the data behind the strength-of-evidence judgment:
+extent of coverage, sampling method, and reliability. The choices are:
+
+- High — the evidence receives full weight
+- Moderate — the evidence is partly discounted toward neutral
+- Low — the evidence is discounted most strongly toward neutral
+
+**Seepage observed** (Yes or No) — Whether seepage has been observed downstream of the embankment during past loading events.
+
+**Seepage observation type** (required when seepage has been observed) — The character of the observed seepage. More localized,
+sediment-carrying signatures are stronger evidence of a continuous transmissive flaw than diffuse wet areas. The choices are:
+
+- Sand boils — the strongest seepage evidence of a continuous flaw; also enables the observed-seepage refinements below
+- Concentrated seepage — the next strongest evidence; also enables the observed-seepage refinements below
+- Stage-dependent wet areas — wet areas that respond to pool level; weaker evidence than concentrated seepage
+- Stage-independent wet areas — wet areas that do not respond to pool level; close to uninformative
+
+## Confining-Layer Characterization
+
+The downstream confining layer — a fine-grained stratum overlying the foundation sand on the landside — controls whether seepage can exit
+unfiltered at the toe. The presence, the thickness category, the permeability, and the upstream-extension question are each required where they
+apply, and Unknown is a valid answer to each.
+
+**Confining layer presence** (required) — Whether a confining layer overlies the foundation sand downstream of the embankment. The choice is
+deliberately three-way, so that a layer whose presence cannot be established is neither ignored nor fully credited:
+
+- Yes — the layer is confirmed. The defect and blowout analyses run with the selected thickness category, and the layer itself is credited as
+ the roof for pipe progression.
+- No — there is no layer. Seepage exits unfiltered at the toe with certainty, and only the toe pathway is evaluated.
+- Unknown — the layer may be present. The Unknown thickness band applies (no thickness category is asked), roof support is evaluated from the
+ embankment materials, and both exit pathways are evaluated.
+
+**Confining layer thickness category** (required when the presence is Yes) — The qualitative thickness of the layer, chosen by the analyst
+from borings or geologic mapping. The choices are:
+
+- Very Thin, Thin, Moderate, or Thick — each maps to a uniform thickness range ()
+- Unknown — no thickness information exists; the broad Unknown band applies
+- Custom — the user supplies a site-specific thickness distribution, in feet, that cannot produce negative values
+
+**Confining layer permeability** (required when the presence is Yes) — The permeability character of the layer, which decides whether it can
+act as an upstream seepage barrier (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)). The choices
+are:
+
+- Impervious — the layer can be credited as an upstream seepage barrier
+- Semi-pervious — the layer contributes no upstream head loss
+- Unknown — the layer contributes no upstream head loss
+
+**Confining layer extends upstream** (asked when the presence is Yes, the permeability is Impervious, and no upstream blanket is present) —
+Whether the confirmed impervious layer continues upstream beneath the reservoir. An engineered upstream blanket takes precedence as the upstream
+barrier, so the question is not asked when one is present. The choices are:
+
+- Yes — the layer is treated as the upstream seepage barrier and its upstream length is entered; a Very Thin layer is credited with zero
+ upstream length and so uses Blanket Theory Case 4
+- No — no upstream head loss is credited
+- Unknown — no upstream head loss is credited
+
+The two confining-layer extents are entered as single lengths ().
+
+1 (when credited)', 'Lcl'],
+ ['ft', 'ft'],
+ ['≥ 0', '> 0'],
+ ['None (required when the layer extends upstream)', 'Unknown'],
+ ]}
+/>
+
+- **Upstream confining layer length** — Length of the layer beyond the upstream embankment toe. It is required when the layer extends
+ upstream. It is credited directly as the upstream seepage path $L_1$, except for a Very Thin layer, which is credited with $L_1 = 0$ (see
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+- **Downstream confining layer length** $L_{cl}$ — Length of the layer beyond the downstream embankment toe, which is the distance to the
+ daylight exit. Leaving it blank means the extent is unknown:
+ - With no berm, the downstream seepage path is characterized by a wide default range scaled to the embankment height (see
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+ - With a berm over a confirmed layer, a daylighting exit is assumed at the berm toe.
+- When a berm is present over a confirmed layer, a supplied extent also decides whether the berm end remains beneath the layer (retaining the
+ through-layer exit mechanisms, evaluated at the berm toe) or reaches and clears it (producing a daylighting exit at the berm toe; see
+ [Event Tree](./06-event-tree.mdx)).
+- As a seepage-path length, a supplied downstream extent is used only when the presence is Yes. When the presence is Unknown, the wide default
+ range applies to the no-berm path regardless, and any berm is taken to end the layer at the berm toe.
+
+
+
+Each qualitative thickness category maps to a uniform distribution of confining-layer thickness $z_{bl}$ over the range in
+.
+
+:::warning[INPUT NEEDED IN-01 — Engineering Basis]
+The thickness ranges assigned to the qualitative confining-layer categories (Very Thin 0–5 ft, Thin 5–10 ft, Moderate 10–20 ft, Thick
+20–35 ft, Unknown 0–10 ft) require an engineering basis. Provide a literature citation (to be added to the bibliography) or the
+engineering-judgment attribution to state here, including the reasoning for the Unknown band spanning 0–10 ft.
+:::
+
+## Observed-Seepage Refinements
+
+When sand boils or concentrated seepage have been observed, two additional inputs refine how that observation enters the event tree
+().
+
+trigger'],
+ ['—', 'ft'],
+ ['—', '> 0 and at or below the crest'],
+ ['None (required after sand boils or concentrated seepage)', 'No trigger'],
+ ]}
+/>
+
+- **Seepage through confining layer** (Yes or No) — Whether the observed sand boils or concentrated seepage emerged through the confining layer. Yes
+ establishes that an unfiltered exit through the layer already exists, forcing the unfiltered-exit probability to certainty; No records that
+ the observation did not penetrate the layer and has no further effect. The question is asked only after a sand-boil or concentrated-seepage
+ observation, which keeps "no observation" distinct from "observed, but not through the layer."
+- **Trigger elevation** $E_{trigger}$ — Pool elevation at or above which sand boils or concentrated seepage have historically
+ activated (or are expected to activate). At pool levels at or above it, the initiation probability is set to certainty, because initiation has been demonstrated at those
+ loads.
+
+## Embankment Materials
+
+**Embankment materials** (required unless the confining layer presence is Yes) — One or more Unified Soil Classification System (USCS)
+classes describing the materials overlying the developing pipe along the seepage pathway. Each class maps to a probability that it can sustain a
+stable pipe roof, and the minimum across the listed materials governs, because every material along the path must hold a roof for the pipe to
+remain open. The mapping is given in [Event Tree](./06-event-tree.mdx). When the confining layer presence is Yes, the layer itself is credited as
+the roof and the materials are not used.
+
+## Foundation Sand Properties
+
+The foundation sand — the erodible aquifer beneath the embankment — is characterized by its thickness, relative density, gradation, and fines
+content (). The thickness, the relative density category, and the fines content category
+are required; Unknown is a valid answer for the two categories. The gradation
+properties carry screening defaults that the user may override with site-specific distributions.
+
+r', 'Cu', 'D10', '—'],
+ ['ft', '%', '—', 'mm', '—'],
+ ['> 0', '0 to 100', '≥ 1', '> 0', '—'],
+ [
+ 'None (required)',
+ 'None (required)',
+ 'Triangular: 1.1, 2.0, 4.0',
+ 'Normal: mean 0.25, standard deviation 0.085, not less than 0.1',
+ 'None (required)',
+ ],
+ ]}
+/>
+
+The thickness, coefficient of uniformity, and effective grain size are entered as distributions, and the relative density as a category or a
+custom distribution. The valid ranges are the physical ranges of each quantity (the coefficient of uniformity cannot be less than 1 by
+definition). Apart from the relative density, the model does not test sampled values against these ranges, so a distribution that could stray
+outside them should carry lower or upper limits.
+
+- **Foundation sand thickness** $d$ — Thickness of the pervious foundation (aquifer) layer, entered as a distribution. It enters both the
+ blanket-theory analysis (the seepage entrance and gradient computations) and the Schmertmann progression analysis (the depth correction).
+- **Relative density category** $D_r$ — Qualitative relative density of the foundation sand. Denser sands resist progression through the
+ Schmertmann density correction. The choices are:
+ - Very Loose, Loose, Medium Dense, Dense, or Very Dense — each maps to a uniform distribution of relative density
+ ()
+ - Unknown — a broad band spanning loose to medium-dense conditions applies
+ - Custom — the user supplies a site-specific distribution; every value it can produce must lie within the physical range of 0 to 100%, so an
+ unbounded form such as a normal distribution requires explicit lower and upper limits
+- **Coefficient of uniformity** $C_u$ — Coefficient of uniformity of the foundation sand gradation. It sets the base critical gradient in the
+ Schmertmann method; more uniform sands (lower values) are more erodible.
+- **Effective grain size** $D_{10}$ — Grain size at 10% passing for the foundation sand. It sets the Schmertmann grain-size correction.
+- **Fines content category** — Fines content of the foundation sand, which places the sand on one side or the other of the step in the
+ Schmertmann fines-content correction (see [Delegated Methods](./07-delegated-methods.mdx)). The choices are:
+ - Less than 5% — taken as 0% fines; no fines correction applies
+ - 5% or more — taken as 5% fines; the higher fines correction applies
+ - Unknown — taken as 0% fines, so no fines credit is taken
+
+
+
+:::warning[INPUT NEEDED IN-02 — Engineering Basis]
+The default coefficient-of-uniformity distribution (triangular with low 1.1, mode 2.0, high 4.0) requires an engineering basis. Provide a
+literature citation or the engineering-judgment attribution to state here.
+
+Proposed (unconfirmed): representative of the poorly graded, uniform fine to medium sands that are susceptible to backward erosion piping;
+confirm or replace.
+:::
+
+:::warning[INPUT NEEDED IN-03 — Engineering Basis]
+The default effective-grain-size distribution (normal with mean 0.25 mm and standard deviation 0.085 mm, limited below at 0.1 mm) requires an
+engineering basis — both the distribution parameters and the lower limit. Provide a literature citation or the engineering-judgment attribution
+to state here.
+:::
+
+:::warning[INPUT NEEDED IN-04 — Engineering Basis]
+The relative-density uniform ranges require an engineering basis — the category band boundaries and the choice of the 15–65% band for the
+Unknown category. Provide a literature citation or the engineering-judgment attribution to state here.
+
+Proposed (unconfirmed): the category boundaries (15 / 35 / 65 / 85%) follow the standard qualitative relative-density classification for
+granular soils; a uniform distribution over each band takes no position on a most-likely value within the category; and the Unknown
+band spans loose to medium-dense as a conservative screening posture. Confirm or replace, and supply the classification source for the
+bibliography if the proposal stands.
+:::
+
+## Unit Weights
+
+Two saturated unit weights enter the blanket-theory critical-gradient computations
+(). Both carry screening defaults that may be overridden.
+
+sand', 'γbl'],
+ ['pcf', 'pcf'],
+ ['> 62.4', '> 62.4'],
+ ['Normal: mean 122.0, standard deviation 3.0', 'Normal: mean 118.0, standard deviation 3.0'],
+ ]}
+/>
+
+Both unit weights are entered as distributions. A saturated unit weight must exceed the unit weight of water (62.4 pcf) for the critical
+gradient to be positive; the model does not test sampled values against this limit, so a distribution that could fall below it should carry a
+lower limit.
+
+- **Foundation sand saturated unit weight** $\gamma_{sand}$ — Sets the critical vertical gradient for heave of the sand through a defect in
+ the confining layer.
+- **Confining layer saturated unit weight** $\gamma_{bl}$ — Sets the critical vertical gradient for hydraulic blowout (rupture) of the layer.
+
+:::warning[INPUT NEEDED IN-05 — Engineering Basis]
+The default foundation-sand saturated unit weight (normal with mean 122.0 pcf and standard deviation 3.0 pcf) requires an engineering basis.
+Provide a literature citation or the engineering-judgment attribution to state here.
+
+Proposed (unconfirmed): typical of loose to medium-dense saturated alluvial sand; confirm or replace.
+:::
+
+:::warning[INPUT NEEDED IN-06 — Engineering Basis]
+The default confining-layer saturated unit weight (normal with mean 118.0 pcf and standard deviation 3.0 pcf) requires an engineering basis.
+Provide a literature citation or the engineering-judgment attribution to state here.
+:::
+
+## Intervention and Breach Probabilities
+
+The final two event-tree nodes are user-specified probabilities (). Both default to 1.0
+(certain), which is conservative for screening.
+
+int', 'Pbr'],
+ ['0 to 1', '0 to 1'],
+ ['1.0', '1.0'],
+ ]}
+/>
+
+- **Probability of unsuccessful intervention** $P_{int}$ — Probability that detection and emergency intervention fail to stop the piping
+ process before breach. The default assumes no successful intervention; a lower value should be used only when documented monitoring,
+ early-warning, and response capabilities support it.
+- **Probability of breach** $P_{br}$ — Probability that an uncontrolled release of impounded water occurs, given that the pipe has progressed
+ fully and intervention has failed. The default assumes certain breach.
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/04-flaw-assessment.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/04-flaw-assessment.mdx
new file mode 100644
index 000000000..2210b1237
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/04-flaw-assessment.mdx
@@ -0,0 +1,183 @@
+---
+title: Flaw Assessment
+---
+
+import Equation from '@site/src/components/Equation';
+import EquationReference from '@site/src/components/EquationReference';
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Flaw Assessment
+
+The first event-tree node is the probability that a continuous path of fine to medium, uniform sand exists in the foundation — the flaw that
+backward erosion piping requires. The screening model estimates this probability with a Bayesian assessment: a prior probability based on the
+geologic depositional environment is updated by the available site evidence. The assessment is independent of pool level; the resulting
+probability applies across the entire system response curve.
+
+## Bayesian Framework
+
+The assessment combines up to three pieces of information:
+
+1. **Geologic prior** — The depositional environment of the foundation soils sets the prior probability $p_0$ that a laterally continuous,
+ uniform fine sand layer was deposited.
+2. **Subsurface-data evidence** — When borings, soundings, geophysics, or comparable data inform the judgment, the analyst characterizes the
+ strength of that evidence for (or against) a continuous flaw, together with the quality of the data behind the judgment.
+3. **Seepage-observation evidence** — When seepage has been observed downstream during past loading, the character of the observation serves
+ as evidence that a continuous transmissive pathway already exists.
+
+Each evidence source is expressed as a likelihood ratio $LR$ — the ratio of the probability of the observation given that a continuous flaw
+exists to its probability given no flaw. Ratios above one make the flaw more probable; ratios below one make it less probable. The update is
+performed in log-odds form:
+
+
+
+
+
+
+
+where:
+
+> $p_0$ = prior probability of a continuous flaw from the geologic environment
+> $\ell_0$, $\ell$ = prior and posterior log-odds
+> $LR_{sub}$ = likelihood ratio for the subsurface-data evidence
+> $q$ = subsurface data quality factor, which scales the weight given to the subsurface evidence
+> $LR_{seep}$ = likelihood ratio for the seepage observation
+> $P_{flaw}$ = posterior probability of a continuous flaw
+
+When subsurface data is not available, the subsurface term drops out of (equivalently,
+$LR_{sub} = 1$). When no seepage has been observed, the seepage term drops out ($LR_{seep} = 1$). The quality factor $q$ acts as an exponent on
+the subsurface likelihood ratio: high-quality data receives full weight ($q = 1$), while lower-quality data is discounted toward neutral
+($q < 1$).
+
+:::warning[INPUT NEEDED IN-18 — Bibliography]
+The Bayesian formulation of the flaw assessment requires a literature source: expressing each evidence source as a likelihood ratio, updating
+the prior in log-odds form ( to ),
+and weighting the subsurface likelihood ratio by the quality factor $q$ as an exponent. Provide full bibliographic details for the source of
+the formulation (for addition to the bibliography), or the engineering-judgment attribution for the quality-factor weighting if it is specific
+to this model.
+:::
+
+## Uncertainty Quantification
+
+Each categorical selection maps to a *range* of values rather than a single number, reflecting the imprecision of the underlying judgments.
+The model propagates this uncertainty by Monte Carlo simulation: in each realization, the prior probability and each active likelihood ratio
+and quality factor are drawn independently and uniformly from their ranges, and the posterior probability is computed from
+. Across realizations this produces a distribution of the posterior flaw probability.
+
+The **mean posterior probability** populates the event-tree node. The spread of the posterior, from its 5th to its 95th percentile, is reported
+alongside it, so the user can see how sharply the evidence constrains the flaw judgment (see
+[Output and Interpretation](./09-output-and-interpretation.mdx)).
+
+## Geologic Environment Priors
+
+ lists the prior probability range for each depositional environment. Environments that
+deposit laterally continuous, well-sorted fine sands — glacial outwash foremost — carry the highest priors. The Unknown selection carries a
+moderate, deliberately broad prior.
+
+
+
+:::warning[INPUT NEEDED IN-07 — Engineering Basis]
+The prior probability ranges by geologic depositional environment require an engineering basis. Provide a literature citation (to be added to
+the bibliography) or the engineering-judgment attribution to state here — including whether the ranges derive from a published compilation of
+depositional-environment characteristics or from elicited expert judgment.
+:::
+
+## Subsurface-Data Evidence
+
+ lists the likelihood-ratio range for each strength-of-evidence selection, and
+ the quality factor that scales the weight of that evidence. A neutral selection carries a
+likelihood ratio of exactly one (no update in either direction).
+
+
+
+
+
+:::warning[INPUT NEEDED IN-08 — Engineering Basis]
+The strength-of-evidence likelihood-ratio ranges and the data-quality factor ranges require an engineering basis. Provide a literature
+citation or the engineering-judgment attribution to state here — including the reasoning behind the order-of-magnitude bands (0.01–30) and
+the quality discounts (0.50–1.00).
+:::
+
+## Seepage-Observation Evidence
+
+ lists the likelihood-ratio range for each observed seepage signature. Localized,
+sediment-transporting observations are the strongest evidence of a continuous transmissive flaw; diffuse wet areas that do not respond to pool
+level are close to uninformative.
+
+
+
+:::warning[INPUT NEEDED IN-09 — Engineering Basis]
+The seepage-observation likelihood-ratio ranges require an engineering basis. Provide a literature citation or the engineering-judgment
+attribution to state here.
+:::
+
+A sand-boil or concentrated-seepage observation also interacts with the event tree beyond the flaw node: it activates the
+seepage-through-confining-layer question and, through the trigger elevation, can force the initiation node to certainty at high pools
+(see [Input Parameters](./03-input-parameters.mdx) and [Event Tree](./06-event-tree.mdx)).
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/05-hydraulic-loading-and-seepage-paths.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/05-hydraulic-loading-and-seepage-paths.mdx
new file mode 100644
index 000000000..ca6758fa8
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/05-hydraulic-loading-and-seepage-paths.mdx
@@ -0,0 +1,245 @@
+---
+title: Hydraulic Loading and Seepage Paths
+---
+
+import Citation from '@site/src/components/Citation';
+import CitationFootnote from '@site/src/components/CitationFootnote';
+import Equation from '@site/src/components/Equation';
+import EquationReference from '@site/src/components/EquationReference';
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Hydraulic Loading and Seepage Paths
+
+Before the event tree is assembled, the model resolves the hydraulic loading and the seepage-path geometry from the site inputs: the downstream
+reference elevations that control net driving head, the treatment of tailwater, the three seepage path components $L_1$, $L_2$, and $L_3$, the
+selection between the two blanket-theory configurations, the location of the exit evaluation point, and the head that acts across the confining
+layer there. This chapter documents each resolution rule in calculation order.
+
+## Downstream Reference Elevations
+
+Two reference elevations define the downstream boundary of the head computations:
+
+- **Toe reference elevation** $E_{toe,ref}$ — the controlling ground surface at the downstream limit of the embankment section. When a seepage
+ berm is present and its toe ground-surface elevation is specified, the berm toe controls; otherwise the downstream embankment toe controls
+ (the ground beneath a berm is then assumed flat, so the berm toe shares the embankment toe elevation).
+
+- **Daylight reference elevation** $E_{day,ref}$ — the controlling ground surface at the downstream termination of the confining layer, where
+ the foundation sand daylights. When the daylight ground-surface elevation is supplied, it controls; otherwise the daylight exit is assumed to
+ share the toe reference elevation. The daylight ground may sit above or below the embankment toe. One exception applies: when the daylighting
+ exit is the berm toe itself — a berm that reaches or clears a confirmed layer's downstream extent, overlies a confirmed layer of unknown
+ extent, or overlies a layer of unknown presence — the toe reference is the exit's datum, and a separately supplied daylight ground-surface
+ elevation would describe the same location a second time. The supplied value is then not used.
+
+The two elevations play different roles. Seepage beneath the confining layer leaves the foundation sand at the daylighting exit, so the
+daylight reference elevation sets the exit level that controls the driving head for the blowout, heave, and daylight progression analyses.
+The toe reference elevation sets the level of the water standing on the confining layer at the exit evaluation point, against which the
+blowout and heave net head is measured (see [Head Beneath the Confining Layer](#head-beneath-the-confining-layer)), and it controls the toe
+progression pathway. Both elevations therefore enter the blowout and heave analyses whenever they differ.
+
+## Tailwater and Net Driving Head
+
+At each pool level, the downstream control level is the higher of the tailwater and the applicable reference elevation. Where no tailwater
+exists — the tailwater series was omitted, or an individual stage has no tailwater — the control level falls directly to the reference
+elevation. The net driving head is then:
+
+
+
+where:
+
+> $h$ = headwater elevation
+> $t$ = tailwater elevation at that pool level (where one exists)
+> $E_{ref}$ = the applicable reference elevation ($E_{day,ref}$ for the blowout, heave, and daylight-progression analyses; $E_{toe,ref}$ for
+> the toe-progression analysis)
+
+A pool at or below the exit reference elevation produces zero net driving head: no seepage flows out of that exit, so the progression analysis
+along that pathway is not loaded. Zero driving head does not by itself mean zero load on the confining layer. Where the daylight ground sits
+above the toe, a pool between the two elevations fills the foundation sand to pool level and still acts upward on the layer at the toe; the
+blowout and heave analyses account for this static case (see [Head Beneath the Confining Layer](#head-beneath-the-confining-layer)).
+
+The control level is evaluated at each supplied headwater–tailwater pair and varies linearly between successive supplied headwater values.
+Within any interval between successive supplied headwater values where the supplied tailwater crosses the reference elevation, this linear treatment slightly overstates the
+control level (and so slightly understates the net head); the effect is bounded by the change in tailwater across that interval and is noted in
+[Assumptions and Limitations](./08-assumptions-and-limitations.mdx).
+
+## Seepage Path Components
+
+Blanket theory idealizes the seepage path in three segments : the upstream entry length $L_1$ through or
+beneath the upstream top stratum, the path $L_2$ beneath the embankment, and the downstream path $L_3$ from the embankment toe to the seepage
+exit. The screening model resolves each from the site inputs.
+
+### Upstream Path Length L₁
+
+The upstream path length is resolved by precedence:
+
+1. **Engineered upstream blanket present** — $L_1$ equals the supplied blanket length.
+2. **Confining layer confirmed and Very Thin** — $L_1 = 0$. A very thin upstream extension is credited with no head loss.
+3. **Confining layer confirmed, impervious, with a supplied upstream extension** — $L_1$ equals the supplied upstream confining-layer
+ length.
+4. **Otherwise** — $L_1 = 0$. A layer whose upstream extension is No or Unknown, or a layer that is semi-pervious or of unknown permeability,
+ is credited with no upstream head loss.
+
+:::warning[INPUT NEEDED IN-10 — Engineering Basis]
+Two judgments in the upstream-path crediting rules require an engineering basis to state here:
+
+1. A confirmed Very Thin confining layer contributes no upstream path length ($L_1 = 0$), taking precedence over the impervious-extension
+ credit. Proposed (unconfirmed): a layer thinner than about 5 ft cannot be relied on to remain intact and carry head loss over its upstream
+ extent; confirm or replace.
+2. Only a layer characterized as Impervious is credited; Semi-pervious and Unknown permeability contribute nothing.
+
+Provide the citation or engineering-judgment attribution for each.
+:::
+
+### Embankment Path Length L₂
+
+The embankment path length $L_2$ is the embankment base width — the crest width plus the horizontal projections of the
+upstream and downstream faces (see [Input Parameters](./03-input-parameters.mdx)). A downstream seepage berm is not part of $L_2$; its length
+extends the downstream path instead.
+
+### Downstream Path Length L₃
+
+The downstream path length $L_3$ — from the embankment toe to the seepage exit — is resolved from the berm and confining-layer inputs
+(). A supplied downstream extent enters as its single value; the default for no berm with an
+unknown extent or unknown layer presence is the only downstream-path characterization carried as a distribution.
+
+d to 5·Hd), sampled per Monte Carlo realization.',
+ 'The supplied downstream confining-layer length, as a single value.',
+ ],
+ ]}
+/>
+
+:::warning[INPUT NEEDED IN-11 — Engineering Basis]
+The default downstream path length for an unknown confining-layer extent — uniform between 1 and 5 embankment heights — requires an
+engineering basis. Provide a literature citation or the engineering-judgment attribution to state here, including the reasoning for scaling
+the range to embankment height.
+:::
+
+## Blanket-Theory Configuration Selection
+
+The blowout and heave analyses run under one of two blanket-theory configurations, selected from the upstream seepage barrier:
+
+- **Blanket Theory Case 2** — impervious top strata on both the riverside and the landside (see
+ [Blanket Theory Case 2](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-2)
+ in the BEP Initiation manual).
+ Selected whenever the upstream path length is credited ($L_1 > 0$): an engineered upstream blanket is present, or the confining layer is
+ confirmed, impervious, not Very Thin, and has a supplied upstream extension length. The total seepage path is:
+
+
+
+- **Blanket Theory Case 4** — no riverside top stratum, impervious landside top stratum only (see
+ [Blanket Theory Case 4](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-4)
+ in the BEP Initiation manual).
+ Selected otherwise. With an open seepage entrance, the effective entry length is approximated from the foundation thickness:
+
+
+
+where $d$ is the sampled foundation sand thickness. A confirmed Very Thin layer is credited with $L_1 = 0$ per the crediting rules above, so it
+routes to Case 4 and retains the open-entrance length $0.43\,d$; crediting neither an upstream path nor an entrance length would understate the
+head loss upstream of the embankment.
+
+## Exit Evaluation Point
+
+The blowout and heave probabilities are evaluated at an exit point along the downstream blanket. By default the evaluation point is the
+downstream toe (zero offset), where the excess head is highest. One site condition shifts it: when a berm overlies a confirmed confining layer
+whose supplied downstream extent exceeds the berm length — the configuration in which the toe exit remains beneath the layer and the
+through-layer defect and blowout mechanisms are retained (see [Event Tree](./06-event-tree.mdx)) — the evaluation point moves to the berm toe,
+the first exposed ground beyond the berm:
+
+
+
+where:
+
+> $x$ = distance of the exit evaluation point downstream of the embankment toe
+> $L_b$ = berm length
+
+The confining layer then extends $L_3 - x$ beyond the evaluation point, and the excess head available there follows the linear blanket-theory
+head profile, reduced by the factor $(L_3 - x)/L_3$ relative to the toe (see [Head Beneath the Confining Layer](#head-beneath-the-confining-layer)).
+When the berm instead reaches or clears the layer's downstream extent, no offset arises — the exit daylights at the berm toe and the
+confined-exit nodes are set to certainty rather than computed (see [Event Tree](./06-event-tree.mdx)).
+
+## Head Beneath the Confining Layer
+
+Blowout and heave depend on the net head across the confining layer at the exit evaluation point: the head in the foundation sand beneath the
+layer less the head of the water standing on the layer there. The two heads are referenced to different ground surfaces. The seepage beneath
+the layer exits at the daylighting exit, so the exit level is
+
+
+
+where:
+
+> $E$ = exit level, the control level at the daylighting exit
+> $T$ = level of the water standing on the confining layer at the exit evaluation point
+> $E_{check}$ = ground surface at the exit evaluation point: $E_{toe,ref}$ (the berm-toe ground when a berm is present)
+
+The head in the sand beneath the layer at the evaluation point combines the exit level with the share of the driving head that remains after
+the head loss along the path upstream of that point :
+
+
+
+and the net head across the layer is
+
+
+
+where $L_{total}$ is the total seepage path of the selected configuration ( or
+), evaluated per Monte Carlo realization, and $x$ is the evaluation-point distance of
+. A distance $x$ at or beyond $L_3$ leaves no head from flow at the evaluation point.
+
+The first term covers two loading states. When the pool stands above the exit level, seepage flows and $\min(h, E) = E$: the head beneath the
+layer is the exit level plus the remaining share of the driving head. When the pool stands at or below the exit level, no seepage flows, the
+second term vanishes, and the foundation sand fills to pool level, so $h_{under} = h$. A daylight ground above the toe therefore adds the
+difference between the two ground surfaces to the uplift at the toe, and a daylight ground below the toe reduces it. Where the daylight ground
+equals the toe ground, reduces to the excess head of the blanket-theory toe solution.
+
+The blowout analysis compares the upward gradient $h_{net}/z_{bl}$ with the critical gradient of the confining layer, and the heave analysis
+with the critical gradient of the foundation sand (see [Delegated Methods](./07-delegated-methods.mdx)). A realization with no positive net head
+does not fail.
+
+## Progression Path Lengths
+
+The Schmertmann progression analysis uses the full geometric path from the upstream limit of the seepage barrier to the exit under evaluation:
+
+
+
+
+
+where the berm length $L_b$ is included only when a berm is present. $L_3$ in the daylight path is sampled per Monte Carlo realization only
+when no berm is present and the downstream extent or the layer's presence is unknown (the one-to-five-embankment-height default); otherwise it
+enters as a single value. A longer path reduces the average applied gradient. When the presence is Unknown and a berm is present, $L_3 = L_b$,
+so the two progression paths are equal.
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/06-event-tree.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/06-event-tree.mdx
new file mode 100644
index 000000000..1312e329b
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/06-event-tree.mdx
@@ -0,0 +1,298 @@
+---
+title: Event Tree
+---
+
+import Citation from '@site/src/components/Citation';
+import CitationFootnote from '@site/src/components/CitationFootnote';
+import Equation from '@site/src/components/Equation';
+import EquationReference from '@site/src/components/EquationReference';
+import Figure from '@site/src/components/Figure';
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Event Tree
+
+The BEP screening model computes the system response probability at each headwater level by multiplying probabilities from a seven-node event
+tree. The tree follows the structure defined in the
+[Typical Event Tree Database](/docs/toolbox-technical-manuals/risk-calculations-suite/typical-event-tree-database/v1.5/Backward-Erosion-Piping)
+for the backward erosion piping failure mode; every database node maps one-to-one onto a screening-model node.
+
+
+
+## Node Summary
+
+ summarizes the seven nodes and how the screening model populates each probability on each
+exit pathway. The sections that follow state the engineering question each node answers and give each node in full. Nodes 2, 3, and 5 vary with pool level and differ between the toe and daylight pathways; the remaining nodes
+are pool-independent and shared by both pathways.
+
+
+
+## Node 1: Flaw — Continuous Path
+
+*Question:* Does a continuous path of fine to medium, uniform sand exist in the foundation?
+
+The probability $P_{flaw}$ that a continuous path of erodible foundation sand exists is the mean posterior probability from the Bayesian flaw
+assessment documented in [Flaw Assessment](./04-flaw-assessment.mdx). The flaw is a geologic condition, so this probability is constant across
+all pool levels and is shared by both exit pathways.
+
+## Node 2: Flaw — Unfiltered Exit
+
+*Question:* Does seepage exit unfiltered at the ground surface?
+
+### Toe pathway
+
+When a confining layer may be present and the toe exit remains beneath it — no berm, or a berm ending within the layer's known downstream
+extent — seepage can reach the surface unfiltered at the toe through either of two mechanisms:
+
+- **Pre-existing defect** — a discontinuity that already penetrates the layer (desiccation crack, root channel, animal burrow, or similar).
+ The probability that a defect passes completely through the layer is evaluated as a survival function on the layer thickness:
+
+
+
+ where $z_{bl}$ is the confining-layer thickness, $t_c = 3.5$ ft is the characteristic defect penetration depth, and $k = 1.25$ is the shape
+ parameter. The expression is the probability that a defect's penetration depth equals or exceeds the layer thickness under a Weibull
+ distribution of defect depths — thinner layers are more likely to be fully penetrated. The probability is evaluated for each sampled layer
+ thickness and averaged across the Monte Carlo realizations; it does not depend on pool level.
+
+- **Hydraulic blowout** — rupture of the layer when uplift at its base exceeds its buoyant weight. The blowout probability $P_{blowout}(h)$ at
+ each pool level is computed by the blanket-theory analysis using the confining layer's saturated unit weight
+ (see [Delegated Methods](./07-delegated-methods.mdx)); it increases with the net head across the layer. The probability is evaluated at the
+ exit evaluation point — the toe by default, or the berm toe when a berm ends within the layer's known extent — with the net head measured
+ against the water standing on the layer there
+ (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx#head-beneath-the-confining-layer)).
+
+The two mechanisms are combined as the union of independent pathways:
+
+
+
+Three site conditions override the composition and force $P_{ue} = 1.0$ at every pool level:
+
+1. **No confining layer** — with the layer's presence answered No, nothing filters the exit.
+2. **The exit daylights at the berm toe** — a berm that reaches or clears a confirmed layer's supplied downstream extent, or overlies a
+ confirmed layer of unknown extent: the berm toe then sits at or beyond the layer's termination, so nothing filters the exit there. For a
+ layer of unknown presence, any berm forces this override — a daylighting exit at the berm toe is assumed rather than established. In all
+ these cases the berm toe is itself the daylighting exit and no separate daylight pathway is evaluated (see Governing SRP below).
+3. **Observed seepage through the layer** — sand boils or concentrated seepage have been observed emerging through the confining layer,
+ demonstrating that an unfiltered exit already exists. The override applies to any toe exit that remains beneath the layer, with or
+ without a berm.
+
+A berm ending within a confirmed layer's known extent triggers none of these overrides: the through-layer composition above is retained, with
+the blowout probability evaluated at the berm toe.
+
+:::warning[INPUT NEEDED IN-13 — Engineering Basis]
+The Weibull defect-survival parameters — characteristic penetration depth $t_c = 3.5$ ft and shape parameter $k = 1.25$ — require an
+engineering basis. These are empirical values with no published-literature provenance recorded. Provide the data source, calibration
+rationale, or engineering-judgment attribution to state here.
+:::
+
+:::warning[INPUT NEEDED IN-14 — Engineering Basis]
+Two judgments in the berm treatment require an engineering basis to state here:
+
+1. No berm is ever credited with filtering the exit: where the berm end remains beneath the layer, the exit resistance is carried entirely
+ by the layer's defect and blowout composition (evaluated at the berm toe), and where the berm daylights the exit, the unfiltered
+ exit is certain.
+2. When the layer's presence is unknown and a berm is present, a daylighting exit at the berm toe is assumed (forcing the unfiltered exit to
+ certainty) rather than evaluated.
+
+Proposed (unconfirmed): for (1), seepage and stability berms are not engineered filters, so no filtering credit is taken for any berm; for
+(2), with the layer itself unverified, its lateral extent beneath the berm cannot be relied upon, and assuming a daylighting exit at the berm
+toe is the conservative screening posture. Confirm or replace.
+:::
+
+:::warning[INPUT NEEDED IN-15 — Engineering Basis]
+The union formula treats the defect and blowout mechanisms as statistically independent pathways. Provide the engineering basis or judgment
+attribution for the independence treatment to state here.
+:::
+
+### Daylight pathway
+
+At the daylight exit the confining layer has terminated; there is nothing to filter the seepage. The unfiltered-exit probability on the
+daylight pathway is 1.0 at every pool level. The pathway itself is evaluated only when the daylighting exit is distinct from the toe exit
+(see Governing SRP below).
+
+## Node 3: Initiation
+
+*Question:* Is the exit gradient sufficient to initiate backward erosion at the unfiltered exit?
+
+### Toe pathway
+
+Initiation at a confined exit requires the vertical gradient through the layer (or through a defect in it) to fluidize the underlying sand.
+The initiation probability $P_{init}(h)$ at each pool level is the blanket-theory heave probability, computed with the foundation sand's
+saturated unit weight and the same net head across the layer as the blowout analysis (see [Delegated Methods](./07-delegated-methods.mdx)).
+Four site conditions override the computed value and force $P_{init} = 1.0$:
+
+1. **No confining layer** — with no overburden to resist heave, initiation accompanies the unfiltered exit.
+2. **A berm overlies a layer of unknown presence, or a confirmed layer of unknown downstream extent** — a daylighting exit is assumed at the
+ berm toe, beyond the characterized layer.
+3. **The berm reaches or clears a supplied downstream extent** — the berm is at least as long as the layer's extent, so the exit sits at or
+ beyond the layer's termination.
+4. **The pool reaches the trigger elevation** — sand boils or concentrated seepage have historically activated at or above this pool, demonstrating initiation:
+
+
+
+where $E_{trigger}$ is the trigger elevation and $P_{heave}(h)$ the blanket-theory heave probability.
+
+The second and third conditions are the berm-toe daylighting cases: they force both this node and the unfiltered-exit node to certainty, and
+the separate daylight pathway is not evaluated (see Governing SRP below).
+
+### Daylight pathway
+
+At the daylight exit the sand is exposed at the surface with no confining layer to resist heave, so initiation is certain once seepage
+leaves the sand there. Seepage leaves the sand only while the pool stands above the exit level; a pool at or below it fills the sand without
+flowing out. The initiation probability on the daylight pathway is therefore
+
+
+
+where $t$ is the tailwater elevation at that pool level, where one exists.
+
+## Node 4: Progression — Mechanical Condition
+
+*Question:* Can the material over the developing pipe sustain a stable roof?
+
+A pipe can only progress if the material above it sustains a stable roof. When the confining layer's presence is confirmed (answered Yes), the
+layer itself provides the roof and the probability is 1.0. Otherwise, the probability is evaluated from the embankment materials: each USCS
+class maps to a roof-support probability per , following Fell et
+al. (2024) , and the minimum across the listed materials governs — every material along the pipe path must
+hold a roof, so the least capable material controls. The probability is constant across pool levels.
+
+
+
+## Node 5: Progression — Hydraulic Condition
+
+*Question:* Is the applied gradient sufficient to advance the pipe toward the impounded water?
+
+The probability that the applied gradient is sufficient to advance the pipe from the exit toward the reservoir is the mean probability of
+advancement from the Schmertmann analysis, evaluated at each pool level for the pathway's seepage path length
+(see [Delegated Methods](./07-delegated-methods.mdx)). The toe pathway uses the path to the embankment or berm toe; the daylight pathway uses
+the longer path to the daylight exit. The resulting probability is constrained to be non-decreasing with pool level, reflecting that, for a net
+head that rises with pool level, a higher pool cannot make progression less likely (see assumption 15 in
+[Assumptions and Limitations](./08-assumptions-and-limitations.mdx)).
+
+## Nodes 6 and 7: Unsuccessful Intervention and Breach
+
+*Questions:* Do detection and intervention fail (Node 6)? Does an uncontrolled release of impounded water occur (Node 7)?
+
+The final two nodes are the user-specified probabilities documented in [Input Parameters](./03-input-parameters.mdx). Both default to
+1.0 — no successful intervention and certain breach — a conservative screening posture.
+
+## SRP Computation
+
+The system response probability for each pathway at each pool level is the product of its seven node probabilities:
+
+
+
+where:
+
+> $P_{flaw}$ = probability of a continuous flaw (Node 1)
+> $P_{ue}(h)$ = probability of an unfiltered exit (Node 2)
+> $P_{init}(h)$ = probability of initiation (Node 3)
+> $P_{roof}$ = probability of roof support (Node 4)
+> $P_{prog}(h)$ = probability of hydraulic progression (Node 5)
+> $P_{int}$ = probability of unsuccessful intervention (Node 6)
+> $P_{br}$ = probability of breach (Node 7)
+
+On the daylight pathway, $P_{ue}$ is 1.0, $P_{init}$ follows , and $P_{prog}$
+reflects the daylight path.
+
+## Governing SRP
+
+A daylight pathway is evaluated only where the daylighting exit is distinct from the toe exit. When a berm reaches or clears a confirmed
+layer's downstream extent, overlies a confirmed layer of unknown extent, or overlies a layer of unknown presence, the berm toe is itself the
+daylighting exit: the toe pathway then carries a certain unfiltered exit and certain initiation over the berm-extended path, which are exactly
+the daylighting-exit conditions, so a separate daylight pathway would repeat the same exit node for node and is not evaluated. A separately
+supplied daylight ground-surface elevation is not used in these cases.
+
+When both pathways are evaluated, the governing SRP at each pool level is the larger of the two pathway values:
+
+
+
+When only the toe pathway exists — no confining layer, or a berm-toe daylighting exit — it governs directly.
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/07-delegated-methods.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/07-delegated-methods.mdx
new file mode 100644
index 000000000..b95df3079
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/07-delegated-methods.mdx
@@ -0,0 +1,252 @@
+---
+title: Delegated Methods
+---
+
+import Citation from '@site/src/components/Citation';
+import CitationFootnote from '@site/src/components/CitationFootnote';
+import Equation from '@site/src/components/Equation';
+import EquationReference from '@site/src/components/EquationReference';
+import NavContainer from '@site/src/components/NavContainer';
+import TableReference from '@site/src/components/TableReference';
+import TableVertical from '@site/src/components/TableVertical';
+
+
+
+# Delegated Methods
+
+The screening model hands two of its event-tree calculations to established analysis methods, each documented in a dedicated technical manual:
+
+- **Blanket theory** evaluates the blowout and heave probabilities behind Node 2 (Flaw: Unfiltered Exit) and Node 3 (Initiation) on the toe
+ pathway.
+- **The Schmertmann critical-gradient method** evaluates the probability of pipe advancement behind Node 5 (Progression: Hydraulic Condition) on
+ both pathways.
+
+The theory of each method lives in its manual. Each section below states the node the method serves and the question it answers there, links
+the chapter of the manual that covers it, and then documents only what the screening model supplies, what it uses from the result, and every
+screening-level adjustment relative to the manual. The flaw assessment (Node 1) and the defect-survival relationship (part of Node 2) are the
+screening model's own calculations, documented in [Flaw Assessment](./04-flaw-assessment.mdx) and [Event Tree](./06-event-tree.mdx).
+
+## Blanket Theory — Blowout and Heave
+
+**Nodes served:** Node 2 (Flaw: Unfiltered Exit) and Node 3 (Initiation), on the toe pathway, wherever a confining layer may be present and the
+toe exit remains beneath it.
+
+**Questions answered:** At Node 2, is the uplift pressure at the base of the confining layer large enough to rupture the layer (blowout), opening
+an unfiltered exit? At Node 3, is the vertical gradient through a defect in the layer large enough to fluidize the underlying sand (heave),
+starting erosion at the exit? Both questions compare the vertical exit gradient through the layer with a critical gradient set by a saturated
+unit weight, which is what blanket theory computes .
+
+### Blanket-theory configuration
+
+The model evaluates one of two blanket-theory configurations, selected from the upstream seepage barrier by the rule documented in
+[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx#blanket-theory-configuration-selection):
+
+- **Case 2** — impervious top strata on both the riverside and the landside, used when an upstream seepage barrier is credited with an
+ upstream path length. The theory,
+ including the exit head at the landside toe and at a given distance beyond it, is in
+ [Blanket Theory Case 2](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-2)
+ of the BEP Initiation manual.
+- **Case 4** — no riverside top stratum and an impervious landside top stratum, used otherwise. The theory, including the effective entrance
+ length of $0.43\,d$ for an open riverside entrance, is in
+ [Blanket Theory Case 4](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-4)
+ of the BEP Initiation manual.
+
+### Blowout and heave evaluations
+
+The model evaluates the selected configuration **twice with identical sampled realizations** of the foundation thickness, confining-layer
+thickness, and downstream path length:
+
+- **Blowout** — the critical gradient is computed from the *confining layer's* saturated unit weight $\gamma_{bl}$, representing rupture
+ of the layer against its buoyant weight. The result feeds Node 2.
+- **Heave** — the critical gradient is computed from the *foundation sand's* saturated unit weight $\gamma_{sand}$, representing
+ fluidization of the sand column at a defect through the layer. The result feeds Node 3.
+
+Because the two evaluations share their sampled realizations, the blowout and heave probabilities differ only through the unit weight entering
+the critical gradient.
+
+### Governing relationships
+
+Within each Monte Carlo realization, and at each pool level with net driving head $H$ above the exit level $E$ (both defined in
+[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)):
+
+
+
+
+
+The head in the sand beneath the layer at the evaluation point is $\min(h, E) + h_x$, and the net head across the layer, $h_{net}$, is that head
+less the water standing on the layer there (). The gradient and factor of safety follow:
+
+
+
+
+
+where:
+
+> $h_o$ = excess head above the exit level at the embankment toe, from flow beneath the layer
+> $h_x$ = excess head above the exit level at the exit evaluation point, a distance $x$ downstream of the toe
+> $h_{net}$ = net head across the confining layer at the exit evaluation point
+> $L_3$, $L_{total}$ = downstream and total seepage path lengths ($L_3$ sampled per realization when no berm is present and the extent or the layer's presence is unknown)
+> $i_{cv}$ = critical vertical gradient
+> $\gamma_{sat}$ = saturated unit weight ($\gamma_{bl}$ for blowout, $\gamma_{sand}$ for heave)
+> $\gamma_w$ = unit weight of water (62.4 pcf)
+> $i_v$ = vertical exit gradient through the confining layer
+> $z_{bl}$ = sampled confining-layer thickness
+> $FS$ = factor of safety against the vertical gradient
+
+The blowout or heave probability at each pool level is the fraction of Monte Carlo realizations in which $FS < 1$. Realizations with no
+upward gradient (no positive net head across the layer) contribute no failure.
+
+### Screening-level adjustments
+
+Relative to the blanket-theory chapters of the BEP Initiation manual, the screening model fixes the following:
+
+- **Finite-blanket head loss always applies** — the excess head at the toe is always reduced by the path-length ratio
+ (). The idealization of an infinite downstream blanket carrying the full net head at
+ the toe is not used.
+- **The exit and the evaluation point may sit at different ground elevations** — the blanket-theory chapters measure the exit head against a
+ single landside ground surface. The screening model measures the driving head to the exit level at the daylighting exit and the net head
+ against the water standing on the layer at the evaluation point, so a daylighting exit above the toe adds the difference to the uplift and
+ one below the toe reduces it. With a pool below the exit level, no seepage flows and the foundation sand stands at pool level beneath the
+ layer. Where the two ground surfaces coincide, the net head equals the blanket-theory excess head $h_x$.
+- **Downstream blanket length follows the resolved downstream path** — $L_3$ enters as the supplied downstream extent, or is drawn per
+ realization from the wide default range when no berm is present and the extent or the layer's presence is unknown
+ (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+- **Confining-layer thickness comes from the category band** — the sampled $z_{bl}$ follows the qualitative thickness category (or the custom
+ distribution) documented in [Input Parameters](./03-input-parameters.mdx).
+- **The unit weight is mechanism-specific** — $\gamma_{bl}$ for blowout and $\gamma_{sand}$ for heave, each defaulting per
+ [Input Parameters](./03-input-parameters.mdx).
+- **Foundation permeability does not influence the screening result** — hydraulic conductivity affects only the seepage-quantity results of
+ blanket theory, which the screening model does not use; the exit-gradient computations are independent of it.
+
+## Schmertmann Method — Progression
+
+**Node served:** Node 5 (Progression: Hydraulic Condition), on the toe pathway and, when it is evaluated, the daylight pathway.
+
+**Question answered:** Once erosion has initiated at the exit and a roof is available, is the average hydraulic gradient along the seepage path
+large enough to keep advancing the pipe upstream through the foundation sand until it reaches the reservoir? The Schmertmann
+method answers it by comparing the average applied gradient with a field critical gradient derived from
+laboratory piping tests and corrected for site conditions. The complete method is documented in the
+[Schmertmann](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann) chapter of the BEP
+Progression manual; the subsections below link the part of that chapter each step follows.
+
+### Base critical gradient
+
+The base critical gradient derives from laboratory piping-model tests, represented as a family of quantile curves linear in the coefficient of
+uniformity (see
+[Laboratory Horizontal Critical Gradient](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#laboratory-horizontal-critical-gradient)):
+
+
+
+where $i_{pmt}(\xi)$ is the laboratory critical gradient at cumulative probability $\xi$, and $m(\xi)$ and $b(\xi)$ are the quantile regression
+coefficients from the BEP Progression manual. The screening model uses these laboratory relationships without modification.
+
+### Field critical gradient and correction factors
+
+The field critical gradient scales the laboratory gradient by the correction factors (see
+[Field Horizontal Critical Gradient](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#field-horizontal-critical-gradient)):
+
+
+
+In the screening configuration, five factors remain active and four are fixed at unity
+().
+
+D', 'CL', 'CS', 'Cγ', 'COF', 'CK', 'CZ', 'Cα', 'CR'],
+ [
+ 'Depth',
+ 'Seepage path length',
+ 'Grain size',
+ 'Density',
+ 'Overall field correction',
+ 'Anisotropy',
+ 'Underlayer',
+ 'Pipe-path inclination',
+ 'Axis curvature',
+ ],
+ ['Active', 'Active', 'Active', 'Active', 'Active', 'Fixed at 1.0', 'Fixed at 1.0', 'Fixed at 1.0', 'Fixed at 1.0'],
+ ]}
+/>
+
+The active factors take their values from the screening inputs:
+
+- $C_D$ — from the sampled foundation thickness $d$ and the pathway's seepage path length
+- $C_L$ — from the pathway's seepage path length
+- $C_S$ — from the sampled effective grain size $D_{10}$
+- $C_\gamma$ — from the sampled relative density $D_r$ (per the category mapping or custom distribution in
+ [Input Parameters](./03-input-parameters.mdx))
+- $C_{OF}$ — the product of the fines-content correction and the exit-geometry factor, given below
+
+The fixed factors reflect information that is rarely available at the screening stage:
+
+- $C_K$ — taken as 1.0, which the BEP Progression manual's anisotropy relationship, $C_K = (1.5/R_{kf})^{0.5}$, gives for a reference
+ conductivity ratio $R_{kf} = k_h/k_v$ of 1.5; the seepage path length is not transformed for anisotropy (assumption 12 in
+ [Assumptions and Limitations](./08-assumptions-and-limitations.mdx))
+- $C_Z$ — taken as 1.0, the value for no higher-permeability underlayer; no stratum beneath the aquifer is characterized (assumption 13)
+- $C_\alpha$ — the pipe path is fixed horizontal (inclination 0°), so no inclination correction applies (see
+ [Pipe Path Inclination](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#pipe-path-inclination))
+- $C_R$ — the axis is treated as straight, as in the BEP Progression manual
+
+### Exit geometry and fines corrections
+
+The overall field correction is:
+
+
+
+The exit-geometry factor $C_{3d}$ distinguishes concentrated (hole-type) exits from distributed (plane-type) exits. Van Beek et
+al. (2015) found that three-dimensional flow converging toward a single exit point produces critical
+gradients roughly half those predicted for the two-dimensional configuration. Their comparison was made against the Dutch (Sellmeijer) piping
+model, and the BEP Progression manual notes that the reduction was not developed and calibrated for the Schmertmann method; the screening model
+applies it to the Schmertmann critical gradient by engineering judgment, as the manual does, so a hole-type exit takes $C_{3d} = 0.5$ and a
+plane-type exit $C_{3d} = 1.0$. The screening model assigns the exit type as follows:
+
+- **Toe pathway** — hole-type ($C_{3d} = 0.5$) when the confining layer is confirmed, *unless* a berm is present and either the layer's
+ downstream extent is unknown or the berm reaches or clears that extent (the exit then daylights beyond the layer and is plane-type). When
+ the layer's presence is No or Unknown, the toe exit is plane-type (assumption 18 in
+ [Assumptions and Limitations](./08-assumptions-and-limitations.mdx)).
+- **Daylight pathway** — always plane-type ($C_{3d} = 1.0$); the exit is an exposed sand surface.
+
+The fines-content correction is a step function of the foundation sand's fines content:
+
+
+
+The higher factor applies at exactly 5% fines and above; a fines content below 5% takes no correction.
+
+:::warning[INPUT NEEDED IN-16 — Engineering Basis]
+The fines-content correction applied in the Schmertmann analysis — a step from 1.0 to 1.4, with the higher factor applying at exactly 5% fines
+and above — requires an engineering basis. Provide the source or engineering-judgment attribution for the step form, the 5% threshold, and the
+1.4 value, and add the term to the Schmertmann chapter of the BEP Progression manual, which currently omits it.
+:::
+
+### Probability of advancement
+
+At each pool level, the applied gradient is the net head over the pathway's seepage path length (see
+[Likelihood of Backward Erosion Piping Progression](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#likelihood-of-backward-erosion-piping-progression)):
+
+
+
+where $L_{prog}$ is the toe or daylight progression path length from
+[Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx) (sampled per realization on the daylight pathway when no berm is
+present and the downstream extent or the layer's presence is unknown). Within each realization, the correction factors scale the entire family of laboratory quantile curves
+(), and the probability of advancement is the cumulative probability that the corrected
+critical gradient is at or below the applied gradient — interpolated from the scaled quantile family, and limited to 0 and 1 beyond its ends.
+A pool producing no positive net head yields no probability of advancement.
+
+The Node 5 probability at each pool level is the mean probability of advancement across the Monte Carlo realizations, then constrained to be
+non-decreasing with pool level as described in [Event Tree](./06-event-tree.mdx).
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/08-assumptions-and-limitations.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/08-assumptions-and-limitations.mdx
new file mode 100644
index 000000000..dc2943711
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/08-assumptions-and-limitations.mdx
@@ -0,0 +1,204 @@
+---
+title: Assumptions and Limitations
+---
+
+import Citation from '@site/src/components/Citation';
+import CitationFootnote from '@site/src/components/CitationFootnote';
+import NavContainer from '@site/src/components/NavContainer';
+
+
+
+# Assumptions and Limitations
+
+The BEP screening model applies deliberate simplifications relative to the full toolbox models. They reduce input requirements and are designed
+to avoid false negatives at the screening level. Each assumption below states its engineering basis, its effect on results, and the conditions
+under which it may not hold. Where an engineering basis is still awaiting confirmation, the assumption cross-references the input marker at its
+primary location in this document.
+
+## Seepage Geometry and Hydraulics
+
+1. **The site is idealized as one of two blanket-theory configurations, Case 2 or Case 4.** The configuration is selected from the upstream
+ seepage barrier (see [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+ - *Engineering basis:* Screening design decision (engineering judgment): the two cases bracket the screening-relevant configurations — an
+ upstream barrier either exists or does not — and automatic selection removes a choice from the user.
+ - *Effect on results:* Sites whose stratigraphy matches other blanket-theory cases (semi-pervious strata, more complex layering) are
+ approximated by the nearer of the two configurations.
+ - *When it may not hold:* Sites with well-characterized semi-pervious strata or geometries that need Cases 1, 3, or 5 through 8; the
+ toolbox models apply directly to such sites.
+2. **The downstream confining layer carries a linear head profile.** The excess head above the exit level decays from its value at the toe
+ to zero at the layer's downstream termination.
+ - *Engineering basis:* Blanket theory . The landside layer is analyzed as an impervious top stratum
+ whatever permeability is selected; the permeability selection affects only the upstream credit.
+ - *Effect on results:* Exit heads are reduced by the path-length ratio, which is less conservative than an infinite-blanket idealization.
+ - *When it may not hold:* Blankets with strong lateral heterogeneity, or relief wells and toe drains that alter the head profile. A
+ semi-pervious landside layer also departs from it: blanket theory replaces a semi-pervious landside stratum with an equivalent impervious
+ length that can be shorter or longer than the physical length, depending on the landside boundary condition (see
+ [Blanket Theory Case 6](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/blanket-theory-case-6)),
+ so the impervious treatment can overstate or understate the exit head.
+3. **When the confining-layer extent or presence is unknown and no berm is present, the downstream seepage path spans 1 to 5 embankment heights.**
+ - *Engineering basis:* Basis requested — see marker IN-11 in [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx).
+ - *Effect on results:* The wide range spreads the sampled exit heads, gradients, and daylight path lengths, widening the uncertainty carried
+ into the blowout, heave, and daylight-progression results.
+ - *When it may not hold:* Sites where mapping or borings bound the layer extent outside 1 to 5 embankment heights, where the analyst supplies the extent instead.
+4. **Supplied seepage-path lengths are single values.** The upstream blanket length and the upstream and downstream confining-layer extents
+ carry no uncertainty; the default range for an unknown downstream extent is the only seepage-path length treated as a distribution.
+ - *Engineering basis:* Screening design decision (engineering judgment): a known length is a geometric site measurement entered as one
+ value, and uncertainty about an unknown downstream extent is represented by the wide default range instead.
+ - *Effect on results:* The SRP reflects the entered path lengths exactly; uncertainty in a measured length does not spread the result.
+ - *When it may not hold:* Sites where a supplied seepage-path length is both highly uncertain and influential; the analyst then brackets
+ that uncertainty by running the analysis at candidate lengths.
+5. **The downstream control level is interpolated linearly between successive supplied headwater values.** The control level is the higher of the tailwater
+ and the exit reference elevation, evaluated at each supplied headwater–tailwater pair.
+ - *Engineering basis:* Screening simplification (engineering judgment) with a bounded, documented effect (see
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx)).
+ - *Effect on results:* Within any interval between successive supplied headwater values where the tailwater crosses the reference elevation, the
+ interpolated control level slightly overstates the true value, understating the net head there by no more than the change in tailwater
+ across that interval (slightly non-conservative).
+ - *When it may not hold:* Tailwater that crosses the exit reference within a wide interval between successive supplied headwater values;
+ additional headwater–tailwater pairs near the crossing reduce the effect.
+
+## Unfiltered Exit and Initiation
+
+6. **A pre-existing defect fully penetrates the confining layer with a probability given by a Weibull survival function of thickness.** The
+ characteristic depth is 3.5 ft and the shape parameter is 1.25 (see [Event Tree](./06-event-tree.mdx)).
+ - *Engineering basis:* Basis requested — see marker IN-13 in [Event Tree](./06-event-tree.mdx).
+ - *Effect on results:* The defect probability sets a pool-independent lower bound on the toe unfiltered-exit probability, because the
+ unfiltered-exit probability can never be less than the defect probability. Averaged over the thickness bands, the defect probability is
+ about 0.55 for Very Thin, 0.32 for Unknown, 0.09 for Thin, and below 0.01 for Moderate and Thick, so it controls Node 2 whenever the band
+ includes thin layers and the blowout probability is lower.
+ - *When it may not hold:* Sites with a defect survey or verified intact layers (inspection, construction records) that contradict the
+ generic defect population.
+7. **The defect and blowout pathways to an unfiltered exit are statistically independent.**
+ - *Engineering basis:* Basis requested — see marker IN-15 in [Event Tree](./06-event-tree.mdx).
+ - *Effect on results:* The combined unfiltered-exit probability is at least as large as either mechanism alone.
+ - *When it may not hold:* Where the two mechanisms share a common cause (both concentrated at thin spots in the layer), the union may misstate
+ the combined probability.
+8. **A downstream seepage berm is classified by where it ends relative to the confining layer.** A berm within a confirmed layer of known
+ greater extent retains the through-layer exit mechanisms, evaluated at the berm toe. A berm that reaches or clears the extent, or overlies a
+ layer of unknown extent or unknown presence, produces a daylighting exit at the berm toe with a certain unfiltered exit and certain
+ initiation. No berm is credited with filtering, and every berm lengthens the toe progression path.
+ - *Engineering basis:* Basis requested — see marker IN-14 in [Event Tree](./06-event-tree.mdx).
+ - *Effect on results:* A berm within a known layer extent keeps the defect and blowout composition, with the head at the berm toe reduced
+ by the share of the layer the berm covers. A berm that daylights the exit makes the unfiltered-exit and initiation nodes certain, and the
+ toe pathway then carries the governing curve (see [Event Tree](./06-event-tree.mdx)).
+ - *When it may not hold:* Engineered filter berms designed to filter the exit; sites where the berm length relative to the layer extent is
+ itself uncertain, since that comparison switches the exit treatment.
+9. **A confining layer of unknown presence is evaluated as possibly present.** The defect and blowout analyses run with the Unknown thickness
+ band, roof support comes from the embankment materials, and both exit pathways are evaluated unless a berm makes the berm toe the single
+ exit.
+ - *Engineering basis:* Screening design objective (engineering judgment): an unverified layer is neither ignored nor fully credited, avoiding false negatives from
+ either extreme.
+ - *Effect on results:* Results for unknown-presence sites reflect deliberately wide parameter bands rather than either the confirmed-present
+ or the confirmed-absent treatment.
+ - *When it may not hold:* Once field verification confirms the layer present or absent, the analysis is re-run with the confirmed answer.
+
+## Progression
+
+10. **A confirmed confining layer provides a certain pipe roof; otherwise the least capable embankment material governs roof support.**
+ - *Engineering basis:* Roof-support values follow Fell et al. (2024) . Layer-as-roof: engineering
+ judgment adopted in the model design — a fine-grained layer able to confine the foundation also sustains the pipe roof.
+ - *Effect on results:* With a confirmed layer, no roof-support reduction applies. Otherwise the governing roof-support probability multiplies
+ the SRP at every pool level, so a single listed clean sand or gravel (roof-support probability 0.01) lowers the whole curve by two orders
+ of magnitude.
+ - *When it may not hold:* Layers too thin or brittle to sustain a roof over a growing pipe; heavily fractured or desiccated layers.
+11. **The pipe path is horizontal.** No inclination correction is applied.
+ - *Engineering basis:* Screening design decision (engineering judgment): pipe inclination is rarely known at the screening stage.
+ - *Effect on results:* Neutral for horizontal paths; conservative for downward-inclined paths and non-conservative for upward-inclined
+ paths. The size of the effect at shallow angles awaits a basis (marker IN-19 below).
+ - *When it may not hold:* Steeply inclined pipe paths (the angle beyond which the effect matters awaits a basis; marker IN-19 below).
+12. **The anisotropy correction is set to its reference value.** The correction factor $C_K$ is taken as 1.0, the value the Schmertmann
+ relationship $C_K = (1.5/R_{kf})^{0.5}$ gives for a conductivity ratio $R_{kf} = k_h/k_v$ of 1.5, and the seepage path length is not
+ transformed for anisotropy (see
+ [Field Horizontal Critical Gradient](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#field-horizontal-critical-gradient)).
+ - *Engineering basis:* Screening design decision (engineering judgment): the conductivity ratio is rarely characterized at the screening stage.
+ - *Effect on results:* Relative to applying the full method with the site ratio, the result is conservative for ratios below 1.5 (at equal
+ conductivity the full method gives $C_K \approx 1.22$, a higher critical gradient). For ratios above 1.5 it can be substantially
+ non-conservative: at a ratio of 4 the full method gives $C_K \approx 0.61$, partly offset because the full method also shortens the
+ transformed path length, which raises the path-length and depth corrections.
+ - *When it may not hold:* Strongly layered or stratified foundations, where horizontal conductivity is well above vertical.
+13. **No underlayer correction is applied beneath the aquifer.** The correction factor $C_Z$ is taken as 1.0, the Schmertmann method's value
+ when no higher-permeability underlayer exists.
+ - *Engineering basis:* Screening design decision (engineering judgment): underlayer properties are rarely available at the screening stage.
+ - *Effect on results:* A higher-permeability layer beneath the piping sand increases the flow toward the pipe and lowers the critical
+ gradient ($C_Z < 1$), so neglecting it is non-conservative where one exists; where none exists, the treatment matches the full method. The
+ BEP Progression manual notes that $C_Z$ is approximately 1 when the ratio of piping-layer depth to pipe radius exceeds about 80 (see
+ [Field Horizontal Critical Gradient](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#field-horizontal-critical-gradient)).
+ - *When it may not hold:* A higher-permeability stratum (for example, coarse sand or gravel) beneath a thin piping sand.
+14. **An Unknown fines content is taken as 0%, and the fines correction is a step at 5% fines.** The correction factor is 1.0 below 5% fines and
+ 1.4 at or above 5%.
+ - *Engineering basis:* Taking an Unknown fines content as 0% is a conservative screening posture (engineering judgment): it forgoes the higher fines correction, which would raise the resistance to progression. Step form: basis
+ requested — see marker IN-16 in [Delegated Methods](./07-delegated-methods.mdx).
+ - *Effect on results:* Sands with real fines content receive less progression resistance than the method would assign unless the 5% or
+ more category is selected.
+ - *When it may not hold:* Sands with significant fines where gradation data is available, where the analyst selects the matching fines
+ category.
+15. **The progression probability is non-decreasing with pool level.**
+ - *Engineering basis:* Physical reasoning: for a fixed seepage geometry and a net head that rises with pool level, a higher pool cannot make progression less likely.
+ - *Effect on results:* Sampling noise cannot produce a locally decreasing progression node.
+ - *When it may not hold:* Configurations where the net head genuinely falls as the pool rises (tailwater rising faster than headwater); the
+ constraint then overrides a real decrease.
+
+:::warning[INPUT NEEDED IN-19 — Engineering Basis]
+Assumption 11 (horizontal pipe path) needs a basis for two statements about the size of the neglected inclination effect: that it is small at
+shallow angles, and that it becomes significant for paths inclined more than about 10° from horizontal. Provide the literature source (for
+example, the pipe-path inclination relationship of the Schmertmann method) with full bibliographic details, or the engineering-judgment
+attribution, and confirm or replace the 10° threshold.
+:::
+
+## Exit Datum and Exit Type
+
+17. **The blowout and heave net head combines the daylight exit level with the ground at the evaluation point.** The seepage beneath the
+ layer exits at the daylight reference elevation, which sets the driving head; the net head across the layer is measured against the water
+ standing on the layer at the toe or berm toe. A pool below the exit level drives no seepage and fills the sand to pool level (see
+ [Hydraulic Loading and Seepage Paths](./05-hydraulic-loading-and-seepage-paths.mdx#head-beneath-the-confining-layer)).
+ - *Engineering basis:* Blanket theory for the head remaining beneath the layer, with hydrostatic
+ conditions where no seepage flows. Two-dimensional steady-state seepage models of representative sections, with 10 ft of foundation sand,
+ reproduced the resulting net head at the toe to within about 0.25 ft across configurations with the daylight ground above, at, and below
+ the toe.
+ - *Effect on results:* A daylight ground above the toe adds the difference between the two ground surfaces to the uplift at the toe, so
+ pools between the toe and the daylight ground load the layer even though they drive no seepage; a daylight ground below the toe reduces
+ the uplift.
+ - *When it may not hold:* Ground that rises or falls steeply between the toe and the daylighting exit. Blanket theory measures the downstream
+ path horizontally and holds the sand thickness constant, while a steep rise lengthens and thins the sand path beneath the layer and leaves
+ more head at the toe: for a 57 ft rise over a 50 ft downstream extent, a two-dimensional model gave about 3 ft more net head at the toe at
+ full pool. Thick foundation sand exposed beyond the layer termination adds an exit loss of similar size that the method does not include.
+18. **The toe exit type follows the presence answer.** The toe exit is hole-type only for a confirmed layer whose exit stays beneath it; for a
+ layer of unknown presence it is plane-type (see [Delegated Methods](./07-delegated-methods.mdx)).
+ - *Engineering basis:* Basis requested — see marker IN-21 below.
+ - *Effect on results:* A plane-type exit takes no exit-geometry reduction, so the toe progression probability under unknown presence is
+ lower than it would be with a hole-type exit through a possibly present layer (less conservative).
+ - *When it may not hold:* Sites where a confining layer is in fact present, so that toe seepage would emerge through defects as concentrated
+ exits.
+
+:::warning[INPUT NEEDED IN-21 — Engineering Basis]
+Assumption 18: under a layer of unknown presence, the toe exit is treated as plane-type ($C_{3d} = 1.0$), which is less conservative than the
+hole-type treatment ($C_{3d} = 0.5$) applied to a confirmed layer. Provide the engineering basis or judgment attribution for this choice, or
+confirm whether a possibly present layer should take the hole-type factor.
+:::
+
+## Flaw
+
+16. **The flaw probability is independent of pool level.**
+ - *Engineering basis:* Definitional: the flaw is a geologic condition whose existence does not depend on the pool.
+ - *Effect on results:* The same flaw probability scales the SRP at every pool level.
+ - *When it may not hold:* Pool-dependent flaw mechanisms (for example, first-filling collapse features) are outside the model.
+
+## Interpretation Cautions
+
+Three aspects of the screening formulation deserve particular attention when reading results:
+
+- **Unknown-driven breadth.** The Unknown selections (layer presence, thickness, extent) intentionally substitute wide characterizations. A
+ high screening SRP at a site with many Unknown answers reflects that breadth as much as the site physics; resolving the unknowns with field
+ information and re-running the analysis is the intended response.
+
+- **Defect floor for thin layers.** Because the defect probability does not depend on pool level and the toe unfiltered-exit probability can
+ never fall below it (assumption 6), thickness bands that include thin layers keep Node 2 high even at low pools. Where that floor exceeds the
+ blowout probability, the pool dependence of the toe SRP comes from the initiation and progression nodes instead.
+
+- **No driving head below the exit reference.** Pools at or below the toe reference elevation carry zero SRP on the toe pathway, and pools
+ at or below the daylight exit level carry zero SRP on the daylight pathway. A daylight ground above the toe does not shield the toe below
+ it: pools between the two elevations load the confining layer statically, so the toe blowout and heave probabilities can be high there
+ even though no seepage leaves the daylighting exit. The reference elevations — and the daylight ground surface in particular — directly
+ position the low-pool end of the system response curve.
+
+
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/09-output-and-interpretation.mdx b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/09-output-and-interpretation.mdx
new file mode 100644
index 000000000..1cd05e745
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/09-output-and-interpretation.mdx
@@ -0,0 +1,171 @@
+---
+title: Output and Interpretation
+---
+
+import NavContainer from '@site/src/components/NavContainer';
+
+
+
+# Output and Interpretation
+
+The model produces two groups of results: probabilities that do not depend on pool level, and series evaluated at each pool level. The
+governing SRP series is the system response curve.
+
+## Pool-Independent Results
+
+- **Flaw probability** — the mean posterior probability of a continuous foundation flaw (Node 1), from the Bayesian assessment in
+ [Flaw Assessment](./04-flaw-assessment.mdx).
+- **Flaw probability spread** — the 5th, 25th, 50th, 75th, and 95th percentiles of the posterior flaw probability, which show how sharply the
+ evidence constrains the flaw judgment.
+- **Defect probability** — the mean probability that a pre-existing defect fully penetrates the confining layer; produced only when a confining
+ layer may be present.
+- **Roof-support probability** — the probability that the material over the developing pipe sustains a roof (Node 4): 1.0 with a confirmed
+ confining layer, otherwise the minimum across the listed embankment materials.
+- **Intervention and breach probabilities** — the user-specified probabilities for Nodes 6 and 7.
+
+## Pool-Dependent Series
+
+Every pool-dependent result is a series over the evaluated pool levels: every supplied headwater value and additional pool levels distributed
+between them (see [Input Parameters](./03-input-parameters.mdx)). The daylight-pathway series
+are produced only when a confining layer may be present (its presence is Yes or Unknown) *and* the daylighting exit is distinct from the toe
+exit. When the berm toe is itself the daylighting exit — a berm that reaches or clears a confirmed layer's downstream extent, overlies a
+confirmed layer of unknown extent, or overlies a layer of unknown presence — there are no daylight series and the toe series carry the
+governing curve (see [Event Tree](./06-event-tree.mdx)).
+
+**Hydraulic series:**
+
+- **Pool levels** — the headwater elevations at which the event tree is evaluated.
+- **Tailwater** — the tailwater at each pool level, interpolated between the supplied pairs, and blank wherever no tailwater exists.
+- **Toe control level** — the higher of the tailwater and the toe reference elevation: the downstream control level of the toe progression
+ pathway, and the water standing on the confining layer in the blowout and heave analyses.
+- **Daylight control level** — the higher of the tailwater and the daylight reference elevation: the exit level that sets the driving head of
+ the blowout, heave, and daylight-progression analyses.
+
+**Toe pathway series:**
+
+- **Unfiltered-exit probability** — Node 2: the defect–blowout composition with its overrides applied; 1.0 at every pool when no confining layer
+ is present.
+- **Blowout probability** — the blowout probability alone, before it is combined with the defect probability, so the two contributions to
+ Node 2 can be compared; produced only when a confining layer may be present.
+- **Initiation probability** — Node 3: the heave probability with the berm and trigger-elevation overrides applied; 1.0 at every pool when no
+ confining layer is present.
+- **Progression probability** — Node 5: the mean probability of advancement over the toe path, non-decreasing with pool level.
+- **SRP** — the product of the seven nodes on the toe pathway.
+
+**Daylight pathway series:**
+
+- **Unfiltered-exit probability** — Node 2: 1.0 at every pool level.
+- **Initiation probability** — Node 3: 1.0 at pool levels above the daylight control level, and 0 at or below it.
+- **Progression probability** — Node 5: the mean probability of advancement over the longer daylight path, non-decreasing with pool level.
+- **SRP** — the product of the seven nodes on the daylight pathway.
+
+**Governing series:**
+
+- **Governing SRP** — the system response curve: the larger of the toe and daylight SRP at each pool level, equal to the toe SRP when no
+ daylight pathway is evaluated.
+
+## Interpreting the System Response Curve
+
+The governing SRP series is the system response curve — the conditional probability of breach by backward erosion piping as a function of pool
+level. While the net head does not decrease as the pool rises, the curve is non-decreasing with pool level: the flaw, roof-support,
+intervention, and breach nodes are constant; the blowout and heave probabilities rise with net head; and the progression node is explicitly
+constrained to be non-decreasing. Where the tailwater rises faster than the headwater, the net head can fall and the blowout and heave
+probabilities with it. Each pathway carries zero SRP at pools at or below its own control level, because its progression analysis has no
+driving head there.
+
+### Which Pathway Governs
+
+The governing curve is the larger of the two pathway SRPs at each pool level, and the two pathways differ in opposite directions:
+
+- The **toe pathway** carries unfiltered-exit and initiation probabilities that can be below one, because the confining layer resists both. Its
+ progression analysis runs over a path no longer than the daylight path — shorter with no berm, or with a berm inside a confirmed layer's
+ known extent — which raises the average applied gradient, and, when the layer is confirmed and the exit stays beneath it, uses the hole-type
+ exit that halves the Schmertmann critical gradient.
+- The **daylight pathway** carries certain unfiltered exit, because nothing confines the exit there, and certain initiation whenever seepage
+ leaves the sand there. Its progression analysis runs over the path to the layer's termination with a plane-type exit.
+
+The daylight pathway governs at a pool level when the reduction the confining layer gives the toe pathway through Nodes 2 and 3 outweighs any
+progression advantage the toe pathway gains from its shorter path and exit type; otherwise the toe pathway governs. (The path-length and depth
+corrections of the Schmertmann method also change with path length, so the progression comparison itself depends on the site.) Which side of that balance a site falls on depends on the
+layer thickness band, the unit weights, the downstream extent, and the foundation sand properties, and it can change with pool level. When both
+pathways are evaluated, both are produced, so the balance can be read directly from the results. When the berm toe is itself the daylighting
+exit, only the toe pathway is evaluated: it *is* the daylighting exit, with certain unfiltered-exit and initiation probabilities over the
+berm-extended progression path.
+
+### How Key Inputs Affect the SRP
+
+The effect of each input depends on the site configuration. The following describes the mechanism by which each key input changes the SRP and
+the conditions under which it controls the result:
+
+- **Flaw evidence selections** — the flaw probability multiplies the SRP at every pool level, so the effect of the geologic environment, the
+ strength of evidence, and the observed-seepage selections on the flaw likelihood scales the whole curve by the same factor, whatever the other
+ inputs. A sand-boil or concentrated-seepage observation also enables the seepage-through-layer and trigger-elevation inputs, which can set
+ Nodes 2 and 3 to certainty and so change the curve beyond that factor (see [Event Tree](./06-event-tree.mdx)).
+- **Confining-layer thickness category** — thickness enters the defect probability (pool-independent, and rising steeply as the layer thins)
+ and the vertical exit gradient in the blowout and heave analyses (a thinner layer gives a larger gradient for the same head). It affects the
+ toe pathway only, and only where a confining layer may be present. Where no layer is present, or where a berm daylights the exit, Nodes 2
+ and 3 are certain and thickness has no effect.
+- **Downstream confining-layer extent** — with no berm, a longer downstream path $L_3$ leaves a larger share of the net head at the toe
+ (raising the toe blowout and heave probabilities) and lengthens the daylight progression path (lowering the daylight progression
+ probability). With a berm ending inside a confirmed layer's known extent, the blowout and heave are evaluated at the berm toe, where the
+ head from flow is the driving head times the layer length remaining beyond the berm divided by the total path length, so a longer extent
+ raises them. When no berm is
+ present and the extent or the layer's presence is unknown, the 1 to 5 embankment-height default spreads these effects across a wide range.
+ With a berm, the extent also decides which exit treatment applies (see [Event Tree](./06-event-tree.mdx)).
+- **Relative density category** — denser sand raises the Schmertmann critical gradient through the density correction and lowers the
+ progression probability on both pathways. It has little effect at pool levels where the progression probability is already close to 0 or 1.
+- **Coefficient of uniformity, effective grain size, and fines content** — these set the base critical gradient, the grain-size correction,
+ and the fines-content correction of the Schmertmann analysis, and they act on Node 5 of both pathways in the same way as relative density.
+- **Embankment materials** — when the confining layer is not confirmed, the minimum roof-support probability multiplies the SRP at every pool
+ level, so a single listed material with a low roof-support probability lowers the whole curve by that factor. With a confirmed layer, the
+ materials have no effect.
+- **Reference elevations** — the toe and daylight ground surfaces set the pool levels below which each pathway has no driving head, and so
+ position the low-pool end of the curve. Their difference also enters the blowout and heave analyses directly: a daylight ground above the toe
+ adds that difference to the uplift at the toe, including at pools below the daylight ground, and a daylight ground below the toe reduces it.
+
+### Checking the Result
+
+The documented method implies several relationships that every result must satisfy. A result that breaks one of the identities below
+indicates a computation error in the model, not a property of the site:
+
+- **Product of nodes** — at each pool level, each pathway SRP equals the product of its seven node probabilities, all of which are reported.
+- **Governing value** — the governing SRP equals the larger of the toe and daylight SRP at each pool level, or the toe SRP when no daylight
+ pathway is evaluated.
+- **Upper bound** — no SRP exceeds the product of the pool-independent nodes: the flaw, roof-support, unsuccessful-intervention, and breach
+ probabilities.
+- **Unfiltered-exit floor** — on the toe pathway, the unfiltered-exit probability is never less than either the defect probability or the
+ blowout probability.
+- **Certain nodes** — on the daylight pathway, the unfiltered-exit probability is 1.0 at every pool level and the initiation probability is
+ 1.0 above the daylight control level and 0 at or below it; on the toe pathway both are 1.0 at every pool level when the confining-layer
+ presence is No.
+- **Zero-head threshold** — each pathway's SRP is zero at pool levels where its progression analysis has no net head: at or below the higher
+ of the tailwater and the toe reference elevation for the toe pathway, and of the tailwater and the daylight reference elevation for the
+ daylight pathway.
+- **Monotonic progression** — the progression probabilities never decrease with pool level.
+- **Trigger elevation** — where a trigger elevation is supplied, the toe initiation probability is 1.0 at every pool level at or above it.
+
+Two further checks follow from the method and help judge whether a result is reasonable for the site:
+
+- **Flaw ceiling** — the governing SRP never exceeds the flaw probability, so a curve that approaches the flaw probability at high pools means
+ every other node is close to certain there; the analyst can confirm that this matches the site's confining layer, materials, and berm.
+- **Low-pool unfiltered exit** — for a confirmed layer with no berm, the blowout probability falls toward zero as the net head falls, so at low
+ pools the toe unfiltered-exit probability should approach the defect probability; a much larger value at low pools points to a forcing
+ condition (for example, observed seepage through the layer) that the analyst can confirm.
+
+### Screening Versus Detailed Analysis
+
+A high screening SRP does not by itself indicate a high risk of failure — it indicates that the structure warrants analysis with the full
+toolbox models, where:
+
+- the blanket-theory case matching the actual stratigraphy can be selected from all eight configurations (see the
+ [General Overview](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-initiation/v1.0/general-overview) of the BEP Initiation manual);
+- site-specific blanket geometry replaces the screening defaults and unknown-value ranges;
+- the anisotropy and underlayer corrections (see
+ [Field Horizontal Critical Gradient](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#field-horizontal-critical-gradient)) and the pipe-inclination correction (see
+ [Pipe Path Inclination](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/schmertmann#pipe-path-inclination)) can be applied to the Schmertmann analysis;
+- the Sellmeijer method is available as an alternative progression formulation (see
+ [Sellmeijer](/docs/toolbox-technical-manuals/internal-erosion-suite/backward-erosion-piping-progression/v1.0/sellmeijer)); and
+- the flaw judgment can be refined by targeted subsurface investigation rather than screening-level evidence categories.
+
+A low screening SRP provides reasonable confidence that backward erosion piping is not a critical concern at the screening level, subject to
+the assumptions and limitations documented in this reference.
diff --git a/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/_input-needed.md b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/_input-needed.md
new file mode 100644
index 000000000..9c8761a57
--- /dev/null
+++ b/docs/web-applications/system-response/backward-erosion-piping-screening/v1.0/_input-needed.md
@@ -0,0 +1,265 @@
+# Input Needed — Backward Erosion Piping Screening Technical Reference Manual (v1.0)
+
+Answer inline and return this file (or paste its contents into the conversation). Leave an
+Answer blank to keep that marker in place. Do not renumber — the IDs tie each entry to its
+admonition in the document. IN-18 to IN-21 were added in the October 2026 revision. (IN-17 was retired in the August 2026 update: the mean-of-
+distribution treatment it questioned no longer exists — supplied seepage-path lengths are now
+single values by design. IN-12 was retired in the October 2026 model update: blowout and heave beneath a berm
+are now evaluated at the berm toe, the location the marker asked to confirm. IN-20 was retired in the same update: the
+blowout and heave net head now combines the daylight exit level with the ground at the evaluation point.)
+
+---
+
+## IN-01 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** The thickness ranges assigned to the qualitative confining-layer categories
+(Very Thin 0–5 ft, Thin 5–10 ft, Moderate 10–20 ft, Thick 20–35 ft, Unknown 0–10 ft, each as
+a uniform distribution).
+
+**Needed:** Literature citation (full bibliographic details for the bibliography) or the
+engineering-judgment attribution to state, including the reasoning for the Unknown band
+spanning 0–10 ft.
+
+**Answer:**
+
+---
+
+## IN-02 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** Default coefficient-of-uniformity distribution for the foundation sand
+(triangular: low 1.1, mode 2.0, high 4.0).
+
+**Needed:** Literature citation or engineering-judgment attribution.
+
+**Proposed (unconfirmed):** Representative of the poorly graded, uniform fine to medium sands
+susceptible to backward erosion piping.
+
+**Answer:**
+
+---
+
+## IN-03 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** Default effective-grain-size (D10) distribution for the foundation sand
+(normal: mean 0.25 mm, standard deviation 0.085 mm, values limited to no less than 0.1 mm).
+
+**Needed:** Literature citation or engineering-judgment attribution for both the distribution
+parameters and the 0.1 mm lower limit.
+
+**Answer:**
+
+---
+
+## IN-04 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** The relative-density category uniform ranges (Very Loose 0–15%, Loose 15–35%,
+Medium Dense 35–65%, Dense 65–85%, Very Dense 85–100%, and the Unknown band 15–65%).
+
+**Needed:** Literature citation or engineering-judgment attribution for the band boundaries
+and for the Unknown selection.
+
+**Proposed (unconfirmed):** Boundaries follow the standard qualitative relative-density
+classification for granular soils; a uniform distribution over each band takes no position on
+a most-likely value within the category; Unknown spans loose to medium-dense as a
+conservative screening posture. If confirmed, supply the classification source for the
+bibliography.
+
+**Answer:**
+
+---
+
+## IN-05 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** Default foundation-sand saturated unit weight (normal: mean 122.0 pcf,
+standard deviation 3.0 pcf).
+
+**Needed:** Literature citation or engineering-judgment attribution.
+
+**Proposed (unconfirmed):** Typical of loose to medium-dense saturated alluvial sand.
+
+**Answer:**
+
+---
+
+## IN-06 — Engineering Basis — `03-input-parameters.mdx`
+
+**Regarding:** Default confining-layer saturated unit weight (normal: mean 118.0 pcf,
+standard deviation 3.0 pcf).
+
+**Needed:** Literature citation or engineering-judgment attribution.
+
+**Answer:**
+
+---
+
+## IN-07 — Engineering Basis — `04-flaw-assessment.mdx`
+
+**Regarding:** The prior probability ranges by geologic depositional environment (glacial
+outwash 0.500–0.900; high-energy fluvial 0.100–0.500; coastal shoreface/barrier 0.100–0.500;
+aeolian dune 0.075–0.500; delta deposits 0.050–0.500; alluvial fans 0.050–0.300; shallow
+marine shelf 0.050–0.300; low-energy deltaic/coastal mud 0.010–0.050; residual soils
+0.001–0.100; unknown 0.050–0.300).
+
+**Needed:** Literature citation or engineering-judgment attribution — including whether the
+ranges derive from a published compilation of depositional-environment characteristics or
+from elicited expert judgment.
+
+**Answer:**
+
+---
+
+## IN-08 — Engineering Basis — `04-flaw-assessment.mdx`
+
+**Regarding:** The strength-of-evidence likelihood-ratio ranges (very strong 10–30; strong
+3–10; moderate 1–3; neutral 1; weak 0.10–0.30; very weak 0.01–0.10) and the subsurface
+data-quality factor ranges (high 1.00; moderate 0.75–0.90; low 0.50–0.75).
+
+**Needed:** Literature citation or engineering-judgment attribution, including the reasoning
+behind the order-of-magnitude likelihood bands and the quality discounts.
+
+**Answer:**
+
+---
+
+## IN-09 — Engineering Basis — `04-flaw-assessment.mdx`
+
+**Regarding:** The seepage-observation likelihood-ratio ranges (sand boils 3.50–5.00;
+concentrated seepage 2.00–3.50; stage-dependent wet areas 1.25–2.00; stage-independent wet
+areas 1.00–1.25).
+
+**Needed:** Literature citation or engineering-judgment attribution.
+
+**Answer:**
+
+---
+
+## IN-10 — Engineering Basis — `05-hydraulic-loading-and-seepage-paths.mdx`
+
+**Regarding:** Two judgments in the upstream seepage-path crediting rules: (1) a confirmed
+Very Thin confining layer contributes no upstream path length (L1 = 0), taking precedence
+over the impervious-extension credit; (2) only a layer characterized as Impervious is
+credited — Semi-pervious and Unknown permeability contribute nothing.
+
+**Needed:** Citation or engineering-judgment attribution for each judgment.
+
+**Proposed (unconfirmed):** For (1): a layer thinner than about 5 ft cannot be relied on to
+remain intact and carry head loss over its upstream extent.
+
+**Answer:**
+
+---
+
+## IN-11 — Engineering Basis — `05-hydraulic-loading-and-seepage-paths.mdx`
+
+**Regarding:** The default downstream seepage path length when the confining-layer extent (or
+presence) is unknown: uniform between 1 and 5 embankment heights.
+
+**Needed:** Literature citation or engineering-judgment attribution, including the reasoning
+for scaling the range to embankment height.
+
+**Answer:**
+
+---
+
+## IN-13 — Engineering Basis — `06-event-tree.mdx`
+
+**Regarding:** The Weibull defect-survival parameters — characteristic defect penetration
+depth 3.5 ft and shape parameter 1.25 — in the probability that a pre-existing defect fully
+penetrates the confining layer.
+
+**Needed:** The data source, calibration rationale, or engineering-judgment attribution.
+These are recorded as empirical values with no published-literature provenance.
+
+**Answer:**
+
+---
+
+## IN-14 — Engineering Basis — `06-event-tree.mdx`
+
+**Regarding:** Two judgments in the revised berm treatment (updated August 2026 — the former
+rule that any berm forces the unfiltered exit to certainty no longer exists; the treatment
+now follows where the berm ends relative to the confining layer):
+
+1. No berm is ever credited with filtering the exit — where the berm end remains beneath the
+ layer, the exit resistance is carried entirely by the layer's defect/blowout composition
+ (evaluated at the offset exit point), and where the berm daylights the exit, the
+ unfiltered exit is certain.
+2. When the layer's presence is unknown and a berm is present, a daylighting exit at the
+ berm toe is assumed (forcing the unfiltered exit to certainty) rather than evaluated.
+
+**Needed:** The engineering basis or judgment attribution for each.
+
+**Proposed (unconfirmed):** For (1): seepage and stability berms are not engineered filters,
+so no filtering credit is taken for any berm. For (2): with the layer itself unverified, its
+lateral extent beneath the berm cannot be relied upon, and assuming a daylighting exit at the
+berm toe is the conservative screening posture.
+
+**Answer:**
+
+---
+
+## IN-15 — Engineering Basis — `06-event-tree.mdx`
+
+**Regarding:** Treating the defect and blowout mechanisms as statistically independent
+pathways in the unfiltered-exit union formula.
+
+**Needed:** Engineering basis or judgment attribution for the independence treatment.
+
+**Answer:**
+
+---
+
+## IN-16 — Engineering Basis — `07-delegated-methods.mdx`
+
+**Regarding:** The fines-content correction applied in the Schmertmann analysis — a step from
+1.0 to 1.4, with the higher factor applying at exactly 5% fines and above. The same step
+applies in the toolbox Schmertmann analysis; the Schmertmann chapter of the BEP Progression
+manual does not describe the term.
+
+**Needed:** Source or engineering-judgment attribution for the step form, the 5% threshold,
+and the 1.4 value, and an addition to the Schmertmann chapter of the BEP Progression manual.
+
+**Answer:**
+
+---
+
+## IN-18 — Bibliography — `04-flaw-assessment.mdx`
+
+**Regarding:** The Bayesian formulation of the flaw assessment: each evidence source expressed
+as a likelihood ratio, the prior updated in log-odds form, and the subsurface likelihood ratio
+weighted by the data-quality factor as an exponent. The same formulation is named in the
+Physics Basis section of `02-model-overview.mdx`.
+
+**Needed:** Full bibliographic details for the source of the formulation (for the
+bibliography), or the engineering-judgment attribution for the quality-factor weighting if it
+is specific to this model.
+
+**Answer:**
+
+---
+
+## IN-19 — Engineering Basis — `08-assumptions-and-limitations.mdx`
+
+**Regarding:** Assumption 11 (horizontal pipe path): the statements that the neglected
+inclination effect is small at shallow angles and becomes significant beyond about 10° from
+horizontal.
+
+**Needed:** Literature source with full bibliographic details, or the engineering-judgment
+attribution; confirm or replace the 10° threshold.
+
+**Answer:**
+
+---
+
+## IN-21 — Engineering Basis — `08-assumptions-and-limitations.mdx`
+
+**Regarding:** Assumption 18. Under a confining layer of unknown presence, the toe exit is
+treated as plane-type (exit-geometry factor 1.0), which is less conservative than the
+hole-type factor (0.5) applied to a confirmed layer whose exit stays beneath it.
+
+**Needed:** Engineering basis or judgment attribution for this choice, or confirmation of
+whether a possibly present layer should take the hole-type factor.
+
+**Answer:**
+
+---
diff --git a/src/docConfig.js b/src/docConfig.js
index 94aa4cf81..a7d909aae 100644
--- a/src/docConfig.js
+++ b/src/docConfig.js
@@ -329,7 +329,7 @@ const docs = [
software: 'system-response',
doc_location: 'web-applications/system-response/backward-erosion-piping-screening',
doc_name: 'Backward Erosion Piping Screening Technical Reference Manual',
- active: false,
+ active: true,
draft: true,
},
{
diff --git a/static/bibliographies/web-applications/system-response/backward-erosion-piping-screening/v1.0/bib.json b/static/bibliographies/web-applications/system-response/backward-erosion-piping-screening/v1.0/bib.json
new file mode 100644
index 000000000..776c10912
--- /dev/null
+++ b/static/bibliographies/web-applications/system-response/backward-erosion-piping-screening/v1.0/bib.json
@@ -0,0 +1,50 @@
+[
+ {
+ "citationKey": "Fell2024",
+ "entryType": "report",
+ "author": [
+ "R. Fell",
+ "M.A. Foster",
+ "J. Cyganiewicz",
+ "R.R. Davidson",
+ "G.L. Sills"
+ ],
+ "title": "Methods for Estimating Probability of Failure of Embankment Dams by Internal Erosion and Piping (The Piping Toolbox 2024)",
+ "year": 2024,
+ "institution": "University of New South Wales, School of Civil and Environmental Engineering",
+ "report": "Report No. 470"
+ },
+ {
+ "citationKey": "Schmertmann2000",
+ "entryType": "incollection",
+ "author": ["J.H. Schmertmann"],
+ "year": 2000,
+ "title": "The no-filter factor of safety against piping through sands",
+ "booktitle": "Judgment and Innovation: The Heritage and Future of the Geotechnical Engineering Profession (Geotechnical Special Publication No. 111)",
+ "publisher": "American Society of Civil Engineers",
+ "pages": "65–132",
+ "doi": "10.1061/9780784405376.006"
+ },
+ {
+ "citationKey": "vanBeek2015",
+ "entryType": "article",
+ "author": ["V.M. van Beek", "H.M. Van Essen", "K. Vandenboer", "A. Bezuijen"],
+ "year": 2015,
+ "title": "Developments in modelling of backward erosion piping",
+ "journal": "Géotechnique",
+ "volume": "65",
+ "edition": "9th",
+ "pages": "740–754",
+ "doi": "10.1680/geot.14.P.119"
+ },
+ {
+ "citationKey": "USACE1956",
+ "entryType": "report",
+ "author": ["U.S. Army Corps of Engineers"],
+ "year": 1956,
+ "title": "Investigation of underseepage and its control: Lower Mississippi River Levees (Technical Manual [TM] 3-424)",
+ "institution": "U.S. Army Corps of Engineers, Waterways Experiment Station",
+ "number": "TM 3-424",
+ "url": "https://usace.contentdm.oclc.org/digital/collection/p266001coll1/id/2416/"
+ }
+]