Allocation Assessment • tbeploads

library(tbeploads)

The anlz_aa() function compares mean annual total nitrogen (TN) loads against the allowable allocations established by the Tampa Bay Nitrogen Management Consortium (TBNMC) as part of the 5-year Reasonable Assurance (RA) assessment. Allocations are defined for four source categories: non-point source / MS4 stormwater (NPS), industrial point source (IPS), domestic point source (DPS), and material losses (ML). Each category uses a different method for computing mean loads and, where applicable, applies hydrologic normalization.

Required inputs

anlz_aa() takes six arguments: the year range, pre-computed load data for each source, and the tbbase spatial lookup table:

anlz_aa(yrrng, dps_data, ips_data, ml_data, nps_data, tbbase)

yrrng is an integer vector of length 2 giving the first and last years of the assessment period. The function internally expands this to a full sequence using seq(min, max). For example, assessing 2022 to 2024:

yrrng <- c(2022, 2024)

The four load inputs are computed using the corresponding anlz_* functions described in the individual loading vignettes. Each is briefly described below.

DPS loads

DPS loads come from anlz_dps_facility(). The function requires a vector of file paths to entity data files provided by TBNMC partners. See the DPS vignette for full details on the required file format and processing steps.

fls_dps <- list.files(system.file("extdata/", package = "tbeploads"),
  pattern = "ps_dom_", full.names = TRUE)
dps <- anlz_dps_facility(fls_dps)
head(dps)

IPS loads

IPS loads come from anlz_ips_facility(). The function requires a vector of file paths to industrial facility discharge files. See the IPS vignette for full details.

fls_ips <- list.files(system.file("extdata/", package = "tbeploads"),
  pattern = "ps_ind_", full.names = TRUE)
ips <- anlz_ips_facility(fls_ips)
head(ips)

ML loads

Material loss loads come from anlz_ml_facility(). The function requires a vector of file paths to material loss data files. See the ML vignette for full details.

fls_ml <- list.files(system.file("extdata/", package = "tbeploads"),
  pattern = "ps_indml", full.names = TRUE)
ml <- anlz_ml_facility(fls_ml)
head(ml)

NPS loads

NPS loads come from anlz_nps() called with summ = "basin" and summtime = "year". This produces annual basin-level TN and hydrologic loads that anlz_aa() disaggregates to individual MS4 entities. See the NPS vignette for full details on the required inputs.

data(tbbase)
data(rain)
data(allwq)
data(allflo)

nps <- anlz_nps(
  yrrng    = c("2022-01-01", "2024-12-31"),
  tbbase   = tbbase,
  rain     = rain,
  allwq    = allwq,
  allflo   = allflo,
  vernafl  = system.file("extdata/verna-raw.csv", package = "tbeploads"),
  summ     = "basin",
  summtime = "year"
)
head(nps)

The NPS loads passed to anlz_aa() represent total NPS contributions and are not corrected for point-source loads upstream of stream gauges. The point-source correction handled by anlz_nps_psremove() is intentionally omitted here because the allocation assessment disaggregates loads at the basin level, which is inconsistent with that subtraction.

Running the assessment

With all inputs prepared, the assessment is run as:

data(tbbase)
result <- anlz_aa(c(2022, 2024), dps, ips, ml, nps, tbbase)
head(result)

The function returns one row per entity (NPS/MS4) or entity/facility (IPS, DPS, ML) per bay segment, with the following columns:

Column	Description
`bay_seg`	Integer bay segment (1 = OTB, 2 = HB, 3 = MTB, 4 = LTB, 55 = RALTB)
`segment`	Bay segment name
`entity`	MS4 entity name or facility operator
`entity_full`	Full entity name (NPS rows only)
`facname`	Facility name (IPS, DPS, ML rows only)
`permit`	NPDES permit number (IPS rows only)
`source`	Allocation type (`"MS4"`, `"IPS"`, `"DPS - end of pipe"`, `"DPS - reuse"`, `"ML"`)
`alloc_pct`	Fractional TN allocation (0-1)
`alloc_tons`	Allowable TN load (tons/yr)
`eff_load_tons`	Mean hydrologically-normalized TN load (tons/yr)
`load_tons`	Mean annual TN load without normalization (tons/yr)
`pass`	`TRUE` if `eff_load_tons <= alloc_tons`, `NA` when either value is missing

Entities present in the computed loads but absent from the allocation tables are retained in the output with NA allocation fields so that unmatched entries are visible for troubleshooting.

Source-specific methodology

NPS/MS4

The NPS path disaggregates basin-level loads to individual MS4 jurisdictions using land use and runoff coefficient data from tbbase. The core disaggregation uses two factors computed internally by util_aa_npsfactors():

factor_tn: each CLUCSID’s share of basin TN load, proportional to EMC, area, and runoff coefficient relative to the basin total.
factor_rc: each entity’s share of a CLUCSID’s load within a basin, proportional to entity area times runoff coefficient relative to the CLUCSID total.

Agricultural land use (category "Agriculture") is attributed to the aggregate entity "All" regardless of the underlying MS4 jurisdiction.

A conservation land correction is applied before summing across CLUCSIDs. The conserv_correction dataset provides entity- and CLUCSID-specific fractions of area times runoff coefficient attributable to conservation land. These fractions are derived from the original SAS land cover file, which includes a binary conservation land flag while retaining the original MS4 jurisdiction for each spatial unit. Each entity’s disaggregated TN load for a given basin and CLUCSID is scaled by (1 - conserv_frac) to remove the conservation land contribution. The tbbase file herein does not include a conservation land overlay because the original spatial layer is unavailable for routine GIS updates, so conserv_correction is stored as a separate stable dataset and applied as a backend correction.

After disaggregation, entity loads and 1992-1994 baseline water volumes from hydro_baseline are summed across basins to the bay segment level. Corrections from aa_corrections (representing atmospheric deposition and approved project TN adjustments from the 2007 RA analysis) are subtracted before hydrologic normalization:

$\text{eff\_tn} = (\text{tn\_entity} - \text{corr\_tons}) \times \frac{\text{mean\_h2o\_9294}}{\text{total\_h2o}}$

total_h2o is the annual NPS + IPS + DPS water load for that basin (matching the SAS ratio1_2224 denominator). mean_h2o_9294 is the 1992-1994 baseline total basin water volume from hydro_baseline. Effective loads are averaged over yrrng as sum / length(yrrng), so missing years contribute zero rather than being excluded.

Bay segments Terra Ceia Bay (6) and Manatee River (7) are merged into segment 55 (Remaining Lower Tampa Bay) after disaggregation, consistent with hydro_baseline and TBNMC reporting. Boca Ciega Bay (segment 5) is excluded from the allocation framework.

IPS

Industrial point source loads from each facility are normalized by the ratio of the 1992-1994 baseline basin water volume to the total annual basin water load:

$\text{eff\_tn} = \text{tn\_load} \times \frac{\text{mean\_h2o\_9294}}{\text{basin\_total\_h2o}}$

The normalization denominator is the same total basin water load (NPS + IPS + DPS) used in the NPS path, matching the SAS ratio1_2224 construction. Effective loads are summed across basins per permit and averaged over yrrng.

DPS

Domestic point source loads require no hydrologic normalization. Monthly loads from dps_data are summed to annual totals per facility and averaged over yrrng. Boca Ciega Bay (bay_seg = 5) is excluded and bay segments 6 and 7 are remapped to 55 before joining against dps_allocations for the Remainder Lower Tampa Bay segment. The join key is entity + facility name + bay segment + source type (end of pipe or reuse).

ML

Material loss loads require no hydrologic normalization. Monthly loads are summed to annual totals per facility and averaged over yrrng. Facilities with ishared = FALSE in ml_allocations are assessed individually against their own allocation. Facilities with ishared = TRUE (e.g., Mosaic facilities in Hillsborough Bay) have their loads summed to an entity + bay segment total before comparison to a single shared allocation.

Supporting datasets

The following package datasets support the allocation assessment and are used internally by anlz_aa():

Dataset	Description
`nps_allocations`	NPS/MS4 allowable allocations by entity and bay segment
`ps_allocations`	IPS allowable allocations by NPDES permit
`dps_allocations`	DPS allowable allocations by facility, bay segment, and source type
`ml_allocations`	ML allowable allocations by facility and bay segment
`hydro_baseline`	1992-1994 mean annual basin water volumes (million m3/yr)
`aa_corrections`	AD and approved project TN corrections per entity and bay segment
`conserv_correction`	Conservation land area fractions per entity, basin, and CLUCSID