Cleanliness National Indicator (NI 195)


Detritus Grading

9.1

Introduction
9.1.1 There is no statutory definition of detritus, however, local authority cleansing officers and their contractors have developed a common understanding of the term and the definition used for the NI 195 (and for the LEQSE) is based on this industry norm.
9.1.2 Detritus comprises dust, mud, soil, grit, gravel, stones, rotted leaf and vegetable residues, and fragments of twigs, glass, plastic and other finely divided materials. Detritus includes leaf and blossom falls when they have substantially lost their structure and have become mushy or fragmented. A significant and avoidable source of detritus is uncollected grass cuttings.
9.1.3 Detritus on metalled highways must be removed as a requirement of S.89 of the Environmental Protection Act 1990, which imposes a duty to keep highways and roads clean, and the Code of Practice on Litter and Refuse (COPL&R) recommends that detritus should be removed alongside litter and refuse by duty bodies from all other hard surfaces.
9.1.4 Detritus will be assessed separately from litter, using a grading system based on that for litter set out in the Code Of Practice On Litter And Refuse, issued under Part IV of the Environmental Protection Act 1990.
9.1.5 There will be a few occasions when transects on soil, grass or granular surfaces will be surveyed – usually as part of Recreation Areas (e.g. playing fields, riverbanks, canal towpaths, grass or dirt footpaths). In these cases it will not be possible to give a grade for detritus and so the ‘Not Appicable’ option should be circled on the NI 195 survey form. At the end of the year, when 900 transects have been surveyed, there should be 900 grades for litter but slightly fewer grades for detritus.

9.2

Definitions of Detritus Grades
  GRADE A - no detritus present on the transect;
  GRADE B - predominantly free of detritus except for some light scattering;
  GRADE C - widespread distribution of detritus, with minor accumulations;
  GRADE D - extensively covered with detritus with significant accumulations.

9.3

Assigning Intermediate Grades
9.3.1 Three Intermediate Grades will also be used (B+, between Grade A and Grade B; B –, between Grade B and Grade C; and C –, between Grade C and Grade D).
9.3.2 The intermediate grades are not separately defined – they fall ‘in between’ the four grades defined in COPL&R, when the quality standard on a transect neither conforms to the definition of an upper ‘whole’ grade nor that of the ‘whole’ grade below it.
9.3.3 This could happen where some parts of a transect could be graded as Grade B, but other parts are Grade C – e.g., there is a light scattering of detritus over much of the transect, but also one or two minor accumulations.
9.3.4 The clearest example would be where there is a marked difference in standard between one side of a transect and the other. For example, if one side is Grade B and the other is Grade C, then a Grade B – is assigned.
9.3.5 The B – Grade is particularly important in the context of the NI 195 survey, because it shows that standards are close to being satisfactory. That is why, from 1st April 2008 onwards, it will be given only half the weight of Grades C, C – and D in calculating an authority’s NI 195 score for detritus.

9.4

Why Does The NI 195 Survey Include Detritus On Rural Roads?
9.4.1 Most authorities contain Rural Roads. Only authorities in highly urbanised areas such as in Inner London, or where the boundary is drawn very tightly around the built up area, will not have sufficient ‘Rural Road’ transects to include them in the NI 195 survey.
9.4.2 If Rural Roads were omitted from the NI 195 survey, this would mean that conditions on a significant part of the land area of England would be ignored.
9.4.3 Because of the way the NI 195 survey is structured, with a target number of 30 transects for each land use in each four-monthly survey, there is no question of authorities with large rural areas being penalised.
9.4.4 Rural Roads form only 10% of the standard survey, and so the influence of conditions in any one land use on the overall NI 195 result is limited.
9.4.5 Equal weight is given to Rural Roads for every authority in which they form enough transects to be included in the NI 195 survey. Levels of detritus tend to be relatively high on Rural Roads, both in ‘urban’ and ‘rural’ authorities (see Section 15.0 for the latest estimated national benchmarks).
9.4.6 The fact that detritus is measured on all transects surveyed for NI 195 helps to ensure that the NI 195 survey is consistent and comparable between all local authorities.

9.5

Grading Detritus On Rural Roads
9.5.1 On Rural Roads, where there is a kerb, detritus should be assessed in the normal way.
9.5.2 Often, however, there is no kerb, and the edge of the carriageway may be eroded and difficult to identify. There are three common variations;
a. there is a clearly defined margin to the metalled surface* of the road, with a bank covered by grass or vegetation;
b. there is a broken and irregular edge to the metalled surface* of the road;
c. an area adjacent to the road surface that is covered by grass and/or vegetation has been overrun by vehicles, spreading mud over the metalled surface* of the road.
  *Note: a metalled surface is one that is made of broken stone that is mixed with asphalt to form tarmac.
9.5.3 In this situation, surveyors should base their grading assessment on the detritus lying on the metalled surface of the road.

9.6

How To Deal With Rock Salt
9.6.1 During cold snaps and frosts, road salt deliberately placed on roads and footways for safety purposes should not be considered as detritus. However, if it appears that road salt has not been swept away for a long period after the cold weather, and has denatured, then surveyors should grade it as if it were detritus.
9.6.2 This is consistent with the approach taken to leaf and blossom fall.


Last modified: 18 June 2009
Last published: 11 May 2009

Department for Environment, Food and Rural Affairs