Bomvrij militair object, Voordorpsedijk Groenekan (De Bilt 26)

English translation

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Description

Cluster 36. Group Shelters Type P.

NEW HOLLANDIC WATERLINE

Introduction

GROUP SHELTERS TYPE P as twentieth-century, mass-produced additions to the existing defence system. At various locations around Forts Voordorp and Blauwkapel there are in total more than 15 Group Shelters Type P. Most are located in the area between the two forts and some south and east of Fort Voordorp. (Concrete) (group) shelters formed a response to the arrival of heavy projectiles and high-explosive grenades. The latter have a highly explosive charge. According to the weight of the artillery and the protection against it, there is a classification into resistance or protection classes, consisting of two numbers, for example W 12-15. The first indicates that the protection is sufficient for impacts of projectiles up to that calibre (in centimetres); the second that protection also exists against one or at most a few impacts up to this higher calibre. The earliest types of concrete shelters offered only protection against grenade shrapnel and were called 'shrapnel-proof'. The Group Shelters Type P were built in the years 1939-1940 at multiple locations in the Netherlands according to more or less uniform or standard design. The total number of built examples is approximately 700, of which around 570 in the New Hollandic Waterline; the majority (approximately 400) of these still exist. The construction programme for Group Shelters Type P was not completed at the outbreak of the Second World War and a number of examples have visibly remained unfinished. Type P (also called 'the pyramid' because of its distinctive shape) is presumably the most well-known type of concrete defensive work in the Netherlands. The type originated from the so-called VIS 77 (Regulation for Preparing Positions no. 77), from 1928, and had among other things the purpose of being part of the defence of a number of new accesses, especially (motorway) roads. The Group Shelter Type P usually came into being in the direct vicinity of already existing or contemporary fortifications, gun emplacements, strengthened positions, group nests or trenches. The traditionally entirely closed front face or front side of the Group Shelters Type P was intended to be covered by earthworks, which could form part of a glacis to protect the trench or a covered way. These earthworks are now mostly no longer present or only recognisable with difficulty, but in particular on forts or in otherwise relief-marked terrain there is sometimes still coverage. There are various variants of Type P, both in terms of dimensions and protection class as well as in execution and detail. For instance, there are examples built in protection classes W 12-15 and W 21-28 with dimensions ranging from approximately 5.50 x 7.20 x 4.70 metres to 6.50 x 8.20 x 4.90 metres (width x depth x height). Numerous examples of Type P were built in inundatable areas, in which in a number of cases a visible pile foundation was applied, while often a retaining wall or trough with steps against floodwater was incorporated in the then elevated, square entrance and in yet others a protruding concrete foundation slab is present all around. The examples within the complex Concrete Works between Fort Blauwkapel and Fort Voordorp lie largely in a still recognisable with some effort linear relationship, which extends from Fort Blauwkapel in the northwest to Fort Voordorp in the southeast. Examples also lie on both forts.

Description

GROUP SHELTERS TYPE P are single-storey military shelters, usually executed in reinforced, approximately 100 to 180 centimetre thick cast concrete, grenade-proof, which could provide shelter for 10-12 infantrymen/artillerymen. Group Shelters Type P are built on a rectangular ground plan. The visible height above ground level varies. Both blind side walls and the rear face are executed vertically up to approximately 3 metres height. Above this these walls bend inward at approximately 45 degrees, and then continue into a flat roof. On the right in the rear face is at locally varying height above ground level an entrance opening (later sealed or not). The entirely vertical, closed front face reflects the 45 degree angles and thus ends as a 'truncated pointed gable'. In a number of cases iron hooks were cast into the wall(s) which could serve to attach camouflage material. A characteristic component on top of the Type P shelter is the conical, concrete 'exhaust', which was intended for application of a periscope. These periscopes were however never installed in practice. The interior of the Group Shelters Type P consists of a short corridor (usually with a concrete retaining wall or balustrade and usually a few descending steps) and from there a 'sluice' directed to the left which could be sealed off by a (consisting of several parts) heavy, steel door with bolts. Via a second, comparable door the rear space could be reached to the right, the actual shelter. The entrance could be covered from this space via a firing port. The doors were however rarely or never installed in practice. The ceilings located at approximately two metres above floor level are flat and rectangular. In a number of cases interior components are still present, such as (remains of) wooden benches or a support for the firearm for covering the entrance. The Group Shelters Type P within the complex Concrete Works between Fort Blauwkapel and Fort Voordorp lie (almost) without exception visibly and recognisably in the terrain, although not always in accessible areas. An earth covering is not (any longer) present.

Valuation

The GROUP SHELTERS TYPE P within the complex Concrete Works between Fort Blauwkapel and Fort Voordorp are of general interest because of:

* Cultural-historical values as part of the New Hollandic Waterline as designed by C.R.T. Kraijenhoff and first implemented from 1815 by him, Jan Blanken and major-engineer Willem Offerhaus and subsequently by others strengthened and improved over approximately 125 years.

* Architectural-historical values, in particular as an expression of military-strategic building technique, which is based on the system of: a. the system of inundation and access defence (twentieth century), b. the race with increasingly strengthened offensive means (twentieth century), c. the system of 'living' field fortification in depth (twentieth century).

These are components from the period 1939-1940, namely concrete enlisted men's shelters.

* Ensemble value and situational values as part of the New Hollandic Waterline in general and because of the mutual functional, functionally-spatial and physical coherence with the remaining components of the complex and Forts Voordorp and Blauwkapel, where small concrete works belonging to the same adaptation of the defence system are located.

* The components are representative (characteristic) because they are clearly recognisable as components of a deconcentrated defence line added to the existing fortification system.

* The components are reasonably well preserved and as built components can still be well recognised in the field.